Accuracy of Postcontrast 3D Turbo Spin-Echo MR Sequence for the Detection of Enhanced Inflammatory Lesions in Patients with Multiple Sclerosis

BACKGROUND AND PURPOSE:Therapeutic strategies for patients with MS partly rely on contrast-enhanced MR imaging. Our aim was to assess the diagnostic performance of 3D turbo spin-echo MR imaging with variable refocusing flip angles at 3T for the detection of enhanced inflammatory lesions in patients with multiple sclerosis.MATERIALS AND METHODS:Fifty-six patients with MS were prospectively investigated by using postcontrast T1-weighted axial 2D spin-echo and 3D TSE MR images. The order in which both sequences were performed was randomized. Axial reformats from 3D T1 TSE were generated to match the 2D spin-echo images. The reference standard was defined by using clinical data and all MR images available. Three separate sets of MR images (2D spin-echo images, axial reformats, and multiplanar images from 3D TSE sequences) were examined in a blinded fashion by 2 neuroradiologists separately for the detection of enhanced MS lesions. Image artifacts and contrast were evaluated.RESULTS:No artifacts related to vascular pulsation were observed on 3D TSE images, whereas image artifacts were demonstrated on 2D spin-echo images in 41 patients. One hundred twelve enhanced MS lesions were identified in 19 patients. Sixty-four lesions were correctly diagnosed by using 2D spin-echo images; 90, by using 3D TSE axial reformatted views; and 106, by using multiplanar analysis of the 3D TSE sequence. Multiplanar analysis was 94.7% sensitive and 100% specific for the diagnosis of patients with at least 1 enhanced lesion. Contrast of enhanced MS lesions was significantly improved by using the 3D TSE sequence (P < .011).CONCLUSIONS:The 3D TSE sequence with multiplanar analysis is a useful tool for the detection of enhanced MS lesions.

The diagnosis of multiple sclerosis needs to demonstrate dissemination of brain lesions in space and time and to exclude alternative diagnoses. In some circumstances, dissemination of brain lesions in space and time can be established by a single MR imaging.¹ In such patients, dissemination of brain lesions in time is demonstrated by the simultaneous presence of asymptomatic gadolinium-enhancing and nonenhancing lesions at any time.¹ Indeed, therapeutic strategies for patients with MS partly rely on contrast-enhanced MR imaging. Updated recommendations on the use of MR imaging in MS suggest that axial 2D T1-weighted spin-echo (SE) MR imaging should be performed for the detection of enhanced MS lesions,^2,3 whereas T1-weighted 3D gradient recalled-echo (GRE) MR images are reported to be useful for the assessment of brain atrophy.^2–4 As previously reported,⁵ the sensitivity of the 2D T1-weighted SE sequence for the detection of enhanced MS lesions is progressively increased from 5 to 10 minutes after intravenous injection of gadolinium.Recently, a new technique has been introduced to generate 3D T1-weighted images of the brain (BrainView, Philips Healthcare, Best, the Netherlands; Cube, GE Healthcare, Milwaukee, Wisconsin; SPACE, Siemens, Erlangen, Germany). The BrainView sequence is based on a turbo spin-echo acquisition with variable refocusing flip angles and short echo spacing, allowing longer echo-train readouts and reduced signal losses.⁶ Such an approach provides high spatial resolution and signal-to-noise ratio without the blurring commonly associated with long echo-trains. Thinner section images can be acquired, minimizing the partial volume effect between small lesions and surrounding brain parenchyma. The added value of the postcontrast 3D TSE sequence with variable flip angles was recently reported in patients with brain metastasis.^7,8No data are available on the diagnostic performance of the postcontrast 3D T1-weighted TSE sequence for the detection of enhanced inflammatory lesions in patients with MS. Our purpose was to assess the detectable enhanced MS lesions by using the 3D BrainView sequence compared with the conventional axial 2D SE sequence.     

A Spiral Spin-Echo MR Imaging Technique for Improved Flow Artifact Suppression in T1-Weighted Postcontrast Brain Imaging: A Comparison with Cartesian Turbo Spin-Echo

BACKGROUND AND PURPOSE:A challenge with the T1-weighted postcontrast Cartesian spin-echo and turbo spin-echo brain MR imaging is the presence of flow artifacts. Our aim was to develop a rapid 2D spiral spin-echo sequence for T1-weighted MR imaging with minimal flow artifacts and to compare it with a conventional Cartesian 2D turbo spin-echo sequence.MATERIALS AND METHODS:T1-weighted brain imaging was performed in 24 pediatric patients. After the administration of intravenous gadolinium contrast agent, a reference Cartesian TSE sequence with a scanning time of 2 minutes 30 seconds was performed, followed by the proposed spiral spin-echo sequence with a scanning time of 1 minutes 18 seconds, with similar spatial resolution and volumetric coverage. The results were reviewed independently and blindly by 3 neuroradiologists. Scores from a 3-point scale were assigned in 3 categories: flow artifact reduction, subjective preference, and lesion conspicuity, if any. The Wilcoxon signed rank test was performed to evaluate the reviewer scores. The t test was used to evaluate the SNR. The Fleiss κ coefficient was calculated to examine interreader agreement.RESULTS:In 23 cases, spiral spin-echo was scored over Cartesian TSE in flow artifact reduction (P < .001). In 21 cases, spiral spin-echo was rated superior in subjective preference (P < .001). Ten patients were identified with lesions, and no statistically significant difference in lesion conspicuity was observed between the 2 sequences. There was no statistically significant difference in SNR between the 2 techniques. The Fleiss κ coefficient was 0.79 (95% confidence interval, 0.65–0.93).CONCLUSIONS:The proposed spiral spin-echo pulse sequence provides postcontrast images with minimal flow artifacts at a faster scanning time than its Cartesian TSE counterpart.

T1-weighted MR imaging after the injection of gadolinium-based contrast agent is widely used in the diagnosis of many neurologic diseases, such as tumors, infections, and inflammatory conditions. 2D multisection Cartesian spin-echo (SE) and turbo spin-echo–based pulse sequences are the clinically preferred methods for postcontrast T1WI. A challenge with these Cartesian images is the presence of ghosting artifacts due to flowing blood from the venous sinuses. These artifacts can obscure the visualization of lesions and reduce image quality. With contrast-agent enhancement, these flow artifacts are further exacerbated by bright-blood signals. Gradient flow compensation and spatial saturation bands are helpful in alleviating, but not eliminating, these flow-induced artifacts in Cartesian acquisitions.Spiral MR imaging, a non-Cartesian acquisition technique, has several advantages over its Cartesian counterpart.^1,2 A primary benefit is the ability of the spiral to traverse k-space more efficiently per unit of time than Cartesian trajectories, thus providing a higher scan speed. With spiral acquisitions, motion- and flow-induced errors are manifest as incoherent artifacts in the image domain. As a result, spiral acquisition reduces the sensitivity of the pulse sequence to structured artifacts.³ The spiral trajectory also inherently provides zero gradient moments at the origin of k-space, which substantially decreases the sensitivity of the sequence to in-plane flow-related artifacts.⁴ Spiral SE MR imaging has been reported in pelvic imaging,⁵ black-blood imaging of peripheral vasculature,⁶ and functional MR imaging.⁷The purpose of this work was to develop a 2D spiral SE technique for T1-weighted brain imaging with minimal flow artifacts and faster scanning speed and compare it with a conventional 2D Cartesian TSE pulse sequence, with comparable spatial resolution and volumetric coverage. We prospectively evaluated the performance of the 2D spiral SE technique and its subsequent image quality in a cohort of pediatric patients.     

T1 Signal-Intensity Increase in the Dentate Nucleus after Multiple Exposures to Gadodiamide: Intraindividual Comparison between 2 Commonly Used Sequences

BACKGROUND AND PURPOSE:Different T1-weighted sequences have been used for qualitative and quantitative evaluation of T1 signal intensity related to gadolinium deposition in the dentate nucleus in patients who underwent several enhanced MR imaging studies. Our purpose was to perform an intraindividual qualitative and quantitative comparison between T1-weighted spin-echo and 3D magnetization-prepared rapid acquisition of gradient echo sequences in patients who had multiple exposures to gadodiamide.MATERIALS AND METHODS:Our retrospectively selected population included 18 patients who underwent at least 3 administrations of gadodiamide and had a baseline and a final MR imaging performed with both T1-weighted sequences. Qualitative and quantitative analyses were independently performed. Dentate nucleus/middle cerebellar peduncle signal-intensity ratios and signal changes between the baseline and final examinations were compared by using the Wilcoxon signed rank test. Correlation between quantitative and qualitative evaluations was assessed by using a polyserial correlation test.RESULTS:The differences between the 2 sequences for both baseline and last examination dentate nucleus/middle cerebellar peduncle ratios were statistically significant (P = .008 and P = .006, respectively); however, the signal-intensity changes of the ratios with time were not (P = .64). The correlation between the qualitative and quantitative analysis was very strong (near-perfect) (r = 0.9) for MPRAGE and strong (r = 0.63) for spin-echo sequences.CONCLUSIONS:T1-weighted spin-echo and MPRAGE sequences cannot be used interchangeably for qualitative or quantitative analysis of signal intensity in the dentate nucleus in patients who received gadodiamide. Baseline and final examination ratios should be evaluated across time by using the same sequence. Qualitative analysis performed with MPRAGE correlated better with quantitative analysis and may offer advantages over spin-echo sequences for research purposes.

During the past 2 years, several peer-reviewed studies have been published describing an association between progressive high signal intensity on unenhanced T1-weighted images in the globus pallidus and/or dentate nucleus (DN) and the number of administrations of different gadolinium-based contrast agents (GBCAs), suggesting gadolinium deposition in these structures; this has been confirmed in humans and animals.^1–11One major limitation of retrospective human studies of gadolinium deposition is the variability of the MR imaging protocols used, according to the pathology that is being studied and among different institutions.Kanda et al⁵ and Adin et al⁸ used qualitative measurements to evaluate signal-intensity changes in patients who underwent multiple GBCA administrations, by using T1-weighted spin-echo (SE),^5,8 T1 MPRAGE, or T1 FLAIR images.⁸ It is generally assumed that visual analysis correlates well with quantitative analysis, but qualitative assessment of the presence or absence of hyperintensity on T1-weighted MR images is subjective; hence, quantitative signal-intensity measurement is commonly favored.In most of the published literature, the authors have used T1-weighted SE sequences to quantitatively evaluate the signal intensity and signal changes with time. However, in some studies, different T1-weighted sequences have been interchangeably used, including T1-weighted 3D MPRAGE⁶ and FLASH,¹² to quantitatively evaluate signal-intensity changes in the dentate nucleus. Not surprising, the results among different investigators are somewhat contradictory. The use of different sequences may, in part, explain these differences.¹³ It is unclear whether different T1-weighted sequences may be used interchangeably to qualitatively and quantitatively study gadolinium deposition on the basis of their T1-weighting despite their distinct intrinsic properties. Even though quantitative measurements are undoubtedly recommended for scientific publications, they are difficult to apply in clinical practice. On the other hand, qualitative analysis is applied every day to assess normal brain structures and lesions. Considering the increasing concern regarding GBCA administration, we believe qualitative analysis must be evaluated. Therefore, our aim was to determine whether there are differences between the quantitative analysis performed with T1-weighted SE and T1-weighted MPRAGE sequences and to correlate the qualitative appreciation of the T1 signal intensity of the DN with the quantitative analysis of corresponding sequences.     

Optimal MR Plaque Imaging for Cervical Carotid Artery Stenosis in Predicting the Development of Microembolic Signals during Exposure of Carotid Arteries in Endarterectomy: Comparison of 4 T1-Weighted Imaging Techniques

BACKGROUND AND PURPOSE:Preoperative identification of plaque vulnerability may allow improved risk stratification for patients considered for carotid endarterectomy. The present study aimed to determine which plaque imaging technique, cardiac-gated black-blood fast spin-echo, magnetization-prepared rapid acquisition of gradient echo, source image of 3D time-of-flight MR angiography, or noncardiac-gated spin-echo, most accurately predicts development of microembolic signals during exposure of carotid arteries in carotid endarterectomy.MATERIALS AND METHODS:Eighty patients with ICA stenosis (≥70%) underwent the 4 sequences of preoperative MR plaque imaging of the affected carotid bifurcation and then carotid endarterectomy under transcranial Doppler monitoring of microembolic signals in the ipsilateral middle cerebral artery. The contrast ratio of the carotid plaque was calculated by dividing plaque signal intensity by sternocleidomastoid muscle signal intensity.RESULTS:Microembolic signals during exposure of carotid arteries were detected in 23 patients (29%), 3 of whom developed new neurologic deficits postoperatively. Those deficits remained at 24 hours after surgery in only 1 patient. The area under the receiver operating characteristic curve to discriminate between the presence and absence of microembolic signals during exposure of the carotid arteries was significantly greater with nongated spin-echo than with black-blood fast spin-echo (difference between areas, 0.258; P < .0001), MPRAGE (difference between areas, 0.106; P = .0023), or source image of 3D time-of-flight MR angiography (difference between areas, 0.128; P = .0010). Negative binomial regression showed that in the 23 patients with microembolic signals, the contrast ratio was associated with the number of microembolic signals only in nongated spin-echo (risk ratio, 1.36; 95% confidence interval, 1.01–1.97; P < .001).CONCLUSIONS:Nongated spin-echo may predict the development of microembolic signals during exposure of the carotid arteries in carotid endarterectomy more accurately than other MR plaque imaging techniques.

For appropriately selected patients, carotid endarterectomy (CEA) can effectively prevent stroke,^1–3 with few neurologic deficits observed immediately following the procedure. Surgical site embolism represents >70% of intraoperative procedure-related strokes.⁴ When one monitors the middle cerebral artery by using intraoperative transcranial Doppler (TCD), microembolic signals (MES) are detected in >90% of patients undergoing CEA^4–6; however, the quality and quantity of MES detected depends on the stage of CEA.^5–7 During exposure procedures for the carotid arteries, plaque that represents a source of emboli and has not been removed remains exposed to blood flow. Under such conditions, manipulation of the carotid arteries can dislodge emboli from the surgical site into the intracranial arteries.⁸ Furthermore, because the target vessel remains closed during the exposure procedure, detectable MES are thought to represent solid masses, such as thrombi, necrosis, or lipid.⁶ In contrast, once the walls of the carotid arteries are cut for endarterectomy, a high number of harmless gaseous MES may develop during carotid declamping due to air entering the lumen of the arteries.^6,9 Detection of MES during the exposure procedure has been shown to correlate with postoperative neurologic deficits immediately after CEA.^5–7,9–11Several investigators have compared MES during the exposure procedure for the carotid arteries in CEA with histopathologic findings of excised carotid plaque and have demonstrated that development of the MES was strongly associated with vulnerable carotid plaques consisting primarily of intraplaque hemorrhage and/or intraluminal thrombus.^12,13 Intraplaque hemorrhage might cause formation of intraluminal thrombus likely due to chemical mediators, increased stenosis, or changes in eddy currents, though the associations among these remain unclear. Other research has shown that more cerebrovascular adverse events related to CEA occurred in patients with atheromatous plaques compared with patients with fibrous plaques.⁹ Preoperative identification of plaque vulnerability may thus allow improved risk stratification for patients considered for CEA.Intraplaque characteristics are generally assessed by using MR imaging based on T1-weighted sequences,¹⁴ and the detection of intraplaque hemorrhage on preoperative MR imaging is associated with the development of MES during the procedure for exposure of the carotid arteries.¹² However, there has been inconsistency among published findings on vulnerable plaques.¹⁵ This could be due to interinstitutional differences in the methodology for such imaging techniques as cardiac-gated black-blood fast spin-echo (BB-FSE),^16–19 magnetization-prepared rapid acquisition of gradient echo,^12,20–22 source image of 3D time-of-flight MR angiography (SI-MRA),²³ and noncardiac-gated spin-echo (SE).^15,24,25 Although the cardiac-gated BB-FSE method is most commonly used for T1-weighted MR plaque imaging,^17,18 the TR is dependent on a single R-R interval from electrocardiography, which occasionally results in an overly long TR to diminish proton density–weighted contrast and to enhance T1-weighted contrast.²⁵In addition to cardiac gating, proton density–weighted contrast is preserved when using T1-weighted spoiled gradient-echo techniques, which are generally used for MRA.²³ The use of T1-weighted spoiled gradient-echo techniques on SI-MRA could result in insufficient contrast between fibrous and lipid/necrotic plaques.¹⁵ Originally developed for direct thrombus imaging, MPRAGE is a modified sequence in which the TI is set to permit black-blood effects.²¹ Because the signal intensity of the lipid/necrotic component tends to show T1 values similar to those of blood, the intensity can theoretically be attenuated.¹⁵ The substantial influence of the proton density and inversion recovery pulse can be avoided in nongated SE; however, this sequence requires a relatively long acquisition time and is known to be susceptible to patient motion even when motion correction is used.¹⁵ Among these 4 kinds of imaging techniques, substantial variation is observed in the contrast provided by T1-weighted MR plaque imaging and its ability to characterize intraplaque components. Furthermore, quantitative color-coded MR plaque imaging performed by using the nongated SE sequence has recently been shown to provide accurate evaluation of the composition (ie, fibrous tissue, lipid/necrosis, or hemorrhage) of excised carotid plaques compared with histopathologic findings in patients undergoing CEA.²⁶The purpose of the present study was thus to determine which plaque imaging technique, BB-FSE, MPRAGE, SI-MRA, or nongated SE, all of which are variations of T1-weighted imaging, can most accurately predict development of MES during exposure of the carotid arteries in CEA.     

How Common Is Signal-Intensity Increase in Optic Nerve Segments on 3D Double Inversion Recovery Sequences in Visually Asymptomatic Patients with Multiple Sclerosis?

BACKGROUND AND PURPOSE:In postmortem studies, subclinical optic nerve demyelination is very common in patients with MS but radiologic demonstration is difficult and mainly based on STIR T2WI. Our aim was to evaluate 3D double inversion recovery MR imaging for the detection of subclinical demyelinating lesions within optic nerve segments.MATERIALS AND METHODS:The signal intensities in 4 different optic nerve segments (ie, retrobulbar, canalicular, prechiasmatic, and chiasm) were evaluated on 3D double inversion recovery MR imaging in 95 patients with MS without visual symptoms within the past 3 years and in 50 patients without optic nerve pathology. We compared the signal intensities with those of the adjacent lateral rectus muscle. The evaluation was performed by a student group and an expert neuroradiologist. Statistical evaluation (the Cohen κ test) was performed.RESULTS:On the 3D double inversion recovery sequence, optic nerve segments in the comparison group were all hypointense, and an isointense nerve sheath surrounded the retrobulbar nerve segment. At least 1 optic nerve segment was isointense or hyperintense in 68 patients (72%) in the group with MS on the basis of the results of the expert neuroradiologist. Student raters were able to correctly identify optic nerve hypersignal in 97%.CONCLUSIONS:A hypersignal in at least 1 optic nerve segment on the 3D double inversion recovery sequence compared with hyposignal in optic nerve segments in the comparison group was very common in visually asymptomatic patients with MS. The signal-intensity rating of optic nerve segments could also be performed by inexperienced student readers.

MR imaging contributes to not only the diagnosis and differential diagnosis of MS but also the monitoring and follow-up of patients.¹ T1-weighted postcontrast, T2-weighted, proton-density, FLAIR, and double inversion recovery (DIR) images are recommended to detect acute and chronic demyelinating lesions in typical locations.^1–9Acute optic neuritis is an inflammatory demyelination of the optic nerve causing acute visual loss.^10–13 After recovery, patients are often visually asymptomatic, but careful visual testing by visually evoked potentials, optical coherence tomography, and visual disability evaluation may reveal persistent slight visual deficits.^14–17 These deficits are also observed in patients without any history of previous acute optic neuritis due to a suspected subclinical disease known as subclinical optic nerve demyelination.^14–17Acute optic neuritis is easily diagnosed on MR imaging by focal nerve swelling and segmental T2-weighted hyperintensity, especially on STIR images or on fat-suppressed T2-weighted images and by segmental gadolinium enhancement on T1-weighted fat-suppressed images.^10,18–22 The enhancement is present for a mean of 30 days after the onset of visual symptoms.^21,23–31Subclinical optic nerve demyelination, however, is not easily visible on MR imaging. Routine T2-weighted images without fat suppression and contrast-enhanced T1-weighted FSE images do not show any signal abnormality in the affected optic nerve. Fat-suppressed T2-weighted FSE images, especially STIR T2-weighted images, may detect a signal-intensity abnormality in subclinical optic nerve demyelination.^23,32,33 The highly diagnostic value of fat-suppressed FLAIR images and fat-suppressed 3D DIR images in the detection of any pathologic signal intensity in the optic nerve has been evaluated in acute optic nerve demyelination.^10,34,35 In a few patients with subclinical optic nerve demyelination, signal-intensity abnormalities have been reported on 3D FLAIR.³⁴ However, there are few data about the use of the 3D DIR sequence in the evaluation of subclinical optic nerve demyelination.³⁶In our department, patients with MS are routinely and regularly monitored for disease progression by a standard protocol with 3D FLAIR, 3D DIR, T2-weighted FSE, and 3D T1-weighted postcontrast images. 3D DIR is added to our standard protocol for improved detection of juxtacortical, cortical, and infratentorial demyelinating lesions.^1–9 On the basis of postmortem and clinical studies having already shown a high percentage of subclinical optic nerve demyelination with ongoing axonal loss in patients with MS,^37–41 we wanted to test 2 hypotheses: first, that it is possible to detect signal-intensity changes in optic nerve segments on the 3D DIR sequence without the additional application of a STIR T2-weighted sequence over the orbits in patients with MS without a history of clinically obvious visual loss and without a history of acute optic neuritis during the previous 3 years; and second, that the signal-intensity changes on 3D DIR are so obvious that even inexperienced readers can detect them. This second hypothesis is important because in our department, MR imaging examinations of patients with MS are evaluated not only by trained neuroradiologists but also general radiologists. Therefore, it is desirable that the lack of neuroradiologic experience be compensated by the application of an easily readable MR image, and the 3D DIR sequence is routinely acquired in our department for the follow-up of patients with MS.For comparison, the signal intensities of normal healthy optic nerve segments in patients evaluated by the identical 3D DIR sequence for different diseases (ie, epileptic seizures and posttraumatic sequelae) were analyzed as well.     

The Role of MRI in Diagnosing Neurovascular Compression of the Cochlear Nerve Resulting in Typewriter Tinnitus

BACKGROUND AND PURPOSE:Typewriter tinnitus, a symptom characterized by paroxysmal attacks of staccato sounds, has been thought to be caused by neurovascular compression of the cochlear nerve, but the correlation between radiologic evidence of neurovascular compression of the cochlear nerve and symptom presentation has not been thoroughly investigated. The purpose of this study was to examine whether radiologic evidence of neurovascular compression of the cochlear nerve is pathognomonic in typewriter tinnitus.MATERIALS AND METHODS:Fifteen carbamazepine-responding patients with typewriter tinnitus and 8 control subjects were evaluated with a 3D T2-weighted volume isotropic turbo spin-echo acquisition sequence. Groups 1 (16 symptomatic sides), 2 (14 asymptomatic sides), and 3 (16 control sides) were compared with regard to the anatomic relation between the vascular loop and the internal auditory canal and the presence of neurovascular compression of the cochlear nerve with/without angulation/indentation.RESULTS:The anatomic location of the vascular loop was not significantly different among the 3 groups (all, P > .05). Meanwhile, neurovascular compression of the cochlear nerve on MR imaging was significantly higher in group 1 than in group 3 (P = .032). However, considerable false-positive (no symptoms with neurovascular compression of the cochlear nerve on MR imaging) and false-negative (typewriter tinnitus without demonstrable neurovascular compression of the cochlear nerve) findings were also observed.CONCLUSIONS:Neurovascular compression of the cochlear nerve was more frequently detected on the symptomatic side of patients with typewriter tinnitus compared with the asymptomatic side of these patients or on both sides of control subjects on MR imaging. However, considering false-positive and false-negative findings, meticulous history-taking and the response to the initial carbamazepine trial should be regarded as more reliable diagnostic clues than radiologic evidence of neurovascular compression of the cochlear nerve.

Arterial compression of the cochleovestibular nerve complex has been suggested as a potential cause of hearing deficit, typewriter tinnitus, and equilibrium disturbance or vertigo.^1–4 Among these clinical symptoms, typewriter tinnitus, which was first described by a pediatric cardiologist as “ear-clicking tinnitus responding to carbamazepine,”⁵ is characterized by paroxysmal attacks. It is either spontaneous or precipitated by positioning or sounds and occurs with staccato sounds described as “Morse code,” “machine gun,” “coins in a can,” “crackling,” or “typewriter” sounds.^6–8 Typewriter tinnitus is considered the result of dysmyelination and demyelination of the contact point between the arterial loop and the cochlear nerve that transmits an abnormal signal to the auditory cortex.⁹ As in other vascular compression syndromes such as trigeminal neuralgia, typewriter tinnitus is highly responsive to carbamazepine.^6–8,10,11 Complete suppression of tinnitus with carbamazepine treatment, in addition to its paroxysmal character, has led to the hypothesis that typewriter tinnitus results from neurovascular compression of the cochlear nerve (NVC-C), for which microvascular compression would be an effective treatment.^6,7However, because typewriter tinnitus is a relatively rare condition and was only recently described, few studies have been performed investigating the relationship between radiologic evidence of cochlear nerve compression on MR imaging and the presence of typewriter tinnitus, to our knowledge. A few previous studies investigating subjects with typewriter tinnitus with carbamazepine responsiveness showed evidence of NVC-C on T2-weighted CISS images; however, the sample sizes were relatively small (4 and 5 subjects, respectively), and no control subjects without tinnitus were included.^6,10 Moreover, signs of neurovascular compression have frequently been detected on MR imaging in asymptomatic patients, which raises questions about the role of MR imaging in the diagnosis of typewriter tinnitus.^7,12Thus, in this study, we aimed to evaluate MR imaging findings of subjects with typewriter tinnitus with regard to the presence of radiologic evidence of cochlear nerve compression by performing a 3D T2-weighted volume isotropic turbo spin-echo acquisition (T2-VISTA; Phillips Healthcare, Best, the Netherlands) sequence on 3T MR imaging to effectively visualize neurovascular compression. In other words, the purpose of the current study was to examine whether radiologic evidence of cochlear nerve compression is pathognomonic in subjects with typewriter tinnitus.     

Effectiveness of 3D T2-Weighted FLAIR FSE Sequences with Fat Suppression for Detection of Brain MR Imaging Signal Changes in Children

BACKGROUND AND PURPOSE:T2-weighted FLAIR can be combined with 3D-FSE sequences with isotropic voxels, yielding higher signal-to-noise ratio than 2D-FLAIR. Our aim was to explore whether a T2-weighted FLAIR–volume isotropic turbo spin-echo acquisition sequence (FLAIR-VISTA) with fat suppression shows areas of abnormal brain T2 hyperintensities with better conspicuity in children than a single 2D-FLAIR sequence.MATERIALS AND METHODS:One week after a joint training session with 20 3T MR imaging examinations (8 under sedation), 3 radiologists independently evaluated the presence and conspicuity of abnormal areas of T2 hyperintensities of the brain in FLAIR-VISTA with fat suppression (sagittal source and axial and coronal reformatted images) and in axial 2D-FLAIR without fat suppression in a test set of 100 3T MR imaging examinations (34 under sedation) of patients 2–18 years of age performed for several clinical indications. Their agreement was measured with weighted κ statistics.RESULTS:Agreement was “substantial” (mean, 0.61 for 3 observers; range, 0.49–0.69 for observer pairs) for the presence of abnormal T2 hyperintensities and “fair” (mean, 0.29; range, 0.23–0.38) for the comparative evaluation of lesion conspicuity. In 21 of 23 examinations in which the 3 radiologists agreed on the presence of abnormal T2 hyperintensities, FLAIR-VISTA with fat suppression images were judged to show hyperintensities with better conspicuity than 2D-FLAIR. In 2 cases, conspicuity was equal, and in no case was conspicuity better in 2D-FLAIR.CONCLUSIONS:FLAIR-VISTA with fat suppression can replace the 2D-FLAIR sequence in brain MR imaging protocols for children.

3D (volume) gradient-echo T1-weighted sequences are a well-established part of brain MR imaging protocols due to the intrinsically higher SNR compared with 2D sequences and the ability to obtain optimal MPR.¹ However, abnormalities of the brain are usually detected as nonspecific areas of variably increased signal in T2WI. FLAIR images are preferable to FSE images for detecting such T2 abnormalities because suppression of the CSF high signal results in an improved gray-scale dynamic range.²T2-weighted FLAIR can be combined with 3D-FSE sequences with isotropic voxels that are variably named by different vendors, including volume isotropic turbo spin-echo acquisition (VISTA; Philips Healthcare, Best, the Netherlands), SPACE (sampling perfection with application-optimized contrasts by using different flip angle evolution; Siemens, Erlangen, Germany), Cube (GE Healthcare, Milwaukee, Wisconsin), isoFSE (http://www.hitachimed.com/products/mri/oasis/Neurological/isoFSE), and 3D mVox (Toshiba, Tokyo, Japan). Such T2-weighted FLAIR 3D-FSE sequences have a higher SNR than 2D-FLAIR, enable MPR, and are less affected by CSF flow artifacts,^3–6 which are more prominent in sedated children at a higher field strength 3T magnet.^7–9Theoretically, suppression of fat signal with spectral presaturation could improve the sensitivity of FLAIR-VISTA by further narrowing the gray-scale dynamic range.²The purpose of the present study was to evaluate whether a FLAIR-VISTA sequence with fat suppression shows abnormal brain T2 signal hyperintensities with better conspicuity than a 2D-FLAIR sequence on a single axial plane in children.     

T1 Signal Measurements in Pediatric Brain: Findings after Multiple Exposures to Gadobenate Dimeglumine for Imaging of Nonneurologic Disease

BACKGROUND AND PURPOSE:Signal intensity increases possibly suggestive of gadolinium retention have recently been reported on unenhanced T1-weighted images of the pediatric brain following multiple exposures to gadolinium-based MR contrast agents. Our aim was to determine whether T1 signal changes suggestive of gadolinium deposition occur in the brains of pediatric nonneurologic patients after multiple exposures to gadobenate dimeglumine.MATERIALS AND METHODS:Thirty-four nonneurologic patients (group 1; 17 males/17 females; mean age, 7.18 years) who received between 5 and 15 injections (mean, 7.8 injections) of 0.05 mmol/kg of gadobenate during a mean of 2.24 years were compared with 24 control patients (group 2; 16 males/8 females; mean age, 8.78 years) who had never received gadolinium-based contrast agents. Exposure to gadobenate was for diagnosis and therapy monitoring. Five blinded readers independently determined the signal intensity at ROIs in the dentate nucleus, globus pallidus, pons, and thalamus on unenhanced T1-weighted spin-echo images from both groups. Unpaired t tests were used to compare signal-intensity values and dentate nucleus–pons and globus pallidus–thalamus signal-intensity ratios between groups 1 and 2.RESULTS:Mean signal-intensity values in the dentate nucleus, globus pallidus, pons, and thalamus of gadobenate-exposed patients ranged from 366.4 to 389.2, 360.5 to 392.9, 370.5 to 374.9, and 356.9 to 371.0, respectively. Corresponding values in gadolinium-based contrast agent–naïve subjects were not significantly different (P > .05). Similarly, no significant differences were noted by any reader for comparisons of the dentate nucleus–pons signal-intensity ratios. One reader noted a difference in the mean globus pallidus–thalamus signal-intensity ratios (1.06 ± 0.006 versus 1.02 ± 0.009, P = .002), but this reflected nonsignificantly higher T1 signal in the thalamus of control subjects. The number of exposures and the interval between the first and last exposures did not influence signal-intensity values.CONCLUSIONS:Signal-intensity increases potentially indicative of gadolinium deposition are not seen in pediatric nonneurologic patients after multiple exposures to low-dose gadobenate.

Recent reports have detailed high signal intensity (SI) in certain brain areas (primarily the dentate nucleus [DN] and globus pallidus [GP]) on unenhanced T1-weighted images following multiple exposures to gadolinium-based contrast agents (GBCAs).^1–20 Many of these reports have focused on apparent differences between macrocyclic and open-chain “linear” GBCAs,^4–13 invariably associating progressive T1 hyperintensity with multiple exposures to linear GBCAs and concluding that observed T1 signal reflects the lower stability of these agents and thus a greater propensity for gadolinium (Gd) release and, subsequently, deposition in the brain. Among the more recent reports are several that describe retrospective assessments in pediatric patients.^15–19 Although each patient evaluated received just 1 specific linear GBCA (gadopentetate dimeglumine; Magnevist; Bayer HealthCare, Wayne, New Jersey), the study-based recommendations in each case were to consider carefully the use of all linear agents in pediatric subjects.Gadobenate dimeglumine (MultiHance; Bracco Diagnostics, Monroe, New Jersey) is an ionic open-chain, linear GBCA that differs fundamentally from gadopentetate and other extracellular GBCAs in having an aromatic substituent on the chelating molecule.²¹ Unique properties conferred by this substituent include increased R1-relaxivity,²² which permits the acquisition of diagnostically valid images with a reduced dose,²³ and liver-specificity, which permits gadobenate use for hepatobiliary-phase liver applications.²⁴ An additional benefit is increased molecular stability compared with gadopentetate, other linear agents, and certain macrocyclic agents.²⁵ Studies that have evaluated brain T1 signal intensities after multiple exposures to gadobenate have yielded conflicting results with one report demonstrating T1 signal increases, albeit to a lesser extent than with gadopentetate,¹⁰ and others demonstrating no direct changes.^11,12We aimed to determine whether multiple exposures to low-dose gadobenate for nonneurologic pathology results in T1 signal changes in the DN and GP of pediatric patients relative to that in age- and weight-matched GBCA-naïve control subjects.     

Evaluation of Diffusivity in the Anterior Lobe of the Pituitary Gland: 3D Turbo Field Echo with Diffusion-Sensitized Driven-Equilibrium Preparation

BACKGROUND AND PURPOSE:3D turbo field echo with diffusion-sensitized driven-equilibrium preparation is a non–echo-planar technique for DWI, which enables high-resolution DWI without field inhomogeneity–related image distortion. The purpose of this study was to evaluate the feasibility of diffusion-sensitized driven-equilibrium turbo field echo in evaluating diffusivity in the normal pituitary gland.MATERIALS AND METHODS:First, validation of diffusion-sensitized driven-equilibrium turbo field echo was attempted by comparing it with echo-planar DWI. Five healthy volunteers were imaged by using diffusion-sensitized driven-equilibrium turbo field echo and echo-planar DWI. The imaging voxel size was 1.5 × 1.5 × 1.5 mm³ for diffusion-sensitized driven-equilibrium turbo field echo and 1.5 × 1.9 × 3.0 mm³ for echo-planar DWI. ADCs measured by the 2 methods in 15 regions of interests (6 in gray matter and 9 in white matter) were compared by using the Pearson correlation coefficient. The ADC in the pituitary anterior lobe was then measured in 10 volunteers by using diffusion-sensitized driven-equilibrium turbo field echo, and the results were compared with those in the pons and vermis by using a paired t test.RESULTS:The ADCs from the 2 methods showed a strong correlation (r = 0.79; P < .0001), confirming the accuracy of the ADC measurement with the diffusion-sensitized driven-equilibrium sequence. The ADCs in the normal pituitary gland were 1.37 ± 0.13 × 10⁻³ mm²/s, which were significantly higher than those in the pons (1.01 ± 0.24 × 10⁻³ mm²/s) and the vermis (0.89 ± 0.25 × 10⁻³ mm²/s, P < .01).CONCLUSIONS:We demonstrated that diffusion-sensitized driven-equilibrium turbo field echo is feasible in assessing ADC in the pituitary gland.

DWI is widely used to diagnose cerebrovascular diseases, intracranial tumors, and inflammation.^1–10 However, it is difficult to evaluate skull base structures by the most common imaging technique used with echo-planar (EP)-DWI. Previous studies have revealed the efficacy of DWI for skull base tumors such as pituitary adenoma; however, they are mostly limited to macroadenomas large enough to calculate the ADC by using EP sequences.^3–7 Compared with EP-DWI, 3D diffusion-sensitized driven-equilibrium turbo field echo (DSDE-TFE) obtained DWI has higher spatial resolution and fewer susceptibility artifacts.¹¹ To our knowledge, to date, the diffusivity of the normal pituitary gland has not been fully evaluated, especially in those glands surrounded by aerated sphenoid sinuses. Therefore, the purpose of this study was to evaluate the feasibility of DSDE-TFE in evaluating diffusivity in the normal pituitary gland.     

Evaluation of Focal Cervical Spinal Cord Lesions in Multiple Sclerosis: Comparison of White Matter–Suppressed T1 Inversion Recovery Sequence versus Conventional STIR and Proton Density–Weighted Turbo Spin-Echo Sequences

BACKGROUND AND PURPOSE:Conventional MR imaging of the cervical spinal cord in MS is challenged by numerous artifacts and interreader variability in lesion counts. This study compares the relatively novel WM-suppressed T1 inversion recovery sequence with STIR and proton density–weighted TSE sequences in the evaluation of cervical cord lesions in patients with MS.MATERIALS AND METHODS:Retrospective blinded analysis of cervical cord MR imaging examinations of 50 patients with MS was performed by 2 neuroradiologists. In each patient, the number of focal lesions and overall lesion conspicuity were measured in the STIR/proton density–weighted TSE and WM-suppressed T1 inversion recovery sequence groups. Independent side-by-side comparison was performed to categorize the discrepant lesions as either “definite” or “spurious.” Lesion contrast ratio and edge sharpness were independently calculated in each sequence.RESULTS:Substantial interreader agreement was noted on the WM-suppressed T1 inversion recovery sequence (κ = 0.82) compared with STIR/proton density–weighted TSE (κ = 0.52). Average lesion conspicuity was better on the WM-suppressed T1 inversion recovery sequence (conspicuity of 3.1/5.0 versus 3.7/5.0, P < .01, in the WM-suppressed T1 inversion recovery sequence versus STIR/proton density–weighted TSE, respectively). Spurious lesions were more common on STIR/proton density–weighted TSE than on the WM-suppressed T1 inversion recovery sequence (23 and 30 versus 3 and 4 by readers 1 and 2, respectively; P < .01). More “definite” lesions were missed on STIR/proton density–weighted TSE compared with the WM-suppressed T1 inversion recovery sequence (37 and 38 versus 3 and 6 by readers 1 and 2, respectively). Lesion contrast ratio and edge sharpness were highest on the WM-suppressed T1 inversion recovery sequence.CONCLUSIONS:There is better interreader consistency in the lesion count on the WM-suppressed T1 inversion recovery sequence compared with STIR/proton density–weighted TSE sequences. The focal cord lesions are visualized with better conspicuity due to better contrast ratio and edge sharpness. There are fewer spurious lesions on the WM-suppressed T1 inversion recovery sequence compared with STIR/proton density–weighted TSE. The WM-suppressed T1 inversion recovery sequence could potentially be substituted for either STIR or proton density–weighted TSE sequences in routine clinical protocols.

The cervical spinal cord is commonly affected in multiple sclerosis, which is often associated with an increase in clinical disability.^1–3 A focal form of involvement is more common in the relapsing-remitting variant of MS compared with the other less common MS subtypes.⁴ MS lesions undergo complex cycles of inflammation, followed by variable extent of repair and, therefore, have heterogeneity in the prolongation of T1 and T2 relaxation times, which influence their conspicuity on the standard MR imaging sequences such as STIR and proton density–weighted TSE (PDWTSE).The PDWTSE sequence with a lower TE is better than the longer TE T2-weighted sequences in the detection of focal MS lesions in the spinal cord.^5,6 STIR has intrinsic sensitivity to T1 shortening effects in addition to T2 prolongation effects and improves the lesion contrast compared with T2-weighted sequences, translating to a better interreader agreement in the assessment of the extent of disease.⁷ Nevertheless, artifacts and lower lesion conspicuity prevalent on these sequences may cause variability in the clinical evaluation of lesion burden, which is difficult to resolve in the absence of a true reference standard.⁸ Reliable characterization of the lesion burden on follow-up examinations is therefore important for assessing treatment efficacy and optimizing treatment strategies.Many novel sequences have been devised attempting to improve imaging quality and lesion conspicuity with fewer artifacts and with a reasonable acquisition time. In a smaller study population, the WM-suppressed T1 inversion recovery (WMS) sequence has shown improvement in lesion conspicuity over STIR and dual-echo fast spin-echo.⁹ While the principles of the contrast mechanism on WMS are similar to those on STIR, the sequence parameters of WMS are optimized for better intramedullary imaging. In WMS, the section-selective inversion pulse is applied at 385 ms to suppress the background signal from white matter, whereas in STIR, it is applied at 160 ms to optimize fat suppression.¹⁰ A shorter TE is used in WMS compared with STIR or PDWTSE, which further increases the T1-weighting of the sequence, which acts as the main contrast mechanism in this long TR/short TE sequence.^11,12 MS lesions have increased T1 relaxation times and thus are not suppressed with a white matter selective inversion recovery suppression pulse. There is a need for larger scale evaluation of WMS for clinical utility in routine practice against the standard sequences (STIR and PDWTSE) in the detection of MS cord lesions. The purpose of this retrospective study was to compare the utility of WMS compared with routinely used STIR and PDWTSE sequences in the evaluation of focal cervical cord lesions is MS.     

Manual Segmentation of MS Cortical Lesions Using MRI: A Comparison of 3 MRI Reading Protocols

BACKGROUND AND PURPOSE:Double inversion recovery has been suggested as the MR imaging contrast of choice for segmenting cortical lesions in patients with multiple sclerosis. In this study, we sought to determine the utility of double inversion recovery for cortical lesion identification by comparing 3 MR imaging reading protocols that combine different MR imaging contrasts.MATERIALS AND METHODS:Twenty-five patients with relapsing-remitting MS and 3 with secondary-progressive MS were imaged with 3T MR imaging by using double inversion recovery, dual fast spin-echo proton-density/T2-weighted, 3D FLAIR, and 3D T1-weighted imaging sequences. Lesions affecting the cortex were manually segmented by using the following 3 MR imaging reading protocols: Protocol 1 (P1) used all available MR imaging contrasts; protocol 2 (P2) used all the available contrasts except for double inversion recovery; and protocol 3(P3) used only double inversion recovery.RESULTS:Six hundred forty-three cortical lesions were identified with P1 (mean = 22.96); 633, with P2 (mean = 22.6); and 280, with P3 (mean = 10). The counts obtained by using P1 and P2 were not significantly different (P = .93). The counts obtained by using P3 were significantly smaller than those obtained by using either P1 (P < .001) or P2 (P < .001). The intraclass correlation coefficients were P1 versus P2 = 0.989, P1 versus P3 = 0.615, and P2 versus P3 = 0.588.CONCLUSIONS:MR imaging cortical lesion segmentation can be performed by using 3D T1-weighted and 3D FLAIR images acquired with a 1-mm isotropic voxel size, supported by conventional T2-weighted and proton-density images with 3-mm-thick sections. Inclusion of double inversion recovery in this multimodal reading protocol did not significantly improve the cortical lesion identification rate. A multimodal approach is superior to using double inversion recovery alone.

Multiple sclerosis is an inflammatory and neurodegenerative disease that affects both the white matter and gray matter of the central nervous system. Postmortem immunohistochemical characterization of cortical lesions (CLs) has allowed the identification of a substantial burden of cortical GM lesions in patients with long-standing MS.^1–5 However, the prevalence of cortical lesions at earlier stages of MS is underexplored.⁶ As a result, an efficient, standardized MR imaging protocol for segmentation of CLs in early-stage MS has become an important research goal. Double inversion recovery (DIR) MR imaging has generally been selected because it enhances the conspicuity of GM by suppressing unwanted signal from both WM and CSF. However, DIR images have a low signal-to-noise ratio due to the application of 2 inversion pulses. They are also prone to hyperintense vascular artifacts, which can confound CL identification.^7–14In 2011, an international panel of experts formulated consensus recommendations for scoring CLs at 1.5T and 3T by using DIR.¹¹ As part of the recommendations, they noted that in the future, the additional use of other MR imaging contrasts (T1-weighted, T2-weighted, or fluid-attenuated inversion recovery images) in combination with DIR could improve the detection of cortical lesions by reducing the number of false-positives and false-negatives. Several groups have since reported on such multicontrast approaches for segmenting CLs. Examples include the following: 1) CL segmentation performed by using a single MR imaging contrast followed by subsequent verification of lesion labels on other contrasts¹³; 2) CL segmentation performed independently by using 2 different MR imaging contrasts, where a tight correlation between the counts is considered evidence that each MR imaging contrast yields counts proportional to the real lesion load¹⁵; 3) CL segmentation performed by using a single MR imaging contrast with the results subsequently reviewed by a second (more experienced) rater who uses other contrasts to resolve ambiguities/potential false-positives¹⁶; and 4) CL segmentation performed independently for each independent contrast, and then each count compared with the counts obtained from the other MR imaging contrasts to determine which one detects the highest number of lesions.¹⁷ The variability among these methods has led to difficulty in developing a standardized CL segmentation protocol.¹¹ Consequently, a major goal of this work was to identify a robust, multicontrast CL segmentation protocol that could be used with more generally available MR imaging pulse sequences at clinically accessible magnetic field strengths.According to the consensus recommendations, only type I leukocortical and type II intracortical lesions should be considered for radiologic scoring¹¹ in MS. However, type I lesions affecting both the cortex and the juxtacortical white matter are often difficult to differentiate from purely juxtacortical lesions. Consequently, these lesions can be misclassified. Type II lesions are the smallest and affect the cortex without reaching either the pial or white matter boundaries. These lesions are also challenging to detect visually by using 1.5T or 3T MR imaging. Subpial lesions (type III and IV), extending from the pial boundary down to the white matter surface, are not considered within the consensus guidelines for MR imaging at 1.5 and 3T due to their low detectability at these clinical field strengths. Even with these simplifying assumptions in place, CL identification has been highly variable.^10,13,18,19 The prevalence of MR imaging–identified intracortical lesions ranges from 8.2% to 46% across different published reports.^{10,12,13,18,19} This variability may partially reflect the variable sensitivity of current MR imaging protocols but also may indicate the inherent variability of cortical lesion involvement across MS disease stages and individual patients. Support for this hypothesis is provided by histology studies in which the percentage of intracortical lesions (type II) also shows a wide range: 7%–31% and 17%–71% when we consider types I and type II combined.^{1–6,19,20,21}A significant aim of our study was to simplify and improve the process of manual cortical lesion segmentation when using multiple MR imaging contrasts derived from 3T MR imaging. We specifically strived to identify a lesion-segmentation method with reduced variability and reduced false-positive identifications. To do this, we avoided classification of cortical lesions into subtypes.     

Comparison of Readout-Segmented Echo-Planar Imaging and Single-Shot TSE DWI for Cholesteatoma Diagnostics

BACKGROUND AND PURPOSE:The high diagnostic value of DWI for cholesteatoma diagnostics is undisputed. This study compares the diagnostic value of readout-segmented echo-planar DWI and single-shot TSE DWI for cholesteatoma diagnostics.MATERIALS AND METHODS:Thirty patients with newly suspected cholesteatoma were examined with a dedicated protocol, including readout-segmented echo-planar DWI and single-shot TSE DWI at 1.5T. Acquisition parameters of both diffusion-weighted sequences were as follows: b=1000 s/mm,² axial and coronal section orientations, and section thickness of 3 mm. Image quality was evaluated by 2 readers on a 5-point Likert scale with respect to lesion conspicuity, the presence of susceptibility artifacts mimicking cholesteatomas, and overall subjective image quality. Sensitivity and specificity were calculated using histology results as the gold standard.RESULTS:Twenty-five cases of histologically confirmed cholesteatomas were included in the study group. Lesion conspicuity was higher and fewer artifacts were found when using TSE DWI (both P < .001). The overall subjective image quality, however, was better with readout-segmented DWI. For TSE DWI, the sensitivity for readers 1 and 2 was 92% (95% CI, 74%–99%) and 88% (95% CI, 69%–97%), respectively, while the specificity for both readers was 80% (95% CI, 28%–99%). For readout-segmented DWI, the sensitivity for readers 1 and 2 was 76% (95% CI, 55%–91%) and 68% (95% CI, 46%–85%), while the specificity for both readers was 60% (95% CI, 15%–95%).CONCLUSIONS:The use of TSE DWI is advisable for cholesteatoma diagnostics and preferable over readout-segmented DWI.

Cholesteatoma is a common non-neoplastic disease in otology, characterized by collections of trapped keratinous debris within a sack of stratified epithelium, typically found in the middle ear and capable of causing a progressive inflammatory process.¹ Clinical complications include the destruction of adjacent bone and ossicular structures, which can lead to conductive or sensoneuronal hearing loss.^2,3 Cholesteatoma is commonly treated with surgery, ranging from focal excision to radical mastoidectomy.⁴ A second-look surgery procedure is typically performed within the first 2 years after the initial surgery to identify residual or recurrent cholesteatoma foci. Unlike canal wall down mastoidectomy, visual inspection of canal wall up mastoidectomy can be challenging; hence, a reliable diagnostic imaging tool is desirable for accurate follow-up diagnosis and treatment.^5–7 Preoperative high-resolution CT is the method of choice for the detection of osseous disintegration and is sufficient for diagnosis; however, for recurrent cholesteatoma after surgery, its role may be more limited.⁸ MR imaging is suitable for the assessment pre- and postsurgery using DWI and delayed postcontrast T1-weighted spin-echo imaging, which enable differentiation between keratinous debris and noncholesteatoma findings such as granulation tissue or scar.⁹The value of DWI in cholesteatoma diagnostics was initially shown using echo-planar DWI sequences.^10-12 Alternative approaches have been proposed for cholesteatoma diagnostics such as diffusion-sensitized driven-equilibrium DWI¹³ and PROPELLER TSE DWI (tseDWI).¹⁴ Notably, tseDWI techniques introduce radiofrequency refocusing pulses between the k-space lines and are, therefore, not able to easily fulfill the Carr-Purcell-Meibom-Gill Sequence condition if diffusion encoding is applied—an issue that must be addressed in the sequence design and essentially often degrades the image quality.¹⁵ Nonetheless, several studies have suggested single-shot tseDWI to be superior in terms of diagnostic accuracy compared with single-shot echo-planar DWI.^16-18 The image quality of EPI in the temporal region is often degraded due to the inhomogeneous magnetic environment at the skull base. Moreover, regions adjacent to bone- or air-filled spaces can artificially appear hyperintense, which can be misleading and result in false-positive findings.Readout-segmented echo-planar DWI (rsDWI)¹⁹ as a derivative of conventional echo-planar DWI can be used to minimize the geometric distortions to improve both image quality and diagnostic accuracy.^20,21 In a recently published work by Algin et al,²¹ rsDWI proved to be superior to single-shot EPI sequences for cholesteatoma diagnostics. Hence, this study sought to compare rsDWI and tseDWI, focusing on image quality and performance in cholesteatoma diagnostics.     

Comparison of Sagittal FSE T2, STIR,and T1-Weighted Phase-Sensitive Inversion Recovery in the Detection of Spinal Cord Lesions in MS at 3T

BACKGROUND AND PURPOSE:Determining the diagnostic accuracy of different MR sequences is essential to design MR imaging protocols. The purpose of the study was to compare 3T sagittal FSE T2, STIR, and T1-weighted phase-sensitive inversion recovery in the detection of spinal cord lesions in patients with suspected or definite MS.MATERIALS AND METHODS:We performed a retrospective analysis of 38 patients with suspected or definite MS. Involvement of the cervical and thoracic cord segments was recorded on sagittal FSE T2, STIR, and T1-weighted phase-sensitive inversion recovery sequences independently by 2 readers. A consensus criterion standard read was performed with all sequences available. Sensitivity, specificity, and interobserver agreement were calculated for each sequence.RESULTS:In the cervical cord, the sensitivity of T1-weighted phase-sensitive inversion recovery (96.2%) and STIR (89.6%) was significantly higher (P < .05) than that of FSE T2 (50.9%), but no significant difference was found between T1-weighted phase-sensitive inversion recovery and STIR. In the thoracic cord, sensitivity values were 93.8% for STIR, 71.9% for FSE T2, and 50.8% for T1-weighted phase-sensitive inversion recovery. Significant differences were found for all comparisons (P < .05). No differences were detected in specificity. Poor image quality and lower sensitivity of thoracic T1-weighted phase-sensitive inversion recovery compared with the other 2 sequences were associated with a thicker back fat pad.CONCLUSIONS:The use of an additional sagittal sequence other than FSE T2 significantly increases the detection of cervical and thoracic spinal cord lesions in patients with MS at 3T. In the cervical segment, both STIR and T1-weighted phase-sensitive inversion recovery offer high sensitivity and specificity, whereas in the thoracic spine, STIR performs better than T1-weighted phase-sensitive inversion recovery, particularly in patients with a thick dorsal fat pad.

MR imaging of the spinal cord is an important diagnostic technique in MS because the prevalence of spinal cord abnormalities in patients with clinically isolated syndrome is as high as 42%.¹ In clinically diagnosed MS, spinal cord involvement reaches 75%–92%, depending on the series.^2–4 The presence of asymptomatic cord lesions contributes to the demonstration of dissemination in space in the McDonald 2010 criteria for MS, and imaging of the spinal cord allows an increase of 18.3% in the number of patients meeting the diagnostic criteria.⁵ The presence of spinal cord lesions not only facilitates diagnosing MS but is also predictive of conversion to clinically definite MS, especially in patients with nonspinal clinically isolated syndrome who do not fulfill brain MR imaging criteria.⁶ Moreover, spinal cord lesions in MS can occur in isolation in 5% of patients, particularly in primary-progressive MS.⁷Spinal cord imaging is challenging because the spinal cord is a small and mobile structure.⁸ In addition, its anatomic location makes it prone to ghosting artifacts caused by the heart and great vessels as well as truncation artifacts. 3T MR imaging compared with 1.5T is more prone to artifacts caused by B₁ field inhomogeneity,⁹ susceptibility, vascular pulsation, and chemical shift.^10,11 In addition, 3T MR imaging has a higher energy deposit within the tissue, resulting in a higher specific absorption rate than lower field scanners. These problems can be partially solved with various technical adjustments and fast (parallel) imaging.¹²Traditionally, the spinal cord in patients with MS has been imaged by using sagittal and axial FSE T2/proton density sequences. Additional sequences, including STIR^13,14 and T1 inversion recovery,¹⁵ have shown promise by increasing lesion visibility, particularly at 3T, in which conventional FSE T2 and proton density images are frequently unsatisfactory.¹⁶ STIR has proved very useful as a complementary sequence in the detection of MS lesions but cannot be used in isolation due to its lower specificity.^13,14 Numerous studies have demonstrated the superiority of STIR over T2 at 1.5T,^{13,14,17–19} and 1 study¹⁵ also showed the advantages of STIR at 3T in the cervical cord. To our knowledge, no studies have been performed in the thoracic cord comparing sagittal FSE T2 and STIR. A recent publication showed the advantages of T1-weighted phase-sensitive inversion recovery (PSIR) for the detection of cervical spinal cord lesions in MS at 3T.¹⁶ PSIR has been shown to improve lesion localization and boundary definition over STIR in the cervical spinal cord, but it has not been tested in the thoracic cord.¹⁶The aim of our study was to compare the sensitivity and specificity of sagittal STIR, PSIR, and FSE T2 in the detection of MS spinal cord lesions at 3T, in both the cervical and thoracic segments.     

Optimal Diagnostic Indices for Idiopathic Normal Pressure Hydrocephalus Based on the 3D Quantitative Volumetric Analysis for the Cerebral Ventricle and Subarachnoid Space

BACKGROUND AND PURPOSE:Despite the remarkable progress of 3D graphics technology, the Evans index has been the most popular index for ventricular enlargement. We investigated a novel reliable index for the MR imaging features specified in idiopathic normal pressure hydrocephalus, rather than the Evans index.MATERIALS AND METHODS:The patients with suspected idiopathic normal pressure hydrocephalus on the basis of the ventriculomegaly and a triad of symptoms underwent the CSF tap test. CSF volumes were extracted from a T2-weighted 3D spin-echo sequence named “sampling perfection with application-optimized contrasts by using different flip angle evolutions (SPACE)” on 3T MR imaging and were quantified semiautomatically. Subarachnoid spaces were divided as follows: upper and lower parts and 4 compartments of frontal convexity, parietal convexity, Sylvian fissure and basal cistern, and posterior fossa. The maximum length of 3 axial directions in the bilateral ventricles and their frontal horns was measured. The “z-Evans Index” was defined as the maximum z-axial length of the frontal horns to the maximum cranial z-axial length. These parameters were evaluated for the predictive accuracy for the tap-positive groups compared with the tap-negative groups and age-adjusted odds ratios at the optimal thresholds.RESULTS:In this study, 24 patients with tap-positive idiopathic normal pressure hydrocephalus, 25 patients without response to the tap test, and 23 age-matched controls were included. The frontal horns of the bilateral ventricles were expanded, with the most excessive expansion being toward the z-direction. The CSF volume of the parietal convexity had the highest area under the receiver operating characteristic curve (0.768), the z-Evans Index was the second (0.758), and the upper-to-lower subarachnoid space ratio index was the third (0.723), to discriminate the tap-test response.CONCLUSIONS:The CSF volume of the parietal convexity of <38 mL, upper-to-lower subarachnoid space ratio of <0.33, and the z-Evans Index of >0.42 were newly proposed useful indices for the idiopathic normal pressure hydrocephalus diagnosis, an alternative to the Evans Index.

Idiopathic normal pressure hydrocephalus (iNPH) has been diagnosed since the evidence-based guidelines for diagnosis and management of iNPH were announced in Japan, the United States, and Europe.^1–5 Frequently, patients with iNPH have short-stepped gaits at first, followed by cognitive impairment and urinary incontinence. The Study of iNPH on Neurologic Improvement (SINPHONI) showed that narrow sulci at the high convexity and an enlarged Sylvian fissure with ventricular dilation, which was designated as “disproportionately enlarged subarachnoid-space hydrocephalus (DESH),” were important MR imaging features for iNPH diagnosis.⁶ The SINPHONI also confirmed that a lumbar CSF tap test was a necessary diagnostic test for probable iNPH and predicted a favorable response to a ventriculoperitoneal shunt surgery.⁷Despite the remarkable progress of 3D graphics technology, the Evans Index proposed by William Evans in 1942 has been the most popular index of ventricular enlargement,⁸ and an Evans Index of >0.3 has been adopted as a criterion for ventriculomegaly in the Japanese and international iNPH guidelines.^1–5 However, some studies using volumetric analysis suggested that it was not a sufficient linear index for evaluating ventricular enlargement.^9,10 In recent years, a T2-weighted 3D spin-echo sequence with sampling perfection with application-optimized contrasts by using different flip angle evolutions (SPACE sequence; Siemens, Erlangen, Germany) has been developed.^11–14 This volumetric sequence enables the decrease of specific absorption rate limits and a scan of the whole brain in a single slab and a true isotropic 3D data record with high resolution (voxel size ≤ 1 mm³ without interpolation). Taking advantage of the high sensitivity to detect CSF on the T2-weighted 3D-SPACE sequence, a new automated segmentation technique by using a simple threshold algorithm has been developed.¹⁵ The aim of the present study was to investigate the association between several 1D and 3D parameters of the ventricles and subarachnoid space and the response to the CSF tap test in patients with suspected iNPH in a systematic manner.     

Preoperative MRI Evaluation of Thyroid Cartilage Invasion in Patients with Laryngohypopharyngeal Cancer: Comparison of Contrast-Enhanced 2D Spin-Echo and 3D T1-Weighted Radial Gradient Recalled-Echo Techniques

BACKGROUND AND PURPOSE:Accurate assessment of thyroid cartilage invasion on preoperative imaging influences management in patients with laryngeal and hypopharyngeal cancers. We evaluated the clinical usefulness of contrast-enhanced 3D T1-weighted radial gradient recalled-echo for preoperative assessment of thyroid cartilage invasion in patients with laryngohypopharyngeal squamous cell carcinoma, compared with 2D spin-echo T1WI.MATERIALS AND METHODS:Preoperative MR images of 52 consecutive patients who were diagnosed with laryngeal or hypopharyngeal cancer and underwent partial or total laryngectomy were analyzed. Pathologic specimens served as reference standards. Two independent head and neck radiologists evaluated the presence of thyroid cartilage invasion in both contrast-enhanced 2D spin-echo T1WI and 3D gradient recalled-echo sequences. The sensitivity, specificity, and accuracy of the 2 modalities were compared. The area under the curve was a measure of diagnostic performance.RESULTS:Pathologic neoplastic thyroid cartilage invasion was identified in 24 (46.2%) of the 52 patients. The sensitivity (75.0%), specificity (96.4%), and accuracy (86.5%) of contrast-enhanced 3D gradient recalled-echo were significantly higher than those of 2D spin-echo T1WI (58.3%, 89.3%, and 75.0%; P = .017, .003, and .002, respectively). 3D gradient recalled-echo had significantly better diagnostic performance (area under the curve = 0.963) than 2D spin-echo T1WI (area under the curve = 0.862; P = .010).CONCLUSIONS:Contrast-enhanced 3D gradient recalled-echo was diagnostically superior in identifying neoplastic thyroid cartilage invasion compared with 2D spin-echo T1WI in patients with laryngohypopharyngeal cancer, and therefore, may provide more accurate preoperative staging.

Accurate preoperative staging is crucial for deciding appropriate treatment strategies and predicting prognosis in patients with head and neck cancers. Specifically, in laryngeal and hypopharyngeal cancers, treatment strategies vary with the presence of thyroid cartilage invasion.¹ If the tumor is localized without extension to the thyroid cartilage, larynx-preserving treatment can be performed. On the contrary, if the tumor extends through the thyroid cartilage, more invasive treatment such as total laryngectomy is considered.^2-7 Thus, accurate assessment of thyroid cartilage invasion preoperatively is highly desirable in patients with laryngeal and hypopharyngeal cancers.MR imaging has been shown to be superior to CT in the assessment of cartilage invasion because of its excellent soft-tissue contrast.^8-10 Becker et al⁹ proposed new diagnostic criteria based on MR imaging to improve the distinction between tumor tissue and peritumoral inflammation involving the laryngeal cartilage in patients with laryngeal and hypopharyngeal cancers. Although MR imaging in head and neck cancer is most widely performed with a conventional 2D spin-echo (SE) sequence, 3D volumetric imaging has emerged as an alternative because it allows isotropic data acquisition with multiplanar image reconstruction, within an acceptable acquisition time. In addition, T1-weighted high-resolution isotropic volume examination (THRIVE), a 3D ultrafast spoiled gradient MR imaging sequence that incorporates a frequency-selective fat-saturation pulse, was recently shown to be clinically superior for preoperative evaluation of head and neck cancer, providing more accurate measurement of tumor size and higher sensitivity to detect the primary tumor in patients with cervical lymph node metastases of unknown primary tumors, compared with 2D SE T1WI.^11,12We hypothesized that contrast-enhanced 3D gradient recalled-echo (GRE) might allow more accurate identification of neoplastic thyroid cartilage invasion compared with 2D SE T1WI in patients with laryngohypopharyngeal cancer. The aim of the present study was to investigate the potential of GRE for the preoperative assessment of thyroid cartilage invasion in patients with laryngohypopharyngeal cancer by comparing it with 2D SE T1WI.     

Measurement of Cortical Thickness and Volume of Subcortical Structures in Multiple Sclerosis: Agreement between 2D Spin-Echo and 3D MPRAGE T1-Weighted Images

BACKGROUND AND PURPOSE:Gray matter pathology is known to occur in multiple sclerosis and is related to disease outcomes. FreeSurfer and the FMRIB Integrated Registration and Segmentation Tool (FIRST) have been developed for measuring cortical and subcortical gray matter in 3D-gradient-echo T1-weighted images. Unfortunately, most historical MS cohorts do not have 3D-gradient-echo, but 2D-spin-echo images instead. We aimed to evaluate whether cortical thickness and the volume of subcortical structures measured with FreeSurfer and FIRST could be reliably measured in 2D-spin-echo images and to investigate the strength and direction of clinicoradiologic correlations.MATERIALS AND METHODS:Thirty-eight patients with MS and 2D-spin-echo and 3D-gradient-echo T1-weighted images obtained at the same time were analyzed by using FreeSurfer and FIRST. The intraclass correlation coefficient between the estimates was obtained. Correlation coefficients were used to investigate clinicoradiologic associations.RESULTS:Subcortical volumes obtained with both FreeSurfer and FIRST showed good agreement between 2D-spin-echo and 3D-gradient-echo images, with 68.8%–76.2% of the structures having either a substantial or almost perfect agreement. Nevertheless, with FIRST with 2D-spin-echo, 18% of patients had mis-segmentation. Cortical thickness had the lowest intraclass correlation coefficient values, with only 1 structure (1.4%) having substantial agreement. Disease duration and the Expanded Disability Status Scale showed a moderate correlation with most of the subcortical structures measured with 3D-gradient-echo images, but some correlations lost significance with 2D-spin-echo images, especially with FIRST.CONCLUSIONS:Cortical thickness estimates with FreeSurfer on 2D-spin-echo images are inaccurate. Subcortical volume estimates obtained with FreeSurfer and FIRST on 2D-spin-echo images seem to be reliable, with acceptable clinicoradiologic correlations for FreeSurfer.

Gray matter pathology in patients with multiple sclerosis is present from the very early stages of the disease and has been related to long-term disability.^1,2 Therefore, in recent years, research has focused on obtaining accurate markers of GM damage, and different software packages have been developed or optimized for measuring it in MS. FreeSurfer software (http://surfer.nmr.mgh.harvard.edu)^3,4 allows automatic calculation of cortical thickness and the volume of subcortical GM structures by using 3D T1-weighted images. Briefly, the image-processing pipeline includes Talairach transformation of the 3D T1-weighted images and segmentation of the subcortical white matter and deep GM structures, relying on the gray and white matter boundaries and pial surfaces. The FMRIB Integrated Registration and Segmentation Tool (FIRST; http://fsl.fmrib.ox.ac.uk/fsl/fslwiki/FIRST) software package⁵ automatically segments subcortical GM structures also on the basis of 3D T1-weighted images. Briefly, FIRST is a model-based segmentation and registration program that uses shape and appearance models constructed from manually segmented images. On the basis of the learned models, FIRST searches through linear combinations of shape modes of variation for the most probable shape instance, given the observed intensities in the 3D T1-weighted input images. Both software packages have been shown to be accurate and reproducible.^6–11The study of cortical pathology in patients with MS by using FreeSurfer has shown cortical thinning in patients with MS compared with healthy controls,^12,13 which has been related to lesion volume, disease duration, disability,¹² and cognitive impairment.¹⁴ Also, cortical thinning of the superior frontal gyrus, thalamus, and cerebellum significantly predicted conversion to MS in patients presenting with clinically isolated syndromes,¹⁵ and global cortical thinning for 6 years was significantly associated with a more aggressive disease evolution.¹⁶ The volume of deep GM structures (measured with both FreeSurfer and FIRST) has also been shown to be lower in patients with MS compared with healthy controls,^17–19 and it has been related to different clinical disease outcomes such as fatigue,²⁰ cognitive impairment,^17–19,21 disability,¹⁹ and walking function.²²Both FreeSurfer and FIRST have been optimized for 3D T1-weighted gradient-echo images that incorporate a magnetization-prepared inversion pulse that increases the T1-weighting.²³ Unfortunately, for most of the historical MS cohorts with long-term clinical and radiologic follow-up, only 2D spin-echo (2D-SE) T1-weighted images were acquired, a sequence that does not provide an optimal contrast between gray and white matter, particularly when acquired with high-field magnets.²⁴ The objectives of this work were the following: 1) to evaluate whether cortical thickness and subcortical volumes obtained with FreeSurfer could be reliably measured with 2D-SE T1-weighted images by using as the criterion standard the same measures obtained with 3D gradient-echo (3D-GE) T1-weighted sequences, 2) to investigate whether subcortical volumes obtained with FIRST could be reliably measured in 2D-SE T1-weighted images by using as the criterion standard the same measures obtained with 3D-GE T1-weighted images, and 3) to assess whether the correlations between clinical outcomes and subcortical normalized volumes obtained with 3D-GE and 2D-SE T1-weighted images had a similar strength and direction.     

Comparison of CSF Distribution between Idiopathic Normal Pressure Hydrocephalus and Alzheimer Disease

BACKGROUND AND PURPOSE:CSF volumes in the basal cistern and Sylvian fissure are increased in both idiopathic normal pressure hydrocephalus and Alzheimer disease, though the differences in these volumes in idiopathic normal pressure hydrocephalus and Alzheimer disease have not been well-described. Using CSF segmentation and volume quantification, we compared the distribution of CSF in idiopathic normal pressure hydrocephalus and Alzheimer disease.MATERIALS AND METHODS:CSF volumes were extracted from T2-weighted 3D spin-echo sequences on 3T MR imaging and quantified semi-automatically. We compared the volumes and ratios of the ventricles and subarachnoid spaces after classification in 30 patients diagnosed with idiopathic normal pressure hydrocephalus, 10 with concurrent idiopathic normal pressure hydrocephalus and Alzheimer disease, 18 with Alzheimer disease, and 26 control subjects 60 years of age or older.RESULTS:Brain to ventricle ratios at the anterior and posterior commissure levels and 3D volumetric convexity cistern to ventricle ratios were useful indices for the differential diagnosis of idiopathic normal pressure hydrocephalus or idiopathic normal pressure hydrocephalus with Alzheimer disease from Alzheimer disease, similar to the z-Evans index and callosal angle. The most distinctive characteristics of the CSF distribution in idiopathic normal pressure hydrocephalus were small convexity subarachnoid spaces and the large volume of the basal cistern and Sylvian fissure. The distribution of the subarachnoid spaces in the idiopathic normal pressure hydrocephalus with Alzheimer disease group was the most deformed among these 3 groups, though the mean ventricular volume of the idiopathic normal pressure hydrocephalus with Alzheimer disease group was intermediate between that of the idiopathic normal pressure hydrocephalus and Alzheimer disease groups.CONCLUSIONS:The z-axial expansion of the lateral ventricle and compression of the brain just above the ventricle were the common findings in the parameters for differentiating idiopathic normal pressure hydrocephalus from Alzheimer disease.

Idiopathic normal pressure hydrocephalus (iNPH) has been diagnosed with several highly sensitive radiologic findings since the evidence-based guidelines for the diagnosis and management of iNPH were announced.^1–11 Due to the expansion of the lateral ventricles toward the vertex, upward displacement of the superior parietal lobule and decrease of the subarachnoid space at part of the high parietal convexity area are specific morphologic features for iNPH, called “disproportionately enlarged subarachnoid-space hydrocephalus (DESH).”¹ As an alternative to the Evans index, we recently proposed that the “z-Evans index,” which was defined as the maximum z-axial length of the frontal horns of the lateral ventricles to the maximum cranial z-axial length, was useful for iNPH diagnosis.¹² iNPH occurs in the elderly population prone to many types of comorbidities including Alzheimer disease (AD).^13–21 Therefore, differential diagnosis between iNPH and AD with brain atrophy is important, though the quantitative rating system on MR imaging to distinguish iNPH from AD with brain atrophy has not yet been established, to our knowledge.A new automated segmentation technique by using a simple threshold algorithm has been developed, taking advantage of the high sensitivity to detect CSF on the T2-weighted 3D spin-echo sampling perfection with application-optimized contrasts by using different flip angle evolution (SPACE) sequence.^12,22–24 The aim of the present study was to establish a novel representative characteristic of CSF volume and distribution, which can differentiate iNPH from AD.     

Cumulative Dose of Macrocyclic Gadolinium-Based Contrast Agent Improves Detection of Enhancing Lesions in Patients with Multiple Sclerosis

BACKGROUND AND PURPOSE:Gadolinium-enhanced MR imaging is currently the reference standard for detecting active inflammatory lesions in patients with multiple sclerosis. The sensitivity of MR imaging for this purpose may vary according to the physicochemical characteristics of the contrast agent used and the acquisition strategy. The purpose of this study was to compare detection of gadolinium-enhancing lesions or active disease following a single or cumulative dose of a macrocyclic gadolinium-based contrast agent with different image acquisition delays in patients with clinically isolated syndrome or relapsing multiple sclerosis.MATERIALS AND METHODS:All patients received a first dose (0.1 mmol/kg) of gadobutrol and, 20 minutes later, a second dose (0.1 mmol/kg), with a cumulative dose of 0.2 mmol/kg. Two contrast-enhanced T1-weighted sequences were performed at 5 and 15 minutes after the first contrast administration, and 2 additional T1-weighted sequences at 5 and 15 minutes after the second contrast administration with a 3T magnet.RESULTS:One hundred fifteen patients were considered evaluable. A significantly larger number of lesions were detected in scans obtained at 5 and 15 minutes after the second contrast injection compared with scans obtained at 5 and 15 minutes after the first injection (P < .001). The number of patients with active lesions on MR imaging was significantly higher after the second dose administration (52.0%, first dose versus 59.2%, second dose; P < .001).CONCLUSIONS:Cumulative dosing of a macrocyclic gadolinium-based contrast agent increases detection of enhancing lesions and patients with active lesions. These data could be considered in the design of MR imaging protocols aimed at detecting active multiple sclerosis lesions.

Gadolinium-enhanced MR imaging is currently the reference standard for detecting inflammatory demyelinating lesions associated with increased permeability of the blood-brain barrier in patients with multiple sclerosis, and is commonly used as a marker of acute focal inflammatory activity.^1,2 The sensitivity of the technique for this purpose may vary according to the physicochemical characteristics of the contrast agent used and the acquisition strategy (eg, delay between injection and image acquisition, contrast dose, field strength, and parameters of the postinjection T1-weighted sequence).^3–12 A large body of evidence has indicated that various approaches can increase the visibility of contrast-enhancing lesions and lead to a notable improvement in sensitivity.^{3,4,8,9,12–15} One potential strategy that has not yet been explored is the combination of an increased contrast dose and a longer delay time at 3T MR imaging with a 2D gradient recalled-echo (GRE) T1-weighted sequence. To examine this option, we designed the present open-label, prospective study to assess the advantages of combining a high-field-strength MR imaging magnet (3T) and a cumulative gadolinium dose (0.1 mmol/kg + 0.1 mmol/kg) at different delay times compared with a single dose (0.1 mmol/kg) to detect active lesions in patients with clinically isolated syndrome (CIS) or relapsing MS. The hypothesis was that the combined advantages of a cumulative gadolinium dose and a longer delay time would significantly increase the detection rate of active lesions and the percentage of patients showing disease activity, measures that have a strong impact for the diagnosis of the disease, therapy optimization, and predicting disease course and treatment response.^1,2,16     

Direct Visualization of Anatomic Subfields within the Superior Aspect of the Human Lateral Thalamus by MRI at 7T

BACKGROUND AND PURPOSE:The morphology of the human thalamus shows high interindividual variability. Therefore, direct visualization of landmarks within the thalamus is essential for an improved definition of electrode positions for deep brain stimulation. The aim of this study was to provide anatomic detail in the thalamus by using inversion recovery TSE imaging at 7T.MATERIALS AND METHODS:The MR imaging protocol was optimized on 1 healthy subject to segment thalamic nuclei from one another. Final images, acquired with 0.5²-mm² in-plane resolution and 3-mm section thickness, were compared with stereotactic brain atlases to assign visualized details to known anatomy. The robustness of the visualization of thalamic nuclei was assessed with 4 healthy subjects at lower image resolution.RESULTS:Thalamic subfields were successfully delineated in the dorsal aspect of the lateral thalamus. T1-weighting was essential. MR images had an appearance very similar to that of myelin-stained sections seen in brain atlases. Visualized intrathalamic structures were, among others, the lamella medialis, the external medullary lamina, the reticulatum thalami, the nucleus centre médian, the boundary between the nuclei dorso-oralis internus and externus, and the boundary between the nuclei dorso-oralis internus and zentrolateralis intermedius internus.CONCLUSIONS:Inversion recovery–prepared TSE imaging at 7T has a high potential to reveal fine anatomic detail in the thalamus, which may be helpful in enhancing the planning of stereotactic neurosurgery in the future.

MR imaging, due to its excellent soft-tissue-contrast capabilities, has become the most important imaging technique for the living brain. Nevertheless, the thalamus, characterized by its rich structural variety,^1–3 appears virtually isointense in routine high-resolution MR images. The lack of visible anatomic detail within the thalamus affects presurgical planning of deep brain stimulation (DBS) procedures. Considering that thalamic morphology can show significant interindividual variability,³ direct visualization of intrathalamic anatomy is necessary for a more precise patient-specific planning of brain electrode positions.Besides the small size of some thalamic nuclei, the main reason for the lack of contrast is the similarity of MR imaging–relevant tissue parameters such as relaxation times and/or proton densities of adjacent thalamic structures. However, as long as differences in contrast-relevant tissue properties exist, their delineation by an appropriate MR imaging technique is mainly a question of SNR. Several years ago, the wide availability of 3T MR imaging scanners triggered a series of studies aiming to visualize internal substructures of the thalamus,^4–11 extending the research done at 1.5T.^12–16 Although noticeable progress was made, the visualization of thalamic nuclei with 3T MR imaging for DBS surgery is not a clinical routine to date. It seemed reasonable to assume that the SNR boost offered by MR imaging at 7T could further improve the visualization of thalamic nuclei. Indeed, the first encouraging results have been reported by using SWI, quantitative susceptibility mapping, and MPRAGE imaging.^17–19 This feasibility study aims to investigate the usefulness of inversion recovery turbo-spin-echo (IR-TSE) MR imaging at 7T in revealing anatomic detail within the thalamus. This task comprises both the optimization of the MR imaging acquisition and the assignment of visualized structures to thalamic anatomy.     

Differentiation between Cystic Pituitary Adenomas and Rathke Cleft Cysts: A Diagnostic Model Using MRI

BACKGROUND AND PURPOSE:Cystic pituitary adenomas may mimic Rathke cleft cysts when there is no solid enhancing component found on MR imaging, and preoperative differentiation may enable a more appropriate selection of treatment strategies. We investigated the diagnostic potential of MR imaging features to differentiate cystic pituitary adenomas from Rathke cleft cysts and to develop a diagnostic model.MATERIALS AND METHODS:This retrospective study included 54 patients with a cystic pituitary adenoma (40 women; mean age, 37.7 years) and 28 with a Rathke cleft cyst (18 women; mean age, 31.5 years) who underwent MR imaging followed by surgery. The following imaging features were assessed: the presence or absence of a fluid-fluid level, a hypointense rim on T2-weighted images, septation, an off-midline location, the presence or absence of an intracystic nodule, size change, and signal change. On the basis of the results of logistic regression analysis, a diagnostic tree model was developed to differentiate between cystic pituitary adenomas and Rathke cleft cysts. External validation was performed for an additional 16 patients with a cystic pituitary adenoma and 8 patients with a Rathke cleft cyst.RESULTS:The presence of a fluid-fluid level, a hypointense rim on T2-weighted images, septation, and an off-midline location were more common with pituitary adenomas, whereas the presence of an intracystic nodule was more common with Rathke cleft cysts. Multiple logistic regression analysis showed that cystic pituitary adenomas and Rathke cleft cysts can be distinguished on the basis of the presence of a fluid-fluid level, septation, an off-midline location, and the presence of an intracystic nodule (P = .006, .032, .001, and .023, respectively). Among 24 patients in the external validation population, 22 were classified correctly on the basis of the diagnostic tree model used in this study.CONCLUSIONS:A systematic approach using this diagnostic tree model can be helpful in distinguishing cystic pituitary adenomas from Rathke cleft cysts.

Pituitary adenoma is a benign neoplasm that arises from the adenohypophysis and is the most common intrasellar pathology, accounting for 10%–15% of all intracranial neoplasms.^1,2 Typical imaging findings of an uncomplicated pituitary adenoma include slow enhancement compared with that of the pituitary gland, lateral deviation of the infundibulum, and isointense signal intensity relative to gray matter on T1-weighted imaging.³ Intratumoral hemorrhage and ischemic infarction are common with larger pituitary adenomas, which may result in hemorrhagic or cystic changes or both, leading to various signal intensities on MR imaging.^4–8Rathke cleft cyst (RCC) is a benign epithelial cyst believed to originate from the remnants of the Rathke pouch.⁹ Typical imaging findings include a nonenhancing, noncalcified, intrasellar/suprasellar cyst with an intracystic nodule.^9–12 Depending on its cystic content and the presence of an associated intracystic nodule, an RCC may show various signal intensities on both T1- and T2-weighted images.^13–15 More specifically, T1 hyperintensity and T2 hypointensity of an RCC associated with a high intracystic protein content can mimic cystic pituitary adenoma with hemorrhage, which makes imaging diagnosis of a cystic pituitary adenoma or an RCC a challenge.Preoperative differentiation between a cystic pituitary adenoma and an RCC is important for treatment planning.^16–18 Partial resection of the wall and evacuation of cyst contents are sufficient for an RCC, whereas a cystic pituitary adenoma may require total resection, not only to relieve mass effect but also to correct hormone excess.^9,19–21 Unnecessary surgical excision of an RCC may lead to serious complications, such as CSF leaks, infection, and hypothalamic injury, though the incidences thereof are very low.^21,22 Thus, obtaining the correct preoperative diagnosis with which to determine the proper surgical indication and to plan the optimal surgical procedure is a major concern for neurosurgeons.⁹ To date, several characteristic MR imaging appearances of pituitary adenomas and RCCs have been reported,^{2,9,12,20,23–25} but there are some cases for which the diagnoses are inconclusive when 1 or 2 imaging findings are used, and none of the studies has systemically analyzed the MR imaging appearances of cystic pituitary adenomas to differentiate them from RCCs. Therefore, we evaluated the diagnostic potential of a multifactor analysis of MR imaging findings and developed a diagnostic tree model to increase the diagnostic accuracy in differentiating cystic pituitary adenomas and RCCs before surgery.