T2-weighted three-dimensional fast spin-echo MR in inflammatory peripheral facial nerve palsy.

PURPOSEOur objective was to identify histologically and intraoperatively verified focal nerve thickening of the distal intrameatal segment on three-dimensional fast spin-echo (FSE) T2-weighted MR images as a new diagnostic criterion in patients with inflammatory peripheral facial nerve palsy.METHODSTwenty-two patients with clinically diagnosed unilateral (n = 20) or bilateral (n = 2) inflammatory peripheral facial nerve palsy were examined on a 1.5-T MR imager using noncontrast and contrast-enhanced T1-weighted SE sequences and 3-D T2-weighted FSE sequences with secondary reformations. Abnormal contrast enhancement and possible focal nerve thickening of the distal intrameatal segment, labyrinthine nerve segment, and geniculate ganglion region were analyzed prospectively.RESULTSIn all patients, the T1-weighted postcontrast SE images showed characteristic smooth, linear, abnormally intense contrast enhancement of the distal intrameatal segment, indicating peripheral inflammatory nerve palsy. In 23 nerves (96%) a focal bulbous nerve thickening of the distal intrameatal segment was observed on 3-D T2-weighted FSE images. In 100% of patients with peripheral inflammatory facial nerve palsy, postcontrast T1-weighted SE images showed a smooth, linear, and abnormally intense contrast enhancement of the distal intrameatal segment; reformatted very thin 3-D T2-weighted FSE images showed a focal bulbous nerve thickening of the distal intrameatal segment in 96% of patients. These findings corresponded to intraoperative and histologic findings.CONCLUSIONThree-dimensional T2-weighted FSE sequences are fast and cheap compared with T1-weighted postcontrast images, but secondary reformations are time-consuming and require exact anatomic knowledge for careful analysis of the different nerve segments.     

Comparison of lumbar degenerative disc disease using conventional fast spin echo T2W MRI and T2 fast spin echo dixon sequences

Objectives:To compare the grading of lumbar degenerative disc disease (DDD), Modic end-plate changes (MEPC) and identification of high intensity zones (HIZ) on a combination of sagittal T₁weighted turbo spin echo (T₁W TSE), T₂weighted fast spin echo (T₂W FSE) and short tau inversion recovery (STIR) sequences (routine protocol) with a single sagittal T₂W FSE Dixon MRI sequence which provides in-phase, opposed-phase, water only and fat only images in a single acquisition (Dixon protocol).Methods:50 patients underwent lumbar spine MRI using the routine protocol with the addition of a T₂W FSE Dixon sequence. DDD grade, MEPC and HIZ for each disc level were assessed on the routine and Dixon protocols. Each protocol was reviewed independently by three readers (consultant musculoskeletal radiologists with 26-, 8- and 4 years’ experience), allowing assessment of inter-reader agreement and inter protocol agreement for each assessed variable.Results:The study included 17 males and 33 females (mean age 51 years; range 8–82 years). Inter-reader agreement for DDD grade on the routine protocol was 0.57 and for the Dixon protocol was 0.63 (p = 0.08). Inter-reader agreement for MEPC on the routine protocol was 0.45 and for the Dixon protocol was 0.53 (p = 0.02), and inter-reader agreement for identification of the HIZ on the routine protocol was 0.52 and for the Dixon protocol was 0.46 (p = 0.27). Intersequence agreement for DDD grade ranged from 0.61 to 0.97, for MEPC 0.46–0.62 and for HIZ 0.39–0.5.Conclusion:A single sagittal T₂W FSE Dixon MRI sequence could potentially replace the routine three sagittal sequence protocol for assessment of lumbar DDD, MEPC and HIZ resulting in ~60% time saving.Advances in knowledge:Grading of lumbar DDD, presence of Modic changes and high intensity zones were compared on sagittal T₁W TSE, T₂W FSE and STIR sequences with a T₂W FSE Dixon sequence, with fair-to-good correlation suggesting that three conventional sequences could be replaced by a single Dixon sequence.     

Contrast on T2-weighted images of the lumbar spine using fast spin-echo and gated conventional spin-echo sequences

A prospective study in 31 patients was designed to compare contrast quantitatively using axial conventional, gated spin-echo T2-weighted (T2W) (SE) (asymmetrical echo TE 30 and 80 ms) and axial dual-echo fast spin-echo (FSE) sequences (TE_eff20 and 120 ms) to image lumbar discs, nerve roots, and cerebrospinal fluid CSF. We used two quantitative measures, percent (%) contrast and contrast-to-noise ratio (CNR), to compare the sequences. The FSE sequence had greater % contrast and CNR on the first and second echo images for both disc and nerve root detection using these scan parameters. An axial FSE sequence, therefore, provided contrast characteristics similar to those of gated axial T2W SE sequence in the lumbar spine, with a 60% saving in acquisition time. The FSE sequence is now our standard axial T2W study for the lumbar spine.     

Spinal cord lesions in patients with multiple sclerosis: comparison of MR pulse sequences.

PURPOSETo compare T2-weighted conventional spin-echo (CSE), fast spin-echo (FSE), shorttau inversion recovery (STIR) FSE, and fluid-attenuated inversion recovery (FLAIR) FSE sequences in the assessment of cervical multiple sclerosis plaques.METHODSTwenty patients with clinically confirmed multiple sclerosis and signs of cervical cord involvement were examined on a 1.5-T MR system. Sagittal images of T2-weighted and proton density-weighted CSE sequences, T2-weighted FSE sequences with two different sets of sequence parameters, STIR-FSE sequences, and FLAIR-FSE sequences were compared by two independent observers. In addition, contrast-to-noise measurements were obtained.RESULTSSpinal multiple sclerosis plaques were seen best on STIR-FSE images, which yielded the highest lesion contrast. Among the T2-weighted sequences, the FSE technique provided better image quality than did the CSE technique, but lesion visibility was improved only with a repetition time/echo time of 2500/90; parameters of 3000/150 provided poor lesion contrast but the best myelographic effect and overall image quality. CSE images were degraded by prominent image noise; FLAIR-FSE images showed poor lesion contrast and strong cerebrospinal fluid pulsation artifacts.CONCLUSIONSThe STIR-FSE sequence is the best choice for assessment of spinal multiple sclerosis plaques. For T2-weighted FSE sequences, shorter echo times are advantageous for spinal cord imaging, long echo times are superior for extramedullary and extradural disease. FLAIR-FSE sequences do not contribute much to spinal imaging for multiple sclerosis detection.     

Improved Lesion Conspicuity with Contrast-Enhanced 3D T1 TSE Black-Blood Imaging in Cranial Neuritis: A Comparative Study of Contrast-Enhanced 3D T1 TSE, 3D T1 Fast-Spoiled Gradient Echo,and 3D T2 FLAIR

BACKGROUND AND PURPOSE:Contrast-enhanced 3D-turbo spin-echo (TSE) black-blood sequence has gained attention, as it suppresses signals from vessels and provides an increased contrast-noise ratio. The purpose was to investigate which among the contrast-enhanced 3D T1 TSE, 3D T1 fast-spoiled gradient echo (FSPGR), and 3D T2 FLAIR sequences can better detect cranial nerve contrast enhancement.MATERIALS AND METHODS:Patients with cranial neuritis based on clinical findings (n = 20) and control participants (n = 20) were retrospectively included in this study. All patients underwent 3T MR imaging with contrast-enhanced 3D T1 TSE, 3D T1 FSPGR, and 3D T2 FLAIR. Experienced and inexperienced reviewers independently evaluated the 3 sequences to compare their diagnostic performance and time required to reach the diagnosis. Additionally, tube phantoms containing varying concentrations of gadobutrol solution were scanned using the 3 sequences.RESULTS:For the inexperienced reader, the 3D T1 TSE sequence showed significantly higher sensitivity (80% versus 50%, P = .049; 80% versus 55%; P = .040), specificity (100% versus 65%, P = .004; 100% versus 60%; P = .001), and accuracy (90% versus 57.5%, P = .001; 90% versus 57.5%, P = .001) than the 3D T1 FSPGR and 3D T2 FLAIR sequences in patients with cranial neuritis. For the experienced reader, the 3D T1-based sequences showed significantly higher sensitivity than the 3D T2 FLAIR sequence (85% versus 30%, P < .001; 3D T1 TSE versus 3D T2 FLAIR, 85% versus 30%, P < .001; 3D T1 FSPGR versus 3D T2 FLAIR). For both readers, the 3D T1 TSE sequence showed the highest area under the curve (inexperienced reader; 0.91, experienced reader; 0.87), and time to diagnosis was significantly shorter with 3D T1 TSE than with 3D T1 FSPGR.CONCLUSIONS:The 3D T1 TSE sequence may be clinically useful in evaluating abnormal cranial nerve enhancement, especially for inexperienced readers.

Cranial neuropathies can have multiple causes, including infectious, neoplastic, inflammatory, traumatic, and idiopathic pathologies.¹ Such conditions cause disruption of the blood–nerve barrier, which is sustained by the combined actions of tight junctions in the endothelium of the endoneurial capillaries and of the inner layers of the perineurium.² Contrast-enhanced (CE) MR imaging plays an important role in the diagnosis of cranial neuritis by visualizing nerve enhancement attributed to leakage forcing spillage and accumulation of contrast material surrounded by CSF.³To date, no standard protocol has been established for evaluating cranial nerve enhancement, whereas several sequences have been proposed for detecting leptomeningeal enhancement. CE 3D T1 gradient-echo (GRE) sequences have been widely used in the clinical setting to detect leptomeningeal pathology.^4-7 Furthermore, the CE 3D FLAIR sequence is advantageous because it can sensitively detect low concentrations of gadolinium.^8,9 Recently, a CE 3D turbo spin-echo (TSE) black-blood sequence has gained attention because it provides an increased contrast to noise ratio (CNR) and suppresses diverting signals from vessels.^10-13To the best of our knowledge, no study has explored the value of CE 3D T1 TSE black-blood imaging in the diagnosis of cranial neuritis. Although the CE 3D T1 GRE sequence is generally used for the evaluation of cranial nerve enhancement,^3,14 its ability to evaluate the cisternal segment of cranial nerves is limited owing to the surrounding prominent vessel enhancement. Moreover, hyperintensities on FLAIR are also associated with various conditions, such as subarachnoid hemorrhage, sluggish collateral vessels, and supplemental oxygen, which may produce misinterpretations of the cranial nerve enhancement.¹⁵ Therefore, the aim of this study was to investigate which sequence among 3D T1 TSE, 3D T1 fast-spoiled gradient echo (FSPGR), and 3D T2 FLAIR can better detect contrast enhancement in patients with cranial neuritis.     

MR diagnosis of facial neuritis: diagnostic performance of contrast-enhanced 3D-FLAIR technique compared with contrast-enhanced 3D-T1-fast-field echo with fat suppression

BACKGROUND AND PURPOSE:Current MRI with the CE T1-weighted sequence plays a limited role in the evaluation of facial neuritis due to prominent normal facial nerve enhancement. Our purpose was to retrospectively investigate the usefulness of the CE 3D-FLAIR sequence compared with the CE 3D-T1-FFE sequence in facial neuritis patients.MATERIALS AND METHODS:We assessed 36 consecutive patients who underwent temporal bone MR imaging at 3T for idiopathic facial palsy. Two readers independently reviewed CE 3D-T1-FFE and CE 3D-FLAIR images to determine the degree of enhancement in each of 5 segments of the facial nerve. We compared AUCs using the Z-test, compared diagnostic performance of 2 MR techniques with the McNemar test, and evaluated interobserver agreement. The Pearson χ² test was used for each segment of the facial nerve.RESULTS:The AUC of CE 3D-FLAIR (reader 1, 0.754; reader 2, 0.746) was greater than that of CE 3D-T1-FFE (reader 1, 0.624; reader 2, 0.640; P < .001). The diagnostic sensitivities, specificities, and accuracies were 97.2%, 86.1%, and 91.7%, respectively, for CE 3D-FLAIR, and 100%, 56.9%, and 78.5%, respectively, for CE 3D-T1-FFE. The specificity and accuracy of CE 3D-FLAIR were greater than those of CE 3D-T1-FFE (specificity, P = .029; accuracy, P = .008). The interobserver agreements for CE 3D-FLAIR (κ-value, 0.831) and CE 3D-T1-FFE (κ-value, 0.694) were excellent. Enhancement of the canalicular and anterior genu segments on CE 3D-FLAIR were significantly correlated with the occurrence of facial neuritis (P < .001 for canalicular; P = .032 and 0.020 for anterior genu by reader 1 and reader 2, respectively).CONCLUSIONS:CE 3D-FLAIR can improve the specificity and overall accuracy of MR imaging in patients with idiopathic facial palsy.

MR imaging of patients with facial neuritis is usually not indicated except for patients with facial palsy who have atypical manifestations and those with intractable palsy despite therapy. In most patients, the diagnosis of facial neuritis is clinically evident and EPS confirms this. EPS can also provide prognostic information on outcomes in patients with acute facial palsy. However, the major disadvantage of EPS is its inability to detect diagnostic abnormalies of the nerve distal to the stylomastoid foramen within 1 week of symptom onset.¹Although the potential of MR imaging has been studied as part of the effort to find other helpful diagnostic techniques over the past 20 years,^2–10 its results have been largely disappointing. Gd-DTPA-enhanced T1-weighted spin-echo and 3D spoiled gradient-echo sequences have shown significant limitations in diagnosing and predicting outcomes in patients with facial neuritis; the geniculate ganglion, tympanic, or mastoid segment of the normal facial nerve can be significantly enhanced in up to 76% of patients due to the distribution of arteriovenous plexus along the facial nerve, which, in turn, may inhibit evaluation of the pathologic enhancement of the nerves resulting from breakdown of the blood nerve barrier.^10–12 Thus, MR imaging plays a limited role in the diagnosis and provision of prognostic information of facial neuritis.^3,7Recently, a new isotropic 3D-T2-weighted imaging technique, the 3D turbo spin-echo sequence with variable flip angles (VISTA, sampling perfection with application optimized contrast using different flip angle evolution [SPACE], or Cube), was introduced on the 3T MR system.¹³ This sequence uses variable refocusing flip angles to constrain T2 decay over a long echo train, with minimal blurring, and can acquire isotropic resolutions in a clinically acceptable scan time. When applied to the temporal bone pathologies, this 3D-FLAIR sequence had higher SNR and CNR than previous 2D sequences.^14,15 Moreover, the 3D-FLAIR sequence has been shown useful in the diagnosis of mumps-related deafness and sudden sensorineural hearing loss, and for predicting the prognosis of patients with sudden sensorineural hearing loss, which is not usually demonstrated by the conventional MR imaging sequences.^16–18 This ability of the 3D-FLAIR sequence to find minute abnormalities mainly results from the high sensitivity of FLAIR imaging to subtle changes of longitudinal magnetization in the fluid space, which declines with the higher concentration of the contrast agent, different from T1-weighted images.^19,20 The 3D-FLAIR sequence is also known to suppress the signal intensity from the flowing fluid at a velocity exceeding 1.0 cm/s.²¹ With this background information, we retrospectively evaluated 3D-FLAIR images in 20 subjects with normal facial nerve function and found that only 1 subject showed mild enhancement of the anterior genu segment. From the preliminary study, we hypothesized that the pathologic enhancement of facial neuritis may be more accurately imaged on 3D-FLAIR images than on T1-FFE images, without normal enhancement of the arteriovenous plexus along the facial nerve.Therefore, the purpose of this study was to investigate the diagnostic performance of CE 3D-FLAIR images compared with CE 3D-T1-FFE images in patients with facial neuritis.     

Idiopathic,herpetic, and HIV-associated facial nerve palsies: abnormal MR enhancement patterns.

PURPOSETo determine specific criteria that can be used to define normal versus abnormal MR contrast enhancement of the facial nerve.METHODSTwenty-three patients with acute unilateral inflammatory peripheral facial nerve palsy were examined on a 1.5-T MR using multiplanar T1-weighted spin-echo sequences before and after injection of gadopentetate dimeglumine. These MR patterns were compared with those of healthy control subjects.RESULTSThe normal facial nerve usually showed a mild to moderate enhancement of the geniculate ganglion and the tympanic-mastoid segment. The intracanalicular-labyrinthine segment did not enhance. All patients showed abnormal enhancement of the distal intracanalicular and the labyrinthine segment. An intense enhancement could be observed in the geniculate ganglion and the proximal tympanic segment, especially in herpetic palsy. Associated enhancement of the vestibulocochlear nerve was seen in herpetic and idiopathic palsy. Enhancement of the inner ear structures was detected only in herpetic palsy.CONCLUSIONSAbnormal contrast enhancement of the distal intracanalicular and the labyrinthine facial nerve segment is observed in all patients and is the only diagnostically reliable MR feature proving an inflammatory facial nerve lesion. The intense enhancement of the geniculate ganglion and the proximal tympanic segment is possibly correlated with the reactivation of the latent infection in the sensory ganglion. The abnormal enhancement results from breakdown of the blood-peripheral nerve barrier and/or from venous congestion in the venous plexuses of the epi- and perineurium.     

MR evaluation of vertebral metastases: T1-weighted,short-inversion-time inversion recovery,fast spin-echo,and inversion-recovery fast spin-echo sequences.

PURPOSETo compare the detectability of vertebral metastatic disease on T1-weighted, short-inversion-time inversion recovery (STIR), fast spin-echo (FSE), fat-saturated FSE, and inversion recovery FSE (IRFSE) MR sequences using percent contrast and contrast-to-noise ratios.METHODSPatients with proved metastatic disease underwent imaging on a 1.5-T MR system with sagittal T1-weighted (800/20/2 [repetition time/echo time/excitations]) (91 patients), STIR (1400/43/2; inversion time, 140) (91 patients), FSE (4000/180/2) (46 patients), fat-saturated FSE (4000/180/2) (16 patients), and IRFSE (29 patients) sequences. Percent contrast and contrast-to-noise ratio were calculated for the lesions. The number of metastatic lesions detected with each of the pulse sequences was also calculated.RESULTSMean percent contrast was, for T1-weighted sequence, -42.2 +/- 1%; STIR, 262 +/- 34%; FSE, 121 +/- 21%; fat-saturated FSE, 182 +/- 6%; and IRFSE, 272 +/- 47%. The mean contrast-to-noise ratio for T1-weighted was -4.63 +/- 1.7; STIR, 10.8 +/- .98; FSE, 4.16 +/- .76; fat-saturated FSE, 4.87 +/- .19; and IRFSE, 5.2 +/- .87. STIR and IRFSE showed the highest number of lesions, followed by T1-weighted, fat-saturated FSE, and FSE sequences. T1-weighted sequences showed 94%, FSE 55%, and fat-saturated FSE 78% of the lesions detected. Epidural metastatic lesions were better depicted on T1-weighted, FSE, and fat-saturated FSE sequences.CONCLUSIONSTIR was superior to both T1-weighted and FSE (with and without fat saturation) for detection of metastatic lesions, in terms of both percent contrast and contrast-to-noise ratio and visibility. IRFSE was equal to STIR for the detection of metastasis by both subjective and objective criteria. T1-weighted, FSE, and fat-saturated FSE sequences were superior to STIR and IRFSE in the detection of epidural metastatic disease. IRFSE provided faster scanning time, which could be translated into greater resolution.     

Impact of motion on T1 mapping acquired with inversion recovery fast spin echo and rapid spoiled gradient recalled‐echo pulse sequences for delayed gadolinium‐enhanced MRI of cartilage (dGEMRIC) in volunteers

Purpose:

To evaluate the impact of motion on T1 values acquired by using either inversion‐recovery fast spin echo (IR‐FSE) or three‐dimensional (3D) spoiled gradient recalled‐echo (SPGR) sequences for delayed gadolinium‐enhanced magnetic resonance imaging of cartilage (dGEMRIC) in volunteers.

Materials and Methods:

Single‐slice IR‐FSE and 3D SPGR sequences were applied to perform dGEMRIC in five healthy volunteers. A mutual information‐based approach was used to correct for image misregistration. Displacements were expressed as averaged Euclidean distances and angles. Averages of differences in goodness of fit (Δχ²) tests and averages of relative differences in T1 values (ΔT1) before and after motion correction were computed.

Results:

Maximum Euclidean distance was 3.5 mm and 1.2 mm for IR‐FSE and SPGR respectively. Mean ± SD of Δχ² were 10.18 ± 8.4 for IR‐FSE and ?1.37 ± 5.5 for SPGR. Mean ± SD of ΔT1 were 0.008 ± 0.0048 for IR‐FSE and ?0.002 ± 0.019 for FSPGR. Pairwise comparison of Δχ² values showed a significant difference for IR‐FSE, but not for 3D‐SPGR. Significantly greater variability in T1 values was also noted for IR‐FSE than for 3D‐SPGR.

Conclusion:

Involuntary motion has a significant influence on T1 values acquired with IR‐FSE, but not with 3D‐SPGR in healthy volunteers. J. Magn. Reson. Imaging 2010;32:394–398. © 2010 Wiley‐Liss, Inc.

     

High-resolution proton density weighted three-dimensional fast spin echo (3D-FSE) of the knee with IDEAL at 1.5 Tesla: comparison with 3D-FSE and 2D-FSE--initial experience

Purpose:

To assess the feasibility of combining three‐dimensional fast spin echo (3D‐FSE) and Iterative‐decomposition‐of water‐and‐fat‐with‐echo asymmetry‐and‐least‐squares‐estimation (IDEAL) at 1.5 Tesla (T), generating a high‐resolution 3D isotropic proton density‐weighted image set with and without “fat‐suppression” (FS) in a single acquisition, and to compare with 2D‐FSE and 3D‐FSE (without IDEAL).

Materials and Methods:

Ten asymptomatic volunteers prospectively underwent sagittal 3D‐FSE‐IDEAL, 3D‐FSE, and 2D‐FSE sequences at 1.5T (slice thickness [ST]: 0.8 mm, 0.8 mm, and 3.5 mm, respectively). 3D‐FSE and 2D‐FSE were repeated with frequency‐selective FS. Fluid, cartilage, and muscle signal‐to‐noise ratio (SNR) and fluid‐cartilage contrast‐to‐noise ratio (CNR) were compared among sequences. Three blinded reviewers independently scored quality of menisci/cartilage depiction for all sequences. “Fat‐suppression” was qualitatively scored and compared among sequences.

Results:

3D‐FSE‐IDEAL fluid‐cartilage CNR was higher than in 2D‐FSE (P < 0.05), not different from 3D‐FSE (P = 0.31). There was no significant difference in fluid SNR among sequences. 2D‐FSE cartilage SNR was higher than in 3D FSE‐IDEAL (P < 0.05), not different to 3D‐FSE (P = 0.059). 2D‐FSE muscle SNR was higher than in 3D‐FSE‐IDEAL (P < 0.05) and 3D‐FSE (P < 0.05). Good or excellent depiction of menisci/cartilage was achieved using 3D‐FSE‐IDEAL in the acquired sagittal and reformatted planes. Excellent, homogeneous “fat‐suppression” was achieved using 3D‐FSE‐IDEAL, superior to FS‐3D‐FSE and FS‐2D‐FSE (P < 0.05).

Conclusion:

3D FSE‐IDEAL is a feasible approach to acquire multiplanar images of diagnostic quality, both with and without homogeneous “fat‐suppression” from a single acquisition. J. Magn. Reson. Imaging 2012;361‐369. © 2011 Wiley Periodicals, Inc.     

Enhancement pattern of the normal facial nerve at 3.0 T temporal MRI

The purpose of this study was to evaluate the enhancement pattern of the normal facial nerve at 3.0 T temporal MRI. We reviewed the medical records of 20 patients and evaluated 40 clinically normal facial nerves demonstrated by 3.0 T temporal MRI. The grade of enhancement of the facial nerve was visually scaled from 0 to 3. The patients comprised 11 men and 9 women, and the mean age was 39.7 years. The reasons for the MRI were sudden hearing loss (11 patients), Méniàre''s disease (6) and tinnitus (7). Temporal MR scans were obtained by fluid-attenuated inversion-recovery (FLAIR) and diffusion-weighted imaging of the brain; three-dimensional (3D) fast imaging employing steady-state acquisition (FIESTA) images of the temporal bone with a 0.77 mm thickness, and pre-contrast and contrast-enhanced 3D spoiled gradient record acquisition in the steady state (SPGR) of the temporal bone with a 1 mm thickness, were obtained with 3.0 T MR scanning. 40 nerves (100%) were visibly enhanced along at least one segment of the facial nerve. The enhanced segments included the geniculate ganglion (77.5%), tympanic segment (37.5%) and mastoid segment (100%). Even the facial nerve in the internal auditory canal (15%) and labyrinthine segments (5%) showed mild enhancement. The use of high-resolution, high signal-to-noise ratio (with 3 T MRI), thin-section contrast-enhanced 3D SPGR sequences showed enhancement of the normal facial nerve along the whole course of the nerve; however, only mild enhancement was observed in areas associated with acute neuritis, namely the canalicular and labyrinthine segment. Imaging of the facial nerve is useful for the evaluation of pathological conditions. MRI of the facial nerve is usually performed selectively in cases of peripheral facial nerve palsy in patients with an atypical presentation or delayed recovery to exclude space-occupying lesions. The gadolinium-diethylene triamine pentaacetic acid (Gd-DTPA) contrast pulse sequence is the most informative MRI procedure for evaluation of facial nerve pathology [1]. Although many studies involving MRI of normal and paralysed facial nerves have been performed [2–10], there are no reports on the enhancement pattern of normal and abnormal facial nerves with 3.0 T MR scanning. The 3.0 T MR scan provides a higher signal-to-noise ratio (SNR), which allows a higher imaging matrix, thinner slices and a shorter time for scanning [11].The purpose of this retrospective study was to evaluate the enhancement pattern of normal facial nerves, bilaterally, with 3.0 T temporal MRI.     

High-resolution depiction of the cranial nerves in the posterior fossa (N III–N XII) with 2D fast spin echo and 3D gradient echo sequences at 3.0 T

PurposeThe objective of this study was to evaluate the influence of high-resolution imaging obtainable with the higher field strength of 3.0 T on the visualization of the brain nerves in the posterior fossa by using T₂-weighted fast spin echo (FSE) and fast imaging employing steady-state gradient echo (GRE) sequences as the most suitable techniques to visualize each of the cranial nerves.Materials and methodsIn total, 20 nerves were investigated on MR images of 12 volunteers each and selected for comparison, respectively, with the FSE sequences with 5-mm and 2-mm section thicknesses and GRE sequences acquired with a 3.0-T scanner and a quadrature head coil. The resulting MR images were evaluated by three independent readers who rated image quality according to depiction of anatomic detail and contrast with use of a rating scale.ResultsIn general, decrease of the slice thickness showed a significant increase in the detection of nerves as well as in the image quality characteristics. As expected, artifacts were prominent in high-field imaging of the posterior fossa with GRE sequences. Nevertheless, comparing FSE and GRE imaging, the course of brain nerves and brainstem vessels was visualized best with use of the three-dimensional (3D) pulse sequence, although with respect to structural identification and contrast according to the rating scale, observer scores were not significantly improved.ConclusionThe comparison revealed the clear advantage of a thin section. The increased resolution enabled immediate identification of all brainstem nerves. Although image quality is impaired at GRE at high field strength, this sequence most distinctly and confidently depicted pertinent structures and enables 3D reconstruction in order to illustrate complex relations of the brainstem.     

Spatial relationship between vestibular schwannoma and facial nerve on three-dimensional T2-weighted fast spin-echo MR images

BACKGROUND AND PURPOSE: During surgical removal of a vestibular schwannoma, correct identification of the facial nerve is necessary for its preservation and continuing function. We prospectively analyzed the spatial relationship between vestibular schwannomas and the facial nerve using 3D T2-weighted and postcontrast T1-weighted spin-echo (SE) MR imaging. METHODS: Twenty-two patients with a unilateral vestibular schwannoma were examined with MR imaging. The position and spatial relationship of the facial nerve to adjacent tumor within the internal auditory canal (IAC) and cerebellopontine angle cistern (CPA) were assessed on multiplanar reformatted 3D T2-weighted fast spin-echo (FSE) images and on postcontrast transverse and coronal T1-weighted SE images. The entrance of the nerve into the bony canal at the meatal foramen and the nerve root exit zone along the brain stem were used as landmarks to follow the nerve course proximally and distally on all images. RESULTS: The spatial relationship between vestibular schwannoma and facial nerve could not be detected on postcontrast T1-weighted SE images. In 86% of the patients, the position of the nerve in relation to the tumor was discernible on multiplanar reformatted 3D T2-weighted FSE images. In tumors with a maximal diameter up to 10 mm, the entire nerve course was visible; in tumors with a diameter of 11 to 24 mm, only segments of the facial nerve were visible; and in tumors larger than 25 mm, the facial nerve could not be seen, owing to focal nerve thinning and obliteration of landmarks within the IAC and CPA. CONCLUSION: Identification of the facial nerve and its position relative to an adjacent vestibular schwannoma is possible on multiplanar reformatted 3D T2-weighted FSE images but not on postcontrast T1-weighted SE images. Detection of this spatial relationship depends on the tumor's size and location.     

Comparison of Gd-DTPA-induced signal enhancements in rat brain C6 glioma among different pulse sequences in 3-Tesla magnetic resonance imaging

Background: T1-shortening contrast media are routinely used in magnetic resonance (MR) examinations for the diagnosis of brain tumors. Although some studies show a benefit of 3 Tesla (T) compared to 1.5T in delineation of brain tumors using contrast media, it is unclear which pulse sequences are optimal.

Purpose: To compare gadopentetate dimeglumine (Gd-DTPA)-induced signal enhancements in rat brain C6 glioma in the thalamus region among different pulse sequences in 3T MR imaging.

Material and Methods: Five rats with a surgically implanted C6 glioma in their thalamus were examined. T1-weighted brain images of the five rats were acquired before and after Gd-DTPA administration (0.1 mmol/kg) using three clinically available pulse sequences (spin echo [SE], fast SE [FSE], fast spoiled gradient echo [FSPGR]) at 3T. Signal enhancement in the glioma (E_T) was calculated as the signal intensity after Gd-DTPA administration scaled by that before administration. Pulse sequences were compared using the Tukey-Kramer test.

Results: E_T was 1.12±0.05 for FSE, 1.26±0.11 for FSPGR, and 1.20±0.11 for SE. FSPGR showed significantly higher signal enhancement than FSE and comparable enhancement to SE.

Conclusion: FSPGR is superior to FSE and comparable to SE in its ability to delineate rat brain C6 glioma in the thalamus region.     

High-Resolution MRI of the Intraparotid Facial Nerve Based on a Microsurface Coil and a 3D Reversed Fast Imaging with Steady-State Precession DWI Sequence at 3T

BACKGROUND AND PURPOSE:3D high-resolution MR imaging can provide reliable information for defining the exact relationships between the intraparotid facial nerve and adjacent structures. The purpose of this study was to explore the clinical value of using a surface coil combined with a 3D-PSIF-DWI sequence in intraparotid facial nerve imaging.MATERIALS AND METHODS:Twenty-one healthy volunteers underwent intraparotid facial nerve scanning at 3T by using the 3D-PSIF-DWI sequence with both the surface coil and the head coil. Source images were processed with MIP and MPR to better delineate the intraparotid facial nerve and its branches. In addition, the SIR of the facial nerve and parotid gland was calculated. The number of facial nerve branches displayed by these 2 methods was calculated and compared.RESULTS:The display rates of the main trunk, divisions (cervicofacial, temporofacial), and secondary branches of the intraparotid facial nerve were 100%, 97.6%, and 51.4% by head coil and 100%, 100%, and 83.8% by surface coil, respectively. The display rate of secondary branches of the intraparotid facial nerve by these 2 methods was significantly different (P < .05). The SIRs of the intraparotid facial nerve/parotid gland in these 2 methods were significantly different (P < .05) at 1.37 ± 1.06 and 1.89 ± 0.87, respectively.CONCLUSIONS:The 3D-PSIF-DWI sequence combined with a surface coil can better delineate the intraparotid facial nerve and its divisions than when it is combined with a head coil, providing better image contrast and resolution. The proposed protocol offers a potentially useful noninvasive imaging sequence for intraparotid facial nerve imaging at 3T.

3D high-resolution MR imaging can provide reliable information for depicting normal intraparotid facial nerve anatomy and defining the exact relationship of the intraparotid facial nerve and adjacent structures; this information could assist in the planning of parotid tumor surgery.¹ Imaging the intraparotid course of the facial nerve is a challenge due to the fine structure and complex anatomy of the nerve.^1–4 With recent advances in MR imaging technology, especially the use of surface coils combined with 3D high-resolution MR imaging technology, increased attention has been directed to intraparotid facial nerve imaging.^1–4 The inherent resolution of a surface coil itself is significantly better than that of a head coil, ensuring high-quality imaging for fine structures, particularly in superficial organs such as the parotid gland or eye.^1,5 Recently, 3D high-resolution sequences such as 3D gradient-recalled acquisition in the steady state sequence and 3D FIESTA have been applied to intraparotid facial nerve imaging.^2–4 These sequences rely mainly on the fat within the parotid gland as a high signal background to show the facial nerve because both the intraparotid facial nerve and the parotid duct are visualized as linear structures of low intensity.^2–4 In another report, the intraparotid facial nerve showed low signal compared with the high intensity of the parotid duct by using a balanced turbo-field echo, thus avoiding confusion between these 2 structures; however, no volumetric images were obtained,⁶ and MPR or curved planar reconstruction was not available. Thus, although there are several MR imaging sequences that can delineate the intraparotid facial nerve and parotid duct, limitations remain. The aim of this study was to explore the capabilities of simultaneously displaying the intraparotid facial nerve and parotid duct by using a surface coil combined with 3D-PSIF-DWI on a 3T MR imaging scanner.     

Assessment of bone marrow oedema-like lesions using MRI in patellofemoral knee osteoarthritis: comparison of different MRI pulse sequences

Objective:To compare bone marrow oedema-like lesion (BML) volume in subjects with symptomatic patellofemoral (PF) knee osteoarthritis (OA) using four different MRI sequences and to determine reliability of BML volume assessment using these sequences and their correlation with pain.Methods:76 males and females (mean age 55.8 years) with symptomatic patellofemoral knee OA had 1.5 T MRI scans. PD fat suppressed (FS), STIR, contrast-enhanced (CE) T₁W FS, and 3D T₁W fast field echo (FFE) sequences were obtained. All sequences were assessed by one reader, including repeat assessment of 15 knees using manual segmentation and the measurements were compared. We used random-effects panel linear regression to look for differences in the log-transformed BML volume (due to positive skew in the BML volume distribution) between sequences and to determine associations between BML volumes and knee pain.Results:58 subjects had PF BMLs present on at least one sequence. Median BML volume measured using T₁W FFE sequence was significantly smaller (224.7 mm³, interquartile range [IQR] 82.50–607.95) than the other three sequences. BML volume was greatest on the CE sequence (1129.8 mm³, IQR 467.28–3166.02). Compared to CE sequence, BML volumes were slightly lower when assessed using PDFS (proportional difference = 0.79; 95% confidence interval [CI] 0.62, 1.01) and STIR sequences (proportional difference = 0.85; 95% CI 0.67, 1.08). There were strong correlations between BML volume on PDFS, STIR, and CE T₁W FS sequences (ρs = 0.98). Correlations were lower between these three sequences and T₁W FFE (ρs = 0.80–0.81). Intraclass correlation coefficients were excellent for proton density fat-suppressed, short-tau inversion recovery, and CE T₁W FS sequences (0.991–0.995), while the ICC for T₁W FFE was good at 0.88. We found no significant association between BML volumes assessed using any of the sequences and knee pain.Conclusion:T₁W FFE sequences were less reliable and measured considerably smaller BML volume compared to other sequences. BML volume was larger when assessed using the contrast enhanced T₁W FS though not statistically significantly different from BMLs when assessed using PDFS and STIR sequences.Advances in knowledge:This is the first study to assess BMLs by four different MRI pulse sequences on the same data set, including different fluid sensitive sequences and gradient echo type sequence.     

关节软骨损伤MR成像序列的实验研究

目的 评价关节软骨缺损检查的各种MRI扫描序列。材料与方法 选用猪膝关节10只，制成宽度不等，深度为软骨全层的小槽状软骨缺损，MRI序列包括T1加权自旋回波序列（SE-T1），质子和T2加权快速自旋双回波序列（FSE-PD/T2），附加脂肪抑制的质子和T2加权快速自旋双回波序列（FS-FSE-PD/T2），附加脂肪抑制的三维快速扰相梯度回波序列（FS-3D-SPGR），液体衰减反转恢复序列（FLAIR），短TI翻转回波序列（STIR）和T1加权反转恢复序列（IR-TI700）。结果 与常规膝关节检查的FSE-PD/T2序列比较，FS-FSE-PD/T2能够分辨软骨与软骨下骨的界限，可测量软骨缺损厚度和深度；FS-3D-SPGR的软骨信噪比（SNR）和其对软骨下骨，关节液等关节软骨周围组织的对比噪声比（CNR）最高；IR-TI700测量的软骨缺损宽度和深度，与实际测量值的一致性最好，FLAIR和STIR不能清楚分辨软骨和软骨下骨的界限。结论 FS-FSE-PD/T2应作为膝关节检查的常规序列；三维抑脂梯度回波序列仍为关节软骨检查的最佳扫描序列。翻转回波扫描序列在关节软骨检查方面具有潜在的临床价值。     

Imaging sequences for intraoperative MR-guided laparoscopic liver resection in 1.0-T high field open MRI

The aim of this study was to identify suitable interactive (dynamic) magnetic resonance (MR) sequences for real-time MR-guided liver dissection in a 1.0-T high field open MRI system. Four dynamic sequences encompassing balanced steady state free precession (bSSFP), T1W gradient echo (GRE), T2W GRE and T2W fast spin echo (FSE) were analysed regarding the image quality, artefact susceptibility and the performance of SNR and CNR. The T2W FSE sequence (1.5 s/image) was considered superior because of an intraoperative SNR of 6.9 (±0.7) and CNR (vessel to parenchyma) of 5.6 (±1.7) in the interventional setting. As a proof of concept, MR-guided laparoscopic liver resection was performed in two healthy domestic pigs by using the T2W FSE sequence. The additional MR images offered simultaneous multiplanar real-time visualisation of the liver vessels during the intervention and thereby increased the anatomical orientation of the surgeon.     

Brain MR post-gadolinium contrast in multiple sclerosis: the role of magnetization transfer and image subtraction in detecting more enhancing lesions

Our purpose was to evaluate the role of magnetization transfer and image subtraction in detecting more enhancing lesions in brain MR imaging of patients with multiple sclerosis (MS). Thirty-one MS patients underwent MR imaging of the brain with T1-weighted spin echo sequences without and with magnetization transfer (MT) using a 1.5 T imager. Both sequences were acquired before and after intravenous injection of a paramagnetic contrast agent. Subtraction images in T1-weighted sequences were obtained by subtracting the pre-contrast images from the post-contrast ones. A significant difference was found between the numbers of enhanced areas in post-gadolinium T1-weighted images without and with MT (p=0.020). The post-gadolinium T1-weighted images with MT allowed the detection of an increased (13) number of enhancing lesions compared with post-gadolinium T1-weighted images without MT. A significant difference was also found between the numbers of enhanced areas in post-gadolinium T1-weighted images without MT and subtraction images without MT (p=0.020). The subtraction images without MT allowed the detection of an increased (10) number of enhancing lesions compared with post-gadolinium T1-weighted images without MT. Magnetization transfer contrast and subtraction techniques appear to be the simplest and least time-consuming applications to improve the conspicuity and detection of contrast-enhancing lesions in patients with MS.     

Visualization of cranial nerves I–XII: value of 3D CISS and T2-weighted FSE sequences

The aim of this study was to evaluate the sensitivity of the three-dimensional constructive interference of steady state (3D CISS) sequence (slice thickness 0.7 mm) and that of the T2-weighted fast spin echo (T2-weighted FSE) sequence (slice thickness 3 mm) for the visualization of all cranial nerves in their cisternal course. Twenty healthy volunteers were examined using the T2-weighted FSE and the 3D CISS sequences. Three observers evaluated independently the cranial nerves NI–NXII in their cisternal course. The rates for successful visualization of each nerve for 3D CISS (and for T2-weighted FSE in parentheses) were as follows: NI, NII, NV, NVII, NVIII 40 of 40 (40 of 40), NIII 40 of 40 (18 of 40), NIV 19 of 40 (3 of 40), NVI 39 of 40 (5 of 40), NIX, X, XI 40 of 40 (29 of 40), and NXII 40 of 40 (4 of 40). Most of the cranial nerves can be reliably assessed when using the 3D CISS and the T2-weighted FSE sequences. Increasing the spatial resolution when using the 3D CISS sequence increases the reliability of the identification of the cranial nerves NIII–NXII. Received: 29 September 1999; Revised: 2 February 2000; Accepted: 21 March 2000