Head and neck paragangliomas: value of contrast-enhanced 3D MR angiography

BACKGROUND AND PURPOSE: A rapid and accurate MR imaging technique would be beneficial to assess paragangliomas in the head and neck and to distinguish them from other lesions. The purpose of this study was to determine whether the combination of elliptic centric contrast-enhanced MR angiography (CE-MRA) and unenhanced and enhanced spin-echo imaging (conventional MR imaging) is more accurate than conventional MR imaging alone to assess paragangliomas in the head and neck.MATERIALS AND METHODS: Three radiologists retrospectively and independently reviewed CE-MRA and conventional MR imaging in 27 patients with suspected paragangliomas. The overall image quality and the probability of paraganglioma were recorded. The results of each technique and their combination were analyzed for sensitivity and specificity. Receiver operating characteristic (ROC) analyses were performed by using histologic analysis, imaging, and/or clinical findings as the reference standard.RESULTS: Forty-six lesions were found in 27 patients. In the assessment of paragangliomas, the combination of conventional MR imaging and CE-MRA was significantly superior to conventional MR imaging alone. Sensitivity and specificity respectively were the following: for CE-MRA, 100% and 94%; and for conventional MR imaging, 94% and 41%. The specificity of CE-MRA was significantly higher than that of conventional MR imaging (P = .004). There was good-to-excellent interobserver agreement for the paraganglioma probability with CE-MRA (nonweighted κ, 0.67–0.77), whereas there was fair-to-good interobserver agreement with conventional MR imaging (nonweighted κ, 0.50–0.65).CONCLUSION: In combination with conventional MR imaging, CE-MRA yields an excellent diagnostic value for the assessment of head and neck paragangliomas; hence, the 2 techniques should be regarded as complementary.

In the head and neck, paragangliomas are slow-growing hypervascular lesions that are most commonly located in 4 main sites: the carotid bifurcation, the foramen jugulare, the middle ear cavity, and along the cervical portion of the vagus nerve.¹ These lesions occur in both sporadic and hereditary forms (7% of cases). Multicentricity occurs in 10% of sporadic paragangliomas and in 30%–40% of familial paragangliomas.Imaging techniques are used for suspected head and neck paragangliomas to confirm this diagnosis.² Accurate assessment of tumor margins and invasion of adjacent structures are also essential for proper staging and therapy.³ For this task, MR imaging using unenhanced and enhanced fat-suppressed spin-echo (SE) sequences is widely accepted as the method of choice,^4,5 in addition to high-resolution CT,^6,7 in particular when the skull base is involved. Nonetheless, SE MR imaging has several limitations, particularly its sensitivity to artifacts.⁸ Moreover, the differentiation from other tumors and inflammatory lesions remains problematic. For example, the results of SE imaging are often equivocal when processes in the area of the jugular foramen are suspected.^9,10 Somatostatin receptor scintigraphy (SRS) may be useful in this situation but is not always conclusive. Digital subtraction angiography (DSA) is the current imaging reference standard for assessing the vascular architecture of the tumor before embolic therapy, but this method is invasive with a complication rate of 0.5%–1%,¹¹ which is too high for a diagnostic examination. Consequently, some investigators have discussed the utility of more specific methods in MR imaging to differentiate paragangliomas from other tumors or vascular abnormalities (dynamic MR imaging,¹² high-dose gadodiamide-injection dynamic MR imaging,¹³ or arterial and venous MR angiography [MRA]⁹).To our knowledge, the elliptical centric contrast-enhanced MRA (CE-MRA) sequence has not been assessed for visualizing paragangliomas and differentiating them from other lesions. We postulated that CE-MRA has the potential to simplify the interpretation of conventional MR imaging because intense tumor blush on CE-MRA may be a sensitive and specific feature for paragangliomas.The purpose of this study was to determine whether the combination of CE-MRA and conventional MR imaging is more accurate than conventional MR imaging alone to assess patients with suspected paragangliomas.     

Head and neck haemangiomas: contrast-enhanced three-dimensional MR angiography

We evaluated the clinical effectiveness of contrast-enhanced three-dimensional (3D) magnetic resonance angiography (MRA) for diagnosing head and neck haemangiomas. We studied six patients using a magnetization prepared rapid acquisition gradient-echo (MP-RAGE) sequence on a 1.5-T system. Conventional T1- and T2-weighted and contrast-enhanced images were also obtained. The images were compared with histological findings. In four cavernous haemangiomas, a mass was partially visible as an enhancing lesion on the early phase of MRA, and was completely visible as a larger enhancing lesion in the late phase, showing slow blood flow. In two capillary haemangiomas, a mass was completely visible in the early phase showing fast flow. In all patients, MRA clearly showed both the haemangiomas and the external carotid artery branches. MRA allowed assessment of the relationship between the haemangiomas and the feeding arteries, and of the haemodynamics. Received: 17 April 1998 Accepted: 5 June 1998     

The value of MR angiography techniques in the detection of head and neck paragangliomas

OBJECTIVE: The objective of this study was to compare three-dimensional phase-contrast angiography (3D PCA), 2D time-of-flight (2D TOF), and 3D TOF magnetic resonance (MR) angiography and a proton density weighted technique in terms of their ability to detect head and neck paragangliomas. MATERIALS AND METHODS: 14 patients with 29 paragangliomas were examined at 1.5 T. Three MR angiography sequences (3D PCA, 2D TOF, and multi-slab 3D TOF) and a proton density (PD) weighted sequence were reviewed by four neuroradiologists. The gold standard was digital subtraction angiography. Presence of tumor was assessed in five grades of confidence. Sensitivity and specificity were calculated after dichotomizing the results. Data was analyzed using the logistic regression method. RESULTS: Mean sensitivity and specificity for the four observers were for PD: 72%/97%, for 3D PCA: 75%/90%, for 2D TOF: 66%/93%, and for 3D TOF: 90%/92%. Sensitivity was significantly better for 3D TOF MRA (P < 0.001). No substantial between-observer variation for tumor detection was present. CONCLUSION: Our results demonstrate that, using 3D TOF MRA, paragangliomas in the head and neck region can be detected with high sensitivity and specificity. Further investigation is necessary to judge the value of 3D TOF MR angiography against fat suppressed contrast enhanced T1 weighted and fat suppressed T2 weighted MR sequences to find the optimal imaging sequence for paragangliomas.     

Follow-up of coiled cerebral aneurysms at 3T: comparison of 3D time-of-flight MR angiography and contrast-enhanced MR angiography

BACKGROUND AND PURPOSE: Our aim was to compare contrast-enhanced MR angiography (CE-MRA) and 3D time-of-flight (TOF) MRA at 3T for follow-up of coiled cerebral aneurysms.MATERIALS AND METHODS: Fifty-two patients treated with Guglielmi detachable coils for 54 cerebral aneurysms were evaluated at 3T MRA. 3D TOF MRA (TR/TE = 23/3.5; SENSE factor = 2.5) and CE-MRA by using a 3D ultrafast gradient-echo sequence (TR/TE = 5.9/1.8; SENSE factor = 3) enhanced with 0.1-mmol/kg gadobenate dimeglumine were performed in the same session. Source images, 3D maximum intensity projection, 3D shaded surface display, and/or 3D volume-rendered reconstructions were evaluated in terms of aneurysm occlusion/patency and artifact presence.RESULTS: In terms of clinical classification, the 2 MRA sequences were equivalent for 53 of the 54 treated aneurysms: 21 were considered fully occluded, whereas 16 were considered to have a residual neck and 16 were considered residually patent at follow-up MRA. The remaining aneurysm appeared fully occluded at TOF MRA but had a residual patent neck at CE-MRA. Visualization of residual aneurysm patency was significantly (P = .001) better with CE-MRA compared with TOF MRA for 10 (31.3%) of the 32 treated aneurysms considered residually patent with both sequences. Coil artifacts were present in 5 cases at TOF MRA but in none at CE-MRA. No relationship was apparent between the visualization of patency and either the size of the aneurysm or the interval between embolization and follow-up.CONCLUSION: At follow-up MRA at 3T, unenhanced TOF and CE-MRA sequences are similarly effective at classifying coiled aneurysms as occluded or residually patent. However, CE-MRA is superior to TOF MRA for visualization of residual patency and is associated with fewer artifacts.

Regular imaging follow-up of patients with intracranial aneurysms treated with Guglielmi detachable coils (GDCs) is necessary because of the risk of aneurysm reconfiguration (ie, coil compaction and/or growth of a residual aneurysm neck or body remnant) with time.^1–4 Of the techniques available for monitoring the results of embolization therapy, MR angiography (MRA) has emerged as the technique of choice at most institutions. Advantages over conventional digital subtraction angiography (DSA) include minimal invasiveness with no associated risk of neurologic complications, reduced patient discomfort and inconvenience, greater cost savings, and no exposure to ionizing radiation or potentially nephrotoxic iodinated contrast media. An alternative minimally invasive procedure is CT angiography (CTA). However, whereas this technique has proved useful for aneurysm detection,^5–9 limitations to its use for follow-up of coiled aneurysms include streak and other coil-related artifacts.^10–12 Moreover, CTA also requires exposure to ionizing radiation and iodinated contrast media, which may be undesirable if repeat follow-up examinations are required.Studies performed to date have shown that nonenhanced 3D time-of-flight (TOF) MRA sequences on 1.5T scanners are frequently satisfactory for the follow-up of coiled aneurysms^1–20 but that 3D TOF MRA on 3T scanners offers improved depiction of both treated²¹ and untreated²² aneurysms due to the greater spatial and contrast resolution achievable at a higher magnetic field strength. Concerning the use of gadolinium contrast material, some studies have suggested that contrast-enhanced MRA (CE-MRA) provides no additional benefit compared with nonenhanced 3D TOF MRA at either 1.5T^15,20 or 3T,²¹ whereas other studies have shown that CE-MRA permits better visualization of coiled aneurysms and of branch arteries and residual neck, particularly in large or giant aneurysms.^14,22–26 Recently, Nael et al²⁷ demonstrated that CE-MRA with highly accelerated (×4) parallel acquisition at 3T provides comparable information to accelerated (×2) 3D TOF MRA at 3T for the characterization of untreated intracranial aneurysms without the known drawbacks of TOF MRA techniques (ie, prolonged acquisition time, spin saturation, and flow-related artifacts). On the other hand, Gibbs et al²⁸ showed that with elliptic-centric imaging, 3D TOF MRA at 3T is superior to CE-MRA at 3T in terms of both image quality and detection of untreated intracranial aneurysms. Our study was performed to evaluate CE-MRA with accelerated (×3) parallel acquisition at 3T compared with accelerated (×2.5) 3D TOF MRA at 3T for the follow-up of GDC-treated intracranial aneurysms. To the authors’ knowledge, this is the first study to compare MRA sequences at 3T for follow-up of coiled aneurysms.     

Carotid artery stenosis: intraindividual correlations of 3D time-of-flight MR angiography, contrast-enhanced MR angiography, conventional DSA, and rotational angiography for detection and grading

PURPOSE: To compare three-dimensional (3D) time-of-flight (TOF) MR angiography, contrast-enhanced MR angiography, digital subtraction angiography (DSA), and rotational angiography for depiction of stenosis. MATERIALS AND METHODS: The study had Ethics Committee approval, and each patient gave written informed consent. Forty-nine patients (18 women, mean age, 67.2 years +/- 9.1 [+/- standard deviation], and 31 men, mean age, 63.1 years +/- 8.0) with symptomatic stenosis of internal carotid artery (ICA) diagnosed at duplex ultrasonography underwent transverse 3D TOF MR angiography with sliding interleaved kY acquisition and coronal contrast-enhanced MR angiography, followed by DSA and rotational angiography within 48 hours. MR angiography was performed at 1.5-T with a cervical coil. Contrast-enhanced MR angiograms were obtained after a bolus injection of 20 mL of gadobenate dimeglumine. Maximum ICA stenosis on maximum intensity projection and source images was quantified according to NASCET criteria. Correlations for 3D TOF MR angiography, contrast-enhanced MR angiography, DSA, and rotational angiography were determined by means of cross tabulation, and accuracy for detection and grading of stenoses were calculated. Data were evaluated with analysis of variance, Wilcoxon signed rank test, and McNemar test, all at significance of P < .05. RESULTS: Ninety-eight ICAs were evaluated at contrast-enhanced MR angiography, DSA, and rotational angiography, and 97 were evaluated at 3D TOF MR angiography. Correlations for contrast-enhanced MR angiography, 3D TOF MR angiography, and DSA relative to rotational angiography were r2 = 0.9332, r2 = 0.9048, and r2 = 0.9255, respectively. Lower correlation (r2 = 0.8593) was noted for contrast-enhanced MR angiography and DSA. Respective sensitivity and specificity for detection of hemodynamically relevant stenosis relative to rotational angiography were 100% and 90% for contrast-enhanced MR angiography, 95.5% and 87.2% for 3D TOF MR angiography, and 88.6% and 100% for DSA. Four of 31 severe stenoses were underestimated at DSA, and three were underestimated at contrast-enhanced MR angiography. Three severe stenoses were underestimated at 3D TOF MR angiography, and one was misclassified as occluded. Of 13 moderate (50%-69%) stenoses, one was overestimated at contrast-enhanced MR angiography, two were underestimated and three overestimated at 3D TOF MR angiography, and two were underestimated at DSA. CONCLUSION: DSA results in an underestimation of ICA stenosis compared with rotational angiography. Contrast-enhanced MR angiography correlates best with rotational angiography.     

High-resolution multiphase contrast-enhanced three-dimensional MR angiography compared with two-dimensional time-of-flight MR angiography for the identification of pedal vessels

PURPOSE: The authors prospectively evaluated optimized multiphase high-resolution (HR) Gadolinium (Gd)-enhanced three-dimensional (3D) magnetic resonance (MR) angiography and standard two-dimensional (2D) time-of-flight (TOF) MR angiography for their ability to delineate distal calf and pedal vessels. MATERIALS AND METHODS: Twelve patients (20 limbs) with limb-threatening peripheral arterial occlusive disease underwent HR Gd-enhanced and 2D TOF MR angiography to identify targets for distal bypass. Imaging of the region of the ankle and foot was performed on a 1.5 T system with a head coil. A standard 2D TOF MR angiography sequence was performed first. The HR Gd-enhanced MR angiography sequence was then performed after injection of 0.01-0.2 mmol/kg of gadodiamide, allowing the acquisition of multiple consecutive coronal partitions, each in 18-25 seconds. Two experienced angiographers independently analyzed both studies. Comparison with intraoperative conventional angiography was available in 10 limbs. RESULTS: HR Gd-enhanced MR angiography allowed significantly faster imaging time (P <.0001) and larger coverage area (P <.0001) than 2D TOF MR angiography. All segments seen on 2D TOF MR angiography were visualized on HR Gd MR angiography, and significantly more suitable targets were seen well on HR Gd-enhanced MR angiography than on 2D TOF MR angiography (mean targets per limb: 3.9 +/- 1.9 vs 2.6 +/- 1.5, respectively; P =.02). In addition, HR Gd-enhanced MR angiography allowed better visualization of the arcuate pedal branch than 2D TOF MR angiography (P <.0001). Excellent correlation was demonstrated between HR Gd-enhanced MR angiography and intraoperative angiography in 29 segments (binary similarity coefficient, 0.90). A significantly higher percentage of artifacts adversely affected image interpretation with 2D TOF MR angiography than with HR Gd-enhanced MR angiography (14 limbs vs five limbs, P <.001). Artifacts on HR Gd-enhanced MR angiography included suboptimal mask in two limbs, venous contamination in one patient (two limbs), and motion artifact in one limb, although the studies remained diagnostic in all cases. CONCLUSION: HR Gd-enhanced MR angiography identified more distal target vessels with greater confidence than 2D TOF MR angiography. Optimized HR Gd-enhanced MR angiography may replace 2D TOF MR angiography as the gold standard examination for evaluation of distal runoff.     

HYPR TOF: time-resolved contrast-enhanced intracranial MR angiography using time-of-flight as the spatial constraint

Purpose

To investigate the feasibility of using time‐of‐flight (TOF) images as a constraint in the reconstruction of a series of highly undersampled time‐resolved contrast‐enhanced MR images (HYPR TOF), to allow simultaneously high temporal and spatial resolution and increased SNR.

Materials and Methods

Ten healthy volunteers and three patients with aneurysms underwent a HYPR TOF study, which includes a clinical routine TOF scan followed by a first pass time‐resolved contrast‐enhanced exam using an undersampled three‐dimensional (3D) projection trajectory (VIPR). Image quality, waveform fidelity and signal to background variation ratio measurements were compared between HYPR TOF images and VIPR images without HYPR reconstruction.

Results

Volunteer results demonstrated the feasibility of using the clinical routine TOF as the spatial constraint to reconstruct the first pass time‐resolved contrast‐enhanced MRA acquired using highly undersampled 3D projection trajectory (VIPR). All the HYPR TOF images are superior to the corresponding VIPR images with the same temporal reconstruction window on both spatial resolution and SNR.

Conclusion

HYPR TOF improves the spatial resolution and SNR of the rapidly acquired dynamic images without losing the temporal information. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc.     

Visceral artery aneurysms: evaluation using 3D contrast-enhanced MR angiography

OBJECTIVE: Visceral artery aneurysms are uncommon, but they are clinically important because of the high incidence of rupture and life-threatening hemorrhage. Visceral artery aneurysms in patients with vascular anatomic variations are extremely rare, but detecting these variations is significant in this setting to determine the best treatment strategy; therefore, a thorough assessment of the aneurysm and of the vascular anatomy before treatment is paramount. CONCLUSION: Three-dimensional contrast-enhanced MR angiography is a noninvasive technique for the diagnosis and display of visceral artery aneurysms. It can provide 3D anatomic information that is needed for surgery or embolization.     

MR angiography of internal carotid arteries: breath-hold Gd-enhanced 3D fast imaging with steady-state precession versus unenhanced 2D and 3D time-of-flight techniques

PURPOSE: The purpose of this work was to compare Gd-enhanced breath-hold fast imaging with steady-state precession (Gd-FISP) with unenhanced time-of-flight (TOF) sequences in evaluating internal carotid arteries (ICAs). METHOD: Thirty patients underwent three unenhanced TOF sequences [2D traveling saturation (Travelsat); 3D tilted optimized nonsaturated excitation (TONE); TOF 3D Multislab] and two breath-hold 3D Gd-FISP sequences with automated intravenous contrast agent injection (axial and coronal). ICAs were classified as normal (no stenosis); with mild (<30%), moderate (30-70%), or severe stenosis; or occluded (100%). Digital subtraction angiography (DSA) with aortic arch injection was used as a reference technique. RESULTS: DSA revealed 20 normal ICAs; 11 mild, 9 moderate, and 14 severe stenoses; and 2 occlusions. DSA and all MR angiography (MRA) sequences diagnosed the occlusion of four common carotid arteries. The TOF 2D overestimated 10 stenoses, TOF 3D TONE 9, and TOF 3D Multislab 5; Gd-FISP 3D overestimated only 2 of them, reaching the highest sensitivity and specificity for severe stenoses. Significant differences were found between the overestimation of Gd-FISP and each of the three unenhanced sequences (0.0020 < p < 0.0313, Wilcoxon and McNemar tests). Severe artifacts were observed with TOF techniques only. CONCLUSION: Gd-FISP is an interesting, largely artifact-free improvement for MRA of ICAs.     

3.0-Tesla MR angiography of intracranial aneurysms: comparison of time-of-flight and contrast-enhanced techniques

PURPOSE: To determine whether 3.0-T elliptical-centric contrast-enhanced (CE) magnetic resonance (MR) angiography is superior to 3.0-T elliptical-centric time-of-flight (TOF) MR angiography in the detection and characterization of intracranial aneurysms, and to determine whether increasing the acquisition matrix size in 3.0-T CE MR angiography improves image quality. MATERIALS AND METHODS: A total of 50 consecutive patients referred for MR angiographic evaluation of a known or suspected intracranial aneurysm underwent MR angiography, including three-dimensional TOF and elliptical-centric CE techniques at 3.0 T. The 3.0-T three-dimensional TOF and 3.0-T CE examinations were graded for image quality. A blind review identified the presence and location of aneurysms. RESULTS: A total of 28 aneurysms were identified in 23 of the 50 patients. The 3.0-T TOF MR angiography had a higher mean score for image quality than the 3.0-T elliptical-centric CE MR angiography (P < 0.0001). A total of 14 patients with aneurysms had conventional angiography for comparison. The 3.0-T TOF showed all the aneurysms, whereas 3.0-T CE MR angiography did not show 1 of 19 aneurysms when conventional angiography was the reference standard. CONCLUSION: For imaging intracranial aneurysms, 3.0-T TOF MR angiography offers better image quality than 3.0-T CE MR angiography using the elliptical-centric technique.     

3D time-resolved MR angiography (MRA) of the carotid arteries with time-resolved imaging with stochastic trajectories: comparison with 3D contrast-enhanced Bolus-Chase MRA and 3D time-of-flight MRA

BACKGROUND AND PURPOSE: Time-resolved MR angiography (MRA) offers the combined advantage of large anatomic coverage and hemodynamic flow information. We applied parallel imaging and time-resolved imaging with stochastic trajectories (TWIST), which uses a spiral trajectory to undersample k-space, to perform time-resolved MRA of the extracranial internal carotid arteries and compare it to time-of-flight (TOF) and high-resolution contrast-enhanced (HR) MRA.MATERIALS AND METHODS: A retrospective review of 31 patients who underwent carotid MRA at 1.5T using TOF, time-resolved and HR MRA was performed. Images were evaluated for the presence and degree of ICA stenosis, reader confidence, and number of pure arterial frames attained with the TWIST technique.RESULTS: With a consensus interpretation of all sequences as the reference standard, accuracy for identifying stenosis was 90.3% for TWIST MRA, compared with 96.0% and 88.7% for HR MRA and TOF MRA, respectively. HR MRA was significantly more accurate than the other techniques (P < .05). TWIST MRA yielded datasets with high in-plane spatial resolution and distinct arterial and venous phases. It provided dynamic information not otherwise available. Mean diagnostic confidence was satisfactory or greater for TWIST in all patients.CONCLUSION: The TWIST technique consistently obtained pure arterial phase images while providing dynamic information. It is rapid, uses a low dose of contrast, and may be useful in specific circumstances, such as in the acute stroke setting. However, it does not yet have spatial resolution comparable with standard contrast-enhanced MRA.

Stroke has an estimated prevalence of 5.7 million (2.6%) adults in the United States, where it is the third most common cause of mortality.¹ Atherosclerotic carotid artery disease is an important risk factor for anterior circulation ischemic stroke. Imaging evaluation is essential for optimal management and stroke prevention, as demonstrated in studies of symptomatic^2,3 and asymptomatic populations.^4,5 Carotid dissection is another potential cause of anterior circulation ischemia, which also requires high-spatial-resolution imaging for definitive diagnosis.Digital subtraction angiography (DSA) remains the gold standard for assessment of the cervical vasculature,⁶ with excellent spatial and temporal resolution. However, risks include vascular injury, intracerebral complications, contrast nephrotoxicity, and exposure to ionizing radiation. Therefore, noninvasive techniques are typically used initially. Duplex Doppler sonography, CT angiography (CTA), and MR angiography (MRA) all have high but varying degrees of sensitivity and specificity, ranging from 70% to 99% for carotid stenosis detection.⁷ Although sonography provides excellent dynamic information and spatial resolution, insonation window limitations restrict anatomic coverage. Similarly, long imaging times with time-of-flight (TOF) MRA also limit anatomic coverage. CTA and conventional arterial contrast-enhanced MRA offer extensive coverage but provide no dynamic information and are dependent on accurate timing for optimal visualization of the arterial tree.3D time-resolved contrast-enhanced MR angiography (TR MRA) has been previously described.⁸ TR MRA offers combined anatomic and hemodynamic information and obtains pure arterial and venous phase images consistently and rapidly without a timing run. More recently, the technique has been specifically applied to the extracranial carotid arteries using parallel imaging or keyhole imaging techniques.^9,10 In this study, we report the diagnostic accuracy of TR MRA of the extracranial internal carotid artery (ICA) acquired with a combination of parallel imaging (generalized autocalibrating partially parallel acquisition [GRAPPA])¹¹ and time-resolved imaging with stochastic trajectories (TWIST), a new view-sharing technique, which undersamples the periphery of k-space depending on the radial distance from the center of k-space.^12,13 We compared TR MRA with 3D high-resolution contrast enhanced MRA (HR MRA) and 3D TOF MRA.     

Endometriosis: Appearance and detection with conventional and contrast-enhanced fat-suppressed spin-echo techniques

Suspected pelvic endometrlosis was prospectively evaluated in 31 women with T1- and T2-weighted conventional spin-echo (CSE) magnetic resonance imaging alone and in combination with Tl-weighted fat-suppressed (TIPS) and gadolinium-enhanced TIPS (Gd-TlFS) spin-echo techniques. Images were grouped for interpretation and comparison as follows: (a) CSE alone, (b) CSE/T1FS. and (c) CSE/T1FS/ Gd-TlFS. All patients underwent surgery within 3 months of imaging, and 21 patients were found to have endometrlosis: 59 endometriomas (26 large and 33 small) and 51 sites of implants were seen. With CSE images, 23 large and six small endometriomas were detected. With CSE/T1FS images, 25 large and 14 small endometriomas were identified. With CSE/ TIFS/Gd-TlFS Images, 24 large and 14 small endometriomas were detected and ill-defined areas of enhancement were noted in 22 sites throughout the pelvis. These corresponded to endometriotic implants seen at surgery in 14 sites. The sensitivity, specificity, and accuracy, respectively, for the detection of endometriosis were 76%, 60%, and 71% for CSE, 86%, 50%, and 74% for CSE/T1FS, and 81%, 50%, and 71% for CSE/TlFS/Gd-TlFS images. No significant differences (P > 0.1) between image combinations for correctly identifying patients with and without endometriosis were seen. The difference in sensitivity between CSE and CSE/T1FS and between CSE and CSE/TlFS/Gd-TlFS images for detecting small endometriomas was significant (P=.03).     

Postoperative assessment of extracranial-intracranial bypass by time-resolved 3D contrast-enhanced MR angiography using parallel imaging

PURPOSE: Our goals were to assess image quality of time-resolved contrast-enhanced MR angiography (CE MRA), by using 3D data acquisition along with a parallel imaging technique that can improve temporal resolution and to compare this technique with 3D-time-of-flight (TOF) MRA in the postoperative assessment of extracranial (EC)-intracranial (IC) bypass surgery. METHODS: On a 1.5T imaging system, we performed CE MRA by using a 3D fast field-echo sequence in combination with a parallel imaging technique, to obtain images in the coronal plane centered at the postoperative site. Our patient group comprised 17 patients, including 13 after superficial temporal artery-middle cerebral artery (MCA) anastomosis, 3 after external carotid artery-MCA anastomosis, and one after extracranial vertebral artery-posterior cerebral artery anastomosis. Visualization of the anastomosis and the distal flow on the CE-MRA images was assessed comparatively with that on 3D-TOF MR angiograms obtained at the same time. In 6 patients, we also compared the efficiency of visualization on CE-MRA images with that on conventional angiograms. RESULTS: A temporal resolution of 0.8 s/frame could be achieved with the technique employed. The bypass was better demonstrated postoperatively on CE-MRA images than on 3D-TOF MR angiograms in 13 patients (76%), whereas the 2 methods were equivalent in 4 patients (24%). Good correspondence of results was observed in the 6 patients for whom CE MRA and conventional digital subtraction angiography (DSA) images were compared. CONCLUSION: CE MRA by using the parallel imaging technique can increase image acquisition speed with sufficient image quality. This technique is at least equivalent to 3D-TOF MRA to evaluate the postoperative status of EC-IC bypass.     

Combining time-resolved and single-phase 3D techniques in contrast-enhanced carotid MR angiography.

We established an easy-to-use technique for performing contrast-enhanced carotid MR angiography (MRA) with a commercial scanner. Twenty-three patients with suspected carotid or vertebral arterial lesions were prospectively studied. Two techniques were applied in the study. After performing sagittal time-resolved acquisitions, we undertook a coronal single-phase 3D acquisition, in which the injection timing was estimated from the preceding images. In each case, we obtained multidirectional images with sufficient venous suppression. The combined use of time-resolved and single-phase 3D MRA is a feasible technique for obtaining selective arterial images without the use of special applications or hardware.     

Vascularization of head and neck paragangliomas: comparison of three MR angiographic techniques with digital subtraction angiography

BACKGROUND AND PURPOSE: MR angiography of the head and neck region has been studied widely, but few studies have been performed concerning the efficacy of MR angiography for the identification of the specific vascular supply of the highly vascular head and neck paragangliomas. In this study, we compared three MR angiography techniques with respect to visualization of branch arteries in the neck and identification of tumor feeders in patients with paragangliomas. METHODS: Fourteen patients with 29 paragangliomas were examined at 1.5 T using 3D phase-contrast (PC), 2D time-of-flight (2D TOF), and multi-slab 3D TOF MR angiography. In the first part of the study, two radiologists independently evaluated the visibility of first-, second-, and third-order branch arteries in the neck. In the second part of the study, the number of feeding arteries for every paraganglioma was determined and compared with digital subtraction angiography (DSA), the standard of reference in this study. RESULTS: Three-dimensional TOF angiography was superior to the other MR angiography techniques studied (P < .05) for depicting branch arteries of the external carotid artery in the neck, but only first- and second-order vessels were reliably shown. DSA showed a total of 78 feeding arteries in the group of patients with 29 paragangliomas, which was superior to what was revealed by all MR angiography techniques studied. More tumor feeders were identified with 3D TOF and 2D TOF angiography than with 3D PC MR angiography (P < .05), with a sensitivity/specificity of 61%/98%, 54%/95%, and 31%/95%, respectively. Sensitivity was lowest for carotid body tumors. CONCLUSION: Compared with intra-arterial DSA, the 3D TOF MR angiography technique was superior to 3D PC and 2D TOF MR angiography for identifying the first- and second-order vessels in the neck. With 3D TOF angiography, more tumor feeders were identified than with the other MR angiography techniques studied. The sensitivity of MR angiography, however, is not high enough to reveal important vascularization. The sensitivity of MR angiography is too low to replace DSA, especially in the presence of carotid body tumors.     

Combination of 2D sensitivity encoding and 2D partial fourier techniques for improved acceleration in 3D contrast-enhanced MR angiography.

Sensitivity encoding (SENSE) and partial Fourier (PF) techniques both reduce MRI acquisition time. Two-dimensional SENSE uses coil sensitivities to unfold aliasing in the phase/slice-encoding plane. One-dimensional PF and homodyne reconstruction are routinely applied in the frequency/phase-encoding plane to compensate for nonsampled k-space of the presumed real magnetization. Recently, a modified 3D elliptical centric acquisition was proposed to facilitate 2D-PF and homodyne reconstruction on an undersampled phase/slice-encoding plane. In this work we hypothesized that this 2D-PF technique can be combined with 2D-SENSE to achieve a greater acceleration factor than what each method can provide separately. Reconstruction of data whereby SENSE and PF are applied along the same axes is described. Contrast-enhanced MR angiography (CE-MRA) results from experiments using four receiver coils in phantom and volunteer studies are shown. In 11 volunteer studies, the SENSE-PF-homodyne technique using sevenfold acceleration (4x SENSE, 1.7x PF) consistently provided high-diagnostic-quality images with near 1-mm isotropic resolution in acquisition times of <20 s.     

Carotid artery: elliptic centric contrast-enhanced MR angiography compared with conventional angiography

PURPOSE: To determine the accuracy of elliptic centric contrast material-enhanced magnetic resonance (MR) angiography by using conventional angiography as the reference standard. MATERIALS AND METHODS: Fifty patients were examined prospectively with contrast-enhanced MR angiography and conventional angiography. The two examinations were performed within 1 week of each other. Two patients underwent conventional angiography of only one carotid artery, which yielded 98 arteries for comparison. RESULTS: With conventional angiography as the reference standard and by using a 70% threshold for internal carotid arterial diameter stenosis, maximum intensity projection (MIP) images had a sensitivity of 93.3%, specificity of 85.1%, and accuracy of 87.6%, whereas reformatted transverse source images had a sensitivity of 83.3%, specificity of 97.0%, and accuracy of 92.8%. Interobserver variability for conventional angiograms was 0.97, for MIP images was 0.91, and for source images was 0.90. The contrast-enhanced MR angiographic technique had a sensitivity of 88.9% and specificity of 58.1% for the presence of irregularity and/or ulceration. All 50 examinations were triggered appropriately so that minimal or no venous signal intensity was depicted. CONCLUSION: Contrast-enhanced elliptic centric three-dimensional MR angiography offers high-spatial-resolution, venous-suppressed images of the carotid arteries that appear to be adequate to replace conventional angiography in most patients examined prior to carotid endarterectomy.