Gradient recalled echo MR imaging of the jugular foramen

Axial T1-weighted spin-echo MR images have not proved to be effective in identifying normal structures in the jugular foramen. By correlating cryomicrotomic sections and axial T1-weighted gradient recalled echo images, we identified the neural and vascular contents of the jugular foramen. Further work with gradient recalled echo images is needed to determine the signal characteristics of jugular foraminal lesions.     

上矢状窦闭塞后静脉侧支循环的影像学表现及临床意义初探

目的：借助影像学表现分析窦旁脑膜瘤导致上矢状窦完全闭塞后其前、中、后三个区域静脉侧支循环表现和临床意义。材料与方法：选择经手术病理证实的窦旁脑膜瘤导致上状窦完全闭塞者３０例，分析其影像表现（颅脑血管造影、ＣＴ、ＭＲ），依据解剖标志将上矢状窦划分为前、中、后三区。结果：慢性窦旁脑膜瘤术前颅脑血管造影对评价上矢状窦闭塞情况及侧支循环有重要指导作用。前、中、后三区静脉侧支循环表现各异，聘相应临床症状。结     

Gradient echo imaging

Magnetic resonance imaging (MRI) based on gradient echoes is used in a wide variety of imaging techniques and clinical applications. Gradient echo sequences form the basis for an essential group of imaging methods that find widespread use in clinical practice, particularly when fast imaging is important, as for example in cardiac MRI or contrast‐enhanced MR angiography. However, the term “gradient echo sequence” is somewhat unspecific, as even images acquired with the most common sequences employing the gradient echo for data acquisition can significantly differ in signal, contrast, artifact behavior, and sensitivity to, eg, flow. This is due to the different use of sequence timing and basic sequence building blocks such as spoiler gradients or specific radiofrequency (RF) pulse phase patterns. In this article the basic principles of gradient echo formation compared to spin echo imaging are reviewed and the properties of gradient echo imaging in its simplest form (TR ? T₂) are described. Further, the most common three variants of fast gradient echo sequences (TR < T₂), namely, unbalanced gradient echo, RF spoiled gradient echo, and balanced steady state free precession; are discussed. For each gradient echo sequence type, examples of applications exploiting the specific properties of the individual technique are presented. J. Magn. Reson. Imaging 2012;35:1274–1289. © 2012 Wiley Periodicals, Inc.     

Musculoskeletal MR imaging: turbo (fast) spin-echo versus conventional spin-echo and gradient-echo imaging at 0.5 tesla

The value of T2-weighted fast spin-echo imaging of the musculoskeletal system was assessed in 22 patients with various neoplastic, inflammatory, and traumatic disorders. Images were acquired with high echo number (i.e., echo train length) fast spin-echo (FSE; TR 2000 ms, effective TE 100 ms, echo number 13, lineark-space ordering), conventional spin-echo (SE; TR 2000 ms, TE 100 ms) and gradient-echo (GRE) sequences (TR 600 ms, TE 34 ms, flip angle 25°). Signal intensities, signal-to-noise ratios, contrast, contrast-to-noise ratios, lesion conspicuousness, detail perceptibility, and sensitivity towards image artifacts were compared. The high signal intensity of fat on FSE images resulted in a slightly inferior lesion-to-fat contrast on FSE images. However, on the basis of lesion conspicuity, FSE is able to replace time-consuming conventional T2-weighted SE imaging in musculoskeletal MRI. In contrast, GRE images frequently showed superior lesion conspicuity. One minor disadvantage of FSE in our study was the frequent deterioration of image quality by blurring, black band, and rippling artifacts. Some of these artifacts, however, can be prevented using short echo trains and/or short echo spacings.     

MR imaging of the cavernous sinus: value of spin echo and gradient recalled echo images

A detailed evaluation of the MR appearance of the pituitary gland-cavernous sinus junction has not been described. In a series of coronal T1-weighted spin echo images without and with IV gadolinium, we noted the variable size and signal intensity of cavernous venous spaces adjacent to the pituitary gland and the inconsistent visualization of the dural membrane just lateral to the gland. Correlation of coronal T1-weighted spin echo and gradient recalled echo images (the latter with high-signal-intensity vascular structures) proved to be an effective means of identifying cavernous venous spaces, connective tissue and cranial nerves, and the lateral margins of the pituitary gland, and of differentiating tumor tissue from cavernous venous spaces. Further work is needed to develop criteria to distinguish cavernous sinus compression from actual tumor invasion.     

Gradient and stimulated echo (GRASTE) imaging.

As a modification of single-shot stimulated echo acquisition mode (STEAM) MRI, a gradient and stimulated echo (GRASTE) sequence is presented that acquires multiple gradient echoes in addition to each stimulated echo. While "contiguous" GRASTE exploits all stimulated echoes for the central part of k-space and the gradient echoes for outer lines, "interleaved" GRASTE assigns all echoes of a particular readout interval to directly neighboring lines. Phase distortions may be corrected by the reference signals of a single readout interval without phase encoding. Experimental results obtained for the human brain demonstrate that contiguous GRASTE yields up to 30% better SNR per acquisition time than conventional single-shot STEAM due to a better efficiency and maintains most of its robustness. Interleaved GRASTE can improve the SNR by a factor of 2 because of the possibility of using larger flip angles in the readout interval. However, its more pronounced sensitivity to off-resonance effects requires short echo trains.     

肩袖MRI:梯度回波和快速自旋回波的比较

目的 评价梯度回波T2*WI对肩袖病变的诊断价值。资料与方法 对35例可疑肩袖损伤的病例进行前瞻性MRI检查，对比分析斜冠状位T2*WI和脂肪抑制快速自旋回波T2WI（FS TSET2WI）对肩袖病变的诊断价值。结果 T2*WI和FS TSE T2WI对肩袖损伤的评价具有较好的诊断一致性，Kappa值为0.746。不管是对总的肩袖撕裂，还是对于肩袖全层撕裂，T2*WI的诊断敏感性和阴性预测值均高于FS TSE T2WI，但其诊断特异性和阳性预测值降低。结论 T2*WI和FS TSE T2WI对于肩袖损伤的评价具有较好的诊断一致性。     

低场强磁共振梯度回波在颈椎间盘突出中的应用价值

目的探讨低场强磁共振梯度回波在颈椎间盘突出中的应用价值。方法对176例患者颈部MRI资料回顾性分析,对比横断T1WI、T2WI、T2^＊WI对椎间盘突出的显示率并作统计学处理。结果176例中共有椎间盘突出416个,其中T1WI显示70个（占16．82％）,T2WI显示304个（占73．07％）,T2^＊WI显示406个（占97．59％）。结论低场强磁共振梯度回波能更好的显示颈椎间盘突出,可作为颈椎常规检查序列,以弥补自旋回波的不足。     

Segmented echo planar MR imaging of the brachial plexus with inversion recovery magnetization preparation at 3.0T

PURPOSE: To evaluate the image quality of segmented echo planar MRI with inversion recovery magnetization preparation (seg-IR-EPI) to depict the anatomy and pathologic changes involving the brachial plexus. MATERIALS AND METHODS: The coronal seg-IR-EPI sequence was performed on 30 healthy volunteers and 20 patients. Postprocessing techniques were used to generate images of brachial plexus and the images acquired were qualitatively evaluated by two experienced radiologists based on grading of the morphological images. Signal-to-noise ratios (SNRs) and nerve soft tissue contrast-to-noise-ratios (CNRs) were calculated and the normalized SNR (SNRn) and the normalized CNR (CNRn) were compared with the STIR TSE sequence. RESULTS: Although seg-IR-EPI had more ghosting artifacts than STIR TSE, excellent general image appearance with minor blurring can be achieved with seg-IR-EPI. In all healthy volunteers the means of CNRn were significantly greater for seg-IR-EPI than for STIR-TSE, while the means of SNRn were significantly lower for seg-IR-EPI than for STIR-TSE. CONCLUSION: In the present study the seg-IR-EPI sequence obtained uniform fat suppression and high-contrast T2-weighted images of brachial plexus. Our data suggest that the seg-IR-EPI sequence may provide high fidelity in evaluating brachial plexus.     

三维平衡式快速场梯度回波和时间飞跃法血管造影技术对三叉神经的对比研究

目的:探讨MR扫描三叉神经与周围血管的最佳序列。方法:对16例三叉神经痛患者行三叉神经3D BTFE和3D TOF MRA扫描。测量双侧三叉神经与桥前池的CNR、椎-基底动脉与桥前池CNR、三叉神经与桥前池对比度。根据三叉神经图像质量、周围血管显示、神经与血管的关系进行评分。结果:3D BTFE组三叉神经与桥前池CNR、对比度较3D TOF MRA组高〔22.94±4.18(左)and 21.68±5.51(右)vs 5.92±3.01(左)and 6.37±3.86(右)〕、〔1834±294(左)and 1968±351(右)vs 572±42(左)and 468±55(右)〕。3D BTFE组椎-基底动脉与桥前池CNR较3D TOFMRA低〔2.47±1.17 vs 6.21±2.87〕(P0.01)。3D BTFE组三叉神经图像质量较好。3D TOF MRA组血管显示较好、血管与神经关系较清晰(P0.05,Kappa0.75)。结论:3D BTFE和3D TOF MRA序列联合应用,可以清晰观察到三叉神经解剖学改变及神经与周围血管关系,对设计和优化MVD具有重要意义。     

Large arachnoid granulations involving the dorsal superior sagittal sinus: findings on MR imaging and MR venography

BACKGROUND AND PURPOSE: Large arachnoid granulations (AG) within the dorsal superior sagittal sinus (SSS) have been incompletely characterized and can be confused with pathology. This report reviews the characteristics of these anatomic structures to establish common imaging features that allow differentiation from pathology.MATERIALS AND METHODS: Twelve cases of large AG in the dorsal SSS are presented, identified by MR imaging. Signal intensity characteristics, size, location, venographic appearance, and association with adjacent venous and osseous structures were documented.RESULTS: A defect in the dura of the SSS was seen in all of the cases communicating with the subjacent subarachnoid space. The average size of the AG was 8.1 × 9.4 × 10.0 mm (range, 4–19 mm). Ten produced calvarial remodeling, and 11 were in the direct vicinity of the lambda. On T2-weighted images, all were hyperintense to the brain. On T1-weighted images, 8 were hypointense and 4 were hypointense with mixed areas of isointense signal intensity. All of the AGs were associated with cortical venous structures entering the sinus. On MR venography, AGs appeared as focal protrusions into the sinus, displacing, distorting, and narrowing the sinus lumen. Seven patients had headache without other visible cause on MR imaging, and 4 were initially interpreted as thrombosis or tumor.CONCLUSION: Large AGs can occur in the dorsal SSS. They are well-defined projections of the subarachnoid space into the sinus, can cause luminal narrowing and calvarial remodeling, and have typical signal intensity characteristics, position, and morphology differentiating them from other pathology. Association with patient symptoms is uncertain.

Arachnoid granulations (AGs) are normal structures that can be demonstrated on CT and MR imaging.¹ They typically are identified as CSF attenuation or signal intensity protuberances projecting into the lumen of the dural sinuses.¹ Although most commonly identified on standard imaging studies in the midlateral transverse sinuses (TSs),^2,3 when more detailed high-resolution MR imaging examinations with contrast are used, they can be identified throughout the dural sinuses.⁴ Rarely, large AGs have been described in the dorsal (posterior inferior) superior sagittal sinus (SSS) on imaging^1,5 and on anatomic assessment.⁶ Because of their infrequency and large size, they can be misdiagnosed as a thrombus or tumor in this location.⁵ We have identified 12 cases of large AGs in the dorsal SSS on MR imaging (1.5T and 3T), and describe their appearance on standard MR pulse sequences, time-of-flight MR venography (MRV; TOF-MRV) and contrast-enhanced MRV (CE-MRV). We compared these cases with the few cases reported previously in the literature and established common imaging features that allow differentiation from pathology.     

High resolution computed tomography of superior sagittal sinus-thrombosis and-abnormalities

Summary Ten patients with suspected abnormalities or thrombosis of the superior sagittal sinus were studied by high resolution computed tomography using a thin slice technique after bolus injection. In all patients good visualization of the sinus pathology could be achieved, which correlated exactly with the findings in the 7 angiographically controlled cases.     

Endogenous susceptibility contrast in myocardium during apnea measured using gradient recalled echo planar imaging

Gradient recalled echo planar imaging was used to monitor changes in myocardial and left ventricular chamber blood intensity during apnea in rats. Significant signal loss in both blood (to 62 ± 5% and 51 ± 6% of baseline) and myocardium (to 79 ± 2% and 76 ± 3% of baseline) was observed at 45 and 90 s apnea while O₂ saturation decreased from 98 ± 1% to 62 ± 7% and 36 ± 9%, respectively. These results show that myocardial intensity is modulated by alterations in blood oxygenation.     

Diagnosis of partial and complete rotator cuff tears using combined gradient echo and spin echo imaging

Most magnetic resonance (MR) studies evaluating the rotator cuff for tears have used T2-weighted imaging in the coronal oblique and sagittal oblique planes, T2^*-weighted gradient echo imaging, however, has advantages over spin echo imaging, including contiguous slices without cross-talk, high contrast around the cuff, and intrinsically shorter imaging times which can be used to increase the number of signals averaged and thus improve the signal-to-noise ratio. We reviewed the shoulder MR scans of 87 consecutive patients who underwent both a MR scan and a shoulder arthroscopy during which the size of tears, if present, was graded. The reviewers were blinded as to the history and arthroscopic results. The MR scans included oblique coronal T2^*-weighted gradient echo and oblique sagittal T2-weighted spin echo images. MR cuff grades were correlated with arthroscopic findings. For complete tears, the sensitivity of MR was 0.91 and the specificity 0.95. For partial tears, the sensitivity was 0.74 and the specificity 0.87. This accuracy is similar to two-plane T2-weighted imaging as previously reported in the literature. There was a statistically significant correlation (p < 0.0005) between the cuff grade as determined by MR and the arthroscopic findings.