Gd-enhanced MR imaging of acute and chronic experimental demyelinating lesions

Experimental allergic encephalomyelitis, a demyelinating disease with marked similarity to multiple sclerosis, was produced in two of 12 dogs. All dogs were studied with serial MR imaging. T1- and T2-weighted MR images were obtained both before and after IV Gd-DTPA. Multiple, new periventricular white matter demyelinating lesions were observed after each clinical episode of the disease. Like multiple sclerosis, the acute lesions of experimental allergic encephalomyelitis on T2-weighted MR images were indistinguishable from the older, more chronic lesions. However, after Gd-DTPA, there was bright paramagnetic enhancement of the acute lesions and, in one animal, no enhancement of the chronic lesions on T1-weighted MR images. At necropsy, the differences in the MR paramagnetic enhancement correlated well with the relative histologic age of the demyelinating lesions. Our results suggest that MR with Gd-DTPA may be used to differentiate acute, active demyelinating lesions from the more chronic, inactive lesions in this animal model.     

Magnetic resonance study of lesions of the cervical spinal cord in multiple sclerosis

Lesions consistent with demyelinating plaques were retrospectively identified in the cervical spinal cord of 15/49 patients (31%) with multiple sclerosis examined with cranial and cervical MR imaging. The lesions appeared as hyperintense areas on proton-density and T2-weighted images. Clinical signs and symptoms suggestive of spinal cord location of the demyelinating plaques were observed in 14 of the 15 patients presenting with spinal cord lesions at MR, and also in 11 of the 34 patients with negative MR findings. In 2 patients the cervical lesion was not associated with brain lesions at MR, while in 1 patient it was associated with medullary dilatation. Serial MRs revealed disappearance of the cervical hyperintense area in both patients, and reduction in medullary volume in the latter. Therefore, MR imaging of the cervical spinal cord is suggested as an useful examination in patients with suspected multiple sclerosis, particularly in those presenting with clinical signs and symptoms suggestive of spinal cord involvement.     

Experimental radiation injury: combined MR imaging and spectroscopy

A model of radiation injury to the brain was developed in the cat. Definite radiation changes were demonstrated at magnetic resonance (MR) imaging in four of six cats. These changes consisted of high-intensity abnormalities on images obtained with a long repetition time (TR) and a long echo time (TE), which were initially noted 208-285 days after irradiation. These changes were associated with gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA) enhancement on short TR and inversion-recovery (IR) pulse sequences. Gd-DTPA enhancement and the high intensity on the long TR/TE images were identified at the same time and became more prominent throughout the study. Chemical-shift imaging and phosphorus spectroscopy demonstrated no notable changes despite clear-cut MR evidence of abnormalities. Sodium imaging was positive in one case. Correlation of MR and pathologic findings revealed areas of radiation necrosis and wallerian degeneration that corresponded to areas of Gd-DTPA enhancement on short TR and IR images and to areas of high intensity on long TR/TE images. Peripheral to the areas of Gd-DTPA enhancement were nonenhanced zones of high-signal-intensity abnormality on long TR/TE images, which represented regions of demyelination without necrosis. Gd-DTPA-enhanced proton imaging was the most sensitive method for detecting radiation damage in this animal model.     

MR imaging of intradural inflammatory diseases of the spine

Twenty-eight patients with intradural inflammatory disease of the spine were studied in order to characterize the MR imaging findings of infectious and inflammatory conditions. Patients were categorized according to the spinal compartment involved. Among the 12 patients in the intradural extramedullary group, unenhanced scans were either normal or nonspecific while contrast-enhanced scans were helpful in visualizing and localizing the lesion. Nevertheless, contrast-enhanced MR studies were unable to differentiate infection and inflammation from tumor in this compartment. Among 16 patients with intramedullary lesions, four had granulomatous disease and 12 had nongranulomatous disease. The granulomatous lesions resembled tumors and displayed MR characteristics of a focal lesion with large nodular enhancement. The patients with nongranulomatous intramedullary lesions exhibited two subsets of MR findings. In the first subset of nine patients, diffuse cord swelling and high signal were seen on long TR images, combined with either no enhancement or peripheral, diffuse, or speckled enhancement of the spinal cord on contrast-enhanced short TR images. In the second subset of three patients, minimal or no spinal cord swelling was displayed despite the visualization of high signal on long TR scans and nodular enhancement with contrast administration on short TR scans. Both subsets were sufficiently unique that nongranulomatous myelitis could usually be differentiated from spinal cord tumors.     

Multiple sclerosis: serial study of gadolinium-enhanced MR imaging

Thirteen patients with definite multiple sclerosis (MS), studied 16-24 months previously with magnetic resonance (MR) imaging with and without enhancement by intravenously administered gadolinium diethylenetriaminepentaacetic acid (DTPA) dimeglumine, were reexamined with a similar protocol. Assessment of enhancement and clinical activity in both studies revealed that enhancement was observed in 13 of 14 cases in which clinical activity had changed within 4 weeks of the study and thus appeared more sensitive than clinical examination in determining active disease. The 3-minute postinjection, short repetition time image (TR) was the most efficient for depicting enhancement. Enhancing lesions (active plaques) arose from previously hyper- or isointense regions on long TR images. Previously active lesions reverted to areas of iso- or hyperintensity on long TR images. Serial comparison of long TR images in this population reveals a decrease in high-intensity lesions on long TR images in some cases and an increase in others. The findings of high-intensity regions on long TR images and previously enhancing lesions both becoming isointense suggests that transient inflammatory changes with concomitant edema without demyelination and/or with significant remyelination may occur in some MS lesions. MS lesions are dynamic; both active and inactive lesions may show dramatic change on longitudinal MR imaging studies.     

Chordomas of the skull base: MR features.

PURPOSE: To characterize the MR features of skull base chordomas with regard to signal intensity, size, position, extension, and Gd-DTPA enhancement. PATIENTS AND METHODS: The MR imaging studies of 28 patients with surgically proven chordomas of the skull base were retrospectively reviewed. Twenty-two of these patients received intravenous administration of Gd-DTPA. RESULTS: On short TR/short TE images, chordomas generally had low to intermediate signal. On long TR/long TE images, chordomas generally had very high signal that was heterogeneous in 79%. After Gd-DTPA administration, all chordomas demonstrated some degree of contrast enhancement. In most cases, enhancement was demonstrated throughout most of each tumor in a heterogeneous pattern. Chordomas were associated with MR findings of displacement and encasement of vessels, and frequent extension into adjacent structures such as the cavernous sinus, sella, nasopharynx, and hypoglossal canal. CONCLUSION: The MR characterization of the position and extent of these neoplasms played an important role in determining the optimal surgical approaches for gross total tumor resection.     

Gadopentetate dimeglumine enhancement of multiple sclerosis lesions on long TR spin-echo images at 0.6 T.

The authors sought to determine if Gd-DTPA enhancement of multiple sclerosis (MS) hampers lesion detection on long TR spin-echo images (TE 60 msec) at 0.6 T. They measured the signal intensity (SI) of 41 lesions (10 patients) and normal-appearing gray (NAGM) and white matter (NAWM) before and after administration of contrast. The change in SI of nonenhancing lesions and NAGM and NAWM was small (less than or equal to 1.5%), and of enhancing lesions (5.3%) moderate. The contrast of nonenhancing lesions to NAGM and NAWM changed insignificantly, but the contrast of enhancing lesions to NAGM and NAWM increased significantly. The authors conclude that long TR images can be obtained after Gd-DTPA without hampering lesion conspicuity in research MR protocols in multiple sclerosis.     

Pre- and postoperative MR imaging of the craniocervical junction in rheumatoid arthritis

Ten patients with severe chronic rheumatoid arthritis with atlantoaxial subluxation were examined with conventional radiography and MR imaging of the cervical spine before and at an average of 6 months after posterior occipitocervical fusion. Periodontoid pannus formation was revealed by MR preoperatively in nine patients, all with mobile horizontal atlantoaxial subluxation. Compression of the medulla and/or upper cervical cord, due to subluxation and periodontoid pannus bulging into the spinal canal, was seen in seven patients. After the stabilizing surgery the periodontoid pannus had decreased in size in all patients with preoperative pannus. This reduction in the pannus seems to be the result of the atlantoaxial immobility achieved by the posterior fusion. Postoperatively, three patients had some remaining compression of the medulla and/or cord secondary to immobile subluxation, while the pannus posterior to the odontoid process had disappeared. Artifacts from the surgical stainless steel fixation material were confined to the posterior part of the neck on short TR/short TE MR images and did not interfere with the evaluation of the periodontoid region and the anterior part of the medulla/cervical cord. We found that flexion and extension lateral radiographs, combined with sagittal short TR/short TE MR images in the neutral position, enable preoperative evaluation of patients with rheumatoid arthritis in the cervical spine. Postoperative MR should be performed only if there are residual or new symptoms.     

脊髓多发性硬化的MRI诊断与鉴别诊断

目的　提高对脊髓多发性硬化MRI特征的认识。方法　对 15例脊髓多发性硬化患者行颈部MRI检查。对病变的位置、长度、横断面上病变大小及病变的强化进行评价 ,并与脊髓内肿瘤、脊髓型颈椎病、急性横贯性脊髓炎的MRI表现进行比较。结果　 15例脊髓多发性硬化主要发生在颈段脊髓 ,病变一般少于 5个椎体长度 ,MRI特点为矢状位脊髓局限性梭形增粗 ,边缘光滑。T1WI呈等或界限模糊的稍低信号 ,T2 WI呈长短不一的条形高信号。轴位像病灶位于脊髓侧方和后方 ,一般小于脊髓截面 1/2。活动期病灶呈条、片状强化 ,但强化区范围明显小于T2 高信号灶范围。反复发作病例多发病灶强化多样性 ,也可不强化。结论　脊髓多发性硬化有其特征性MRI表现 ,能为临床诊断提供可靠的依据     

Sequential gadolinium-DTPA enhanced MRI studies in neuro-Behçet's disease

Summary Sequential gadolinium-DTPA (Gd-DTPA) enhanced MR images were obtained before and after steroid therapy in a case of neuro-Behçet's disease. Multiple scattered lesions, which could not be detected on pre-and post-contrast CT, were demonstrated mainly in the white matter of the pons and/or the cerebrum with both T1-and T2-weighted images. Some of these lesions, however, were not enhanced at all by infusion of Gd-DTPA. The Gd-DTPA infusion study demonstrated marked enhancement in the white matter of the pons and cerebrum. Some lesions not seen with T2-weighted images were also strongly enhanced by Gd-DTPA infusion at the acute stage. After steroid therapy, the symptoms and abnormal laboratory findings were resolved. The pontine and cerebral lesions on plain MR images remained unchanged even after resolution of the symptoms, suggesting that they were inactive old foci. On the other hand, the lesions detected in the enhancement study before steroid therapy disappeared with the repeat Gd-DTPA enhanced MR images which were performed after resolution of the symptoms. Some active inflammatory lesions in, neuro-Behçet's disease may be demonstrated only on Gd-DTPA enhanced MR images. Gd-DTPA enhanced MR imaging appears to be potentially useful for detecting active inflammatory lesions in neuro-Behçet's disease and for evaluating the efficacy of treatment.     

Acoustic neuromas: Gd-DTPA enhancement in MR imaging

Magnetic resonance (MR) imaging examinations were performed in ten patients with 12 acoustic neuromas before and after intravenous administration of 0.1 mmol/kg body weight gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA). The degree of enhancement was greatest with the inversion recovery sequence 1,500/500/44 (repetition time [TR]/inversion time/echo delay time [TE]), followed by spin-echo (SE) 544/44 (TR/TE) sequences, then by SE 1,500/44 and SE 1,500/80 sequences. After enhancement there was a 50% reduction for measured T1 values, 33% for T2, and no significant change for proton density. There were no toxic effects on patients. Enhanced CT scans failed to demonstrate lesions in six of 12 cases. Air-CT technique improved sensitivity in four of five cases. Enhanced MR imaging added significant clinical information in two small intracanalicular tumors and in one recurrent tumor.     

Cervical spine: MR imaging with a partial flip angle, gradient- refocused pulse sequence. Part II. Spinal cord disease

A magnetic resonance imaging pulse sequence (GRASS) with a short repetition time (TR), short echo time (TE), partial flip angle, and gradient refocused echo was prospectively evaluated for the detection of cervical cord disease that caused minimal or no cord enlargement in eight patients. Sagittal T2-weighted, cerebrospinal fluid (CSF)-gated images and sagittal and axial GRASS images were obtained in all patients. The following GRASS parameters were manipulated to determine their effect on signal-to-noise ratio (S/N) and contrast: flip angle (4 degrees-18 degrees), TR (22-50 msec), and TE (12.5-25 msec). Flip angle had the greatest effect on S/N and contrast. There were no differences between axial and sagittal imaging for the spinal cord or lesion. However, because the signal intensity of CSF did differ on sagittal and axial images and because this influenced the conspicuity of lesions, there was a difference in the useful flip angle range for axial and sagittal imaging. No one set of imaging parameters was clearly superior, and in all patients, the gated image was superior to the sagittal GRASS image in lesion detection. GRASS images should be used in the axial plane primarily to confirm spinal cord disease detected on sagittal CSF-gated images. For this, a balanced approach is suggested (TR = 40 msec, TE = 20 msec, with flip angles of 4 degrees-6 degrees for sagittal and 6 degrees-8 degrees for axial imaging).     

快速FLAIR技术在椎管内病变MRI中的应用及价值

目的介绍快速FLAIR技术在椎管内病变MRI中的应用并评价其价值。方法用0．5T超导型MR扫描仪在常规T     

Dynamic 3DFT FISP MR imaging of hepatocellular carcinoma]

Dynamic 3 dimensional Fourier transformation (3DFT) FISP MR imaging was performed in 5 patients with hepatocellular carcinoma before partial hepatectomy. Immediately after 0.1 mmol/kg of Gd-DTPA was administered intravenously, 3DFT FISP images (TR/TE/flip angle/slice thickness, 20 msec/8 msec/30 degrees/2-4 mm) were obtained every 30 seconds until 150 sec. We correlated dynamic MR images of the 5 patients with gross and microscopic findings. Some regions in the tumor corresponding to viable cells showed high intensity enhancement and other regions corresponding to necrotic regions showed no enhancement on the early phase images. We concluded that dynamic 3DFT FISP MR imaging which had good spatial resolution was useful in evaluating the vascularity of the tumor.     

脊髓亚急性联合变性的MRI诊断要点分析

目的分析脊髓亚急性联合变性(SCD)的MRI诊断要点。资料与方法回顾性分析15例临床确诊SCD的病人临床及MRI资料,分析其脊髓MRI表现特点,统计分析SCD病人受累脊髓节段数与血清VB12水平、发病时间的相关性。结果 15例SCD病人均于横断面影像上显示颈胸段脊髓对称性等或长T1、长T2信号,13例病变主要位于颈胸段水平脊髓后索,2例同时累及后索、侧索及前索。但于横断面T2WI上颈段与胸段脊髓异常信号形态各具特点。颈段脊髓受累时于横断面T2WI上呈脊髓内"倒V"形或"反兔耳"形的对称性高信号。胸段脊髓受累时于横断面T2WI上呈脊髓内"哑铃"形的对称性高信号。统计学分析显示15例SCD病人脊髓受累节段数与血清VB12水平呈负相关,而与病程长短无相关性。结论脊髓MR成像对于SCD脊髓疾病的诊断有重要价值。     

巨噬细胞活性MRI对多发性硬化大鼠模型中枢神经系统病灶诊断价值的初步研究

目的 探讨巨噬细胞活性成像(MAI)对多发性硬化(MS)模型大鼠脑和脊髓病灶的诊断价值.方法 20只正常Lewis大鼠用数字表法随机分成实验组15只,对照组5只.应用髓鞘少突胶质细胞糖蛋白多肽35-55(MOG35-55)致敏实验组大鼠制备MS动物模型实验性自身免疫性脑脊髓炎(EAE),大鼠首次急性发病后第3天行MR检查.分别对大鼠脑和脊髓行T2WI、T1WI和Gd-DTPA增强T1WI的三维容积扫描.经大鼠尾静脉注入超微超顺磁性氧化铁(USPIO)24 h后行USPIO增强T2WI(即MAI).利用工作站专业软件获得大鼠脑和脊髓冠状面、横断面和矢状面的重组图像,并与常规图像进行比较.结果 成功建立MOG35-55-EAE模型大鼠15只.MOG35-55-EAE大鼠急性发病期相关的中枢神经系统病灶多数分布在脑内(58/63),少数位于脊髓(5/63).常规MRI上病灶表现为T2WI高信号、T1WI低信号,部分出现Gd-DTPA强化.在MAI图像上病灶呈低信号,部分USPIO强化病灶在T2WI上呈等信号,病灶的USPIO强化与Gd-DTPA强化表现不完全一致.T2WI(14/15)和MAI(13/15)对MOG35-55-EAE大鼠急性期病灶的敏感度高,两者联合对病灶的检出率高达100%(15/15),增强T1WI的敏感度相对较低(7/15).对照组大鼠MAI未见异常.结论 MAI弥补传统MR检查技术的不足,能监测EAE的炎症反应,与常规T2WI联合能提高MOG35-55-EAE大鼠病灶的检出率;Gd-DTPA增强能显示EAE血脑屏障破坏的早期活动性病灶,MAI与之联合成像对EAE病灶的诊断和监测有互补作用.     

Chronic cervical cord compression: clinical significance of increased signal intensity on MR images

Magnetic resonance (MR) imaging was performed in 668 patients with chronic compressive lesions of the cervical spinal canal. High signal intensity was observed within the spinal cord on T2-weighted or proton density spin-echo images in 99 patients (14.8%). Frequency of this finding was directly proportional to severity of clinical myelopathy and degree of spinal canal compression seen on MR images. Patients with a high-signal-intensity area responded less favorably than those without to surgical or medical treatment. More than 60% of the patients had this finding when grade of myelopathy or degree of canal compression was moderate to marked. Among 10 patients who received contrast material during MR imaging, one patient had definite enhancement and another had questionable enhancement in the high-signal-intensity area. The finding disappeared after decompressive surgery and medical treatment in some cases: Three of four of the patients who underwent surgery showed good clinical improvement. High signal intensity of the spinal cord produced by compressive lesions appears to be an important indicator for predicting prognosis.     

MR imaging and angiography of cerebral venous angiomas associated with brain tumors

Summary Cervical spinal cord lesions in the anterior spinal artery syndrome were delineated on magnetic resonance images (MRI) in four patients. The lesion was always seen anteriorly in the cervical cord. On T2-weighted images, the lesions appeared hyperintense relative to the normal spinal cord, while on T1-weighted images, two chronic lesions appeared hypointense, with local atrophy of the cord. In one case, repeated T1-weighted images showed no signal abnormality 4 days after the ictus, but the lesion became hypointense 18 days later, when contrast enhancement was also recognized after injection of Gd-DTPA; this sequence of intensity changes was similar to that of cerebral infarction. The extent of the lesion seen MRI correlated closely with neurological findings in all cases. Although the findings may not be specific, MRI is now the modality of choice for confirming the diagnosis in patients suspected of having an anterior spinal artery syndrome.     

Low flip angle gradient echo magnetic resonance imaging of the cervical spine at 0.3 tesla

The influence of flip angle and TR on signal to noise ratio and contrast between cerebrospinal fluid (CSF) and cord was evaluated in cervical spine imaging in 5 volunteers, using gradient echo technique. All experiments were performed on a 0.3 tesla Fonar beta-3000 M scanner using solenoidal surface coils. The most useful sequence was considered to be TR/TE = 300/12 ms and 10 degrees flip angle. This sequence provided images with a 'myelographic appearance' with good delineation of cord, CSF and epidural space. The grey and white matter was also regularly visualized. The acquisition time was considerably shorter than would have been necessary if a long TR/TE spin echo sequence had been used to obtain the same contrast pattern and the sequence was not as sensitive to motion as was the spin echo sequence. The sequence was also evaluated in 10 patients with degenerative disease and in 5 with lesions in the cord. The gradient echo sequence was found to be equal to or better than short and long TR/TE spin echo sequences in demonstrating narrowing of the spinal canal and cord lesion. The drawback is the limited signal to noise ratio.     

MR imaging features of medulloblastomas.

The preoperative MR studies of 25 patients with surgically proved medulloblastomas were retrospectively reviewed in order to characterize these neoplasms with regard to their MR signal intensity, size, location, and appearance after contrast enhancement. Gadopentetate dimeglumine--enhanced MR images were available in 11 patients. On short TR/short TE images, medulloblastomas generally had low to intermediate signal, and were predominantly slightly hyperintense relative to muscle and hypointense relative to white matter. On long TR/long TE images, medulloblastomas generally had intermediate to moderately high signal, predominantly hyperintense relative to muscle and white matter. Tumor signal relative to gray matter varied considerably on both short TR and long TR images. Signal heterogeneity on long TR/long TE images was observed in 91% of the lesions and resulted from intratumoral cystic zones, small blood vessels, and/or calcifications. In the patients who received gadopentetate dimeglumine, the fraction of tumor volume showing enhancement was found to be less than one third in two cases, between one third and two thirds in four cases, and greater than two thirds in five cases. The mean tumor size was 3.6 x 4.0 x 3.5 cm. The most frequent location of medulloblastoma was the mid and inferior vermis. We conclude that the unenhanced and enhanced MR characteristics of medulloblastomas are somewhat variable. Medulloblastomas should be included in the differential diagnosis when the MR findings described are present in the appropriate patient population.