Magnetic resonance imaging of intracranial neoplasms at 0.02 tesla

Sixty-five patients with single or multiple intracranial neoplasms were examined with an MR imager operating at 0.02 tesla. In 56 patients the diagnosis was histologically confirmed. All patients had an abnormal CT finding. MR images were positive in 59 cases, while the lesion remained undetected or equivocal in 6 cases (2 pituitary adenomas and 4 meningiomas). The MR signal intensity of several meningiomas was equal to that of normal brain tissue. Some astrocytomas were better delineated on MRI than on CT. For the study of pituitary lesions, the spatial resolution was unsatisfactory. The ultralow field MR imager was found to be sensitive for the detection of other intracranial neoplasms.     

Evaluation of acquired cholesteatoma with PROPELLER diffusion imaging

Purpose

Was to evaluate the role of periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) diffusion imaging in evaluation of middle ear acquired cholesteatomas (primary and recurrent) and differentiating them from middle ear granulation tissue.

Patients and methods

Forty two patients with suggested acquired cholesteatomas were included in this prospective study, they underwent spiral CT and MRI (PROPELLER diffusion) for all. The two radiologist analyzed the imaging data of plain spiral CT and PROPELLER diffusion MR images. Sensitivity and specificity were assessed. Results were compared with endoscopic and surgical results, which were regarded as the standard reference.

Results

Ten patients had middle ear granulation tissue, 21 patients had acquired primary cholesteatomas, and 11 patients had acquired recurrent (post operative) cholesteatomas. PROPELLER diffusion MR successfully diagnosed and differentiated between granulation tissue and cholesteatomas (primary and recurrent. Sensitivity (lesions detection) and specificity (lesions characterization) of PROPELLER diffusion MR was 100%. In recurrent cholesteatomas, plain CT detected abnormal densities without any differentiation resulting in 0% specificity while in primary cholesteatomas, CT successfully diagnosed them based on associated bone erosions/destruction.

Conclusion

PROPPLER diffusion Imaging is both sensitive and specific for detection and characterization of primary and recurrent cholesteatomas as it lack susceptibility and chemical-shift artifacts, and ghosts in the phase-encoding direction which occur in Echo-planar diffusion, it can detect small cholestatoma as 3 mm. It provides the highest sensitivity, specificity for detection and characterization of acquired cholesteatomas.     

颅内原发恶性淋巴瘤的MRI诊断(附12例报告)

目的　探讨颅内原发恶性淋巴瘤CT及MR的表现特征 ,以提高诊断准确率。方法　对 12例经手术病理证实的颅内原发恶性淋巴瘤的CT及MR表现进行回顾分析。结果　共检出 3 2个病灶 ,其中单发 9例 ,分别位于额、颞、顶叶深部脑白质 8例 ,位于颞叶表面 1例 ;多发 3例 ,病灶多位于深部脑白质。CT多表现为圆形或类圆形稍高密度灶 ,MRI表现为T1WI低或等信号 ,T2 WI为稍低信号。多数病灶周围有轻 -中度高信号水肿带 ,病灶边界尚清楚。增强扫描见所有病灶均有强化 ,2 3个 ( 72 .0 % )病灶呈均匀强化 ,18个 ( 5 6.2 5 % )病灶强化后出现缺口或凹陷改变。病理结果 :11例为非何杰金氏淋巴瘤 ,1例为浆细胞淋巴瘤。结论　尽管颅内原发恶性淋巴瘤的影像表现与其它颅内肿瘤如脑膜瘤、胶质瘤及转移瘤等有许多相似之处 ,但通过认真分析其影像特征 ,术前的正确诊断是有可能的     

CT, MR, and pathology in HIV encephalitis and meningitis

The value and limitations of CT and MR in human immunodeficiency virus (HIV) infection of the brain was determined by a retrospective analysis of the CT scans (22) and MR images (7) in 22 patients with pathologically proved HIV encephalitis (21) or meningitis (1). Our clinical-radiologic-pathologic correlation suggested that, especially in the early stages of the disease, CT and MR were relatively insensitive in detecting the primary changes of HIV encephalitis. The multiple bilateral diffuse microscopic glial nodules with multinucleated giant cells of HIV found at autopsy in both gray and white matter were usually not directly visualized by either CT or MR. Secondary, nonspecific changes, however, were seen. These included cortical atrophy, found in virtually all patients with HIV encephalitis, and HIV-induced foci of demyelination found in the minority of cases. On CT the latter were seen in the white matter as nonenhancing, nonmass-producing areas of low density; on MR they were seen as frequently progressive high-intensity signal abnormalities on T2-weighted images, usually in the periventricular white matter and centrum semiovale. MR was more sensitive in detecting these demyelinative lesions than was CT. The clinical diagnosis of HIV encephalitis usually antedated the radiographic diagnosis. In HIV meningitis, contrast CT was more definitive than MR, showing striking enhancement of the subarachnoid spaces, although MR was more sensitive in detecting the secondary parenchymal changes.     

Magnetic resonance in multiple sclerosis

Summary Magnetic Resonance Imaging was performed in more than 200 patients with clinical suspicion or knowledge of Multiple Sclerosis. One hundred and forty-seven (60 males and 87 females) had MR evidence of multiple sclerosis lesions. The MR signal of demyelinating plaques characteristically has prolonged T1 and T2 relaxation times and the T2-weighted spin-echo sequences are generally superior to the T1-weighted images because the lesions are better visualized as areas of increased signal intensity. MR is also able to detect plaques in the brainstem, cerebellum and within the cervical spinal cord. MR appears to be an important, non-invasive method for the diagnosis of Multiple Sclerosis and has proven to be diagnostically superior to CT, evoked potentials (EP) and CSF examination. In a selected group of 30 patients, with the whole battery of the relevant MS studies, MR was positive in 100%, CT in 33,3%, EP in 56% and CSF examination in 60%. In patients clinically presenting only with signs of spinal cord involvement or optic neuritis or when the clinical presentation is uncertain MR has proven to be a very useful diagnostic tool for diagnosis of MS by demonstrating unsuspected lesions in the cerebral hemispheres.     

Intracranial vascular malformations: MR and CT imaging

Twenty-four patients with 29 cerebrovascular malformations were evaluated with a combination of computed tomography (CT), angiography, and magnetic resonance (MR) imaging. Characteristics of the malformations on MR images were reviewed retrospectively, and a comparative evaluation of MR and CT images was made. Of 14 angiographically evident malformations, 13 intra-axial lesions were detected on both CT and MR images, and one dural malformation gave false-negative results on both modalities. The appearance of parenchymal lesions on MR images closely mirrored characteristic CT findings. Calcific foci were difficult to separate from vessels on both images. Clot was more easily identified on MR images. In the detection of 15 angiographically occult malformations, CT proved more sensitive when focal calcification was the only evidence of their presence. MR study failed to detect two small supratentorial lesions evidenced by faint calcifications on CT scans. In two patients, MR images showed small hemorrhages not detectable by CT, and MR provided strong evidence for the diagnosis of hematoma for 12 lesions. Angiographically evident malformations have a highly characteristic appearance on MR images. MR may be more sensitive than CT in the detection of small hemorrhagic foci associated with cryptic arteriovenous malformations and may add specificity in the diagnosis of occult malformations in some cases, but MR is less sensitive than CT for the detection of small calcified malformations.     

Tuberous sclerosis: characteristics at CT and MR imaging

Computed tomography (CT) and magnetic resonance (MR) imaging findings were reviewed in 26 patients with tuberous sclerosis. All patients underwent CT; 16 patients underwent both. The CT features included subependymal nodules in 25 of 26 patients (96%) and calcifications in 23 of 26 (88%). Parenchymal hamartomas (cortical tubers) were seen in 23 of 26 patients (88%). These lesions had less attenuation than surrounding brain in 16 of 26 patients (62%) and were calcified in 14 of 26 patients (54%). Contrast enhancement of a lesion, indicating a subependymal giant cell astrocytoma, occurred in three of 26 patients (12%). The MR imaging characteristics included subependymal nodules (periventricular nodules) of intermediate signal intensity in ten of the 16 patients (63%). Parenchymal hamartomas, demonstrated in 15 of the 16 patients (94%), usually exhibited long T1 and T2 relaxation characteristics. The pattern was noted to be reversed in the two newborn patients (13%). One parent demonstrated a forme fruste at CT but had a normal MR image.     

Orbital tumors in children: CT and MR imaging features

The purpose of the article is to review the CT and MR imaging features of orbital tumors in children. Tumors in children are usually different than those in adults. Clinical symptoms are usually non-specific. Clinical examination combined with US may be sufficient for diagnosis and follow-up of benign and superficial lesions. CT and/or MRI are needed for deep or malignant lesions. CT is valuable for osseous and/or calcified lesions. MR is advantageous because of its superior spatial resolution and non-ionizing nature. Malignant tumors correspond to about 20% of lesions and include primary tumors (retinoblastoma, rhabdomyosarcoma) and metastases. Benign pathology is more frequent (80%) with dermoid cyst corresponding to about 50% of orbital masses.     

Prospective comparative study of intermediate-field MR and CT in the evaluation of closed head trauma

Forty patients with closed head trauma were evaluated prospectively with CT and intermediate-field-strength MR imaging to compare the diagnostic efficacies of the two techniques. Traumatic lesions were detected in 38 patients. The severity of injury, as determined by the Glascow Coma Scale, ranged from 3 to 14. The sensitivities of CT and MR were calculated for all subgroups of lesions: (1) hemorrhagic and nonhemorrhagic intraaxial lesions (diffuse axonal injury, cortical contusion, subcortical gray-matter injury, primary brainstem injury); (2) extraaxial hematomas (subdural, epidural); and (3) diffuse hemorrhage (subarachnoid, intraventricular). CT and MR (T1- and T2-weighted) studies were both highly and comparably sensitive in the detection of hemorrhagic intraaxial lesions. MR scans, however, were much more sensitive in detecting nonhemorrhagic lesions. cortical contusions and diffuse axonal injury constituted 91.9% of all intraaxial lesions. The sensitivities of the imaging techniques for this combined group of lesions were (1) nonhemorrhagic lesions (CT = 17.7%, T1-weighted MR = 67.6%, T2-weighted MR = 93.3%); (2) hemorrhagic lesions (CT = 89.8%, T1-weighted MR = 87.1%, T2-weighted MR = 92.5%). MR was also significantly better in detecting brainstem lesions (CT = 9.1%, T1-weighted MR = 81.8%, T2-weighted MR = 72.7%). The sensitivities of the diagnostic studies in the detection of extraaxial hematomas were CT = 73.2%, T1-weighted MR = 97.6%, T2-weighted MR = 90.5%). Intraventricular hemorrhage was consistently seen with all three imaging studies, but subarachnoid hemorrhage was detected much more frequently with CT. In summary, MR has clear advantages over CT in evaluating closed head trauma. Although its sensitivity in detecting hemorrhagic lesions is similar to that of CT, it is much better than CT in detecting nonhemorrhagic lesions, which are more prevalent. MR is more useful than CT in classifying primary and secondary forms of injury and directing treatment. CT's one advantage over MR is its ability to more rapidly assess unstable patients who may need surgery.     

Optic nerve sheath meningiomas. Role of MR imaging

Optic nerve meningiomas usually are seen in middle-aged and elderly women, and present as a slowly progressing axial proptosis and loss of vision. CT and MR imaging are the most valuable diagnostic tools to evaluate these tumors. This article reviews the MR imaging and CT characteristics of optic nerve sheath meningiomas and discusses features that may distinguish optic nerve sheath meningiomas from simulating lesions.     

MR and CT evaluation of intracranial sarcoidosis

Fourteen patients with CNS manifestations of neurosarcoidosis were evaluated by MR imaging and CT. Evaluations were done on a 0.5-T superconductive magnet with T1- and T2-weighted sequences. CT with contrast was obtained in all patients. The granulomatous lesions were classified by location into basilar, convexity, intrahemispheric, and periventricular white-matter involvement. Hydrocephalus with or without an associated lesion was also noted. MR determined the presence of disease in all patients (100%), but was less accurate than CT in depicting disease in two patients (14%). CT determined the presence of disease in 12 patients (85%) and was less accurate than MR in delineating hypothalamic involvement in two patients and periventricular white-matter disease in three patients. There was great variability in the appearance of intracranial sarcoidosis on MR. Three patients had lesions that were isointense or hypointense (relative to cerebral cortex) on both T1- and T2-weighted images while nine patients had lesions that were hyperintense on T2-weighted images. Convexity involvement and hydrocephalus were well documented by both CT and MR. These results indicate that both MR and CT are helpful in fully evaluating a patient with suspected intracranial sarcoidosis.     

Diagnosis of small hepatocellular carcinoma: correlation of MR imaging and tumor histologic studies

Magnetic resonance (MR) images of the liver were used to study 43 patients with relatively small hepatocellular carcinomas (HCCs) and 36 with other hepatic mass lesions. In 27 HCC patients, histologic findings were available. All focal lesions detectable by CT without contrast media were delineated with greater contrast by MR imaging. The rate of detection depended on tumor size, being 97.5% for HCCs greater than 2 cm in the longest axis and 33.3% for those less than 2 cm. MR imaging demonstrated the ring sign characteristic of encapsulated HCC twice as frequently as CT scans. Inversion recovery (IR) images depicted the internal structure of the HCC better than T2-weighted spin-echo images. Lesions were classified into four patterns of intensity: low, iso, high, and mixed. The latter three were relatively characteristic of HCC and related closely with steatosis of cancer tissue. HCCs with fibrosis tended to have long T1 values; those with steatosis had short T1 values. T1 and T2 relaxation times were useful in the differential diagnosis.     

Brain radiation lesions: MR imaging

This retrospective study was performed to assess the capability of magnetic resonance (MR) to depict and characterize diffuse and focal radiation lesions in the brain using the spin-echo technique. The MR images of 55 patients who had undergone radiation therapy were reviewed. Comparative computed tomography (CT) studies were available for all the patients. Normal white matter was chosen as reference tissue for the quantitative comparison of signal intensities. Radiation lesions (identified in eight patients) were seen as regions of high signal intensity on the sequence with a long repetition time (TR) (2.0 sec) and showed no difference in signal compared with white matter when the TR was short (0.5 sec). Nonspecific prolongation of T1 and T2 relaxation times was measured in such lesions. In one patient, subependymal tumor spread, demonstrated by contrast-enhanced CT, was missed on MR images, masked by the adjacent abnormal signal owing to radiation effects. Recurrent or residual brain tumor could not be distinguished from radiation brain necrosis either by CT or by MR imaging. It is concluded that MR can depict radiation lesions with great sensitivity but is not very helpful for discrimination between recurrent or residual brain tumor, radiation necrosis, and other brain lesions.     

Eosinophilic hepatic necrosis: magnetic resonance imaging and computed tomography comparison

OBJECTIVE: To compare the findings of magnetic resonance (MR) imaging with those of computed tomography (CT) of focal liver lesions related to peripheral eosinophilia. METHODS: For 12 patients with peripheral eosinophilia (>7%) examined with hepatic MR imaging and CT, 52 focal hepatic lesions larger than 0.5 cm, including 31 lesions simultaneously found on the 2 imaging modalities, were subjected to a comparative analysis of their imaging features. RESULTS: The total number of lesions distinguished from background liver was 39 (75%) on MR imaging and 44 (85%) on CT scans. On arterial phase images of 10 patients with comparable data, homogeneously hyperintense lesions were demonstrated more frequently (P = 0.006) on MR imaging (16 [50%] of 32 lesions) than on CT scans (4 [13%] of 32 lesions). Only 7 (22%) of the 32 hypoattenuating lesions on portal phase CT were depicted as hypointense lesions on portal phase MR images in 12 patients. On delayed phase images in 8 patients, the number of hyperintense lesions on MR images (9 [56%] of 16) was greater (P = 0.077) than that seen on the CT scans (4 [25%] of 16). CONCLUSIONS: For many focal hepatic lesions related to peripheral eosinophilia, dynamic MR imaging more easily demonstrates lesional enhancement on arterial and delayed phases than CT scans. Because of the higher degree of lesional enhancement of MR imaging compared with CT, the lesion-to-liver contrast may not be sufficient to distinguish the lesion from the background liver, resulting in decreased sensitivity of portal phase dynamic MR imaging.     

Traumatic brain stem injury: MR imaging

Eighty-seven patients with acute (n = 70) or chronic (n = 17) head injuries were prospectively studied with magnetic resonance (MR) imaging and computed tomography (CT) to characterize the frequency and nature of traumatic brain stem injury (BSI). Forty-eight traumatic lesions were identified in 36 patients. Of 36 patients, 35 had neurologic findings that corroborated the radiographic impression of BSI. T1- and T2-weighted MR images demonstrated a significantly higher number of lesions than did CT. Patients with BSI had a significantly higher frequency of corpus callosum and diffuse axonal "shear" lesions. The number of cortical contusions and extraaxial hematomas was similar in both groups. The mean Glasgow Coma Scale (GCS) scores at admission were significantly lower in patients with evidence of BSI on MR images. Patients with primary BSI had lower initial GCS scores, a longer duration of coma, more diffuse axonal "shear" lesions, and a higher frequency of corpus callosum injury than patients with secondary BSI. The location of primary and secondary lesions was significantly different. Overall, MR imaging was more helpful than CT in detecting, localizing, and characterizing BSI.     

MR imaging of Hallervorden-Spatz disease

Hallervorden-Spatz disease (HSD) is a movement disorder with neuropathology including abnormal iron storage, disordered myelination, and loss of brain substance. Cranial magnetic resonance (MR) imaging of two patients with HSD provided good quality imaging of these patients' atrophic brain stems and cerebella, regions partially degraded by beam-hardening artifact on X-ray CT. Magnetic resonance also demonstrated signal aberrations in the lentiform nuclei and surrounding white matter consistent with iron storage or disordered myelination. However, quantification of relaxation times of these lesions was not specific for either process. The diagnosis of HSD remains one of exclusion, with MR providing helpful but not definitive information.     

Orbit: initial experience with surface coil spin-echo MR imaging at 1.5 T

Fifty-nine cases in which surface coil MR imaging of the orbit was performed were reviewed. MR imaging was performed with spin-echo techniques at 1.5 T with both short repetition time/echo time (TR/TE) and long TR/TE sequences in all cases. In all patients short TR/TE images were obtained with small-diameter surface coils; long TR/TE images were usually obtained with a standard head coil. Surface coil MR appears to be an important adjunct in state-of-the-art orbital imaging. Orbital MR imaging may be most useful, providing information not available on computed tomography (CT), in identifying lesions in the orbital apex, superior orbital fissure, and optic canal; differentiating inflammatory pseudotumor from malignancy in clinically similar patients; characterizing lesions containing hemorrhage or other paramagnetic material; defining the posterior extent of optic pathway gliomas; and detecting abnormal flow in intraorbital vascular structures. CT seems to be superior to MR imaging in the evaluation of small perioptic meningiomas, especially those that are calcified.     

Hemangioma in the cirrhotic liver: diagnosis and natural history

PURPOSE: To investigate the natural history and diagnosis of cavernous hemangioma in the cirrhotic liver with computed tomography (CT) and magnetic resonance (MR) imaging. MATERIALS AND METHODS: Imaging and pathologic findings of 21 hemangiomas in 17 patients were retrospectively reviewed. CT of the liver was performed in all patients; MR imaging, in four. Cirrhosis was confirmed histologically in all patients, and the diagnosis of hemangioma was based on histopathologic findings (15 patients, 18 hemangiomas) or strict imaging criteria (two patients, three hemangiomas). Ten patients underwent imaging follow-up. The number, sizes, location, attenuation, pattern of enhancement, exophytic growth, presence of capsular retraction, and size stability were evaluated. RESULTS: Of the 21 hemangiomas, five were not detected at CT or MR imaging. Twelve (75%) of 16 hemangiomas were subcapsular, two (12%) of 16 demonstrated exophytic growth, 14 (87%) of 16 demonstrated nodular peripheral enhancement, and 16 (100%) of 16 were isoattenuating to blood vessels. At MR imaging, all five hemangiomas demonstrated nodular peripheral enhancement and hyperintensity on T2-weighted images. Seven lesions were smaller at follow-up, and five lesions developed retraction of the hepatic capsule. CONCLUSION: Even within the cirrhotic liver, larger hemangiomas can usually be diagnosed confidently with CT or MR imaging. With progressive cirrhosis, however, hemangiomas are likely to decrease in size, become more fibrotic, and are difficult to diagnose radiologically and pathologically.     

Preoperative Evaluation of Cervical Radiculopathy and Myelopathy by Surface-Coil MR Imaging

During a 2-year period, 256 patients were screened for cervical radiculopathy and myelopathy with surface-coil MR images and plain films. Selected patients had follow-up examinations including CT, myelography, and CT myelography. Thirty-four of these patients underwent cervical spine surgery after MR imaging, which disclosed a total of 50 abnormalities in three major categories: herniated disks, bony canal stenoses, and intradural lesions. MR correctly predicted 88% of all surgically proved lesions compared with 81% for CT myelography, 58% for myelography, and 50% for CT. Missed herniated disks on either MR or CT myelography usually were the result of technically suboptimal studies caused by motion artifacts on MR and beam-hardening artifacts on CT myelography. Small osteophytes adjoining herniated disks sometimes were not predicted on MR, although such osteophytes invariably were seen on plain films and were palpable during standard anterior cervical diskectomy procedures. Herniated disks in the lateral root canals found in two patients appeared to be detected more readily by CT myelography than by MR. All proved lesions were detected by either screening MR images and plain films or by follow-up CT myelograms. MR replaced invasive evaluations by myelography and CT myelography in 32% of preoperative patients.We conclude that MR images, combined with plain films, offer an accurate, noninvasive test for the preoperative evaluation of cervical radiculopathy and myelopathy, while CT myelography is the preferred follow-up examination.     

Diagnosis of acute cerebral infarction: comparison of CT and MR imaging.

The appearance of acute cerebral infarction was evaluated on MR images and CT scans obtained in 31 patients within 24 hr of the ictus; follow-up examinations were performed 7-10 days later in 20 of these patients and were correlated with the initial studies. Acute infarcts were visible more frequently on MR images than on CT scans (82% vs 58%). Proton density- and T2-weighted scans usually demonstrated regions of hyperintensity corresponding to acute infarcts, but proton density-weighted scans often showed better definition of the lesion in terms of regional anatomy. Follow-up MR images and CT scans identified approximately 88% of subacute strokes, 54% of which were better defined and/or larger than on the initial examination. In 20% of lesions, "hemorrhagic" characteristics were seen on at least one examination. CT and MR imaging were comparable in delineating acute hemorrhage, but MR detected more cases with evidence of hemorrhage on follow-up examinations. MR appears to be more sensitive than CT in the imaging of acute stroke.