Focal nodular hyperplasia of the liver: MR imaging and pathologic correlation in 37 patients.

Thirty-seven patients with 48 lesions of focal nodular hyperplasia (FNH) underwent preoperative magnetic resonance (MR) examination and surgical resection. Sixteen lesions were imaged at 0.5 T with T1- and T2-weighted spin-echo sequences; 32 lesions were imaged at 2 T with T1-and T2-weighted spin-echo and gradient-recalled-echo sequences. Contrast material-enhanced MR imaging was performed in 20 lesions. MR imaging failed to depict six tumors that were less than 3 cm in diameter. Typical appearance was present in 18 of the 42 (43%) lesions seen at MR. Atypical lesion features included no scar (n = 15), hypointense scar on T2-weighted images (n = 7), pseudocapsule (n = 6), strong hyperintense lesion on T2-weighted images (n = 3), diffuse hyperintensity on T1-weighted images (n = 3), and heterogeneous lesion (n = 1). Comparison between findings at MR imaging and at histopathologic examination was performed in 38 lesions: There was good correlation between presence and size of the scar on both examinations. In 13 of 20 (65%) of the hyperintense scars on T2-weighted images, edema was prominent, whereas in five of the seven (71%) hypointense scars on T2-weighted images, edema was absent or low.     

Intraocular tumors: evaluation with MR imaging

Sixty-seven ocular tumors were studied with magnetic resonance (MR) imaging and computed tomography (CT). These tumors included primary uveal melanoma (n = 55), circumscribed choroidal hemangioma (n = 3), diffuse choroidal hemangioma (n = 1), retinal capillary hemangioma (n = 1), medulloepithelioma (n = 1), choroidal nevus (n = 1), retinoblastoma (n = 1), and choroidal metastases (n = 4). MR imaging demonstrated all these lesions, while CT demonstrated 88%. Associated retinal detachment was more easily distinguished from the neoplasms with MR imaging. Extrascleral extension of melanoma and hemorrhagic cystic necrosis within the melanoma were clearly demonstrated with MR imaging, but not with CT. Ninety-three percent of melanomas were markedly hyperintense, compared with the intensity of the vitreous body, on T1-weighted images and hypointense on T2-weighted images. All metastatic lesions were isointense on T1-weighted images and hypointense on T2-weighted images. The circumscribed choroidal hemangiomas were hyperintense on T1-weighted images and isointense on T2-weighted images. MR imaging is superior to CT in detection of intraocular tumors and may be more specific in diagnosis.     

Diffusion-weighted MR imaging offers no advantage over routine noncontrast MR imaging in the detection of vertebral metastases

BACKGROUND AND PURPOSE: Diffusion-weighted MR imaging of the spine has been used to differentiate benign from pathologic vertebral body compression fractures. We sought to determine the utility of diffusion-weighted MR imaging in the detection of vertebral metastases and to compare it with conventional noncontrast T1- and T2-weighted MR imaging. METHODS: Fifteen patients with metastases to the spine were studied using conventional MR imaging and diffusion-weighted imaging. Blinded review of all images was undertaken, and patients were categorized according to whether they had focal or multiple lesions. The signal intensity of the lesions was compared on T1-, T2- (fast spin-echo), and diffusion-weighted images. RESULTS: In five patients with focal disease, metastases were hypointense on T1-weighted images; hypointense (n = 2), isointense (n = 1), or hyperintense (n = 2) on T2-weighted images; and hypointense (n = 3) or hyperintense (n = 2) on diffusion-weighted images with respect to presumed normal bone marrow. In 10 patients with disease in multiple sites, all lesions were hypointense on T1-weighted images; hypointense (n = 2), isointense (n = 4), hyperintense (n = 2), or mixed (n = 2) on T2-weighted images; and hypointense (n = 5), hyperintense (n = 3), or mixed (n = 2) on diffusion-weighted images with respect to presumed normal bone marrow. CONCLUSION: As used in this study, diffusion-weighted MR imaging of the spine showed no advantage in the detection and characterization of vertebral metastases as compared with noncontrast T1-weighted imaging, but was considered superior to T2-weighted imaging.     

Adenomatous hyperplastic nodules in the cirrhotic liver: differentiation from hepatocellular carcinoma with MR imaging

Differentiation of hepatocellular carcinomas from adenomatous hyperplastic nodules (AHNs) is important for the early and precise detection of hepatocellular carcinoma in the cirrhotic liver. For this purpose, the authors compared findings on magnetic resonance (MR) images of surgically resected AHNs (n = 7) with those of hepatocellular carcinoma (n = 47). AHNs were divided into two histologic groups: those without atypia (n = 5) and those with atypical hepatocytes or malignant foci (n = 2). All AHNs without atypia were hyperintense on T1-weighted spin-echo images and hypointense on T2-weighted spin-echo images relative to the surrounding liver. However, almost all hepatocellular carcinomas, except for two lesions with massive coagulation necrosis, were demonstrated as hyperintense on T2-weighted images. MR imaging may be useful in the differentiation of AHN without atypia from hepatocellular carcinoma in the cirrhotic liver.     

Fibrolamellar hepatocellular carcinoma: imaging and pathologic findings in 31 recent cases.

PURPOSE: To review characteristic findings of fibrolamellar hepatocellular carcinoma (HCC) at computed tomography (CT) and magnetic resonance (MR) imaging. MATERIALS AND METHODS: The authors retrospectively reviewed the clinical, pathologic, and preoperative imaging findings in 31 patients with histologically proved fibrolamellar HCC. Dynamic contrast material-enhanced CT of the liver was performed in 31 patients, helical multiphase CT in 21, and MR imaging in 11. Complete resection was performed in 17 patients, and imaging-pathologic correlation was performed. RESULTS: Large tumors (mean diameter, 13 cm) were depicted at CT and MR in all cases. At CT, the margins of the tumors were well defined in 24 (77%) of 31 cases calcifications were depicted in 21 (68%), a central scar in 22 (71%), and abdominal lymphadenopathy in 20 (65%). In 20 (80%) of 25 cases with hepatic arterial phase CT images, all tumors were heterogeneous and depicted areas of hypervascularity. At MR imaging, tumors were hypointense to liver on T1-weighted images (n = 11) and hyperintense to liver on T2-weighted images (n = 10). Calcification was not depicted on MR images, but a central scar was depicted as hypointense to surrounding tumor in nine cases. CONCLUSION: CT and MR images demonstrate characteristic features that may allow confident diagnosis of fibrolamellar HCC.     

CT and MR imaging of advanced Zollinger-Ellison syndrome

The CT and magnetic resonance (MR) findings in 13 patients with advanced Zollinger-Ellison syndrome are described. In eight patients (62%) one or more primary tumors were found with both methods. All patients with proven liver metastases (n = 7) were identified by MR. Computed tomography was positive in six of these patients. Three patients with lymph node metastases were identified on CT and MR and one patient had bone metastases. Computed tomography and MR were inferior to selective arteriography in the detection of multiple lesions of the pancreas in a patient with multiple endocrine neoplasia-I syndrome. On the T1-weighted MR images, the primary tumors demonstrated no consistency with regard to their signal intensity relative to the adjacent pancreatic parenchyma. All gastrinomas had an increased relative signal intensity on the T2-weighted images with the exception of a calcified tumor. Liver and lymph node metastases had a low signal intensity on the T1-weighted images and an increased signal intensity on the T2-weighted images. The signal intensity of primary tumors and metastases was independent of size. In conclusion, MR was able to detect abnormalities based on its outstanding lesion/normal tissue contrast, whereas CT diagnosis was based mostly on contour distortion. For the current technique, MR is considered at least equal to CT.     

Epithelioid hemangioendothelioma of the liver: MR and CT findings.

The MR imaging features in five patients with hepatic epithelioid hemangioendothelioma (EHE) were correlated with CT and pathologic findings. Two hemangioendotheliomas appeared as multiple nodular lesions with a predominantly peripheral location in the liver. In three more extensive cases, the tumors formed confluent peripheral lesions with macroscopic invasion of portal or hepatic veins (n = 3), signs of portal hypertension (n = 3), and nodular hypertrophy of uninvolved liver (n = 2). These findings, suggestive of EHE, were well demonstrated by MR imaging and CT. The internal architecture of the tumors was clearly depicted on T2-weighted MR images. Viable tumor peripheries appeared moderately hyperintense relative to liver. The center of the tumors consisted of one or several concentric zones. Hyperintense central zones were composed of loose, edematous connective tissue. Hypointense zones contained mainly coagulation necrosis, calcifications, and scattered hemorrhages. Except for the presence of calcifications, the internal architecture of EHE was better defined by MR imaging than by CT.     

MRI of musculoskeletal extraspinal tuberculosis

PURPOSE: The aim of this study was to describe the MR findings in extraspinal musculoskeletal tuberculosis (EMT). METHOD: A retrospective review was conducted of the MR findings of 18 patients with microbiologically and/or pathologically proven EMT. All MR studies were performed using T1-and T2-weighted spin echo sequences. T1-weighted spin echo sequences after Gd-DTPA injection were obtained for 12 patients. The MR images were evaluated for abnormalities in joints, bones, and soft tissues, and the results were grouped by anatomic localization, frequency distribution of structures affected, and morphologic patterns of involvement. RESULTS: Isolated soft tissue tuberculosis was found in 10 (55.5%) patients and involvement of more than one structure in 8 (44.4%). Pyomyositis (n = 6) and arthritis with involvement of adjacent soft tissues (n = 7) were the most common forms of presentation. One patient presented with isolated fascial superficial tissue involvement in one leg. Isolated pyomyositis involving one (n = 3) or two (n = 3) muscles was homogeneous in six cases and showed intermediate (n = 6), low (n = 2), or high (n = 1) signal intensity on T1-weighted images and a high and very hyperintense signal on T2-weighted images. The tenosynovitis synovial fluid was homogeneous (n = 1) or heterogeneous with multiple tiny hypointense nodules (n = 1) on T2-weighted images. The subdeltoid bursitis fluid was characterized by homogeneous low signal intensity with a hyperintense rim (n = 2) on T1-weighted images and homogeneous (n = 1) or heterogeneous hyperintense signals with areas of low signal intensity (n = 1) on T2-weighted images. In tuberculous arthritis, the synovial joint fluid (n = 7) showed heterogeneous (n = 4) or homogeneous (n = 3) low signal intensity on T1-weighted images and high or very high signal intensity on T2-weighted images. Where involved, the adjacent muscle(s) (n = 8) were usually hypointense on T1-weighted images and very hyperintense on T2-weighted images. Associated cellulitis was found in arthritis with involvement of neighboring soft tissues (n = 5), pyomyositis (n = 2), and tenosynovitis (n = 1). The images obtained after Gd-DTPA showed peripheral (n = 10) or heterogeneous (n = 1) enhancement or no enhancement (n = 1). CONCLUSION: The MR findings for EMT are variable. Although diagnosis is dependent largely on prior presumption and clinical context, MRI provides valuable guidelines in defining the extent of the lesions to select the appropriate treatment and for follow-up of abnormalities.     

Pyogenic hepatic abscesses: MRI findings on T1- and T2-weighted and serial gadolinium-enhanced gradient-echo images

The purpose of this study was to determine the magnetic resonance imaging (MRI) features of pyogenic hepatic abscesses on T1-weighted, T2-weighted, and serial gadolinium (Gd)-enhanced T1-weighted spoiled gradient-echo (SGE) images including images acquired in the immediate, intermediate, and late phases of enhancement. The MRI studies of 20 patients with pyogenic liver abscesses were retrospectively reviewed. All patients were examined on 1.5 (n = 19) and 1.0 (n = 1) T MR scanners. MR studies included T1-weighted, T2-weighted, and serial Gd-enhanced SGE images. The following determinations were made: signal intensity of the abscess cavity and perilesional liver tissue, and the presence of internal septations, layering material, or air in the abscess cavity. The pattern of enhancement of the abscess wall, internal septae and peri-abscess liver were evaluated on serial Gd-enhanced SGE images. A total of 53 abscesses were observed in the 20 patients. Fortyeight abscesses were hypointense on T1-weighted and hyperintense on T2-weighted images. Internal septations were present in four abscesses. Lower signal intensity material was observed in a dependent location on T2-weighted images in one abscess. Signal void foci of air located on the nondependent surface was observed in two abscesses. Two other abscesses contained signal void air that occupied the entire abscess cavity, observed on all imaging sequences. On serial gadolinium-enhanced images, all abscesses revealed early enhancement of the wall, which persisted with negligible change in degree of enhancement or thickness on delayed images. Abscess walls ranged in thickness from 2 to 5 mm. Internal septations ranged in thickness from 2 to 3 mm. Abscess walls and septations were relatively uniform in thickness with no evidence of focal nodularity. Periabscess liver tissue was mildly hypointense on T1-weighted and mildly hyperintense on T2-weighted images in 20 lesions, which were either circumferential (n = 12) or wedge-shaped (n = 8). All these regions enhanced more than the remainder of the liver on immediate post-gadolinium images and remained relatively hyperintense on late phase images. Periabscess liver parenchyma was isointense on both T1- and T2-weighted images in 18 lesions, and in these lesions wedge-shaped subsegmental (n = 6) or segmental (n = 12) enhancement was observed on immediate gadolinium-enhanced images, which faded to isointensity on intermediate phase images. No perilesional signal changes and enhancement difference was observed in 15 lesions. Characteristic features of abscesses include: intense mural enhancement on early gadolinium-enhanced images, which persists with negligible change in thickness and intensity on later post-gadolinium images, and the presence of periabscess increased enhancement on immediate post-gadolinium images. These MRI features may help to distinguish abscesses from other focal liver lesions during differential diagnosis.     

MR imaging of the normal and abnormal clivus

We retrospectively reviewed 330 T1-weighted sagittal images, 80 T2-weighted sagittal images, and 83 gadopentetate-dimeglumine-enhanced scans of normal adults to determine the MR appearance of the normal adult clivus. MR images of 21 patients with an abnormal clivus (19 with tumor invasion and two with marrow reconversion) were also evaluated restrospectively and compared with those of the control group to assess MR features distinguishing the two groups. Our study revealed that a normal adult clivus consisted of low- and high-intensity portions mixed in various proportions on T1-weighted images. The low-intensity portion was isointense or hyperintense relative to the pons and always contained foci of bright signal intensity. The low-intensity tumor of a pathologic clivus tended to be hypointense relative to the pons (17/19), and was completely devoid of foci of bright signal intensity. The normal adult clivus was approximately isointense relative to the pons on T2-weighted images. Clival tumors were grossly hyperintense relative to the pons on T2-weighted images in 11 of 17 patients. In the remaining six patients, either a portion of or the entire lesion was isointense relative to the pons and, therefore, was not detectable on T2-weighted images. A normal adult clivus can enhance to some degree (19/83). Clival tumors were found to enhance intensely. A clivus of very low signal intensity (signal void) on T1- or T2-weighted images was always abnormal. The clivus with marrow reconversion was uniformly hypointense relative to the pons on T1-weighted images and isointense relative to normal marrow on T2-weighted images.(ABSTRACT TRUNCATED AT 250 WORDS)     

The dynamic magnetic resonance study of focal liver lesions by FLASH sequences with bolus intravenous gadolinium-DTPA]

Thirty-five patients with hepatic hemangioma (n = 12), metastasis (n = 10), hepatocellular carcinoma (HCC) (n = 10) and focal nodular hyperplasia (n = 3) were examined with the fast low-angle shot (FLASH) technique and an intravenous bolus injection of Gd-DTPA. In order to differentiate the lesions, the following criteria were used: a) pre Gd-DTPA intensity of lesions; b) post Gd-DTPA patterns of contrast enhancement. On the basis of these criteria, an unquestionable differential diagnosis could be made. Hemangiomas were characterized by an hypointense mass before Gd-DTPA, by peripheral contrast enhancement and by subsequent continuous hyperintense fill-in; thus, hemangiomas were visualized as hyperintense lesion during the late phase. Before contrast administration hypovascular metastases appeared as hypointense; they were characterized by delayed uptake of contrast agent. HCCs were hyperintense lesions before contrast administrations; then, quick contrast enhancement and rapid decrease in signal intensity were observed with visualization of a hyperintense ring due to the capsule. Finally, focal nodular hyperplasia appeared isointense or hypointense relative to normal liver on precontrast scans; the lesions were enhanced transiently with subsequent quick dismission of contrast agent. This initial experience suggests dynamic contrast-enhanced MR imaging as an effective method to improve the differential diagnosis among hepatic tumors when precontrast T2-weighted images are equivocal.     

Focal nodular hyperplasia of the liver: MR findings in 35 proved cases

MR images of 28 patients with 35 lesions of hepatic focal nodular hyperplasia were reviewed to determine the frequency of findings considered typical of this condition (isointensity on T1- and T2-weighted pulse sequences, a central hyperintense scar on T2-weighted images, and homogeneous signal intensity). Fifteen lesions were imaged at 0.6 T with T1- and T2-weighted spin-echo (SE) pulse sequences; 20 lesions were imaged at 1.5 T with T1-weighted SE and gradient-echo pulse sequences and T2-weighted SE pulse sequences. Diagnosis of focal nodular hyperplasia was made pathologically in 25 patients, with nuclear scintigraphy in four, and with follow-up imaging in six. Only seven lesions (20%) were isointense relative to normal liver on both T1- and T2-weighted images. On T1-weighted SE images, 21 lesions (60%) were isointense relative to normal liver, 12 (34%) were hypointense, and two (6%) were hyperintense. On T2-weighted SE images, 12 lesions (34%) were isointense and 23 (66%) were hyperintense relative to normal liver. A central scar was present in 17 lesions (49%) and was hypointense relative to the lesion on T1-weighted images and hyperintense on T2-weighted images. Twenty lesions (57%) were of homogeneous signal intensity throughout the lesion, except for the presence of a central scar. All three MR imaging characteristics were present in three cases (9%). We conclude that hepatic focal nodular hyperplasia has a wide range of signal intensity on MR imaging.     

Contrast-enhanced MRI of the liver with mangafodipir trisodium: imaging technique and results

Magnetic resonance (MR) contrast agents are now routinely used for detecting and characterizing focal liver lesions. Liver specific, hepatobiliary, MRI contrast agent mangafodipir trisodium (Mn-DPDP) is taken up by the functioning hepatocytes and excreted by the biliary system. Contrast uptake leads to persistent elevation of T1-weighted signal of normal liver parenchyma within 10 minutes of injection. Most tumors of non-hepatocellular origin typically are hypointense relative to enhanced liver parenchyma on T1 weighted images and are more conspicuous than on unenhanced images. Whereas, tumors of hepatocellular origin such as focal nodular hyperplasia (FNH), adenoma, and well-differentiated hepatocellular carcinomas (HCC) have been shown to accumulate Mn-DPDP, providing characterization information to discriminate hepatocellular from non-hepatocellular tumors. The purpose of this pictorial essay is to illustrate the appearance of various liver tumors on mangafodipir enhanced liver MR imaging.     

MR contrast of ferritin and hemosiderin in the brain: comparison among gradient-echo, conventional spin-echo and fast spin-echo sequences

OBJECTIVE: To compare the magnetic resonance image contrasts due to ferritin and hemosiderin in the brain tissue among different pulse sequences. MATERIALS AND METHODS: Fourteen patients with cavernous hemangioma in the brain prospectively underwent MR imaging with T2*-weighted gradient-echo (GRE), T2-weighted conventional spin-echo (SE) and fast spin-echo (FSE) sequences. The relative contrast ratios (CRs) of the hypointense part of cavernous hemangioma, globus pallidus and putamen to the deep frontal white matter were measured on each pulse sequence and statistically analyzed using analysis of variance followed by paired t-test. RESULTS: In the hypointense part of cavernous hemangioma, relative CRs were significantly lower on T2*-weighted GRE than on T2-weighted SE images (P=0.0001), and on T2-weighted SE than on T2-weighted FSE images (P=0.0001). In the globus pallidus, relative CRs were significantly lower on T2-weighted SE than on T2*-weighted GRE images (P=0.002), and on T2*-weighted GRE than on T2-weighted FSE images (P=0.0002). In the putamen, relative CRs were significantly lower on T2-weighted SE than on T2*-weighted GRE images (P=0.001), and there was no significant difference between CRs on T2-weighted FSE and T2*-weighted GRE images (P=0.90). CONCLUSION: Hemosiderin showed best image contrast on T2*-weighted GRE images but ferritin showed more prominent image contrast on T2-weighted SE than on T2*-weighted GRE images, which may help to determine an appropriate pulse sequence in neurological diseases associated with excessive ferritin accumulation.     

Gallbladder carcinoma: evaluation with MR imaging

Magnetic resonance (MR) images of 19 patients with histologically proved gallbladder carcinoma were retrospectively reviewed to determine the appearance of the primary tumor, and to assess the ability of MR imaging to demonstrate the various modes of tumor spread beyond the gallbladder. The primary tumor, as well as tumor spread beyond the gallbladder, was hyperintense on T2-weighted images and hypointense on T1-weighted images when compared with the liver parenchyma. Liver invasion and metastasis could be depicted by MR imaging with both sequences, unless the tumors were small or the extent of invasion was minimal. Duodenal invasion was difficult to evaluate because of motion artifacts, paucity of fat, and partial volume effects. T1-weighted images readily demonstrated extension of the tumor to the hepatoduodenal ligament and para-aortic region with good contrast between tumor and surrounding tissue. The extent of tumor extension to the blood vessels was also easily evaluated because of flow void in the vasculature. MR imaging can help determine the extent of gallbladder carcinoma and can contribute to the staging of this disease.     

Hypointense renal cell carcinoma: MR imaging with pathologic correlation

In two pathologically documented cases of renal cell carcinoma, the appearance of the tumors at magnetic resonance (MR) imaging was markedly hypointense relative to normal renal parenchyma on both T1- and T2-weighted spin-echo images. Pathologic examination of both tumors revealed diffuse iron scattered throughout the tumors. The paramagnetic effect of the iron may account for this unusual hypointense appearance at spin-echo imaging, independent of pulse sequence.     

MR appearance of rhinoscleroma.

BACKGROUND AND PURPOSE: We describe the MR imaging appearance of rhinoscleroma, an endemic, chronic, granulomatous disease whose causative agent is Klebsiella rhinoscleromatis. METHODS: The study included 15 patients (nine males and six females; mean age, 25 years; range, 13-36 years) with rhinoscleroma. MR imaging was performed in all patients. The signal intensity of the nasal masses was compared with that of fat, muscle, and CSF on both T1- and T2-weighted images. All cases were proved by histopathologic examination. RESULTS: The nasal masses were bilateral and symmetrical (n = 6), asymmetrical (n = 4), or unilateral (n = 5). They extended through the anterior nares (n = 9) or posterior choana into the nasopharynx (n = 3). They obstructed the ostiomeatal units with retained secretions in the related sinuses (n = 10). On T1-weighted images, rhinoscleroma showed striking (n = 9) or mild (n = 6) high signal intensity relative to muscle and CSF, but less hyperintensity than fat. On T2-weighted images, the nasal masses showed homogeneous high signal intensity (n = 10) or heterogeneous high signal intensity associated with hypointense foci (n = 5). They were hyperintense relative to fat and muscle, but less hyperintense than CSF. CONCLUSION: The hypertrophic stage of rhinoscleroma has characteristic mild to marked high signal intensity on both T1- and T2-weighted MR images.     

Chondroblastoma: MR characteristics with pathologic correlation.

PURPOSE: The purpose of this study was to describe the MR findings of chondroblastoma with pathologic correlation. METHOD: In 22 patients with pathologically proven chondroblastoma, MR signal characteristics were correlated with pathological findings. RESULTS: On T2-weighted images, 12 (55%) lesions were hyperintense with hypointense areas in 9 lesions, whereas 10 (45%) were hypointense. Therefore, 19 of 22 (86%) lesions with pathologic correlation had hypointense areas entirely (n = 10) or partly (n = 9) on T2-weighted images. On gadolinium-enhanced images, 13 (59%) lesions showed lobular enhancement and 9 (41%) showed marginal and septal enhancement. Low signal intensity on T2-weighted MR images was most strongly associated with an abundance of immature chondroid matrix, hypercellularity of the chondroblasts, calcifications, and hemosiderin on histology. CONCLUSION: Chondroblastoma was found to show hypointense portions on T2-weighted images. Signal intensity on T1- and T2-weighted MR images in chondroblastoma was dependent on the amounts of histopathological components.     

Coefficient D(av) is more sensitive than fractional anisotropy in monitoring progression of irreversible tissue damage in focal nonactive multiple sclerosis lesions

BACKGROUND AND PURPOSE: Persistently hypointense lesions on T1-weighted MR images have been shown to correlate with the amount of axonal damage and clinical disability in multiple sclerosis (MS) patients. The purpose of this study was to investigate whether diffusion coefficient D(av) and fractional anisotropy (FA) are able to detect quantifiable differences among three groups of focal nonactive multiple sclerosis (MS) lesions that appear qualitatively different on T1-weighted images. METHODS: Conventional and diffusion tensor MR images of the brain were obtained in 18 patients with relapsing remitting (n = 10) or secondary progressive (n=8) MS and in 18 healthy volunteers. Focal nonactive MS lesions were classified as T1 isointense, T1 mildly hypointense, and T1 severely hypointense on unenhanced T1-weighted images. Differences among groups were assessed with one-way analysis of variance using the T1 lesion appearance as the grouping factor and either FA or coefficient D(av) as the dependent measure. RESULTS: FA was lowest and coefficient D(av) was highest in T1 severely hypointense lesions, and then, in ascending and descending order, respectively, T1 mildly hypointense lesions and T1 isointense lesions. A significant difference in the values of FA was detected only between T1 isointense lesions and T1 severely hypointense lesions (P <.01), whereas no difference was found between T1 mildly hypointense lesions and either one of these two groups. A significant difference was found in the values of coefficient D(av) among all investigated lesion groups. Coefficient D(av) was found to correlate inversely with the T1-weighted contrast ratio (r=-0.58, P <.0001), whereas FA and deltaFA (percentage of FA variation in the lesion, a relative FA measure that minimizes the effect of FA spatial dependence) were not. CONCLUSION: Coefficient D(av) is more sensitive than FA to variations in the degree of T1 hypointensity and, thus, in the amount of the permanent brain tissue damage in patients with MS.     

MR imaging of the normal and abnormal clivus

We retrospectively reviewed 330 T1-weighted sagittal images, 80 T2-weighted sagittal images, and 83 gadopentetate-dimeglumine-enhanced scans of normal adults to determine the MR appearance of the normal adult clivus. MR images of 21 patients with an abnormal clivus (19 with tumor invasion and two with marrow reconversion) were also evaluated retrospectively and compared with those of the control group to assess MR features distinguishing the two groups. Our study revealed that a normal adult clivus consisted of low- and high-intensity portions mixed in various proportions on T1-weighted images. The low-intensity portion was isointense or hyperintense relative to the pons and always contained foci of bright signal intensity. The low-intensity tumor of a pathologic clivus tended to be hypointense relative to the pons (17/19), and was completely devoid of foci of bright signal intensity. The normal adult clivus was approximately isointense relative to the pons on T2-weighted images. Clival tumors were grossly hyperintense relative to the pons on T2-weighted images in 11 of 17 patients. In the remaining six patients, either a portion of or the entire lesion was isointense relative to the pons and, therefore, was not detectable on T2-weighted images. A normal adult clivus can enhance to some degree (19/83). Clival tumors were found to enhance intensely. A clivus of very low signal intensity (signal void) on T1- or T2-weighted images was always abnormal. The clivus with marrow reconversion was uniformly hypointense relative to the pons on T1-weighted images and isointense relative to normal marrow on T2-weighted images. The intensity patterns of the normal clivus on T1- and T2-weighted MR images change predictably with advancing age. Intensity patterns of abnormal clivi differ from those of normal clivi. When contrast material is used, normal and abnormal clivi generally show different patterns of enhancement.