MR imaging of diffuse liver disease

MR imaging is able to demonstrate and distinguish the full variety of benign and malignant diffuse liver diseases.     

Computed tomography. Focal and diffuse liver disease

Contrast enhanced CT is very accurate in the detection of focal hepatic disease. Lesion characterization is a more complex issue, in some instances requiring a combination of CT and other diagnostic tests or biopsy for accurate diagnosis. Although CT remains the modality of choice in the evaluation of suspected focal hepatic disease, this role may change if progress in MR imaging leads to further improvements in lesion detection and characterization.     

Focal liver lesions evaluated by MR imaging

Magnetic resonance signal intensity of focal liver lesions is the result of their histological and cytological features. Therefore, analysis of lesion signal intensity and enhancement patterns obtained with magnetic resonance imaging is essential for the differential diagnosis of focal liver lesions. In this article, we review the magnetic resonance imaging features of the most common focal liver lesions.     

MR imaging of diffuse glioma.

Neuroradiologic diagnosis of "gliomatosis cerebri" is hampered by the diffuse, isodense character of the lesion, and the fact that it may not enhance when intravenous contrast medium is administered. Clinical signs and symptoms are usually nonspecific, nonfocal, and disproportionately mild. We report a case of diffuse glioma in a 30-year-old man, discuss the difficulty in arriving at a precise diagnosis of gliomatosis cerebri, and examine the possible role of MR in its detection and delineation.     

Hepatocellular carcinoma of diffuse type: MR imaging findings and clinical manifestations

PURPOSE: To assess MR imaging findings and clinical manifestations of diffuse-type hepatocellular carcinoma (HCC). MATERIALS AND METHODS: We retrospectively reviewed our experience with diffuse HCC from November 1994 to October 2001. MR imaging findings and clinical features were assessed. RESULTS: Twenty-two consecutive patients with diffuse-type HCC (19 men and three women, age range 16-80 years [mean, 52 years]) were identified in a review of liver MR studies. This represented 13% of all patients with HCC imaged during this time period. Diffuse HCC showed a permeative, infiltrative pattern with ill-defined borders and no evidence of convex margination in all cases. At least 50% of the liver volume was involved with tumor. Diffuse-type HCC showed hypointensity in 15 patients, mixed intensity in three, and isointensity in four on T1-weighted images; heterogeneous hyperintensity in 16 patients; and homogeneous hyperintensity in six on T2-weighted MR images. Diffuse-type HCC showed patchy enhancement in 12 patients, miliary enhancement in nine, and minimal enhancement in one on postcontrast early-phase images, and showed heterogeneous wash-out in all patients on postcontrast late-phase images. Proximal portal venous tumor thrombosis was seen in all patients. Serum alpha-fetoprotein (AFP) value was elevated (>10 ng/mL) in 14 of 18 patients, and 13 showed a value greater than 500 ng/mL. The four patients who did not have elevated AFP had tumors which were indistinguishable from those in patients with elevated AFP; they also did not have a distinctive clinical history. CONCLUSION: Diffuse-type HCC was typically seen as an extensive, heterogeneous permeative hepatic tumor, with portal venous tumor thrombosis on MR images in all cases. Early enhancement, observed as patchy in 12 and miliary in nine of 22 patients, was a distinctive imaging feature. Elevated serum AFP value was a common finding; however, 22% had normal values.     

Focal and diffuse liver disease studied by quantitative microstructural sonography

Quantitative microstructural sonography differs from conventional sonography in several ways. The frequency as well as the amplitude of echoes is recorded and assessed using spectral analysis techniques. The effects of diffraction of the ultrasound beam are calibrated, as are the transfer characteristics of the system. Studies of patients with alcoholic liver disease revealed significantly increased attenuation, heterogeneity of scatterers, and local scattering strength in those with severe disease; in contrast, patients with mild cirrhosis exhibited decreased local scattering strength compared to normal individuals. Using retrospective three-parameter discriminant analysis, 23 out of 24 patients were successfully categorized, suggesting that the parameters used were capable of measuring microstructural changes associated with these disease states. Parameters varied widely among 6 types of hepatic tumors, suggesting that this method may offer promise in distinguishing tumors from normal cases and alcoholic liver disease as well as from each other. Further applications and evaluation of this method appear justified.     

Diffusion-weighted single-shot echoplanar MR imaging for liver disease.

OBJECTIVE: The aims of this study were to determine apparent diffusion coefficients (ADCs) of the abdominal organs and liver lesions, to determine the effect of the magnitude of b values on the ADCs, and to determine whether measured ADCs of liver tumors help differentiate benign from malignant lesions. SUBJECTS AND METHODS: Six healthy volunteers and 126 patients were examined with diffusion-weighted single-shot echo-planar imaging using multiple b values (maximum, 846 sec/mm2). The ADCs of the liver, spleen, kidney, 49 malignant liver lesions (33 hepatocellular carcinomas, 15 metastatic liver tumors, and one cholangiocellular carcinoma), and 30 benign lesions (17 cysts, 12 hemangiomas, and one angiomyolipoma) were calculated. RESULTS: The ADCs of the abdominal organs and liver lesions showed smaller values when calculated with the greater maximum b values. The ADCs of the benign lesions calculated with all the b values of less than 850 sec/mm2 (2.49+/-1.39 x 10(-3) mm2/sec) were significantly (p = .0024) greater than those of the malignant lesions (1.01+/-0.38 x 10(-3) mm2/sec). When the maximum b value is 846 sec/mm2, use of a threshold ADC of 1.6 x 10(-3) mm2/sec would result in a sensitivity of 98% and a specificity of 80% for differentiation of malignant liver lesions from benign lesions. CONCLUSION. Measurement of ADC has good potential for characterizing liver lesions, but the calculated ADCs could be affected by the magnitude of the maximum b value.     

Focal liver lesions: MR imaging with Mn-DPDP--initial clinical results in 40 patients.

Manganese (II) N,N'-dipyridoxylethylenediamine-N,N'-diacetate-5,5'-bis(phosphate) (DPDP) was evaluated as a contrast agent for magnetic resonance (MR) imaging (1.5 T) of focal liver lesions in 40 patients. Doses of 5 and 10 mumol/kg were administered intravenously. Mn-DPDP-enhanced T1-weighted images were compared quantitatively and subjectively with standard T1- and T2-weighted nonenhanced images. Use of Mn-DPDP resulted in a statistically significant increase in signal intensity of liver parenchyma in T1-weighted images at both doses. No enhancement was seen in metastases, cholangiocarcinomas, or lymphomas, while all hepatocellular carcinomas were enhanced. Enhancement was seen in focal nodular hyperplasia and in regenerative nodules. The lesion-to-liver contrast in Mn-DPDP-enhanced gradient-recalled-echo images was superior to that of all precontrast images (P less than .01). The number of nonenhancing malignant liver lesions detected in spin-echo (SE) images was increased (272 in T2-weighted SE images vs 390 in T1-weighted Mn-DPDP-enhanced SE images). Image interpretation (eg, visualization and demarcation of the lesions) was markedly better in Mn-DPDP-enhanced images than in all precontrast images (P less than .001).     

脊索瘤的MRI表现

目的：探讨脊索瘤的MRI表现及其诊断价值。方法：回顾性分析17例经临床病理证实的脊索瘤的MRI表现。结果：颅底脊索瘤8例，骶尾部脊索瘤9例，邻近颅底及椎体骨质均有溶骨性破坏，伴硬膜外及骶前较大软组织肿块。17例中16例信号不均匀，T1WI呈低、等信号，T2WI呈明显高信号，MRI增强扫描后，肿瘤均有轻度或中度不均匀性强化。结论：T2WI显著高信号是脊索瘤的特征性MRI表现，有重要鉴别诊断意义，MRI反映肿瘤的部位、侵犯范围以及显示骨质破坏作用均优于CT。     

Focal hepatic lesions: differentiation with MR imaging at 0.5 T

Magnetic resonance (MR) examinations of 43 patients with 95 focal hepatic lesions (diameter, greater than 1 cm) were analyzed for lesion shape, homogeneity, and relative signal intensity compared with normal liver parenchyma, spleen, and skeletal muscle. On T1-weighted, balanced, and T2-weighted images, most metastases (74%), cavernous hemangiomas (76%), and cysts (82%) were smooth and round or oval, while the hepatocellular carcinomas all had irregular borders (40%) or were lobulated (60%). All lesions with irregular borders were malignant. Seventy percent of metastatic lesions, 85% of cavernous hemangiomas, and 100% of simple hepatic cysts were of homogeneous signal intensity, while 60% of hepatocellular carcinomas were inhomogeneous. Logistic regression analysis of multiple lesion characteristics showed that inhomogeneous lesions had a high likelihood of malignancy, while markedly hyperintense lesions had a very low probability of being malignant, regardless of other traits. Homogeneous lesions that were isointense or hyperintense compared with spleen on balanced images but were not markedly hyperintense on T2-weighted images also had a high likelihood of malignancy.     

MR imaging manifestations of skin tumors

In this study, we evaluated MR imaging findings of skin tumors and categorized them into four types: (1) discrete mass lesions of the dermis and epidermis, (2) mass lesions of the subcutis with or without abutment to the skin, (3) diffuse or localized skin thickening without a true mass, and (4) a skin mass with bone destruction. The categorization of MR images may be useful in the differential diagnosis of skin tumors.     

Focal liver disease: comparison of dynamic contrast-enhanced CT and T2-weighted fat-suppressed, FLASH, and dynamic gadolinium-enhanced MR imaging at 1.5 T.

Dynamic contrast medium-enhanced computed tomography (CT), T2-weighted fat-suppressed spin-echo (T2FS) magnetic resonance (MR) imaging, and breath-hold T1-weighted fast low-angle shot (FLASH) MR imaging before and after dynamic gadopentetate dimeglumine injection were compared in 73 patients with clinically suspected liver disease. Observer confidence for presence of focal lesions was determined by using receiver operating characteristic analysis. For all MR images, hepatic lesion-liver signal-to-noise ratios were evaluated qualitatively. and resolution and presence of artifacts were evaluated qualitatively. Lesion detection was greatest with T2FS (n = 272) and enhanced FLASH (n = 244) and was statistically greater with both of these than with CT (n = 220) and FLASH (n = 219) (P less than .03). Correct lesion characterization was greatest with enhanced FLASH (n = 236) (P less than .01), followed by CT (n = 199), FLASH (n = 164), and T2FS (n = 144). Enhanced FLASH was particularly successful in characterization of 5-mm- to 1.5-cm-diameter lesions as cystic or solid.     

皮肤肿瘤的MRI表现

本研究旨在对皮肤肿瘤的影像学表现进行评价，并根据肿瘤的影像学特点将其分为4种类型：①表皮与真皮散在的肿块。②与皮肤相连或不相连的皮下组织肿块。③弥漫或局限性的皮肤增厚，没有形成真正的肿块。④皮肤肿块伴有骨骼破坏。MRI影像的分类有助于皮肤肿瘤的鉴别诊断。     

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.     

Focal nodular hyperplasia of the liver: assessment with contrast-enhanced TurboFLASH MR imaging

Twenty-two patients with 25 cases of focal nodular hyperplasia (FNH) proved with pathologic study were imaged with a TurboFLASH (fast low angle shot) sequence combined with bolus administration of gadolinium tetraazacyclododecanetetraacetic acid (DOTA), spin-echo (SE) T2-weighted sequences, and postcontrast T1-weighted sequences. FNH-liver signal-difference-to-noise ratios were quantified; the features of the central scar were qualitatively analyzed. On SE T2-weighted images, all FNHs were hyperintense; in two cases the central scar exhibited a high signal intensity associated with hypointense areas corresponding to fibrous tissue within the branches of the scar. Unenhanced TurboFLASH images always demonstrated the FNHs as hypointense and always depicted the central scar as a hypointense area within the lesion. After bolus injection, arterial enhancement of FNH was clearly seen, and in 10 of 25 lesions, enhancement within the scar was seen 40-80 seconds after injection. Both unenhanced and enhanced TurboFLASH sequences produced the best signal-difference-to-noise ratios in comparison with T2-weighted images.