MR imaging of intrahepatic cholangiocarcinoma

Background: The purpose of this study was to determine the magnetic resonance (MR) features of intrahepatic cholangiocarcinoma. Methods: MR imaging studies of seven cases of pathologically proven intrahepatic cholangiocarcinoma were retrospectively reviewed. Results: On MR images the tumors presented as a single mass (N = 5) or multiple nodules (N = 2), as welldelineated (N = 5) or ill-defined (N = 2), and as non-encapsulated (N = 7). Mean tumor diameter ranged from 6–14 cm (mean, 10 cm). On T1-weighted (TR/TE = 400–600/10–17 msec) images, the tumors were hypointense compared to the liver. The five tumors studied with dynamic MR imaging showed progressive centripetal filling-in after intravenous administration of a gadolinium chelate. On T2-weighted (TR/TE = 2000–2500/80–100 msec) images, all tumors were hyperintense compared to the liver; five were markedly hyperintense and two moderately hyperintense. Vascular encasement, bile duct dilatation within the tumor, and central scar were depicted on MR images in four, three, and two tumors respectively. Conclusion: The typical MR appearance of intrahepatic cholangiocarcinoma is a large well-delineated nonencapsulated tumor associated with intrahepatic venous encasement.     

Intrahepatic bile duct dilatation secondary to hepatocellular carcinoma: CT features in 10 patients

Background: To determine the computed tomographic (CT) features of bile duct obstruction secondary to hepatocellular carcinoma (HCC). Methods: CT examinations of 10 patients (mean age, 58 years) with bile duct obstruction secondary to HCC were retrospectively reviewed. Results: All tumors were intrahepatic. Eight tumors were well-delineated and two were ill-defined. The largest diameters of tumor ranged from 1.5–6.0 cm (mean, 3.6 cm). All tumors were hypodense before contrast and did not contain calcification. After contrast, four tumors became hypodense, three were isodense, and three were hyperdense to the liver. No tumor demonstrated encapsulation. Diffuse intrahepatic bile duct dilatation was observed in seven patients. One patient had extrahepatic bile duct dilatation. Localized bile duct dilatation was observed in three patients, in the hemi-liver which contained the tumor. No tumor invaded the portal vein. Conclusion: Although rare, HCC should be included in the differential diagnosis of bile duct obstruction. This diagnosis should be suggested in patients with bile duct obstruction when CT shows an associated intra- or extrahepatic mass. Our results suggest that HCC responsible for bile duct obstruction is remarkable for the absence of encapsulation.     

MR imaging of hepatocellular carcinomas with biliary tumor thrombi

We retrospectively evaluate the MR imaging findings of hepatocellular carcinomas (HCC) with biliary tumor thrombi. MR imaging was performed on six patients presenting with obstructive jaundice and/or biliary hemorrhage. T1-weighted images, T2-weighted images, MR cholangiopancreatography (MRCP), and dynamic MR images were obtained. Duodenal endoscopy was performed on all cases and hepatic resection on two cases. HCCs were 1.8–10 cm in diameter (mean 5.8 cm). Biliary tumor thrombi were detected in all patients on MR imaging. Tumor thrombi showed hypointensity on T1-weighted images, hyperintensity on T2-weighted images, and contrast enhancement on the early phase of dynamic MR images. MRCP showed intrahepatic bile duct dilatation in all cases. Biliary hemorrhage was clearly depicted by MR images in five cases and showed hyperintensity on T1-weighted images and hyperintensity or hypointensity on T2-weighted images. Biliary hemorrhage was confirmed by endoscopy in two cases. Portal vein thrombi were also associated in five of six patients. Pathologically, tumor thrombi of HCCs were demonstrated in two patients who underwent hepatic resection. In conclusion, MR imaging is useful for the diagnosis of biliary tumor thrombi from HCC and for evaluating the extension of thrombi and biliary hemorrhage.     

Fascioliasis: US, CT, and MRI findings with new observations

Background: The purpose of this study is to describe the ultrasonographic (US), computed tomographic (CT), and magnetic resonance imaging (MRI) findings in fascioliasis and to emphasize the impact of radiology in diagnosis. Methods: Radiologic findings in 23 consecutive patients with fascioliasis were prospectively recorded. All patients had at least one US and CT examination, and 10 of them were studied by MRI. All diagnoses were confirmed by serologic methods. In the first three cases, initial diagnosis was reached by microscopic demonstration of the parasites' eggs in bile obtained by US-guided gallbladder aspiration. Results: In the hepatic phase of fascioliasis, multiple, confluent, linear, tractlike, hypodense, nonenhancing hepatic lesions were detected by CT. On US, the parasites could be clearly identified in the gallbladder or common bile duct as floating and nonshadowing echogenic particles. MRI showed the lesions as hypo- or isointense on T1-weighted images and as hyperintense on T2-weighted images. Conclusions: CT findings in the hepatic phase and US findings in the biliary phase are characteristic of fascioliasis. Because clinical and laboratory findings of fascioliasis may easily be confused with several diseases, radiologists should be familiar with the specific radiologic findings of the disease to shorten the usual long-lasting diagnostic process. Received: 15 December 1999/Accepted: 26 January 2000     

Sclerosing hepatocellular carcinoma: Radiologic findings

The radiologic findings of seven patients with sclerosing hepatocellular carcinoma (HCC), an unusual subtype of HCC, were evaluated. Computed tomography (CT) demonstrated a hypointense mass with marked delayed contrast enhancement. Although the tumor was well-defined, the tumor capsule was not seen. Focal atrophy was seen in four patients. Ultrasound (US) showed an isoechoic to hyperechoic mass without a rim. Angiography revealed prominent tumor vessels and prolonged stains in all cases. Arterial encasement was seen in four patients. On magnetic resonance (MR) imaging, all tumors were hypointense on T1-weighted images and hyperintense on T2-weighted images. On dynamic MR study, remarkable contrast enhancement, which continued to the delayed phase, seemed to be characteristic for sclerosing HCC. In the presence of liver tumors with homogeneous architecture, hypervascularity, prolonged enhancement, absence of tumor capsule, and focal atrophy in high-risk patients of HCC, sclerosing HCC should be considered.     

Plain and gadolinium-DTPA-enhanced MR imaging of hepatocellular carcinoma treated with transarterial chemoembolization

Background: To assess unenhanced and gadolinium-enhanced magnetic resonance (MR) imaging patterns of hepatocellular carcinoma (HCC) treated with transarterial chemoembolization (TACE). Methods: Thirty-two patients with 48 HCC lesions underwent MR imaging before and 15 days after TACE. Fifteen lesions were then surgically resected. The remaining 33 lesions were not removed and were followed up with MR imaging at 3, 6, 12, and 18 months after treatment. Spin echo (SE) T1- and T2-weighted and gadolinium-enhanced SE T1-weighted sequences were employed. Qualitative evaluation of signal intensity pattern of the treated lesions was performed in all cases. Histological evaluation and selective hepatic arteriography were considered the gold standard of the study for the 15 resected lesions and the 33 unresected lesions, respectively. Results: On follow-up enhanced T1-weighted images of the 15 resected lesions, seven showed no area of enhancement corresponding to complete necrosis at histologic examination. The remaining eight resected lesions showed areas of enhancement; in six of these cases, viable tumor tissue was found at histology; in the other two lesions, histologic examination revealed the presence of complete tumor necrosis. In the group of resected lesions, T2-weighted images showed no pattern characteristic of necrosis. In 24 of 33 unresected lesions, loss of enhancement on follow-up enhanced T1-weighted images was a characteristic finding, which correlated to devascularization at arteriography. Of these 24 lesions, 17 were completely hypointense on follow-up T2-weighted images; the remaining seven showed small foci of hyperintensity. The other nine unresected lesions showed enhanced portions on follow-up enhanced T1-weighted images, which corresponded to hyperintense areas on T2-weighted images. These findings correlated to persistence of hypervascular areas at arteriography. Conclusion: Gadolinium-enhanced T1-weighted MR imaging is a reliable method for evaluating the outcome of TACE treatment and is more accurate than unenhanced T2-weighted MR imaging. Received: 2 June 1995/Accepted: 18 July 1995     

Bile duct disease: Prospective comparison of ERCP,CT, and fat suppression MRI

The authors compared computed tomography (CT) and endoscopic retrograde cholangiopancreatography (ERCP), techniques commonly used to study the biliary tree, with pre- and post-Gd-DTPA breath-hold fast low angle shot (FLASH) and fat suppressed spin-echo in 28 consecutive patients with bile duct abnormalities detected on ERCP, including 11 patients with malignant disease and 17 patients with benign disease. ERCP, CT, and magnetic resonance (MR) images were prospectively interpreted in a blinded fashion and reviewed by consensus. ERCP characterized all cases of malignant disease by the presence of a narrowed bile duct lumen with irregular margins. CT and MRI detected all cases of malignant disease and characterized nine of 11 as malignant. In seven of these cases, CT and MRI showed thickening of extrahepatic bile duct walls >5 mm. MRI images showed intrahepatic-enhancing periportal tissue in four cases, which was not seen on CT images, and which was biopsyproven tumor extension. Benign disease was characterized on ERCP images by the demonstration of smooth tapered narrowings in 16 cases, whereas on CT and MR images it was characterized by mild to moderate dilatation of the intrahepatic bile ducts and wall thickness < 5 mm in 13 cases. Overall ERCP correctly characterized 27 cases as benign or malignant and CT and MRI both characterized 25. The results of this study show a trend that ERCP is superior to CT and MRI for characterizing bile duct disease.     

Segmental high intensity on T1-weighted hepatic MR images

Background We investigated the diagnostic importance of segmental high-intensity (SHI) areas not corresponding to mass lesions on T1-weighted magnetic resonance (MR) images. Methods We conducted a retrospective investigation of hepatic MR images obtained from 634 patients during a 4-year period at our institution. Images were compared with findings reported in the patients’ medical records. There were 16 patients (2.5%) with SHI areas not corresponding to a mass lesion. We compared MR images with plain computed tomographic (CT) scans (n = 16), angiograms (n = 12), and histologic findings (n = 10). Results The segments with intrahepatic bile duct dilatation showed hyperintensity on T1-weighted images. In six of 16 patients, the biliary duct was more dilated in the area of hyperintensity than in areas without hyperintensity. The SHI areas appeared as areas of low attenuation (n = 13), high attenuation (n = 1), or isoattenuation (n = 2) on plain CT scans. Histologically, these areas showed ductular proliferation and deposition of bile pigment within the hepatocytes. Conclusion Segmental areas of increased signal intensity on T1-weighted images were probably due to intrahepatic cholestasis.     

肝内胆管乳头状瘤的CT及MR表现

目的：探讨肝内胆管乳头状瘤（Intrahepatic biliary papillomatosis,IHBP）的临床病理特征、影像学表现。方法 ：回顾性分析5例经手术病理证实的IHBP患者的临床病理特征及影像学表现,并结合文献进行分析和讨论。结果：5例IHBP患者中2例表现为间歇性黄疸、1例腹痛伴发热、1例左腰背部酸痛,1例体检时发现。影像学特点：5例均发现全胆管树系统扩张,胆总管下段无明确占位或结石,受累肝内胆管相对比另一肝叶胆管或胆总管不成比例的扩张,受累肝内胆管呈＂瘤样＂扩张,扩张的肝内胆管出现乳头状或长条状肿块影,MRCP示扩张胆管内多发乳头状及条状充盈缺损,3例位于右肝内胆管、2例位于左肝内胆管,肿块直径约0.3~2.5 cm,于CT平扫呈等或稍低密度,MR T1WI表现为等或稍低信号,T2WI上多呈等高信号,DWI上呈乳头状及条状高信号,增强扫描肿块呈轻度强化。结论：IHBP的影像学表现有一定的特征性,尤其MRCP、DWI及动态增强检查,熟悉该病的特征性影像学表现有助于对IHBP诊断及鉴别诊断。     

Preoperative evaluation of Klatskin tumor: accuracy of spiral CT in determining vascular invasion as a sign of unresectability

Background: To assess the accuracy of spiral computed tomography (CT) in predicting the resectability of Klatskin tumor as determined by vascular invasion. Methods: Twenty-one consecutive patients with Klatskin tumor who had undergone laparotomy were included in this study. The preoperative thin-section (5-mm-thick) spiral CT scans of these patients were assessed for the surgical resectability of tumor by evaluating the vascular invasion. The criterion for vascular invasion indicating unresectability was the tumoral invasion of the proper hepatic artery or main portal vein or simultaneous invasion of one side of the hepatic artery and the other side of the portal vein. Results: All nine patients with tumors thought to be unresectable on the basis of CT findings had tumors that were unresectable at surgery (positive predictive value, 100%). Of 12 patients with tumors thought to be resectable, six had resectable tumors (negative predictive value, 50%). Spiral CT failed to detect small hepatic metastasis (n= 1), lymph node metastasis (n= 1), extensive tumor (n= 2) and variation of bile duct (n= 2), which precluded surgical resection. Conclusion: Spiral CT is a reliable method for detecting vascular invasion and unresectable tumors. However, it has limitations in detecting variations of the bile duct or the intraductal extent of tumor. Received: 24 November 1999/Accepted: 26 January 2000     

MR cholangiopancreatography: comparison between half-Fourier acquisition single-shot turbo spin-echo and two-dimensional turbo spin-echo pulse sequences

Background: To compare half-Fourier acquisition single-shot turbo spin-echo (HASTE) magnetic resonance cholangiopancreatography (MRCP) with two-dimensional turbo spin-echo (2D TSE) MRCP for imaging pancreatobiliary diseases. Methods: Twenty-seven patients with biliary or pancreatic disease underwent MRCP on a 1.0-T scanner with a body phased-array coil. A T2-weighted HASTE sequence (18 s) and a T2-weighted 2D TSE sequence (45 s) were used during a breath-hold by the patient. The source images and maximum intensity projection images of both sequences were reviewed independently by two radiologists. Results: Motion artifacts were more severely pronounced with 2D TSE sequences than with HASTE sequences (p < 0.001). All obstructions and their sites were accurately identified with both sequences. Filling defects (calculi) in bile ducts were identified in all 22 segments (100%) with HASTE-MRCP, whereas calculi in 19 of 22 segments (86%) were identified with 2D TSE-MRCP (p= 0.25). Three missed sites on 2D TSE-MRCP were intrahepatic bile ducts. Conclusions: HASTE-MRCP is superior to 2D TSE-MRCP in terms of detecting motion artifacts and visualization of the pancreatic ducts. HASTE-MRCP is comparable to 2D TSE-MRCP for visualization of the biliary ducts and their obstruction and is superior to 2D TSE-MRCP for identification of calculi in intrahepatic bile ducts. Received: 16 April 1997/Accepted: 28 May 1997     

MR findings of hepatic cavernous hemangioma after intraarterial infusion of iodized oil

Magnetic resonance (MR) imaging was performed on five tumors of three patients who had hepatic hemangiomas. Four tumors were given an intraarterial infusion of 3–8 ml of iodized oil, while one tumor was not. MR images were obtained at 2.0 or 0.5 T. A single spin echo sequence with TE of 30 ms and TR of 500 ms and a double echo sequence with TEs of 60 and 150 ms and TR of 2000 ms, were used to produce relatively T1-, T2-weighted, and heavily T2-weighted images, respectively. Follow-up MR imaging was done 1–5 months after infusion of iodized oil. On relatively T1 weighted images, hemangiomas showed iso or hypointensity. On T2-weighted images, all tumors showed hyperintensity. However, on heavily T2-weighted images, tumors with iodized oil showed heterogeneous, slight hyperintensity, while tumors without iodized oil showed characteristic appearance of marked hyperintensity in hemangiomas. In hepatic cavernous hemangiomas with intraarterial infusion of iodized oil, familiarity with this unusual MR intensity of tumors on heavily T2-weighted images is useful to avoid the incorrect diagnosis and to reduce the frequency of inappropriate hepatic resection.     

Nodular regenerative hyperplasia of the liver in Budd–Chiari syndrome: CT and MR features

We report the imaging findings of spiral computed tomography (CT), magnetic resonance (MR) imaging, and MR angiography in a patient with nodular regenerative hyperplasia of the liver associated with Budd–Chiari syndrome. Spiral CT showed multiple enhancing nodules during the hepatic arterial and portal venous phases. MR images showed multiple hyperintense nodules on T1-weighted images and hypointense or isointense nodules on T2-weighted images. MR angiography showed thrombotic occlusion of three hepatic veins, suggesting Budd–Chiari syndrome. Received: 25 June 1999/Revision accepted: 22 September 1999     

Segmental high intensity on T1-weighted hepatic MR images

BACKGROUND: We investigated the diagnostic importance of segmental high-intensity (SHI) areas not corresponding to mass lesions on T1-weighted magnetic resonance (MR) images. METHODS: We conducted a retrospective investigation of hepatic MR images obtained from 634 patients during a 4-year period at our institution. Images were compared with findings reported in the patients' medical records. There were 16 patients (2.5%) with SHI areas not corresponding to a mass lesion. We compared MR images with plain computed tomographic (CT) scans (n = 16), angiograms (n = 12), and histologic findings (n = 10). RESULTS: The segments with intrahepatic bile duct dilatation showed hyperintensity on T1-weighted images. In six of 16 patients, the biliary duct was more dilated in the area of hyperintensity than in areas without hyperintensity. The SHI areas appeared as areas of low attenuation (n = 13), high attenuation (n = 1), or isoattenuation (n = 2) on plain CT scans. Histologically, these areas showed ductular proliferation and deposition of bile pigment within the hepatocytes. CONCLUSION: Segmental areas of increased signal intensity on T1-weighted images were probably due to intrahepatic cholestasis.     

Small hepatocellular carcinoma: differentiation from adenomatous hyperplasia with color Doppler US and dynamic Gd-DTPA-enhanced MR imaging

Background: To investigate the usefulness of color Doppler ultrasound (US) and dynamic Gd-DTPA-enhanced magnetic resonance (MR) imaging in the differentiation of small hepatocellular carcinoma (HCC) and adenomatous hyperplasia (AH). Methods: Thirty-eight small (3 cm or less) nodular lesions (in 38 cirrhotic patients) with US features consistent with HCC underwent evaluation with color Doppler US and MR imaging. Breath-hold T1-weighted rapid acquisition spin echo MR sequence after bolus injection of 0.1 mmol/kg gadopentetate dimeglumine was used to evaluate dynamic enhancement. US-guided tissue-core percutaneous biopsy established the diagnosis: HCC in 28 cases and AH in 10. Results: Color signals with pulsatile or continuous Doppler spectrum were demonstrated in 19 of 28 HCCs (68%) but in none of the AHs. Although there was considerable overlap in signal intensity between HCC and AH on both unenhanced T1- and T2-weighted images, early enhancement on breath-hold T1-weighted images obtained 40 s after starting contrast administration was observed in 22 of 28 HCCs (79%) but in none of the AHs. In 26 of 28 HCCs (93%), pulsatile or continuous flow at color Doppler US, early enhancement at dynamic MR imaging, or both were observed. Conclusion: Findings with color Doppler US and dynamic Gd-DTPA-enhanced MR imaging enable a reliable distinction between small HCC and AH. Received: 8 August 1994/Accepted after revision: 27 January 1995     

MR imaging of malignant mesenchymal tumors of the liver

Magnetic resonance (MR) features of five primary malignant mesenchymal neoplasms (plasmocytoma, leiomyosarcoma, undifferentiated sarcoma, epithelioid hemangioendothelioma, and angiosarcoma) of the liver were reported. All tumors were hypointense on T1-weighted images and hyperintense on T2-weighted images. No halo and intravenous extension were noted. A target appearance was revealed in epithelioid hemangioendothelioma. MR findings of angiosarcoma were essentially the same as those of cavernous hemangiomas (markedly hyperintense with hypointense linear septa on T2-weighted images). MR findings of these rare hepatic malignancies were nonspecific, although they were quite different from those of typical hepatocellular carcinomas. This study suggested that MR differentiation of primary hepatic mesenchymal tumors from other common benign and malignant neoplasms was difficult; however, the number of studied cases was limited.     

Dynamic contrast-enhanced MR imaging of fibrolamellar hepatocellular carcinoma

The magnetic resonance (MR) appearance of fibrolamellar hepatocellular carcinoma (FL-HCC) on T1- and T2-weighted and dynamic serial postgadolinium-DTPA images is reported. Both tumors were large (>7 cm in shortest dimension) and had central regions of low signal intensity on T1- and T2-weighted images. Diffuse heterogeneous enhancement of the tumors occurred on immediate postcontrast images. Lesions became more homogeneous in enhancement over time, but lack of enhancement of central portions of the tumor persisted. Although persistent lack of enhancement of the tumor scar on late postcontrast MR images may be characteristic of FL-HCC compared with delayed enhancement in focal nodular hyperplasia, the potential similarities between these tumors is stressed.     

T2-weighted MR imaging for hepatic hemangiomas: comparison of breath-hold and non-breath-hold turbo spin-echo pulse sequences with phased-array multicoil

Background: We compared T2-weighted and heavily T2-weighted breath-hold turbo spin-echo (TSE) sequences with T2-weighted non-breath-hold TSE sequence to evaluate hepatic hemangiomas on magnetic resonance (MR) with a phased-array multicoil. Methods: Twenty-two patients with 27 hemangiomas were studied at 1.0-T scanner by using T2-weighted and heavily T2-weighted breath-hold TSE sequences (18 s each) and non-breath-hold T2-weighted TSE sequences with use of a phased-array multicoil. Images were quantitatively analyzed for tumor-to-liver signal-difference-to-noise ratios (SD/Ns) and tumor-to-liver signal intensity ratios (T/Ls) and qualitatively analyzed for tumor conspicuity and motion-induced image artifacts. Results: Quantitatively, T2-weighted breath-hold TSE images showed the highest SD/Ns among the three sequences, although the differences from the heavily T2-weighted breath-hold TSE sequence and the T2-weighted non-breath-hold TSE sequence were not statistically significant (p= 0.61 and 0.06, respectively). Heavily T2-weighted breath-hold TSE images showed the highest T/Ls among the three sequences. The differences from the T2-weighted breath-hold TSE sequence and the T2-weighted non-breath-hold TSE sequence were statistically significant (p < 0.001). Qualitatively, breath-hold TSE images were superior to non-breath-hold TSE images in terms of tumor conspicuity (p < 0.01) and motion artifacts (p < 0.01). Conclusion: T2-weighted breath-hold TSE sequence is superior to T2-weighted non-breath-hold TSE sequence in the evaluation of hepatic hemangiomas on MR with a phased-array multicoil. Received: 7 April 1997/Accepted: 28 May 1997     

Bile duct leaks after laparoscopic cholecystectomy: value of contrast-enhanced MRCP

Background We assessed the role of mangafodipir-enhanced magnetic resonance (MR) cholangiography in the detection and location of bile duct leaks after laparoscopic cholecystectomy.Methods In a prospective study, 34 patients with clinical suspicion of bile duct leak after laparoscopic cholecystectomy underwent MR imaging. Our protocol included conventional heavily T2-weighted MR cholangiography and three-dimensional T1-weighted MR cholangiography after an intravenous bolus injection of mangafodipir trisodium. All studies were performed on a 1.5-T or 1-T scanner. Contrast-enhanced MR cholangiograms were evaluated for the presence and location of bile duct leaks. Correlation was obtained in all cases with surgery (n = 15), endoscopic retrograde cholangiography (n = 5), percutaneous drainage (n = 5), and clinical follow-up (n = 9).Results In 20 of 34 patients, bile duct leakage was proved by surgery, endoscopic retrograde cholangiography, or drainage. Contrast enhancement displayed the leakage in 19 of 20 patients and ruled out leaks in the other 14 patients (95% sensitivity, 100% specificity). The leak site was depicted in 14 patients and contrast-enhanced MR cholangiography successfully located the origin of the leak in 11 patients.Conclusions Contrast-enhanced MR cholangiography with intravenous mangafodipir trisodium can accurately diagnose the presence and location of bile duct leaks in patients who have undergone laparoscopic cholecystectomy.     

Well-differentiated hepatocellular carcinoma: findings of US, CT, and MR imaging

Background: To elucidate the imaging characteristics of well-differentiated hepatocellular carcinomas (HCCs) on ultrasonography (US), computed tomography (CT), and magnetic resonance (MR) imaging. Methods: Ultrasonograms, CTs, and MR images of 18 histopathologically proven well-differentiated HCCs in 15 patients were reviewed. The findings of these images were correlated with histopathologic findings. Results: On US, seven tumors were depicted as a hyperechoic area and eight as a hypoechoic area. Three tumors were not visualized. On precontrast CT, four tumors were depicted as a low-density area, but 14 were not visualized. On conventional contrast-enhanced CT, 12 tumors were depicted as a low-density area but six were not visualized. On T1-weighted MR images, 10 tumors had high signal intensity and two had low signal intensity. Six tumors were not visualized. On T2-weighted MR images, five tumors had high signal intensity and two had low signal intensity. Eleven tumors were not visualized. Tumors with fatty change and/or clear cell formation were frequently hyperechoic on US and hyperintense on T1-weighted MR images. Conclusions: Well-differentiated HCCs show different findings on US, CT, and MR imaging. Therefore, reliable diagnosis of well-differentiated HCCs by these imaging techniques may be difficult. Received: 29 April 1998/Revision accepted: 15 July 1998