Malignant lesions of the liver with high signal intensity on T1-Weighted MR images

Our purpose was to identify the histologic types of malignant liver lesions with high signal intensity (SI) on T1-weighted images and to describe the MR imaging features. Thirteen patients with malignant liver lesions high in SI on T1-weighted images were studied with a 1.5-T MR imager using pre- and serial postcontrast spoiled gradient-echo (SGE) sequences (all patients), T2-weighted fat-suppressed spin-echo sequences (all patients), precontrast T1-weighted fat-suppressed spin-echo sequences (five studies in five patients), and precontrast out-of-phase SGE sequences (seven studies in six patients). Images were reviewed retrospectively to determine number of lesions; lesion size; SI of lesions on T1-weighted, T2-weighted, and fat-attenuated T1-weighted images; distribution of high SI in lesions on T1-weighted images; and tumor enhancement pattern. Seven patients had multiple tumors high in SI on T1-weighted images and six patients had solitary tumors. Seventy-two lesions were less than 1.5 cm in diameter and 35 lesions were more than 1.5 cm in diameter. Nine patients had solid malignant lesions and four patients had cystic malignant lesions. All tumors more than 1.5 cm in diameter were heterogeneously high in SI on T1-weighted images, and all tumors less than 1.5 cm were completely homogeneous or homogeneous with a small central hypointense focus. All tumors were more conspicuous on T1-weighted fat-attenuated images, both on excitation spoiled fat-suppressed spin-echo or on out-of-phase SGE images with the exception of one fat-containing hepatocellular carcinoma (HCC). In one patient with melanoma metastases and one patient with multiple myeloma nodules, appreciably more lesions were detected on out-of-phase SGE images. Causes of hyperintensity were considered to be either fat, melanin, central hemorrhage, or high protein content, all of which may be seen in a variety of tumors. Fat-attenuation techniques are helpful in the detection of these lesions.     

Liver metastases from pancreatic adenocarcinoma: MR imaging characteristics

PURPOSE: To describe the magnetic resonance imaging spectrum of appearances of liver metastases from pancreatic ductal adenocarcinoma. MATERIALS AND METHODS: We retrospectively evaluated the MRI exams performed between July 1996 and August 2001 in all patients who had liver metastases from pancreatic adenocarcinoma and histopathologic diagnosis from either the primary pancreatic tumor, liver metastases, or both. Sixteen patients were included in the study. All MR studies were performed at 1.5 T with a standard protocol including T1- and T2-weighted images and serial post-gadolinium spoiled gradient echo (SGE) images. Location, size, number, signal characteristics on T1- and T2-weighted images, and pattern of enhancement on serial gadolinium-enhanced SGE images were assessed. RESULTS: The diameter of metastases ranged from a few millimetres to 4 cm, and 12 patients (75%) had only lesions of 1.5 cm or less. Capsular-based liver metastases were found in 13 patients (81%) and three patients had only capsular-based lesions with a diameter under 1.5 cm. Hypervascular lesions were found in six patients (38%) and hypovascular lesions in 10 patients (62%). Perilesional enhancement was present in 10 patients (62%), with six patients (38%) having ring perilesional enhancement and eight patients (50%) having wedge-shaped perilesional enhancement. CONCLUSION: On MR imaging, hepatic metastases from pancreatic adenocarcinoma show a range of enhancement patterns. Hypervascular metastases are not rare. Capsular based distribution, small diameter, and perilesional enhancement are common features. This retrospective study describes the MR imaging spectrum of appearances of liver metastases from pancreatic adenocarcinoma in patients with histopathologic confirmation of the diagnosis.     

MRI of carcinoid tumors: spectrum of appearances in the gastrointestinal tract and liver

The purpose of this study was to evaluate the spectrum of appearances of gastrointestinal carcinoid tumors at magnetic resonance imaging (MRI) and to elucidate patterns of appearances of carcinoid liver metastases on precontrast and postgadolinium images. The MR examinations of 29 patients (11 men, 18 women; age range, 33-87 years) with histologically confirmed gastrointestinal carcinoid tumors, representing our complete 9.5 years of experience with this entity, were retrospectively reviewed. Twelve patients had MR examinations prior to resection or biopsy of the primary tumor (preoperative group); 17 patients were imaged postsurgically (postoperative group). All MR studies were performed at 1.5 T and comprised T1-weighted spoiled gradient echo (SGE), T2-weighted fat-suppressed turbo spin echo, HASTE, and serial postgadolinium T1-weighted SGE sequences without and with fat suppression. Morphology, signal intensity, and contrast enhancement of primary tumors and of metastases to the mesentery, peritoneum, and liver were evaluated. Primary tumors were visualized in 8 of 12 patients and best demonstrated on postgadolinium T1-weighted fat-suppressed images. The appearance of primary tumors was a nodular mass originating from the bowel wall (4 of 12 patients) or regional uniform bowel wall thickening (4 of 12 patients) with moderate intense enhancement on postgadolinium images. In 4 of 12 patients the primary tumor was prospectively not seen. Mesenteric metastases, seen in eight patients, presented as nodular masses and were associated with mesenteric stranding in seven patients. A total of 156 liver metastases were evaluated in 16 patients. On precontrast T1- and T2-weighted images, 117 metastases (75%) were hypointense and hyperintense, respectively. A total of 146 metastases (94%) were hypervascular, showing moderate intense enhancement during the hepatic arterial phase, and 9 metastases (6%) were hypovascular. Twenty-three metastases (15%) were visible only on immediate postgadolinium images. MRI is able to demonstrate findings in carcinoid tumors, including the primary tumor, mesenteric metastases, and liver metastases. Liver metastases are commonly hypervascular and may be demonstrable only on immediate postgadolinium images.     

Quantitative mr imaging data in the evaluation of hepatic metastases during systemic chemotherapy

To identify changes induced by chemotherapy in hepatic metastases, 34 patients with metastases underwent magnetic resonance (MR) imaging before the start of systemic chemotherapy and monthly thereafter. The number, size, and morphologic patterns of the lesions and changes in quantitative parameters (signal-to-noise ratio [S/N], contrast-to-noise ratio, and signal intensity ratio) were evaluated and correlated with response to treatment and prognosis. After treatment, seven patients showed a partial response, 18 had stable disease, and nine had progressive disease. No relevant changes in the patterns of the lesions were observed. Quantitative data showed that patients with a good prognosis had an increase in S/N on T1-weighted images and a relative decrease on T2-weighted images; patients with a poor prognosis showed a decrease in S/N on T1-weighted images and an increase on T2-weighted images. The differences between patient groups were significant for both T1- and T2- weighted images. This study demonstrates the value of MR imaging in follow-up of liver metastases and suggests the usefulness of quantitative MR imaging data.     

Invited. Hepatitis,cirrhosis, and hepatoma

Virus hepatitis and liver cirrhosis are found at high incidence in Asia, and they require not only biochemical examination of blood but also subsequent imaging, because they are often complicated by hepatocellular carcinoma (HCC). It is, therefore, very important to know the specific appearances of hepatitis, liver cirrhosis, and HCC when we diagnose these diffuse liver diseases. Liver necrosis due to severe hepatitis is seen as high intensity on T2-weighted spin echo images. Regeneration is seen as low intensity on T2-weighted images. Morphologic and pathologic changes of cirrhotic liver are well demonstrated by MR imaging techniques. Fibrotic septum with inflammatory cell infiltration or rich pseudo bile duct show high intensity on T2-weighted images, and regenerating nodules shows low intensity. Gradient echo images show regenerating nodules with iron deposition as low-intensity nodules due to susceptibility artifact. MRI also has the potential to evaluate function of diffuse liver disease, cirrhosis, and hepatitis. MRI can visualize and diagnose HCC objectively. Dynamic MRI is very useful for diagnosing HCC. It is also applied for evaluation of effect after transcatheter arterial chemoembolization, because it shows enhancement only in the viable region at an arterial phase. MRI is less invasive and is thus an extremely important form of liver imaging.     

Malignant lesions of the liver identified on T1- but not T2-weighted MR images at 1.5 T

The authors reviewed their 21/2-year experience with a magnetic resonance (MR) imaging protocol for a 1.5-T MR imager that included T2-weighted fat-suppressed spin-echo, T1-weighted breath-hold gradient-echo, and serial dynamic gadolinium-enhanced T1-weighted gradient-echo imaging to identify histologic types of malignant liver lesions more apparent on T1- than on T2-weighted images. MR images of 212 consecutive patients with malignant liver lesions were reviewed. T2-weighted, T1-weighted, and dynamic contrast-enhanced T1-weighted images were examined separately in a blinded fashion. Seven patients demonstrated liver lesions (lymphoma [two patients] and carcinoid, hepatocellular carcinoma, colon adenocarcinoma, transitional cell carcinoma, and melanoma [one patient each]) on T1-weighted images that were inconspicuous on T2-weighted images. In all cases, the lesions were most conspicuous on T1-weighted images obtained immediately after administration of contrast agent. Histologic confirmation was present for all seven patients. The consistent feature among these lesions was that they were hypovascular, due either to a fibrous stroma or to dense monoclonal cellularity. These results suggest that in some patients with hypovascular primary neoplasms, the lesions may be identified only on T1-weighted images, and that immediate postcontrast T1-weighted images are of particular value in demonstrating lesions.     

Rapidly enhancing hepatic hemangiomas at MRI: Distinction from malignancies with T2-weighted images

The purpose of this study is to describe a subset of atypical hepatic hemangiomas that enhance rapidly and diffusely and to determine whether heavily T2-weighted images could distinguish between atypically enhancing liver hemangiomas and hypervascular malignancies. A retrospective search of MR records identified seven patients with liver hemangiomas that demonstrated diffuse early enhancement and 23 patients with biopsy-proven malignant liver lesions that were hypervascular on dynamic gadolinium-enhanced MR images. Quantitative analysis of signal intensity measurements was performed on the T2-weighted images, heavily T2-weighted (TE < 140), and dynamic gadolinium-enhanced images. Blinded reader comparison of the T2-weighted images and gadolinium-enhanced images was performed. Hypervascular hemangiomas enhanced to a greater degree than hypervascular malignant liver lesions on the early phase gadolinium-enhanced images. Perilesional parenchymal enhancement was demonstrated in five cases of rapidly enhancing hemangiomas. Signal intensity and contrast-to-noise ratios on the heavily T2-weighted images of the hemangiomas were significantly greater than that of the hypervascular malignant lesions (P < .05). Hemangiomas were differentiated from the hypervascular malignant liver lesions with high accuracy (97–100%) by three blinded readers based on the T2-weighted images. A subset of hemangiomas have atypical rapid diffuse enhancement on dynamic gadolinium-enhanced images. These atypical hemangiomas can be distinguished from hypervascular malignant liver lesions on T2-weighted MR images.     

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.     

Liver lesion detection,characterization, and effect on patient management: Comparison of single-phase spiral CT and current MR techniques

This study compares liver lesion detection, characterization, and effect on patient management between single-phase spiral CT and MRI using spoiled gradient echo (SGE), T2-weighted fat-suppressed spin echo, and serial post gadolinium SGE. All patients with suspected liver lesions who underwent spiral CT and MRI within a 1-month period between January 1993 and September 1996 were included in the study. Spiral CT and MRI were interpreted prospectively in a blinded fashion by separate individual experienced investigators, and lesion detection and characterization were determined. Confirmation was obtained by surgery (6 patients), biopsy (18 patients), imaging follow-up (36 patients), or combined reading of all imaging studies and clinical follow-up (29 patients). Effect on patient management was determined by combined chart review and interview of the patients' physicians and by retrospective clinical assessment performed by a surgical oncologist and medical oncologist separately. Eighty-nine patients were included in the study. Regarding true positive lesion detection, 295 and 519 lesions were detected on spiral CT and MR images, respectively, which was significantly different on a patient-by-patient basis (P < .001). More lesions were detected on MR than on spiral CT in 44 of 89 patients (49.4%), and 11 of these 44 patients had lesions shown on MRI in whom no lesions were apparent on CT images. No patients had true positive lesions shown on spiral CT that were not shown on MRI. Regarding lesion characterization, 129 and 466 lesions were characterized on spiral CT and MRI images, respectively, which was significantly different on a patient-by-patient basis (P < .001). More lesions were characterized on MR than CT images in 67 patients (75.3%). Regarding effect on patient management, chart review with physician interview demonstrated that findings on MRI provided information that altered patient management as compared with findings on spiral CT in 57 patients. Retrospective clinical evaluation by the surgical and medical oncologist showed that MRI was considered to have a greater effect on patient management than spiral CT in 58 and 55 patients, respectively. Comparing current MRI technique to single-phase spiral CT, MRI detected more lesions in 49.4% and characterized more lesions in 75.3% of patients investigated for focal liver disease. MRI had a greater effect on patient management in each of the three methods than singlephase spiral CT in more than 61% of patients.     

Human fascioliasis: MR imaging findings of hepatic lesions

Our objective was to describe MR imaging findings of liver lesions in human fascioliasis. The MR imaging of the liver was performed in 29 patients with fascioliasis. Seventeen patients were women and 12 were men, with a mean age of 47.5 years (age range 17–75 years). Hepatic lesions were grouped into five types based on their signal characteristics. Three patients had normal imaging findings. One or more lesions were observed in the other 26 patients. The lesion types and the frequency of appearances were as follows: hyperintensity of the liver capsule on T2-weighted images (n=16, 55.2%); ill-defined slightly hyperintense areas on T2-weighted images (n=18, 62.1%); lesions which were hypointense on T1-weighted and hyperintense on T2-weighted images (n=10, 34.5%); hypointense on T1-weighted images and centrally hypo- or hyperintense, surrounded by peripherally less hyperintense area on T2-weighted images (n=4, 13.8%); and hypointense foci or ill-defined hypointense areas on T1- and T2-weighted images (n=10, 34.5%). We describe the MR imaging features of the disease. Our findings may help the differential diagnosis in which fascioliasis should be added to the list. Electronic Publication     

Characterization of focal hepatic lesions with ferumoxides-enhanced MR imaging: utility of T1-weighted spoiled gradient recalled echo images using different echo times

PURPOSE: To evaluate the different signal characteristics of focal hepatic lesions on ferumoxides-enhanced MR imaging, including T1-weighted spoiled gradient recalled echo (GRE) images using different echo times (TE) and T2- and T2*-weighted images. MATERIALS AND METHODS: Ferumoxides-enhanced MR imaging was performed using a 1.5-T system in 46 patients who were referred for evaluation of known or suspected hepatic malignancies. One hundred and seven lesions (42 hepatocellular carcinomas [HCC], 40 metastases, 13 cysts, eight hemangiomas, three focal nodular hyperplasias [FNHs], and one cholangiocarcinoma) were evaluated. Postcontrast MR imaging included 1) T2-weighted FSE; 2) T2*-weighted GRE; 3) T1-weighted spoiled GRE using moderate (TE = 4.2-4.4 msec) TE; and 4) minimum (TE = 1.8-2.1 msec) TE. Signal intensities of the focal lesions were rated by two radiologists in conference as follows: hypointense, isointense or invisible, hyperintense, and markedly hyperintense. Lesion-to-liver contrast-to-noise ratio (C/N) was measured by one radiologist for a quantitative assessment. RESULTS: On ferumoxides-enhanced FSE images, 92% of cysts were "markedly hyperintense" and most of the other lesions were "hyperintense", and the mean C/N of cysts was significantly higher than that of other focal lesions. T2*-weighted GRE images showed most lesions with similar hyperintensities and the mean C/N was not significantly different between any two types of lesion. T1-weighted GRE images using moderate TE showed all FNHsand hemangiomas, 29 (69%) HCCs and eight (20%) metastases as "hyperintense". On T1-weighted GRE images using minimum TE, however, all HCCs and metastasis except one were iso- or hypointense, while all of the FNHs and hemangiomas were hyperintense. Ring enhancement was highly suggestive of malignant lesions, and was more commonly seen on the minimum TE images than on the moderate TE images. CONCLUSION: Addition of T1-weighted GRE images using minimum and moderate TE is helpful for characterizing focal lesions in ferumoxides-enhanced MR imaging.     

Mr imaging of hepatic nodular regenerative hyperplasia

Nodular regenerative hyperplasia (NRH), a rare condition that is commonly associated with noncirrhotic portal hypertension, is not well described in the MR literature. Three patients at two institutions were identified who had both abdominal MR imaging and pathologic evidence of NRH. All examinations were performed at 1.5 T and included axial T1- and T2-weighted spin-echo (SE) images. The MR studies were reviewed by two radiologists in consensus. Two patients had multiple liver lesions that had high signal components on T1-weighted images and were predominantly isointense with liver on the T2-weighted images. One patient had no focal lesions identified. NRH, when visualized on MR images, appears as multifocal masses with shortened Tl and T2 similar to liver. NRH should be considered in the differential diagnosis of hepatocellular tumors, especially in patients with a predisposing condition.     

Hepatic nodules in Budd-Chiari syndrome: imaging features

PURPOSE: To analyze the imaging features of nodules associated with Budd-Chiari syndrome. MATERIALS AND METHODS: The authors retrospectively studied images obtained in 23 patients with liver nodules who were being followed up for Budd-Chiari syndrome. Doppler ultrasonography was performed in all patients, computed tomography in 16, and magnetic resonance (MR) imaging in 20. The following lesion features were evaluated: location, number, size, vascularization, qualitative signal intensity at MR imaging, and homogeneity. Nodules were diagnosed on the basis of histopathologic findings or clinical and biologic data with no change at imaging during 2-year follow-up. RESULTS: All patients had histopathologic features of chronic Budd-Chiari syndrome. Four patients had hepatocellular carcinoma (HCC), with one to three lesions. The mean diameter of the largest HCC lesion in each patient was 7.3 cm. All HCC lesions were heterogeneous and had high signal intensity on T2-weighted MR images. Nineteen patients had multiple benign regenerative nodules, most of which were smaller than 4 cm. Most nodules were homogeneous and hyperintense on T1- and T2-weighted images. In 15 patients, nodules were hypervascular in the arterial phase. CONCLUSION: In patients with chronic Budd-Chiari syndrome, multiple (> 10) small (< 4-cm) lesions are suggestive of benignity.     

Characterization of Focal Liver Lesions with Superparamagnetic Iron Oxide-Enhanced MR Imaging: Value of Distributional Phase T1-Weighted Imaging

Objective

To determine the potential value of distributional-phase T1-weighted ferumoxides-enhanced magnetic resonance (MR) imaging for tissue characterization of focal liver lesions.

Materials and Methods

Ferumoxides-enhanced MR imaging was performed using a 1.5-T system in 46 patients referred for evaluation of known or suspected hepatic malignancies. Seventy-three focal liver lesions (30 hepatocellular carcinomas [HCC], 12 metastases, 15 cysts, 13 hemangiomas, and three cholangiocarcinomas) were evaluated. MR imaging included T1-weighted double-echo gradient-echo (TR/TE: 150/4.2 and 2.1 msec), T2*-weighted gradient-echo (TR/TE: 180/12 msec), and T2-weighted turbo spin-echo MR imaging at 1.5 T before and after intravenous administration of ferumoxides (15 mmol/kg body weight). Postcontrast T1-weighted imaging was performed within eight minutes of infusion of the contrast medium (distributional phase). Both qualitative and quantitative analysis was performed.

Results

During the distributional phase after infusion of ferumoxides, unique enhancement patterns of focal liver lesions were observed for hemangiomas, metastases, and hepatocellular carcinomas. On T1-weighted GRE images obtained during the distributional phase, hemangiomas showed a typical positive enhancement pattern of increased signal; metastases showed ring enhancement; and hepatocellar carcinomas showed slight enhancement. Quantitatively, the signal-to-noise ratio of hemangiomas was much higher than that of other tumors (p < .05) and was similar to that of intrahepatic vessels. This finding permitted more effective differentiation between hemangiomas and other malignant tumors.

Conclusion

T1-weighted double-echo FLASH images obtained soon after the infusion of ferumoxides, show characteristic enhancement patterns and improved the differentiation of focal liver lesions.     

MRI of pancreatic tumors

MRI employing current imaging techniques is able to detect various pancreatic tumors well, and is able to stage and characterize tumors accurately. This review article describes various current MR techniques emphasizing breath hold spoiled gradient echo (SGE) imaging, fat suppression, dynamic gadolinium administration and MR cholangiographic techniques. Pancreatic ductal adenocarcinomas are generally low signal intensity on T1-weighted and T2-weighted images and enhance poorly on immediate post gadolinium SGE images. Islet cell tumors are generally low signal intensity on T1-weighted images, high signal intensity on T2-weighted images and enhance intensely on immediate post gadolinium images. The appearances of less common tumors is also described. Received 23 September 1996; Revision received 14 November 1996; Accepted 22 November 1996     

MRI in focal liver disease: A comparison of small and ultra-small superparamagnetic iron oxide as hepatic contrast agents

The purpose of this study was to compare small and ultrasmall superparamagnetic iron oxide particles (SPIO and USPIO, respectively) as MR contrast agents for the evaluation of focal hepatic disease. In two different patient groups (SPIO [n = 53], USPIO [n = 27]), with focal liver disease (metastases, hepatocellular carcinoma [HCC], hepatocellular adenoma [HCA], and focal nodular hyperplasia [FNH]), spin-echo T1- and T2-weighted images (T1WI, T2WI) were obtained at 1.0T, before and after intravenous contrast administration. The percentage signal-to-noise ratio (SNR) change and lesion-to-liver contrast (LLC) were measured and statistically compared. The liver decreased in signal intensity (SI) after SPIO administration (?28%) and increased after USPIO administration (+16%) on T1WI. On T2WI, the liver decreased in SI on postcontrast images with both agents (?78% SPIO, ?73% USPIO). This difference was not statistically significantly different (P ? .07). Both SPIO and USPIO provided >500% improvement in LLC on T2WI. On T1WI, LLC was increased in metastases (120%) and HCC (325%) with SPIO. Post-USPIO, LLC was increased on T1WI only in metastases (>500%). Both SPIO and USPIO show excellent hepatic uptake, presumed secondary to reticuloendothelial activity, based on the degree of %SI change seen in the liver after administration of contrast on T2WI. However, USPIO preparations exhibit blood pool activity that may aid in further characterization of focal liver lesions, as is evidenced by their greater T1 effect in the liver and in some focal liver lesions.     

Hepatocellular carcinoma after systemic chemotherapy: gadolinium-enhanced mr measurement of necrosis by volume histogram

As a preliminary study, we measured the necrosis of advanced hepatocellular carcinoma (HCC) by volume histogram after systemic chemotherapy and correlated it with clinical data. Five patients with advanced HCC secondary to chronic hepatitis and cirrhosis underwent pretreatment and posttreatment MR examination on a 1.5 T MR scanner following systemic chemotherapy. MR sequences included dynamic enhanced fast spoiled gradient echo 3D images. Clinical response to chemotherapy, as determined by MR images, was measured as changes of both the total tumor volume and the percent of tumor necrosis by volume histogram algorithm. Four of five patients had clinical improvement. Three of these patients had no or minimal change of tumor volume; however, there was an increase in tumor necrosis in follow-up MR image. One patient of five with no change in tumor necrosis had no response and died at 3 months. Serial MR images showed increased irregular necrosis of advanced HCC after systemic chemotherapy, but stable volume, in patients who responded clinically to systemic chemotherapy.     

Stomach diseases: MR evaluation using combined t2-weighted single-shot echo train spin-echo and gadolinium-enhanced spoiled gradient-echo sequences

The aim of this study was to describe the magnetic resonance (MR) appearances of diseases of the stomach using combined T1-weighted spoiled gradient-echo, T2-weighted single-shot echo train spin-echo and gadolinium-enhanced spoiled gradient-echo sequences. All patients with gastric diseases who underwent combined T2-weighted single-shot echo train spin-echo and gadolinium-enhanced conventional and fat-suppressed spoiled gradient-echo imaging between October 1, 1996 and March 1, 1999, and who had histological or other imaging proof of disease, were included in this study. This patient population was comprised of 40 patients with subsequently proven gastric abnormalities, including malignant tumors (25) or benign disease (15). The MRI sequences included T1-weighted, T2-weighted, and early and late gadolinium-enhanced spoiled gradient-echo (SGE) images. Evaluation was made of the following parameters: a) the ability to detect the disease process on MRI, by comparing the original prospective MR reports with the records of the pathology department; b) the MR appearance of a variety of gastric diseases; and c) the sequences that most clearly demonstrated abnormalities by retrospective review of the MR studies. MR images demonstrated 22 of 25 malignant tumors. Evaluation of the extent of the tumor was correctly shown in 22 of 25 tumors. Small-volume tumor (one patient with gastric adenocarcinoma, and one patient with lymphoma) and coexistent infiltrative adenocarcinoma and gastritis (one patient) rendered demonstration of tumor poor on MR images in three patients. Tumors were mildly hypointense on T1-weighted images and mildly hyperintense on T2-weighted images. Tumors enhanced in a heterogeneous fashion compared with background stomach wall, but they ranged from hypointense to hyperintense on early and late post-gadolinium SGE images. Regarding benign diseases, the changes of gastritis were evident in three of four cases. Gastritis appeared as increased mucosal enhancement that ranged from moderate to intense on early and late post-gadolinium SGE images. Imaging findings of the various entities are described in greater detail in the text. MR findings in a variety of neoplastic and non-neoplastic diseases of the stomach are described. Neoplastic diseases were consistently observed in most cases; however, small tumors and tumors coexistent with inflammatory changes were poorly evaluated. The changes of gastritis were demonstrated as increased enhancement of the gastric wall. J. Magn. Reson. Imaging 10:950-960, 1999.     

Multilocular cystic nephroma: MR imaging appearance with current techniques,including gadolinium enhancement

The purpose of the study was to define the MRI appearance of multilocular cystic nephroma (MLCN), using current MR techniques, including gadolinium (Gd)-enhanced sequences. Seven patients with MLCN underwent MR imaging with the following sequences: T1-weighted spin echo with fat suppression (TIFS, five patients), T1-weighted spoiled gradient echo (SGE, seven patients), T2-weighted fast spin echo (two patients), and Gd-enhanced TIFS (seven patients) and SGE (seven patients). MLCN was histologically proven by resection of the mass in six patients and by observation of typical imaging features with stability in appearance over a 6-month period in one patient. Lesion morphology and signal intensity (SI) features were retrospectively evaluated. MRI features of MLCN included a solitary cystic lesion with thin internal septations in six patients and a cluster of closely grouped cysts similar in size in one patient. Individual cystic spaces demonstrated SI, varying from low to high on T1-weighted images in three patients and demonstrated low-to-intermediate SI in four patients. Herniation of the lesions into the renal collecting system and thin enhancing septa were demonstrated in all patients. A complex cystic renal lesion with enhancing septa and herniation into the renal collecting system are the characteristic MR findings of MLCN. The direct multiplanar capability of MR may optimally show the relationship of MLCN to the renal pelvis and, thus, facilitate correct diagnosis.     

Adrenal hemorrhage after orthotopic liver transplantation: MR appearance

The purpose of this paper is to describe the MR imaging findings of right adrenal hemorrhage after orthotopic liver transplantation. Twenty-seven orthotopic liver transplantation patients underwent MR studies of the liver and/or biliary system. Patients were referred to MR examination because of suspected biliary complications ( n=22) or for evaluation of mass lesions ( n=5). The standard MR protocol included T1-weighted spin-echo (SE) or gradient-recalled echo (GRE) images and T2-weighted turbo SE (TSE) images with fat suppression. In addition, cholangiography pulse sequences and/or contrast-enhanced T1-weighted images were obtained according to specific indications. In 2 patients a right adrenal mass was detected at MR imaging. Three to 4 weeks after transplantation, the lesions were markedly hyperintense on T2-weighted images and showed a hypointense capsule. Follow-up MR examinations revealed a slight decrease in size and a change in morphology. Computed tomography examinations of these 2 patients, obtained 10 weeks after transplantation, showed resolution of the hemorrhage and transformation into a cystic lesion in one case and a complete resolution of the hemorrhage and a normal right adrenal gland in the other case. Adrenal hemorrhage after liver transplantation shows typical MR features and should not be mistaken for an adrenal tumor or a postoperative abscess.