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.     

Nodular sarcoidosis of the liver and spleen: Appearance on MR images

Small nodular lesions in the liver and spleen have been reported as an infrequent manifestation of sarcoidosis. Five patients with this appearance on either dynamic contrast material—enhanced computed tomographic (CT) or ultrasound scans underwent magnetic resonance (MR) imaging with and without dynamic gadolinium enhancement. The lesions were relatively uniform in size, ranging from 0.5 to 1.5 cm. On CT scans, they were hypoattenuating relative to surrounding parenchyma. On MR images, the lesions were hypointense relative to background parenchyma with all sequences. No substantial enhancement was observed in the lesions, although lesion conspicuity decreased over time on serial postcontrast images. Lesion conspicuity was greatest on either T2-weighted fat-suppressed (T2FS) images or early-phase dynamic contrast-enhanced images. Abdominal adenopathy was seen in three of the five patients and was hyperintense relative to liver on T2FS images in two and intermediate in intensity in one patient.     

Renal lesions: controlled comparison between CT and 1.5-T MR imaging with nonenhanced and gadolinium-enhanced fat-suppressed spin-echo and breath-hold FLASH techniques.

Nonenhanced and gadolinium-enhanced fat-suppressed spin-echo and breath-hold fast low-angle shot (FLASH) magnetic resonance (MR) imaging techniques were compared with iodine contrast material-enhanced computed tomography (CT) for the detection and characterization of renal masses. MR studies included T1-weighted fat-suppressed spin-echo (T1FS) and FLASH images followed by rapid injection of gadopentetate dimeglumine and a repeated FLASH image obtained at 1 second, a T1FS image at 30 seconds, and a FLASH image at 10 minutes. Of 38 patients, 17 had renal cysts, 18 had solid tumors, two had cortical scarring, and one had a hypertrophied column of Bertin. With contrast-enhanced T1FS, contrast-enhanced FLASH, and CT images, 114, 110, and 109 lesions, respectively, were detected. With MR imaging and CT, cysts smaller than 5 mm in diameter and solid tumors as small as 1 cm in diameter were detected. With combined contrast-enhanced FLASH and T1FS images, 112 lesions were correctly characterized as cystic or solid; with nonenhanced T1FS images, 110; with nonenhanced FLASH images, 107; and with nonenhanced CT, 103.     

Bowel disease: prospective comparison of CT and 1.5-T pre- and postcontrast MR imaging with T1-weighted fat-suppressed and breath-hold FLASH sequences.

The potential of new high-field-strength magnetic resonance (MR) imaging sequences to evaluate bowel disease was investigated and compared with computed tomographic (CT) studies. Thirty-two patients were studied, 14 with known or suspected gastrointestinal tumors and 18 with known or suspected bowel inflammatory conditions. T1-weighted fat-suppressed spin-echo and breath-hold FLASH (fast low-angle shot) images were obtained before and after intravenous injection of 0.1 mmol/kg gadopentetate dimeglumine. Pathologic confirmation was obtained by biopsy (n = 18), surgical excision (n = 8), or endoscopy (n = 6). CT and MR images were analyzed separately in a prospective fashion and reviewed by consensus. Information from CT and MR images was comparable in cases of confirmed bowel neoplasia. CT scans had better spatial resolution, while fat-suppressed gadolinium-enhanced MR images had better contrast resolution. In the 18 cases of bowel inflammation, CT scans showed concentric wall thickening in 16, while MR images showed concentric wall thickening in 14 and increased contrast enhancement in 17. Contrast enhancement was better appreciated on fat-suppressed images than on FLASH images. The results suggest that MR imaging may play a role in the evaluation of bowel disease.     

Hepatic Cavernous Hemangioma in Cirrhotic Liver: Imaging Findings

Objective

To document the imaging findings of hepatic cavernous hemangioma detected in cirrhotic liver.

Materials and Methods

The imaging findings of 14 hepatic cavernous hemangiomas in ten patients with liver cirrhosis were retrospectively analyzed. A diagnosis of hepatic cavernous hemangioma was based on the findings of two or more of the following imaging studies: MR, including contrast-enhanced dynamic imaging (n = 10), dynamic CT (n = 4), hepatic arteriography (n = 9), and US (n = 10).

Results

The mean size of the 14 hepatic hemangiomas was 0.9 (range, 0.5-1.5) cm in the longest dimension. In 11 of these (79%), contrast-enhanced dynamic CT and MR imaging showed rapid contrast enhancement of the entire lesion during the early phase, and hepatic arteriography revealed globular enhancement and rapid filling-in. On contrast-enhanced MR images, three lesions (21%) showed partial enhancement until the 5-min delayed phases. US indicated that while three slowly enhancing lesions were homogeneously hyperechoic, 9 (82%) of 11 showing rapid enhancement were not delineated.

Conclusion

The majority of hepatic cavernous hemangiomas detected in cirrhotic liver are small in size, and in many, hepatic arteriography and/or contrast-enhanced dynamic CT and MR imaging demonstrates rapid enhancement. US, however, fails to distinguish a lesion of this kind from its cirrhotic background.     

Superparamagnetic Iron Oxide Hepatic MR Imaging: Efficacy and Safety Using Conventional and Fast Spin-Echo Pulse Sequences

The purpose of this study was to evaluate the technical efficacy and safety of iv ferumozldes (Feridex^a), a superparamagnetic iron oxide contrast agent for detection of hepatic lesions using conventional spin-echo and fast spin-echo MR images. Precontract and postcontrast MR studies were performed on 25 patients with suspected focal hepatic lesions. Conventional Tl-and T2-weighted MR images, as well as fast spin-echo and fat suppressed fast spin-echo MR images, were evaluated. Quantitative assessment of the contrast agent was performed obtaining region of interest measurements of the liver, spleen, and selected hepatic lesions. The pulse sequences were also evaluated subjectively for overall image quality and a subjective assessment of lesion detection. The use of a superparamagnetic iron oxide contrast agent led to a decrease in hepatic signal intensity on all pulse sequences. Lesion-to-liver contrast increased 41.1%, 36.5%, and 32.0% on the conventional T2, fast spin-echo, and fat suppressed fast spin echo pulse sequences, respectively. Lesion-to-liver contrast decreased on the T1-weighted postcontrast pulse sequence by 23.8%. Despite Improvement in lesion-to-liver contrast, radiologists subjectively preferred the precontract sequences because of overall better image quality. At a dose of 10 μmol/kg, fenunoxides favorably impacts lesion-to-liver contrast, and may be useful in hepatic imaging, more with conventional T2-weighted spin-echo pulse sequences than with T2-weighted fast spin-echo pulse sequences.     

Mangafodipir trisodium‐enhanced MRI for the detection and characterization of focal hepatic lesions: Is delayed imaging useful?

PURPOSE: To investigate the usefulness of early and delayed hepatic MRI after mangafodipir trisodium (Mn-DPDP) administration for the detection and characterization of focal hepatic lesions. MATERIALS AND METHODS: Forty-five patients (31 males and 14 females, mean age = 61 years) with a total of 113 hepatic lesions (mean size = 3.5 cm) were included in this study (15 with hepatocellular carcinoma (HCC, N = 35), 20 with hepatic metastasis (N = 63), five with hemangioma (N = 10), three with cholangiocarcinoma (CC, N = 3), and two with liver abscess (N = 2)). T1-weighted gradient-echo MR images were obtained before and after Mn-DPDP administration, with a mean 18-hour delayed imaging. A qualitative analysis (including the size and signal intensity (SI)) and quantitative analysis (including enhancement and lesion-liver contrast-to-noise ratio (CNR)) were performed on pre- and postcontrast early and delayed MR images. RESULTS: Compared to postcontrast early imaging, 17 (48.6%) of 35 HCCs showed higher SI, 16 (45.7%) showed no SI change, and two (5.7%) showed lower SI on delayed imaging. All 63 metastases, 10 hemangiomas, three CCs, and two abscesses showed no SI change. On delayed imaging, ring enhancement was noted in 53 metastases (84.1%), three hemangiomas (30.0%), and one abscess (50.0%), but was not seen in HCCs or CCs. Eight metastases (12.7%) also showed ring enhancement on postcontrast early imaging. No newly detected hepatic lesions were revealed on postcontrast delayed MR images compared to postcontrast early images. Regarding CNR, the HCCs showed a significant increase in CNR from postcontrast early to delayed images after administration of Mn-DPDP (P < 0.01). However, none of the metastases, hemangiomas, CCs, and abscesses showed a significant increase of CNR from postcontrast early to delayed images. CONCLUSION: Postcontrast delayed MR images after Mn-DPDP administration were helpful in distinguishing hepatocellular from nonhepatocellular lesions, but were not useful for lesion detection and had limited utility for lesion characterization, since benign and malignant hepatic lesions looked the same.     

同相位与反相位梯度回波T_1WI在肝脏的应用价值

目的　评估同相位与反相位梯度回波T1WI在肝脏应用的价值 ,尤其是评估其对肝内脂肪变的检测能力。方法　 76例病人采用屏气同相位与反相位T1W梯度回波序列对肝脏扫描。将76例病人分成 3组分析 :(1)肝内无占位病变组 ,8例 ;(2 )肝癌组 ,34例 ;(3)血管瘤或囊肿组 ,共 34例。对 2种序列的图像进行了定量分析。结果　 76例中发现 14例肝脂肪变 ,6 2例无脂肪变。在 14例肝脂肪变中 ,反相位MRI还显示了 4例低信号肿块周边环状高信号带 ,其中 3例肝癌 ,1例血管瘤。在肝脂肪变的反相位上显示肝与脾和病灶信噪比或对比信噪比值较同相位低 ,但肝与脾和病灶间信噪比 (SNR)或对比信噪比 (CNR)在同相位与反相位上均无显著性差异 (P >0 .0 5 )。结论　同相位与反相位对显示肝脏病变和对脂肪成分的诊断是有价值的。两者互补 ,缺一不可。为避免肝脏病变在T1WI上的误诊或漏诊 ,建议常规行同相位与反相位T1W扫描     

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.     

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.     

Small hepatic lesions found on single-phase helical CT in patients with malignancy: diagnostic capability of breath-hold, multisection fluid-attenuated inversion-recovery (FLAIR) MR imaging using a half-fourier acquisition single-shot turbo spin-echo (HASTE) sequence

PURPOSE: To evaluate the diagnostic capability of breath-hold, multisection fluid-attenuated inversion-recovery (FLAIR) imaging using a half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequence in combination with T2-weighted fast spin-echo (FSE) magnetic resonance (MR) sequences for small hepatic lesions found on CT in patients with malignancy. MATERIALS AND METHODS: This study included 48 patients with extrahepatic malignancy who underwent both CT and MR examinations. There were a total of 112 small hepatic lesions (73 cysts and 39 liver metastases, <2 cm in diameter) that showed low attenuation on enhanced CT. Three radiologists independently reviewed the CT and MR (FLAIR-HASTE and T2-weighted FSE) images and assigned a confidence level to their evaluation (cyst or metastasis) on a five-point scale. RESULTS: All three reviewers were significantly better able (P < 0.05) to differentiate small hepatic cyst from liver metastasis with combined FLAIR-HASTE and T2-weighted FSE images (Az values = 0.997-0.999) than with CT (0.917-0.932). The mean values of sensitivity, specificity, and accuracy were significantly higher (P < 0.001) for T2-weighted FSE with FLAIR-HASTE (96.6%, 96.8%, and 96.7%, respectively) than for CT (76.9%, 61.6%, and 67.3%, respectively). A confident diagnosis was rendered in 12 of 112 lesions (10.7%) on the basis of CT, and this rate increased to 83 of 112 (74.1%) on the basis of T2-weighted FSE and FLAIR-HASTE imaging. CONCLUSION: FLAIR-HASTE is considered to be an effective sequence for differentiating hepatic cysts from liver metastases without the use of a contrast agent. With FLAIR-HASTE one can confidently diagnose small hepatic lesions found on CT in patients with a malignancy.     

Small Cell Carcinoma of the Urinary Bladder: CT and MR Imaging Findings

Objective

Primary small cell carcinoma (SCC) is a rare aggressive malignancy of the urinary bladder, with identical histopathology to that of the lung. The treatment and prognosis of bladder SCC are somewhat different from those of more frequent transitional cell carcinoma. The purpose of this study was to analyze the CT and MR imaging findings of bladder SCC.

Materials and Methods

Six adult patients (five males and one female) with pathologically proven SCC of the urinary bladder who had undergone pelvic CT and/or MR imaging were included in this study. The radiologic findings were retrospectively evaluated in terms of tumor location, texture, calcification, depth of invasion, perivesical extension, lymph node involvement, and local or distant metastasis, by two radiologists, who established a consensus.

Results

CT and MR images depicted all tumors as large, ill-defined, relatively well enhancing, broad-based polypoid intramural masses with (n=3) or without (n=3) cystic portions. Their frequent location was posterior and trigonal (n=3). Calcification was found within one tumor, and lymphadenopathy in four. At T2-weighted MR images, the solid portion of the tumor was relatively hypointense. The stage at the time of diagnosis was C in three patients, and D1 in three. Follow-up imaging showed brain metastasis in one patient and liver metastasis in two.

Conclusion

On CT and MR images, SCC of the urinary bladder appeared as a large, enhancing, broad-based polypoid mass. It was stage C or higher, and lymph nodes and distant metastasis were frequent. T2-weighted MR images showed that the solid portion of the tumor was relatively hypointense. When radiologic examinations demonstrate a bladder tumor of this kind in adults, SCC of the urinary bladder should be included in the differential diagnosis.     

Detection of hepatic masses in patients with carcinoma: comparative sensitivities of sonography, CT, and MR imaging

To evaluate the sensitivity of sonography, CT, and MR imaging in the detection of hepatic masses in carcinoma patients, we conducted a prospective study of 75 consecutive patients with gastrointestinal tumors who were admitted for surgical resection of the primary tumor. Sonography was performed with convex transducers of 3.5 and 5.0 MHz. Three noninvasive CT techniques were used: unenhanced CT scans, the incremental bolus dynamic scanning technique, and delayed scanning 4-6 hr after bolus injection of 60 g of iodine. MR images (1.5 T) were acquired as presaturated T1- and T2-weighted spin-echo sequences and as breath-holding fast low-angle shot (FLASH) 60 degrees and FLASH 15 degrees sequences. As it is difficult to distinguish benign from malignant masses solely on the basis of morphologic criteria, the techniques for each imaging method were designed to detect and not to characterize hepatic lesions. Each examination was interpreted blindly, and the results were compared with surgical findings, intraoperative sonography, and biopsy of the liver as the gold standard. All focal hepatic masses verified at surgery, malignant or benign, were included in the analysis. Sixty-five (68%) of 95 focal hepatic masses were detected by CT, 60 lesions (63%) by MR, and 50 lesions (53%) by sonography. Although lesions 1-2 cm were shown almost equally well by CT and MR (74% and 77%, respectively), the detection rate of smaller lesions (less than 1.0 cm) decreased more drastically with MR (31%) than with CT (49%). Sonography had a sensitivity of only 20% with the smaller lesions. All imaging techniques had a sensitivity of 100% for focal hepatic masses larger than 2.0 cm. Our results show that CT has a higher overall sensitivity (68%) than MR and sonography for the detection of focal hepatic masses. When the results of the three procedures are combined, the overall sensitivity is 77%. This is unsatisfactorily low, as CT and MR have a size threshold of about 1.0 cm and are relatively unreliable for the detection of smaller lesions.     

MR Imaging of Orbital Inflammatory Pseudotumors with Extraorbital Extension

Objective

To demonstrate a variety of MR imaging findings of orbital inflammatory pseudotumors with extraorbital extension.

Materials and Methods

We retrospectively reviewed the MR features of five patients, who were diagnosed clinically and radiologically as having an orbital inflammatory pseudotumor with extraorbital extension.

Results

The types of orbital pseudotumors were a mass in the orbital apex (n = 3), diffuse form (n = 2), and myositis (n = 1). The extraorbital extension of the orbital pseudotumor passed through the superior orbital fissure in all cases, through the inferior orbital fissure in two cases, and through the optic canal in one case. The orbital lesions extended into the following areas: the cavernous sinus (n = 4), the middle cranial fossa (n = 4), Meckel''s cave (n = 2), the petrous apex (n = 2), the clivus (n = 2), the pterygopalatine fossa and infratemporal fossa (n = 2), the foramen rotundum (n = 1), the paranasal sinus (n = 1), and the infraorbital foramen (n = 1). On MR imaging, the lesions appeared as an isosignal intensity with gray matter on the T1-weighted images, as a low signal intensity on the T2-weighted images and showed a marked enhancement on the post-gadolinium-diethylene triamine pentaacetic acid (post-Gd-DTPA) T1-sequences. The symptoms of all of the patients improved when they were given high doses of steroids. Three of the five patients experienced a recurrence.

Conclusion

MR imaging is useful for demonstrating the presence of a variety of extraorbital extensions of orbital inflammatory pseudotumors.     

Malignant hepatic tumors: Changes on MRI after hepatic arterial chemoembolization – preliminary findings

This study describes the MR appearances of malignant hypervascular liver lesions pre- and post-hepatic-arterial chemoembolization, with correlation to serial imaging and clinical responses. Eight patients with malignant hypervascular liver lesions underwent pretreatment and posttreatment MR examination on a 1.5-T MR imager. MR sequences included T1-weighted spoiled gradient echo (SGE), T2-weighted fat-suppressed spin echo or turbo spin echo, and dynamic gadolinium-enhanced SGE images. All patients underwent pretreatment, initial posttreatment, and subsequent posttreatment MR studies. The histology of primary tumors included various types of hepatocellular carcinoma (HCC) (four patients: fibrolamellar HCC [one patient], HCC [two patients], mixed HCC/cholangiocarcinoma [one patient]) and liver metastases (four patients: untyped islet cell tumor [two patients], gastrinoma [one patient], carcinoid [one patient]). Response to chemoembolization was determined by three assessments: MR response, serial imaging response, and clinical response. The appearance of MR response to chemoembolization was determined based on the correlation with clinical and serial imaging response. The MR response of lesions that showed good clinical response included: increase in signal intensity on T1-weighted images (three patients), decrease in signal intensity on T2-weighted images (three patients), and negligible or minimal enhancement on immediate postgadolinium images (four patients) after chemoembolization. The most marked change in lesion appearance was observed in lesions < 1 cm, which had intense homogeneous enhancement on pretreatment MR studies and negligible enhancement on initial posttreatment MR examinations. MR response of lesions that showed moderate clinical response demonstrated a variety of lesion appearances from substantial change to minimal change. MR response of lesions that showed poor clinical response demonstrated no change in lesion appearances compared with the pretreatment MR study. Our results demonstrated change in appearance of liver lesions between pre- and post-hepatic-arterial chemoembolization MR studies. MR response correlated with response determined by serial imaging studies and clinical findings.     

Transient increased segmental hepatic enhancement distal to portal vein obstruction on dynamic gadolinium-enhanced gradient echo MR images

The purpose of the present study was to demonstrate the frequency of occurrence of transient increased segmental hepatic enhancement distal to portal veto obstruction in patients with a lobar (main branch) portal vein obstruction. MR images of all patients with main and lobar branch portal vein obstruction examined by dynamic gadolinium enhanced gradient echo MR images between December 1990 and July 1994 were reviewed retrospectively. All studies included T2-weighted imaging, Tl-weighted spoiled gradient echo‘fast low angle shot ([FLASH])’ and postgadolinium enhanced PLASH imaging at 1, 45, and 90 sec and 10 min. Fourteen patients were identified with portal vein obstruction which Included: six with main portal and right and left branch occlusion, six with right lobar, and two with left lobar. In the six patients with main portal vein obstruction, enhancement on 1-sec postgadolinium FLASH images was homogenous (three patients), diffusely heterogeneous (two patients), or peripherally hyperintense (one patient). In eight of eight patients with isolated obstruction of the right or left lobar portal vein, transient-increased segmental enhancement distal to portal vein occlusion was observed on immediate postcontrast images. Relatively high signal intensity of the involved segments was present on 1-sec images and liver parenchymal enhancement became more homogeneous by 45 to 90 sec in all cases. In conclusion, transient-increased segmental enhancement occurred in eight of eight patients with isolated right or left portal vein occlusion. We postulate that this effect occurs due to increased hepatic arterial blood flow in the presence of portal vein obstruction.     

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.     

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.     

Newly developed hepatocellular carcinoma (HCC) in chronic liver disease: MR imaging findings before the diagnosis of HCC

PURPOSE: The purpose of this work was to describe the initial magnetic resonance (MR) imaging findings obtained before an imaging diagnosis of overt hepatocellular carcinoma (HCC) in the chronically damaged liver. METHODS: One hundred fifty-two newly diagnosed HCCs diagnosed by dynamic computed tomography (n = 111) or by MR imaging (n = 41), in addition to digital subtraction hepatic arteriography, in 96 patients were subjected to analysis of their MR imaging features within the previous 2 years. RESULTS: Ninety-seven (64%) HCC cases showed no focal lesions distinguishable from background hepatic parenchyma in MR images taken before the indication of typical HCC. The remaining 55 (36%) lesions were readily identified in earlier images and were categorized into 3 groups: nonhypervascular lesions (category I, n = 6), lesions with partially hypervascular foci of "nodule-within-nodule" appearance (category II, n = 12), and homogeneously hypervascular and/or T2-weighted hyperintense lesions (category III, n = 37). The size and doubling time of category III lesions (0.7 cm, 154 days) were smaller and shorter than those of the other lesions (1.2 cm, 377 days). CONCLUSIONS: Before the imaging diagnosis of HCCs, the premalignant or early malignant lesions can be found on the prior MR images just in the minority of the lesions in the cirrhotic liver.     

MR imaging detection of calcified intracranial lesions and differentiation from iron-laden lesions.

Magnetic susceptibility variation caused by calcium permits limited detection of intracranial calcifications and/or their distinction from iron-laden lesions with spin-echo or gradient-echo magnetic resonance (MR) techniques. The magnetic susceptibility sensitivity of phase imaging has been used to detect iron-laden lesions. A new approach that combines the magnetic susceptibility sensitivity of both gradient-echo and phase imaging to yield greater imaging sensitivity to calcium is presented. Two-dimensional fast low-angle shot (FLASH) gradient-echo imaging with phase image reconstruction (gradient-echo phase [GEP]) was used at 1.0 and 1.5 T. Twelve patients with computed tomography-proved calcified intracranial lesions (greater than or equal to 200 HU) and seven patients with iron-laden intracranial lesions having a characteristic appearance on T1- and T2-weighted and FLASH MR images were studied. The GEP imaging technique helped detect calcified intracranial lesions (greater than or equal to 200 HU) and helped distinguish them from iron-laden lesions.