Hypervascular Hyperplastic Nodules Appearing in Chronic Alcoholic Liver Disease: Benign Intrahepatic Nodules Mimicking Hepatocellular Carcinoma

PURPOSE: Hypervascular hyperplastic nodules in those patients with chronic alcoholic liver disease and who are hepatitis B and C negative have recently been reported on. The purpose of this study was to correlate the radiologic and pathologic findings with the clinical significance of these hypervascular hyperplastic nodules in chronic alcoholic liver disease. MATERIALS AND METHODS: The study included eight hypervascular nodules of seven patients with chronic alcoholic liver disease, and these patients had abused alcohol for more than 20 years. Eight hypervascular nodules were seen on the arterial phase of dynamic CT scans, but the possibility of HCC was excluded pathologically (n=4) or clinically. The radiologic and pathologic findings, and the changes of these nodules on follow up CT scans were retrospectively analyzed. RESULTS: All nodules showed good enhancement on the arterial phase. The tissue equilibrium phase of the dynamic CT scans showed isodensity in seven patients and low density in one patient. Ultrasound scans revealed hypoechoic findings for three nodules, isoechoic findings for two nodules, hyperechoic findings for one nodule, and two nodules were not detected. Angiograms (n=6) showed late incremental tumor staining, and all the nodules were well seen on the sinusoidal phase. CT during hepatic angiography (n=4) showed well stained tumor. CT during arterial portography (n=4) showed no defect in three nodules and nodular defect in one nodule. The MR images (n=3) showed low signal intensity in two nodules and iso-signal intensity in one nodule on T2WI. Five of six cases for which follow up CT scans were performed showed decrease in size and one was disappeared. CONCLUSION: Radiologically, it is often difficult to differentiate the hypervascular hyperplastic nodules seen in the chronic alcoholic liver disease from hepatocellular carcinoma, and histological confirmation is needed for excluded hepatocellular carcinoma. However, late tumor staining during the sinusoidal phase without any blood supply by feeding vessels or any arterioportal shunt on the angiogram, isodensity during the tissue equilibrium phase of dynamic CT and low signal intensity on T2WI may suggest the presence of hypervascular hyperplastic nodule.

Hepatic Metastasis of Thymoma: A Case Report

Thymoma is the most common neoplasm in the anterior mediastinum, and extrathoracic involvement is rare. Moreover, cystic liver metastasis is extremely rare; few cases have been reported in the literature to date. We report here on a case of cystic liver metastasis of thymoma treated with surgical resection, describing the ultrasonography, CT and MRI findings.

Follow-up Results After Negative Findings on Unenhanced Hepatic MR Imaging for Hepatic Metastasis from Rectal Cancer

OBJECTIVE: To assess the follow-up results after negative findings on unenhanced hepatic MR imaging in rectal cancer patients who have undergone locally curative surgery. MATERIALS AND METHODS: From all pertinent imaging reports and medical records, we selected 255 patients who had negative results on unenhanced hepatic MR imaging. When selecting patients who had undergone curative resection, the following patients were excluded from the study: 1) patients in whom extrahepatic metastases were detected on preoperative staging work-ups, 2) patients in whom the surgery was judged to be non-curative due to peritoneal seeding or local aggressiveness. Cases with follow-up periods of less than 18 months were also excluded, as these cases were considered insufficient to confirm the negative outcomes. Thus, a total of 149 patients were ultimately enrolled in our study. The follow-up results of unenhanced MR imagings were assessed according to the assumption that the newly developed hepatic metastases had been false-negative lesions on preoperative MR image. RESULTS: During a median follow-up period of 29.3 months, 25 hepatic metastases were detected in 13 patients (8.7%), which indicated a negative predictive value of 91.3%. CONCLUSION: Unenhanced hepatic MR imaging provides a high negative predictive value with regard to the detection of hepatic metastasis in the preoperative evaluation of rectal cancer.

Double Contrast Media enhanced MRI with Ferumoxides-Gadolinium on Hepatocellular Carcinoma

PURPOSE: To evaluate the effects of Ferumoxides on Gadolinium (Gd) enhanced dynamic liver magnetic resonance imaging (MRI) in cirrhotic patients and also for the diagnosis of hepatocellular carcinoma (HCC). MATERIALS AND METHODS: 29 patients with liver cirrhosis were examined at 1.5T. 12 patients had HCC. The imaging protocol included GE T1 in and opposed phases, and a breath-hold TSE T2 before and 30-60 min following 0.05 ml/kg Ferumoxides. Four dynamic in-phase GE series were also acquired after an injection of 20 ml of Gd at 2 ml/sec. SNR and CNR were calculated for liver lesion relative to the muscle and background liver respectively. Statistical analysis was performed using the paired t-test. RESULTS: The SNR of the liver decreased by 8.6+/-1.20 (p<0.001) after Ferumoxides injection. At the peak of the Gd effect, the liver increased by 6.09+/-1.15 relative to the post Ferumoxides, but it was not significantly different from the pre-Ferumoxides study (p<0.01). Although there was no significant change in post Ferumoxides SNR of HCC, CNR of HCC relative to the liver increased by 7.54+/-1.61 (p<0.05). After the Gd injection, CNR of HCC increased by 15.6+/-3.87 (p<0.05). CONCLUSION: The administration of Ferumoxides made HCC CNR increase, and it canceled the effect of Gd enhancement of the cirrhotic liver. The combination of Ferumoxides and Gd makes HCC CNR increase.

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.

Optimal Pulse Sequence for Ferumoxides-Enhanced MR Imaging Used in the Detection of Hepatocellular Carcinoma: A Comparative Study Using Seven Pulse Sequences

OBJECTIVE: To identify the optimal pulse sequence for ferumoxides-enhanced magnetic resonance (MR) imaging in the detection of hepatocelluar carcinomas (HCCs). MATERIALS AND METHODS: Sixteen patients with 25 HCCs underwent MR imaging following intravenous infusion of ferumoxides. All MR studies were performed on a 1.5-T MR system, using a phased-array coil. Ferumoxides (Feridex IV) at a dose of 15 micro mol/Kg was slowly infused intravenously, and axial images of seven sequences were obtained 30 minutes after the end of infusion. The MR protocol included fast spin-echo (FSE) with two echo times (TR3333-8571/TE18 and 90-117), singleshot FSE (SSFSE) with two echo times (TR infinity/TE39 and 98), T2*-weighted gradient-recalled acquisition in the steady state (GRASS) (TR216/TE20), T2*-weighted fast multiplanar GRASS (FMPGR) (TR130/TE8.4-9.5), and T2*-weighted fast multiplanar spoiled GRASS (FMPSPGR) (TR130/TE8.4-9.5). Contrast-to-noise ratios (CNRs) of HCCs determined during the imaging sequences formed the basis of quantitative analysis, and images were qualitatively assessed in terms of lesion conspicuity and image artifacts. The diagnostic accuracy of all sequences was assessed using receiver operating characteristic (ROC) analysis. RESULTS: Quantitative analysis revealed that the CNRs of T2*-weighted FMPGR and T2*-weighted FMPSPGR were significantly higher than those of the other sequences, while qualitative analysis showed that image artifacts were prominent at T2*-weighted GRASS imaging. Lesion conspicuity was statistically significantly less clear at SSFSE imaging. In term of lesion detection, T2*-weighted FMPGR, T2*- weighted FMPSPGR, and proton density FSE imaging were statistically superior to the others. CONCLUSION: T2*-weighted FMPGR, T2*- weighted FMPSPGR, and proton density FSE appear to be the optimal pulse sequences for ferumoxidesenhanced MR imaging in the detection of HCCs.

Detection of Malignant Primary Hepatic Neoplasms with Gadobenate Dimeglumine (Gd-BOPTA) Enhanced T1-Weighted Hepatocyte Phase MR Imaging: Results of Off-site Blinded Review in a Phase-II Multicenter Trial

OBJECTIVE: To investigate the efficacy of gadobenate dimeglumine (Gd-BOPTA) enhanced MR imaging for the detection of liver lesions in patients with primary malignant hepatic neoplasms. MATERIALS AND METHODS: Thirty-one patients with histologically proven primary malignancy of the liver were evaluated before and after administration of Gd-BOPTA at dose 0.05 or 0.10 mmol/kg. T1-weighted spin echo (T1W-SE) and gradient echo (T1W-GRE) images were evaluated for lesion number, location, size and confidence by three off-site independent reviewers and the findings were compared to reference standard imaging (intraoperative ultrasound, computed tomography during arterial portography or lipiodol computed tomography). Results were analyzed for significance using a two-sided McNemar's test. RESULTS: More lesions were identified on Gd-BOPTA enhanced images than on unenhanced images and there was no significant difference in lesion detection between either concentration. The largest benefit was in detection of lesions under 1 cm in size (7 to 21, 9 to 15, 16 to 18 for reviewers A, B, C respectively). In 68% of the patients with more than one lesion, Gd-BOPTA increased the number of lesions detected. CONCLUSION: Liver MR imaging after Gd-BOPTA increases the detection of liver lesions in patients with primary malignant hepatic neoplasm.

In vivo Proton MR Spectroscopic Findings of Focal Hepatic Lesions: Initial Experience

PURPOSE: To investigate the in vivo proton MRS features of various focal hepatic lesions and to distinguish these features according to the involved. MATERIALS AND METHODS: Twenty-five hepatic lesions [hepatocellular carcinoma (n=7), cholangiocarcinoma(n=3), metastatic tumor (n=9), hemangioma (n=3), hepatic abscess (n=2), lymphoma (n=1)] underwent proton MR spectroscopy using a 1.5T unit and a localized proton STEAM sequence, without respiratory interruption, The findings of this in-vivo sequence were then reviewed, with particular attention to the presence and location of dominant peaks. RESULTS: In-vivo proton MR spectra were successfully acquired in all cases. A dominant lipid peak appeared in the MR spectra of the hepatocellular carcinomas, metastatic tumors, hepatic abscesses, lymphoma, one hemangioma and one cholangiocarcinoma(88%) at 1.3ppm, but not in two cholangiocarcinomas and one hemangioma. The spectral peaks of other metabolites appeared very irregular and even different in the same disease. CONCLUSION: In focal hepatic lesions, the spectra obtained during in-vivo proton MRS were useful, and a lipid peak was most frequent and dominant. Among the various neoplasms there were, however, no specific MR spectral features, and nor did such features vary according to the specific pathologic entity.

Assessment of Neoplastic Angiogenesis Using Perfusion-Weighted MR Imaging: Experimental Study in VX2 Carcinoma in Rabbits

PURPOSE: To evaluate the perfusion-weighted MR imaging findings of hepatic VX2 carcinoma in rabbits and to explain the perfusion characteristics of this condition by correlation with the histopathological findings. MATERIALS AND METHODS: Twelve New Zealand white rabbits, each weighing between 2.5 and 3.5 (mean) 3.1kg, were used in this study. Perfusion MRI using single-shot gradient-echo EPI was performed 7 -21 days after the injection of tumor cell suspension into the hepatic parenchyma by laparotomy. On the basis of the calculated enhancement ratio, the time-intensity perfusion curves for VX2 tumor and normal liver parenchyma were created, and the shapes of these curves, the time to maximum SI decrease, and the maximum enhancement ratio in each, were evaluated. To assess microvessel density in each VX2 carcinoma and in normal liver parenchyma, immunohistochenical study using factor VIII-related antigen was performed. RESULTS: A total of 15 tumors 1 -3 cm in diameter were revealed by MR imaging. The perfusion curve showed rapid decrement and immediate recovery of the signal intensity of VX2 carcinoma during the early arterial perfusion phase and slower decrement and gradual recovery of that of normal liver parenchyma during the late portal perfusion phase. In all cases, these were constant findings. The time to maximum signal intensity decrease was 13 -16 (mean, 15) secs in VX2 carcinoma and 28 -36 (mean, 32) secs in normal liver parenchyma (p<0.01). The maximum enhancement ratio of VX2 carcinoma and normal liver ranged from 27 to 84% (mean 47%) and from 36 to 82% (mean, 56%), respectively. Immunohistochemical study showed that the MVD of VX2 carcinoma was significantly greater than that of normal liver parenchyma(75 vs 17, p<0.01). CONCLUSION: Perfusion-weighted MR imaging appears to be a useful tool for the diagnosis of neoplastic angio-genesis, and thus holds promise differentiating liver tumors.

Comparison between Spiral CT and MR Imaging in Evaluation of Focal Hepatic Masses

PURPOSE: The main aim of this study was to compare spiral CT and MR imaging in the detection and characterization of focal hepatic masses. MATERIALS AND METHODS: Seventy-nine patients with 155 focal hepatic masses confirmed pathologically, or radiologically and clinically [hepatocellular carcinoma(HCC) (n =52), hemangioma (n=36), cysts (n =35), metastasis (n =27), intrahepatic cholangiocarcinoma (n =5)], underwent two- or three-phase spiral CT, and T1-, T2- weighted, and dynamic contrast-enhanced MR imaging. The detection and characterization of focal hepatic masses by these modalities were evaluated and compared. RESULT: The detection rates of spiral CT and MR imaging, respectively, were as follows: HCC, 81%(42/52) and 94%(49/52); hemangioma, 75%(27/36) and 100%(36/36); cysts, 80%(28/35) and 100%(35/35); metastasis, 67%(18/27) and 100%(27/27); and intrahepatic cholangiocarcinoma, 100%(5/5) and 100%(5/5). MR imaging was superior to spiral CT in mass detection of HCC, hemangioma, cysts, and metastasis (p < .05). The characterization rates of spiral CT and MR imaging, respectively, were as follows: HCC, 52%(27/52) and 71%(37/52); hemangioma, 67%(24/36) and 100%(36/36); cysts, 63%(22/35) and 100%(35/35); metastasis, 37%(10/27) and 100%(27/27); and intrahepatic cholangiocarcinoma, 40%(2/5) and 80%(4/5). In the mass characterization of HCC, hemangioma, cysts, and metastasis, MR imaging was superior to spiral CT (p< .05). CONCLUSION: In the detection and characterization of focal hepatic masses, including hepatocellular carcinoma, hemangioma, hepatic cyst and metastasis, MR imaging is superior to spiral CT.

Detectability of Hepatocellular Carcinoma: Comparison of Gd-DT PA-Enhanced and SPIO-Enhanced MR Imaging

PURPOSE: To compare the detectability of hepatocellular carcinoma (HCC) using superparamagnetic iron oxide (SPIO)-enhanced T2-weighted turbo spin echo (TSE), SPIO-enhanced T2*-weighted FISP, and dynamic Gd-DTPA-enhanced fast low-angle shot (FLASH) MR images. MATERIALS AND METHODS: In order to assess their hepatic lesions, 25 patients (20 men and 5 women) with HCC were enrolled in an MR study in which both gadolinium and SPIO were used. Since the lesions were most conspicuous during the phase of dynamic arterial dominant phase of dynamic gadolinium-enhanced imaging, this was the phase used for analysis. Images were analyzed qualitatively and quantitatively, and to compare the diagnostic value of gadolinium-enhanced imaging with that of SPIO-enhanced imaging for the detection of HCCs, a receiver-operated characteristic curve was obtained. RESULTS: Qualitative analysis revealed a significantly higher percentage of signal loss and a higher liver-lesion contrast-to-noise ratio on SPIO-enhanced FISP imaging than on SPIO-enhanced T2-weighted TSE imaging (p<0.05). It also showed that the lesions were most clearly visible on SPIO-enhanced FISP imaging(and signifi-cantlyso), followed by SPIO-enhanced T2-weighted TSE imaging, and dynamic gadolinium-enhanced imag-ing. Imaging artifacts were more prominent on SPIO-enhanced T2-weighted TSE than on SPIO-enhanced PISF imaging or dynamic gadolinium-enhanced imaging(p<0.05). According to ROC analysis, SPIO-enhanced T2-weighted turbo spin echo(TSE) or SPIO-enhanced FISP imaging achieved higher accuracy than did dynamic gadolinium-enhanced FLASH imaging(p<0.05). CONCLUSION: For the detection of hepatocellular carcinomas, SPIO-enhanced MR imaging is better than gadolinium-enhanced FLASH imaging.

Hemangioma and Hepatocellular Carcinoma: Distinction with Superparamagnetic Iron Oxide-Enhanced MR Imaging

PURPOSE: To compare liver hemangioma with hepatocellular carcinoma (HCC), as seen on superparamagneticiron oxide (SPIO)-enhanced MR images. MATERIALS AND METHODS: The study involved 30 patients with 51 focal hepatic mass lesions (31 hemangiomas, 20 HCCs). Breath-hold T1-weighted fast low angle shot (FLASH) and respiratory-triggered T2-weighted turbo-spin echo (TSE) images were obtained at 1.5 T before and after intravenous administration of SPIO particles. For quantitative analysis, percentage signal intensity change (PSIC) and contrast-to-noise ratio (CNR) of the lesions were calculated for T1-weighted FLASH and T2-weighted TSE before and after intravenous administration of SPIO particles. In addition, lesion conspicuity and imaging artifacts were analyzed qualitatively. RESULTS: After SPIO administration, percentage signal intensity increase on T1-weighted FLASH images was 73.0 +/-22.1% for hemangiomas and 21.8 +/-12.6% for HCCs, the difference being significant (p < 0.05). Taking a signal increase of 40% on postcontrast T1-weighted FLASH as the cut-off value, sensitivity and specificity for hemangiomas were 96.8% and 100%, respectively. In addition, the percentages of signal intensity loss on T2-weighted TSE images for hemangiomas and HCCs were 35.5 +/-17.2% and 0.2 +/-10.5%, respectively (p < 0.05). A comparison of lesion to liver CNR before and after SPIO infusion showed readings-for hemangiomas and HCCs, respectively - of 15.4 +/-6.0 and 4.7 +/-4.4 on T1-weighted FLASH images, and -2.6 +/-0.7 and 2.7 +/-4.4 on T2-weighted TSE images (p < 0.05). Qualitative analysis indicated that the conspicuity of HCCs was noticeably greater on postcontrast T2-weighted TSE images than on precontrast images (p < 0.05). CONCLUSION: The positive enhancement seen on T1-weighted FLASH images and the negative enhancement on T2 weighted TSE observed in liver hemangiomas after the administration of SPIO particles are valuable diagnostic features that can help characterize hemangiomas and differentiate them from HCCs.

Dynamic Images for Prediction of Therapeutic Efficacy of Hepatocellular Carcinoma Treated with Transcatheter Oily Chemoembolization

PURPOSE: To predict the therapeutic efficacy of transcatheter oily chemoembolization(TOCE) in the treatment. MATERIALS AND METHODS: We reviewed the findings of 24 dynamic CT or MR scans examined for the purpose of diagnosis before TOCE, and follow-up CT scans obtained after this procedure. In 24 patients (M:F=20:4) with a mean age of 52.2 years, 43 nodular HCCs with a diameter of 5 cm or less were present. The patients underwent double dynamic CT or MR imaging as one arterial phase 30 seconds after the intravenous injection of contrast media, and this was followed by a delayed phase 5 minutes fter injection. HCCs were then classified as one of four types: Type I, high and low attenuation or intensity during the arterial and delayed phase, respectively; Type II, iso- and low; Type III, iso- and high; and Type IV, high and iso-. In addition, we classified the degree of lipiodol accumulation by HCC nodules as either Grade 5 (fullmoon-like lipiodolization), Grade 2 (about 40%), or Grade 1 (about 20%), as seen on follow-up CT scans after TOCE. RESULTS: Type I provided an accuracy of 72.1% considering to more than 50% lipiodol accumulation. However, a single finding demonstrating high atenuation or intensity during the arterial phase gave an accuracy of 79.1% better than that of Type I. CONCLUSION: A finding of high attenuation or intensity during the arterial phase, as seen on dynamic CT or MR images, provides the best information about the therapeutic efficacy of HCCs treated by means of with TOCE.

Hepatic Cavernous Hemangioma in Cirrhotic Liver: Imaging Findings

OBJECTIVE: To document the imaging findings of hepatic cavernous heman-gioma 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 hypere-choic, 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.

Enhancement Pattern of Small Hepatic Hemangioma: Findings on Multiphase Spiral CT and Dynamic MRI

PURPOSE: To compare the enhancement characteristics of small hemangiomas seen on multiphase spiral CT anddynamic MR imaging MATERIALS AND METHODS: Thirteen patients with 20 hepatic hemangiomas less than 25mm indiameter underwent both multiphase spiral CT and dynamic MR imaging. All lesions were assigned to one of threeclassified into 3 categories according to the enhancement pattern seen on multiphase spiral CT : typical delayedpooling, atypical early enhancement, or continuous low attenuation. The enhancement patterns seen on spiral CT andon dynamic MRI were correlated. RESULTS: On CT scans, ten lesions (50%) showed delayed pooling. Six(30%) showedearly arterial enhancement and four(20%) showed continuous low attenuation. On delayed-phase MRI, all lesionsshowed delayed high signal intensity compared to adjacent liver parenchyma. Four of six lesions with earlyenhancement on CT showed peripheral globular enhancement on early arterial-phase MRI. CONCLUSION: On multiphasespiral CT scans, small hemangiomas can show variable atypical enhancement features. In this situation,contrast-enhanced dynamic MRI is helpful for the diagnosis of hemangiomas.

MR Imaging of Hepatocellular Carcinoma: Usefulness of Four-Phase Dynamic Imaging Including Early ArterialPhase

PURPOSE: To evaluate the usefulness of four-phase dynamic MR imaging technique by analyzing the imagingfeatures of hepatocellular carcinoma(HCC). MATERIALS AND METHODS: We reviewed four-phase dynamic MR images of 63lesions in 38 patients. MR imaging of the whole liver on gradient T1-weighted sequence was obtained at 10seconds(phase I), 35 seconds(phase II), 60 seconds(phase III), and 5 minutes(phase IV) after the start ofGd-DTPA(0.1mmol/kg) hand injection(3-4cc/sec) through the vein. We evaluated the degree of lesional contrastenhancement during each phase by comparing surrounding liver parenchyma, and analyzed signal intensity in lesionsover and less 2cm, respectively. RESULTS: The number of lesions showing high signal intensity compared withsurrounding liver parenchyma was 52(83%)during phase I, 30(48%) during phase II, 12(19%) during phase III, and 4(6%) during phase IV. During each phase, the number of lesions with signal intensity lower than that ofsurrounding liver parenchyma was 7(11%), 2(3%), 7(11%) and 21(33%), respectively. Thirty-four lesions wereenhanced only during phase I and eleven during only phase II. In tumors less than 2cm(n=40), more enhanced lesionswere during phase I(n=33) than more during phase II(n=16)(p=.0020). CONCLUSION: During each phase, four-phasedynamic MR imaging is useful for the effective detection of HCC showing varying degrees of contrast enhancement.

Comparison of Non-Breath-Hold T2-weighted Turbo Spin-Echo and Three Breath-Hold T2-weighted MR Images for Detection of Focal Hepatic Lesion

PURPOSE: The purpose of this study was to compare non-breath-hold T2-weighted turbo spin-echo (TSE) MR imaging with three types of breath-hold T2-weighted MR imaging (breath-hold TSE [BHTSE], half-Fourier single- shot TSE [HASTE], and true-fast imaging with steady-state precession [FISP]) for hepatic lesion detection. MATERIALS AND METHODS: T2-weighted MR images obtained using the above with the four sequences in 38 patients with 53 solid malignant and 90 non-solid benign hepatic lesions were retrospectively analyzed. Images were compared quantitatively (lesion-to-liver contrast-to-noise ratio and lesion detectability) and qualitatively (conspicuity of lesion and artifact). Statistical analysis involved the paired t-test for quantitative evaluation and Wilcoxon's signed rank test for qualitative evaluation. RESULTS: The values of lesion-to-liver contrast-to-noise ratios and lesion conspicuity for solid malignant hepatic lesions were better with non-breath-hold TSE imaging than with the three breath-hold T2-weighted sequences (p .05), and lesion detectability for non-solid benign lesions was similar (94% and 98%, compared with 91% and 96 %). CONCLUSION: In the cases of solid malignant hepatic lesions, the three breath-hold T2-weighted sequences were inferior to non-breath-hold TSE with regard to lesion-to-liver contrast-to-noise ratio and lesion detectability. Non-breath-hold TSE imaging should thus not be replaced by breath-hold T2-weighted imaging.

Comparison of Non-Breath-Hold T2-weighted Turbo Spin-Echo and Three Breath-Hold T2-weighted MR Images for Detection of Focal Hepatic Lesion

PURPOSE: The purpose of this study was to compare non-breath-hold T2-weighted turbo spin-echo (TSE) MR imaging with three types of breath-hold T2-weighted MR imaging (breath-hold TSE [BHTSE], half-Fourier single- shot TSE [HASTE], and true-fast imaging with steady-state precession [FISP]) for hepatic lesion detection. MATERIALS AND METHODS: T2-weighted MR images obtained using the above with the four sequences in 38 patients with 53 solid malignant and 90 non-solid benign hepatic lesions were retrospectively analyzed. Images were compared quantitatively (lesion-to-liver contrast-to-noise ratio and lesion detectability) and qualitatively (conspicuity of lesion and artifact). Statistical analysis involved the paired t-test for quantitative evaluation and Wilcoxon's signed rank test for qualitative evaluation. RESULTS: The values of lesion-to-liver contrast-to-noise ratios and lesion conspicuity for solid malignant hepatic lesions were better with non-breath-hold TSE imaging than with the three breath-hold T2-weighted sequences (p .05), and lesion detectability for non-solid benign lesions was similar (94% and 98%, compared with 91% and 96 %). CONCLUSION: In the cases of solid malignant hepatic lesions, the three breath-hold T2-weighted sequences were inferior to non-breath-hold TSE with regard to lesion-to-liver contrast-to-noise ratio and lesion detectability. Non-breath-hold TSE imaging should thus not be replaced by breath-hold T2-weighted imaging.

Value of MR Imaging after CT in Patients with Focal Hepatic Lesion

PURPOSE: To determine the usefulness of magnetic resonance imaging (MRI) after computed tomography (CT) inpatients with focal hepatic lesion. MATERIALS AND METHODS: We evaluated 100 patients with 103 focal hepaticlesions. The diagnosis of each lesion was made pathologically (n=19), or radiologically and clinically (n=84), andthe findings were as follows: he-mangioma (n=53), hepatocellular carcinoma (n=17), metastasis (n=10), cyst (n=5),regenerative nodule (n=3), and adenomatous hyperplasia (n=3). The patients underwent conventional CT (n=25),two-phase spi-ral CT (n=17) or three-phase spiral CT (n=61). MRI was performed using conventional T1- andT2-weighted imaging and dynamic contrast enhancement. The value of MRI after CT was assigned to one of fourgrades, according to the consensus of three radiologists: grade I (decisive), grade II (helpful), grade III (notadditional), or grade IV (confused). RESULTS: The outcome of MRI of 103 lesions was grade I in 14 cases(14%), IIin 34 (33%), III in 49 (48%), and IV in 6 (6%). MRI was not helpful (grade III or IV) in 40% (10/25), 47% (8/17),and 61%(31/61) of lesions after conventional, two-phase spiral, and three-phase spiral CT, respectively. Grade IIIor IV lesions were present in 45% of hemangiomas (24/53), 59% of hepatocellular carcinomas (10/17), and 80% ofcases in which metastasis had occurred(8/10). CONCLUSION: MRI after CT in patients with focal hepatic lesion washelpful in less than half of all cases. It was particularly valuable for patients who did not undergo three-phasespiral CT and in whom hemangioma was suspected.

Assessment of Focal Liver Lesions with 4-Phase Dynamic FLASH MR Imaging: Usefulness of Early Image Acquisitionfor Characterization of Arterial Phase

PURPOSE: To document the usefulness of early image acquisition using the contrast-enhanced dynacic MR imagingfor characterization of various focal hepatic lesions during the arterial phase. MATERIALS AND METHODS:Seventy-nine patients with 145 focal liver lesions (71 hemangiomas, 59 hepatocellular carcinomas and 15metastases) underwent breathhold dynamic MR imaging using a fast low-angle shot sequence. After obtainingunenhanced T1-weighted images, four phase MR images were obtained 10, 35, 60 and 300 seconds after starting theinjection. Patterns of contrast enhancement were analyzed for each lesion, with an emphasis on first phase images. RESULTS: Forty-two of the 59 HCCs (71%) showed prominent contrast enhancement during the first phase. HCCssmaller than 2cm in diameter showed a more homogeneous enhancement pattern than those which measured 2cm ormore(24/25 vs 12/17;P<.05). Hemangiomas showed a globular enhancement pattern during the same phase in 51 of 71cases (72%), a finding which was more apparent in those whose diameter was 2cm or more(35/54 vs 16/17, p<.05).During the first phase of imaging, 12 of the 15 metastases showed peripheral enhancement of their thick rim. CONCLUSION: The use of early image acquisition on dynamic MR sequences is helpful in character-izing lesionsaccrding to their pattern of contrast enhancement.