Comparison of MRI pulse sequences for prediction of size of hepatocellular carcinoma at explant evaluation.

OBJECTIVE: The purpose of this study was to retrospectively compare the size of hepatocellular carcinoma (HCC) on images obtained using different MRI pulse sequences with the tumor size determined at pathologic evaluation of liver explant specimens. MATERIALS AND METHODS: Ninety-two patients with HCC who underwent contrast-enhanced liver MRI within 90 days before liver transplant were included. A single pathologist measured the dominant HCC in each case. In different sessions, two abdominal radiologists (readers 1 and 2) aware only of the location of the dominant HCC independently measured lesion size on images obtained using the following sequences: T2-weighted imaging; b-500 diffusion-weighted imaging; and arterial, portal venous, and equilibrium phases of contrast enhancement. Size measurements on MR images were compared with explant measurements by use of Pearson correlation coefficients, paired t tests, and Bland-Altman plots. RESULTS: Correlation with pathologic findings was highest for reader 1 for portal venous (r = 0.890) and equilibrium (r = 0.828) phase images and for reader 2 for arterial, portal venous, and equilibrium phase images (r = 0.842-0.860). Absolute error relative to pathologic size was lowest for reader 1 using portal venous (4.3 mm) and for reader 2 using portal venous and arterial phase images (both 4.7 mm). Systematic error for both readers was lowest with portal venous and equilibrium phase images (reader 1, systematic under-measurement of 0.5 mm in both sequences; reader 2, systematic over-measurement of 0.1 mm with portal venous phase images and systematic under-measurement of 1.1 mm with equilibrium phase images). Sequences in which reader 1 made systematic over-measurements were diffusion-weighted images, arterial phase images, and T2-weighted images (by 3.5, 2.9, and 1.6 mm). Reader 2 made systematic over-measurements using arterial phase and T2-weighted images (by 1.5 and 0.4 mm). CONCLUSION: The data suggest the arterial phase may be suboptimal for measuring HCC at MRI. Portal venous phase acquisition warrants further investigation as a potential standard approach for such measurements.

Utility of MRI features for differentiation of retroperitoneal fibrosis and lymphoma.

OBJECTIVE: The objective of our study was to retrospectively compare the MRI features of retroperitoneal fibrosis (RPF) and lymphoma presenting as confluent retroperitoneal soft tissue. MATERIALS AND METHODS: MRI studies of 31 patients (18 men, 13 women; mean age, 58.4 ± 15.8 [SD] years; 22 with RPF and nine with lymphoma) were evaluated. Two radiologists independently and in consensus evaluated all cases for an array of subjective imaging features. A third radiologist measured the size (i.e., the greatest dimension in the transverse plane) and apparent diffusion coefficient (ADC) value of the tissue. Features of RPF and lymphoma were compared using the Fisher exact test, Mann-Whitney test, and receiver operating characteristic (ROC) curve analysis. Interreader concordance was also calculated. RESULTS: The mean age of patients with lymphoma was significantly greater than that in cases of RPF (72.4 ± 13.3 [SD] vs 52.7 ± 13.2 years, respectively; p = 0.003). The MRI features significantly more common in patients with RPF were pelvic extension (p = 0.004) and medial ureteral bowing (p < 0.001). The MRI features significantly more common in cases of lymphoma were predominantly suprarenal location, perirenal extension, anterior aortic displacement, heterogeneity, and the presence of additional nodes (p < 0.001-0.043). Size was significantly greater in patients with lymphoma than in those with RPF (mean ± SD, 33.9 ± 17.3 vs 11.0 ± 5.7 mm; p < 0.001) and had an area under the curve (AUC) of 0.960; a size larger than 15 mm had sensitivity of 100% and specificity of 86.4% for the diagnosis of lymphoma. The ADC was significantly lower in lymphoma than in RPF (mean ± SD, 0.92 ± 0.17 vs 1.40 ± 0.38 × 10(-3) mm(2)/s; p = 0.003) and had an AUC of 0.904. An ADC of 0.955 × 10(-3) mm(2)/s or less had sensitivity of 83.3% and specificity of 89.5% for the diagnosis of lymphoma. Interreader concordance for subjective features was very good to excellent (range, 80.6-100%). CONCLUSION: MRI features may be helpful in distinguishing between RPF and lymphoma.