Focal Liver Lesion Detection in Gadoxetic Acid-enhanced Liver MRI: Effects of Scan Delay, Hepatic Function, and Magnetic Field Strength

PURPOSE: To determine the effects of scan delay, hepatic function, and magnetic field strength on the performance of gadoxetic acid enhanced magnetic resonance imaging. MATERIALS AND METHODS: Gadoxetic acid enhanced MRI conducted in 72 patients with 10 minutes and 20 minutes delay were reviewed retrospectively. For quantitative analysis, liver-to-lesion signal difference ratio (SDR) was measured and compared according to scan delay time, hepatic function and magnetic field strength. For qualitative analysis, two board-certificated radiologists reviewed 10-minute delay and 20-minute delay images. The sensitivity and specificity of each reader was compared. RESULTS: The SDR of 20-minute images in non-cirrhotic patients was significantly higher (p 0.05) to 10-min delay images. In comparisons according to the magnetic strength, there was no significant difference between 1.5-T and 3.0-T systems. Comparisons of ROC curves showed no statistically significant differences in sensitivity and specificity between 10-minute and 20-minute delay images. CONCLUSION: An increase in the liver-to-lesion signal difference ratio was dependent on the patients' hepatic function but not dependent on the magnetic strength. There was no significant difference in sensitivity or specificity between the 10-minute and 20-minute delay images.

Dynamic MRI for Breast Cancer: Correlation with the Prognostic factors and the Time-Signal Intensity Curve

PURPOSE: We wanted to evaluate the relation of the kinetic MRI features of dynamic contrast-enhanced MRI with the histopathological prognostic factors of breast cancer. MATERIALS AND METHODS: Fifty-four lesions of breast cancer patients were evaluated with using a 1.5 T MR scanner. The dynamic studies were performed in the axial plane with using T1 High Resolution Isotropic Volume Examination (THRIVE) so we obtained the time signal intensity curves. By considering the early peak signal intensity, the maximal signal intensity, the pre-enhanced signal intensity and the last signal intensity, we calculated the absolute value, percentage, slope of enhancement and the washout. The time of the early peak signal intensity and the time of the maximal signal intensity were obtained. We classified the early and delayed enhancement patterns. The kinetic MR features were correlated with the histopathological findings (the histologic and nuclear grades, estrogen receptor, progesteron receptor, Ki-67, p53 and c-erb B2). RESULTS: The early peak signal intensity slope was significantly correlated with the histologic grade (I versus II, III), and the Ki-67 (p=0.045, p=0.009). Ki-67 was also significantly correlated with the time of the peak signal intensity and the time of the maximal signal intensity (p=0.009, p=0.045). CONCLUSION: Some of the parameters of the time-signal intensity curve of dynamic MRI were associated with the prognostic factors, so these MRI signs may be useful to noninvasively identify prognostic factors in the future.