Optimizing signal intensity correction during evaluation of hepatic parenchymal enhancement on gadoxetate disodium-enhanced MRI: comparison of three methods.

OBJECTIVE To compare signal intensity (SI) correction using scale and rescale slopes with SI correction using SIs of spleen and muscle for quantifying multiphase hepatic contrast enhancement with Gd-EOB-DTPA by assessing their correlation with T1 values generated from Look-Locker turbo-field-echo (LL-TFE) sequence data (ER-T1). MATERIALS AND METHODS Thirty patients underwent Gd-EOB-DTPA-enhanced magnetic resonance imaging (MRI) in this prospective clinical study. For each patient, breath-hold T1-weighted fat-suppressed three-dimensional (3D) gradient echo sequences (e-THRIVE) were acquired before and 2 (first phase), 10 (second phase), and 20min (third phase) after intravenous Gd-EOB-DTPA. Look-Locker turbo-field-echo (LL-TFE) sequences were acquired before and 1.5 (first phase), 8 (second phase), and 18min (third phase) postcontrast. The liver parenchyma enhancement ratios (ER) of each phase were calculated using the SI from e-THRIVE sequences (ER-SI) and the T1 values generated from LL-TFE sequence data (ER-T1) respectively. ER-SIs were calculated in three ways: (1) comparing with splenic SI (ER-SI-s), (2) comparing with muscle SI (ER-SI-m), (3) using scale and rescale slopes obtained from DICOM headers (ER-SI-c), to eliminate the effects of receiver gain and scaling. For each of the first, second and third phases, correlation and agreement were assessed between each ER-SI and ER-T1. RESULTS In the first phase, all ER-SIs correlated weakly with ER-T1. In the second and third phases, ER-SI-c showed a stronger linear correlation with ER-T1 (r(2)=0.71-0.72, p<0.01) than did ER-SI-s (r(2)=0.37-0.39, p<0.01) or ER-SI-m (r(2)=0.30-0.41, p<0.01). CONCLUSION SI correction using scale and rescale slopes from DICOM data is the most acceptable algorithm for evaluating delayed-phase Gd-EOB-DTPA hepatic enhancement.