Evaluation of HCC response to locoregional therapy: Validation of MRI-based response criteria versus explant pathology.
PURPOSE The purpose of this work was to determine the technical feasibility and value of dynamic subtraction (postcontrast-precontrast) magnetic resonance (MR) imaging for the assessment of hyperintense lesions on precontrast T1-weighted images in the cirrhotic liver. METHODS One hundred four hyperintense lesions on T1-weighted precontrast and arterial phase postcontrast images were subjected to analysis of their subtraction qualities depending on the lesion size, location and/or the degree of misregistration between the source images in 27 different MR imaging sets. RESULTS The quality of subtraction images was always diagnostic for lesions larger than 2 cm in diameter (n=8) but not diagnostic for 73% (40 of 55 lesions) of small subcentimetric lesions. Thirty-one subcapsular lesions always showed a variable degree of coregistration artifact. Only 3 of 35 lesions with a slice misregistration of 3 mm or more gave rise to subtraction images of diagnostic quality. For determining the contrast enhancement, the area under the receiver operating characteristic curve of 30 verified lesions was significantly larger (P <0.001) for subtraction images than for conventional arterial phase images. CONCLUSION Depending on the lesion size and/or location or the degree of misregistration between the source images, dynamic subtraction MR imaging can be useful for the characterization of hyperintense lesions on precontrast T1-weighted imaging.