Parametric response mapping of contrast-enhanced biphasic CT for evaluating tumour viability of hepatocellular...

To determine the feasibility and role of parametric response mapping (PRM) for quantitative assessment of regional contrast-enhancement patterns in hepatocellular carcinoma (HCC).

Biphasic CT of 19 patients receiving repetitive conventional transarterial chemoembolisation (cTACE) for intermediate stage HCC were retrospectively analysed at baseline and follow-up at 3, 6, and 9 months. Voxel-based registration of arterial and porto-venous phases, with segmentation of the largest target lesion was performed. Frequency distribution plots of density-pairs of segmented voxels were generated. To differentiate necrotic, hypervascular and non-hypervascular tumour, and lipiodol/calcification, thresholds of 30, 100, and 300 HU were applied. Changes in density frequency plots over time were analysed and compared to response and assessment criteria (WHO, RECIST, EASL, mRECIST) and survival.

PRM was feasible in all cases. Tumour volumes and hypervascular/non-hypervascular volume ratio showed significant longitudinal decrease (p < 0.05). Hypervascular volume at baseline was inversely correlated to survival (R = -0.57, p = 0.005). The only predictive parameter following cTACE to show significant survival difference was the change of the viable/non-viable ratio (p = 0.044), whereas common response assessment criteria showed no significant difference in survival.

PRM allows a quantitative and more precise assessment of regional tumour vascularisation patterns and may be helpful for TACE treatment planning and response assessment.

• PRM allows more precise assessment of tumour vascularisation compared to conventional evaluation • PRM is beneficial for cTACE treatment planning and response assessment • PRM allows a quantitative assessment of regional contrast enhancement patterns.