Comparing HCC arterial tumour vascularisation on baseline imaging and after lipiodol cTACE: how do estimations of enhancing tumour volumes differ on contrast-enhanced MR and CT?

OBJECTIVES: In this study, pre-treatment target lesion vascularisation in either contrast-enhanced (CE) CT or MRI and post-treatment lipiodol deposition in native CT scans were compared in HCC patients who underwent their first cTACE treatment. We analysed the impact of stratification according to cTACE selectivity on these correlations. METHODS: Seventy-eight HCC patients who underwent their first cTACE procedure were retrospectively included. Pre-treatment tumour vascularisation in arterial contrast phase and post-treatment lipiodol deposition in native CT scans were evaluated using the qEASL (quantitative tumour enhancement) method. Correlations were analysed using scatter plots, the Pearson correlation coefficient (PCC) and linear regression analysis. Subgroup analysis was performed according to lobar, segmental and subsegmental execution of cTACE. RESULTS: Arterial tumour volumes in both baseline CE CT (R2 = 0.83) and CE MR (R2 = 0.82) highly correlated with lipiodol deposition after cTACE. The regression coefficient between lipiodol deposition and enhancing tumour volume was 1.39 for CT and 0.33 for MR respectively, resulting in a ratio of 4.24. After stratification according to selectivity of cTACE, the regression coefficient was 0.94 (R2 = 1) for lobar execution, 1.38 (R2 = 0.96) for segmental execution and 1.88 (R2 = 0.89) for subsegmental execution in the CE CT group. CONCLUSIONS: Volumetric lipiodol deposition can be used as a reference to compare different imaging modalities in detecting vital tumour volumes. That approach proved CE MRI to be more sensitive than CE CT. Selectivity of cTACE significantly impacts the respective regression coefficients which allows for an innovative approach to the assessment of technical success after cTACE with a multitude of possible applications. KEY POINTS: • Lipiodol deposition after cTACE highly correlates with pre-treatment tumour vascularisation and can be used as a reference to compare different imaging modalities in detecting vital tumour volumes. • Lipiodol deposition also correlates with the selectivity of cTACE and can therefore be used to quantify the technical success of the intervention.