Contrast-enhanced CT as a non-invasive alternative for lung shunt fraction estimation in hepatic transarterial radioembolization.

[BACKGROUND] Estimation of the lung shunt fraction (LSF) is an integral part of liver radioembolization treatment planning to prevent excessive lung irradiation from arterio-venous shunting in the liver. Tc macro-aggregated albumin (Tc-MAA) nuclear imaging is the standard method. Recent literature suggests that Tc-MAA nuclear imaging may be omitted in selected patient populations.

[PURPOSE] This study investigates the potential of contrast-enhanced computed tomography (CECT) as a non-invasive method for estimating LSF as an alternative for Tc-MAA nuclear imaging.

[MATERIALS AND METHODS] This single-center retrospective study included 30 consecutive patients who underwent Y radioembolization between January 2015 and December 2024, where both four-phase CECT and Tc-MAA planar imaging were performed within one month of each other. Hypervascular tumor enhancement was identified on the CECT by subtracting the portal venous phase from the arterial phase and applying an intensity threshold. Additional perfusion characteristics were captured. Statistical analysis assessed the agreement between the CECT-derived volume ratios and the LSF values derived from Tc-MAA imaging.

[RESULTS] The cohort consisted of 23 male and 7 female patients with a median age of 66 years (interquartile range: 58-71), diagnosed with hepatocellular carcinoma ( = 24), intrahepatic cholangiocarcinoma ( = 2), pancreatic neuroendocrine tumors ( = 2), metastatic colorectal cancer ( = 1), and lymphocyte carcinoma ( = 1). Regression of the hypervascular-tumor-to-perfused volume ratio on CECT against LSF from Tc-MAA imaging showed  = 0.95 ( < .001). In contrast, the correlation between tumor volume and LSF was  = 0.38 ( = .001). The root mean square error between the LSF estimated from CECT and that measured using Tc-MAA planar imaging was 3%.

[CONCLUSION] Hypervascular-tumor-to-perfused volume ratio computed from CECT may offer a suitable alternative to Tc-MAA nuclear imaging for LSF estimation in patients undergoing transarterial radioembolization.