Feasibility of Yttrium-90 Radioembolization Dose Calculation Utilizing Intra-procedural Open Trajectory Cone Beam CT

Purpose: Dose calculation for transarterial radioembolization (TARE) with glass yttrium-90 (Y⁹⁰) labeled microspheres is based on liver lobe and tumor volumes, currently measured from preprocedural MRI or CT. The variable time between MRI and radioembolization may not account for relevant tumor progression. Advances in cone beam computed tomography (CBCT) allow for intra-procedural assessment of these volumes that avoids this factor. Liver lobe and hepatocellular carcinoma tumor volume measurements and dose calculations using intra-procedural CBCT were compared to those using preprocedural MRI in order to determine feasibility. Methods: Retrospective analysis was performed in 20 patients with proven hepatocellular carcinoma (HCC) who underwent planning angiography with open trajectory CBCT acquisitions prior to radioembolization, and an MRI performed within 6 weeks prior to treatment planning. Liver lobe and tumor burden volumes were measured based on CBCT using embolization planning and guidance software and measured on preprocedural MRI using standard volume analysis software. Y⁹⁰ doses were subsequently calculated using each measured volume. Comparisons of volume measurements and calculated Y⁹⁰ doses between the two modalities were evaluated for significance using paired t tests. Results: All target liver lobes and all tumors were completely depicted on CBCT. Mean liver lobe and tumor burden volumes measured on intra-procedural CBCT and preprocedural MRI showed no significant difference (p = 0.71). Mean calculated Y⁹⁰ dose based on each modality showed no significant difference (p = 0.18). Conclusions: Lobar and tumor volume measurement with CBCT is a reliable alternative to measurement with preprocedural MRI. Utilization of CBCT 3D segmentation software during planning angiography may be useful to provide up-to-date volume measurements and dose calculations prior to radioembolization.