Feasibility of a modified cone-beam CT rotation trajectory to improve liver periphery visualization during transarterial chemoembolization¹

Purpose: To compare liver coverage and tumor detectability by using preprocedural magnetic resonance (MR) images as a reference, as well as radiation exposure of cone-beam computed tomography (CT) with different rotational trajectories. Materials and Methods: Fifteen patients (nine men and six women; mean age 6 standard deviation, 65 years 6 5) with primary or secondary liver cancer were retrospectively included in this institutional review board-approved study. A modified conebeam CT protocol was used in which the C-arm rotates from +55° to 2185° (open arc cone-beam CT) instead of 2120° to +120° (closed arc cone-beam CT). Each patient underwent two sessions of transarterial chemoembolization between February 2013 and March 2014 with closed arc and open arc cone-beam CT (during the first and second transarterial chemoembolization sessions, respectively, as part of the institutional transarterial chemoembolization protocol). For each cone-beam CT examination, liver volume and tumor detectability were assessed by using MR images as the reference. Radiation exposure was compared by means of a phantom study. For statistical analysis, paired t tests and a Wilcoxon signed rank test were performed. Results: Mean liver volume imaged was 1695 cm3 6 542 and 1857 cm3 6 571 at closed arc and open arc cone-beam CT, respectively. The coverage of open arc cone-beam CT was significantly higher compared with closed arc cone-beam CT (97% vs 86% of the MR imaging liver volume, P = .002). In eight patients (53%), tumors were partially or completely outside the closed arc cone-beam CT field of view. All tumors were within the open arc cone-beam CT field of view. The open arc cone-beam CT radiation exposure by means of weighted CT index was slightly lower compared with that of closed arc cone-beam CT (25.1%). Conclusion: Open arc cone-beam CT allowed for a significantly improved intraprocedural depiction of peripheral hepatic tumors while achieving a slight radiation exposure reduction.