DOSIMETRIC AND CANCER RISK ASSESSMENT IN CONE BEAM COMPUTERIZED TOMOGRAPHY (CBCT)
Figure 1: Sagittal view of male voxel phantom in the CBCT MCNPX computational model (A). Organ doses (B) and lifetime risk (C) for Thorax CBCT during a complete course of IGRT treatment for lung cancer.
Cone-Beam CT (CBCT) provides 3D images of tumor anatomy, size and location for cancer treatment by Image-Guided Radiotherapy (IGRT). Despite its benefits, imaging doses from CBCT scans are a clinical concern due to additional exposure of healthy tissues surrounding the exposed target-organs. In this study, we were able to quantify the concomitant organ doses involved in a Thorax CBCT scan for lung cancer treatment and to estimate the corresponding radiological risk of cancer incidence. For that, MCNPX simulations to model the CBCT equipment and a male voxel phantom were used to calculate the organ doses. The total CBCT imaging dose was determined, assuming that at least one CBCT scan was performed per session, for a complete course of treatment for lung cancer (24 sessions). The mean organ dose was converted to cancer risk using the BEIR VII gender, age and tissue-specific risk coefficient for lifetime attributable risk (LAR) of radiation induced cancer incidence.