2025/02/03 by Sébastien Gros, J. G. Bian, Gros, S. +11
Physics and Astronomy · #Advanced Radiotherapy Techniques #FOS: Physical sciences #Medical Physics (physics.med-ph)
paper · pdf · doi:10.48550/arxiv.2502.01509
openalex publication_date 2025/02/03 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Objective: To propose a CBCT dose optimization method using readily available measurement equipment in radiation oncology departments. Approach: A 0.6cc air kerma (Kair) calibrated Farmer chamber measured Kair at isocenter for five default CBCT protocols (HEAD, PELVIS, LARGE PELVIS, THORAX, SPOTLIGHT) on a Varian TrueBeam linac. Imaging parameters were modified to reduce cumulative exposure by reducing projections (by 25%, 50%, 75%) in FDK reconstruction, or lowering single frame exposure by 25%, 50%, 70 to 75%. Cone Beam Dose Index (CBDI) and weighted CBDI (CBDIw) were measured in CTDI phantoms to correlate with Kair. Image quality was assessed quantitatively (HU linearity, uniformity, low-contrast visibility, high-contrast resolution, spatial integrity) using Catphan604, and qualitatively via anthropomorphic phantoms. Results: A linear relationship between Kair, CTDI, and CBDIw was established. High-contrast resolution and spatial integrity were unaffected by dose reduction (R < 0.5), while low-contrast visibility strongly correlated with exposure (R > 0.75). HU uniformity and linearity remained stable (<40 HU deviation), except for LARGE PELVIS at <50% single-frame exposure. 80 to 50% dose reduction retained clinically acceptable image quality with minimal artifacts or noise. Significance: CBCT protocols on TrueBeam linacs were optimized for dose reduction. The method enables easy implementation by radiotherapy physicists without diagnostic physics equipment or expertise.