Abstract
The feasibility of accounting of the dose from kilovoltage cone‐beam CT in treatment planning has been discussed previously for a single cone‐beam CT (CBCT) beam from one manufacturer. Modeling the beams and computing the dose from the full set of beams produced by a kilovoltage cone‐beam CT system requires extensive beam data collection and verification, and is the purpose of this work. The beams generated by Elekta X‐ray volume imaging (XVI) kilovoltage CBCT (kV CBCT) system for various cassettes and filters have been modeled in the Philips Pinnacle treatment planning system (TPS) and used to compute dose to stack and anthropomorphic phantoms. The results were then compared to measurements made using thermoluminescent dosimeters (TLDs) and Monte Carlo (MC) simulations. The agreement between modeled and measured depth‐dose and cross profiles is within 2% at depths beyond 1 cm for depth‐dose curves, and for regions within the beam (excluding penumbra) for cross profiles. The agreements between TPS‐calculated doses, TLD measurements, and Monte Carlo simulations are generally within 5% in the stack phantom and 10% in the anthropomorphic phantom, with larger variations observed for some of the measurement/calculation points. Dose computation using modeled beams is reasonably accurate, except for regions that include bony anatomy. Inclusion of this dose in treatment plans can lead to more accurate dose prediction, especially when the doses to organs at risk are of importance.PACS numbers: 87.55.D, 87.55.K, 87.56.bd
Highlights
Cone-beam CT (CBCT) is rapidly becoming the standard equipment in radiation therapy departments employing image-guided radiation therapy (IGRT) for patient position verification
Computing and adding CBCT dose to patient treatment plans is the subject of discussion in the radiation therapy community
Addition of the dose from kilovoltage CBCT is currently not possible in clinical settings due to the inability of treatment planning systems to accurately model and compute this dose. This investigation examined the possibility of modeling and commissioning the beams produced by a kV CBCT system using a commercial treatment planning system and the degree of accuracy of such a dose calculation
Summary
Cone-beam CT (CBCT) is rapidly becoming the standard equipment in radiation therapy departments employing image-guided radiation therapy (IGRT) for patient position verification. There have been many studies on the dose delivered to patients from CBCT procedures. Among the studies that have focused on kilovoltage CBCT dose, Islam et al[2] measured doses in phantom on an Elekta X-ray volume imaging (XVI) unit and reported doses of up to 3.5 cGy per procedure. Song et al[6] measured doses for both Elekta and Varian units, and reported doses of up to 3.5 cGy for the Elekta and 8.3 cGy for the Varian unit. These investigations focused on the systems available at the time, and current systems may result in less dose than stated
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