[Dose Management and Estimation Model Development Using a Dose Area Product Meter during kV Planar Imaging in Image-guided Radiotherapy].

Abstract

Purpose: This study aimed to measure patient exposure dose during kilovoltage (kV) planar imaging in image-guided radiotherapy (IGRT) using a dose area product (DAP) meter and to estimate the DAP under unmeasured imaging conditions using two-dimensional cubic interpolation.

Methods: Dose measurements during kV planar imaging were performed using a DAP meter (VacuDAP duo; VacuTec Meßtechnik, Dresden, Germany) attached to the kV X-ray tube of the On-Board Imager mounted on a TrueBeam linear accelerator (Varian Medical Systems, Palo Alto, CA, USA). DAP was measured under various imaging conditions, with tube voltages ranging from 60 to 140 kV and tube currents from 2.5 to 20 mAs. A two-dimensional cubic interpolation based on the measured data was implemented to estimate the DAP for unmeasured imaging conditions.

Results: The deviation from linearity was relatively larger under low-dose conditions, with a maximum deviation of 1.8% at 100 kV and 2.5 mAs. Nevertheless, the overall DAP for each mAs value exhibited high linearity (R²=1.00). The relative error of the estimated DAP was within 2.0%.

Conclusion: The DAP meter was demonstrated to be effective for dose management in kV planar imaging in IGRT, and use of the two-dimensional cubic interpolation enabled accurate dose estimation even under unmeasured imaging conditions.