Exhibit Hall | Forum 6
Purpose: Radiation dosimetry plays an important role in radiation therapy to ensure that radiation dose is accurately delivered to the tumor. Despite wide use in clinical intervention, in-line verification of the delivered dose in tumor is still absent in the clinic, making precision radiotherapy challenging. X-ray-induced acoustic computed tomography (XACT) has recently been proposed as an imaging method for use in in-tumor dosimetry. While XACT has been studied for relative dosimetry, it has not been studied for its potential for quantitative dosimetry. The aim of this study was to investigate the accuracy of XACT to quantitatively reconstruct dose in-tumor during radiotherapy.
Methods: We have developed a model-based image reconstruction algorithm to quantify radiation dose in tumors using XACT imaging. Both 3D simulations and experimental measurements have been performed for in-tumor dosimetry with XACT imaging. Two imaging techniques, back projection, and the developed model-based image reconstruction algorithm, are used to reconstruct the dose distribution, have been compared throughout the simulations and experiments. The reconstructed dose was calibrated before comparing it to the PDD profile. Experimental signal was acquired from a 4cm×4cm radiation field at depths of 6, 8, and 10cm beneath the water surface. The acquired signal was processed before reconstruction to achieve accurate results.
Results: Applying model-based reconstruction algorithm with non-negative constraints successfully achieved quantitative radiation dose in a 3D simulation study. The reconstructed quantitative dose matches well with the PDD profile after calibration in experiments. We have also shown that XACT images can be displayed as pseudocolor maps of acoustic intensity, which correspond to different radiation doses in the clinic.
Conclusion: Our results show that the XACT imaging by model-based reconstruction algorithm is considerably more accurate than the dose reconstructed by back projection. With proper calibration, XACT is potentially applicable to the clinic for absolute in-tumor.
Funding Support, Disclosures, and Conflict of Interest: Research reported in this publication was supported by the National Cancer Institute of the National Institutes of Health under Award Number (R37CA240806), American Cancer Society (133697 RSG 19 110 01 CCE) funds, and UCI Chao Family Comprehensive Cancer Center (P30CA062203).