166 - A Clinical Validation Study of Ionizing Radiation Acoustic Imaging (iRAI) for Real-Time Visualization of Radiation Therapy Dose in Liver Cancer Patients
Presenter(s)
W. Zhang1, D. W. Litzenberg2, Y. Huang1, S. W. Hadley1, I. Oraiqat3, K. W. Chang1, G. Gonzalez4, S. Dykstra1, M. Zhang1, E. G. Moros3, P. Carson1, I. El Naqa5, X. Wang1, and K. C. Cuneo2; 1University of Michigan, Ann Arbor, MI, 2Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, 3H. Lee Moffitt Cancer Center and Research Institute, Department of Radiation Oncology, Tampa, FL, 4Moffitt Cancer Center, Tampa, FL, 5H. Lee Moffitt Cancer Center and Research Institute, Department of Machine Learning, Tampa, FL
Purpose/Objective(s): Ionizing radiation acoustic imaging (iRAI) is a novel imaging technology with the potential to map the delivered radiation dose on anatomical structure in real time during external beam radiation therapy (RT) including conventional RT, FLASH-RT, proton therapy, and radiotherapy with heavy ions such as Carbon. This technology offers unprecedented opportunities for online monitoring of radiation’s interactions with tissues of interest, providing adaptive feedback for safe and personalized cancer treatment. This study aimed to evaluate the clinical feasibility of using iRAI to map the delivered dose in patients receiving RT with various treatment techniques, including 3D-comformal RT (3D CRT), Intensity Modulated RT (IMRT), and Volumetric Modulated Arc RT (VMAT).
Materials/Methods: The volumetric iRAI system, which consists of a custom-designed two-dimensional (2D) matrix transducer array with an integrated preamplifier array and driven by a clinic-ready (not FDA approved) ultrasound imaging platform, was developed. A total of 10 patients with intra-liver cancer were enrolled in a prospective clinical trial after providing informed consent and IRB approval. Patients were treated with stereotactic body radiation therapy (SBRT) using standard of care clinical techniques, with the addition of volumetric iRAI for real-time mapping of three-dimensional radiation dose deposition.
Results: The minimal detectable dose was low at approximately 10 cGy. The overall shape of the dose distribution and location of the dose deposition determined by iRAI matched well with the corresponding treatment plan. A gamma passing rate of 0.7597 ± 0.1112 and 0.9099 ± 0.0661 with a 10 mm/10% distance to agreement (DTA)/ dose difference (DD) suggest good agreement between the iRAI measurement and the treatment plan in both the liver volume and the planning target volume under current system resolution. A structural similarity (SSIM) value of 0.6284 ± 0.1678 demonstrates that the iRAI measurements have shown structural pattern agreement with the treatment plan within the planning target volume (PTV).
Conclusion: This study demonstrates the clinical feasibility of iRAI to monitor radiation dose delivery to deep targets in real-time during treatment. This information can be integrated into treatment delivery systems to improve safety and facilitate the adaptation of radiation therapy and warrants further development and optimization of iRAI technology.