Photoacoustic tomography in a clinical linear accelerator for quantitative radiation dosimetry

Cancer is the second leading cause of death in the United States. Approximately half of all cancer patients receive radiation therapy, in which linear accelerators are used to deliver high doses of x-ray radiation to tumors, inducing cell death. X-ray energy deposition causes pressure changes that produce acoustic signals due to the photoacoustic effect. Here, clinical x-ray beams were directed at test objects made of antimonial lead and other metallic materials within a water tank. Photoacoustic signals were measured using a calibrated broadband hydrophone and validated using simulations in k-Wave. Linear and two-dimensional synthetic apertures were formed by mechanically scanning the x-ray source and test object within a single plane. Tomographic images of test objects, reconstructed from measured photoacoustic signals, show good agreement with object geometry. X-ray doses incurred by the test objects are mapped based on the reconstructed acoustic pressure sources and Gruneisen parameter of the material employed. Potential applications to in vivo dosimetry for x-ray and proton therapy, potentially enabling safer and more effective treatments, are discussed.Cancer is the second leading cause of death in the United States. Approximately half of all cancer patients receive radiation therapy, in which linear accelerators are used to deliver high doses of x-ray radiation to tumors, inducing cell death. X-ray energy deposition causes pressure changes that produce acoustic signals due to the photoacoustic effect. Here, clinical x-ray beams were directed at test objects made of antimonial lead and other metallic materials within a water tank. Photoacoustic signals were measured using a calibrated broadband hydrophone and validated using simulations in k-Wave. Linear and two-dimensional synthetic apertures were formed by mechanically scanning the x-ray source and test object within a single plane. Tomographic images of test objects, reconstructed from measured photoacoustic signals, show good agreement with object geometry. X-ray doses incurred by the test objects are mapped based on the reconstructed acoustic pressure sources and Gruneisen parameter of the material...