Characterization of X-Ray Acoustic Computed Tomography for Applications in Radiotherapy Dosimetry

Abstract

X-ray acoustic computed tomography (XACT) is an emerging imaging modality that detects the acoustic waves induced in an object following irradiation by X-ray photons to form an image related to the energy deposited within the object. Since XACT images can be related to deposited radiation dose, it has been proposed that XACT could be an effective dosimetry tool for radiation therapy applications. This paper aims to systematically characterize XACT to determine its capabilities as a radiation dosimetry technique. XACT images of acceptable signal to noise ratio were formed at a dose level as low as 11.6 mGy, and the spatial resolution of XACT was measured to be 6 mm at a linac pulse duration of $4 ~{\mu }\text{s}$ . XACT was experimentally shown to be energy and dose rate independent. Changes in field size of 4 mm, field location of 2 mm, and field magnitude of 3% were detectable with XACT. The characteristics of XACT images were observed to be very sensitive to the transducer used for signal detection. Based on these results, XACT has the potential to be a powerful dosimetry tool for radiotherapy dosimetry applications, specifically for relative water tank measurements.