Physical characteristics of the novel transmission-target X-ray equipment for kilovoltage radiation therapy applications

Abstract

There are two types of X-ray devices: transmission-type and reflection-type. These two types rely on different techniques to generate X-rays. This study aims to explore physical characteristics of transmission-type anode X-ray device. The newly developed transmission-type X-ray device (NanoRay Biotech) was assessed, and the beam quality of the device was determined by measuring the half-value layer (HVL) and energy spectrum. Furthermore, this study measured the percentage depth dose (PDD) and flatness and symmetry using ionization chambers in the PTW MP3-s water tank, and all of the measurements of the field size on the entrance surface of the water phantom was set 10 by 10 cm2. The study also discusses the stability and linearity of the tube voltage (kVp) and the tube current (mAs) of the X-ray tube, and investigates the effect of aluminum (Al) filter on beam quality. The results show that at the same depth, when the source-to-surface distance was reduced, the PDD declined, while the symmetry of the lateral dose profile was within 3%. In addition, the dose output of the X-ray device increased with an increase in kVp or mAs. The HVL was 1.55 and 0.41 mm with and without the Al filter, respectively. The introduction of the filter helped reduce low-energy photons by 23.4% and increased the ratio of the characteristic radiation by 2.22% in the energy spectrum. With the filter, the device can effectively reduce low-energy photons, thereby decreasing the surface dose and increasing the ratio of characteristic radiation. The rapid decline in PDD made the device suitable for the clinical treatment of shallow tumors and the intraoperative radiation therapy for tumor beds.