Trials of transmission imaging using clinically used Ir-192 source for high-dose-rate brachytherapy

• Published in: Journal of instrumentation Vol. 17; no. 6; p. T06009
• Main Authors: Nagata, J., Yamamoto, S., Nakanishi, K., Noguchi, Y., Okudaira, K., Kataoka, J.
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.06.2022
• Subjects: Cameras; Charge coupled devices; Image acquisition; Image contrast; Image transmission; Instrumentation for gamma-electron therapy; Photons; Pinholes; Position measurement; Radiation dosage; Radiation therapy; Radiotherapy concepts; Scintigraphy and whole-body imaging; Spatial resolution; Time measurement; X-ray radiography and digital radiography (DR)
• ISSN: 1748-0221; 1748-0221
• DOI: 10.1088/1748-0221/17/06/T06009

In high-dose-rate (HDR) brachytherapy, verification of an Ir-192 source's position during treatment is required. One of the methods for this used a high-energy pinhole gamma camera to image the position of the source, but the absolute position of the source cannot be measured. To confirm the absolute position, it will be useful to acquire the transmission image of a subject in addition to the gamma photon image at the same time without using an additional X-ray system. To measure the transmission images, we tried to use the high-energy gamma photons emitted from the Ir-192 source used for the therapy. We developed a high-energy gamma photon imaging system composed of 1-mm-thick Pr doped Gd 2 O 2 S (GOS), a surface mirror, and a cooled charge-coupled device (CCD) camera. The developed imaging system achieved transmission imaging of high-energy gamma photons by transporting the Ir-192 source in front of the imaging system. The spatial resolution of the imaging system was better than 2.4 mm FWHM with and without a 10-cm-thick acrylic block set between the imaging system and the source. Moderate spatial resolution and contrast images of phantoms were obtained with the system. For the dynamic imaging mode, continuous images of the phantoms were measured with 1-sec intervals. There was no observable difference in the transmission images by the movement of the Ir-192 source. Transmission imaging of subjects using an Ir-192 source for HDR brachytherapy could be achieved using our developed imaging system. The system offers a new method to measure the real-time transmission images of the subject during HDR brachytherapy.