Positron imaging for verification of irradiation field during radiotherapy.

Aim of Study: The present study was designed to investigate the application of positron images from photonuclear reactions to verify the location of targeted radiation in vivo. Materials and Methods: The phantom study was conducted with distilled water, porcine muscle, porcine adipose tissue, and graphite; these subjects were irradiated separately with 50 MV photons generated by an MM50 Racetrack Microtron. The positron emission activity was measured using a Geiger counter, and the radioactive decay curves for each of the irradiated materials were then established. The positron emission tomography (PET) images of the three tissue models were also achieved using the same radiation conditions. The in vivo PET imaging study was also conducted in tumor-bearing rabbits. Results: Our results demonstrated that the PET imaging could be used to verify the position of the irradiation field in vivo. The dose distribution images of photonuclear reactions of C-11 and O-15 were uniform, using 2-Gy 50 MV photons. Conclusions: The factors influencing the half-life of radiation activity in various tissues were different from the first order kinetic reaction in physics.