BACKGROUND AND PURPOSE: This study outlines the measured doses for three concomitant imaging modalities used in radiotherapy. MATERIAL AND METHODS: Doses were measured using thermo luminescent dosemeters within pelvis and thorax anthropomorphic phantoms for the Varian On Board Imager (OBI), Elekta X-ray Volume Imager (XVI) and Tomotherapy HiArt II systems. Organ sites were selected to include those organs which would be irradiated by the treatment beam during the therapy exposure. RESULTS: Doses for kilovoltage imaging systems are comparable within the pelvis phantom at 20-30 mGy. Thorax phantom doses are lower, especially where user specified protocols are used at 5-10 mGy. Tomotherapy doses are typically less than 10 mGy for both phantoms. CONCLUSIONS: Concomitant imaging dose is a small fraction of the therapy dose, however, for a high fraction technique, the imaging dose can become comparable to the therapy dose outside primary target volume. Recommendations for optimisation of imaging in radiotherapy are presented.
BACKGROUND AND PURPOSE: This study outlines the measured doses for three concomitant imaging modalities used in radiotherapy. MATERIAL AND METHODS: Doses were measured using thermo luminescent dosemeters within pelvis and thorax anthropomorphic phantoms for the Varian On Board Imager (OBI), Elekta X-ray Volume Imager (XVI) and Tomotherapy HiArt II systems. Organ sites were selected to include those organs which would be irradiated by the treatment beam during the therapy exposure. RESULTS: Doses for kilovoltage imaging systems are comparable within the pelvis phantom at 20-30 mGy. Thorax phantom doses are lower, especially where user specified protocols are used at 5-10 mGy. Tomotherapy doses are typically less than 10 mGy for both phantoms. CONCLUSIONS: Concomitant imaging dose is a small fraction of the therapy dose, however, for a high fraction technique, the imaging dose can become comparable to the therapy dose outside primary target volume. Recommendations for optimisation of imaging in radiotherapy are presented.