Cyberknife Robotik Kollu Lineer Hızlandırıcı Cihazında kV Görüntü Alma Sıklığının Tüm Vücudun Aldığı Radyasyon Dozuna Etkisi

Abstract

In this study, dose contribution result from the imaging systems for CyberKnife® were analyzed. Dose per image values were measured for four different energy and exposure (mAs) parameters. These doses were measured and compared with each other by placing TLD and Gafkromik film on the Alderson Rando phantom surface. To increase the precision of measuring systems, each measurement was repeated two times on 40 and 80 image sets, and a single image dose was obtained. The sensitivity of measurement systems were evaluated against two-fold increase in the number of the images. Doses per image for TLD measurements taken by 90 kV energy are 0.12 and 0.82 mGy, respectively, for 10 and 90 mAs. For 120 kV energy , these values are 0.41 and 2.68 mGy, respectively, for 10 and 90 mAs. Doses per image for Gafchromic film measurements taken by 90 kV energy are 0.17 and 0.84 mGy, respectively, for 10 and 90 mAs. For 120 kV energy , these values are 0.46 and 2.73 mGy, respectively, for 10 and 90 mAs. The dose per image values, for both measurement systems, were increasing in case of the energy increase. When the energy was increased, the dose per image values were getting closer to each other. No significant change in dose per image even if the number of images were doubled. Measurement systems responded more sensitively in low doses. The higher values were obtained from measurements of the Gafchromic film because of the spatial resolution and the tissue equivalent was better than the TLD. This difference was more pronounced in low energies. The dose per image for each energy increased with the factor of 2.45 (2.54-2.32) while shifting the mAs parameter with the factor of three. As a result, the surface dose of X-ray imaging depends on the parameter couple kV and mAs in CKS. The number of required image for each case varied with the location of a disease and CKS treatment options, i.e. breath (Syncrony Respiratory Tracking), vertebra bones (Xsight Spine Tracking), and cranial bones (6DSkull Tracking) tracking. For our department, cumulative real-time images used for patient has changed in the range of 40 and 150. This situation revealed the requirement of consideration of additional surface dose exposed by imaging process. Therefore, while we choose the optimal lowest tube parameters without compromising from the quality of imaging, also we use minimum number of images without compromising from the quality of treatment.