Abstract
Stereotactic radiosurgery (SRS) unites with current state of art techniques have provided excellent conformity, precision, and versatility for small tumor lesions. Arguably the best known systems are the Gamma ray systems like GammaKnife and the linac based robotic systems like CyberKnife. However, GammaKnife systems are limited to only treating intracranial targets. In this study, we investigate a novel rotating gamma ray system for SRS of intracranial targets and stereotactic body radiation therapy (SBRT) of extracranial body sites as compared to the CyberKnife machine. The RT Pro planning system (version 1.00.4557, Prowess, Concord, CA) was used to generate treatment plans for a prototype CybeRay system for 12 patients, who were previously treated on the CyberKnife. The new CybeRay system (OUR United RT Group., Xian, China) has a rotation gantry containing 16 Co-60 sources focusing at the isocenter. The prototype implemented in RT Pro included 4 different changeable collimators while an improved version included 7 collimators. The treatment can also swing 35° in the superior direction. CybeRay is equipped with an electronic portal imaging device, a cone-beam CT system, and a 6 degrees of freedom couch. Treatment plans from both treatment systems were compared based on isodose distributions, dose volume histograms, conformity index (CI), and the estimated treatment time. CybeRay and CyberKnife results were compared using Wilcoxon signed-rank tests. The planned target volume (PTV) ranged from 2.7cc to 59.5cc. The estimated treatment delivery time for CybeRay plans ranged from 3.7-60.2 minutes as compared to 13-67minutes with Cyberknife (p=0.05). The mean value of CI was 1.23 for Cyberknife as compared to 1.27 for CybeRay (p=0.2). On the other hand, CybeRay was superior with regards to peripheral doses appearing as excessive isodose lines extending to distal normal tissues. To quantify the difference between the two systems, a ring structure (D5cm) was drawn at 5cm distant to the PTV. The maximum dose received by D5cm averaged over 12 patients was 7Gy for CybeRay and 13.4Gy for CyberKnife (p=0.0024). A newly designed rotating gamma ray machine was evaluated through a retrospective dosimetric study using patients previously treated on CyberKnife system. The new machine exhibited high precision stereotaxy and accurate target localization with promising dosimetric capabilities for stereotactic radiation therapy of extra-cranial lesions.Abstract 3565Vol (cc)Dose Gy/fxtreat timeCID5cmCRCKCRCKCRCKAdrenal2736/343.26421.291.188.718.911.850/360.2531.31.236.224.117.745/356.2521.161.2211.415.1Liver4.460/321.2341.191.194.220.44550/528.1381.091.0912.720.3pancreas7.527/311.6441.211.192.85.549.110/131.6381.381.141.53.110.210/145.5331.581.571.33.6Breast25.114/73.69131.211.211112.259.514/74.94191.211.366.28.8Lung12.648/425501.291.188.615.82.754/317.2671.371.259.213.1Mean29401.271.23713.4 Open table in a new tab
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