Cyberknife® X-Sight® Vertebra Takip Sisteminin Vertebra Dışı Lezyonlarda Uygulanabilirliğinin Araştırılması

Abstract

One of devices which uses the ablative dose for the Stereotactik body radiation theraphy (SBRT) is CyberKnife® Stereotactic Radiosurgery System. This device, has different tracking system from other devices. This systems have high precision for tracking. In this study , X-Sight™ spine tracking system and Synchrony™ tracking system have been used. In these days, X-Sight™ spine tracking system is used on the targets which are far from spine. But when its going away from a spine, especially in abdomen, tissues are affected by respiratory induced motion. On this study, X-Sight™ spine tracking system, outside of spinal lesions its enforceability has been investigated. For this, it is thought to have been subjected to motion at various amplitudes for the target at various distances from the spine the measurements were made using these two tracking systems. For X-Sight™ spine tracking system, the measurements have been taken to see the effect at distance, 1 cm, 2 cm, 3 cm from spine with 8 mm movement amplitude for 6 sn breath cycle time and for angular motion, 45˚ angle with 1 cm, 2 cm, 3 cm distances from spine for 6 sn breath cycle time 8 mm movement amplitude and for 11˚ anglular motion with spine, 1cm from spine with 2 mm movement amplitude, 2 cm from spine with 4 mm movement amplitude and 3 cm from spine with 8 mm amplitude. Some measurements have been taken with Synchrony™ tracking system as there are many studies on high and low amplitudes, on this study only the measurements have been taken for 1 cm, 2 cm, 3 cm distances from spine with 8 mm movement amplitude for 6 sn breath cycle time. All this measurement taken with GafChromic™ EBT3 films and the BrainLab® ExacTrac gating phantom. In the dosimetric analysis, GafChromic™ EBT3 films compared with the original treatment planing system datas(TPS). By using X-Sight™ spine tracking system, the amplitude stays constant when its getting away from spine for target, the minimum dose difference between TPS and EBT3 is % 11.1 and % 12.2. The biggest difference appears in this group. The measuremenet result of 45˚ angle with constant amplitude when distance is increased, the obtained results were very similar to the ones were taken vertical angle. When distance and amplitude is changed, in order to see dosimetrically difference comes out or not, on 11˚ angle, when we look at the dose alteration of movement, when amplitude is gone up, the dose difference between TPS and EBT3 is increased significantly. We experience with this mostly on minimum dose. The alteration which is on minimum dose for 2 mm %3.1, for 4 mm %6.1, for 8 mm %11.2. Any measurement taken with X-Sight spine tracking system could not past the gamma analysis. When we look at the measurements which were taken by Synchrony™ tracking system, the dose difference between TPS and EBT3 all the measurements were very close to eachother which are on different distances. Maximum difference is found % 3,1. All measurement taken with Synchrony™ tracking system past the gamma analysis. As a result, if the user assumes that spinal lesions is not affected by the movement in abdominal region, X-Sight™ spine tracking system can be used while accepting the disadvantages mentioned. However it should be considered that respiratory movement affects abdominal region. Therefore, considering to avoid unnecessary large treatment volume in SBRT with ablative doses, X-Sight™ spine tracking system is not suitable to be used in trackingof the targets in attached to the spine. Instead of that, for abdominal lesions, we recommend the use of Fiducial based Synchrony™ tracking system.