Room: Exhibit Hall
Purpose: SyncTraX FX4 (SFX4), a novel real-time tracking radiotherapy (RTRT) system with four X-ray tubes and flat panel detectors (FPDs), was installed at our institution for the first time in the world. The purpose of this study was to provide the first report on the commissioning of this system.
Methods: The following were performed to commission the SFX4 RTRT: 1) evaluation of dose linearity and reproducibility using an ionization chamber with and without gating; 2) evaluation of time delay using an oscilloscope based on AAPM Task Group 142; 3) comparison of dose distributions with and without gating using a GAFchromic film and a respiratory motion phantom for several gating windows; 4) evaluation of entrance surface dose (ESD) using an optical fiber dosimeter. Flattening filter (FF) and flattening filter free (FFF) modes were used for 6 and 10 MV X-ray beams.
Results: The approximate linearity between the monitor units (MUs) and electronic charges with and without gating were almost consistent for each beam, and the coefficients of variation in three measurements were within 1% in the conditions of MUâ‰¥3. The mean values of the beam-on and beam-off time delays between dose delivery and marker detection for all energy levels were 128.5 msec and 87.8 msec, respectively (tolerance in TG-142: <100 msec). From the gamma analysis (3 mm/3%), the dose distributions with gating (gating window: 1-5 mm) all agreed well (>90%) with those without gating. The ESD was 33.3 mGy/min in the worst case assuming a clinical use (30 fps, 100 mA, 110 kV).
Conclusion: We have demonstrated that this RTRT system performs competently by providing reasonable dosimetric accuracy. However, the beam-on time delay does not yet meet the criteria of TG-142. Further investigations are needed.
Funding Support, Disclosures, and Conflict of Interest: This research is financially supported by Shimadzu Co., Kyoto, Japan.