Clinical commissioning of a new patient positioning system, SyncTraX FX 4, for intracranial stereotactic radiotherapy

Background & Aims A new real‐time tracking radiotherapy ( RTRT ) system, the SyncTraX FX 4 (Shimadzu, Kyoto, Japan), consisting of four X‐ray tubes and four ceiling‐mounted flat panel detectors ( FPD s) combined with a linear accelerator, was installed at Uonuma Kikan Hospital (Niigata, Japan) for the first time worldwide. In addition to RTRT , the SyncTraX FX 4 system enables bony structure‐based patient verification. Here we provide the first report of this system's clinical commissioning for intracranial stereotactic radiotherapy ( SRT ). Materials & Methods A total of five tests were performed for the commissioning: evaluations of (1) the system's image quality; (2) the imaging and treatment coordinate coincidence; and (3) the localization accuracy of cone‐beam computed tomography ( CBCT ) and SyncTraX FX 4; (4) the measurement of air kerma; (5) an end‐to‐end test. Results & Discussion The tests revealed the following. (1) All image quality evaluation items satisfied each acceptable criterion in all FPD s. (2) The maximum offsets among the centers were ≤0.40 mm in all combinations of the FPD and X‐ray tubes (preset). (3) The isocenter localization discrepancies between CBCT and preset #3 in the SyncTraX FX 4 system were 0.29 ± 0.084 mm for anterior‐posterior, −0.19 ± 0.13 mm for superior‐inferior, 0.076 ± 0.11 mm for left‐right, −0.11 ± 0.066° for rotation, −0.14 ± 0.064° for pitch, and 0.072±0.058° for roll direction. the Pearson's product‐moment correlation coefficient between the two systems was >0.98 in all directions. (4) The mean air kerma value for preset #3 was 0.11 ± 0.0002 mG y in predefined settings (80 kV , 200 mA , 50 msec). (5) For 16 combinations of gantry and couch angles, median offset value in all presets was 0.31 mm (range 0.14–0.57 mm). Conclusion Our results demonstrate a competent performance of the SyncTraX FX 4 system in terms of the localization accuracy for intracranial SRT .