Room: Room 205
Purpose: Kilovoltage Intrafraction Monitoring (KIM) is an innovative real-time image guidance approach to track six-degrees-of-freedom (6DoF) intrafraction tumour motion on a standard linear accelerator. This study assesses the geometric accuracy of KIM used in the multi-institutional TROG 15.01 Stereotactic Prostate Ablative Radiotherapy with KIM (SPARK) trial.
Methods: Data from 38 prostate cancer patients treated using KIM guidance at three different institutions were analyzed. Each patient had three gold fiducial markers implanted in the tumour to allow for motion tracking. The real-time KIM measurements were compared with motion measurements from simultaneously acquired kV/MV triangulated images. The kV/MV data were assumed to be the ground truth. The accuracy (mean) and precision (standard deviation) of the difference between KIM and the ground truth kV/MV measurements were analysed in each of the 6DoF. Additional analyses investigated the dependence on the treatment energy (6MV vs. 10MV FFF) due to faster gantry rotation speed and more treatment beam scatter with the 10MV FFF beam.
Results: The geometric accuracy was assessed for 176 SBRT fractions. The 6DoF geometric accuracy and precision of KIM was -0.02Â±0.4 mm, -0.18Â±0.2 mm and 0.02Â±0.6 mm for translation, and -0.08Â±1.2Â°, -0.13Â±0.9Â° and -0.07Â±0.5Â° for rotation in the LR, SI and AP directions respectively. In this dataset prostate motion exceeding 3, 5 and 7 mm was observed during 21.8%, 7.2% and 2.7% of the total treatment time. No correlation was found between gantry angle and geometric accuracy in any degree of freedom for 6MV (Ï? < 0.11) or 10MV FFF treatments (Ï? < 0.09).
Conclusion: For the first time, KIM has been successfully implemented for SBRT in a multi-institutional study with cancer targeting accuracy within sub-mm and sub-degree in 6DoF. The outcomes of this study demonstrate the potential for KIM to be integrated broadly across radiotherapy centres.
Funding Support, Disclosures, and Conflict of Interest: This work receives funding from Cancer Australia and Prostate Cancer Foundation. D T Nguyen is funded by an NHMRC and a Cancer Institute NSW Early Career Fellowship. P Keall is funded by an NHMRC Senior Principal Research Fellowship. P Keall and P Poulsen are named inventors of a granted patent.
Not Applicable / None Entered.