Impact of Single and High-Density Diode Merge Measurement on Snc Arccheck for SBRT Plans Psqa
Abstract
Purpose
To investigate the difference in gamma passing rate and dose profile of measurement of patient specific quality assurance (PSQA) of SBRT plans using the SNC ArcCHECK in single measurement and high-density diode merge measurement.
Methods
A retrospective study consisting of 31 SBRT plans delivered on Elekta Versa linac with Agility MLC. Plans comprised of various anatomical regions (head and neck to pelvis) delivered using 6FFF and 6X beam energies. SNC ArcCHECK was used with SNC Patient (v8.0) to acquire single and merged measurement. The two measurements were evaluated using gamma analysis against composite dose calculated in Raystation (2024A) using 2D Gamma with 3% dose difference, 2mm distance to agreement criteria and 10%-90% dose threshold. Difference in gamma passing rate (GPR) between two measurement was evaluated against PTV size and plan modulation factor and diode ratio between two measurement was evaluated against gamma analysis dose threshold.
Results
Minimal difference for GPR was found between single and merged diode measurement with -0.03%±0.37% and 0.51%±0.34% raw and absolute difference, respectively. Plan modulation and PTV size did not indicate correlation to GPR difference between two measurements (R2=0.06, with positive and R2=0.01 with negative correlations, respectively). Finally, the diode ratio between two measurements decreased with higher GA dose threshold, 1.99, 1.93, 1.78 and 1.64 for 10%, 50%, 75% and 90% threshold respectively.
Conclusion
We have examined the difference in PSQA measurement from the two acquisition techniques. Minimal difference was found the GPR between two suggesting that for large PTV or less complex SBRT plans single measurement should be sufficient. Future work will focus on determining a more rigorous a cutoff threshold for recommending the use of merged diode measurement and examine the dose distribution in context more sophisticated analysis (e.g., Fourier analysis).