Clinical assessment of dedicated SRS detector for dose verification in SBRT/SRS treatment plans: to establish clinical threshold with AAPM TG-218 recommendation

Stereotactic radiosurgery (SRS) and stereotactic body radiotherapy (SBRT) deliver high radiation doses with steep dose gradients near critical organs, demanding patient-specific quality assurance (PSQA) systems with sub-millimetre spatial resolution beyond conventional criteria. This study evaluated a high-resolution complementary metal oxide semiconductor detector for PSQA in SRS and SBRT, focusing on sensitivity to plan modulation and dose gradient accuracy. Forty clinical plans (20 SRS, 20 SBRT) were retrospectively analysed and measured using a dedicated stereotactic phantom which is myQA SRS. Gamma analysis was performed with strict spatial criteria. Correlations between gamma passing rates and modulation factor were assessed using Spearman’s rank correlation. Dose gradient accuracy was evaluated by comparing measured and calculated dose profiles. Mean gamma passing rates for all plans were 95.4% ± 5.1% for 3%/2 mm, 93.6% ± 5.9% for 4%/1 mm, and 89.9% ± 7.4% for 3%/1 mm criteria. A statistically significant inverse correlation between modulation factor and gamma passing rate was observed for stereotactic radiosurgery plans, strongest for the 3%/1 mm criterion (ρ = −0.620, p = 0.0035), while no significant correlation was found for stereotactic body radiotherapy plans. Dose profile analysis demonstrated excellent agreement in steep gradient regions, with coefficients of determination ranging from 0.91 to 0.998. The high-resolution detector accurately resolves steep dose gradients and small-field penumbras characteristic of stereotactic treatments. The findings support the use of stricter, site-specific QA action limits to fully exploit high-resolution detector capabilities and improve confidence in stereotactic PSQA.