Dosimetric validation of the Gamma Knife^® Icon^TM plan adaptation and high-definition motion management system with a motorized anthropomorphic head phantom

Purpose: To perform dosimetric validation of the plan adaptation and high-definition motion management (HDMM) system of Gamma Knife® Icon^TM in various clinical scenarios. Methods and materials: We built an assembly for a pitch-adjustable anthropomorphic head phantom. We then used films to measure dosimetric and positional accuracy in 13 clinical scenarios, including movement near HDMM thresholds, multiple plan adaptations, frequent coughing, and initial setup error. Results: The dose for the superiorly located 4-mm shot was decreased up to 7-13% near 2- to 3-mm HDMM thresholds in the chin-down position. Dosimetric deviation was within ±3.5% for initial pitch angles of up to 20°. Multiple treatment interruption and frequent coughing did not cause substantial dosimetric deviation (<2%). Conclusion: Our results indicated that dosimetric accuracy of the Gamma Knife® Icon^TM system is reliable even in extreme treatment conditions. However, the user should exercise caution for superiorly located small lesions with an HDMM threshold ≥2 mm or in the scenario of large initial setup error.