Evaluation of Multi-Modal Dosimetry for Eye Lens Dose Verification in Gamma Knife Radiosurgery: A Phantom-Based Analysis

Background: Accurate eye lens dose measurement during Gamma Knife radiosurgery (GKRS) is essential, particularly for patients with eye movement and those undergoing multiple treatment sessions, as excessive lens exposure may result in cataract formation and long-term ocular complications. Purpose: To evaluate and verify eye lens doses during GKRS using independent dosimetric techniques and to assess their agreement with treatment planning system (TPS) calculations. Methods: Eye lens doses were assessed in 12 patients treated with GKRS using three approaches: TPS calculations, optically stimulated luminescent dosimeters (OSLDs), and Gafchromic EBT3 films. OSLDs were used for their high sensitivity and reproducibility. Gafchromic EBT3 films were employed for detailed spatial dose mapping and were analyzed using both a calibrated densitometer and an EPSON 12000XL flatbed scanner with ImageJ-based optical density evaluation. Results: TPS-calculated lens doses ranged from 1.7 Gy to 37.6 Gy, depending on lesion location and proximity to ocular structures. Excellent agreement was observed among all methods, with correlation coefficients of r = 0.9994 (TPS vs OSLD), r = 0.9998 (TPS vs film densitometer), and r = 0.9999 (TPS vs film scanner). Conclusion: OSLDs and Gafchromic EBT3 films provide accurate and reliable verification of eye lens doses during GKRS. Their incorporation as secondary dose-verification tools in routine clinical practice can enhance patient safety and quality assurance.