Wide area surface dosimetry with conformal scintillator array for external beam radiotherapy

In vivo dosimetry is essential for treatment verification in modern radiotherapy, but existing techniques have significant limitations in their logistics of use related to time, accuracy of placement, temporal resolution, and non-uniform anatomy. Optical scintillation imaging dosimetry has shown potential to address several of these limitations, and the translation to conventional photon external beam radiotherapy was examined with a novel wide area imaging and sensing technique.

This study characterized a conformable scintillator array, for imaging real-time surface dose delivery over a wide curved surface area in conventional photon external beam radiotherapy. The variability was evaluated for dose, angular deviation, repetition rate, and field geometry while assessing its performance in field edge detection and measurement reproducibility using an anthropomorphic torso phantom.

The modular scintillator array consisting of 101 hexagonal scintillating elements was used together with a dual-camera stereovision system for 3D localization and a clinical Cherenkov imaging system for optical scintillation detection. The water equivalent thickness, dose linearity (10-800 MU), repetition rate stability (60-600 MU/min), and angular dependence of the scintillator array were characterized. Field edge detection was evaluated against radiochromic film through gamma analysis. System reproducibility was assessed through five consecutive deliveries simulating contralateral breast monitoring during whole breast treatment with a tangent beam.

The scintillator array demonstrated high dose linearity (R² = 0.999) across the full tested range, with minimal beam perturbation (1.21 mm water equivalent thickness) and consistent response within 5% across all available LINAC repetition rates. Dose-normalized scintillation varied within 5% for clinically relevant gantry angles (0°-75°), while camera angle corrections successfully compensated for deviation from Lambertian emission. Field edge detection showed high agreement with a 99.98% gamma pass rate (3%/3 mm) compared to film. Inter-delivery reproducibility of ± 1 cGy demonstrated robust system performance across multiple acquisitions.

The conformable scintillator array imaging system provides spatially resolved, dynamic surface dosimetry with minimal workflow impact. Its ability to generate continuous dose maps across complex anatomical surfaces while maintaining angular correction capabilities addresses key limitations of current in vivo dosimetry approaches. This technology shows promise for clinical integration, particularly for treatments where wide area surface dosimetry is necessary.