270 - Scintillator Array In Vivo 3D Surface Dosimetry: Development and Clinical Translation for Photon, Proton and FLASH Radiotherapy

01:10pm - 01:20pm ET

Room 258

Presenter(s)

Roman Vasyltsiv, PhD, BS - University of Pennsylvania, Philadelphia, PA

R. Vasyltsiv¹, A. L. Matous², J. Harms³, N. Mulenga¹, M. Rohman⁴, H. Qi⁴, C. B. Simone II⁴, H. Lin⁵, B. W. Pogue⁶, D. J. Gladstone⁷, L. A. Jarvis⁸, and P. Bruza⁹; ¹Dartmouth College, Hanover, NH, ²Dartmouth-Hitchcock Medical Center, Lebanon, NH, ³WashU Medicine, Department of Radiation Oncology, St. Louis, MO, ⁴New York Proton Center, New York, NY, ⁵Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, ⁶Thayer School of Engineering at Dartmouth College, Hanover, NH, ⁷Geisel School of Medicine at Dartmouth & Norris Cotton Cancer Center, Dartmouth Hitchcock Medical Center, Lebanon, NH, ⁸Dartmouth Health, Lebanon, NH, ⁹Thayer School of Engineering, Dartmouth College, Hanover, NH

Purpose/Objective(s):

Clinical in vivo dosimetry (IVD) faces growing challenges from complex beam delivery, steep dose gradients, and non-uniform anatomy, while the rapid pursuit of FLASH therapy demands more capable treatment verification. Existing IVD solutions remain limited by point-only measurement, dose rate dependence, or delayed readout. This work presents and clinically translates a deformable, wide-area scintillator array imaging system for photon, spread out Bragg peak (SOBP) proton, and FLASH proton therapy, enabling time-resolved 3D surface dosimetry with patient-geometry mapping and a path toward volumetric dose verification.

Materials/Methods:

A wide-area dosimetry system combining a conformal pixelated scintillator array (15×15 cm²; 750 elements; 0.9 mm water equivalence) with a high-speed optical camera and stereovision tracking was developed, enabling >4500 FPS scintillation imaging (~0.2ms dose sampling) with simultaneous 3D surface registration for patient-coordinate mapping. Scintillator dose and dose rate response linearity were verified for photon and proton beams. Clinical translation was performed through a 12-patient contralateral breast photon IVD study, comparing scintillation-derived 3D surface dose maps against point TLD dosimetry to evaluate dosimetric accuracy and impact of placement uncertainty. For protons, the array was applied to CT-planned anthropomorphic phantoms, and irradiated under conventional and FLASH conditions. Resulting time-resolved surface dose was registered to CT and propagated volumetrically using an analytical depth projection model for comparison against planned volume dose.

Results:

The array demonstrated linear dose response for both photon and proton beams, and showed dose rate independence across conventional and UHDR ranges. In the clinical photon study, the system resolved dose gradients up to 150 cGy/cm at field edges and captured real-time contralateral breast doses ranging from 40 to 230 cGy. Across 12 patient cases, central TLD dose agreed within 1% (1.5 cGy) of the scintillation dose map, while physician-selected point dosimetry locations differed by 2.74 ± 0.95 cm from the dose maxima, highlighting point dosimetry drawback. In proton workflows, scintillation-derived FLASH surface dose and dose rate maps agreed with film at >99% gamma passing (2%/2 mm) with <0.5 mm spot localization error. For conventional SOBP delivery, surface dose was dynamically resolved at each energy, and analytical projection of each spot yielded a time resolved volumetrically reconstructed dose distribution that agreed with the treatment plan within 5%.

Conclusion:

This deformable scintillator array integrates wide-area coverage, minimal water equivalence, time-resolved readout, and geometric mapping into a unified dosimetry platform for photons, conventional protons, and FLASH protons. Clinical and phantom workflows demonstrate its utility across treatment modalities, supporting near-term clinical translation.