Clinical Scintillation Array Imaging Enables in vivo contralateral Breast 3D Surface Dosimetry
Abstract
Purpose
Limiting contralateral breast dose (CBD) is an important concern in breast radiotherapy, as prior studies link doses >1Gy to significantly increased secondary cancer risk. Furthermore, complex beam geometry increases low-dose irradiation of healthy tissue while dose verification via point dosimetry is placement-dependent and unreliable in steep dose gradients, impeding accurate measurement. This work introduces a novel scintillator array dosimeter providing isocenter-referenced 3D surface dose maps, and evaluates its translation in a clinical study benchmarked against TLD measurements.
Methods
Cherenkov imaging was used to identify 10 treatments (7 tangent/supraclavicular, 3 VMAT) with CBD. Following the first fraction, a 10×5cm² deformable array of 100 scintillating elements was placed medially along the breast. The central element was replaced by a TLD at the physician-identified point of interest, with a second TLD placed 5mm from the array medial edge. During irradiation, an intensified-CMOS camera captured emission from each element, interpolating to obtain continuous dose maps, while stereovision localized the 3D array surface. For each patient, a dose map cross-section was compared against TLD readings, and distance between central TLD placement and array-reported maximum dose was calculated.
Results
Scintillator array dosimetry resolved continuous dose maps with 150cGy/cm gradients at field edges, identifying CBD ranging from 40-230cGy. Central TLDs agreed within 5cGy/1mm of interpolated maps across all deliveries. Edge TLDs showed greater deviation due to extrapolation but agreed within 20cGy/2mm. Central TLD placement showed average separation of 2.74(+/-0.95)cm from maximum CBD, with VMAT showing increased deviation compared to tangent delivery. Scintillator intensity was linear with dose (R²>0.99), and array water equivalent thickness remained <1mm.
Conclusion
This work demonstrates clinical translation of 3D surface scintillation dosimetry with direct application in conformal CBD monitoring. The system resolves continuous dose maps across steep dose gradients and non-uniform anatomy, enhancing treatment verification and addressing key limitations of current dosimetry.