2251 - Conformal Scintillator Array Imaging Allows for Dynamic 2D In Vivo Dosimetry of Wide-Area and High-Gradient Fields

Purpose/Objective(s):

In vivo dosimetry (IVD) is essential for treatment verification, but achieving precise measurements remains challenging. Conventional techniques are often insufficient, especially when measuring dose over time, wide areas of non-uniform anatomy, or steep dose gradients. Current approaches are often limited by temporal resolution, 1D measurement, or variable angular response, which can lead to inaccurate target coverage and dose dynamics. In this work, we introduce the first wide-area conformal scintillation imaging system capable of time-resolved in vivo surface dosimetry with minimal impact on clinical workflow and evaluate performance in a clinical trial against TLD dosimetry.

Materials/Methods:

A deformable scintillator array was constructed from 100 hexagonal elements with a 7.5 mm pitch and 10×5 cm² area. Conformality was evaluated by adhering the array to phantoms of decreasing diameter. During irradiation, an intensified CMOS camera captured emission from each element, interpolating between them to obtain a continuous dose map over the full area. Stereovision imaging localized the array in 3D, allowing for dynamic angular correction. Scintillation linearity with dose was verified at 6MV and 10MV, and impact on beam delivery was characterized by water equivalent thickness. This technique was translated in vivo and used to monitor dose for 3 patients undergoing tangent/supraclavicular (SCV) treatments, specifically in high gradient regions at the contralateral breast, and tangent/SCV fields match lines. Each array measurement was compared to a reference TLD at the array center and two TLDs positioned 5 mm from the top and bottom edges.

Results:

The array retained 100% conformality over surfaces of diameter >1.3cm and attachment was comparable to bolus placement. Scintillator intensity was linear with dose for 6MV (R²>0.99) and 10MV beams (R²>0.99). Stereovision positioning localized the 3D target surface in patient coordinates with 0.5mm accuracy. The system resolved continuous dose gradients up to 150cGy/cm at the field edge and captured real-time in vivo surface dose distributions during treatment revealing contralateral breast dose ranging from 230 cGy to 40 cGy. Across all deliveries, central TLDs agreed within 1% (1.5 cGy) of the interpolated dose map. Edge TLD deviations were higher due to extrapolation but still agreed within 20 cGy and 2 mm.

Conclusion:

This work introduces a wide-area conformal scintillation imaging system capable of real-time, in vivo surface dosimetry with minimal workflow impact. The system’s ability to resolve steep dose gradients and continuous dose maps across complex anatomy demonstrates its potential to enhance treatment verification and address key limitations of current IVD. Ongoing work will further integrate into the clinical trial, applying the dosimetry to additional patient treatments and sites.