2441 - Development and Clinical Evaluation of a Portable Pixelated Radio-Luminescent Organic Phantom for Radiotherapy Quality Assurance

S. Wang¹, C. T. Gibson², M. R. M. Ashraf³, M. Gopaulchan⁴, L. Wang⁵, L. Skinner⁶, and L. Xing⁴; ¹Stanford University, Palo Alto, CA, ²Stanford Health Care, Palo Alto, CA, ³Stanford Radiation Oncology, Palo Alto, CA, ⁴Department of Radiation Oncology, Stanford University, Stanford, CA, ⁵Department of Radiation Oncology, Stanford University School of Medicine, Palo Alto, CA, ⁶Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA

Purpose/Objective(s): This study introduces a portable, pixelated radio-luminescent organic phantom designed specifically for dosimetry and quality assurance (QA) purposes, addressing the need for precise dose measurements. The developed pixelated design is intended to improve reading accuracy, particularly in low dose areas, by mitigating crosstalk—surpassing the limitations of traditional sheet-based radio-luminescent phantoms. Materials/

Methods: Utilizing 3D printing technology, the phantoms housing and the integrated camera system were constructed. This setup incorporated 300 scintillator pixels, each measuring 2mm x 4mm x 4mm. The camera output underwent calibration against film measurements over a dose range from 5 MU to 500 MU, in full field and in five incremental steps. This process yielded a fitted curve that was instrumental in developing a dose measurement look-up table (LUT) with 0.1 MU increments for each pixel. Dose ground truth predictions were subsequently made by approximating the pixel intensity to the nearest value in the LUT, enhancing the accuracy of measurements.
Results: Analysis comparing the dosimeter camera readings with film data revealed a linear relationship across four randomly selected pixel points, attesting to the devices reliability in accurate dose measurement. Specifically, the Pearson correlation coefficients for pixel locations (10,20; 203,225; 50,60; 48,411) were exceptionally high (0.99998, 1, 0.99999, and 0.99999), indicating near-perfect linearity and a strong correlation between the measured and ground truth doses. This numerical assessment complements the visual agreement observed in the 2D dose distribution comparisons, where the portable dosimeters output closely matched that of film measurements in smaller radiation fields. The slopes derived from both measurement approaches showed a close match, further validating the accuracy of the developed phantom in replicating precise dose distributions across a varied range of dosimetry applications.
Conclusion: The development of this portable, pixelated, radio-luminescent organic phantom marks a significant enhancement in dosimetry and QA technology. By integrating a sophisticated dose measurement LUT and minimizing crosstalk through its pixelated architecture, this phantom achieves unparalleled accuracy in dose readings, especially in low dose zones. This advancement sets a new standard in radioluminescence-based dosimetry solutions, promising to refine QA protocols in clinical settings.