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A Three-Dimensional Electronic Detector Array for Dose Verification in Radiotherapy: Proof of Product

D Roa1, R Challco2*, Z Arqque3, O Paucar4, C GUZMAN CALCINA5, A Gonzales6, A Gonzales Galvez7, M Montoya8, J Hernandez-Bello9, (1) University Of California, Irvine, Orange, CA, (2) Universidad Nacional de Ingenieria, Lima, ,PE, (3) Universidad San Antonio Abad, Cuzco, ,PE, (4) Universidad Nacional de Ingenieria, Lima, ,PE, (5) Universidad Nacional Federico Villarreal, Lima, ,PE, (6) Universidad Nacional de Ingenieria, Lima, ,PE, (7) Aliada Contra El Cancer, Lima, ,PE, (8) Universidad Nacional de Ingenieria, Lima, ,PE, (9) HRS Oncology International, Las Vegas, NV


(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: Proof of product (POP) of a three-dimensional (3D) electronic detector array that can provide volumetric prescription dose quality assurance (QA) of an IMRT/VMAT plan within minutes after irradiation.

Methods: A 3D electronic detector array has been constructed. It consists of three concentric PMMA semi-spherical layers, 210 photodiodes in a semi-isotropic distribution and a farmer chamber in its central volume. The innermost layer has a 2 cm radius, 5 active matrices (AMs) and 3 AM pixels per matrix. Each AM pixel comprises a BPW34S photodiode, a 1 µF storage capacitor and a NX7002AK MOSFET. The central and outermost layers have radiuses of 4 cm and 6 cm, 5 active matrices (AMs) each and 12 and 27 AM pixels per matrix, respectively. A dose calibration that matched the TPS calculated dose to the voltage measured by each photodiode in a 20 x 20 cm^2 6 MV parallel-opposed SAD beams to a specific dose at isocenter, was applied to a QA measurement. Furthermore, the detector array design was converted to DICOM and exported to a TPS to be used for plan verification of a 3D conformal intracranial target treatment.

Results: Spherical coordinates were used to map the dose distribution from the calculated (TPS) and measured sources. A direct dose analysis for each diode was performed and a percent dose difference of = 4% was observed. Gamma value analysis is in progress and results are pending.

Conclusion: These preliminary results demonstrate the feasibility and mark the beginning of the development of 3D electronic detector array for IMRT/VMAT QA. The need for such a device is compelling due to advances in linac technology that have made high precision treatments routine.

Funding Support, Disclosures, and Conflict of Interest: Financial support for this project was provided by HRS Oncology International and the Universidad Nacional de Ingenieria in Lima, Peru.


3D, Absolute Dosimetry, Quality Assurance


TH- Radiation Dose Measurement Devices: Development (new technology and techniques)

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