Feasibility of Acquiring Radiotherapy Linac Commissioning Data with a Three-Dimensional Cubic Electronic Detector Array

Abstract

Linac commissioning data acquisition consists of measurements of PDDs/TMRs, profiles, and dosimetric factors done in water and lasting several weeks to complete. Data collected with an early prototype 3D cubic electronic detector suggests faster, reliable, accurate, and a cost-effective option for commissioning data collection in the future. A 10 × 10 × 15 cm3 3D cubic electronic detector array prototype of acrylic, silicon rubber, and five 10 × 10 × 0.2 cm3 planar active matrices at 2.0, 4.0, 6.0, 8.0, and 10 cm depths, was constructed. Each active matrix has 25 pixels (diode, capacitor, MOSFET) of 2.0 cm separation in a 10 × 10 cm2 active area resulting in 125 pixels in the array. Data readout consists of a multiplex connectivity configuration where one channel provides data input/output to multiple pixels rather than one channel per pixel. Simultaneous absolute depth-dose (ADD) and profile measurements were performed using a 6 MV photon beam, 100 cm SSD, 10 × 10 cm2 open field, 100 MU, and 400 MU/min, without scanning. Also, ADDs and profiles were measured with 15-, 30- and 45-deg wedges. Data processing for these measurements, and 2D and 3D DD and profile displays, were done in a programming environment, and results were compared to calculated data in acrylic. Table with ADD and profile results for the 10 × 10 cm2 open field. ADD and profiles with wedges showed similar results. Absolute depth-dose and profile data acquired with an early prototype agreed within ±4 % of calculated values. This suggests that an improved 3D cubic electronic detector array could be used for commissioning data collection. If realized, it could reduce commissioning time from weeks to hours saving cost, staff time, and leveraging a new Linac into clinical operations sooner.