A comprehensive characterization of a multi-axis ion chamber array for use as a linear accelerator QC device

To investigate the behavior of a high-resolution multi-axis ion chamber array in measuring key parameters within a linear accelerator quality control (QC) program. The detector consists of a double-layer ionization chamber matrix detection plate and it can acquire relative dose profile in inline and crossline direction. It was tested for reproducibility, dose rate dependence, linearity, and angular/field dependence. Its ability to measure flatness, symmetry, and dose profiles for photon (6/10 MV, FF/FFF) and electron (6/9 MeV) beams was compared against water phantom measurements. The ability to detect multileaf collimator (MLC) positioning errors was also analyzed. Short and long-term reproducibility were within 0.3 %, dose rate dependence was under 0.2 %, and the dose response was linear. The angular dependence was below 1 % for gantry angles between 0° and ±30°. Profile comparisons showed a maximum difference of 1.5 % over beam flat area. Average deviations were minimal for flatness (<0.2 %), symmetry (<0.4 %), and penumbra (<0.7 mm). Depth dose differences did not exceed 1 %. The system can detect MLC positioning error lower than 1 mm. The high resolution multi-axis ion chamber array is a reliable tool for verifying beam parameters in a QC program, demonstrating high accuracy in profile evaluation.