Use of a commercial ion chamber detector array for the measurement of high spatial-resolution photon beam profiles.

Use of a commercial ion chamber detector array for the measurement of high spatial-resolution photon beam profiles.
J Appl Clin Med Phys. 2018 Oct 04;:
Authors: Karimnia V, Belley MD, Rodgers R, Price M
Abstract
Linear accelerator (linac) commissioning and quality assurance measurements are time-consuming tasks that often require a water tank scanning system to acquire profile scans for full characterization of dosimetric beam properties. To increase efficiency, a method is demonstrated to acquire variable resolution, photon beam profile data using a commercially available ion chamber array (0.5 cm detector spacing). Field sizes of 2 × 2, 5 × 5, 10 × 10, and 15 × 15 cm2 were acquired at depths in solid water of dmax , 5 cm, and 10 cm; additionally, beam profiles for field sizes of 25 × 25 and 40 × 40 cm2 were acquired at 5 cm depth in solid water at x-ray energies of 6 and 23 MV. 1D composite profiles were generated by combining discrete point measurements made at multiple couch positions. The 1D composite profile dataset was evaluated against a commissioning dataset acquired with a 3D water tank scan system utilizing (a) 0.125 cc ion chamber for 5 × 5, 10 × 10, 15 × 15, 25 × 25, and 40 × 40 field sizes and (b) a solid state detector for 2 × 2 cm2 field size. The two datasets were compared to the gamma criteria at 1%/1 mm and 2%/2 mm tolerance. Almost all pass rates exceeded 95% at 2%/2Â...

Source: Journal of Applied Clinical Medical Physics - October 4, 2018 Category: Physics Authors: Karimnia V, Belley MD, Rodgers R, Price M Tags: J Appl Clin Med Phys Source Type: research