Technical Note: A method for improving the calibration reproducibility of an ionization chamber detector array. Issue 9 (13th August 2014)

• Record Type: Journal Article
• Authors: Goodall, Simon; Morgan, Steve
• Is Part Of: Medical physics. Volume 41:Issue 9(2014)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2014-08-13
• Subjects: Dose‐volume analysis -- Standards and calibration -- Gas‐filled counters: ionization chambers, proportional, and avalanche counters; calibration -- dosimeters -- dosimetry -- ionisation chambers -- radiation therapy; calibration reproducibility -- array calibration -- radiation dosimetry; Radiation therapy -- Testing or calibrating of apparatus or arrangements provided for in groups G01D1/00 to G01D15/00 -- Measurement of nuclear or x‐radiation -- Dosimeters -- Calibrating of instruments or apparatus -- Tubes for determining the presence, intensity, density or energy of radiation or particles -- Scintigraphy -- with scintillation detectors -- Ionisation chambers; Calibration -- Inductively coupled plasma -- Linear accelerators -- Detector arrays -- Ionization chambers -- Dosimetry -- Quality assurance; Medical physics -- Periodicals; Medical physics; Geneeskunde; Natuurkunde; Toepassingen; Biophysics; Periodicals; Periodicals; Electronic journals; 610.153
• DOI: 10.1118/1.4892607
• Languages: English
• ISSNs: 0094-2405

Abstract

Abstract : Purpose: : This paper describes an extension to a wide field calibration method implemented on a commercial detector array in order to improve the reproducibility of the calibration procedure. Methods: : Following the standard array calibration procedure, two additional 10 × 10 cm exposures were acquired for each array axis with the detector array shifted by ±10 cm in the transverse or axial axes, or by ±10 2 cm in the positive or negative diagonal axes. These exposures were compared with a final baseline 10 × 10 cm exposure captured with the detector repositioned at the isocenter. The measurements were used to calculate a linear off‐axis correction gradient which was then applied to the stored calibration factors. Results: : The mean coefficient of variation between five repeat calibrations was reduced from 4.17% to 0.48% and the maximum percentage error in individual calibration factors was reduced from 6.46% to 0.77%. Conclusions: : The reproducibility of the calibration factors of an ionization chamber array was increased by capturing a baseline exposure and two further off‐axis readings per calibration axis.