Author: Uddin, T.U.
Paper Title Page
WEPPD061 Quality Control of Modern Linear Accelerator: Dose Stability Long and Short-term 2660
 
  • T.U. Uddin
    NICRH, Dhaka, Bangladesh
 
  Quality Control (QC) data of modern linear accelerators, collected by National Institute of Cancer Research and Hospital, Dhaka, Bangladesh between the years 2006 and 2010, were analyzed. The goal was to provide information for the evaluation and elaboration of QC of accelerator outputs and to propose a method for QC data analysis. Short- and long-term drifts in outputs were quantified by fitting empirical mathematical models to the QA measurements. Normally, long-term drifts were well (≤1.5%) modeled by either a straight line or a single-exponential function. A drift of 2% occurred in 18 ± 12 months. The shortest drift times of only 2–3 months were observed for some new accelerators just after the commissioning but they stabilized during the first 2–3 years. The short-term reproducibility and the long-term stability of local constancy checks, carried out with a sealed plane parallel ion chamber, were also estimated by fitting empirical models to the QC measurements. The reproducibility was 0.3–0.6% depending on the positioning practice of a device. Long-term instabilities of about 0.3%/month were observed for some checking devices.