Isodose Curve Mappings Measured While Undergoing Rotation for Quality Assurance Testing of a 137Cs Irradiator

摘要

To enable accurate and reproducible dosimetry for biological sample irradiation in a ¹³⁷Cs irradiator, routine quality assurance (QA) of the dose rate and isodose distributions should be considered. Our previous work demonstrated a means for accurate dose rate QA and for QA of isodose distributions of non-rotational samples. In this work we present a means to accurately and cost effectively measure dose distributions within a ¹³⁷Cs irradiator using rotational geometry, which geometry represent a more typical use of these irradiators. A simple apparatus was developed to hold radiochromic film (RCF) and was constructed of polymethyl methacrylate (PMMA). The rotational QA device allowed the comparison of measured RCF versus manufacturer provided isodose distributions. A good agreement was discovered between the two data sets along the central vertical axis of rotation in the ¹³⁷Cs irradiator, but a 40–50% smaller 100% isodose region in the horizontal direction. These finding may lead to limiting the overall size of a sample capable of being uniformly irradiated by the ¹³⁷Cs irradiator at our research institution. We propose the construction and use of a simple rotational QA device for routine QA of ¹³⁷Cs irradiators.