Development of absolute dosimeter for standardization of low-energy synchrotron radiation and establishing of diagnostic X-ray beam qualities

ABSTRACT Purpose: Low energy X-rays from synchrotron radiation (SR) and X-ray generators are used for diagnostic imaging procedures. The dosimetry of low energy X-rays is challenging. For these types of radiations, the free-air ionization chamber (FAIC) is considered as the primary standard for absolute determination of air-kerma, which is an important quantity for the patient dose during diagnostic radiology investigation. Materials and Methods: To fulfil above requirement, a miniature parallel-plate FAIC (FAIC SR ) and portable parallel-plate FAIC (FAIC DIAG ) were designed and fabricated as the absolute dosimeter for standardization of SR beams and for establishing diagnostic X-rays beam qualities, RQR series respectively. Experiments were performed in SR beams (8-25 keV) as well as in diagnostic X-ray beams of 40, 50, 60, 70, 81, 90, 100 KVp for evaluating the basic characteristics of these chambers. Results: The basic characteristics of these chambers were in conformity with International Atomic Energy Agency (IAEA) TRS-374 and International Electrotechnical Commission (IEC) 61674, 60731. Dosimetric beam quality parameters such as the first half-value layer and homogeneity coefficient of the RQR series, measured using FAIC DIAG are within the acceptable limits specified by IEC 61267 and IAEA TRS-457. The RQR series (RQR 2 to RQR 8) are established as per IAEA TRS-457 specifications. Conclusions: The performance of the indegeneously developed FAICs was found satisfactory as per design and expectation and they qualify as absolute dosimeters for measurement of air-kerma of low energy regions and for direct calibration of field dosimeters and quality assurance test tools used for performance evaluation of diagnostic X-ray machines in the radiology department.