Dose Optimization for the Quality Control Tests of X-Ray Equipment

Abstract

Radiation is a major risk in diagnostic and therapeutic medical imaging. The problem is caused from incorrect use of radiography equipment and from radiation exposure to patients much more than required. Exposure of different dose values for same clinical examination, is an enough reason to draw attention to this issue. International Commission on Radiation Protection (ICRP), International Atomic Energy Agency (IAEA) and other various independent institutions have been making publications in relation to ionizing radiation protection for more than fifty years. Report 60 of ICRP and Basic Safety Standards that was published in IAEA report have three basic principles related to radiation protection (ICRP, 1991; IAEA, 1996). The most important issue in these principles is optimization of radiation. In mentioned policy, lowest dose is aimed by considering country's economic and social factors for acceptable applications. Personnel already receive low dose with protection systems in working areas. However, patient doses must be taken under control based on principle of optimization as much as possible. There are two important points when performing a radiological procedure:  To obtain best possible image for a clear diagnosis of disease,  To apply lowest dose for protecting patient while getting best image. The second point indicates that patient’s radiation dose level must be kept at lowest possible dose. In other words, it indicates dose optimization. The dose optimization meaning the minimum radiation dose of optimum image quality, is achieved by applying quality control procedures, calibration and dosimetric measurements. In Radiology Quality Control systems, biggest problem is dose control and dose optimization. Neither patient nor users knows how much dose is exposed because there is no any system in x-ray device for measuring or showing dose during exposure. Since there is no dose adjustment on equipment, systems are operated by using usual parameters; kVp and mAs. Because dose can not be adjusted, patient may receive more dose than aimed dose. For dose optimization, all exposures should be kept at minimum dose level in according to ALARA principle (ALARA-as low as reasonably achievable). The aim of optimization is not to download risks of irradiation to zero. It is to reduce them to an acceptable level. This can be possible only by examining all parameters that affect X-ray, by investigating relationship between dose and these parameters, on basis of this relationship, by performing necessary regulations.