Evolution of X-ray machine quality control acceptance indices

The quality assurance (QA) of radiographic images based on the operating conditions of X-ray equipment is essential for good image quality, accurate medical diagnostics and for the prevention of health professionals and patients to unnecessary doses of ionizing radiation. This paper presents a historical analysis of 1,635 Quality Assurance Technical Reports of Health Institutions in the state of São Paulo, Brazil, over a seven-year period. Based on acceptable limits for variations between nominal and measured parameters as the variable to determine the quality of X-ray equipment operating conditions, a significant improvement was found in the percentage of acceptance of the overall parameters described in the QA technical reports over this period. As expected, we found a strong concentration in the categories of conventional and portable X-ray equipment, which represent 72% and 84%, respectively, of the total number of equipments. A mechanical parameter such as half-value layer (HVL), which is important not only for image quality but also for radiation protection, showed significant improvements. Again, only 58% of portable X-ray equipment showed HVL values recommended for 80 kVp (above 2.3 mm Al), a percentage that improved to 76 % in 2006. With regard to mammographers, which are newer machines, all the analyzed systems presented acceptable HVL values. Conventional X-ray machines showed an increase of this conformity index from 89 % in 2000 to 94 % in 2006. All this improvement was attributed to the continuous and extensive enforcement of Regulation Act 453 in the state of São Paulo. The improvement in equipment quality control standards is expected to result in the improvement of diagnostic quality, as well as in the reduction of exam repetitions, and thereby reducing the patient’s exposure to radiation. PACS number: 87.57.C Key words: X-ray equipment, quality assurance, dose linearity, applied kilovoltage