Analysis of the Evolution of Acceptance Indices of Quality Control Parameters for X-Ray Equipment in the State of São Paulo

Abstract

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 to prevent the exposure of health professionals and patients to unnecessary doses of ionizing radiation. This paper presents a historical analysis of 1,635 Quality Assurance Technical Reports by Health Institutions in the state of São Paulo, Brazil, over a 7-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 HVL – Half-Value Layer, which is important not only for image quality but also for radiation protection, showed significant improvements. Again, 48% of portable X-ray equipment showed HVL values below the recommended for 80kVp (2.3mmAl), a percentage that declined to 24% in 2006. With regard to mammographers, which are newer machines, all the analyzed systems presented acceptable HVL values. Conventional X-ray machines showed a decrease of this index (nonconformity) from 11% in 2000 to 6% 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, therefore reducing the patient’s exposure to radiation.