[Quality control testing of x-ray equipment used in medical diagnostic: results of interlaboratory comparison]

Effective diagnostic radiology system should be based on an efficient and suitable servicing of medical X-ray equipment. According to Polish requirements, all radiology departments are obligated to carry out quality control (QC) test of their X-ray set. In practice, testing is mostly performed by accredited external QC services, which have to participate in periodic interlaboratory comparison (ILC) to maintain or obtain the accreditation. Large-scale ILC for QC services were performed at the Nofer Institute of Occupational Medicine for three ranges of diagnostic radiology: dental, conventional and mammography.

During ILC, the metrological coherence of main physical parameters, which determine good quality of diagnostic image, were estimated and compared with appropriate reference values ensured by ILC organizer. The ILC participants comprised 29 QC services. The measurements were performed by ILC participants under laboratory conditions, using their own calibrated meters, according to routine procedures. All measurement results were assessed by calculating the E(n) value, normalized with respect to the uncertainties.

Of the 328 evaluated results only 11 (3.4%) were classified as unsatisfactory. As much as 82% of them applied to mammography. Thus, the final evaluation revealed negative results in 2 of the 29 participants, which means that their satisfactory scores for the studied ranges were below 75%.

In spite of predominant amount of satisfactory results, ILC indicated some regions of divergence e.g. large differences in evaluation of uncertainties and other inconsistencies.