Physical aspects of establishing tolerances and limiting values in diagnostic radiology

This paper deals with the background to the measurement process and in particular what is meant by accuracy and precision in diagnostic radiology. The relevance of these two quantities to both the tolerances imposed on the measurement process and the limiting value of the measured quantity is highlighted. The framework for quality control in diagnostic radiology is described together with the need to match the tolerances of the measurement process to the regime employed in tests associated with specifying performance in the factory, in the X-ray department upon installation, or monitoring performance during routine operation. Error analysis is used to determine overall effects on the final outcome of the limiting values associated with individual parameters. The multi-parameter expressions used in this analysis also have an important role to play in optimization analyses of the radiological process. (author)