Quality control programme in mammography: second level quality controls.

Mammography is the most reliable method by which to detect lesions in the breast. Since contrast between normal and pathological areas in the breast is extremely low, mammographic image quality should reach high standards without exceeding acceptable exposure levels for the breast. A quality control programme in mammography has been implemented. This programme is subdivided into two levels. The first consists of simple daily checks of image quality and film processing, while the second deals with more complex checks of mammographic unit, screen-film system, darkroom, illuminators, viewing conditions and reference dose determination. The values of all the parameters undergoing measurement are compared with the limiting values given by National and International Protocols. This paper describes the second level controls carried out every 6 months by the medical physicist. The parameters described are only those which have been studied and analysed in detail since the quality control programme in mammography was implemented. Such parameters (kilovoltage, focal spot dimension, half value layer, tube output, automatic exposure control system, screen-film characteristic curve and mean glandular dose) were measured during the period 1991-1995 and the results summarised. The values obtained prove the constant correct functioning of the equipment.

Daily quality control programme in mammography.

The Medical Physics Department of S. Chiara Hospital (Trento, Italy) has developed, promoted and organized a quality control programme in mammography in the Department of Diagnostic Radiology. The aim of this paper is to describe the procedure for daily quality control carried out by the radiological technologist and analysed by the medical physicist, and also to discuss some interesting results obtained in the various departments during 1994. A sensitometric strip provides the film characteristic parameters to meet the requirements of DIN 6868 Part II (base plus fog level, average gradient, relative speed, maximum density, speed index and contrast index). A test phantom radiograph provides information on the detection of microcalcifications and simulated tumours (high and low contrast resolution) as well as on the central background density and the contrast. The exposure time-current product, mAs, needed to expose the phantom is always noted. Characteristic parameters of the two systems are compared with limiting values given by International Protocols or with the permissible ranges calculated in advance. It has been possible to discover variations in the performance of mammographic and automatic processing units due to the quality control programme. In one department, for example, the malfunctioning of the automatic exposure control device was observed. In another, replacement of mammography films and the automatic processing unit resulted in a better image quality.