Method and apparatus for using film density measurements of a radiograph to monitor the reproducibility of X-ray exposure parameters of a mammography unit

摘要

Apparatus and methods for using film density measurements of a radiograph to monitor the reproducibility of x-ray exposure parameters used by a mammography unit to make the radiograph are disclosed. Radiographic images of a breast phantom and a novel mammography beam quality phantom are formed simultaneously on a film using a single x-ray exposure. The mammography beam quality phantom comprises at least a first section and a second section formed from materials having different x-ray attenuation properties and thicknesses. For any combination of x-ray exposure parameters useful for film mammography, including the parameters of kilovoltage peak, dose, and half value layer, the material from which the first section is formed is selected so that the optical density produced by the first section of the mammography beam quality phantom is greater than the optical density produced by the breast phantom. The material from which the second section is formed is selected so that the optical density produced by the second section of the mammography beam quality phantom is less than the optical density produced by the breast phantom. The difference in optical density between the first and second sections of the mammography beam quality phantom, adjusted for the effect of film processing, is calibrated in terms of exposure parameters. Thus, the film density measurements of a radiographic image of a mammography beam quality phantom can be used to monitor the reproducibility of x-ray exposure parameters of a mammography unit in making repeat radiographs of a breast phantom.