Computed radiography systems for mammography: an evaluation of image quality and dose

Computed radiography (CR) in mammography was initially based on systems for general radiography. Dedicated mammography CR systems are now available with improved imaging capability, particularly in terms of spatial resolution. The phosphor is carried on a clear backing plate and the reader scans both sides of the phosphor simultaneously.

Image quality data for both types of mammography CR system was obtained using standard test objects. All acquired images were printed onto film using a high-resolution laser printer and were scored under standard viewing conditions. Certain images were also scored as soft copy using a reporting workstation. Breast dose was also assessed. The results were compared to film screen data and to the National Health Service Breast Cancer Screening Programme (NHSBSP) guidelines on the introduction of CR systems for mammography.

In terms of low contrast sensitivity and small detail detectability the performance of both designs of CR system is similar to that of a modern film screen combination. The measured values of high contrast resolution are close to the nominal values derived from the pixel size but are significantly poorer than for film screen imaging. Dose levels are similar to that for a modern film screen combination. Both CR systems meet the suggested NHSBSP standards for image quality and dose.