Digital Mammography - Where to now?
Digital mammography represents a potential new and exciting development in the interface between computers and health care. Your paper highlights some of the emerging issues which might be expected with new technology. You have noted the increase in incidence of breast cancer, together with a large increase in recall rates. Reports from the radiologists also indicate that between 6% and 10% of tumors are identified clinically following mammography.
The protocol presented by those involved in the screening program differs in a number of significant aspects from conventional screen film mammography. The instructions provided to women attending for screening do not include any advice regarding using talcum powder. This advice had always previously been given both in writing and orally to those attending for mammograms.
All X-rays are reported and scored by two specialist radiologists. However, the reports, when issued, do not identify the radiologists, nor is the panel from which they are selected apparent. The Quality Assurance manual indicates that targets are set for the incidence of breast cancer. A Standarised Detection Ratio (S.D.R.)is the preferred method for correcting unit performance. This raises the possibility that the computer can over-ride the results from the individual radiologists. Such a mechanism might again contribute to an increase in detection of breast cancer.
The new digital equipment relies much less on X-ray exposure and has substituted pressure to compensate for the reduction in the X-ray content. Is it possible that the increase in pressure on breast tissue might contribute to the increase in incidence of second round breast cancers from 4.4 to 5.7/1,000 when the older SFM machine is compared to the newer FFDM machine, reported by Hambly et al in the American Journal of Radiology, October 2009.
Is the observed interval tumor rate a result of the reduced penetration in the new machine, with consequent diminution in accuracy of detecting mass lesions? Alternatively, is the increased pressure in the new machine causally related to the number of women who present with mass lesions following mammography?
Conflict of Interest: