The shift from film to digital mammography is occurring rapidly, resulting in
diagnostic images with higher resolution and higher fees. It's also causing a greater number of
patient recalls. These facts were revealed in a recent article in the New York Times (see: In Shift to Digital, More Repeat Mammograms). On the right is a graph from the article illustrating the adoption rate of this new technology from 2004-2007.
Many patients are unaware of this shift in imaging technology but some will experience greater anxiety as a result of the increased numbers of patient recalls. The article make some very interesting and relevant points about some of the problems associated with the clinical validation of new diagnostic procedures. Below is an excerpt from the article with boldface emphasis mine:
It is a phone call that women dread. Something is not quite right on the mammogram: come back for another one. But don’t worry, the script goes, most repeat tests wind up normal....At many centers, these nerve-racking calls are on the rise, at least temporarily — the price of progress as more and more radiologists switch from traditional X-ray film to digital mammograms, in which the X-ray images are displayed on a computer monitor. Problems can arise during the transition period, while doctors learn to interpret digital mammograms and compare them to patients’ previous X-ray films. Comparing past and present to look for changes is an essential part of reading mammograms. But the digital and film versions can sometimes be hard to reconcile, and radiologists who are retraining their eyes and minds may be more likely to play it safe by requesting additional X-rays — and sometimes ultrasound exams and even biopsies — in women who turn out not to have breast cancer.
The dual concepts of radiologists "retraining their eyes and minds" and the need for clinical validation of digital mammography against previous films are important and are probably receiving insufficient attention. To put the issue boldly, this rapid shift to digital mammography constitutes a large-scale experiment with the patients as the guinea pigs. However, the fact that the number of patient recalls is rising suggests that the higher resolution of the new technology is causing false positives rather than false negatives. The problem of false positives in connection with breast MRI scans, which are even more sensitive than mammograms, is also receiving media attention (see: Breast MRI scans 'overly scare'). A Google search for the term false positive in relation to mammograms, CT scans, and MRI yields 274,000 hits.
I have posted a number of previous notes about molecular imaging. With this new technology, the goal is for radiologists to render diagnoses rather than impressions. In the conversion from film mammography to digital mammography, the latter images are being compared to the former for clinical validation. As molecular imaging matures, more sophisticated clinical validation protocols will be required based on histopathologic diagnoses of the lesions that are identified. This latter process remains as the gold standard for diagnosing tissue lesions. Such validation protocols should also include the measurement of serum biomarkers which will provide additional information and increase the diagnostic power of the molecular imaging techniques.
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