McDonnell signs bill requiring radiologists to provide more information following mammograms Gov. Bob McDonnell (R) has signed a bill requiring that radiologists provide information about breast density in post-mammogram letters to patients. The measure goes into effect July 1. Virginia Gov. Robert McDonnell (R). (J. Scott Applewhite - AP) State legislators passed the legislation after leaning mammograms miss about 40 percent of cancers in women with dense breast tissue. Other imaging techniques, such as MRIs and ultrasounds, can detect some tumors in dense tissue better than mammograms but those tests have their own shortcomings too. The bill was met with behind-the-scenes resistance from radiologists who were concerned that women would be unduly alarmed, turned off from life-saving mammograms, and left footing the bill for unnecessary and expensive tests.