Use of digital mammography in needle localization procedures

With digital technology, images can be displayed rapidly and manipulated. This study was undertaken to assess the duration and accuracy of needle localizations performed with digital vs film-screen technology. These two technologies also were compared with respect to radiation doses and ability to image a standard phantom.

A prototype digital mammographic system with both a 512 x 512 matrix and a 1024 x 1024 matrix was evaluated by using the American College of Radiology mammography accreditation phantom, and these results were compared with testing done on commercially available, dedicated, analog mammography equipment. Duration, accuracy of needle placement, and number of exposures needed to perform localization were recorded for 157 consecutive needle localizations done with digital technology, and these results were compared with data collected from 103 needle localizations done with film-screen technology. Another 33 localizations attempted with digital imaging were aborted because of technical factors. Average glandular doses were calculated for those women who had a compressed breast thickness of 4-5 cm.

The time to complete needle localization was reduced by almost 50%, from 20 to 11 min, when digital technology was used. Because of the small (5 x 5 cm) field of view of the digital system, an additional mammogram obtained at the onset of the procedure was found to be helpful in localization, but otherwise the number of images was the same regardless of imaging receptor. Mean glandular dose was reduced by about 50% with digital imaging from 0.219 to 0.120 cGy. In those 17% (33/190) of needle localizations that could not be completed with digital imaging, failure was due to a variety of factors. Despite improved detectability of fibrils, specks, and masses on digital images, digital systems did not show some fine calcifications or soft-tissue masses during needle localizations. Difficulty in imaging lesions near the chest wall or in the axilla and the small field of view also caused procedures attempted with digital imaging to be aborted and completed with film-screen systems.

The time to complete needle localization was reduced by 50%, with a similar reduction in patients' radiation dose, when digital mammography was used. These findings should be applicable to stereotaxic procedures done with digital mammography. Factors limiting the use of digital mammography equipment included inability to image some fine calcifications and some masses, difficulty in imaging near the chest wall and in the axilla, and a small field of view.