[Physical and technical aspects of digital mammography]

Image quality of digital direct flat-panel mammography versus an indirect small-field CCD technique using a high-contrast phantom

OBJECTIVE

To compare the detection of microcalcifications on mammograms of an anthropomorphic breast phantom acquired by a direct digital flat-panel detector mammography system (FPM) versus a stereotactic breast biopsy system utilizing CCD (charge-coupled device) technology with either a 1024 or 512 acquisition matrix (1024 CCD and 512 CCD).

MATERIALS AND METHODS

Randomly distributed silica beads (diameter 100-1400 μm) and anthropomorphic scatter bodies were applied to 48 transparent films. The test specimens were radiographed on a direct digital FPM and by the indirect 1024 CCD and 512 CCD techniques. Four radiologists rated the monitor-displayed images independently of each other in random order.

RESULTS

The rate of correct positive readings for the "number of detectable microcalcifications" for silica beads of 100-199 μm in diameter was 54.2%, 50.0% and 45.8% by FPM, 1024 CCD and 512 CCD, respectively. The inter-rater variability was most pronounced for silica beads of 100-199 μm in diameter. The greatest agreement with the gold standard was observed for beads >400 μm in diameter across all methods.

CONCLUSION

Stereotactic spot images taken by 1024 matrix CCD technique are diagnostically equivalent to direct digital flat-panel mammograms for visualizing simulated microcalcifications >400 μm in diameter.

[Current situation and future perspectives of digital mammography]

Digital mammography has extensively replaced conventional film screen mammography and is now the standard in combination with soft copy reading in clinical as well as screening mammography. Large international multicenter studies demonstrate an equivalent or superior detection rate of breast cancers by digital in comparison to conventional mammography especially in dense breasts, premenopausal and perimenopausal women and women less than 50 years old. Computer-aided detection (CAD) is important for the experienced investigator (increased specificity). Digital mammography also offers further options, such as tomosynthesis, digital contrast-enhanced mammography and the combination of digital mammography and ultrasound. The future in breast diagnosis will be the fusion of images from different digital systems.

Image Quality of Digital Direct Flat-Panel Mammography Versus an Analog Screen-Film Technique Using a Phantom Model

OBJECTIVE

The objective of our study was to compare the detection and distinguishability of microcalcifications on mammograms obtained with a digital direct flat-panel detector versus an analog system using an anthropomorphic breast phantom.

MATERIALS AND METHODS

Studies were performed with a digital mammography system (Selenia) and an analog mammography system (Mammomat 3). Sixty-five transparent films were used as test specimens. Randomly distributed round and heterogeneous silicate particles (diameter, 100-1,400 microm) and an anthropomorphic scatter body were applied to the films. All radiographs were taken at identical settings and exposures. Six radiologists rated the films and monitor-displayed images independently of each other in random order on a standardized electronic questionnaire.

RESULTS

Interpretations based on monitor reading produced superior results over those based on digital image reading and analog film reading. In 41.1% (95% CI, 38.7-43.5%) of all the monitor readings, 20.2% (18.2-22.2%) of all digital images, and 19.6% (17.6-21.6%) of all analog films, the number of detectable microcalcifications agreed with the gold standard method. The diameter of visible microcalcifications was interpreted correctly in 35.6% (33.2-38.0%) of monitor readings, 19.0% (17.1-21.0%) of digital images, and 21.0% (18.9-23.0%) of analog films; and microcalcification shape was interpreted correctly in 53.8% (51.4-56.3%) of monitor readings, 28.2% (26.0-30.4%) of digital images, and 28.3% (26.0-30.5%) of analog films. Microcalcification number and size were underestimated more frequently than overestimated. Regardless of display medium, accuracy increased proportionately with the diameter of the simulated microcalcifications for all evaluation variables.

CONCLUSION

Digital flat-panel mammography is superior to the analog screen-film method for the detection and morphologic characterization of microcalcifications larger than 200 microm in diameter when the display medium is a monitor.

Digitale Radiographie und Fluoroskopie

For 110 years, x-rays and special x-ray films have been used in medical diagnostics. New developments in the field of x-ray techniques, and especially new computer applications, have led to new imaging techniques which have substantially expanded the spectrum of radiological examinations. In spite of significant technological and medical advances in the field of MRI and multidetector-CT, radiographic images of the lungs, skeleton and organs still comprise up to 80% of the routine radiological workload. The increasing availability of digital detectors has led to the continual replacement of conventional film/screen systems. The inclusion of digital mammography was delayed due to the higher requirements for spatial resolution. For about 2 years, dynamic flat panel detectors have started to replace the image intensifier which has been used in fluoroscopy for 40 years.

[Clinical results of digital mammography]

Digital mammography is the technology of the future in breast diagnosis. This article provides an overview of all digital mammography units admitted by the Food and Drug Administration (FDA), results of clinical studies, soft copy reading, CAD (computer aided detection), and presents an overview on possible further developments. It is obvious that clinical results are equivalent to conventional screen film mammography and digital mammography.