iaea human health series publications - SEDIM

5.3.3. Differences in image evaluationImage interpretation in digital mammography is no different from that in screen film mammography, althoughit may take a little while to get used to the different ‘look’ of the digital images. The radiologist still looks formasses, asymmetric densities, architectural change and calcifications. However, digital mammography provides theopportunity for excellent mammography image quality with superior low contrast resolution at acceptable spatialresolution for easier detection of microcalcifications. This improves image interpretation and level of confidence.In addition, image processing software (specifically window and levelling) can be utilized to adjust for tissue‘thickness’, allowing visualization of skin and subcutaneous tissues at the breast periphery and making imageinterpretation easier in the thinner parts of the breast. Historically, this part of the breast would have been regardedas ‘overexposed’. Image processing may also improve visualization of specific suspicious features such ascalcifications and enhance subject contrast, thus also reducing the risk of missing abnormalities.5.3.4. Use of computer aided detectionCAD algorithms are more efficiently applied to digital images than to films, as the time and expense ofdigitization is eliminated. Studies have shown that CAD can increase cancer detection by a single reader to a levelcomparable with that achieved by double reading of the same study by two different radiologists [41–43]. There iscertainly the potential for CAD systems to be developed that not only will contribute to the detection of suspiciousabnormalities in the mammogram, but will also indicate the probability of malignancy with a particular appearance.However, it is the radiologist who must ultimately decide if the areas marked are significant, as with current CADsystems more false positives than true lesions are marked.5.4. IMAGE STORAGE AND COMMUNICATION5.4.1. PACS and RIS considerationsDigital mammographic images stored in the PACS can be viewed at multiple locations within a facility, sothat reporting, teaching and consultation can occur rapidly. One advantage of this is possible improved access toavailable radiologists and experts. Another is that it is difficult to lose images, either past or present, if they arestored in the PACS and are labelled correctly. Backup systems are required, as servers can fail.There are some issues related to the storage of image data, specifically:— The PACS should be able to interface with mammography systems from different vendors and with differentmodalities such as ultrasound and MRI. All such images should be able to be displayed equally well at eachworkstation.— Some facilities are reluctant to store ‘for processing’ images due to the associated increased cost.— It may be necessary to manually ‘push’ (i.e. transfer electronically) prior digital mammograms from PACSstorage to the dedicated mammography review workstations. However, automatic ‘pulling’ of prior imagesshould be possible, and it is important that facilities press their PACS vendors to provide the safest and mostefficient workflow possible.— Very large data sets may be generated in the future with breast tomosynthesis, and this will further challengestorage capacities.— Problems can arise when sharing digital mammographic images on computer disks (CD, USB or DVD media)with another facility. CDs often include limited software capability to view and adjust images and may bereviewed by clinicians on ordinary computer monitors rather than on the high resolution 5 MP monitors usedby radiologists. It is therefore important that when disks are written, the DICOM images are transferredcorrectly and the destination site has the facilities to upload the images to a diagnostic workstation. It is clearthat at present not all digital mammography images are optimally displayed on all workstations. CD transferof information may require data encryption or other methods to ensure patient record confidentiality.27