Additional digital mammography information
Recent publications indicate that digital mammography provides equal or superior accuracy to screen-film mammography. Digital mammography also has potential for increased efficiency in image archiving and retrieval and the possibility of avoiding the costs, complexity and waste disposal problems associated with chemical processing of film. These factors have stimulated interest in the acquisition of digital systems. This presents both opportunities and challenges to those involved in delivering mammography services. One of the important challenges is to have in place in a timely fashion, an appropriate framework of quality assurance for digital mammography systems
Transition to digital mammography
There is currently considerable enthusiasm regarding digital mammography and many facilities are interested in purchasing such systems. In the IAEA digital mammography document, some of the factors affecting performance of digital mammography and those technical elements that distinguish performance of one system from another are considered. It must also be recognized that while digital mammography will almost certainly eventually supplant film mammography, it is still a new technology with very high capital costs. In addition, there are other important considerations regarding the purchase of a digital system including costs of preparing the installation (electrical supply, cooling, etc.), requirements of computer information systems, service costs, cost of maintaining the system at the state of the art, and training of personnel. In addition, with this new technology, there may be efficiency differences (both positive and negative) in producing and interpreting the mammograms
Principles of QA
A quality assurance (QA) programme in diagnostic radiology, as defined by the WHO, is an organized effort by the staff operating a facility to ensure that the diagnostic images produced are of sufficiently high quality so that they reliably provide adequate diagnostic information with both the lowest possible cost and the least possible exposure of the patient to radiation consistent with the requisite level of image quality. The establishment of a comprehensive QA program for medical diagnosis is required for this with the technical aspects of such a programme under the supervision of an appropriate medical physicist.
Relevant Human Health Website cross-links: Technology Management
Clinical image quality
While image reading is not substantially different from that of screen-film systems, the process for image review is. Therefore, radiologist training is required in the use of workstation tools and the RIS/PACS. Both radiologist and radiographer training in the use of vendor specific RIS/PACS features, 'new' digital workflow processes, display protocols and use of software tools is essential.
To allow full utilisation of the digital environment in mammography, especially in a breast screening environment, both a PACS and an integrated RIS are required. This integration should preferably be seamless to facilitate well planned workflow customised to the practice's needs to maximise efficiency.
The tests provided in the IAEA QA document form a QC programme for the radiographer and in most cases offer a replacement for tests that are in the manufacturer's programme. It is not necessary to perform both sets of tests. This programme does not include maintenance or calibration procedures. Maintenance and calibration activities should be performed by the appropriate individual according to the manufacturer's instructions.
A brief description of the methodology to be undertaken when performing the radiographer's QC tests is provided. The order in which tests are performed does not necessarily have to be that in which they appear in this document. The preferred order will depend on various factors relating to the mammography facility as well as the preferences of the individual performing the testing, always having in mind that the results of one test may affect the execution of others. Data collection sheets are found in link below.
Relevant documents: Annex 1 Radiographer data collection sheets (worksheet)
Medical physics tests
The tests provided in the IAEA QA document form a QC programme for the medical physicist. In addition to periodic testing, all tests should be performed at commissioning, i.e. before the equipment is initially used to image patients. Some commissioning tests are necessary to set up the base line values needed for the radiographer QC tests. In some cases, the medical physicist may also be responsible for performing some of the tests described in the section on radiographer's tests. Data collection sheets can be found below.
For many of the tests, it is useful to carry out the analysis of images on a separate computer. For this purpose it is desirable that test images be exported in "For Processing" DICOM format from the digital mammography system. In addition, to facilitate testing of the softcopy and hardcopy displays, it is desirable to be able to import test images to the digital mammography system in a convenient manner, information on importing and exporting data can be found in the links below.
a. Worksheets Annex 2 Medical physicist data collection sheets
b. Monitor test pattern
c. Resolution testing and Noise related measurements - under construction
d. Film hardcopy - IAEA Screen-Film Mammography publication - Human Health Campus website screen-film mammography page