iaea human health series publications - SEDIM

Potential challenges or disadvantages associated with digital mammography include:— Higher capital costs.— The increased time required for image interpretation coupled with a need for radiologists to adjust to newimage attributes.— The need for radiologists, radiographers, clerks, etc., to adjust to new technology.— Possible increased patient dose. 2— Difficulties in comparing digital images with film mammograms.— Poorer technical performance characteristics of some digital systems compared with screen film, as expressedby their modulation transfer function (MTF), detective quantum efficiency (DQE) and signal difference tonoise ratio (SDNR).— Incompatibility between different digital systems.— Difficulty in providing images to nondigital facilities (e.g. referring physicians).— The increased complexity of technology leading to increased service costs.— The need to interface the operation of several computer systems (image viewing, patient worklist, reporting),often provided by different vendors.— Availability of suitably trained service personnel.— Equipment reliability problems (e.g. detector failures due to abnormal temperatures).— More demanding environmental requirements (e.g. properly conditioned electrical power, dust control andlighting conditions, Internet connections, ventilation and air conditioning). For example, many digital unitsrequire air conditioning to be provided 24 hours a day, 7 days a week to prevent damage to the detector.All these factors should be taken into account when any facility contemplates making the transition fromscreen film to digital mammography. In particular, the capital and maintenance costs of digital mammographyequipment are considerably higher than those of screen film systems, although there are some offsetting costsavings (no film, processing chemistry, processor maintenance or film library). This factor, combined withuncertainty concerning the clinical and other advantages of digital mammography and concerns about buying asystem that might quickly become obsolete (although the technology has now begun to stabilize), has resulted inrelatively slow uptake of this technology. Balancing these factors may mean that, in many facilities, mammographyis the last analogue (film) technology holdout, although there is a strong incentive to become completely digital andto eliminate the costs and inefficiencies associated with chemical processing and archiving of films.2.2. FACTORS TO CONSIDER IN CHOOSING A DIGITAL MAMMOGRAPHY SYSTEMIn some countries, the sale of digital mammography equipment is heavily regulated and the manufacturer hasto demonstrate that performance meets certain standards. In others, standards are far less demanding. Whether ornot rigorous standards exist in a given Member State, when considering the purchase of a digital system, it isvaluable to examine whether that system has been approved in countries that do enforce such standards. It maytherefore be useful to refer to the web sites of national or regional agencies such as the European ReferenceOrganisation for Quality Assured Breast Screening and Diagnostic Services (EUREF) (www.euref.org), the UnitedKingdom’s National Health Service Breast Screening Programme (www.cancerscreening.nhs.uk/breastscreen/), theUnited States Food and Drug Administration (FDA) (http://www.fda.gov/cdrh/mammography) or other nationalsites where lists of acceptable models or assessment reports of performance are available.The digital mammography system is a complex chain that includes the X ray unit and detector, software,display workstations, the picture archiving and communications system (PACS) and, possibly, printers. For thesystem to be effective and to provide improved performance over film mammography, all these components mustbe of high quality and must work effectively together. An example of the sort of problems that can occur whencomponents do not work together is given in Ref. [17].2It should be noted that depending on the system design, the choice of technique factors and attention to QC, doses in digitalmammography can be either lower or higher than those in screen film mammography.4