1、European Journal of Radiology 72(2009)194201Contents lists available at ScienceDirectEuropean Journal of Radiologyjournal homepage: and CR:Recent advances in technologyC.M.Schaefer-Prokopa,b,D.W.De Boob,M.Uffmannc,M.ProkopdaMeander Medical Center Amersfoort,Utrechtseweg 160,3800 BM Amersfoort,Nether
2、landsbAcademic Medical Center(AMC)Amsterdam,Meibergdreef 9,1105 AZ Amsterdam,NetherlandscUniversity Hospital Vienna(AKH)Vienna,Dep of Radiology,Waehringer Guertel 18-20,1090 Vienna,AustriadUniversity Medical Center(UMC),Utrecht,Image Science Center,Heidelberglaan 100,3584 CX Utrecht,Netherlandsa r t
3、 i c l ei n f oArticle history:Received 7 May 2009Accepted 7 May 2009Keywords:Digital radiographyDetector systemsDose efficiencyPhysical performancea b s t r a c tAfter some initial reluctance,nowadays transition from conventional analogue-to-digital radiographictechniqueisrealizedinthevastmajorityo
4、finstitutions.Theeventualtriumphofdigitaloverconventionaltechnique is related to its undoubted advantages with respect to image quality and improved imagehandling in the context of a picture archiving and communication system.CR represents the older system,which matured over decades and experienced
5、some important recentimprovements with respect to dose efficiency and work-flow efficiency that strengthened its position.Itrepresents a very versatile,economically attractive system that is equally suited for integrated systemsas well as for cassette-based imaging at the bedside.DR systems offer su
6、perb image quality and realistic options for dose reduction based on their high doseefficiency.While for a long time only integrated systems were on the market suited for a large patientthroughput,also mobile DR systems became recently available.While for the next years,it is likely that DR and CR s
7、ystems will coexist,the long term perspective ofCR will depend on further innovations with respect to dose efficiency and signal-to-noise characteristicswhile for DR economical aspects and broader availability of mobile systems will play a role.2009 Published by Elsevier Ireland Ltd.1.IntroductionSi
8、nce its introduction almost 30 years ago,digital radiographyhasbecomeastandardtechnologyinmostinstitutions.Whileothertechniques,such as computed tomography or magnetic resonanceimaging were digital since their introduction,projection radiogra-phy made the transition from analogue-to-digital techniqu
9、e ratherlate.The eventual triumph of digital over conventional technique isrelated to its undoubted advantages with respect to image qualityand improved image handling in the context of a picture archivingand communication system.Purpose of the following overview is to familiarize the readerwiththev
10、ariouscurrenttechniques,tosummarizerecentadvancesin detector technology and to discuss aspects that are critical forclinical practice.The relationship between dose and image quality,controlof radiation dose in digital radiography and advanced imageprocessing will be discussed in separate articles wi
11、thin thisissue.Corresponding author at:Academic Medical Center(AMC)Amsterdam,Meibergdreef 9,1105 AZ Amsterdam,Netherlands.E-mail address:S(C.M.Schaefer-Prokop).2.Detector systemsThe physical properties of the detector systems translate intovarious advantages and disadvantages with respect to image q
12、ual-ity,equipment handling and cost 1,2.Detector systems differ withrespect to the image receptor material,the readout process and thedata processing.Advances occur not only with the introduction of new detectorssystems but also with further refinement of existing technologiesin terms of dose effici
13、ency and spatial resolution.It is no longersufficient to globally refer to computed radiography,CR,or directradiography,DR,but one has to take specific generation of technol-ogy into account when comparing system performance 3.2.1.Computed radiography CR(storage phosphor radiography)Computed radiogr
14、aphy,CR,was the first digital radiographictechnique to be introduced.CR systems are based on an imagingplate that is similar to the amplifier screen of conventional screensfrom radiography.As opposed to the screens from conventionalradiography,this storage phosphor imaging plate retains the infor-ma
15、tion of the incident photons as a latent image which can later beretrieved by stimulation by a read-out laser.Theimageplateiscoatedononesidewithalayerofphotostimu-lable phosphor material,which consists of a thin layer of phosphor0720-048X/$see front matter 2009 Published by Elsevier Ireland Ltd.doi:
16、10.1016/j.ejrad.2009.05.055C.M.Schaefer-Prokop et al./European Journal of Radiology 72(2009)194201195crystals embedded in a binder.The commonest phosphor materialis BaFX:Eu2+with X representing bromine or iodine atoms.Expo-sureoftheimageplatetoX-rayphotonsstimulateselectronswithinthephosphorlayerandtrapstheminameta-stablestate.Thislatentimage of high-energy electrons can be read out by a thinly focusedlaser beam that releases the trapped electrons from their meta-stable state.When returning to t
