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TABLE 3. TYPICAL TARGET–FILTER COMBINATIONS FOR DIGITAL MAMMOGRAPHYTarget Filter Thickness, in mmMo Mo 0.03 (GE, Planmed, Fujifilm, Siemens, Giotto)Mo Rh 0.025 (GE, Planmed, Fujifilm, Siemens, Giotto)Rh Rh 0.025 (GE)W Al 0.3 (Sectra D40), 0.43 (Sectra L30)W Rh 0.06 (Hologic, Planmed)0.05 (Fujifilm, Siemens)W Ag 0.06 (Hologic)0.075 (Planmed)0.05 (Giotto)3.2.2. Viewing conditionsIn digital mammography, images are generally viewed on a display monitor. Unlike film, the electronic displaycan be adjusted; to facilitate the ability to detect subtle lesions or anatomic features, the display must be properlycalibrated to match the performance of the <strong>human</strong> visual system. Therefore, it is helpful to have some understandingof psychophysical factors of vision [30, 37, 38]. The ability of a <strong>human</strong> viewer to detect a change in brightness, ΔL, isdependent on the average brightness, L, of the area surrounding the image. The smallest visibly detectable change inbrightness, ΔL min , is referred to as the ‘just noticeable difference’, or jnd. The size of a jnd tends to be constant forluminance levels above 100 candelas per square metre (cd/m 2 ); at lower luminance levels, the jnd increases rapidly(i.e. greater changes in brightness are required to evoke a visual response that there is a difference).The approach to calibration of a display for digital imaging is to apply ‘perceptual linearization’ to the imagedata that are to be displayed, such that each step in the image signal sent to the display represents an equalincrement of perceived contrast; that is, a constant number of jnds regardless of L. In other words, to achieve alinear range of perceived contrast steps, an unequal spacing of luminance levels is applied, depending on theluminance.Perceptual linearization is based on the relationship between the jnd and L, and is the basis of the DICOMGSDF, which aims to enforce consistency of medical images across various display devices. While there is littleconcern for constant rendition of jnd with film display devices owing to the typical luminance levels involved, thisis not the case with soft copy displays. In this case, contrast enhancement at low luminance levels can be achievedby GSDF calibration.3.2.2.1. Soft copyViewing conditions are very important for image interpretation from a monitor, especially given the lowluminance of the monitors [24–26]. There should be no glare reflected from the screen, and the walls behind thescreen should be about the same colour and intensity as a mid-grey background on the screen, with the backgroundroom illumination at around 30 lux (lx). There should be no distracting icons on the image screens, and radiologistsshould be positioned such that they are at the distance where they have maximum acuity.3.2.2.2. Hard copyIf hard copy digital mammograms and mammography films from prior studies are to be viewed, the followingconditions should be met:— A viewbox designed for mammography with a luminance of greater than 3000 cd/m 2 ;— Lamps in the viewbox matched for brightness and colour;18
— The ability to mask edges of mammograms;— Low ambient light in room.As film designed for laser printing has a lower maximum optical density than does mammography film, lowerviewbox luminance is required. Therefore, a viewbox with adjustable luminance should be available.3.2.3. Quality assuranceTo ensure high quality, all of the above conditions must be met; however, in addition, it is essential that acomprehensive QA programme be in place. It is also imperative that time be allocated to allow the tests to beperformed regularly, that results be carefully recorded and that corrective action be taken promptly when indicated.The basic elements of a QA programme for digital mammography are outlined in Section 4.3.2.4. Regular maintenanceIn addition to regular QA, it is also essential that all digital mammographic units and associated equipment besubjected to regular maintenance consistent with best practice or with the recommendations of the manufacturer.19
Page 1 and 2: X raysdel matrixCs scintillatorLine
Page 3 and 4: QUALITY ASSURANCE PROGRAMMEFOR DIGI
Page 5 and 6: IAEA HUMAN HEALTH SERIES No. 17QUAL
Page 7 and 8: FOREWORDThe application of radiatio
Page 14: An effective QA programme is necess
Page 17 and 18: The Integrating the Healthcare Ente
Page 21 and 22: technology. Systems containing othe
Page 23 and 24: X raysTop electrodea-Se layerCharge
Page 25 and 26: dose received by inhomogeneous real
Page 27 and 28: 2.3.8.1. Soft copy displayFlat pane
Page 29: 3. ELEMENTS OF HIGH QUALITY MAMMOGR
Page 34 and 35: Disposal orsaleNew facility(start h
Page 36 and 37: 4.2.3. Radiographer (mammography te
Page 38 and 39: 5.2.2. Electronic versus geometric
Page 40 and 41: To allow full utilization of the di
Page 42 and 43: 5.7. ARTEFACTSWhile the incidence o
Page 44 and 45: FIG. 10. Detector crystallization.
Page 46 and 47: FIG. 13. A more subtle example of a
Page 48 and 49: FIG. 16. An example of poor collima
Page 51 and 52: 7. RADIOGRAPHER’S QUALITY CONTROL
Page 53 and 54: 7.1. DAILY TESTS7.1.1. Monitor insp
Page 55 and 56: 7.1.3. Daily flat field phantom ima
Page 57 and 58: 7.1.4. Visual inspection for artefa
Page 59 and 60: 7.1.5. Laser printer sensitometry7.
Page 61 and 62: 7.1.6. Image plate erasure (CR syst
Page 63 and 64: FIG. 19. Modified TG18-QC pattern w
Page 65 and 66: FIG. 21. Radiologist workstation wi
Page 67 and 68: 7.2.1.6. Time frame for corrective
Page 69 and 70: 7.2.3. Weekly quality control test
Page 71 and 72: Note: It is not necessary to view t
Page 73 and 74: TABLE 7. TOLERANCES FOR IMAGING WEE
Page 75 and 76: 7.2.4.4. Interpretation of results
Page 77 and 78: 7.3.1.5. Recommendations and correc
Page 79 and 80: artefacts are typically best seen w
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7.3.3.5. Recommendations and correc
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7.4.1.3. Methodology(1) Annotate th
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RECORD OF DIGITAL MAMMOGRAPHY REPEA
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(3) Including examinations of at le
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7.5. SEMI-ANNUAL TESTS7.5.1. Comput
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8. MEDICAL PHYSICIST’S QUALITY CO
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8.1. NOTE ON IMAGE NAMING CONVENTIO
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(16) On any randomly selected patie
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FIG. 30. Positioning of bathroom sc
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(6) The target, filter, kV, grid, d
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(2) Stack the 20 and 25 mm PMMA sla
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TABLE 13. ACCEPTABLE AND ACHIEVABLE
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8.5. DETECTOR PERFORMANCE8.5.1. Bas
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8.5.2. Detector response and noise8
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the service engineer responsible fo
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(13) Using the annotation tool on t
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Breast supportPMMA slabBreast suppo
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(10) Place the thinner test object
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8.6. EVALUATION OF SYSTEM RESOLUTIO
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TABLE 17. ACCEPTABLE FREQUENCIES AT
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8.7. X RAY EQUIPMENT CHARACTERISTIC
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8.7.2. Incident air kerma at the en
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8.8. DOSIMETRY8.8.1. Mean glandular
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TABLE 21. ACCEPTABLE AND ACHIEVABLE
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FIG. 34. Suggested layout for ruler
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8.10. IMAGE DISPLAY QUALITYThe accu
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FIG. 35. Modified TG18-QC test patt
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8.10.1.5. Interpretation of results
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8.10.2. Monitor luminance response
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TABLE 22. MONITOR PERFORMANCE TOLER
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FIG. 38. Measurement of illuminatio
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8.11. LASER PRINTER8.11.1. Laser pr
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8.11.1.5. Recommendations and corre
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8.12.1.4. Interpretation of results
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iopsies are performed, a sink is of
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Appendix IISPECIFICATIONS OF TEST E
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TABLE 24. SPECIFICATIONS OF TEST EQ
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FIG. 40. Image acquired with a unif
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FIG. 43. The left hand image is par
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FIG. 45. A TG18-QC test pattern dis
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[29] ALSAGER, A., YOUNG, K.C., ODUK
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Annex IRADIOGRAPHER DATA COLLECTION
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Chart 2 — DIGITAL MAMMOGRAPHY (DM
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Chart 4 LASER PRINTER SENSITOMETRY
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Chart 6 — WEEKLY DISPLAY MONITOR
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Chart 7(b) WEEKLY QC TEST OBJECT:
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Chart 9 — SAFETY AND FUNCTION CHE
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Chart 11 — LASER PRINTER ARTEFACT
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Chart 13(a) — RECORD OF DIGITAL M
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Chart 14 — CR PLATE SENSITIVITY M
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Annex IIITHE MAMMOGRAPHY EXTRACTThe
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GLOSSARYair kerma. The energy depos
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image quality. The overall merit of
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CONTRIBUTORS TO DRAFTING AND REVIEW
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