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8.6.2. Alternative procedure: Limiting spatial resolutionIf it is not possible to perform the MTF measurement, a less suitable alternative is to measure the limitingspatial resolution in a manner similar to that used for screen film mammography [8, 59, 60].8.6.2.1. Scope— Objective: To determine the high contrast resolution limit.— Minimum frequency: Annually and after equipment changes to the detector or X ray tube.8.6.2.2. Instrumentation(1) Star or bar resolution pattern covering at least the range 5–12 line pairs (lp)/mm.(2) PMMA slabs.(3) Magnifier lens (4× to 5× magnification).8.6.2.3. Methodology(1) Place the resolution pattern centrally on top of 45 mm of PMMA, with the closest edge 10 mm from the chestwall and with the bars oriented at approximately, but not exactly, 90° with respect to the chest wall edge of thebreast support table. The slight rotation of a few degrees is intended to avoid moiré effects.(2) Ensure that any image processing and detector correction algorithms (except for flat field correction) areturned off.(3) Confirm that the AEC sensor is not under the resolution pattern. Image the pattern using the technical factors(kV, grid, target, filter) used clinically for a compressed breast of 45 mm.(4) View the image on the monitor of the available workstation with at least a 1:1 zoom factor. If hard copy isnormally used with the system, the image could be viewed on the printed film with the aid of a magnifyinglens. Note the number of line pairs that can be observed clearly, starting with the most easily resolved.(5) Note the result on the data collection sheet.(6) Repeat the measurement with the bars oriented at approximately, but not exactly, 0°. For convenience, the twomeasurements can be done simultaneously, if the appropriate bar or star pattern is available.8.6.2.4. Interpretation of results and conclusionsTolerances:(1) Baseline value: Achievable — The limiting spatial resolution (in lp/mm) should not fall below the valueslisted under the 20% column in Table 17.(2) The limiting spatial resolution should not decrease in time by more than 10% from the baseline value.8.6.2.5. Recommendations and corrective actions(1) If variations in the resolution are observed, the cause should be identified (e.g. detector damage, change ofsize of the focal spot). If necessary, consult the manufacturer’s service representative for assistance inresolving the problem.(2) If the resolution of an image viewed on hard copy film does not meet the spatial resolution requirement,ensure that the problem is not caused by laser printing (see Section 8.11).8.6.2.6. Time frame for corrective actionImmediately: Corrective action should be taken before any further patients are imaged.108
8.7. X RAY EQUIPMENT CHARACTERISTICS8.7.1. Half value layer (HVL)8.7.1.1. Scope— Objective: To measure the HVL and to confirm that the total filtration of the X ray beam is in agreement withthe minimum requirements of the national and international standards [8, 59–62].— Minimum frequency: At commissioning, annually and after changes to or maintenance of the X ray tube, tubehousing and/or collimation system.8.7.1.2. Instrumentation (see Appendix II)(1) Appropriate dosimeter system for mammography.(2) Aluminium filters.(3) Measuring tape.(4) Metal plate to shield the detector from X rays (e.g. 1 mm steel, 5 mm aluminium or >0.1 mm lead), largeenough to cover the active area of the detector.8.7.1.3. Methodology(1) Place the metal shielding material on the breast support table to protect the detector from excessive radiationexposure that could cause artefacts.(2) Select the manual mode of operation and the target–filter–kV combinations selected by the AEC for 20, 45and 70 mm thicknesses of PMMA (see Section 8.4.2).(3) Place the dosimeter at a height of 45 mm above the breast support, centred laterally, and 40 mm from the chestwall edge, so that the sensitive volume of the chamber remains completely within the radiation field.(4) Collimate the radiation field to be just slightly larger than the sensitive volume of the dosimeter using theinternal collimators and/or an aperture in a heavily attenuating metal sheet placed on the compression paddle.(5) Place the compression paddle 22 approximately halfway between the X ray target and the dosimeter.(6) Make an exposure and record the reading on the beam quality (HVL) chart (Chart 10 in Annex II).(7) Place 0.3 mm of aluminium (or 0.4 mm, depending on the target–filter–kV combination that has beenselected) on the compression paddle above the aperture, totally covering the active volume of the chamber,and make an exposure with the same parameters. Check that the reading is more than half the reading withoutthe filter. If it is not, use a thinner aluminium thickness.(8) Add 0.1 mm (or 0.025 mm, for more precision) of aluminium and repeat the previous step. Check that thereading is less than half the reading without the filter. Otherwise, add more aluminium until the reading fallsbelow half the reading without the filter.(9) Remove all the filters and repeat the exposure. Take note of the reading.(10) Repeat this procedure for the other selected target–filter–kV combinations.8.7.1.4. Procedure of calculation(1) Calculate the value of the HVL, based on the following expression:HVL =t ln[ 2M / M ] - t ln[ 2M2/M ]1 1 0 2 0ln[ 2M/ M ]1 2(3)22For the calculation of MGD, it is necessary to measure the HVL with the compression paddle in the beam. To compare theHVL with the manufacturer’s specifications, which follow IEC standards, the measurement of the HVL would be done without thecompression paddle.109
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X raysdel matrixCs scintillatorLine
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QUALITY ASSURANCE PROGRAMMEFOR DIGI
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IAEA HUMAN HEALTH SERIES No. 17QUAL
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FOREWORDThe application of radiatio
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An effective QA programme is necess
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The Integrating the Healthcare Ente
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technology. Systems containing othe
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X raysTop electrodea-Se layerCharge
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dose received by inhomogeneous real
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2.3.8.1. Soft copy displayFlat pane
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3. ELEMENTS OF HIGH QUALITY MAMMOGR
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— The ability to mask edges of ma
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Disposal orsaleNew facility(start h
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4.2.3. Radiographer (mammography te
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5.2.2. Electronic versus geometric
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To allow full utilization of the di
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5.7. ARTEFACTSWhile the incidence o
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FIG. 10. Detector crystallization.
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FIG. 13. A more subtle example of a
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FIG. 16. An example of poor collima
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7. RADIOGRAPHER’S QUALITY CONTROL
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7.1. DAILY TESTS7.1.1. Monitor insp
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7.1.3. Daily flat field phantom ima
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7.1.4. Visual inspection for artefa
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7.1.5. Laser printer sensitometry7.
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7.1.6. Image plate erasure (CR syst
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FIG. 19. Modified TG18-QC pattern w
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FIG. 21. Radiologist workstation wi
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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
Page 81 and 82: 7.3.3.5. Recommendations and correc
Page 83 and 84: 7.4.1.3. Methodology(1) Annotate th
Page 85 and 86: RECORD OF DIGITAL MAMMOGRAPHY REPEA
Page 87 and 88: (3) Including examinations of at le
Page 89 and 90: 7.5. SEMI-ANNUAL TESTS7.5.1. Comput
Page 91 and 92: 8. MEDICAL PHYSICIST’S QUALITY CO
Page 93 and 94: 8.1. NOTE ON IMAGE NAMING CONVENTIO
Page 95 and 96: (16) On any randomly selected patie
Page 97 and 98: FIG. 30. Positioning of bathroom sc
Page 99 and 100: (6) The target, filter, kV, grid, d
Page 101 and 102: (2) Stack the 20 and 25 mm PMMA sla
Page 103 and 104: TABLE 13. ACCEPTABLE AND ACHIEVABLE
Page 105 and 106: 8.5. DETECTOR PERFORMANCE8.5.1. Bas
Page 107 and 108: 8.5.2. Detector response and noise8
Page 109 and 110: the service engineer responsible fo
Page 111 and 112: (13) Using the annotation tool on t
Page 113 and 114: Breast supportPMMA slabBreast suppo
Page 115 and 116: (10) Place the thinner test object
Page 117 and 118: 8.6. EVALUATION OF SYSTEM RESOLUTIO
Page 119: TABLE 17. ACCEPTABLE FREQUENCIES AT
Page 123 and 124: 8.7.2. Incident air kerma at the en
Page 125 and 126: 8.8. DOSIMETRY8.8.1. Mean glandular
Page 127 and 128: TABLE 21. ACCEPTABLE AND ACHIEVABLE
Page 129 and 130: FIG. 34. Suggested layout for ruler
Page 131 and 132: 8.10. IMAGE DISPLAY QUALITYThe accu
Page 133 and 134: FIG. 35. Modified TG18-QC test patt
Page 135 and 136: 8.10.1.5. Interpretation of results
Page 137 and 138: 8.10.2. Monitor luminance response
Page 139 and 140: TABLE 22. MONITOR PERFORMANCE TOLER
Page 141 and 142: FIG. 38. Measurement of illuminatio
Page 143 and 144: 8.11. LASER PRINTER8.11.1. Laser pr
Page 145 and 146: 8.11.1.5. Recommendations and corre
Page 147: 8.12.1.4. Interpretation of results
Page 150 and 151: iopsies are performed, a sink is of
Page 152 and 153: Appendix IISPECIFICATIONS OF TEST E
Page 154 and 155: TABLE 24. SPECIFICATIONS OF TEST EQ
Page 156 and 157: FIG. 40. Image acquired with a unif
Page 158 and 159: FIG. 43. The left hand image is par
Page 160 and 161: FIG. 45. A TG18-QC test pattern dis
Page 162 and 163: [29] ALSAGER, A., YOUNG, K.C., ODUK
Page 165 and 166: Annex IRADIOGRAPHER DATA COLLECTION
Page 167 and 168: Chart 2 — DIGITAL MAMMOGRAPHY (DM
Page 169 and 170: 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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