Presentation on theme: "Safety Code 35 John Aldrich PhD FCCPM Regional Leader Clinical Physics"— Presentation transcript:
1 Safety Code 35 John Aldrich PhD FCCPM Regional Leader Clinical Physics Kevin Hammerstrom RTNMQC CoordinatorDepartment of RadiologyVancouver Coastal HealthUniversity of British Columbia
2 Medical X-ray Safety Codes Safety Code 20A (1976)Recommended safety procedures for the installation, use and control of x-ray equipment. Mainly concerned with the x-ray output parameters of the equipmentOnly film processor QC definedSafety Code 35 (2008)(two drafts in 2005 and 2007)Comprehensive safety procedures for the installation, use and control of x-ray equipment.Includes all x-ray systemsIncreased emphasis on patient dose25% of the Code is concerned with QC of digital imaging systems
3 Safety Code 35 A1. Responsibilities of owners and users (4) A2. Procedures for minimizing staff dose (2)A3. Procedures for minimizing patient dose (6)B1. Facility shielding (3)B 2-6. Equipment performance (15)C 1-3. Quality Control (17)Appendices (30)
4 Decoding the Code Handout includes all slides in our presentations Normal Font – Required Test (“must do”)Italics - Recommended Test (“recommended”)Required Tests currently recommended by RPSHandout includes all slides in our presentationsAttached sheets have all the tables enlargedReferences are to details of the tests in the Codeeg D1 is the first daily test listed, W1 – weekly,M1 - monthly, Q1 – quarterly, SY1 – semi-annually, Y1 - Annual
5 Overview Session 1 Requirements for all systems 20 Radiation Protection10QuestionsRadiography (Film/DR/CR)Radioscopy (Fluoroscopy, Angio, DF)LUNCH
6 Overview Session 2 After Lunch CT20Equipment Purchase/ Acceptance Testing15Patient doseQuestions10Personnel qualificationsEducation and training
7 Daily Quality Control Tests Normal Font – Required Test (“must do”)Italics - Recommended Test (“recommended”)Required Tests currently recommended by RPSQuality Control ProceduresFilm-basedAll SystemsDaily Quality Control TestsEquipment Warm-up (D1)According to manufacturers instructionsCan include auto calibration eg CTMeters Operation (D2)Meter, visible and audible indicators should functionEquipment Conditions (D3)Visual inspection for loose or broken components, ease of movementsDarkroom Cleanliness (D5)(M DAP)Film Processor Function (D6)Overall Visual Assessment of Electronic Display Devices (D7)Display SMPTE or QC pattern for general image quality of all Radiologists’ workstationsCheck 5% and 95% areas visible
8 Weekly and Monthly Tests Quality Control ProceduresAll SystemsWeekly Quality Control TestsViewbox condition (W2)Visual inspection for cleanliness, colour, illuminationLaser Film Printer Operation (W3)Print pattern such as SMPTE or PQCCheck for 0/5% and 95/100% patch visibilityOD of 10% to 90% patchesNo artifacts or geometrical distortionMonthly Quality Control TestsDarkroom Temperature and Humidity (M2)Temp: 18-23C; Humidity 40-60%Darkroom Light Conditions (M3)Visual check for light tightnessFilm Processor Operation (M4)Temp ± 0.5C; Developer and fixer correct (M DAP)Electronic Display Device Performance (M6)Display pattern such as SMPTE or QC on all image display devicesLaser Film Printer Operation (M7)As W3 plus measurement of optical density of the 10% to 90% grey scaleNormal Font – Required Test (“must do”)Italics - Recommended Test (“recommended”)Required Tests currently recommended by RPS
9 Quarterly and Annual Tests Quality Control ProceduresAll SystemsQuarterly Quality Control TestsInterlocks (Q2)These are not usually used on diagnostic doorsAnnual Quality Control TestsSafelight Test (Y1)Expose film for 2 minFilm/Screen Contact (Y2)Image mesh and checkViewboxes (Y26)Check luminance, uniformity, homogeneity, ambient lightElectronic Display Device Performance (Y27)All clinical workstations must be calibrated for luminance, distortion, resolution and noiseIntegrity of Protective Equipment (Y28)Lead aprons, glasses, integral shieldsGeneral Preventive Maintenance (Y29)As per manufacturerNormal Font – Required Test (“must do”)Italics - Recommended Test (“recommended”)Required Tests currently recommended by RPS
10 Display QC Daily (D7) – for clinical interpretation Radiologist at each loginFind suitable SMPTE test patternMake accessible on PACSTest using various user logins/profilesAlert radiologists of requirement, frequency, and procedureIn addition to discussing the changes outlined in the new safety code, we wanted to provide a few examples of how meeting the new criteria can be accomplished. So…I will briefly highlight several of the QC procedures Dr. Aldrich has just mentioned.At a VGH Patient Safety and Quality of Care meetings late last year, I mentioned some of the changes to QC that would be expected if Safety Code 35 were adopted and enforced. One of those changes being a daily visual assessment of electronic displays used for interpretation of clinical images for general image quality and the presence of artifacts….D7. I also mentioned that the only practical way I imagined that task would be accomplished, considering the large number of displays at VGH, would be if the radiologists could view a test pattern each time they logged onto a PACS workstation to report images.One of the radiologists present wisely commented that if radiologists were to do so, it had to be easy and fast to perform. So, charged with this mandate, I found a SMPTE pattern and asked VCHA PACS administrators to find the best way to make the SMPTE pattern accessible on the Agfa Impax and iSite workstations.After some tweaking, that included finding a SMPTE pattern with higher resolution and figuring out how to display the SMPTE on both displays simultaneously, we performed some random tests over a few weeks to ensure the pattern work with all radiologist profiles. Once testing was complete, a memo and instruction sheet was circulated to all radiologists informing them of the new Safety Code requirement, what to look for in the SMPTE pattern, the pass/fail criteria and what to do if the visual assessment failed.
11 Problems with inconsistency Left Display – 5% visible / 95 % not visibleRight Display – 5% not visible / 95 % visibleOn Agfa Impax, the SMPTE pattern is accessed after login by left-clicking on a system wizard icon which then displays the same SMPTE pattern on both displays.On iSite workstations, the same occurs except the SMPTE pattern is accessed through a Public folder.Total assessment time should be seconds.This slide illustrates the importance of ensuring displays are calibrated. One can visualize the 5% and 95% squares of the SMPTE pattern….shown in the zoomed part of the image at the bottom of the slide.On the left display, the 5% square is visible but the 95% square is washed out and on the right display, the opposite is true.Obviously, one might miss important clinical information in the image if the displays were not calibrated.Should see both 5% and 95% squares if calibrated properly
12 Display QC Monthly (M6) All displays SMPTE test pattern / test TechnologistPACS administratorBiomedSMPTE test pattern / testpattern generator / vendorThe monthly assessment of all electronic displays devices used to view images from digital systems, as well as those obtained through scanning of radiographic films, using a test pattern (M6) may be a little more complicated since some of the systems connected to those displays may not be able to send a SMPTE pattern to the display.If that is the case, a Biomed engineer may be required to connect the display directly to a test pattern generator, similar to the one shown in the image, to perform the test and then reconnect the display to the xray unit.The two OR wall mounted displays shown have had third party calibration software loaded that is capable of generating a SMPTE pattern.
13 Display QC Annually (Y27) Clinical interpretation and interventional useQC CoordinatorPACS administratorBiomedSMPTE test pattern / test patterngenerator / vendor QC softwareand photometerFor the Annual assessment of displays, the SMTPE pattern is again the tool suggested in the safety code to determine whether the displays are functioning properly. That may be a good starting and ending point but it has been our experience that primary displays, or those used for clinical interpretation, need to be calibrated using software and an external photometer on a more frequent basis to ensure the displays are calibrated properly. Example are the Siemens SMfit ACT Calibration software and photometer for primary displays or Image Smith’s Verilum software and photometer for secondary displays, like those used in an OR or on a CR reader.We calibrate the primary display CRTs every 3 months and the LCD every 6 months. Secondary displays are calibrated annually.
14 Viewbox QC Weekly visual inspection (W2) Cleanliness Viewing area discolourationImproper luminanceClean, replace plastic or bulb if necessaryTechnologists / Biomed / Plant servicesA technologist should be able to perform weekly inspections of viewboxes to determine whether they need cleaning, need the plastic replaced due to discoloration, or if there is a visible discrepancy between panels that would require replacement of the bulb. Parts replacement would most likely involve Biomed or Plant services personnel.
15 Viewbox QC Yearly inspection (Y26) Technologist / physicist Maintain logsheetLuminance> 2500 cd/m2ShouldLight output uniformity+/- 10%Light output homogeneity+/- 20%Ambient light control< 50 lux (50 cd/m2)5-10 lux recommended (5-10 cd/m2)MustDepending on the equipment available, the yearly inspection of viewboxes may be performed by either a technologist or physicist. The two examples of photometers shown are both Minolta products. The one at the lower right is more typically associated with photography can not perform focused spot measurements while the LS-100 more suitable for performing precise spot measurements.Fortunately, the luminance, light output uniformity and light output homogeneity values listed are indicated as standards that “should” be met with ambient light control as the only one that “must” be met. In this case, 1 lux can be equated with 1 cd per sq m.To equate the units of luminance and illuminance (because both can be used to measure viewbox brightness), 1 lux of illuminance may be thought of as the reflectance of a perfectly diffusing surface to 1 candela/m2 (nit) of luminance (or 1 lux = 1 nit).
16 Viewbox QCIt has been our experience, that it is very difficult to meet some of the standards. To date we have been using the Canadian Mammography Quality Guidelines – for viewboxes used for mammography film interpretation and a test procedure outlined in the text Quality Management in the Imaging Sciences – Mosby, 1998, p for all other viewboxes.As you can see by the orange highlighted cells, failures have occurred. I will need to change the spreadsheet’s conditional formatting values to see if it passes with the new limits.In any event, it may be wise to create a spreadsheet with conditional formatting to make it easy to determine where failures occur.
17 Laser Film Printer QC Weekly (W3) Use same viewbox panel Print SMPTE from PACS workstation or from printer menuView 5% and 95% grayscale squaresMaintain logsheetWeekly laser film printer testing could be a task for either a technologist or a film library clerk.At VGH, the film library staff perform testing on the Agfa printer using a SMPTE pattern generated from the control panel and on the Fuji printer using the daily display test SMPTE image from a PACS workstation.
18 Laser Film Printer QCThey perform testing using a procedure I created, view the image on the same viewbox panel and then record the results on a logsheet.
19 Laser Film Printer QC Monthly (M7) Use same viewbox panel Print SMPTE from PACS workstation or from printer menuMeasure optical density of grayscale gradient squares, geometrical distortions, artifactsView 5% and 95% squares and compare densitometer readingsMaintain logsheetThe film printed by the film library staff could be used to measure the optical density of the grayscale gradient squares. A technologist or biomed person may be required to perform this additional step due since the film library person may not be trained on or have access to a densitometer.
20 Laser Film Printer QCI have been tracking the sensitometry results to ensure the two systems are performing similarly. As you can see, we still have some work to do.Testing of these “minor” components may seem like overkill and a waste of time but until we did so, we did not realize that IS had unexpectedly changed many IPs throughout the radiology department. This resulted in an inability to send images directly from the CR reader to the printers. Had PACS gone down, there would have been a panic to print and view images. With such a vast difference between the image quality of the two film printers, reporting errors may have occurred.So keep in mind that this type of QC may also be considered a system test.
21 Overview Session 1 Requirements for all systems 20 Radiation Protection10QuestionsRadiography DR/CRRadioscopy (Fluoroscopy, Angio), DFLUNCH
23 Radiation Safety Officer There must be a Medical Physicist or Radiation Safety Officer to advise on all aspects of Radiation SafetyPlanning, registration, inspectionWorking conditions, proceduresClassification of personnel, dosimetryRecord keeping, investigations
24 Radiation Protection - Shielding Design of ShieldingRecommend NCRP 147 (2004) methods which are based on empirical data(although Appendix is NCRP 49 (1976) which will tend to overshield rooms)Surveys of rooms must be done for new or altered rooms (equipment, use or vicinity Sec A5)Design shieldingCheck lead installationMeasure radiation in surrounding areas
25 Lead equivalence of aprons Lead ApronsLead equivalence of apronsSC 20A<150 kVp 0.5 mmSC 35< 100 kVp: mm100< kVp <150: mm>150 kVp: mm
26 Lead apron QC Annually (Y28) Radiographic / radioscopic Rejection if total defective area > 670 mm2Thyroid and reproductive areas < 5 mm diameter equivalent totalUntil now, I have been using the BCCDC document from March 1, 2003 entitled REJECTION CRITERIA FOR DEFECTS IN LEAD APPAREL USED FOR RADIATION PROTECTION OF X-RAY WORKERS to determine when protective apparel should be removed from use.Safety Code 35 differs a little in that the allowable size of the defective area for aprons has decreased by a third and for thyroid has increased by a multiple of 5.Again, we use logsheets to document the condition of the apron.
27 Overview Session 1 Requirements for all systems 20 Radiation Protection10QuestionsRadiography DR/CRRadioscopy (Fluoroscopy, Angio), DFLUNCH
28 Overview Session 1 Requirements for all systems 20 Radiation Protection10QuestionsRadiography DR/CRRadioscopy (Fluoroscopy, Angio), DFLUNCH
29 Baseline value determination Next constancy testing Equipment Life CycleAcceptance testingNew equipmentConformance to manufacturer’s specifications/RFPBaseline performanceRoutine performance evaluationsSpecific tests performed at regular intervalsConsistency checksEvaluate malfunctioning or out-of-spec equipmentBaseline value determinationDevice use periodNext constancy testingData evaluationWithin theestablished criteriaRemedyAcceptance testingFAILPASSThere is a distinction between acceptance testing and regularly performed QC. Acceptance testing is performed to verify the manufacturers claims and to verify compliance with regulatory standards. Constancy tests are performed to determine whether the performance of a device has changed after its installation/acceptance. More specifically, a certain test is conducted at appropriate intervals to check the deviation of the current performance value from the reference performance value (baseline value).If the measured performance value is within the predetermined acceptance deviation limit (established criteria), the device will be continuously used until the next test.If the measured performance value is outside the acceptable range, an appropriate remedial action must be taken.
30 Which approach would you prefer if you were a patient?? Imaging QC PrinciplesProactive QC rather than Reactive QCTest tool/phantomStandard imaging parameters/conditionsScheduled testing (Daily/Weekly)Defined and objective acceptance/rejection criteriaPatient replaces the phantomNon-standard imaging parameters/conditionsFrequent testing (every patient)Ill-defined and subjective acceptance/rejection criteriaSystem performance rated BEFORE clinical imagingSystem performance rated AFTER clinical imaging.The concept that I propose for the VCHA QC program is Proactive QC rather than Reactive QC.(READ SLIDE INFO)In my opinion, radiologists should not need to complain about image quality if the QC program is effective.Which approach would you prefer if you were a patient??
31 Radiographic Systems Projection radiography Film Digital detectors (DR)Computed radiography (CR)
32 Weekly Radiographic Tests Quality Control ProceduresFilmCRDRCommentsWeekly Quality Control TestsVisual Inspection of Imaging SystemsW1Inspect screens/CR plates/DR housingViewboxes ConditionW2Cleanliness, luminanceLaser Film Printer OperationW3Print pattern such as SMPTENormal Font – Required Test (“must do”)Italics - Recommended Test (“recommended”)Required Tests currently recommended by RPS
33 Monthly Radiographic Tests Quality Control ProceduresFilmCRDRCommentsMonthly Quality Control TestsCassette, Screen, and Imaging Plate CleaningM1Clean screens/CR plates/DR housingDarkroom Temperature and Humidity Conditions (DAP)M2Temp: 18-23C; Humidity 40-60%Darkroom Light ConditionsM3Visual check for light tightnessFilm Processor OperationM4Temp ± 0.5C; Developer and fixer correctRetake AnalysisM5For film, CR and DRElectronic Display Device PerformanceM6Display pattern such as SMPTE on all image display stationsLaser Film Printer OperationM7Print pattern such as SMPTECheck for 0/5% and 95/100% patch visibilityOD of 10% to 90% patchesNo artifacts or geometrical distortionNormal Font – Required Test (“must do”)Italics - Recommended Test (“recommended”)Required Tests currently recommended by RPS
34 Annual Radiographic Tests (1) Quality Control ProceduresFilmCRDRCommentsAnnual QC TestsSafelight TestY1Expose film for 2 mins in roomFilm/Screen ContactY2Image mesh and checkAccuracy of Loading FactorsY3mAs LinearityRadiation Output ReproducibilityY4ReproducibilityRadiation Output LinearityY5Output with mAsX-ray Beam FiltrationY6HVLAutomatic Exposure ControlY7Check AEC for all kVps and thicknessesX-ray Field and Light Field AlignmentY8Congruency of x-ray beam and light field edgesX-ray Beam CollimationY9Congruency of x-ray beam and light field centresNormal Font – Required Test (“must do”)Italics - Recommended Test (“recommended”)Required Tests currently recommended by RPS
35 Annual Radiographic Tests (2) Quality Control ProceduresFilmCRDRCommentsImage QualityGrid PerformanceY10Check uniformity and movement of gridExposure IndexY12Exposure Index versus Dose 1 to 50 mGyNoise, Uniformity and Image ArtifactsY14For above range of dose measure noise in center and each quadrantCheck for artifactsSpatial ResolutionY15Line-pair or Leeds phantomContrast DetectabilityY16Leeds phantomDigital Detector Residual ImagesY17Take image at 50 mGy then zero;check for artifactsPhantom Dose MeasurementsY18Measure dose at surface of standard phantom eg 20 cm PMMADAP MeterCalibrateNormal Font – Required Test (“must do”)Italics - Recommended Test (“recommended”)Required Tests currently recommended by RPS
36 Digital ImagingAny sufficiently advanced technology is indistinguishable from magic… Arthur C Clarke 1961
37 Digital X-ray Systems Direct Radiography DR Computed Radiography CR Formation of image without a secondary read-out deviceComputed Radiography CRUse of storage phosphor plate usually in a cassette-based system
38 Digital System QC - it is not performed magically Film DevelopedAndFixedDetectorReadingDigitalProcessingStoredPACSViewedDisplayQC of the digital systems is an additional requirement– in addition to the usual x-ray performance tests- it is not performed magically
39 DR, CR and DF – Extra QC Dose Calibration Spatial Resolution Low ContrastUniformityArtifactsThere are general QC tests that are performed on CR readers….Dose calibration, Resolution, Contrast, Uniformity, and Spatial Linearity.
40 Dose CalibrationEach system should be calibrated according to the manufacturers protocol, as they are all slightly differentGeneral set-upArrange for defined dose at surface of cassette at 80 kVpExpose and read imageRecord Exposure IndexThe image can also be used to check for uniformity, linearity and artifactsGenerally, this is the setup used for dose calibration.Erase cassette, place at certain distance from tube, use specific technique, read the cassette after a standard amount of time and record the Exposure Index.
41 Image QualityAll CR and some DR/DF manufacturers have custom Image Quality phantoms and automatic software to analyze image quality
42 Resolution and Contrast Any high contrast resolution phantom can be used to provide comparative informationLow contrast resolution is one of the most difficult parameters to measure. There are several phantoms and measurement is subjective, so consistent technique is essentialImage Noise is usually be a good indicator of consistencyA high contrast phantom can be used to ensure the information detail in an image remains constant over time. The phantom is placed on a cassette and exposed with a low technique.After reading the cassette/IP, the image is sent to PACS and the point at which 50% of either lines, bars or mesh are resolvable is determined to be the resolution limit.That should not change over the life of the equipment or between PM’s by more than +/- 20%.The phantom we manufactured can be used for this purpose.
43 Digital Radiography QC Many DR systems require more frequent calibration of the uniformity eg every monthFlat field measurement (uniform Cu orAl plate)Uniformity correctionNoiseArtifactsContrast-detail and resolution phantom
44 CR & DR QC Weekly visual inspection (W1) Dust / dirtClean if necessaryTechnologistCR and DR imaging systems must be inspected weekly for dust and dirt on or near the image reception area where they may negatively affect image quality.Technologists should be able to perform this task. For CR, it would involve carefully removing the imaging plate (with gloved hands) and looking for dust or dirt particulates and then removing them according to manufacturer instructions. For DR, it may mean removing contrast or markers from the imaging surface.The monthly inspection and cleaning of CR cassettes, screens, and imaging plates should also be a task that technologists can perform.Monthly inspection / cleaning (M1)Dust / dirt / damageClean each IP. Replace damaged IPs.TechnologistMaintain logsheet
45 CR QCWe use a logsheet to document the condition of each cassette and imaging plate.