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Safety Code 35 John Aldrich PhD FCCPM Regional Leader Clinical Physics

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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 RTNM QC Coordinator Department of Radiology Vancouver Coastal Health University 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 equipment Only film processor QC defined Safety 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 systems Increased emphasis on patient dose 25% 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 RPS Handout includes all slides in our presentations Attached sheets have all the tables enlarged References are to details of the tests in the Code eg 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 Protection 10 Questions Radiography (Film/DR/CR) Radioscopy (Fluoroscopy, Angio, DF) LUNCH

6 Overview Session 2 After Lunch
CT 20 Equipment Purchase/ Acceptance Testing 15 Patient dose Questions 10 Personnel qualifications Education and training

7 Daily Quality Control Tests
Normal Font – Required Test (“must do”) Italics - Recommended Test (“recommended”) Required Tests currently recommended by RPS Quality Control Procedures Film-based All Systems Daily Quality Control Tests Equipment Warm-up (D1) According to manufacturers instructions Can include auto calibration eg CT Meters Operation (D2) Meter, visible and audible indicators should function Equipment Conditions (D3) Visual inspection for loose or broken components, ease of movements Darkroom 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’ workstations Check 5% and 95% areas visible

8 Weekly and Monthly Tests
Quality Control Procedures All Systems Weekly Quality Control Tests Viewbox condition (W2) Visual inspection for cleanliness, colour, illumination Laser Film Printer Operation (W3) Print pattern such as SMPTE or PQC Check for 0/5% and 95/100% patch visibility OD of 10% to 90% patches No artifacts or geometrical distortion Monthly Quality Control Tests Darkroom Temperature and Humidity (M2) Temp: 18-23C; Humidity 40-60% Darkroom Light Conditions (M3) Visual check for light tightness Film 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 devices Laser Film Printer Operation (M7) As W3 plus measurement of optical density of the 10% to 90% grey scale Normal Font – Required Test (“must do”) Italics - Recommended Test (“recommended”) Required Tests currently recommended by RPS

9 Quarterly and Annual Tests
Quality Control Procedures All Systems Quarterly Quality Control Tests Interlocks (Q2) These are not usually used on diagnostic doors Annual Quality Control Tests Safelight Test (Y1) Expose film for 2 min Film/Screen Contact (Y2) Image mesh and check Viewboxes (Y26) Check luminance, uniformity, homogeneity, ambient light Electronic Display Device Performance (Y27) All clinical workstations must be calibrated for luminance, distortion, resolution and noise Integrity of Protective Equipment (Y28) Lead aprons, glasses, integral shields General Preventive Maintenance (Y29) As per manufacturer Normal 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 login Find suitable SMPTE test pattern Make accessible on PACS Test using various user logins/profiles Alert radiologists of requirement, frequency, and procedure In 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 visible Right Display – 5% not visible / 95 % visible On 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
Technologist PACS administrator Biomed SMPTE test pattern / test pattern generator / vendor The 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 use QC Coordinator PACS administrator Biomed SMPTE test pattern / test pattern generator / vendor QC software and photometer For 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 discolouration Improper luminance Clean, replace plastic or bulb if necessary Technologists / Biomed / Plant services A 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 logsheet Luminance > 2500 cd/m2 Should Light output uniformity +/- 10% Light output homogeneity +/- 20% Ambient light control < 50 lux (50 cd/m2) 5-10 lux recommended (5-10 cd/m2) Must Depending 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 QC It 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 menu View 5% and 95% grayscale squares Maintain logsheet Weekly 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 QC They 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 menu Measure optical density of grayscale gradient squares, geometrical distortions, artifacts View 5% and 95% squares and compare densitometer readings Maintain logsheet The 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 QC I 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 Protection 10 Questions Radiography DR/CR Radioscopy (Fluoroscopy, Angio), DF LUNCH

22 Radiation Protection Radiation Safety Officer (1.4)
Room Shielding (5.0) Lead aprons (4.1)

23 Radiation Safety Officer
There must be a Medical Physicist or Radiation Safety Officer to advise on all aspects of Radiation Safety Planning, registration, inspection Working conditions, procedures Classification of personnel, dosimetry Record keeping, investigations

24 Radiation Protection - Shielding
Design of Shielding Recommend 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 shielding Check lead installation Measure radiation in surrounding areas

25 Lead equivalence of aprons
Lead Aprons Lead equivalence of aprons SC 20A <150 kVp 0.5 mm SC 35 < 100 kVp: mm 100< kVp <150: mm >150 kVp: mm

26 Lead apron QC Annually (Y28) Radiographic / radioscopic
Rejection if total defective area > 670 mm2 Thyroid and reproductive areas < 5 mm diameter equivalent total Until 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 Protection 10 Questions Radiography DR/CR Radioscopy (Fluoroscopy, Angio), DF LUNCH

28 Overview Session 1 Requirements for all systems 20
Radiation Protection 10 Questions Radiography DR/CR Radioscopy (Fluoroscopy, Angio), DF LUNCH

29 Baseline value determination Next constancy testing
Equipment Life Cycle Acceptance testing New equipment Conformance to manufacturer’s specifications/RFP Baseline performance Routine performance evaluations Specific tests performed at regular intervals Consistency checks Evaluate malfunctioning or out-of-spec equipment Baseline value determination Device use period Next constancy testing Data evaluation Within the established criteria Remedy Acceptance testing FAIL PASS There 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 Principles Proactive QC rather than Reactive QC Test tool/phantom Standard imaging parameters/conditions Scheduled testing (Daily/Weekly) Defined and objective acceptance/rejection criteria Patient replaces the phantom Non-standard imaging parameters/conditions Frequent testing (every patient) Ill-defined and subjective acceptance/rejection criteria System performance rated BEFORE clinical imaging System 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 Procedures Film CR DR Comments Weekly Quality Control Tests Visual Inspection of Imaging Systems W1 Inspect screens/CR plates/DR housing Viewboxes Condition W2 Cleanliness, luminance Laser Film Printer Operation W3 Print pattern such as SMPTE Normal Font – Required Test (“must do”) Italics - Recommended Test (“recommended”) Required Tests currently recommended by RPS

33 Monthly Radiographic Tests
Quality Control Procedures Film CR DR Comments Monthly Quality Control Tests Cassette, Screen, and Imaging Plate Cleaning M1 Clean screens/CR plates/DR housing Darkroom Temperature and Humidity Conditions (DAP) M2 Temp: 18-23C; Humidity 40-60% Darkroom Light Conditions M3 Visual check for light tightness Film Processor Operation M4 Temp ± 0.5C; Developer and fixer correct Retake Analysis M5 For film, CR and DR Electronic Display Device Performance M6 Display pattern such as SMPTE on all image display stations Laser Film Printer Operation M7 Print pattern such as SMPTE Check for 0/5% and 95/100% patch visibility OD of 10% to 90% patches No artifacts or geometrical distortion Normal Font – Required Test (“must do”) Italics - Recommended Test (“recommended”) Required Tests currently recommended by RPS

34 Annual Radiographic Tests (1)
Quality Control Procedures Film CR DR Comments Annual QC Tests Safelight Test Y1 Expose film for 2 mins in room Film/Screen Contact Y2 Image mesh and check Accuracy of Loading Factors Y3 mAs Linearity Radiation Output Reproducibility Y4 Reproducibility Radiation Output Linearity Y5 Output with mAs X-ray Beam Filtration Y6 HVL Automatic Exposure Control Y7 Check AEC for all kVps and thicknesses X-ray Field and Light Field Alignment Y8 Congruency of x-ray beam and light field edges X-ray Beam Collimation Y9 Congruency of x-ray beam and light field centres Normal Font – Required Test (“must do”) Italics - Recommended Test (“recommended”) Required Tests currently recommended by RPS

35 Annual Radiographic Tests (2)
Quality Control Procedures Film CR DR Comments Image Quality Grid Performance Y10 Check uniformity and movement of grid Exposure Index Y12 Exposure Index versus Dose 1 to 50 mGy Noise, Uniformity and Image Artifacts Y14 For above range of dose measure noise in center and each quadrant Check for artifacts Spatial Resolution Y15 Line-pair or Leeds phantom Contrast Detectability Y16 Leeds phantom Digital Detector Residual Images Y17 Take image at 50 mGy then zero; check for artifacts Phantom Dose Measurements Y18 Measure dose at surface of standard phantom eg 20 cm PMMA DAP Meter Calibrate Normal Font – Required Test (“must do”) Italics - Recommended Test (“recommended”) Required Tests currently recommended by RPS

36 Digital Imaging Any 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 device Computed Radiography CR Use of storage phosphor plate usually in a cassette-based system

38 Digital System QC - it is not performed magically Film
Developed And Fixed Detector Reading Digital Processing Stored PACS Viewed Display QC 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 Contrast Uniformity Artifacts There are general QC tests that are performed on CR readers….Dose calibration, Resolution, Contrast, Uniformity, and Spatial Linearity.

40 Dose Calibration Each system should be calibrated according to the manufacturers protocol, as they are all slightly different General set-up Arrange for defined dose at surface of cassette at 80 kVp Expose and read image Record Exposure Index The image can also be used to check for uniformity, linearity and artifacts Generally, 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 Quality All 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 information Low contrast resolution is one of the most difficult parameters to measure. There are several phantoms and measurement is subjective, so consistent technique is essential Image Noise is usually be a good indicator of consistency A 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 month Flat field measurement (uniform Cu orAl plate) Uniformity correction Noise Artifacts Contrast-detail and resolution phantom

44 CR & DR QC Weekly visual inspection (W1)
Dust / dirt Clean if necessary Technologist CR 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 / damage Clean each IP. Replace damaged IPs. Technologist Maintain logsheet

45 CR QC We use a logsheet to document the condition of each cassette and imaging plate.


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