Quality Assurance and Quality Control of Film Screen Mammography. Xuan Ho, Ph.D., R.T. (R)

Transcription

1 Quality Assurance and Quality Control of Film Screen Mammography Xuan Ho, Ph.D., R.T. (R)

2 Quality Assurance & Quality Control Quality Assurance Procedures Daily Weekly Monthly Quarterly Semiannual Annual

3 MAMMOGRAPHIC QC TESTS Darkroom cleanliness Daily Processor quality control Daily Mobile unit quality control Daily Screen cleanliness Weekly Viewboxes & viewing conditions Weekly Phantom images Weekly Visual checklist Monthly Repeat analysis Quarterly Analysis of fixer retention in film Quarterly Darkroom fog Semi-annually Screen-film contact Semi-annually Compression Semi-annually

4 Daily Quality Assurance Procedures Darkroom Processor

5 Daily Quality Assurance Procedures Darkroom The purpose of quality assurance for the darkroom, is to assure the cleanliness of it, the darkness (no light leaks), and the brightness of the red light. According to ACR regulations the darkroom is to cleaned each day. The darkroom needs to be free of dust and dirt. Any ventilation in to the room, can not be directly over the countertop. There should not be any storage above the countertop, and there should be no eating, drinking or smoking in this room.

6 Daily Quality Assurance Procedures Processor The purpose of quality assurance on the mammography processor, is to assure that the processor and chemistry system are working in a consistent manner. A specific box of mammography film, and cassette are dedicated to test the daily Q.A. of the processor. A sensitometer is used to expose film with different levels of densities, on the Q.A. film. A densitometer is used to read the levels of density on the film, after the film has been developed through the processor. This indicates whether the chemicals are in balance with the film.

7 Daily Quality Assurance Procedures Sensitometer

8 Daily Quality Assurance Procedures Densitometer

9 Daily Quality Assurance Procedures Processor (continued) When reading the sensitometric strip on the Q.A. film, there are three dedicated steps on the strip that are read each day. Depending on the facility, these steps can vary. There are low, medium and high density steps to be read. The low-density (LD) is subtracted from the high-density (HD), giving what is called the density difference (DD), or contrast.

10 Daily Quality Assurance Procedures Processor (continued) There is also a mid-density (MD) read, giving what is called the speed of the film. There is also one more measurement made, and that is the base-plus-fog. This is read on the clear portion of the Q.A. film.

11 Daily Quality Assurance Procedures Sensitometric Strip

12 Daily Quality Assurance Procedures Processor (continued) Corrective measures can be taken if the speed and density-difference are not with in limits. If the contrast of the film is too high, starter can be added to the developer, to bring it down. If the temperature of the processor is high, make sure the water has been turned on. If the temperature is too low, then service needs to be called, to change the parameters.

13 Daily Quality Assurance Procedures Processor (continued) If the speed of the film is off, make sure the processing time has not changed. Last, but not least, make sure the box of dedicated Q.A. film has not changed.

14 Weekly Quality Assurance Procedures Screen cleanliness Viewbox maintenance Phantom images

15 Weekly Quality Assurance Procedures Screen cleanliness is done on a weekly basis. Darkrooms processors, and manipulation of cassettes help contaminate mammography screens. This is to assure that mammographic screens are free of dust and dirt particles that may degrade image quality or mimic microcalcifications.

16 Weekly Quality Assurance Procedures To clean screens, chose a clean location. Check screens for dirt, dust, lint, pencil marks, fingernail polish and other marks under a bright light. Cleans screens using manufacturer s recommended materials and procedures. After cleaning with liquid cleaners, screens should be allowed to air dry by standing cassettes vertically, on edge, and partially open.

17 Weekly Quality Assurance Procedures Cleaning Screens (continued) Inspect the screen and cassette cover for any stray particles of dust before reloading the cassette with film. Wait at least 15 minutes or manufacturer s recommendation time after loading and before using. Be sure to document on the Q.A. log sheet that this weekly task has been performed. (Date & Tech initials)

18 Weekly Quality Assurance Procedures View Box Maintenance According to ACR regulations this is done to assure that the viewboxes and viewing conditions are optimized and maintained at an optimal level. This should be carried out weekly.

19 Weekly Quality Assurance Procedures View Box Maintenance (continued) To do so, clean view box surfaces using window cleaner and soft paper towels (magnifiers should be cleaned at the same time). Visually inspect the view boxes for uniformity and luminance. Assure that all view box masking equipment is functioning properly and easily. Visually check the room illumination levels and assure that sources of bright light are not present in the room and are not being reflected from the view box surface. Be sure to document the date and tech initials, when this procedure has been done.

20 Weekly Quality Assurance Procedures Phantom images This weekly task is performed to assure that film optical density, contrast (density difference), uniformity, and image quality due to the X-ray imaging system and film processor are maintained at optimum levels. The mammographic phantom is equivalent to a 4.2cm thick compressed breast consisting of 50% glandular and 50% adipose tissue.

21 Weekly Quality Assurance Phantom images Procedures It is important to use the same cassette each time this test is done. It is also important to use the #2 photocell on the image receptor, the same view box, same technologists eyes and same technical factors, each time. This keeps all factors consistent.

22 Weekly Quality Assurance Procedures Optical disc This is a mammography phantom, with the optical disc sitting on top of it.

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24 Weekly Quality Assurance Phantom (continued) When the designated cassette is loaded, place the phantom (with the disc on a place not obscuring the fibers, masses or specks), on the image receptor, flush with the chest wall edge of the bucky, and center it. Bring the compression paddle down, to touch the top of the phantom disc. Make an exposure and develop the film. Make sure to note the technique used.

25 Weekly Quality Assurance Phantom (continued) After the film is developed, use the sensitometer to measure the background optical density (the disc) and the density difference, by measuring right next to the disc. Subtract the optical density from the density just to the left or right of the disc. This gives the density difference.

26 Weekly Quality Assurance Phantom images (continued) Plot the mas, optical density (disc), and the DD (area measured next to the disc). Next, the technologist will then view the number of fibers, masses and specks seen on the phantom and document them on the control chart. This should be done under optimal viewing conditions.

27 Weekly Quality Assurance Phantom images (continued) When scoring the image, it is important to note that the largest whole mass, fiber or group of specks should be viewed first, and given a value of 1. If they are seen, but partially seen, they are given a value of.5. If less than half of the item is seen, then a value of 0 is given and documented. A minimum of 4 fibers, 3 speck groups and 3 masses must be seen, to pass.

28 Monthly Quality Assurance Procedures Visual checklist This is done on a monthly basis to assure that mammographic X-ray system indicator lights, displays, mechanical locks and detents are working properly and that the mechanical rigidity and stability of the equipment is optimum. To do this procedure, review all of the items listed on the visual checklist and indicate the status. Be sure to rotate the C-arm the way you would for patient imaging. Date and initial the checklist where indicated.

29 Quarterly Quality Assurance Procedures Repeat Analysis Fixer Retention Test

30 Quarterly Quality Assurance Repeat analysis Procedures This test is performed quarterly (every three months) to determine the number and cause of repeated mammograms and rejected films. Analysis of these data will help identify ways to improve efficiency and reduce costs as well as patient exposures. Start by disposing of all existing rejected films in the department.

31 Quarterly Quality Assurance Procedures Repeat analysis (continued) Take inventory of film supply as a starting point to determine total number of films consumed during this test. Start to collect all rejected films into the categories on the repeat-reject analysis sheet used for the test.

32 Quarterly Quality Assurance Procedures Repeat analysis (continued) Films may be repeated for a number of reasons including poor positioning, patient motion, being too light or dark, or artifacts. Some films may not have resulted in additional exposure to the patient, but may have been rejected. (clear films or Q.C. films) Although it is important to include wire localization films as part of the reject analysis, they should not be included in the repeat analysis because they are taken as part of the wire localization process. Tabulate the counts and determine the total number of repeated films, rejected films, and the total number exposed.

33 Quarterly Quality Assurance Procedures Repeat Analysis (continued) Determine the overall percentage of repeated/rejected films by dividing the total number of repeated films by the total number of exposed during the analysis period, and multiply by 100. Document this number on the analysis sheet. Determine the percentage of repeats in each reason for repeat category by dividing the repeats in the category by the total number of repeated films and multiply by 100. Document this number on the analysis sheet.

34 Quarterly Quality Assurance Procedures Repeat Analysis (continued) MQSA requirements for repeat analysis say the repeat/reject rates can not rate by more than 2%. If they are, corrective action must take place.

35 Quarterly Quality Assurance Procedures Repeat analysis documentation form.

36 Quarterly Quality Assurance Procedures Fixer Retention Test This test is done quarterly to determine the quantity of residual fixer (hypo) in processed film as an indicator of keeping quality. Residual hypo indicated insufficient washing and considerably degrades image stability.

37 Quarterly Quality Assurance Procedures Fixer retention kit

38 Quarterly Quality Assurance Procedures Fixer Retention test (continued) To do this test, a hypo estimator and a hypo test solution are needed. First process one sheet of unexposed film in the mammography processor. Place one drop of the hypo test solution on the emulsion (less shiny) side of the film. Allow the solution to stand for 2 minutes. Blot off the excess solution. Place the film on a sheet of white paper.

39 Quarterly Quality Assurance Procedures Fixer Retention test (continued) Compare the stain with a hypo estimator strip by looking at the radiographic film on a sheet of white paper. The comparison should be made with the estimator over the film sample to help compensate for differences in the color of the base of the film and the hypo estimator strip in its sleeve for protection. Record the results on the monthly, quarterly and semiannual checklist

40 Semiannual Quarterly Assurance Procedures Darkroom Fog test Film-screen Contact test Compression test

41 Semiannual Quarterly Assurance Procedures Darkroom fog test This test is done to assure the darkroom safelights and other light sources inside and outside of the darkroom do not fog mammographic films. To perform this test, a mammographic phantom, densitometer, mammographic film, one sheet of each type of film used for mammography in the darkroom (from a new box), an opaque card, and a watch or timer are needed.

42 Semiannual Quality Assurance Procedures Darkroom fog test continued First assure that all safelight filters are those specified by the film manufacturer, and do not appear faded or cracked. Also assure that the wattage and type of the light bulbs and the distance from the safelights to the film-handling surface are those specified by the film manufacturer. Turn out all lights in the darkroom and wait 5 minutes for the eyes to adjust. Look for obvious light leaks around doors, around passbox and processor, and in the ceiling. Light leaks may be quite directional. Be careful in moving around a darkroom without safelight illumination.

43 Semiannual Quality Assurance Procedures Darkroom Fog Test (continued) In total darkness, load a new sheet of film into the cassette, and X-ray a phantom (like normal procedures). In total darkness, remove the exposed film from the cassette and place it on the countertop, emulsion side up. Cover one half of the film with an opaque sheet, set perpendicular to the chest wall edge of the film. Be sure the opaque card is in contact with the film, so no light leaks.

44 Semiannual Quality Assurance Procedures Darkroom fog test (continued) Turn on the safelight and let the film and opaque card lie on the countertop for 2 minutes. Process the film. Using the densitometer, measure the the density of the unfogged portion of the image. Then measure the density of the fogged portion of the image. To determine the amount of fog, subtract the unfogged value from the fogged value. Record this optical density difference on the monthly, quarterly, semiannual checklist. MQSA standards indicate that darkroom fog shall not exceed 0.05.

45 Semiannual Quality Assurance Procedures Film-screen contact test This test is done semiannually to assure that optimum contact is maintained between the screen and film in each cassette. In order to do this test a copper screen, 40 mesh (40 wires per inch), mammographic film of appropriate size, a densitometer, a sensitometer, screens and cassettes to be tested. First, all the cassettes to be tested must be cleaned. Afterwards, load film and let the air out of the cassettes by waiting at least 15 minutes before proceeding.

46 Semiannual Quality Assurance Procedures Film-screen contact test tool

47 Semiannual Quality Assurance Procedures Film-screen contact test (continued) Place the cassette to be tested on top of the imaging receptor, with the edge of the cassette flush with the chest-wall edge of the image receptor. Place the copper screen on top of the cassette. Place the compression paddle as high towards the X-ray tube as possible.

48 Semiannual Quality Assurance Procedures Film-screen contact test (continued) Select a manual technique (25 to 28kVp) that will provide a film density between 0.70 and 0.80 when measured in the image over the mesh near the chest-wall edge.

49 Semiannual Quality Assurance Procedures Film-screen contact test tool on top of the image receptor, with the compression paddle all the way up.

50 Semiannual Quality Assurance Procedures Film-screen contact test (continued) Expose and process the film. Repeat this process for each cassette. View the films on a viewbox at a distance of at least 3 feet. Look for areas of poor contact, i.e. darker areas in the mesh image. The cassettes that pass can be placed into clinical use.

51 Semiannual Quality Assurance Procedures Film-screen contact test (continued) Select those cassettes that did not pass and repeat the above process of cleaning etc. Those that do not pass, can not be used. MQSA requires a 40 mesh copper screen. All cassettes being used, need to be tested every six months.

52 Semiannual Quality Assurance Procedures Compression test This test is performed semiannually to assure that the mammography system can provide adequate compression in the manual and powered mode and that the equipment does not allow too much compression to be applied. Adequate compression is essential for high-quality mammography. Compression reduces the thickness of tissue that must be penetrated by radiation, thereby reducing scattered radiation and increasing contrast, while reducing radiation exposure to the breast. For this test a flat analog type bathroom scale and several towels or a sponge are needed.

53 Semiannual Quality Assurance Procedures

54 Semiannual Quality Assurance Procedures Compression test (continued) To do this test in power mode, place a towel on the cassette holder then place the bathroom scale on the towel with the dial and read-out positioned for easy reading. Locate the center of the scale directly under the compression device. Place more towels, or sponges on top of the scale for protection. Using the initial power drive, activate the compression device and allow it to operate until it stops automatically. Read and record the compression force on the monthly, quarterly and semiannual checklist.

55 Semiannual Quality Assurance Procedures Compression test (continued) Release the compression device. For manual mode, move the compression device downward until it stops, manually. Read and record the compression force on the monthly, quarterly and semiannual checklist. Release the compression device. MQSA requirements state that a compression force of at least 111 newtons (25 pounds) shall be provided. The maximum compression force for the initial power drive must be between 111 newtons (25 pounds) and 200 newtons (45 pounds). If the compression test fails, the mammography unit shall not be used until the problem has been corrected.

56 Annual Quality Assurance Procedures Physicist s survey Inspection by federally certified or state-certified inspectors Qualification standards

57 Annual Quality Assurance Procedures Physicist s survey is done once per year. A licensed physicist is required to test the mammography equipment at a minimum of once per calendar year. The physicist records and prepares a report of the findings, according to MQSA regulations. A copy of this document is kept with all of the quality assurance/control records, for inspection.

58 Annual Quality Assurance Procedures Inspection by federally certified or statecertified inspectors: This is done once per calendar year. The inspector reviews all records of Q.A. tests done through out the year, and certification and continuing education of personnel (mammographers and radiologists). If any of the tests are not in compliance with MQSA requirements, the facility will lose it s license to perform mammography procedures. If any personnel are not current with continuing education or licensure, they can not perform mammography until corrected.

59 Annual Quality Assurance Procedures Qualification standards MQSA specifies that a lead interpreting physician be identified by the mammography facility to have the general responsibilities of ensuring that all MQSA-required activities are met. This individual will most likely be the lead mammography radiologist. All radiologists must be compliant in their training in mammography and continuing education, in order to interpret mammograms.

60 Annual Quality Assurance Procedures Mammographers According to the ARRT, a licensed mammographer must complete a minimum of 12 continuing education units on a biennium basis. For the state of California, the continuing education requirement is 15 ceu s per every three years. Each state varies with their requirements. In order to stay current in mammography, a technologist must perform 100 mammograms each year, according to the ARRT.

61 Annual Quality Assurance Procedures Medical physicists The medical physicist must under go extensive education and licensure. He must be current in his education and licensure in order to be compliant with MQSA requirements.