Update on ACR Digital Mammography QC Manual

Transcription

1 Update on ACR Digital Mammography QC Manual Priscilla F. Butler, M.S. Medical Physicist and Senior Director, ACR, Reston, VA (with thanks to Eric Berns, Ph.D.) Overview Phantom Specifications QC Manual Explain what we feel is important Thank you for being here today 1

2 Digital Mammography in the US (as of 3/1/15) 13,493 units at 8720 facilities Over 96% of all units in US are FFDM *4 accrediting bodies *Over 30 models and mfrs approved by FDA 2

3 Quality Control: What It and Why Is It Important? Primary Purpose Reduce exposure to patients and personnel Ensure adequate and consistent patient image quality Detect and correct for potential problems, before they impact patient image quality and care What it s not: Not a detailed technical evaluation of a unit Not a detailed measure of a limits of a unit Not the optimization of a unit QC Mandates MQSA Mammography Quality Standards Act ACR American College of Radiology 3

4 FDA s Current DM QC Requirements Follow latest version of mfr s QC manual procedures for unit tested Lorad (Hologic) allows facility to follow any of their manuals Meet mfr s performance standards Failures must be fixed before use on patients Most mfrs applied for alternative standards to allow 30 days for some QC tests ACR s Current DM QC Requirements Same as FDA s Which are the same as the manufacturer s ACR suggests using manufacturer s data forms 4

5 Screen-Film QC Single detector technology Single processing technology First QC manual in 1990 Manufacturer s DM QC Requirements Tests vary for each manufacturer and model Some tests same but names different Some tests not required by some manufacturers Frequencies vary for each manufacturer and model Procedures vary for each manufacturer and model Pass/fail criteria vary for each manufacturer and model 5

6 Film Printers FDA recommends only using printers cleared by FDA s Office of Device Evaluation for FFDM (but may legally use others) Facility must have access to a laser printer (either on-site or someplace else) Printer must exist and be tested by MP before the facility performs mammography Monitors and Workstations FDA regs require facilities to comply with a QA program substantially the same as that of FFDM mfr (i.e., GE, Lorad, etc.) Impractical; even impossible since tests are softwarebased FDA says If the monitor/workstation has been cleared by FDA s ODE for FFDM, the monitor s QC manual is substantially the same and OK to follow If monitor was not cleared by FDA ODE for FFDM facilities must follow one by FFDM mfr FDA ODE clears monitors/workstations Over 500 total;? have been cleared for FFDM 6

7 ACR DM QC Manual VS. All of the above may vary with QC manual revisions of same manufacturer/model ACR DM QC Manual Project Subcommittee on Quality Assurance Chair Eric Berns, PhD University of Colorado Subcommittee all volunteers (with day jobs) Clinical representatives MITA representatives (equipment and phantom manufacturers) 7

8 ACR DM QC Manual Project Subcommittee Charge: Design ACR Accreditation Phantom for FFDM Write QC Manual for ACR FFDM Mammography Accreditation Program Subcommittee Goals: Standardize all QC tests for all digital manufacturers Standardize test frequencies Standardize performance criteria ACR DM QC Manual Project QC tests: Will apply to all manufacturers Tests come from a variety of sources (MQSA, SFM, ACRIN DMIST, Manufacturer s QC programs, MITA, subcommittee clinical experience, etc.) Clinically relevant User friendly Eliminate non-productive testing Just because you can test something, doesn t mean you should! 8

9 ACR Digital QC Manual - Structure Radiologist s Section Radiologic Technologist s Section Medical Physicist s Section Appendices **Clinical Image Quality Section (w/patient Positioning and Compression and Clinical Image Quality Evaluation) will be revised at a later date and posted on ACR website ACR Digital QC Manual - Tools Will be downloadable to computer or tablet Future revisions fully described (in new Revisions section) Sections and references fully linked Optional procedures and forms available Management forms available to aid organization Procedures liberally illustrated Forms in PDF and Excel formats Excel formats contain formula and functionality Excel forms downloadable from ACR website 9

10 ACR DM QC Manual Project Subcommittee Goals: Standardize all QC tests for all digital Mfrs Standardize test frequencies Standardize performance criteria What Will Be New? 10

11 The ACR DM Phantom Prototype Phantom Prototype Design Principles 11

12 Phantom Prototype Design Principles Phantom Prototype Design Principles Based on existing ACR Accreditation Phantom Similar imaging and scoring to current phantom Build on experience of QC techs and physicists at ~8,700 US facilities who already know how to use and score the existing phantom (~25,000+ techs) 12

13 Phantom Prototype Design Principles Can be used on both SFM & FFDM Total attenuation matched to current SFM phantom Similar thickness Similar total dose Permits testing of the MQSA 3.0 mgy dose limit (single CC view) Proposed Scoring Changes Eliminate subtraction for artifacts Add Fail for artifacts New pass/fail criteria from 4,3,3 To: 2,3,2 **But, objects are the same (effective) size as SFM Phantom 13

14 ACR Phantom Prototype Depth of CNR Cavity = cm Air Gap = cm Nominal Tolerances (Insert Well & CNR Cavity) Wax insert well depth : cm (+ 2 mils). Wax insert well width and length : / cm. CNR cavity depth : cm (+ 2 mils). CNR diameter : cm. Cover =Nominal 0.3 cm Total Thickness = cm Wax = 0.70 cm cm Compensator = cm Total Insert Depth = 0.75 cm Total Thickness Under Insert = 3.05 cm Test object distance from base of wax = cm cm cm Centered Left to Right CNR Cavity ( cm Deep) 9.5 cm cm cm Milled out wax insert area 13.0 cm (+0.04, cm) ID Tag Milled out wax insert area 7.0 cm (+0.04, cm) cm cm cm Screws Wax Insert Specifications with Virtual Placement Grid ID Tag Specs cm (+ 0.00, cm) 1.5 cm Virtual Box: height = 0.5 cm, length = 1.8 cm Location of Virtual Box ID Tag 0.49 cm 2.0 cm 6.98 cm (+ 0.00, cm) 2.0 cm 2.0 cm 0.49 cm 0.49 cm 2.0 cm each 0.49 cm Notes: Test objects to be centered on their respective placement grid locations cm perimeter around test object placement grid cm (1/4 inch) radius on corners of wax insert. Fiber Placement specs Fiber specifications Fiber Fiber Fiber Length = 1.0 cm cm Fiber Diameter = See Table 45 o + 5 o 45 o + 5 o Speck Placement & Specs 1. Specks to be placed at points on star and middle of star 2. Speck Size (spherical) = See Table 3. Center speck placement to be within cm of center of virtual grid 4. Distance from center speck to center of speck on perimeter = 0.5 cm cm Mass Placement & Specs 1. Mass pre-cut sphere diameter = 5/8 inch 2. Mass placement to be within cm of center of virtual grid 14

15 Wax Insert Test Object Specifications Test Object Fiber Diameter Speck Diameter (Glass Spheres) Mass Thickness mm mm mm Summary of Test Object Visual Equivalency Test Object Fibers (mm) Specks (mm) Masses (mm) ACR 156 FFDM ACR 156 FFDM ACR 156 FFDM

16 Pass/Fail Criteria Test Object Fibers (mm) Specks (mm) Masses (mm) ACR 156 FFDM ACR 156 FFDM ACR 156 FFDM Fail Pass The ACR DM Phantom Prototype 16

17 Image of Entire Phantom Serial Number *Note: Gray dot in lower left corner of wax insert is an artifact due to a bubble in wax insert. Wax Insert Serial Number 17

18 Expanded View of Wax Insert Pass Criteria: Equivalent to SFM Phantom: 2 Fibers, 3 Specks, 2 Masses 4 Fibers, 3 Specks, 3 Masses Pass Serial Number 18

19 Effects of Thickness Equalization Serial Number New FFDM phantom equalizes attenuation inside and outside wax insert. This permits evaluation of artifacts over entire phantom area with same WW and WL used to score test objects. Benefits of Prototype Phantom Design Provides view of entire detector artifact evaluation W/L optimized for test objects optimizes for artifact evaluation Finer gradations and smaller sizes of test objects AGD measurement & limit same as SFM meets MQSA Provides single image/exposure for evaluation(s) Minimal training Provides basis for monitor and printer QC ACR Physics Reviewers Can see scores and artifacts on single submitted film (or image) Do not need different WW/WL settings 19

20 Technologist Section 20

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27 Also: Tally sheet Daily Counting Sheet 27

28 Technologist Management Forms 28

29 ACR Technique and Procedure Summaries (continued) Facility MAP ID-Unit# ( ) AW & RW Monitor QC Room ID Unit Mfr & Model ACR Technique and Procedure Summaries (continued) Procedure: Display the AAPM TG 18-QC or SMPTE test pattern. (Another pattern that allows relevant measurements may also be used.) Check the monitor screens to verify they are clean. Facility Room ID Verify that 0%-5% and 95%-100% boxes are visible (red circles). Verify that line-pair images are sharp and distinguishable (red rectangles). MAP ID-Unit# ( ) Unit Mfr & Model Score the ACR DM Phantom & evaluate for artifacts (RW only). If applicable, perform monitor calibration tests per manufacturer's recommendations. Film Printer QC Monitor manufacturer instructions for finding & viewing TG 18-QC test pattern: Procedure: Required equipment - ACR DM Phantom image and densitometer Print image acquired in "ACR DM Phantom Image Quality" test. Print from workstation/computer/pacs used for printing most clinical films. Do not adjust window and level settings prior to printing. Evaluate the phantom for artifacts & score. Note: If possible, print phantom image from same x-ray unit each time for this test. Note: Use film size most commonly used for mammography. Note: For each printer, only print a single image from a single x-ray unit or workstation. SMPTE Test Pattern TG 18-QC Test Pattern Film Printer Setup Date: Film Size (8 x 10 or 10 x 12): ID of x-ray unit or workstation for printed phantom: Dmax Note: Dmax to be measured on perimeter of film. If not available, print a clinical image and measure in the non-breast area. Background OD Cavity OD Dmax SN

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32 Medical Physicist Section 32

33 2. ACR DM Phantom Image Quality Facility Name Imaging Facility Room ID, Mfr & Model ACR DM Phantom Mfr and S/N Phantom Mfr 1234 MAP ID-Unit# ( ) SID (cm) 70 Survey Date Room 1, Unit Mfr, Unit Model xx December 1, 2015 Equipment: ACR DM Phantom (required) Phantom Setup: AEC mode: Follow procedure in the Technologist's ACR Technique & Procedure Summaries: Use clinical technique for typical screening exam of 4.2 cm 50/50 breast Largest IR & paddle, 5 dan or 12 lbs, Score on AW Phantom Setup Adjust W/L to optimize test objects, zoom & pan entire image For Config 2 & 3 using kvp & mas closest to phantom techniques Paddle size (IR size): Paddle type (reg or flex): View or selected image: Compression force: AEC cell position (if avail): Phantom patient name: Target/filter (if app): kvp (if app): Phantom patient ID: Image sent to which PACS? Density setting (if app): Mag factor (mag mode only): Contact Mode Clinical - Manual - Manual - ACR DM Target/Filter Target/Filter Phantom Config 2 Config 3 Clinical - ACR DM Phantom Mag Mode Manual - Manual - Target/Filter Target/Filter Config 2 Config 3 Target/filter Resulting Techniques (if available) Image receptor size kvp mas largest Unit-indicated AGD (mgy) ACR DM Phantom Evaluation Artifacts P/F Fiber score Speck group score Mass score Phantom P/F DC offset (if applicable) Mean cavity signal SNR & CNR Raw Image Mean background signal Std dev of background Calculated SNR Calculated CNR #DIV/0! #DIV/0! SNR 40.0 (P/F) CNR 2.0 (P/F) Distance Measurement Parallel to A-C axis (mm) Meas = 70.0 ±14.0 mm (P/F) Analysis Fibers Full Point 8 mm long Overall Pass/Fail Initiated (or updated) technologist's ACR Technique and Procedure Summaries form Half Point 5 & <8 mm Specks Masses 4-6 specks ¾ border 2-3 specks ½ & < ¾ border Distance Required: ACR DM Phantom image must be free of clinically significant artifacts. Fiber score must be 2.0;; speck group score must be 3.0;; mass score must be 2.0. Action Limits SNR must be 40.0;; CNR must be 2.0;; measured wax insert distance must be 70.0 ± 14.0 mm. Timeframe: Failures of required items must be corrected before clinical use. 33

34 CNR Mean = Mean = St. Dev = 7.8 Serial Number 34

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36 D = Kgcs D = Mean Glandular Dose K = Entrance surface air kerma g = glandularity of 50% c = corrects for difference in composition (age dependent) s = X-ray spectrum correction (Target/Filter) Note: g and c depend on thickness, glandularity, and HVL. Primary Ref: D.R. Dance, et al. Additional for the Estimation of Mean Glandualar Breast Dose Using the UK Mammography Dosimetry Protocol. Physics in Medicine and Biology 45, ,

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46 ACR DM QC Manual Status In September 2014, draft sent to manufacturers, select technologists and medical physicists for review We hope manufacturers will adopt this manual Extensive comments received in October Reviewed and incorporated as appropriate Updated draft sent to FDA in February 2015 Comments and instructions for implementation received from FDA late April 2015 ACR DM QC Manual Status (continued) ACR will respond to comments ACR must apply for FDA alternative standard under current regulations Alternative standard will allow facilities to use this instead of the manufacturer s manuals Tomosynthesis QC to be added as Appendix after FDA approval 46

47 Top Strengths & Take Home Points QC Manual is comprehensive Phantom is of major importance Most failures are artifacts Includes most legacy tests Includes most current manufacturer tests Accommodates mfr specific test (where app) Accommodates growth of QC program Manual can realistically be implemented End of Presentation Questions? 47