Implementation of the 2012 ACR CT QC Manual in a Community Hospital Setting BRUCE E. HASSELQUIST, PH.D., DABR, DABSNM ASPIRUS WAUSAU HOSPITAL

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1 Implementation of the 2012 ACR CT QC Manual in a Community Hospital Setting BRUCE E. HASSELQUIST, PH.D., DABR, DABSNM ASPIRUS WAUSAU HOSPITAL

2 Conflict of Interest Disclaimer Employee of Aspirus Wausau Hospital ACR Activities Reviewer for CT accreditation program (physics) Reviewer for NM accreditation program (physics) Member Medical Physics Guidelines Committee No conflicts to disclose

3 Objectives Review the major elements of the 2012 ACR QC manual Compare the manual to current ACR accreditation program and phantom testing requirements and to the current technical standard Highlight some interesting details of the new physicist testing recommendations

4 2012 ACR CT Quality Control Manual Table of Contents Radiologist s Section Definitions of QA and QC Responsibilities Radiologic Technologist s Section Daily QC Weekly QC Monthly QC Medical Physicist s Section Annual QC

5 To be accredited by the ACR Effective 12/01/2013, all facilities applying for accreditation must maintain a documented QC program and must comply with the minimum frequencies of testing outlined in the 2012 ACR Computed Tomography Quality Control Manual. Page 4: 2012 ACR CT QC Manual

6 What s Mandatory? Should s (177 instances!) Acceptance testing before 1 st patient scanned Equipment evaluation dated within 1 year at renewal Evaluation after major repairs, incl x-ray tube and detector assembly replacement Refer to state and local regulations if more restrictive Greater frequently for QC tests when being introduced or results inconsistent. Records accessible from CT scanner location Must s (35 instances!) Maintain documented QC program Comply with minimum testing frequencies QMP oversees QC program QMP monitors performance at installation and annually Annual equipment evaluation submitted initially and at renewal Evaluation dated within 14 months at renewal Evaluation performed by a QMP Annual QMP review of tech QC records (qtly preferred)

7 Quality Assurance is a comprehensive concept to ensure that: 1. Every imaging procedure is necessary and appropriate to the clinical problem at hand; 2. The combination of acquisition parameters used for each exam is appropriate to address the clinical question; 3. The images generated contain information critical to the solution of that problem; 4. The recorded information is correctly interpreted and made available in a timely fashion to the patient s physician; and 5. The examination results in the lowest possible risk to the patient and is consistent with Objective 2 (above).

8 Quality Control is a series of distinct technical procedures Four steps are involved: 1. Acceptance testing to detect defects in equipment that is newly installed 2. Establishment of baseline equipment performance 3. Detection and diagnosis of changes in equipment performance before they become apparent in images 4. Verification that the causes of deterioration in equipment performance have been corrected

9 (Supervising) Radiologist Radiologists must assume the primary responsibility for the quality of CT and for the implementation of an effective QA program at their site. Convene a CT QA or Protocol Review Committee Oversees QA program Sets goals and directions Determines policies Assesses effectiveness of QA activities Assist with development of CT QA Manual Participate in Interpretive Quality Assurance aka peer review

10 Quality Assurance Committee Design and review all new or modified CT protocol settings to ensure that both image quality and radiation dose are appropriate Develop internal radiation dose thresholds during any new CT protocol design. Implement steps to ensure patient safety and to reduce future risk if an estimated dose value is above the applicable threshold for any routine clinical exam Review, at least annually, all protocols to ensure no unintended changes have been applied that may degrade image quality or unreasonably increase dose Establish a policy stating that the CT dose estimate interface option is not to be disabled and that the dose information is displayed during the exam prescription phase

11 Good Practices Established by the Team 1. Technologists are provided access to adequate training and continuing education in CT that includes a focus on patient safety. 2. An orientation program has been provided for technologists based on a carefully established procedures manual. 3. A technologist has been selected as the primary QC technologist to perform the prescribed QC tests. 4. Appropriate test equipment and materials necessary for the technologist to perform the QC tests have been provided 5. Staffing and scheduling are arranged so that adequate time is available to carry out the QC tests and record and interpret the results.

12 Good Practices Established by the Team 6. A qualified medical physicist will review the technologist s test results at least every 3 months or more frequently if consistency has not yet been achieved. 7. A qualified individual has been designated to oversee the safety program for employees, patients, and other individuals in the surrounding area. 8. Established protocols will be followed 9. Corrective action procedures will be followed when images of poor quality are presented for interpretation

13 Good Practices Established by the Team 10. Radiologists will participate in the Radiology Department s practice improvement program 11. Documentation of current qualifications will be provided by all interpreting radiologists in accordance with ACR Accreditation and local rules.

14 CT QA Procedures Manual 1. Who is responsible for QC? 2. What are your QC procedures? 3. Where are the records of all QC tests, service reports, etc? 4. How are your CT operators trained? 5. How is your scanner maintained? 6. What CT protocols are in place? Contrast? Positioning? 7. Do you have minutes from your CT QA committee? 8. What are your policies for pregnant patients and staff? 9. What are your procedures for disinfecting equipment?

15 Technologist QC Effective 12/01/2013, all facilities applying for accreditation must maintain a documented QC program and must comply with the minimum frequencies of testing outlined in the 2012 ACR Computed Tomography Quality Control Manual. Daily Water CT# and standard deviation Artifact evaluation Weekly Wet laser printer QC Monthly Visual checklist Dry laser QC Display monitor QC (See also current ACR CT accreditation requirements document.)

16 Daily QC The QMP should assist with setting up QC protocols and determining pass / fail criteria. Should acquire a set of standard artifactfree images for comparison with daily QC. Must use daily QC scan protocols to acquire these images. Test Water CT Number and Standard Deviation (noise) Artifact Evaluation Procedure Axial and Helical scans ROI in center of image at center of scan as well as at leading or trailing edge of fan beam CT# Criteria Water: 0 ± 5 HU( must ) ACR Phan: 0 ± 7 HU( must ) Axial scan Thinnest available axial images across the full z-axis extent; 2 (LS16) or 3 (VCT) scans, if necessary Recommend periodic use of larger uniform phantom (manufacturer s or 32 cm dosimetry phantom)

17 Weekly QC To be performed if film is used for primary interpretation. Test Wet Laser Printer QC Procedure Film SMPTE pattern 6 on 1 in all 6 frames. Monitor OD s in upper left image for 0%, 10%, 40% & 90% gray level patches. Evaluate film for artifacts. Should be done for each sending modality, e.g. CT and MRI. Target OD s and control limits are provided in manual.

18 Monthly QC Laser printer QC to be performed if film is used for primary interpretation. Backup printers may be tested prior to clinical use as well as when initiating QC program. Display monitors should be recalibrated at least annually. All QC records should be reviewed and signed by QMP as part of equipment evaluation. Retain records for 5 yr. Test Visual Checklist Dry Laser Printer QC (same as for Wet Laser Printers) Display Monitor QC Procedure See QC manual for recommended list of items to check. Film SMPTE pattern 6 on 1 in all 6 frames. Monitor OD s in upper left image for 0%, 10%, 40% & 90% gray level patches. Evaluate film for artifacts. Should be done for each sending modality, e.g. CT and MRI. Target OD s and control limits are provided in manual. Display SMPTE (or TG18-QC) on acquisition monitor. Evaluate 5% & 95% patches and other gray level patches.

19 Automatic QC Procedures Automatic analysis SW may be used but must be approved by QMP. Automatic QC procedures may be used in place of these tests if the Qualified Medical Physicist has critically reviewed them and approved this substitution (in writing). It is not recommended that an automatic QC process be considered as a replacement for the artifact analysis portion of daily QC.

20 Physicist (QMP) Our role Establish continuous QC program for facility Review QC program results annually Equipment evaluations at acceptance and annually Communicating test results and recommending corrective action are areas that can be improved in the practices of most QMPs. Required tests Missing tests Relegate to acceptance?

21 Annual Physics QC Effective 12/01/2013, all facilities applying for accreditation must maintain a documented QC program and must comply with the minimum frequencies of testing outlined in the 2012 ACR Computed Tomography Quality Control Manual. Review of clinical protocols Scout / alignment light accuracy Image thickness Table travel accuracy Radiation beam width Low-contrast performance Spatial resolution CT number accuracy Artifact evaluation CT number uniformity Dosimetry Display monitor performance

22 Review of Clinical Protocols Recommendations provided in QC manual. Team should design and review all new or modified protocol settings Institute a regular review process of all protocols At least 6 protocols (ped / adult: head & abd; high res chest; brain perfusion, if used) Review appropriate use of dose reduction methods Review clinical scans for: Image quality Dose Centering

23 Scout / Alignment Light Accuracy 1. Align phantom with laser and do axial scan. 2. Scout phantom and scan at marker. Scan location relative to alignment light or scout prescription should be accurate to within 2 mm. ACR CTAP Phantom Module 1 or similar (see AAPM Rpt #39)

24 Image Thickness Perform axial scans of the phantom for each reconstructed image thickness used clinically. Image thickness should be within 1.5 mm of nominal thickness. Good practice mandates helical scans (SSP s) at acceptance mm 2.5 mm 10 mm ACR CTAP Phantom Module 1 or similar 5 mm 1.25 mm.

25 Table Travel Accuracy Check known distance and accuracy of return to initial position after travel to max distance. Translation accuracy should be within 2 mm. ACR CTAP Phantom or any phantom with 2 sets of external fiducial markers of known separation (see AAPM Rpt #39)

26 Radiation Beam Width Scan strip at isocenter using each unique NxT product (beam collimation) available. Measure FWHM of beam profile. Compare to manufacturer s standards or ACR criteria of within the greater of 3 mm or 30% of the nominal beam collimation. Note: 120 kvp, 200 mas works well with GAF Chromic film.

27 Low-Contrast Performance Establish correlation to ACR phantom for alternate phantoms. Equivalent to ACR accreditation LCR test protocol, analysis and criteria. Additionally, 6 mm targets must be visualized for adult head and abdomen. Corrective action is immediate. Scan Protocol Adult Head 1.0 Pediatric Head 1.0 Adult Abdomen 1.0 Pediatric Abdomen 0.5 CNR (ACR) ACR CTAP Phantom Module 2 or any phantom with low contrast objects of known contrast.

28 Spatial Resolution Evaluate HCR for relevant clinical exams, e.g. adult abdomen and highresolution chest. Corrective action is immediate. Scan Protocol Adult Abdomen High-Resolution Chest Limiting Resolution 6 lp/cm 8 lp/cm ACR CTAP Phantom Module 4 or any phantom with high contrast objects of known resolution.

29 80 kvp 100 kvp CT Number Accuracy Scan phantom using all 4 ACR clinical protocols. Evaluate CT # in at least three target materials for all 4 scans. 120 kvp 140 kvp Scan water (or water equivalent) phantom at all clinical kvp s. Use ACR accreditation criteria for ACR phantom. ACR CTAP Phantom Module 1 or similar phantom with water, air and 1 other material

30 2.5 mm 16i (40 mm beam collimation) W/L: 20/0 Artifact Evaluation Same test as for daily technologist QC. Perform axial scan(s) using the thinnest available axial slices, spanning the z-axis extent of the detector array. For a GE VCT this could include: mm, 16i (10 mm) 1.25 mm, 16i (20 mm) 2.5 mm, 16i (40 mm) Water phantom provided by CT manufacturer or ACR CTAP Phantom Module 3.

31 CT Number Uniformity ACR recommends using technologist artifact QC protocol. Analysis and criteria are the same as for the ACR accreditation program. Water phantom provided by CT manufacturer or ACR CTAP Phantom Module 3.

32 Dosimetry In head holder for adult head; On table for pediatric head and abdomen protocols. Equivalent to ACR accreditation dosimetry measurement protocol, analysis and criteria. Additionally, compare measured CTDI vol to the values reported by the scanner. Agreement should be within 20%. Be sure to note if scanner display value based on phantom other than the one use for measurement. Year-to-year variation should be no more than 5%. On table for adult abdomen protocol. 16 cm (head) and 32 cm (body) CTDI dosimetry phantoms

33 Pass/Fail Criteria and Reference Levels Pass/Fail Criteria Reference Levels Examination CTDI vol (mgy) CTDI vol (mgy) Adult Head Adult Abdomen Pediatric Head (1 y.o.) 40 (new) 35 (new) Pediatric Abdomen (5 y.o. /40 lb) 20 (was 25) 15 (was 20) Effective July 1, 2013

34 Display Monitor Performance GSDF should be visually consistent year to year. (see also TG18 report) Observe: 1) 5%/95% patches 2) Line pair patterns 3) Black-white transitions 4) Loss of bit depth 5) Geometric distortion Measure: 1) Min and max brightness (0%, 100%) 2) Response curve (GSDF) 3) Center / edge brightness uniformity Min (0%) 1.2 cd/m 2 Max (100%) 90 cd/m 2 Luminance nonuniformity should be no more than 15% for FPDs SMPTE pattern or equivalent (e.g. TG18 QC)

35 Survey Report Form

36 Automatic QC Software Automatic analysis SW may be used but must be verified. CT Scanner Acceptance Testing Perform all tests independent of manufacturer s QC SW Must compare results to SW if it is to be used during annual testing Must verify SW if it was not evaluated during acceptance testing Annual Performance Evaluation Manufacturer s automatic QC SW may be used if previously verified by QMP

37 Additional Physics Tests These tests are not mentioned in the QC manual but could be done at acceptance. Some manufacturer s provide specifications and CTDI adjustment factors that apply to these measurements. Comparison can also be made to console CTDI display values. Image Noise CTDI Accuracy Output Reproducibility Output kvp dependence mr/mas Linearity Output Beam Thickness Dependence EKG ma Modulation Slice Sensitivity Profile Beam Angulation Accuracy Scatter

38 Slice Sensitivity Profile SSP measurements are recommended as part of acceptance testing in the slice thickness section of the ACR QC manual. Collimation (mm) Slice Thickness (mm) Recon Interval (mm) Max in ROI Slice Sensitivity Profile 1.25 mm slice Distance (mm) Meas FWHM (mm) Manuf. Spec. (mm) (Plus mode) (Plus mode) ACR CTAP Phantom Module 3 or any phantom with a small high contrast object (0.28 mm for ACR) in a uniform background.

39 2012 ACR-AAPM CT Medical Physics Technical Standard 2012 ACR CT QC Manual Limited protocol review Image localization from SPR Alignment light accuracy Table incrementation accuracy Reconstructed image thickness Radiation beam width Image quality HCR, LCR, Uniformity, Noise, Artifact CT number accuracy Dosimetry (CTDI vol, patient dose) Acquisition workstation display Safety evaluation, scatter at AT Review of clinical protocols Scout/alignment light accuracy Table travel accuracy Image thickness Radiation beam width Spatial resolution Low-contrast performance CT number uniformity Artifact evaluation CT number accuracy Dosimetry Display monitor performance

40 Minnesota Rules ACR CT QC Manual Accuracy of scout localization view Table backlash & Table indexing Accuracy of distance measurements CT # uniformity and artifacts CT # calibration and noise CT dose index CT # dependence on slice thickness Hard copy output & visual display Review of clinical protocols Scout/alignment light accuracy Table travel accuracy Image thickness Radiation beam width Spatial resolution Low-contrast performance CT number uniformity Artifact evaluation CT number accuracy Dosimetry Display monitor performance

41 How are we doing? Modified annual equipment evaluation protocols Convened CT QA committee Modified our technologist QC program and associated forms not implemented at WI sites Revised policies & procedures at MI sites Created draft site specific CT QA manual Implementing ACR NRDR/DIR program in Wausau Installing and implementing Dose Check SW Continuing to review protocols (esp. pediatric) QC phantom images analyzed monthly by QMP

42 Questions