Implementation of the 2012 ACR CT QC Manual in a ...chapter.aapm.org/nccaapm/z_meetings/2013-05-03...QualityControl Manual.” Page 4: 2012 ACR CT QC Manual What’s Mandatory? Should’s

B R U C E E . H A S S E L Q U I S T , P H . D . , D A B R , D A B S N M

A S P I R U S W A U S A U H O S P I T A L

Implementation of the 2012 ACR CT QC Manual in a Community

Hospital Setting

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

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

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

http://www.acr.org/~/media/ACR%20No%20Index/Documents/Random/2012CTQCManual2.pdf

To be accredited by the ACR

“Effective 12/01/2013, all facilities applying foraccreditation must maintain a documented QC programand must comply with the minimum frequencies oftesting outlined in the 2012 ACR Computed TomographyQuality Control Manual.”

Page 4: 2012 ACR CT QC Manual

What’s Mandatory?

Should’s (177 instances!) Acceptance testing before 1st

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)

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).

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

(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

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

“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.


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


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.

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?

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.)

Daily QC

The QMP should assist with setting up QC protocols and determining pass / fail criteria.

Should acquire a set of standard artifact-free images for comparison with daily QC. Must use daily QC scan protocols to acquire these images.

Test Procedure

Water CT Number and StandardDeviation (noise)

Axial and Helical scansROI in center of image at center of scan as well as at leading or trailing edge of fan beamCT# CriteriaWater: 0 ± 5 HU(“must”)ACR Phan: 0 ± 7 HU(“must”)

Artifact Evaluation Axial scanThinnest available axial imagesacross the full z-axis extent; 2 (LS16) or 3 (VCT) scans, if necessaryRecommend periodic use of larger uniform phantom (manufacturer’s or 32 cm dosimetry phantom)

Weekly QC

To be performed if film is used for primary interpretation.

Test Procedure

Wet Laser Printer QC

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.

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 Procedure

Visual Checklist See QC manual for recommended list of items to check.

Dry Laser Printer QC (same as for WetLaser Printers)

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 Monitor QC

Display SMPTE (or TG18-QC) on acquisition monitor.Evaluate 5% & 95% patches and other gray level patches.

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.

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?

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

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

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)

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

.

0.625 mm

2.5 mm

10 m

m

5 mm

1.25

mm

ACR CTAP Phantom Module 1 or similar

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)

Radiation Beam Width

Scan strip at isocenterusing each unique NxTproduct (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.

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.

ACR CTAP Phantom Module 2 or any phantom with low contrast objects of known contrast.

Scan Protocol CNR (ACR)

Adult Head 1.0

Pediatric Head 1.0

Adult Abdomen 1.0

Pediatric Abdomen 0.5

Spatial Resolution

Evaluate HCR for relevant clinical exams, e.g. adult abdomen and high-resolution chest.

Corrective action is immediate.

Scan Protocol Limiting Resolution

Adult Abdomen 6 lp/cmHigh-Resolution Chest 8 lp/cm

ACR CTAP Phantom Module 4 or any phantom with high contrast objects of known resolution.

CT Number Accuracy

Scan phantom using all 4 ACR clinical protocols. Evaluate CT # in at least three target materials for all 4 scans.

Scan water (or water equivalent) phantom at all clinical kVp’s.

Use ACR accreditation criteria for ACR phantom.

80 kVp 100 kVp

120 kVp 140 kVp

ACR CTAP Phantom Module 1 or similar phantom with water, air and 1 other material

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:

0.625 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.

2.5 mm 16i (40 mm beam collimation) W/L: 20/0

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.

Dosimetry

Equivalent to ACR accreditation dosimetrymeasurement protocol, analysis and criteria.

Additionally, compare measured CTDIvol 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%.

16 cm (head) and 32 cm (body) CTDI dosimetry phantoms

In head holder for adult head;On table for pediatric head and abdomen protocols.

On table for adult abdomen protocol.

Pass/Fail Criteria and Reference Levels

Pass/FailCriteria

ReferenceLevels

Examination CTDIvol (mGy) CTDIvol (mGy)

Adult Head 80 75

Adult Abdomen 30 25

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

Display Monitor Performance

Observe:1) 5%/95% patches2) Line pair patterns3) Black-white transitions4) Loss of bit depth5) Geometric distortion

Measure:1) Min and max brightness (0%, 100%)2) Response curve (GSDF)3) Center / edge brightness uniformity

SMPTE pattern or equivalent (e.g. TG18‐QC)

Min (0%) ≤ 1.2 cd/m2

Max (100%) ≥ 90 cd/m2Luminance nonuniformity should be no more than 15% for FPDs

GSDF should be visually consistent year‐to‐year. (see also TG18 report)

Survey Report Form

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

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


SSP measurements are recommended as part of acceptance testing in the slice thickness section of the ACR QC manual.

ACR CTAP Phantom Module 3 or any phantom with a small high contrast object (0.28 mm for ACR) in a uniform background.

0200400600800

10001200

1 3 5

Max

in R

OI

Distance (mm)


1.25 mm slice

Collimation (mm)

Slice Thickness

(mm)

Recon Interval

(mm)Meas FWHM

(mm)Manuf. Spec.

(mm)

20 1.25 0.125 1.09 1.17

20 2.5 0.25 2.26 2.40

20 5.0 0.5 4.98 5.48

20 (Plus mode) 1.25 0.125 1.34 1.46

40 (Plus mode) 1.25 0.125 1.38 1.50

2012 ACR-AAPM CT Medical Physics Technical Standard

Limited protocol review

Image localization from SPR

Alignment light accuracy

Table incrementation accuracy

Reconstructed image thickness


Image qualityHCR, LCR, Uniformity, Noise, Artifact

CT number accuracy

Dosimetry (CTDIvol, patient dose)

Acquisition workstation display

Safety evaluation, scatter at AT


Scout/alignment light accuracy


Image thickness


Spatial resolution



Artifact evaluation

CT number accuracy

Dosimetry


2012 ACR CT QC Manual

Minnesota Rules 4732.1100

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


Scout/alignment light accuracy


Image thickness


Spatial resolution



Artifact evaluation

CT number accuracy

Dosimetry


2012 ACR CT QC Manual

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

Questions