Requirements of MIPPAamos3.aapm.org/abstracts/pdf/67-17533-26993-305.pdf · – The Joint...

MR Accreditation Programs - E. Jackson

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Edward F Jackson PhD

MRI Accreditation Programs: An Overview of Each and Specifics of One

Diagnostic - MRI Safety and Accreditation

Edward F. Jackson, PhDDepartment of Imaging Physics

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Educational Objectives

At the conclusion of this presentation, the attendee should:– understand the MIPPA Advanced Diagnostic Imaging Accreditation

requirements and choices of accrediting organizations

– understand the current clinical and physics requirements of the d l ACR MRI di imodular ACR MRI accreditation program

– understand the specific ACR program requirements for medical physicists / MR scientists, including CME requirements

– understand the testing requirements for both the large and small ACR MRI accreditation phantoms, and

– understand the annual physics testing requirements for the ACR MR accreditation program

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Requirements of MIPPA

• MIPPA – Medicare Improvements for Patients and Providers Act (passed in 2008)

• Section 135(a) calls for advanced diagnostic imaging accreditation of all facilities that bill the technical componentaccreditation of all facilities that bill the technical component of diagnostic MRI, CT, and nuclear medicine such as PET services

• Facilities must be accredited by January 1, 2012

• However, “all facilities” does not include hospitals

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Requirements of MIPPA

• Currently, the Centers for Medicare and Medicaid Services (CMS) specifically indicates that the advanced diagnostic imaging (ADI) accreditation can be provided by:– The Joint Commission

– The Intersocietal Accreditation Commission

– The American College of Radiology

• Each of these accreditation programs has its own requirements

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The Joint Commission

• The Joint Commission provides Advanced Diagnostic Imaging accreditation as part of its program for accreditation of diagnostic imaging centers.

• Per Joint Commission posted information, providers already accredited by The Joint Commission do not need to be accredited (for ADI) until their current accreditation expires.*

• The ADI accreditation cost depends on the number of annual patient visits and number of sites (branches). Additional fees may be incurred for multiple modalities and sites.**

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* TJC online resource: Accreditation Handbook for Diagnostic Imaging Centers

** TJC online resource: Accreditation for Your Freestanding Imaging Center


• With respect to Standard EC.02.01.01 – The organization manages safety and security.– At a minimum, the organization manages safety risks in the magnetic

resonance environment associated with the following:

P ti t h i l t h bi i t ti l• Patients who may experience claustrophobia, anxiety, or emotional distress

• Patients who may require urgent or emergent medical care

• Metallic implants and devices

• Ferrous objects entering the MRI environment

6TJC online resource: Changes to Standards & EPs for Advanced Imaging Requirements


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• With respect to Standard EC.02.04.01 – The organization manages medical equipment risks.– The organization identifies activities and frequencies to maintain the

reliability, clarity, and accuracy of the technical quality of diagnostic images producedimages produced.

• With respect to Standard EC.02.04.03 – The organization inspects, tests, and maintains medical equipment.– The organization maintains the reliability, clarity, and accuracy of the

technical quality of diagnostic images produced.

7TJC online resource: Changes to Standards & EPs for Advanced Imaging Requirements


• No specific additional information is available regarding the specifics of The Joint Commission ADI accreditation for MRI.

• It is stated that “All initial surveys conducted under the yAdvanced Diagnostic Imaging Services survey option will be conducted on an unannounced basis.”*

8* TJC online resource: Accreditation Handbook for Diagnostic Imaging Centers

Intersocietal Accreditation Commission

• Intersocietal Commission for the Accreditation of Magnetic Resonance Laboratories (ICAMRL) – created in 2000

• As of February 2012, the new name is “ICA MRI”

• Offers accreditation in the areas of:– Cardiovascular MRI

– Breast MRI

– Body MRI (chest (non-cardiac), abdomen, pelvis, extremity)

– Musculoskelatal MRI

– Neurological MRI and MRA

9http://www.icavl.org/iac/forms/MIPPA_FAQ_Key_Elements.pdf


10http://www.intersocietal.org/mri/seeking/fees.htm


• The ICA MRI accreditation process does not “require purchase of a specific phantom. However, through the application process participating laboratories must provide documentation of their ongoing, comprehensive quality

t ”assessment programs.”

• The ICA MRI standards are available online at: http://www.intersocietal.org/mri/seeking/mri_standards.htm

11http://www.intersocietal.org/mri/seeking/fees.htm


• Part I of the standard addresses:– Supervision and Personnel (training and CME requirements)

• Medical Director

• Medical Staff

• Technical Director

• Technical Staff

– Support Services (clerical, nursing, transport, etc.)

– Physical Facilities

– Examination Interpretation, Reports, and Records

– Safety and Patient Confidentiality

12http://www.intersocietal.org/mri/seeking/mri_standards.htm


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• Part I of the standard addresses (continued):– Instrumentation

• Devices must be FDA approved

• MRI unit must be capable of performing multiplanar T1, T2, and STIR sequences with a FOV large enough to consistently image all relevant anatomy in the region of interest

• The equipment specifications and performance must meet all state, federal, and local requirements (dB/dt, B0,max, max SPL, max SAR)

– Multiple Sites



• Part I of the standard addresses (continued):– Quality Assurance

• There must be a quality assurance program in the MR laboratory

– Quality Assurance Committee role

– Quality control tests, standards, thresholds, timelines, and results reviewQ y , , , ,

– Quality control tests should be performed according to the manufacturer’s performance standards by the MR technologist, service engineer, medical physicist, or qualified expert on a timely basis

– Quality assurance documentation must be maintained at the MR laboratory and made available to all personal




• The quality assurance program must consist of MR system installation acceptance testing and major upgrade acceptance testing

– Acceptance testing must be performed as part of the system installation and after major upgrades, prior to patient clinical use.

– The manufacturer’s representative, service engineer, or the MR site-appointed medical physicist, or qualified expert, should perform the acceptance testing.

– Acceptance testing should include, but is not limited to: B0 homogeneity, gradient and RF calibration, resonance frequency, slice thickness and accuracy, image quality (SNR for all coils, spatial resolution, artifacts, image uniformity, geometric distortion, monitor/processor QC)




• Written report of the acceptance tests, signed and dated, must be maintained

• Routine (daily and periodic) QC tests

– Proper function of audible and visual patient safety equipmentp p y q p

– Center frequency tests

– SNR

– Image uniformity

– Artifact assessment

– Deviations from established thresholds must be documented and corrective action taken where appropriate




• Periodic preventive maintenance (PM) service is recommended for each MR scanner

– PM quality control assessment should include, but is not limited to:

• SNR, B0 homogeneity, RF calibration of all coils, spatial resolution, artifact assessment

• General equipment inspection, e.g., RF coil cables, RF shielding, etc.

– A complete report of PM, QC tests, and service records must be maintained and must be signed and dated by the person(s) performing the tests.

• Ancillary equipment must be included as part of the QA program



• Part II of the standard addresses:– Indications (body, cardiovascular, MSK, neurological, breast, MRA)

– Techniques• Positioning and coil selection

• Appropriate protocol & optimization of pulse sequence(s) for the indicationAppropriate protocol & optimization of pulse sequence(s) for the indication

• Utilization of appropriate software, workstations, techniques, and measurements

• A complete, written description of each protocol must be maintained, including acquisition details, contrast agent administration, filming, etc.

– Procedure Volumes

– Technical and Interpretative Quality Assessment• Technical / Administrative Quality Assessment, including appropriate use criteria

• Interpretative Quality Assessment – over-reads, correlation with outcomes, etc.



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• Application– Case Studies

• EFFECTIVE 1/1/12 | Applicant facilities must submit six (6) total case studies for each MRI unit. Cases must represent each area of testing that is performed on the scanner, i.e., Cardiovascular MRI, Breast MRI, Body MRI [chest (noncardiac), bd l i i ] M l k l l MRI N l i l MRI MRAabdomen, pelvis, extremity], Musculoskeletal MRI, Neurological MRI, MRA.

For example, if your facility is applying in two of the following testing areas you must submit 3 cases for each testing area; if your facility is applying in one testing area, you must submit 6 case studies total.

• In addition, the printed or electronic final reports and MRI Scan Parameter Forms must be submitted.

• Cases must have been obtained within the 12 months prior to the date of submission

19http://www.intersocietal.org/mri/seeking/case_studies.htm


• Application– IAC agreement

– Copies of various site policies

– Acceptance testing results (at installation and/or after major upgrade). All acceptance tests completed after January 5, 2011 must include submission of the QC t t lt ith th h t iQC test results with the phantom images.

– 5 days of daily quality control tests with the results and the phantom images

– Preventative maintenance (PM) report (performed six months prior to application submission)

– Two (2) months of QA meeting minutes (for facilities applying for reaccreditation)

Note: All phantom images must be submitted on CD or DVD with a DICOM viewer.

20http://www.intersocietal.org/mri/seeking/required_items.htm

ACR Accreditation Programs

– Purpose:

• to set quality standards for practices and to help continuously improve the quality of patient care

• to be educational in natureto be educational in nature

– Beneficial for accrediting body and site• ACR assists sites improve practice

• Site obtains PR benefit

• Sites assist ACR in gathering information about MRI practices.

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ACR MRI Accreditation Overview

• History– 1996 – ACR MR program accreditation launched

– 2001 – Initial MR QC Manual released

– 2004 – QC Manual updateQ p

– 2005 – 3-T magnets included

– 2006 – Documentation of QC and annual system performance evaluation required

– 2008 – Modular program introduced

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ACR MRI Modular Program

Whole body(brain, C-spine,L-spine knee)

• Head• Spine• Musculoskeletal• Body

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L spine, knee)• MR angiography• Cardiac

Note: Breast MR accreditation is included in the Breast Imaging Accreditation program

“Every unit must apply for all modules routinely performed on that unit for a facility to be accredited.”

ACR Accreditation Process Overview

Submission materials:– Scanner information

– Most recent annual medical physicist performance report

Personnel q alifications and CME information– Personnel qualifications and CME information

– Clinical images for each module submitted

– Phantom images with associated site scanning data form

– Most recent quarter of QC data

– $$$$

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ACR CME Requirements

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ACR MRAP Cost

Accreditation – First Unit$2400 (1-4 modules)$2600 (5 modules)$2800 (6 modules)

$2300 (1-4 modules)

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Accreditation – Second Unit $2500 (5 modules)$2700 (6 modules)

Repeat$800 per unit for clinical or phantom$1600 for both

Add units or module (mid-cycle) $1600 per unit

Clinical Images

Examination Choices for MRAP by module:- see “MRI Accreditation Program Requirements” file on ACR website, p. 12 of 15

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Clinical Images

Examination Choices for MRAP by module:- see “MRI Accreditation Program Requirements” file on ACR website, p. 12 of 15

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Clinical Images

Evaluated for

1) appropriate pulse sequence and contrast,

2) filming technique (if appropriate),2) filming technique (if appropriate),

3) anatomic coverage and imaging planes,

4) spatial resolution,

5) artifacts, and

6) appropriate labeling of images

Must be submitted in DICOM format on CD with embedded viewer. Requirements for

viewer must are provided in the ACR MRI Clinical Image Quality Guide.

29 30


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Phantom Images – Discussed in detail on subsequent slides

– Acquired on ACR MR Accreditation Phantom using specified T1- and T2-weighted protocols plus the site’s T1- and T2-weighted protocols (for brain imaging).weighted protocols (for brain imaging).

– Must be submitted in DICOM format on CD-ROM (w/o embedded viewer; no image compression)

– Evaluated for 1) geometric accuracy, 2) high contrast spatial resolution, 3) slice thickness accuracy, 4) slice position accuracy, 5) signal uniformity, 6) ghosting, 7) low contrast detectability.

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• Annual MRI System Performance Evaluation– Must be performed by a medical physicist / MR scientist

– Includes MRAP phantom scans and tests required for weekly QC and specific tests of:

• Magnetic field homogeneity

• Slice thickness and position accuracy

• Radiofrequency coils– SNR – all coils

– Uniformity – all volume coils

• Soft-copy displays (monitors)

– Should also provide an assessment of MR safety issues at the facility32

ACR MR Accreditation Phantom

Large Phantom: $1050

Small Phantom: $ 780 (Ortho)

(as of 2/10/2012)

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ACR Phantom Scan Documentation

Contains information on:• Phantom position• Pulse sequences to be usedq• Filming and data preparation instructions

Sent to site with Full Application

Available from the ACRhttp://www.acr.org/accreditation/mri/mri_qc_forms.aspx

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ACR Phantom Scan Documentation

Contains information on:• Test analysis• Performance criteria• Common reasons for failure

Sent to site with Full Application

Available from the ACRhttp://www.acr.org/accreditation/mri/mri_qc_forms.aspx

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Alignment of the ACR Phantom

Alignment is important!

• Center phantom in head coil – use foam, stack of paper, paper

towels, or cardboard

• Make sure phantom is straight– use bubble level

• Make sure phantom is centered SI, LR & AP

– make localizer images in all 3 planes

– use grid to check centering

• Record position for future use46


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ACR Phantom Scans

• Sagittal Localizer– TE/TR=20/200ms, 25 cm FOV, 256x256, 1 20-mm, 1 NEX, 0:56

• ACR T1 Axial SeriesTE/TR 20/500 25 FOV 256 256 11 5 li– TE/TR=20/500ms, 25 cm FOV, 256x256, 11 5-mm slices (graphically prescribed), 1 NEX, 2:16

• ACR T2 Axial Series– TE1/TE2/TR=20/80/2000ms, 25 cm FOV, 256x256, 11 5-mm

slices (same locations as for ACR T1 series), 1 NEX, 8:56

• + Site T1 and T2 Axial Brain Series

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#1 #7 #8

#10 #11#5 #9 #10 #11

#1) Slice thickness and position, geometric accuracy, high contrast resolution#5) Geometric accuracy

#7) Percent image uniformity, ghosting#8-11) Low contrast object detectability, and slice position (in #11)

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Geometric Accuracy

True Dimension: 148 mmTrue Dimension: 190 mmACR T1

Slice 1 Slice 5Sag Loc

Set WW & WL to min, then raise WL until 1/2 water is dark (mean)Set WW to mean and WL to 1/2(mean)

Criterion: ± 2 mm

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Slice Position

ACR T1 & T2

Slice 1 Slice 11 Criterion:<5mm

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Slice Thickness

Two 10:1 ramps

•Magnify image by 2 4x

ACR T1 & T2Slice 1

•Magnify image by 2-4x.

•Define two ROIs, one on each ramp.

•Obtain average intensity from the two ROIs.

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Slice Thickness

Measurements:• lower level to ½ average

• set window width to minimum

• measure lengths of top and• measure lengths of top and bottom ramps

• calculate slice thickness

Criterion: 5.0±0.7 mm

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High Contrast Spatial Resolution

• Magnify by 2-4x.

• Use UL for horizontal resolution and LR for vertical resolution.

• Must be able to resolve 1.0 mm

ACR T1 & T2

Slice 1

holes vertically and horizontally.

1.1 1.0 0.9 mm

UL

LR

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Spatial Resolution Matrix: Registration with Phantom

ResolutionHoles

ImageMatrix

Image compliments of Geoff Clarke, PhD54

Low Contrast Detectability

Slice 8: 1.4%Slice 9: 2.5%Slice 10: 3.6%

ACR T1 & T2

Slices 8-11

≤1.5TCriterion ≥ 9 spokes

Slice 10: 3.6%Slice 11: 5.1%

3.0TCriterion ≥ 37 spokes

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1.5 T 0.3 T

Low Contrast: High vs. Low Field

Slice 11 - ACR T1 series56

Percent Image Uniformity

Slice 7

ACR T1 & T2

(~1 cm2)

Large ROI (195-205 cm2)

percent integral uniformity = 100

1

( )

( )

high low

high low

Criterion: PIU 87.5% Criterion: PIU 82%

≤1.5T 3.0T

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Ghosting

Ghost ratio =

|(top+bottom) (left+right)|

Slice 7

ACR T1

|(top+bottom) - (left+right)|(2 large ROI)

Criterion: 0.025

ROIs ~ 10 cm2 with ~4:1 length:width

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Ghosting

Window and level to make sure ROIs are in background noise! (Warping of image space due to gradient nonlinearity corrections.)

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Common Problems and Artifacts

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Potential Causes of Geometric Accuracy Failures

• Poor phantom positioning - relatively common problem

• Poor gradient calibration

• Bo inhomogeneityF ti bj t i t• Ferromagnetic objects in magnet

• Poor magnet shimming

• Gradient non-linearity (not appropriately corrected)

• Inappropriate receiver bandwidth

• Poor eddy current compensation

• Combination of two or more of above61

Poor Positioning

Rotation (in-plane)

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Poor Positioning

Rotation (through-plane, RL)

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Poor Positioning

Rotation (through-plane, AP)

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10

Sources of Geometric Distortion

• System Limitations– Poor Bo homogeneity

– Linear scale factor errors in the gradient fields

– Field distortion due to induced eddy currents

– Nonlinearities of the gradient fields

• Object-Induced– Chemical shift effects

– Magnetic susceptibility variations (patient induced)

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Spatial Accuracy

Be sure to make sagittal measurements at the centermeasurements at the center of the phantom (or as close as possible to the center).

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Air Bubbles

When a large air bubble is present in the phantom, geometric distortiongeometric distortion measurement may have to be taken along diagonal instead of vertical.

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Low Acquisition Bandwidth

Note distortion as well as increased susceptibility artifacts.

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Air Bubbles

16 kHz 8 kHz

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Spatial Resolution Matrix: Registration with Phantom

ResolutionHoles

ImageMatrix



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High-Contrast Spatial Resolution

Common causes of failure;

• Incorrect FOV or matrix size

P di t lib ti• Poor gradient calibrations

• Excessive filtering (smoothing)

• Poor eddy current compensation

• Gradient amplifier instability

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Big ROI ~ 195 cm2

(19,500 mm2)

Image Intensity Uniformity

ACR phantom - Slice #7

Max Signal

Min Signal

Small ROI’s ~ 1 cm2

(100 mm2)

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Image Intensity Uniformity

Common causes of failure:

Poor phantom centering in coil (usually in AP direction)

Ghosting

Motion or vibration

Mechanical failure in head coil

Note: Uniformity becomes poorer with increasing Bo (especially above 2 T) because of dielectric field focusing phenomenon (aqueous phantom).

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Percent Signal Ghosting

• Must pass on slice #7 of ACR T1-weighted axial series.

• Ghost signal is measured and reported as percentage of the• Ghost signal is measured and reported as percentage of the signal in the true image

• Excessive ghosting in other images may be counted as “Unacceptable Artifact”

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Phase

Readout

NOISENOISE

Phase Ghosting

Readout

NOISENOISE

GH

OS

TG

HO

ST

GH

OS

TG

HO

ST G

HO

ST

GH

OS

T


Ghosting is Nonspecific

• Instability in MRI signal from pulse to pulse

• Phantom motion

• Loose connections or bad cable

• Partial failure of radiofrequency coils or gradient subsystem

• Pulse sequence calibration error

– Eddy currents in Fast Spin Echo series

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Ghosting

Ghosting may obscure otherwiseobscure otherwise visible LCD spokes



ACR T1 & T2

Slice 8: 1.4%

Slice 9: 2.5%

Slice 10: 3.6%

Slice 11: 5.1%

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Some common causes of failure:

– Incorrectly positioned slicesContrast based on partial volume averagingContrast based on partial volume averaging

– Tilted phantom

– Incorrect slice thickness

– Ghosting

– Inadequate SNR

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DC Offset Artifacts

Large artifact off to side.NEX=1; frequency shifted


Susceptibility Artifacts

Small inclusions in LCD insert can make analysis difficult.

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Details of the ACR MRI QC Manual

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MRI QC Manual OverviewCurrent Version: 2004

• Radiologist’s SectionDescribes requirements and the role in a QA program

• Technologist’s SectionOutlines the recommended daily and weekly QC tests

• Physicist’s / MRI Scientist’s SectionSuggestions for setting up a QC programOutlines recommended annual equipment performance tests

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Quality Assurance Manual

Should contain the following:• Responsibilities and procedures for QC testing.• Records of the most recent QC tests.• A description of the orientation program procedures forA description of the orientation program procedures for

use and maintenance of the equipment.• MRI techniques to be used.• Precautions in place to protect the patient.• Proper maintenance of records, including records of

testing, equipment service, and QA meetings.• Procedures for cleaning and disinfection.

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Radiologist’s Responsibilities

• To ensure adequate training and continuing education in MRI

• To provide an orientation program for technologists

• To ensure that an effective quality control program exists for all MRI procedures

• To select the technologist to be the primary quality control technologist

• To ensure that appropriate test equipment and materials are available to perform the technologist’s QC tests.

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Radiologist’s Responsibilities (cont.)

• To arrange staffing and scheduling so that QC tests can be carried out.

• To provide feedback to the technologists.

T l lifi d di l h i i MRI i i• To select a qualified medical physicist or MRI scientist.

• To review the technologist’s test results

• To oversee or designate a qualified individual to oversee the safety program.

• To ensure that records are properly maintained and updated in the MRI QC procedures manual.

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Technologist’s Responsibilities

• Daily (weekly*) MR image QC procedures

• QC of hard and soft copy images

• Routine visual inspection of equipment

• Note: Effective May 2, 2002, the performance of daily QC tests is NOT required. All daily tests mentioned in the QC Manual are now required at least weekly (but daily testing is encouraged).

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Technologist’s Responsibilities

• Medical Physicist/MR Scientist interactions:

– Physicist assures correct implementation an execution of the QC procedures

Physicist reviews QC notebook at least annually (quarterly preferred)– Physicist reviews QC notebook at least annually (quarterly preferred)

• Radiologist interactions:

– Radiologist informs technologist about image quality problems

– Radiologist decides whether or not patient studies can continue

– Radiologist participates in the initial assessment of image quality and regularly monitors the QC results in the intervals between annual reviews

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Medical Physicist’s Responsibilities

• Write purchase specifications

• Perform acceptance testing and establish baseline QC measurementsmeasurements

• Determine action limits for measured parameters

• Setup daily/weekly QC tests

• Perform annual MRI equipment performance reviews

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Details of the Technologist’s Responsibilities

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Technologist’s Section

91


• Identification of the designated QC technologist(s)

• Maintenance of the QC Notebook– QC policies and proceduresQ p p

– Data forms where QC procedure results are recorded

– Notes on QC problems and corrective action(s)

• Document QC data review

• Alternative phantoms and procedures

• Action limits

92


• Routine tests using ACR phantom and ACR T1-weighted head scan:– Center frequency (daily/weekly)– Geometric and positioning accuracy (daily/weekly)p g y ( y y)– Image quality (daily/weekly)

• High contrast resolution

• Low contrast object detectability

– Artifact evaluation (daily/weekly)

• Plus:– Processor sensitometry (weekly)– Physical and mechanical inspection (weekly)

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17 min

94


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Daily (Weekly)– Record central frequency and transmit gain (attenuation) settings

for the ACR axial T1 series.

– Check position accuracy by ensuring central grid structure is within 2 mm of the center of the imagewithin 2 mm of the center of the image

– Verify geometric accuracy by ensuring length (sagittal localizer image) and vertical/horizontal diameter (axial slice #5) measures are within 2 mm of true values

– Verify high contrast resolution (vertical and horizontal) using T1

series axial slice #1

– Verify low contrast object detectability levels using T1 series axial slice #8, 9, 10, or 11 (as determined by physicist/MR scientist)

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Daily (Weekly) (cont)– Assess level of image artifacts in axial T1 series

• Phantom should appear circular

• There should be no ghost images in the background or overlying the phantom image

• There should be no streaks or artifactual bright or dark spots in the image

• There should be no unusual or “new” features in the image.

96

Daily Axial ACR T1 Series

• Spin-echo sequence

• TE/TR=20/500ms

• Slice thickness / gap = 5/5 mm

• 11 slices graphically prescribed from sagittal localizer

• FOV = 25 cm

• Matrix: 256x256

• 1 average (NEX, NSA, etc.)

• Scan time: 2:16 min97

Daily Tests - Transmitter Gain and Frequency

• During the prescan for the T1 series, the scanner determines the appropriate transmitter gain (or attenuation) and transmit (center) frequency.

h l il b i d h• On some scanners, these values are easily obtained at the end of prescan and/or from the series text page.

• On other scanners, these values will need to be obtained from special options (see service engineer).

• The transmit gain (attenuation) value and center frequency value should be recorded daily.

98

Daily Tests - Geometric Accuracy

True Dimension: 148 mmTrue Dimension: 190 mm

Slice 5 Sag Loc

Criteria: ± 2 mmSet WW & WL to min, then raise WL until 1/2 water is dark (mean)Set WW to mean and WL to 1/2(mean)

99

Daily Tests - High ContrastSpatial Resolution

• Magnify by 2-4x.

• Use UL for horizontal resolution and LR for vertical resolution.

• Must be able to resolve 1.0 mm holes vertically and horizontally.

1.1 1.0 0.9 mm

UL

LR

100


16

Daily Tests - Low Contrast Detectability

Count and record the number of spokes in the slice determined by the Medical Physicist or MR Scientist. (T i ll li 11 f l(Typically slice 11 for low field and slice 8 or 9 for high field.)

Action criteria:Change of more than 3 spokes (or as determined by QC procedure).

101

Daily Tests - Assessment of Artifacts

• Look at all slices from the localizer and axial T1 series.

• Modify window width and level to look for ghosting if d di f i f ifartifacts and radiofrequency interference artifacts.

• Note any change in image quality relative to baseline scans.

102

Technologist’s QC Log - Daily Tests

103

Weekly Tests - Processor QC

Weekly Testsy

SMPTE Pattern Gray Level Ring

104


Weekly Hard Copy QC Tests:

• Display SMPTE test pattern.

• Visually examine the SMPTE pattern (0/5% and 95/100% patches).

• Measure the optical density (OD) of the 0, 10, 40, and 90% gray level patches with a densitometer.

• Plot OD values on the Laser Film QC Chart.

• Inspect film for streaks, uneven densities, and other artifacts.

105


107


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Weekly Tests - Visual Inspection

At least weekly visual inspection tests:

• Check patient table, patient communication, patient “panic buttons”, transport, alignment, and system indicator lights

• Check RF room integrity (particularly RF doors)

• Check that emergency cart, safety lights, signage, and patient monitors (and supplies) are present and in working order

• Check that all RF coils are present and in apparent good working condition (no frayed cables, etc.)

108

RF Shielded Room Door

• The RF door “fingers” provide good electrical contact of the shielded door and the rest of the Faraday cage shield.y g

• If the fingers are damaged, as they will inevitably be, the effectiveness of the shield decreases and will ultimately give rise to RF interference artifacts (or cause them on an adjacent scanner!).

109

RF Coil Weekly Checks

• Be sure to check all cables on RF coils, particularly high use and/or flexible coilsand/or flexible coils.

• Any suspicious coils, cables, or connector boxes should be reported immediately to your service organization and/or vendor’s service engineer.

110

Technologist’s QC Summary

• Technologist runs QC runs on a daily (weekly) basis, and records the results in the QC logbook.

• If any test result exceeds the appropriate action limit (established by Medical Physicist/MR Scientist), repeat QC test. If still fails, notify service (and log service call).

• Action criteria are usually set based on 10 or more repeated measurements.

112

Some Details of the Medical Physicist’s / MR Scientist’s Responsibilities

113


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• Performs acceptance tests– New systems before first patient scan– Following any major hardware or software upgrade

• Acquires baseline QC data acquisition and establishes

Medical Physicist/MR Scientist Responsibilities

action limits– Central frequency– Transmitter gain / attenuation– Geometric accuracy– High contrast resolution– Low contrast object detectability

• Artifact analysis114


• Laser camera QC– Establish operating levels (in consultation with laser film

system service engineer)

• Acquire baseline data (using SMPTE test pattern)

• Corrective actions– Determination of whether problem lies in the camera,

processor, and/or MR system

115


Annual Physics Tests– Magnetic field homogeneity

– Slice position accuracy

– Slice thickness accuracy

RF il h k– RF coil checks• Signal-to-noise ratio (all coils)

• Image uniformity (volume coils)

– Interslice RF interference

– Phase stability (ghosting)

– Soft copy displays (monitors)

– Assessment of MR safety program

116

Ideal Homogeneity Good Homogeneity Poor Homogeneity

FWHM

Magnetic Field Homogeneity

o oo

Fourier transform of signal produces a

Lorentzian peak in well-shimmed

magnet

Magnet field homogeneity can be characterized using

FWHM of resonance peak

Denotes a totally uniform magnetic field.All signal is at resonant

frequency, o.

FWHM

117


One vendor’s “head equivalent” phantom.

Insert sphere can be pused for homogeneity test.

(Remove sphere from cylindrical “loader” first. Place at isocenter in head coil.)

118


With sphere in head coil, use manual prescan.

Adjust center frequency twice to determine the “full width at half maximum” of the spectrum.

119


19


Phase images from GRE sequences with 10ms difference in TE’s

Phase and Unwrapped Phase Images

The change in phase acrossthe phantom is proportional to the inhomogeneity of themagnetic field.

120


LVshim Report

Exam 50196, Series 2, Image 1

(Fri Jan 24 20:35:23 1997)

Scan Bandwidth = 200 HzSc dw d 00

Field of View = 50 cm

Sampling Diameter = 22 cm

Inhomogeneity

3.19 Hz (0.050 ppm)

Harmonic Coefficients given for Z1, Z2, Z3, Z4, Z5, Z6,X, Y, ZX, ZY, X2-Y2, XY, Z2X, Z2Y, ZXY, etc.

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• Either the FWHM technique (on a given spherical phantom) or the phase difference technique can be used to assess homogeneity if possible at a given site.to assess homogeneity if possible at a given site.

• Alternative: Use the service engineer’s report on homogeneity for your site records of homogeneity.

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Slice Position Accuracy

Slice Position Slice Spacing

SLICE #1 SLICE #11

Crossed wedges should be of equal lengthif position and spacing are accurate (and phantom is not tilted!)

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Slice Thickness

Measurements:• lower level to ½ average

• set window at minimum

• measure lengths of top and• measure lengths of top and bottom ramps

• calculate slice thickness

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MRI Equipment Performance Evaluation

Site: _____________________________ Date: ________MRAP Number: ____________________ Serial Number: ___________

Equipment: MRI System Manuafacturer: _________________ Model : ________

Processor Manufacturer : _________________ Model: _________

PACS Manufacturer: _________________ Model: _________

ACR MRAP Phantom Number used: _________

1. Magnetic Field Homogeneity

Method Used (check one): Spectral Peak ___ Phase Difference ___Other (desc ribe) __________________________

Measured Homogeneity: Diameter of Spherical Homogeneity Volume (cm) (ppm)

Site & Equipment

Data

Bo

Homogeneity________ _______________ _______________ _______

2. Slice Position Accuracy

From Slice Positionss #1 and #11 of the ACR Phantom:

Wedge (mm)

Slice Location #1 ________

Slice Location #11 ________

3. Slice Thickness Accuracy

From Slice Position #1 of the ACR Phantom:

Slice Thickness Top ______ Calculated slice

(fwhm in mm) Thickness (mm) ______

Bottom ______

Duplicate these forms so they will be available for repeated use.

=+ = -

=+ =

-

Slice PositionAccuracy

Slice ThicknessAccuracy


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Volume RF Coil Measurements

Must assess SNR,

uniformity, and h i i

ACR PhantomSlice #7

ghosting ratio for every

volume coil.

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Volume Coils -SNR, Uniformity, and Ghosting

• Uniformity performance criteria: PIU 90%

percent integral uniformity = 100

1

( )

( )

high low

high low• SNR (no fixed criteria)

(Mean Signal ROI) / (SD of Noise ROI)

• Percent Signal Ghosting

100

2

Left Right Top Bottom

Mean Signal

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Phased-Array Coils

WristPh d ABreast

Phased Array

Head-Neck-Spine Phased Array

TorsoPhased Array

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Phased Array

Phased-Array Coils

Example of a particular vendor’s C-T-L spine phased array coil QC phantom

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Surface RF Coil Measurements

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Volume Coil Data

Ghost Signal

M Si lPercent Signal Ghosting

Mean Signal

SD of Background SignalSignal-to-Noise

Max Signal

Min Signal% Image Uniformity

Mean Signal

Background Signal

Surface Coil DataMaximum signal

SD of Background SignalMaximum Signal-to-Noise


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Volume Coil

Calculated Values:Uniformity

SNRGhosting

4 . RF Coil Performance Evaluation

A. VOLUME RF COIL - RF Coil Description: __________________________ Date: ____________

Phantom Description: ___________________________________________

Pulse Sequence: Type: ____ TR: _____ TE: ______ flip angle _____ degrees

FOV: _____ cm2 Matrix: ___________ BW: _________kHz ; NSA ___

Slice thickness ______mm; spacing _______ mm

TX attenuation (or gain) __________ Data Collected:

Mean Signal

Maximum Signal

Minimum Signal

Background Signal

Noise Standard Deviation

Ghost Signal

Calculated Values:

Signal-to-Noise Ratio

Percent Image Uniformity

Percent Signal Ghosting

-Surface Coil

B. RF SURFACE COIL -

RF Coil Description: __________________________ Date: ____________


Pulse Sequence: Type: ____ TR: _____ TE: ______ FOV: _____ cm2

Matrix: ___________ BW: _________kHz ; NSA ___

Slice thickness ______mm; spacing _______ mm

TX attenuation (or gain) __________

Maximum Signal

Noise Standard Deviation

Maximum Signal-to-Noise Ratio

Image uniformity distribution OK? ________

Image ghosting OK? ________

HARD COPY IMAGE: Window width ________ Window level _______

Several copies of this page may be required to report on all RF coils.

Calculated Value:Maximum SNR

Soft Copy Displays

• Requires precision luminance meter

• Four tests:– Maximum and minimum luminance– Luminance uniformity– Resolution (SMPTE)– Spatial accuracy (SMPTE)

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Soft Copy Displays

• Max luminance (WL/WW min): 90 Cd/m2

• Min luminance: <1.2 Cd/m2

• Luminance uniformity: Each of the l minance al es obtained at the fo rluminance values obtained at the four corners of the screen should be within 30% of the maximum value measured at the center (WL/WW min).

• Resolution: Use SMPTE 100% contrast patterns (see QC manual, p. 117).

• Spatial accuracy: Use SMPTE grid pattern (see QC manual, p. 117).

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RF Slice Interference

S ft C

5. Interslice RF Interference


Pulse Sequence: Type: ____ TR: _____ TE: ______ FOV: _____ cm2

Matrix: ___________ BW: _________kHz ; NSA ___

Number of slices______

6. Soft Copy Displays

Monitor Description: __________________________________________

M i L i Cd -2

S e rie s S lice S ig na l-N u m b e r G a p to - N o ise

(m m ) R a tio

1

2

Me

asu

red

SN

R

10 0 %

90 %

80 %

70 %0 % 25 % 50% 7 5% 1 00 %

In te r- sl ic e G a p (p e rce n t o f sl ic e th ic kn e ss)

3

4

S e rie s S lice S ig na l-N u m b e r G a p to - N o ise

(m m ) R a tio

1

2

Me

asu

red

SN

R

10 0 %

90 %

80 %

70 %0 % 25 % 50% 7 5% 1 00 %

In te r- sl ic e G a p (p e rce n t o f sl ic e th ic kn e ss)

3

4

-

Soft CopyDisplays

Review of Routine QC Program

Maximum Luminance: ________________________ Cd m 2.

Minimum Luminance: _________________________ Cd m-2.

Luminance Uniformity:

Average of values obtained in four corners of screen: ______ Cd m-2.

Luminance measured in center of screen: ______ Cd m-2.

Percent difference: ________ %

|(Center – Average Corners)/(Center) x 100% < 30%|

7. Evaluation of Site’s Technologist QC Program

4) Set up and positioning accuracy: (daily) _________

5) Center Frequency: (daily) _________

6) Transmitter Attenuation or Gain: (daily) _________

7) Geometric Accuracy Measurements: (daily) _________

8) Spatial Resolution Measurements: (daily) _________

9) Low Contrast Detectability: (daily) _________

10) Film Quality Control (weekly) _________

Visual Checklist: (weekly) _________

MRI Equipment Evaluation Summary

Site ___________________ Report Date: __________ System MRAP #_____________ Survey Date: __________

MRI System Manufacturer ___________ Model: __________ Physicist/MRI Scientist: ____________________ Signature: ________________________________

Equipment Evaluation Tests

Pass / Fail 1. Magnetic Field Homogeneity: _________ 2. Slice Position Accuracy _________

3. Slice Thickness Accuracy _________ 4. RF Coils’ Performance

a. Volume Coils’ Signal-to-Noise Ratio _________ b. Volume Coils’ Image Uniformity _________ c. Volume Coils’ Ghosting Ratios _________ d. Surface Coils’ Signal-to-Noise Ratio _________ 5. Inter-slice RF Interference _________ 6. Soft copy displays _________

M di l Ph i i t’ MRI S i ti t’ R d ti f

SummarySh t Medical Physicist’s or MRI Scientist’s Recommendations for

Quality Improvement: ______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Sheet

ACR MRI QC Program Summary

• Technologist– Performs daily (weekly) tests to assess image quality using the

ACR phantom– Performs weekly tests of hard copy output

M i t i QC t b k!!– Maintains QC notebook!!

• Medical Physicist / MR Scientist– Runs baseline tests of system performance– Sets action limits for daily ACR phantom tests– Performs annual system performance tests– Reviews all QC program data annually

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22

ACR MRI QC Program Summary

• Radiologist– Ultimately responsible for all QA for the facility

• All measurements, problems reported, and actions required to resolve the problems must be recorded for review, as must all preventive maintenance and repair records from the vendor or service organization.

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