MR Accreditation Programs - E. Jackson
Diagnostic - MRI Safety and Accreditation
Educational Objectives
MRI Accreditation Programs:
An Overview of Each and Specifics of One
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
modular
d l ACR MRI accreditation
di i program
Edward F
F. Jackson
Jackson, PhD
Department of Imaging Physics
– 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
Requirements of MIPPA
• MIPPA – Medicare Improvements for Patients and Providers
Act (passed in 2008)
• Currently, the Centers for Medicare and Medicaid Services
(CMS) specifically indicates that the advanced diagnostic
imaging (ADI) accreditation can be provided by:
• Section 135(a) calls for advanced diagnostic imaging
accreditation of all facilities that bill the technical component
of diagnostic MRI, CT, and nuclear medicine such as PET
services
– The Joint Commission
– The Intersocietal Accreditation Commission
– The American College of Radiology
• Facilities must be accredited by January 1, 2012
• However, “all facilities” does not include hospitals
• Each of these accreditation programs has its own requirements
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The Joint Commission
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.**
• 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:
• Patients
P ti t who
h may experience
i
claustrophobia,
l t h bi anxiety,
i t or emotional
ti l
distress
• Patients who may require urgent or emergent medical care
• Metallic implants and devices
• Ferrous objects entering the MRI environment
* TJC online resource: Accreditation Handbook for Diagnostic Imaging Centers
** TJC online resource: Accreditation for Your Freestanding Imaging Center
TJC online resource: Changes to Standards & EPs for Advanced Imaging Requirements
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MR Accreditation Programs - E. Jackson
The Joint Commission
The Joint Commission
• With respect to Standard EC.02.04.01 – The organization
manages medical equipment risks.
• No specific additional information is available regarding the
specifics of The Joint Commission ADI accreditation for MRI.
– The organization identifies activities and frequencies to maintain the
reliability, clarity, and accuracy of the technical quality of diagnostic
images produced.
produced
y conducted under the
• It is stated that “All initial surveys
Advanced Diagnostic Imaging Services survey option will be
conducted on an unannounced basis.”*
• 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.
TJC online resource: Changes to Standards & EPs for Advanced Imaging Requirements
* TJC online resource: Accreditation Handbook for Diagnostic Imaging Centers
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Intersocietal Accreditation Commission
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
http://www.icavl.org/iac/forms/MIPPA_FAQ_Key_Elements.pdf
http://www.intersocietal.org/mri/seeking/fees.htm
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Intersocietal Accreditation Commission
Intersocietal Accreditation Commission
• Part I of the standard addresses:
• 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
assessmentt programs.””
– Supervision and Personnel (training and CME requirements)
•
•
•
•
–
–
–
–
• The ICA MRI standards are available online at:
http://www.intersocietal.org/mri/seeking/mri_standards.htm
http://www.intersocietal.org/mri/seeking/fees.htm
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
http://www.intersocietal.org/mri/seeking/mri_standards.htm
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MR Accreditation Programs - E. Jackson
Intersocietal Accreditation Commission
Intersocietal Accreditation Commission
• Part I of the standard addresses (continued):
• Part I of the standard addresses (continued):
– Instrumentation
– Quality Assurance
• 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)
• There must be a quality assurance program in the MR laboratory
– Quality Assurance Committee role
Quality
y control tests,, standards,, thresholds,, timelines,, and results review
– Q
– 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
– Multiple Sites
http://www.intersocietal.org/mri/seeking/mri_standards.htm
http://www.intersocietal.org/mri/seeking/mri_standards.htm
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Intersocietal Accreditation Commission
Intersocietal Accreditation Commission
• Part I of the standard addresses (continued):
• Part I of the standard addresses (continued):
– Quality Assurance
– Quality Assurance
• 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 siteappointed 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
p function of audible and visual ppatient safety
y equipment
q p
– Proper
– Center frequency tests
– SNR
– Image uniformity
– Artifact assessment
– Deviations from established thresholds must be documented and corrective
action taken where appropriate
http://www.intersocietal.org/mri/seeking/mri_standards.htm
http://www.intersocietal.org/mri/seeking/mri_standards.htm
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Intersocietal Accreditation Commission
Intersocietal Accreditation Commission
• Part I of the standard addresses (continued):
• Part II of the standard addresses:
– Quality Assurance
– Indications (body, cardiovascular, MSK, neurological, breast, MRA)
– Techniques
• 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
•
•
•
•
Positioning and coil selection
Appropriate 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.
http://www.intersocietal.org/mri/seeking/mri_standards.htm
http://www.intersocietal.org/mri/seeking/mri_standards.htm
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MR Accreditation Programs - E. Jackson
Intersocietal Accreditation Commission
Intersocietal Accreditation Commission
• Application
• 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 test
t t results
lt with
ith the
th phantom
h t
images.
i
– 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.
– 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),
abdomen,
bd
pelvis,
l i extremity],
i ] M
Musculoskeletal
l k l l MRI
MRI, N
Neurological
l i l MRI,
MRI MRA.
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
http://www.intersocietal.org/mri/seeking/case_studies.htm
http://www.intersocietal.org/mri/seeking/required_items.htm
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ACR Accreditation Programs
ACR MRI Accreditation Overview
– Purpose:
• to set quality standards for practices and to help
continuously improve the quality of patient care
• to be educational in nature
• History
–
–
–
–
–
1996 – ACR MR program accreditation launched
2001 – Initial MR QC Manual released
2004 – Q
QC Manual update
p
2005 – 3-T magnets included
2006 – Documentation of QC and annual system performance
evaluation required
– 2008 – Modular program introduced
– 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 Modular Program
ACR Accreditation Process Overview
Submission materials:
• Head
• Spine
• Musculoskeletal
• Body
• MR angiography
• Cardiac
Whole body
(brain, C-spine,
L-spine
L
spine, knee)
– Scanner information
– Most recent annual medical physicist performance report
– Personnel qualifications
q alifications and CME information
– Clinical images for each module submitted
– Phantom images with associated site scanning data form
– Most recent quarter of QC data
– $$$$
“Every unit must apply for all modules routinely performed on
that unit for a facility to be accredited.”
Note: Breast MR accreditation is included in the Breast Imaging
Accreditation program
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MR Accreditation Programs - E. Jackson
ACR CME Requirements
ACR MRAP Cost
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Accreditation – First Unit
$2400 (1-4 modules)
$2600 (5 modules)
$2800 (6 modules)
Accreditation – Second Unit
$2300 (1-4 modules)
$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
26
Clinical Images
Clinical Images
Examination Choices for MRAP by module:
Examination Choices for MRAP by module:
- see “MRI Accreditation Program Requirements” file on ACR website, p. 12 of 15
- see “MRI Accreditation Program Requirements” file on ACR website, p. 12 of 15
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ACR Accreditation Process Overview
Clinical Images
Evaluated for
1) appropriate pulse sequence and contrast,
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.
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MR Accreditation Programs - E. Jackson
ACR Accreditation Process Overview
ACR Accreditation Process Overview
Phantom Images – Discussed in detail on subsequent slides
• 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
– Acquired on ACR MR Accreditation Phantom using specified
T1- and T2-weighted protocols plus the site’s T1- and T2weighted 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.
– SNR – all coils
– Uniformity – all volume coils
• Soft-copy displays (monitors)
– Should also provide an assessment of MR safety issues at the facility
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ACR MR Accreditation Phantom
ACR Phantom Scan Documentation
Contains information on:
• Phantom position
• Pulse sequences
q
to be used
• Filming and data preparation instructions
Sent to site with Full Application
Large Phantom: $1050
Small Phantom: $ 780 (Ortho)
Available from the ACR
(as of 2/10/2012)
http://www.acr.org/accreditation/mri/mri_qc_forms.aspx
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ACR Phantom Scan Documentation
Alignment of the ACR Phantom
Alignment is important!
Contains information on:
• Test analysis
• Performance criteria
• Common reasons for failure
• 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
Sent to site with Full Application
– make localizer images in all 3 planes
– use grid to check centering
Available from the ACR
http://www.acr.org/accreditation/mri/mri_qc_forms.aspx
• Record position for future use
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MR Accreditation Programs - E. Jackson
ACR Phantom Scans
ACR Accreditation Process Overview
• Sagittal Localizer
#1
#7
#8
#10
#11
– TE/TR=20/200ms, 25 cm FOV, 256x256, 1 20-mm, 1 NEX, 0:56
• ACR T1 Axial Series
– TE/TR
TE/TR=20/500ms,
20/500
25 cm FOV
FOV, 256x256,
256 256 11 55-mm slices
li
(graphically prescribed), 1 NEX, 2:16
#9
#5
• 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
#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)
• + Site T1 and T2 Axial Brain Series
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Geometric Accuracy
ACR T1
Slice 1
Slice Position
ACR T1 & T2
True Dimension: 190 mm
True Dimension: 148 mm
Sag Loc
Slice 5
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
Slice 1
49
Slice 11
Criterion:<5mm
50
Slice Thickness
Slice Thickness
ACR T1 & T2
Slice 1
Measurements:
• lower level to ½ average
• set window width to minimum
• measure lengths of top and
bottom ramps
• calculate slice thickness
Two 10:1 ramps
2 4x
•Magnify image by 2-4x.
•Define two ROIs, one on each
ramp.
•Obtain average intensity from
the two ROIs.
Criterion: 5.0±0.7 mm
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MR Accreditation Programs - E. Jackson
Spatial Resolution Matrix:
Registration with Phantom
High Contrast Spatial Resolution
ACR T1 & T2
Slice 1
• 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.
Resolution
Holes
UL
1.1
1.0 0.9 mm
Image
Matrix
LR
Image compliments of Geoff Clarke, PhD
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Low Contrast Detectability
Low Contrast: High vs. Low Field
ACR T1 & T2
0.3 T
1.5 T
Slices 8-11
Slice 8:
Slice 9:
Slice 10:
Slice 11:
1.4%
2.5%
3.6%
5.1%
≤1.5T
Criterion ≥ 9 spokes
3.0T
Criterion ≥ 37 spokes
Slice 11 - ACR T1 series
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Percent Image Uniformity
Ghosting
ACR T1 & T2
ACR T1
Slice 7
Slice 7
Ghost ratio =
|(top+bottom) - (left+right)|
(2  large ROI)
(~1 cm2)
Large ROI
(195-205 cm2)
≤1.5T
 (high  low) 
percent integral uniformity = 100   1 

 (high  low) 
Criterion: PIU  87.5%
Criterion:  0.025
3.0T
Criterion: PIU  82%
ROIs ~ 10 cm2 with ~4:1 length:width
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MR Accreditation Programs - E. Jackson
Ghosting
Common Problems and Artifacts
Window and level to
make sure ROIs are in
background noise!
(Warping of image space
due to gradient
nonlinearity corrections.)
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Potential Causes of Geometric
Accuracy Failures
•
Poor phantom positioning - relatively common problem
•
Poor gradient calibration
•
Bo inhomogeneity
•
•
Poor Positioning
Rotation (in-plane)
F
Ferromagnetic
ti objects
bj t in
i magnett
Poor magnet shimming
•
Gradient non-linearity (not appropriately corrected)
•
Inappropriate receiver bandwidth
•
Poor eddy current compensation
•
Combination of two or more of above
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Poor Positioning
Poor Positioning
Rotation (through-plane, RL)
Rotation (through-plane, AP)
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MR Accreditation Programs - E. Jackson
Sources of Geometric Distortion
Spatial Accuracy
• System Limitations
– Poor Bo homogeneity
Be sure to make sagittal
measurements at the center
of the phantom (or as close
as possible to the center).
– 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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Air Bubbles
Low Acquisition Bandwidth
When a large air
bubble is present in
the phantom,
geometric distortion
measurement may
have to be taken
along diagonal
instead of vertical.
Note distortion as
well as increased
susceptibility
artifacts.
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Spatial Resolution Matrix:
Registration with Phantom
Air Bubbles
Resolution
Holes
Image
Matrix
16 kHz
8 kHz
Image compliments of Geoff Clarke, PhD
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MR Accreditation Programs - E. Jackson
High-Contrast Spatial Resolution
Image Intensity Uniformity
Common causes of failure;
• Incorrect FOV or matrix size
• Poor
P
gradient
di t calibrations
lib ti
• Excessive filtering (smoothing)
• Poor eddy current compensation
• Gradient amplifier instability
Big ROI ~ 195 cm2
(19,500 mm2)
Small ROI’s ~ 1 cm2
(100 mm2)
Max Signal
Min Signal
ACR phantom - Slice #7
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Image Intensity Uniformity
Percent Signal Ghosting
Common causes of failure:
Poor phantom centering in coil (usually in AP direction)
Ghosting
Motion or vibration
Mechanical failure in head coil
• Must pass on slice #7 of ACR T1-weighted axial series.
• 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”
Note: Uniformity becomes poorer with increasing Bo (especially
above 2 T) because of dielectric field focusing phenomenon
(aqueous phantom).
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Ghosting is Nonspecific
Phase Ghosting
• Instability in MRI signal from pulse to pulse
NOISE
Phase
• Phantom motion
• Loose connections or bad cable
GHOST
GHOST
Readout
• Partial failure of radiofrequency coils or gradient subsystem
• Pulse sequence calibration error
– Eddy currents in Fast Spin Echo series
NOISE
Image compliments of Geoff Clarke, PhD
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MR Accreditation Programs - E. Jackson
Ghosting
Low Contrast Detectability
ACR T1 & T2
Ghosting may
obscure otherwise
visible LCD spokes
Slice 8:
1.4%
Slice 9:
2.5%
Slice 10:
3.6%
Slice 11:
5.1%
Image compliments of Geoff Clarke, PhD
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Low Contrast Detectability
DC Offset Artifacts
Some common causes of failure:
– Incorrectly positioned slices
Contrast based on partial volume averaging
Large artifact off to side.
NEX=1; frequency shifted
– Tilted phantom
– Incorrect slice thickness
– Ghosting
– Inadequate SNR
Image compliments of Geoff Clarke, PhD
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Susceptibility Artifacts
Details of the ACR MRI QC Manual
Small inclusions
in LCD insert can
make analysis
difficult.
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MR Accreditation Programs - E. Jackson
MRI QC Manual Overview
Quality Assurance Manual
Current Version: 2004
Should contain the following:
• Responsibilities and procedures for QC testing.
• Records of the most recent QC tests.
• A 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.
• Radiologist’s Section
Describes requirements and the role in
a QA program
• Technologist’s Section
Outlines the recommended daily and
weekly QC tests
• Physicist’s / MRI Scientist’s Section
Suggestions for setting up a QC
program
Outlines recommended annual
equipment performance tests
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Radiologist’s Responsibilities
Radiologist’s Responsibilities (cont.)
• To ensure adequate training and continuing education in
MRI
• To arrange staffing and scheduling so that QC tests can
be carried out.
• To provide an orientation program for technologists
• To provide feedback to the technologists.
• To ensure that an effective quality control program exists
for all MRI procedures
• To review the technologist’s test results
• To select the technologist to be the primary quality
control technologist
• To oversee or designate a qualified individual to oversee
the safety program.
• To ensure that appropriate test equipment and materials
are available to perform the technologist’s QC tests.
• To ensure that records are properly maintained and
updated in the MRI QC procedures manual.
• To
T select
l a qualified
lifi d medical
di l physicist
h i i or MRI scientist.
i i
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Technologist’s Responsibilities
Technologist’s Responsibilities
• Medical Physicist/MR Scientist interactions:
• Daily (weekly*) MR image QC procedures
– Physicist assures correct implementation an execution of the QC
procedures
– Physicist reviews QC notebook at least annually (quarterly preferred)
• QC of hard and soft copy images
• Routine visual inspection of equipment
• 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
• 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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MR Accreditation Programs - E. Jackson
Medical Physicist’s Responsibilities
Details of the Technologist’s
Responsibilities
• Write purchase specifications
• Perform acceptance testing and establish baseline QC
measurements
• Determine action limits for measured parameters
• Setup daily/weekly QC tests
• Perform annual MRI equipment performance reviews
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Technologist’s Section
Technologist’s Section
• Identification of the designated QC technologist(s)
• Maintenance of the QC Notebook
– Q
QC ppolicies and pprocedures
– 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
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Technologist’s Section
Technologist’s Section
• Routine tests using ACR phantom and ACR T1-weighted
head scan:
– Center frequency
– Geometric and ppositioningg accuracyy
– Image quality
(daily/weekly)
((daily/weekly)
y
y)
(daily/weekly)
17 min
• High contrast resolution
• Low contrast object detectability
– Artifact evaluation
(daily/weekly)
• Plus:
– Processor sensitometry
– Physical and mechanical inspection
(weekly)
(weekly)
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MR Accreditation Programs - E. Jackson
Technologist’s Section
Technologist’s Section
Daily (Weekly)
Daily (Weekly) (cont)
– 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 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)
– 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.
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Daily Tests - Transmitter
Gain and Frequency
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 min
• During the prescan for the T1 series, the scanner determines
the appropriate transmitter gain (or attenuation) and transmit
(center) frequency.
• On some scanners, these
h
values
l
are easily
il obtained
b i d at the
h
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.
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Daily Tests - High Contrast
Spatial Resolution
Daily Tests - Geometric Accuracy
True Dimension: 190 mm
• 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.
True Dimension: 148 mm
UL
1.1
1.0 0.9 mm
Sag Loc
Slice 5
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)
LR
Criteria: ± 2 mm
99
100
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MR Accreditation Programs - E. Jackson
Daily Tests - Low
Contrast Detectability
Daily Tests - Assessment of Artifacts
Count and record the number
of spokes in the slice
determined by the Medical
Physicist or MR Scientist.
(Typically
(T i ll slice
li 11 for
f low
l
field and slice 8 or 9 for high
field.)
• Look at all slices from the localizer and axial T1 series.
• Modify window width and level to look for ghosting
artifacts
if
andd radiofrequency
di f
interference
i
f
artifacts.
if
• Note any change in image quality relative to baseline
scans.
Action criteria:
Change of more than 3 spokes
(or as determined by QC
procedure).
101
102
Technologist’s QC Log - Daily Tests
Weekly Tests - Processor QC
Weekly
y Tests
SMPTE Pattern Gray
Level Ring
103
104
Weekly Tests - Processor QC
Weekly Tests - Processor QC
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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MR Accreditation Programs - E. Jackson
Weekly Tests - Visual Inspection
RF Shielded Room Door
At least weekly visual inspection tests:
• The RF door “fingers” provide
good electrical contact of the
shielded door and the rest of
g shield.
the Faradayy cage
• Check patient table, patient communication, patient “panic
buttons”, transport, alignment, and system indicator lights
• Check RF room integrity (particularly RF doors)
• 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!).
• 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
109
RF Coil Weekly Checks
• Be sure to check all cables on
RF coils, particularly high use
and/or flexible coils.
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
Some Details of the Medical Physicist’s
/ MR Scientist’s Responsibilities
• 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
113
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MR Accreditation Programs - E. Jackson
Medical Physicist/MR Scientist
Responsibilities
Medical Physicist/MR Scientist
Responsibilities
• Performs acceptance tests
– New systems before first patient scan
– Following any major hardware or software upgrade
• Laser camera QC
– Establish operating levels (in consultation with laser film
system service engineer)
• Acquires baseline QC data acquisition and establishes
action limits
–
–
–
–
–
• Acquire baseline data (using SMPTE test pattern)
Central frequency
Transmitter gain / attenuation
Geometric accuracy
High contrast resolution
Low contrast object detectability
• Corrective actions
– Determination of whether problem lies in the camera,
processor, and/or MR system
• Artifact analysis
114
115
Medical Physicist/MR Scientist
Responsibilities
Magnetic Field Homogeneity
Annual Physics Tests
–
–
–
–
Ideal Homogeneity
Magnetic field homogeneity
Slice position accuracy
Slice thickness accuracy
RF coil
il checks
h k
Poor Homogeneity
FWHM
FWHM
• Signal-to-noise ratio (all coils)
• Image uniformity (volume coils)
–
–
–
–
Good Homogeneity
o
Interslice RF interference
Phase stability (ghosting)
Soft copy displays (monitors)
Assessment of MR safety program
Denotes a totally
uniform magnetic field.
All signal is at resonant
frequency, o.
116
o
o
Fourier transform of
signal produces a
Lorentzian peak in
well-shimmed
magnet
Magnet field
homogeneity can be
characterized using
FWHM of resonance
peak
117
Magnetic Field Homogeneity
Magnetic Field Homogeneity
One vendor’s “head
equivalent” phantom.
With sphere in head
coil, use manual
prescan.
p
can be
Insert sphere
used for homogeneity
test.
Adjust center frequency
twice to determine the
“full width at half
maximum” of the
spectrum.
(Remove sphere from
cylindrical “loader”
first. Place at
isocenter in head coil.)
118
119
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MR Accreditation Programs - E. Jackson
Magnetic Field Homogeneity
Magnetic Field Homogeneity
LVshim Report
Phase images from GRE
sequences with 10ms
difference in TE’s
Exam 50196, Series 2, Image 1
(Fri Jan 24 20:35:23 1997)
Sc
dw d = 200
00 Hz
Scan Bandwidth
Field of View = 50 cm
Phase and Unwrapped
Phase Images
The change in phase across
the phantom is proportional
to the inhomogeneity of the
magnetic field.
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.
120
121
Magnetic Field Homogeneity
Slice Position Accuracy
• 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.
Slice Spacing
Slice Position
• Alternative: Use the service engineer’s report on
homogeneity for your site records of homogeneity.
SLICE #11
SLICE #1
Crossed wedges should be of equal length
if position and spacing are accurate (and phantom is not tilted!)
122
123
Slice Thickness
MRI Equipment Performance Evaluation
Site &
Equipment
Data
Site: _____________________________
MRAP Number: ____________________
Date: ________
Serial Number: ___________
Equipment:
MRI System Manuafacturer: _________________ Model : ________
Processor Manufacturer
:
_________________ Model: _________
PACS Manufacturer:
Measurements:
_________________ Model: _________
ACR MRAP Phantom Number used: _________
1. Magnetic Field Homogeneity
Bo
Homogeneity
• lower level to ½ average
• set window at minimum
• measure lengths of top and
bottom ramps
• calculate slice thickness
Method Used (check one): Spectral Peak ___
Phase Difference ___
Other (desc ribe) __________________________
Measured Homogeneity:
Diameter of Spherical
Volume (cm)
Homogeneity
(ppm)
________
________
________
Slice Position
Accuracy
Slice Thickness
Accuracy
124
_______
_______
_______
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
______
Bottom
______
(fwhm in mm)
Thickness (mm) ______
Duplicate these forms so they will be available for repeated use.
19
Calculated slice
MR Accreditation Programs - E. Jackson
Volume Coils SNR, Uniformity, and Ghosting
Volume RF Coil Measurements
• Uniformity performance criteria: PIU  90%
Must assess
SNR,
uniformity, and
ghosting
h i ratio
i
for every
volume coil.
 (high  low) 
percent integral uniformity = 100   1 

 (high  low) 
• SNR (no fixed criteria)
(Mean Signal ROI) / (SD of Noise ROI)
• Percent Signal Ghosting
  Left  Right   Top  Bottom  
ACR
Phantom
Slice #7
100  


126
2  Mean Signal
127
Phased-Array Coils
Breast
Phased Array



Phased-Array Coils
Wrist
Phased
Ph
dA
Array
Torso
Phased Array
Example of a particular vendor’s C-T-L spine phased array coil QC
phantom
Head-Neck-Spine Phased Array
128
129
Surface RF Coil Measurements
Volume Coil Data
% Image Uniformity
Max Signal
Min Signal
Signal-to-Noise
Mean Signal
SD of Background Signal
Percent Signal Ghosting
Ghost Signal
M
Mean
Si
Signall
Background Signal
Maximum Signal-to-Noise
Maximum signal
SD of Background Signal
Surface Coil Data
130
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MR Accreditation Programs - E. Jackson
Soft Copy Displays
4 . RF Coil Perform ance Evaluation
A. VOLUME R F CO IL RF Coil D escription: __________________________ Date: ____________
Phantom Description: ___________________________________________
Volume Coil
Pulse Sequence:
degrees
Type: ____
FO V: _____ cm
2
TR: _____
TE: ______
flip angle _____
Matrix: ___________ BW : _________kHz ; N SA ___
Slice thickness ______m m; spacing _______ mm
Calculated Values:
Uniformity
SNR
Ghosting
TX attenuation (or gain) __________
Data Collected:
Mean
Signal
M axim um
Signal
Minim um
Signal
Background
Signal
Noise
Standard
Deviation
G host
Signal
• Requires precision luminance meter
Calculated Values:
Signal-to-Noise
Ratio
Percent
Image Uniformity
Percent
Signal G hosting
B. R F SU RFACE CO IL -
• Four tests:
RF Coil D escription: __________________________ Date: ____________
Phantom Description: ___________________________________________
Pulse Sequence:
Surface Coil
Calculated Value:
Maximum SNR
Type: ____ TR : _____ TE: ______ FO V: _____ cm
–
–
–
–
2
Matrix: ___________ BW : _________kHz ; NSA ___
-
Slice thickness ______m m; spacing _______ mm
TX attenuation (or gain) __________
M axim um
Signal
Noise Standard
D eviation
Image uniformity distribution O K?
________
Image ghosting O K?
________
HARD CO PY IMAG E:
W indow width ________
Maximum Signal-toNoise Ratio
Maximum and minimum luminance
Luminance uniformity
Resolution (SMPTE)
Spatial accuracy (SMPTE)
W indow level _______
Several copies of this page m ay be required to report on all RF coils.
133
Soft Copy Displays
5. Interslice RF Interference
Phantom Description: ___________________________________________
Pulse Sequence:
Type: ____ TR: _____ TE : ______ FOV: _____ cm
2
M atrix: ___________ BW : _________kHz ; NSA ___
RF Slice
Interference
S li c e
Gap
(m m )
10 0 %
S i g na lto - N o i s e
R a tio
M e a sure d SNR
• Max luminance (WL/WW min): 90 Cd/m2
Number of slices______
S e rie s
Num ber
1
2
90 %
80 %
3
• Min luminance: <1.2 Cd/m2
4
• Luminance uniformity: Each of the
lluminance
minance values
al es obtained at the fo
fourr
corners of the screen should be within 30%
of the maximum value measured at the
center (WL/WW min).
70 %
0%
25 %
50%
7 5%
1 00 %
In te r- sl ic e G a p (p e r c e n t o f sl ic e th ic k n e s s )
6. Soft Copy Displays
M onitor Description: __________________________________________
Soft
S
ft Copy
C
Displays
-2
2
M axim
i um L
Luminance:
i
________________________ Cd m .
-2
M inim um Luminance: _________________________ Cd m .
Lum inance Uniform ity:
-2
Average of values obtained in four corners of screen: ______ Cd m .
Lum inance measured in center of screen:
-2
______ Cd m .
Percent difference: ________ %
-
Review of
Routine QC Program
• Resolution: Use SMPTE 100% contrast
patterns (see QC manual, p. 117).
• Spatial accuracy: Use SMPTE grid pattern
(see QC manual, p. 117).
|(Center – Average Corners)/(Center) x 100% < 30% |
7. Evaluation of Site’s Technologist Q C Program
4) Set up and positioning accuracy:
(daily)
5) Center Frequency: (daily)
6) Transm itter Attenuation or G ain: (daily)
7) Geom etric Accuracy M easurements: (daily)
_________
_________
_________
_________
8) Spatial Resolution Measurem ents: (daily)
_________
9) Low Contrast Detectability: (daily)
_________
10) Film Q uality Control (weekly)
_________
Visual Checklist: (weekly)
_________
134
ACR MRI QC Program Summary
M RI Equipm ent Evaluation Sum m ary
Site ___________________
Report Date: __________
System MRAP #_____________ Survey Date: __________
M RI System Manufacturer ___________ Model: __________
Physicist/M RI Scientist: ____________________
Signature: ________________________________
• Technologist
Equipm ent Evaluation Tests
Summary
Sh t
Sheet
1. Magnetic Field Homogeneity:
2. Slice Position A ccuracy
3. S lice Thickness Accuracy
4. RF Coils’ Performance
a. Volume Coils’ S ignal-to-Noise Ratio
b. Volume Coils’ Image Uniformity
c. V olum e Coils’ Ghosting Ratios
d. Surface Coils’ Signal-to-Noise Ratio
5. Inter-slice RF Interference
6. S oft copy displays
P ass / Fail
_________
_________
_________
– Performs daily (weekly) tests to assess image quality using the
ACR phantom
– Performs weekly tests of hard copy output
– Maintains
M i t i QC notebook!!
t b k!!
_________
_________
_________
_________
_________
_________
M di l Ph
Medical
Physicist’s
i i t’ or MRI S
Scientist’s
i ti t’ R
Recom m endations
d ti
for
f
Q uality Im provem ent:
______________________________________________
______________________________________________
______________________________________________
______________________________________________
______________________________________________
______________________________________________
______________________________________________
______________________________________________
______________________________________________
• 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
137
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MR Accreditation Programs - E. Jackson
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.
138
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