Quality Control: MRI/Breast MRI (Revised 4-24-2020)
Modified on: Fri, 24 Apr, 2020 at 2:18 PM
The MR equipment specifications and performance shall meet all state and federal requirements. The requirements include, but are not limited to, specifications of:
Maximum static magnetic field strength
Maximum rate of change of magnetic field strength (dB/dt)
Maximum radiofrequency power deposition (specific absorption rate)
Maximum auditory noise levels
The ongoing QC program assesses relative changes in system performance as determined by the technologist, service engineer, qualified medical physicist/MR scientist, or supervising physician. A qualified medical physicist/MR scientist must have the responsibility for overseeing the equipment quality control program and for monitoring performance upon installation and routinely thereafter. All ACR MR accredited facilities and those applying for accreditation must maintain a documented quality control (QC) program and must comply with the minimum frequencies of testing outlined in the 2015 ACR MR Quality Control Manual. The ACR will send a QC manual to the modality’s supervising physicians of facilities not previously accredited in MRI. There are no QC tests specific to breast MR accreditation, as distinct from those required for general MRI accreditation.
As part of the accreditation application, facilities must demonstrate compliance with ACR requirements for QC by providing:
The most recent annual MR system equipment performance evaluation summary form signed by a qualified medical physicist - for Breast MR, this must include an indication that the performance of the site’s bilateral breast coil(s) has been checked and was acceptable
Documentation of corrective action (if the annual MR system performance evaluation summary identifies performance problems)
Breast MR: If your facility has already submitted your medical physicist’s MRI Equipment Evaluation Summary Form and MR Safety Checklist for a given unit when accrediting in the general MRI accreditation program, your medical physicist/MR scientist does not need to repeat the MRI Equipment Evaluation survey specifically for breast MRI as long as the breast coils were checked during the survey. However, you must submit the MRI Equipment Evaluation Summary Form and MR Safety Checklist for Breast MRI Accreditation, even if it was submitted previously for general MRI accreditation. The ACR will check to ensure that the unit has been surveyed within the past year.
Although many of the procedures and action criteria outlined in the 2015 ACR Magnetic Resonance Imaging (MRI) Quality Control Manual were written specifically for the ACR MRI Accreditation Phantom, the ACR understands that the use of this phantom may not be possible for all QC in breast imaging. Some facilities use the ACR Small MRI Phantom for this purpose. The ACR leaves the choice of the QC phantom and the resultant action criteria to the facility. This decision must be made by the qualified medical physicist/MR scientist in cooperation with the system vendor. An order form and more information about the ACR small phantom are available through the ACR.
Acceptance testing is intended to measure quantifiable system parameters, which may then be compared to the manufacturer’s specifications and used to develop baseline performance. A complete evaluation of system performance should be conducted by a qualified medical physicist (QMP)/MR scientist after completion of installation and prior to patient imaging. This testing should be more comprehensive than periodic performance testing and should be consistent with current acceptance testing practices. It should include all of the technologist’s QC tests as well as the annual tests in the 2015 ACR Magnetic Resonance Imaging (MRI) Quality Control Manual and an evaluation of all coils, including all breast imaging and biopsy coils. Useful guidance is also available in a report from the MR Subcommittee Task Group of the AAPM.
Annual Medical Physicist/MR Scientist Survey
All facilities applying for accreditation or renewal must demonstrate compliance with the ACR requirements for QC by including a copy of the facility’s most recent Annual MRI System Performance Evaluation Summary (must be performed and signed by a medical physicist/MR scientist and must include evaluation of the weekly technologist QC and MR Safety Program Assessment). A technologist may perform the ACR phantom portion of the accreditation submission, although the ACR strongly recommends the services of a medical physicist or MR scientist for this also. The medical physicist/MR scientist must provide a written report of findings of acceptance testing and performance evaluations to the responsible physician(s) and to the professional(s) responsible for service of the MRI equipment. If appropriate, the medical physicist/MR scientist should inform the site supervisor of the required service. Written reports must be provided in a timely manner consistent with the importance of any adverse findings. If use of the equipment poses imminent danger to patients or staff, the medical physicist/MR scientist must take immediate action to preclude use of the equipment. Compliance with this requirement will be checked during the unannounced site visits that will be conducted by the ACR and/or the CMS.
The ACR realizes that surveys cannot usually be scheduled exactly on the anniversary date of the previous survey; therefore, a period of up to 14 months between surveys is acceptable. If the facility has been conducting QC for less than one quarter, the facility will submit whatever they have on these forms.
Additionally, if the Annual MRI System Performance Evaluation and/or QC files show performance deficits (e.g. problems with the system and/or data outside of the action limits), the facility must state what steps it has taken to correct the problems.
All QC testing must be carried out in accordance with the written procedures and methods outlined in the ACR 2015 MRI Quality Control Manual. The evaluation must include, but is not limited to, the following:
Annual Medical Physicist's/MR Scientist's MR System Performance Evaluation
Magnetic Field Homogeneity
Checks the uniformity of the main magnetic field strength (B0) over a designated volume. Inhomogeneities can contribute to geometrical distortion of images, adversely influence image quality, and compromise the signal-to-noise ratio (SNR) in some fast imaging sequences.
Slice Position Accuracy
Checks the accuracy with which axial slices are positioned at specific locations utilizing a sagittal localizing image. The test determines whether the actual locations of acquired slices differ from their prescribed locations by substantially more than is normal for a well-functioning scanner.
Slice Thickness Accuracy
Checks the prescribed slice thickness against that of the measured slice thickness. Poor slice thickness accuracy may not only suggest that slices are too thick or thin, but can extend to factors such as incorrect image contrast or SNR.
Radiofrequency Coil Checks
Checks the trade-off between maximizing image uniformity and enhancing SNR that is inherent to various types of radiofrequency coils. Tests should be performed on all coils used clinically (including breast coils) and include:
- frequency and gain/attenuator verification (pre-scan values)
- image SNR
- intensity uniformity for volume coils
- phase stability and image artifact assessment
Soft-Copy Displays (Monitors)
Checks that display devices meet manufacturer’s published specifications for
- maximum and minimum luminance
- luminance uniformity
- spatial accuracy
Evaluation of QC Program
Provides an external assessment of QC, checks that appropriate actions are taken to correct problems, identifies areas where quality and QC testing may be improved and enables a comparison of QC practices with those of other MRI sites.
Continuous Quality Control
A continuous QC program must be implemented for all MRI units and should be established with the assistance of a qualified medical physicist/MR scientist. The technologist must perform the QC tests listed below at a weekly minimum frequency. The medical physicist/MR scientist should identify the person responsible for performing the tests and may choose to increase the frequency of testing based on the facility and MRI usage. If any QC parameter being monitored falls outside of the control limits, corrective action should be taken. A medical physicist/MR scientist should be available to assist in prescribing corrective actions for unresolved problems. The technologist weekly QC program must include, but not be limited to, the following:
Annual Medical Physicist's/MR Scientist's MR System Performance Evaluation
To determine that the MRI scanner is functioning properly with regard to performing patient set up
Setup and Scanning
To determine that the MRI scanner is functioning properly with regard to performing data entry and prescan tasks
Center (Central) Frequency
To determine that the MRI system is set on-resonance; the effects of off-resonance relate primarily to system sensitivity and appear as a reduction in image SNR
Transmitter Gain or Attenuation
To determine whether there are problems with the radiofrequency chain (coil RF calibration)
To determine whether the geometric relationships of the MR image are in error (gradient calibration)
High Contrast (Spatial) Resolution
To assess the scanner’s ability to resolve small objects
Low Contrast Resolution (Detectability)
To assess the extent to which objects of low-contrast are discernible in the images
To assess the presence of artifacts that may be early indicators of declining MRI system performance
Film (Hardcopy Image) QC
To ensure artifact-free laser films are produced with consistent gray levels that match the image appearance on the filming console
To ensure the MRI system patient bed transport, alignment and system indicator lights, RF room integrity, emergency cart, safety lights, signage and monitors are present and working properly and are electrically and mechanically stable
If your facility does not have laser printer capability for Breast MRI, there is no need to perform QC for a laser printer. Just indicate that you do not use a laser printer when you complete the application.
Safety guidelines, practices, and policies must be written, enforced, reviewed and documented at least annually by the MR supervising physician. For guidance, see the ACR’s Manual on MR Safety and the ACR Manual on Contrast Media. The annual medical physicist/MR scientist performance summary must also include an assessment of the MRI safety program (signage, access control, screening procedures and cryogen safety) as well as an inspection of the physical and mechanical integrity of the system.
Preventive maintenance must be scheduled, performed and documented by a qualified service engineer on a regular basis. Service performed to correct system deficiencies must also be documented and service records maintained by the MR site.
Revision History for this Article
Description of Revision(s)
Article created; FAQs incorporated; No criteria changes
|4-24-2020||MRI Safety||Updated link to ACR Manual on MR Safety|
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