MRI Quality Control Program

Yearly Performance Evaluation and Acceptance Testing

Some sites object to the need for the ACR’s QA program which includes the need for yearly system performance evaluations. However, I have currently set up QA programs and performed the yearly performance evaluation on 20 magnets and have found it to be extremely useful. For example, as part of the initial system checkout, I found problems with the following RF coils:
4 CTL coils Anterior neck coil
3 Knee phased array coil 2 Flexible Body phased array coils
2 Shoulder phased array coils TMJ coil
3 Neurovascular coils Cardiac Phased Array
Extremity Coil 2 Peripheral Vascular Runoff coils
8-Channel Head coil
I also noted that four Medrad power injectors were overdue for calibration, found 5 scan rooms with RF shielding tabs broken off their doors and two scanners with severe geometric distortion. As part of my initial visit to a site I now check fringe fields. At the first site I made these measurements I found a 40 square foot area outside of their building with public access where the field ranged from 5 to 18 Gauss. At another site I found greater than 70 gauss in a public region outside of the building!
Beyond identifying clearly deficient RF coils, one of the most useful results of the yearly performance evaluation is establishing baseline performance for all your coils. Let’s say that 6 months after establishing this baseline, you notice a possible loss in signal quality. Simply pull out the most recent yearly report and repeat the testing done at that time. If the SNR has dropped or ghosting has increased you have a strong case to present to your service engineer to have him fix or replace the coil.
Magnetic Resonance Imaging is more complicated than all other imaging modalities combined. The scanners consist of many components that all must be working together properly in order to produce quality images. Although most sites have a service engineer perform periodic preventive maintenance (PM), these visits are usually very short and do not include testing every RF coil present. These periodic PM visits are analogous to changing your car’s oil every 3000 miles. A yearly performance can be compared to a complete checkup with a mechanic every 12000 miles.
A site can easily spend more than a million dollars to purchase and setup one of these scanners. The images obtained can have a profound affect on that site’s patients. A yearly performance evaluation is a small cost to pay to help ensure that you, and your patients, get the most from your investment.