MRI coil failures can be difficult to detect during standard QA. Ted Lucidi, CBET, explains how advanced test fixtures support diagnostics and what HTM professionals can watch for in the field.
MRI coil reliability is built long before a device reaches the field—but when failures occur, healthcare technology management (HTM) professionals are often the ones troubleshooting without access to the specialized test fixtures used during manufacturing or repair.
In this Q&A, Ted Lucidi, CBET, director of commercial operations and business analytics at Innovatus Imaging, explains how coils are designed, validated, and tested during manufacturing using fixtures that simulate scanner conditions and stress-test individual components with precision. Lucidi also walks through real-world failure scenarios HTM teams face in the field—from cable degradation to flex coil breakdowns—and shares strategies for diagnosing intermittent issues.
His insights offer a look at how engineering-level testing connects with clinical troubleshooting in the real world.
24×7: To start, most HTM professionals are familiar with MRI coils in terms of functionality and replacement but not necessarily how they’re designed and tested during manufacturing. One surprising point you raised in a recent blog is that many coils aren’t actually tested on an MRI scanner before being shipped. Why is that the case, and how do manufacturers ensure performance without real-world testing?
Lucidi: Let’s take a step back into the design phase of an MRI coil. A coil’s electronic design, its inputs, outputs, performance specifications, etc, are all developed using benchtop-type test equipment. Engineers design and produce specific test devices (or fixtures) to make the testing process highly consistent, very repeatable, precise, accurate, and efficient. The coil model’s design will undergo an extremely well-designed verification and validation process, which includes thorough testing in an MRI environment.
Once the coil’s design has been approved and it is moved into production, coil performance can be assessed using test fixtures similar to those used by the design engineers. Assemblers and QA personnel in manufacturing thoroughly test each coil produced, comparing measured values to the engineering specifications.
As long as a specific serialized coil’s measured values fall within acceptable ranges, the coil is approved for release to sell. Similar processes are used throughout device manufacturing. To perform system testing on every MRI coil during final assembly, once the design has been proven, would be cost-prohibitive and highly inefficient. Â
24×7: Since only a small sample of coils might typically be tested in an MRI environment before release, what are the implications for HTM professionals working with coils in the field?
Lucidi: For factory-new coils, the risk is extremely low. Remember, the overall performance of every coil has been thoroughly assessed, and the results have been very well documented prior to release. During the installation of a new magnet, the purchase of a new/replacement coil, or during routine preventive maintenance, each coil undergoes a thorough QA test using the magnet in the clinical setting. Additionally, MRI technologists perform routine QA tests on their coils. If a QA test fails, some type of corrective action would be required by either the on-site HTM team, an independent service provider, or the OEM.
24×7: From a troubleshooting perspective, how might issues arise in clinical settings that weren’t detected during initial manufacturing tests? Are there specific scenarios where this happens?
Lucidi: In our experience, the warranty rate on factory-new coils is extremely low. Although the number of out-of-box coil failures is minimal, they can and do occur. One example could be accidental damage during packaging, shipment, unpacking, or during the initial installation. As mentioned, the service rep installing the magnet, as well as the MRI technologists during routine QA testing, would identify any performance problems prior to clinical use and take the appropriate action.
24×7: When it comes to testing coils after they’ve failed in the field, test fixtures can be used to isolate and stress-test individual channels. How does this process work, and what kind of issues does it help uncover that might not be obvious with a general visual or functional check?
Lucidi: Test fixtures, or proprietary testing devices, used in repair [at specialized facilities] are very similar, if not identical to, those [used during the manufacturing process]. Some of the test fixtures are model-specific, and others are designed to accommodate multiple coil models—such as all of the various coils that connect to a particular MR system. The test fixtures enable each coil to be interrogated just as if it were connected to the MR system itself. But, the fixtures go much further.Â
Certain fixtures physically stress the coil, others interrogate system cables, and more yet diagnose failures to ID circuitry. Repair technicians use devices that emulate how the scanner dynamically enables/disables various circuitry in a coil. They can isolate individual circuits and verify that circuit’s performance. The test fixtures, like those described above used during manufacturing, enable testing in a thorough, consistent, efficient, and quantifiable manner.
The main benefit of this method (over testing on an MR system) is that repair techs can stress test the entire coil in a very thorough and efficient manner. System testing may not allow for repeated or stress testing without following a pre-defined protocol, which in turn may limit options.
24×7: Cables seem to be a recurring pain point in coil performance. What are some of the most common failure modes in coil cables, and how can HTM teams recognize when a cable—not the coil itself—is the root of the problem?
Lucidi: Almost every device with a cable (medical or commercial) will experience wiring breakdowns over time. Cables and wiring harnesses are only viable for X-number of flexes. Add to this that cables can become trapped in mechanisms, rolled over, accidentally pulled, etc. We’ve all experienced this. With MRI coils, some of the wires in the cable are related to the signal; others are related to control. When a cable begins to break down, end-users may report intermittent performance problems or intermittent error codes.Â
If one or more of the signal lines becomes compromised, end-users would typically report a problem with image quality or the appearance of image artifacts. If a control line fails, end-users might report an error code. With cable degradation, performance may worsen or actually resolve itself based on the positioning of the cable. Over time, performance may degrade to a point where the coil fails its daily/routine QA tests, resulting in a hard failure.
24×7: Flex coils are another area prone to intermittencies. What makes these particularly vulnerable, and how should HTM professionals approach evaluating them during a service call?
Lucidi: For those not familiar with flex (or flexible) MRI coils, these are coils with a lightweight, very flexible design, which allows users to drape them over or wrap them around a particular region of interest or body part. Flex coils experience higher-than-expected failures just based on their design. They are designed by mounting electrical components to a series of very thin, flexible copper traces and then covering them with or embedding them in foam.Â
Just like a cable, a flex coil can only bend X-number of times before a breakdown. Add to this that, occasionally, flex coils are wrapped too tightly around a body part, inducing premature failures. Some users make the mistake of carrying or supporting the coil by the foam, versus using the correct locations. This can result in tearing of the foam and even the flexible copper traces. Flex coil failures will present themselves in manners similar to cables—intermittent performance problems based on positioning.
24×7: As cable and flex coil failures can result in intermittent performance issues, how can these be properly identified and diagnosed?
Lucidi: This is an area where the use of custom test fixtures has benefits over system testing. The test fixtures that engineers design enable repair technicians to perform real-time monitoring and stress testing of every wire in the system cable. Technicians are able to flex, pull, and reposition the cable, all while monitoring the performance of every wire in the cable assembly, live. Testing is thorough, accurate, and highly efficient.
The same type of live interrogation can be performed on a flex coil. Relying on system testing may not allow for this level of interrogation. Although it’s possible to identify intermittent issues via system testing, it can be time-consuming.
24×7: Lastly, while most facilities don’t have access to specialized coil test fixtures, are there practical steps or diagnostic tools HTM professionals can use to approximate this kind of testing and improve troubleshooting accuracy.
Lucidi: Unfortunately, there are no field-based tools that offer an efficient means of thoroughly interrogating the performance of a coil. Service reps might be limited to using tools similar to those used by end-users to run daily/routine QA tests.
Some of the best tools are our senses, and a thorough visual and tactile inspection is a great starting point. Look for damaged connections or worn interconnects between multi-piece coils. Look for missing hardware or physical damage. Look for and feel for excessive wear to a cable or strain relief. Look for tears to or breaks in the foam on a flex coil. Preventively, observe how the end-users store their coils, how they’re handled, how the cable is routed during the study, and even how tightly a flex coil is wrapped around a body part.
In summary, there are over 1,000 unique models of MRI coils. The sheer cost of owning, operating, and maintaining a fleet of MR systems to test such a vast variety of coil models would be highly cost-prohibitive. The use of custom test fixtures for MRI coil development, manufacturing, and repair has been verified, validated, and proven highly successful since the technology’s commercial release in the 1980s.
Photo caption: Repair of large, complex MRI coil
Photo credit: Innovatus Imaging
