Diagnostics of radiofrequency MRI coils using magnetic loop probes

One of the most common causes of failure of medical equipment for magnetic resonance imaging is the malfunction of local radio frequency receive antenna arrays, called coils. These devices are normally located in close proximity to the patient's body inside the scanner bore and are exposed to the most intense operating conditions in combination with the influence of magnetic fields of various types. These factors greatly increase the risk of equipment damage, and a malfunction of these devices can lead not only to the inability to make a correct diagnosis, but also can be dangerous for patients due to the rising probability of radio frequency burns. The aim of our research is to develop methods for rapid diagnostics of medical radiofrequency equipment for magnetic resonance imaging to prevent its potential failure or quickly detect the source of problems if such a failure has already occurred. In our paper we propose a design of measuring sensors based on magnetic loop antennas for diagnosing multichannel coils commonly used in MRI. The proposed sensors can be used together with a vector network analyzer or a spectral analyzer with tracking generator and allows to measure several crucial parameters including operating frequencies of coil channels, the quality of resonance, the integrity of resonant circuits, the functionality of detuning circuits, and the level of parasitic coupling between coil channels. Our analysis of the coil designs used in MRI scanners from various manufacturers allowed us to determine the optimal parameters for antennas that allow us to use them on the widest possible range of medical devices currently available on the market. In addition, we developed recommendations for the application of measuring magnetic loops based on our practical experience and demonstrated examples of methods for diagnosing coil array channels. The designs of single and double-magnetic loop probes that we presented allow us to quickly check the performance of medical devices in a clinical setting, often even without the need to remove the housings or any disassembling work, which can play an important role in conditions of an acute shortage or limited access to qualified service for complex radiofrequency medical equipment.