MRI & Interactions

Magnetic Resonance Imaging (MRI) is an innovative diagnostic tool for almost every clinical specialty. Unlike CT or X-ray angiography, no ionizing radiation or iodine contrast agents are necessary. As a consequence, there has been a large increase in the number of MRI procedures.

The MR scanner market is growing rapidly, not only with the most common field strength of 1.5 T, but also with a tendency towards the use of higher static magnetic field strengths such as 3 T, 7 T and beyond. MRI is considered as one of the safest non-invasive imaging modalities. However, it is based on strong static magnetic fields and switched gradient magnetic fields in the frequency range of several kilohertz (kHz), as well as on electromagnetic fields in the radio frequency (RF) band (MHz).

Besides acceptable and reversible side effects like nausea, vertigo, phosphenes (flashes of light) or a metallic taste, performing MR scans of humans with implants or while using medical instruments can lead to unintended and dangerous interactions. This causes safety and diagnostic problems.

Among the products at issue are

  • vascular implants (e.g. stents, clips, coils, valves)
  • orthopedic implants and devices (e.g. hip prostheses, nails, wires, fixation systems)
  • active implants (e.g. pacemakers, neurostimulators, infusion pumps, pressure sensors)
  • surgical/interventional instruments (e.g. scissors, guidewires, manipulators)
  • medical electrical devices (e.g. pulse oximeters, anaesthesia and monitoring equipment, injectors, ventilators, robotic systems)

and all ancillary equipment used within the MR environment. These devices are also described in the book chapter “Devices and Materials in MRI” by Gregor Schaefers and Andreas Melzer in the Springer Handbook of Medical Technology (2011).

The MR safety of the patient and the device can be compromised by magnetically induced displacement forces and torque, RF-induced heating, gradient-induced heating, RF-induced or gradient induced voltages, gradient induced vibration, unintentional output and operational inhibition (device malfunction). Further, MR compatibility issues can occur, caused by materials that generate MR image artifacts and thus decrease the quality of the MR image. This can lead to diagnostic inaccuracies or misinterpretations and result in a significant lack of information and difficulties with follow-up exams.

In order to protect the patient and the user as well as the equipment from dangerous MR interactions, intensive MR tests need to be performed according to standardized methods (mainly ISO/TS 10974 or ASTM standards). The aim for our comprehensive MR testing service is to provide substantial and meaningful MR labeling information for medical implants, medical instruments and other medical devices.