Interventional MRI is a rapidly developing field which has proven immensely valuable as a navigation tool during surgery, as well as for real time or quasi-real time feedback for different therapies. Nevertheless, the current need for MR compatible devices, the close bore geometry of the scanners and the high costs are the price to pay when using conventional clinical scanners.

While working at low magnetic field regimes can help tackle these problems, further issues may arise because of the reduced signal harvesting capability and the dependence of specific markers on the magnetic field strength, such as susceptibility and proton resonance frequency shift. The latter, in particular, provides the gold standard method employed for MR thermometry and directly relies on the intensity of B₀, making it unsuitable for low magnetic fields. Alternative strategies must therefore be developed.

Here at the AMT Centre, we believe that the capability to image temperature is a very attractive feature of MRI and promises to be a game changer in thermal therapies. We have currently developed a fast temperature mapping sequence that relies on the increased T₁ dispersion achieved at low magnetic fields and on its dependence on temperature. Promising results were obtained in phantoms and we are working towards our first tests on real tissue.

Low-field MRI allows for much more flexibility for the tools used around or inside the magnet. Even when these instruments are not entirely non-magnetic, their impact on the MR image quality is greatly reduced with respect to higher-field scanners.

By exploring the combination of open geometries for the low-field magnets and the RF detectors together with fast imaging sequences, we envision new possibilities for MR-guided surgeries or therapies.