Dr. Shaihan Malik, PhD is a Reader – Associate Professor of medical imaging/MRI physics at King’s College London currently involved in researching heating effects from radiofrequency waves at 7T, as well as Quality Assurance (QA) for clinical research and interventional MRI at a variety of field strengths.

A key reason for purchasing a Multisample120E phantom from Gold Standard Phantoms was to help with our research on heating effects at 7T and to be able to validate new coils used on this powerful scanner. With this phantom we can validate predictive models of heating effects via MR thermometry combined with temperature probes inserted directly into the phantom. By measuring temperature changes and relating it to the specific absorption rate (SAR), we can validate that a coil is behaving as expected, as part of our quality assurance procedures.

The process of purchasing the phantom was smooth, we communicated with the team about our requirements for MR thermometry including the placement of probes and custom reference points and worked collaboratively to find a solution. GSP also sent us a prototype that we were able to trial and send back for alterations before the phantom was finalised and purchased. Preliminary measurements show the phantom is working well and allows us to simultaneously take readings from the embedded temperature probes and perform MR thermometry. Moving forward we are finalising the MR thermometry protocol, and we plan to use this technique to validate safety models both commercially purchased coils (for off label use for example) or for those developed in-house by our RF Engineering lab, led by Özlem Ipek.

Our second research focus involves quantitative MRI and the Multisample120E allows us to validate the T1 and T2 mapping protocols as we have a known reference value in the vials for comparison. The Multisample120 is filled with a susceptibility matching fluid to avoid image distortions, and this is usually just water with some doping to change the relaxation times. However we have found that at 7T (i.e. 300 MHz) the high dielectric constant of water creates strong B1 homogeneity which then leads to poor performance of quantitative MRI methods. We have found the phantom to be very useful to investigate alternative replacements for a flood-fill liquid – we haven’t yet found a solution but hope to soon.

Dr Shaihan Malik, PhD, King's College London