Design and construction of a PET-compatible double-tuned 1H/31P MR head coil
2nd April 2021
A. Avdo Celik, Chang-Hoon Choi, Lutz Tellmann, Claire Rick, N. Jon Shah, and Jörg Felder
The ability to acquire information relating to metabolic processes in the body using PET while simultaneously using MRI to obtain anatomical/functional information is extremely beneficial as it improves diagnostic accuracy, saves time and patient discomfort and helps in understanding the functional, hemodynamic, and metabolic interactions within various neurological disorders.
The depth of information acquired using simultaneous MR-PET can be further optimised with the use of a double-tuned MR coil capable of obtaining a signal from various 'X-nuclei' known to be potential biomarkers, such as sodium-23 (23Na) or phosphorus-31 (31P), alongside traditional 1H proton imaging.
However, while the benefits of such a comprehensive and dynamic imaging system are clear, it is necessary to reconcile a number of trade-offs between the modalities. These include the use of shields and special components to limit the effect of the strong magnetic field on the PET system and to limit the effect of the PET signal processing electronics on the MR images. In addition, special consideration also has to be given to the double resonant nature of the coil so as to avoid coupling between elements, which results in a weak signal to noise ratio (SNR) for the second nucleus.
In response to these technological challenges, this research brings together the benefits of simultaneous MR-PET imaging along with the additional benefits afforded by multinuclear MRI with the development of a PET-transparent double-tuned 1H/31P head coil suitable for use in an MR-PET system at 3T. The results show that this coil can be operated at both resonance frequencies and with only a negligible penalty on the PET count rate loss.
The major benefits of the coil are the result of an optimised geometric layout, the choice of case materials and the careful selection of coil conductor materials and thicknesses. By applying the aforementioned principles, the investigations performed show that the coil is well suited to an MR-PET system. Moreover, in MR operation, it provides high SNR for both nuclei, which is a crucial design goal, even when building MR- only, double-tuned coil systems.
Having demonstrated good performance in phantom investigations, the next step is to obtain clearance for in vivo investigations.
Origional publication:
Design and Construction of a PET-Compatible Double-Tuned 1H/31P MR Head Coil