MRI tools for HP X-nuclei

This work package will provide the technical means for efficient translation of basic research performed in WP1 and WP2 to preclinical validation performed in WP4. In addition, this WP provides the technological basis for widespread use of HP MRI on any clinical MRI scanner.

Task 3.1: Multi-nuclei MR coils

We will design and build dual tuned coils for 15N/1H (operating at 7T and 1.5T). These coils are required for data acquisition in the initial phase of the project. In addition, rapidly switchable coils enabling the quasi simultaneous acquisition of multi-nuclear signals in combination with a dedicated T/R unit established in Task 3.2 will be developed.

Task 3.2: T/R system optimised for HP MRI

A low-cost dedicated transmit/receive system will be developed, which will be interfaced and synchronised to the MR systems produced by different vendors by a simple electrically isolated trigger line. In the first instance, a receive-only system will be set-up enabling interfacing of the dedicated coils developed in Task 3.1 independent of the vendor of the MR system. The system will comprise a fast digitiser that enables sampling of the MR signal with at least 250MS/s and a coil interface capable of rapid switching times below 5µs. In a second step, the receive-only system will be extended by multi-channel transmit capabilities, enabling simultaneous multi-nuclear excitation. In the timeframe of the project, the system will be equipped with independent transmit surface coils.

Task 3.3: Polarisation transfer framework

We will develop 15N to 1H polarisation transfer pulse sequences utilising dual tuned coils that allow simultaneous excitation of 15N and 1H including a reverse INEPT sequence, partial transfer of polarisation (for more efficient transfer using cross-polarisation), B1-insensitive pulses sequences, and sequences that use gradients for coherence selection that improve water suppression. The polarisation transfer protocols developed will be combined with the dedicated data acquisition protocols developed in Task 3.4 and the dual-tuned coils interfaced to the different MR systems by the T/ R system developed in Task 3.2.

Task 3.4: Efficient sampling strategies and motion compensation

We will focus on low-discrepant acquisition strategies (e.g. Seifert spiral) efficiently filling 3D-kspace, enabling  short echo times and self-gating, and providing non-coherent aliasing artefacts, which are thus well suited for sparse reconstruction techniques. Where simultaneous images of multi-nuclear data are not possible (gradient demands), a simultaneously acquired 1H signal will be used for deriving self-gating data for motion compensated reconstruction. Further, sampling strategies (e.g. sampling the multi-nuclear signal quasi-simultaneously) will be investigated for simultaneous acquisition of 1H (anatomy) and multi-nuclear (functional) data. The techniques will be designed and implemented on pre-clinical MR systems operating at 7T (Agilent; UCAM, UOXF) and a clinical scanner at 3T (Philips Achieva, UU). Further, the techniques will be tested on 3 cryogen-free preclinical scanners (1.5T, 3T, and 7T, at RS2D and HMO).