Cryogenic Single and Array Coils for Magnetic Resonance Systems

Daniel Højrup Johansen

Research focus
In signal to noise (SNR) starved applications of nuclear magnetic resonance (NMR) such as spectroscopy serious pathology may be hidden from medical staff. Thus increasing the risk of receiving a wrong diagnosis. The primary merit for NMR is the non-invasive nature of the experiment. In terms of clinical measurements the patient is placed in a static magnetic field and the hydrogen nuclei are tilted by a perpendicular time varying RF magnetic field. After excitation of the nuclei they return to an equilibrium state in which they emit the previously absorbed energy at the Larmor frequency. This re-emitted energy is then recorded by a receiver coil.

Two primary noise sources in NMR are sample and electronic noise. In order to lower the electronic noise the electronics can be cooled down to cryogenic temperatures. Further, decreasing the size of the receiver coils lowers the noise gathered from the sample. However, decreasing the size of the coil also decreases the field of view. Hence, arrays are needed in order to maintain small sample noise but a large field of view.

This project focuses on increasing the SNR of magnetic resonance systems by investigating cryogenic receiver coil arrays and RF front ends and their integration. Receiver coil and RF front end design flows are usually separated. However, this does not yield an optimal coil or LNA nor system for that matter. This project strives to merge the two design flows and create novel methodologies and designs by integrating cryogenic coil arrays and RF front ends in order to optimize the SNR of the receiver system.

Having better SNR can either decrease imaging time or increase image quality. The first aspect concerns especially the new field of hyperpolarization where the signal is decaying relatively fast. Hence faster imaging yields a better insight into the metobolization of the hyperpolarized tracers. This can be used in cancer diagnosis and treatment. Finally having better images can reveal unknown structural diseases in an earlier stage. Thus increasing the probability of recovery for the patient.

Scientific output
Find Daniel's publications at DTU's online research database ORBIT.

Funding
The project is funded by the Danish National Research Foundation as part of the HYPERMAG Center of Excellence (DNRF124) and DTU Elektro.

Supervisors
Associate Professor Vitaliy Zhurbenko and Professor Jan Ardenkjær-Larsen.

Project Period
February 2016 - January 2019

How to design a preamplifier

Watch how Daniel designs preamplifiers for Magnetic Resonance Imaging.
http://www.hypermag.dtu.dk/research/phd-projects/daniel-hoejrup-johansen
14 NOVEMBER 2019