UCL DEPARTMENT OF MEDICAL PHYSICS AND BIOENGINEERING

Radiofrequency Coil Development

At AMRIG we have a special coil development lab for building and testing radiofrequency (RF) coils for use on both clinical and pre-clinical systems.

The RF coils used to perturb the spin system and receive the signal are highly resonant tuned circuits, similar to a television antennae except that they are designed so that they only transmit/receive a magnetic field.  Building a coil is a very involving process requiring specialist non-magnetic components and equipment (such as a Network Analyzer).

Current Projects

Arterial Spin Labelling Transmit Coils

Arterial Spin Labelling is an MRI technique that allows perfusion (blood flow to tissue) to be non-invasively measured in the brain using the protons in arterial blood water as an endogenous tracer.  Labelling occurs in the arteries in the neck by applying a radiofrequency magnetic field in combination with a linear gradient.  Only the water that is flowing in the arteries is labelled, however large macro-molecules in the imaging slice are also saturated (this process is called magnetisation transfer, MT) so a control image (where no labelling is applied) must also be acquired so that the tag and control images can be subtracted (cancelling MT effects).  Using a localised labelling coil means that the transmit field is confined to the neck and no macro-molecules are saturated.

We are investigating using separate labelling coils to improve the accuracy of perfusion measurements and to also allow specific arteries to be labelled, facilitating vascular territory maps of the brain to be obtained.