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information/mri

Magnetic Resonance Imaging

Participant being placed into MRI Scanner

The MRI corridor houses YNiC's GE 3 Tesla HDx Excite MRI scanner and YNiC's Siemens 3T MRI scanner.

For an MRI scan the participant lies on a bed which can then be slid into the scanner.

In the MRI control room, outside the scan room, the radiographer has conventional computer displays from which they can control all the operations of the MRI scanner. The radiographer is always in direct communication with the individual being scanned via speakers and microphones in both the control room and the magnet room. The radiographer can also monitor the participant using a camera and a range of devices that monitor the physiological state of the participant. At the end of scan the computers automatically reconstruct a picture that can be immediately inspected by the radiographer.

Next door to each MRI suite is an MRI-dedicated chemistry laboratory in which the YNiC parahydrogen rig is housed. This equipment is part of an investigation into the production of new contrast agents based on hyperpolarisation. It is not yet used on humans but could offer enormous advantages in the study of metabolic and other chemical processes within the body.

How MRI Works

Magnetic Resonance Imaging (MRI) is a technique that can non-invasively image the internal human anatomy. At YNiC, MRI is used mainly to provide images of the brain but can also be used to image any other part of the body.

To generate a magnetic resonance image, participants lie in a magnetic field, and pulses of radio-frequencies are used to generate images of the brain anatomy. The strength of the magnetic field used by the GE and Siemens MRI scanners at YNiC is 3 Tesla.

The pulses of radio-frequencies generate detailed images of the brain by detecting differences in the distributions of molecules throughout the brain. In a basic structural image, the distribution of water and fat throughout the brain is detected. For instance, the amount of water in blood vessels, and in the bone of the skull is different. This difference allows MRI to generate a contrast image. In the same way that blood and bone have different water concentrations, all types of tissue in the brain have different concentrations of substances that allow the production of images of their distribution. These discrete differences in concentration throughout the brain allow the fine anatomy of the brain to be resolved.

MRI isn’t restricted to only looking at only the distribution of water and fat in the brain; the distribution of other molecules may also be resolved. In functional MRI (fMRI), changes in the distribution of the substances that carry oxygen in the blood are recorded. These changes in blood oxygenation can be related to areas of the brain which are being activated by the experiment that the participant is taking part in. It is also possible to image the distribution of many other molecules in the brain, with glucose and some neurotransmitters being two such examples.

The MRI scanner does generate a significant amount of noise. Participants to be scanned are thus required to wear ear defenders or ear plugs whilst in the scan room. Examples of the sounds the scanner makes when it is running are available below for you to listen to and download for your participants.

MRI Sounds

The following sounds files are provided to aid users and participants in their familiarisation with the MRI environment.

Each sound file represents the noises a participant will hear during a specific type of scan. These sound files were all created from the GE scanner; we aim to provide Siemens-specific sound files in the future, but in the meantime participant's should be advised that they will hear very similar noises to those found in GE.

Click on the files to download or play them.

Noises common to all scans

The standard YNiC structural protocol has the following scans:

  • A localiser. This is the localiser scan that is run at the start of every scanning session. It allows us to tell the scanner's computers exactly where the centre of the area we want to scan is (usually the brain).

  • An ASSET calibration. This short scan allows allows the scanner to be set up to use parallel imaging.

  • A T1 Scan. This is the standard 5 minute T1 sequence we use for structural scans.

  • A T2 Scan. This is the standard 5 minute T2 sequence we use for structural scans.

  • An axial FSE T2 (clinical quality scan). A short, clinical quality T2 run after the structural sequence.

During a typical fMRI acquisition we will use the following sequences:

  • A localiser. This is the localiser scan that is run at the start of every scanning session. It allows us to tell the scanner's computers exactly where the centre of the area we want to scan is (usually the brain).

  • An ASSET calibration. This short scan allows allows the scanner to be set up to use parallel imaging.

  • A T1 FLAIR image. A short T1 sequence usually run in the same session as fMRI (EPI) data acquisition. The T1 FLAIR sequence is a high resolution scan with the same spatial prescription (positioning) as the EPI data and aids in post processing.

  • The EPI sequence. This sequence is used to acquire multiple samples of the brain during the scan. Typically EPI is used for fMRI data. Each 'beep' is a slice of the brain being acquired. The more slices we acquire in a certain amount of time the closer together the beeps will be (i.e. the beeps will be faster).

Note that different investigators may use different combinations of these sequences in different orders as well as other sequences which we have not mentioned here.

Further Information