Open MRI / 3T

There is a Hitachi Airis Open MRI at CCI

http://www.hitachimed.com/products/mri/CertifiedMRISystems/AirisII/index.html

The field strength is 0.3 T.

Several differences in the imaging.

There is inherently more T1 weighting at lower field so there will be better grey/white differentiation on T1 weighted images.

There are less susceptibility effects at low field (the appearance of intracranial hemorrhage that you have learned is really applicable for 1.5 T or higher.) blood products that are dark on T2 at high field, may not be dark at low field.

Low field has lower signal to noise so that images tend to be noisier.

The difference in larmour frequency of fat and water is less at 0.3T compared to 1.5 T (about 44 Hz vs. 220 Hz), therefore chem sat and spectroscopy are either more difficult or impossible.

For 3T

There is less T1 contrast, so we use FLAIR T1 to give acceptable grey/white differentiation.

There are more susceptibility effects.

There is more chemical shift so we use higher bandwidth acquisitions to leen this effect.

There is greater signal to noise so that we can achieve thinner slices or more resolution.

Chem sat is feasable at 3T (1.5 T and higher). Spectroscopy is better at 3T.

MRA is better at 3T.

Susceptibility (GE SWAN) images are better at 3T than 1.5T.