Magnetic Resonance Imaging

Magnetic Resonance Imaging (MRI) is able to generate 3-D images with arbitrary orientation of the image planes and with image contrast based on a broad variety of image operational parameters. The fact that different soft tissues exhibit MR signal behavior quite differently enables this image technique to provide excellent soft tissue contrast, superior than other image modalities. Unlike image techniques that apply radiation exposure, MRI uses the radio frequency (RF) pulse to excite hydrogen protons within tissues and receives signal released from them, thus is considered to be radiation safe.

The image intensity in MR images is determined by tissue properties including the relaxometry properties.  The spin-spin relaxation time (T2) and spin-lattice relaxation time (T1) in tissue describe how fast the magnetization recovers back to its equilibrium status after interference with RF pulse. The study of quantitative relaxometry is aimed to use specific MRI sequences and models to calculate the tissue relaxometry properties. In contrast to raw MR image which is a weighted value and may vary significantly across different hardware. The quantitative relaxometry map is considered to be intrinsic to tissue and therefore is more consistent across experiments. Findings from previous studies have shown quantitative relaxometry can be used as good biomarkers for a broad range of diseases. Read More »

A special type of MRI experiment is also able to assess the macromolecule within tissue by using the concept of magnetization transfer (MT). This idea is brought out as researchers found that there are substantial magnetization exchange between water protons and protons in tissue macromolecules. By saturating macromolecular protons and measuring subsequent water signals after adequate magnetization exchange between protons, researchers can assess macromolecules which can further help investigate microstructure of different tissue types. MT effect has been found in almost all human tissues and therefore possesses great potential as a good diagnostic imaging biomarker. Read More »