MRI Sequences

Contrast differences are required to distinguish normal anatomy from pathology. Contrast is improved when two adjacent areas have high and low signal intensities. There are many different MRI sequences (> 100) and all attempt to optimize tissue contrast.

Each MRI image consists of a T1 component and a T2 component (see also Relaxation section). It is possible to switch off most of one of either components, creating a T1 weighted or T2 weighted image respectively. A special form is the proton density (PD) weighted image. This sequence enables the visualization of the number of protons per volume. In order to achieve this, both the T1 and T2 components must be switched off.

The following briefly describes some commonly used MRI sequences.