The magnetic resonance imaging signal in terms of physics can be seen as being broken down into T1 relaxation and T2 decay. The resulting signal then is able to create images based on the captured T1 and T2 data.
T1 and T2 in physics are types of relaxation. T1 relaxation is known as longitudinal relaxation and T2 is known as spin-spin relaxation. In the T1 type of relaxation, atomic nuclei come to thermal equilibrium in the magnetic field. In the T2 process spins cause the irreversible loss of mechanization and cannot be recovered.
T1 MRI and T2 MRI produce different kinds of images. Let’s take a closer look at those differences.
T1 MRI, or T1-weighted MRI, provides images with the contrast that is derived from the longitudinal time of relaxation of the explored soft tissue of the human organism. The shorter the relaxation time is, the brighter the resulting images.
T2 MRI, or T2-weighted MRI, provides images with the contrast based on the T2, or transverse relaxation time of the soft tissue being explored. Resulting images would appear brighter in case of longer transverse relaxation.
|T1 MRI||T2 MRI|
|Derived from longitudinal relaxation||Derived from transverse relaxation|
|Brighter images show shorter T1 relaxation||Brighter images show long T2 relaxation|
Let’s compare them by the physical nature and the resulting brightness.
- A T1 MRI image is derived from the longitudinal time of relaxation, while a T2 MRI image is derived from the transverse relaxation time. Two types of images show pictures based on different physical properties of soft tissue being explored in the process of an MRI procedure.
- The brightness of images in T1 MRI and T2 MRI show the medical specialist different things. If in a T1 MRI the image is brighter, that is an indication of the shorter T1 relaxation. If a T2 MRI image is brighter, it shows longer T2 relaxation.
You can see in this video the analysis that reveals the differences between T1 and T2 MRI: