Paramagnetic contrast agents
Paramagnetic contrast agents are use to enhance MRI images and display areas of hypervascularity and associated pathology. They have their strongest effect in T1 weighted imaging because they predominantly alter the T1 relaxation time in the tissues in which they have accumulated.
MRI imaging relies upon the signal generated from the behaviour of water protons. The relaxation of these water protons is affected by surrounding tissues and, when a paramagnetic contrast agent has been absorbed in its vicinity, the relaxation of water protons is enhanced.
The paramagnetic contrast agents generate a magnetic field 1000 times stronger than water protons. The interaction between the contrast agent and the water proton is exactly the same as the corresponding interactions with other molecules except that the magnitude of their magnetic interaction has a much greater effect on the relaxation time.
Commonly used contrast agents include: