Final answer:
Magnetization Transfer Contrast (MTC) is a technique in MRI that enhances tissue contrast by transferring magnetization between different tissues. MRI contrast agents are used to selectively affect the magnetic properties of water in specific tissues for better visualization. Gd³+ is an important metal complex for this purpose.
Step-by-step explanation:
Magnetization Transfer Contrast (MTC) is a technique used in magnetic resonance imaging (MRI) to enhance the contrast between different types of tissues. It involves transferring magnetization from a pool of protons in one type of tissue to another pool of protons in a different tissue. By doing so, MTC can improve the visibility of certain structures or pathological conditions in the images.
In MRI, the magnetic properties of hydrogen atoms in water are used to create detailed images of soft tissues. However, the properties of water do not differ significantly between different tissues, making it challenging to obtain images with good contrast. To address this, complexing agents known as MRI contrast agents are used. By injecting these agents into the patient, the magnetic properties of water in specific tissues or blood vessels can be selectively affected, allowing doctors to visualize and differentiate between them.
One example of an important metal ion used as an MRI contrast agent is Gd³+, which is highly paramagnetic due to its seven unpaired electrons. To ensure safety, Gd³+ is administered as a stable complex that does not dissociate in the body and can be excreted intact by the kidneys.