Magnetic Resonance Imaging Analysis

Magnetic resonance imaging (MRI) is a non-invasive imaging tool that can provide increased contrast between soft tissues to visualize structure and function thereof for diagnostic purposes. MRI has high spatial and temporal resolution and is safer than other imaging modalities because it does not require ionizing radiation. Rather, MRI is based on the behavior, interaction, and alignment of water protons that are found in soft tissue when an external magnetic field is applied. The magnetic field causes alignment of the magnetic moments of the protons, after which a radiofrequency pulse is used to cause the protons to precess, and upon removal of the pulse, the protons undergo relaxation, measured in longitudinal relaxation time (T1) and transverse …show more content…
One example is nanoparticles that have been formulated with gadolinium, which is also used as a non-nanomaterial contrast agent in MRI. Gadolinium ions have been incorporated into various nano-scaffolds consisting of polymers, micelles, liposomes, carbon nanotubes, lipoproteins, and silica nanoparticles. These contrast agents show increased sensitivity as the magnetic fields concentrate the ions in and around the tissue of interest. Gadolinium chelates are usually in macrocyclic form to prevent leaching out of gadolinium ions, which can cause nephrotoxicity. Gadolinium based nanomaterials are used in T1-weighted MRI because of the gadolinium is paramagnetic, and the contrast produced is positive in nature. This makes gadolinium based nanomaterials very useful in areas with unpredictable structure and possible signal voids, like the abdomen. Gadolinium has also been combined with dendrimers to produce MRI contrast agents. Dendrimer based contrast agents, like gadolinium-PAMAM Starbust dendrimer, have a longer half-life than common gadolinium based contrast agents, and can have high molecular relaxivity. The larger dendrimers have difficulty being cleared from the liver, and retention of these contrast agents is