The majority of contrast agents which are used in clinical imaging are based on Gadolinium, which is strongly paramagnetic due to its 7 unpaired electrons. To reduce toxicity and to modifiy pharmacokinetic properties, Gd3++ ions are usually chelated with appropriate ligands.

Contrast agents increase longitudinal and transverse relaxation rates (R1 nd R2) and consequently shorten the corresponding relaxation times (T1 and T2). The majority of acquisition techniqes employ the T1-shortening effect, by using T1-weighted acquisitions after (or possibly during) intravenous administration of contrast agent. The presence of contrast agents then causes an increase in signal intensity.

MRI contrast agents provide functional information in the sense that the indicate areas where contrast agent can accumulate in the interstitium, e.g. due to blood-brain barrier leakage or otherwise leaking vessels.

A variety of specialized techniques allow to derive more functional information, e.g. about tissue perfusion (blood flow) or blood volume. This is achieved by time-resolved imaging during CA administration, and the application of tracer kinetic analysis.

Dear Lydia,

Below I am attaching few Journals which will help you. The commonly used contrast agents are Gadolinium.

Thanks

regards,

sam

Dear Lydia,

reading your question I was not sure, if you are just interested in contrast agent application like Gadolinium (where answers are already provided) or you are interested in CEST MRI (CEST = chemical exchange saturation transfer). The latter can be performed with and without contrast agents. Some endogenous substrates also provide a CEST effect (amide, amine, hydroxyl protons). Contrast agents like Iopamidol enable the assessment of pH value very accurately (although pH measurements have also been performed with endogenous CEST effect). Additional contrast agents used for CEST imaging are paramagnetic agents. Other contrast agents for CEST are for example glycogen, sucralose, 3OMG etc.

In CEST MRI, both endogenous and exogenous contrast is possible and provide different information.

CEST MRI provides biochemical information.

Regards

Anja

There are many examples regarding your question.

EG.:

In perfusion imaging with contrast agent which is the dynamic technique the morphology of not perfused regions of infarction in the brain are visible. So it presents both functional and anatomic/pathologic features.

In clasical contrast enhanced MR studies of the brain the enhanced structures are the structures with broken blood brain barier eg. tumors, infections. However some brain structures phisiologicaly do not have bbb and normally enhance (eg pituitary gland). So here also is anatomical and functional application.

In many parenhymal human organs eg liver there is no barier. In liver we may observe the patern of enhamcent of liver masses on dynamic examination and this functional and anatomical/pathological information enables the differentiation of liver masess.

Thank you all for the valuable answers and reading material suggestions. I really appreciate the help.

Regards,