| Mechanism of action |
Based on the behavior of protons when placed in a strong magnetic
field, which is interpreted and transformed into images by magnetic
resonance (MR) instruments. MR images are based primarily on proton
density and proton relaxation dynamics. MR instruments are sensitive to
two different relaxation processes, the T1 (spin-lattice or longitudinal
relaxation time) and T2 (spin-spin or transverse relaxation time).
Paramagnetic agents contain one or more unpaired electrons that enhance
the T1 and T2 relaxation rates of protons in their molecular
environment. In MRI, visualization of normal and pathological brain,
spinal and hepatic tissue depends in part on variations in the radio
frequency signal intensity that occur with changes in proton density,
alteration of the T1, and variation in T2. When placed in a magnetic
field, gadoversetamide shortens the T1 and T2 relaxation times in
tissues where it accumulates. At the recommended dose, the effect is
primarily on T1 relaxation time, and produces an increase in signal
intensity (brightness). Gadoversetamide does not cross the intact
blood-brain barrier; therefore, it does not accumulate in normal brain
tissue or in CNS lesions that may have a normal blood-brain barrier
(e.g., cysts, mature post-operative scars). Abnormal vascularity or
disruption of the blood-brain barrier allows accumulation of
gadoversetamide in lesions such as neoplasms, abscesses, and subacute
infarcts. |
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