Polyamines (BioDeep_00000755619)

描述信息

Gadopentetate dimeglumine, also known as gadopentetic acid dimeglumine salt or magnevist, belongs to pentacarboxylic acids and derivatives class of compounds. Those are carboxylic acids containing exactly five carboxyl groups. Gadopentetate dimeglumine can be found in arabica coffee, which makes gadopentetate dimeglumine a potential biomarker for the consumption of this food product. Gadopentetate dimeglumine can be found primarily in blood and urine. Gadopentetate dimeglumine is a drug which is used for use with magnetic resonance imaging (mri) in adults, and pediatric patients (2 years of age and older) to visualize lesions with abnormal vascularity in the brain (intracranial lesions), spine and associated tissues as well as lesions with abnormal vascularity in the head and neck. also used to facilitate the visualization of lesions with abnormal vascularity in the body (excluding the heart). Gadopentetic acid is one of the trade names for a gadolinium-based MRI contrast agent, usually administered as a salt of a complex of gadolinium with DTPA (diethylenetriaminepentacetate) with the chemical formula A2[Gd(DTPA)(H2O)]; when cation A is the protonated form of the amino sugar meglumine the salt goes under the name "gadopentetate dimeglumine". It was described in 1981 and introduced as the first MRI contrast agent in 1987. It is used to assist imaging of blood vessels and of inflamed or diseased tissue where the blood vessels become "leaky". It is often used when viewing intracranial lesions with abnormal vascularity or abnormalities in the blood–brain barrier. It is usually injected intravenously. Gd-DTPA is classed as an acyclic, ionic gadolinium contrast medium. Its paramagnetic property reduces the T1 relaxation time (and to some extent the T2 and T2* relaxation times) in NMR, which is the source of its clinical utility . 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. The proton relaxation effect (PRE) of an unpaired electron is 700 times stronger than that of a proton itself. In MRI, visualization of normal and pathological brain 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, gadopentetate dimeglumine shortens the T1 and T2 relaxation times in tissues where it accumulates. In the central nervous system (CNS), gadopentetate dimeglumine enhances visualization of normal tissues that lack a blood-brain barrier, such as the pituitary gland and the meninges. Gadopentetate dimeglumine does not cross the intact blood-brain barrier; therefore, it does not accumulate in normal brain tissue or in CNS lesions that have not caused an abnormal blood-brain barrier (e.g., cysts, mature post-operative scars). Abnormal vascularity or disruption of the blood-brain barrier allows accumulation of gadopentetate dimeglumine in lesions such as neoplasms, abscesses, and subacute infarcts. Outside the CNS, gadopentetate dimeglumine rapidly reaches equilibrium in the interstitial compartment and enhances signal in all tissues as a function of delivery and size of the interstitial compartment.

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