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Eu-1,7-Bis(2-(methylene Benzyloxy Ether)-Acetic Acid) acetamide-4,10-bis(acetamidoacetic acid)-1,4,7,10- Tetraazacyclododecane

Eu-1,7-Bis(2-(methylene Benzyloxy Ether)-Acetic Acid) acetamide-4,10-bis(acetamidoacetic acid)-1,4,7,10- Tetraazacyclododecane

Mark Pagel, Kam Leung

PMID: 20641846

Abstract:

Chemical Exchange Saturation Transfer (CEST) is a novel magnetic resonance imaging (MRI) contrast mechanism (1) that is an attractive alternative to T1 and T2 contrast mechanisms, particularly at high magnetic fields (2). CEST agents possess a hydrogen proton with a moderate to slow exchange rate with water. Selective saturation of the MR frequency of this proton, followed by exchange with solvent water, reduces the MR signal of the water. PARACEST (PARAmagnetic CEST) agents include a paramagnetic lanthanide ion that shifts the MR frequencies of the exchangeable proton to unique values to facilitate selective detection (3, 4). Endogenous MR contrast may be continually monitored in the presence of PARACEST agents by neglecting to saturate the MR frequency of the exchangeable proton (and assuming that the T1 relaxation of the PARACEST agent is negligible).
The selective saturation is typically applied for two or more seconds to generate a steady-state of saturation (5), which greatly lengthens the time required for in vivo detection of PARACEST MRI contrast agents. However, computer simulations and studies with chemical solutions have shown that more rapid MRI acquisition schemes can be prepended with a selective saturation pulse to accelerate the detection of PARACEST MRI contrast agents (6). The choice of the MRI acquisition scheme is dependent on the T1 relaxation time of the endogenous tissue in the presence of the PARACEST agent. In addition, a second "control" MR image is typically acquired to account for the direct saturation of water by applying selective saturation at a MR frequency with an opposite sign relative to the saturation frequency of the first MR image (7). The need for a second MR image further lengthens the in vivo detection of PARACEST agents. However, a single control MR image can be acquired before injecting the PARACEST agent, which obviates the need to acquire control MR images after injection of the agent and accelerates the temporal detection of PARACEST agents after injection (6). Although dynamic changes in MR image contrast may be caused by faster T2* relaxation or magnetic susceptibilities caused by the agent, these effects are estimated to be much lower than the CEST effect, so that the dynamic changes in MR image contrast are attributed to CEST effect of the agent. These principles were used to detect the accumulation of a PARACEST agent, Eu-1,7-Bis(2-(methylene benzyloxy ether)-acetic acid) acetamide-4,10-bis(acetamidoacetic acid)-1,4,7,10-tetraazacyclododecane (Eu-DOTA-OBZ2-Gly2), within the liver tissue of a Balb/C mouse (6). The incorporation of two benzyloxyether moieties in the contrast agent promoted uptake of this agent in liver tissue, which also facilitated in the in vivo detection of the agent.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
LS7931095	4-(Benzyloxy)-2,6-difluorophenylboronic acid			Price

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