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Maximizing T2-exchange in Dy(3+)DOTA-(amide)X chelates: fine-tuning the water molecule exchange rate for enhanced T2 contrast in MRI.


ABSTRACT: The water molecule exchange rates in a series of DyDOTA-(amide)X chelates were fine-tuned to maximize the effects of T2-exchange line broadening and improve T2 contrast.Four DyDOTA-(amide)X chelates having a variable number of glycinate side-arms were prepared and characterized as T2-exchange agents. The nonexchanging DyTETA chelate was also used to measure the bulk water T2 reduction due solely to T2*. The total transverse relaxivity (r2tot) at 22, 37, and 52°C for each chelate was measured in vitro at 9.4 Tesla (400 MHz) by fitting plots of total T2 (-1) versus concentration. The water molecule exchange rates for each complex were measured by fitting (17)O line-width versus temperature data taken at 9.4 Tesla (54.3 MHz).The measured transverse relaxivities due to water molecule exchange (r2ex) and bound water lifetimes (?M) were in excellent agreement with Swift-Connick theory, with DyDOTA-(gly)3 giving the largest r2ex?=?11.8 s(-1) mM(-1) at 37°C.By fine-tuning the water molecule exchange rate at 37°C, the transverse relaxivity has been increased by 2 to 30 times compared with previously studied Dy(3+)-based chelates. Polymerization or dendrimerization of the optimal chelate could yield a highly sensitive, molecule-sized T2 contrast agent for improved molecular imaging applications.

SUBMITTER: Soesbe TC 

PROVIDER: S-EPMC4219925 | biostudies-literature | 2014 Mar

REPOSITORIES: biostudies-literature

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Maximizing T2-exchange in Dy(3+)DOTA-(amide)X chelates: fine-tuning the water molecule exchange rate for enhanced T2 contrast in MRI.

Soesbe Todd C TC   Ratnakar S James SJ   Milne Mark M   Zhang Shanrong S   Do Quyen N QN   Kovacs Zoltan Z   Sherry A Dean AD  

Magnetic resonance in medicine 20140301 3


<h4>Purpose</h4>The water molecule exchange rates in a series of DyDOTA-(amide)X chelates were fine-tuned to maximize the effects of T2-exchange line broadening and improve T2 contrast.<h4>Methods</h4>Four DyDOTA-(amide)X chelates having a variable number of glycinate side-arms were prepared and characterized as T2-exchange agents. The nonexchanging DyTETA chelate was also used to measure the bulk water T2 reduction due solely to T2*. The total transverse relaxivity (r2tot) at 22, 37, and 52°C f  ...[more]

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