Heteronuclear Gd-<sup>99m</sup>Tc Complex of DTPA-Bis(histidylamide)
Conjugate as a Bimodal MR/SPECT Imaging Probe
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Abstract
The work describes the synthesis and in vivo application
of heterotrimetallic
complexes of the type {Gd(H<sub>2</sub>O)[(M(H<sub>2</sub>O)(CO)<sub>3</sub>)<sub>2</sub>(<b>1</b>)]} {<b>1</b> = DTPA-bis(histidyl-amide); <i>M</i> = Re (<b>3a</b>); <sup>99m</sup>Tc (<b>3b</b>)} for dual modality MR/SPECT imaging. Here, the DTPA-bis(histidylamide)
conjugate functions as a trinucleating chelate incorporating Gd in
the DTPA core with Re or <sup>99m</sup>Tc in the pair of histidylamide
side arms. The two complexes are chemically equivalent as revealed
by HPLC, and their “cocktail mixture” (<b>3a</b> + <b>3b</b>) has demonstrated itself to be essentially a single
bimodal imaging probe. The present system has thus overcome the sensitivity
difference problem between MRI and SPECT and paved the way for practical
applications
