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Long‐circulating liposomal contrast agents for magnetic resonance imaging
Author(s) -
Ayyagari Ananta Laxmi,
Zhang Xiaodong,
Ghaghada Ketan B.,
Annapragada Ananth,
Hu Xiaoping,
Bellamkonda Ravi V.
Publication year - 2006
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.20846
Subject(s) - gadodiamide , liposome , gadolinium , magnetic resonance imaging , nuclear magnetic resonance , magnetic resonance angiography , chemistry , peg ratio , biomedical engineering , nuclear medicine , medicine , radiology , biochemistry , physics , organic chemistry , finance , economics
Abstract Contrast‐enhanced magnetic resonance imaging (CE‐MRI) is a dynamic technique for imaging vasculature. However, the currently used gadolinium (Gd) chelates, such as Gd‐DTPA, restrict the time window for image acquisition due to their rapid elimination from blood and their rapid diffusion into the extravascular space, which prevents their use in steady‐state imaging, particularly for MR angiography (MRA). The goal of this study was to prepare long‐circulating polyethylene glycol‐bearing ((PEG)ylated) liposomes encapsulating Gd chelate, and characterize and demonstrate their utility for MRA. The liposomes were prepared by hydrating a mixture of lipids with gadodiamide (Omniscan®). The liposomes were sized down to around 100 nm by extruder and exhaustively dialysed to remove the unencapsulated gadodiamide. The Gd liposomes exhibited a significant sustained (>4 hr) contrast enhancement of the vasculature with improved spatial details in a rat model with little leakage relative to Gd‐DTPA controls as shown by MRI. We suggest that such long‐circulating liposomal formulations allow for high spatial resolution imaging without the confounding effects of clearance and extravascular diffusion of the agent complicating the data and image analysis. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.