ABSTRACT
Until recently, NMR imaging with intermolecular multiple-quantum coherences (iMQCs) has been based on the acquisition of a single echo. In vivo studies of iMQC image contrast would greatly benefit from a method that could acquire several orders of quantum coherence during the same acquisition. This would enable comparison of the image contrast for various orders and eliminate image coregistration problems between scans. It has previously been demonstrated that multiple orders of iMQC images can be simultaneously acquired of a simple phantom. Here, we examine the technique and its effect on biological tissue, both in vivo and in vitro. First, we establish the effectiveness of the iMQC sequence in vivo using earthworms as specimens. We then further show that the multi-CRAZED sequence enhances detection of next generation (nanoparticle) contrast agents on excised tumor tissue.
Subject(s)
Image Enhancement/methods , Magnetic Resonance Spectroscopy/methods , Animals , Contrast Media , Female , Image Processing, Computer-Assisted/methods , Mammary Neoplasms, Experimental/diagnosis , Mice , Mice, Nude , Models, Biological , Nanostructures , Oligochaeta , Phantoms, Imaging , Quantum TheoryABSTRACT
In vivo and ex vivo MRI based on intermolecular multiple-quantum coherences (iMQC) is predicted to provide a fundamentally different source of contrast for MRI. This article investigates the dependence of image contrast upon the choice of correlation distance for a heterogeneous material. A closely packed array of parallel hollow cylinders was used to demonstrate signal intensity variations when the correlation distance becomes comparable to the gap size between the cylinders. The observed effects agree well with three-dimensional calculations of the time evolution of magnetization under the nonlinear Bloch equations.
