ENC next week

Spin Locking SQCs in an iMQC Experiment

Gigi Galiana1; Rosa T. Branca2; Warren S. Warren2;
1Princeton University, Princeton, NJ; 2Duke University, Durham, NC;

While iMQCs present a wide range of promising applications, dephasing during t2 competes with signal buildup, and limits the maximum attainable signal. Previous work has explored signal with T1ρ decay during t1, where iMQC terms like IxSx can be locked with a steady RF field along x. In reality, many Cartesian terms that do not lie along the locking axis can also be conserved with a spinlocking pulse. For example, antiphase terms such as IxSz–IzSx, are perfectly locked with a spinlock along y, and continue to be locked when they evolve into observable magnetization. Based on this principle, we present a method to slow the effective dephasing rate during the signal build up period to enhance the iMQC signal.

Distant Dipolar Field Effects in Polymer Melts: A new Approach
Towards Structural Investigations Of Complex Fluids

Priyanga Bandara; Marcel Utz;
University of Connecticut, Storrs, CT, United States

We report the observation of distant dipolar field (DDF) effects in polymer melts. Using the CRAZED sequence, we have succeeded in obtaining DDF double quantum echos in melts of poly(isobutylene). In this system, T2is about 2ms. This requires the use of very strong gradient pulses, which are generated using a home-built gradient probe assembly with a car battery as current source. Experiments of this type could be very useful to investigate the structure of polymer systems. Motivated by such applications, we report pilot measurements using a suspension of PTFE spheres of various diameters in PIB.


Intermolecular Zero Quantum Spectroscopy in the Live Mouse Brain Using a MR Imager
Benoit M. Boulat; P.T. Narasimhan; Russell E. Jacobs;
Caltech, Pasadena, CA

We have utilized the effects of the distant dipolar field to obtain one-dimensional high-resolution NMR spectra in the full head or a localized region in the brain of live mice. Experiments were conducted on a 11.7T magnetic resonance imager. The method uses techniques of two-dimensional NMR spectroscopy and can be well described within the formalism known as “Intermolecular Zero Quantum (IZQ) spectroscopy”. Based on HOMOGENIZED class of pulse sequences, IZQ spectra of good resolution and signal to noise ratio could be obtained in as little as 18 minutes. The method was utilized to study mice of various genetic background.

In vivo multiple quantum imaging of prostatic ductal structure by MR: preliminary results

Albert P Chen1; Charles H Cunningham2; Louis-S Bouchard3; Janine Lupo1; John M
Pauly2; Danial B Vigneron1;

1University of California, San Francisco, San Francisco, CA; 2Stanford University, Stanford, CA; 3University of California, Berkeley and LBNL, Berkeley, CA;

The glandular prostate consists of a duct system that can not be resolved by conventional MRI at lower or moderate field strength (1.5T-3T). Intermolecular multiple quantum coherence (iMQC) that arises from long-range nuclear dipole-dipole couplings has been shown to have the ability to encode spatial heterogeneity on an intermediate length scale using a CRAZED sequence. With this method, structural anisotropy of a given material not detected by MR diffusion methods have been observed in heterogeneous media. This preliminary study demonstrates for the first time the feasibility of obtaining CRAZED images from the prostate in vivo. Potentially, CRAZED may provide a unique image contrast based on the ductal structural anisotropy.


Fast simultaneous measurement of D and T2 using the distant dipolar field

Wilson Barros Jr; Daniel F. Gochberg;
Vanderbilt University Institute of Imaging Science, Nashville, TN

Recently, we reported the simultaneous measurement of the self-diffusion coefficient D and the
spin-spin relaxation time T2 via the NMR signal refocused by long-range dipolar field interactions. Typically the signal available for this methodology is a fraction of the full equilibrium magnetization density. Here, we incorporated a train of equally spaced π pulses into the standard CRAZED (COSY Revamped by Asymmetric Z-gradient Echo Detection) sequence in order to improve the signal-to-noise ratio as well as to perform fast acquisition. A reduction of undesirable diffusion-attenuation caused by local magnetic-field inhomogeneities is also realized. In a series of experiments, the parameters D and T2 are extracted by this method and then compared to values obtained by conventional techniques.