Traditional Posters: Miscellaneous

Traditional Posters: Miscellaneous

Spectroscopic Quantification Methodology

Hall B Tuesday 13:30-15:30

898. The Case of the Missing Glutamine

Ileana Hancu¹, Mark Frye², John Port<sup>2

1</sup>GE Global Research Center, Niskayuna, NY, United States; ²Mayo Clinic, Rochester, MN, United States

A theoretical study is performed to understand the accuracy and repeatability of multiple pulse sequences in quantifying glutamine concentration at 3T. Variable repeatability (12% to >50%) and significant bias (-30% to +70%) is noted for the seven pulse sequences considered. Data acquired in vivo using three of the pulse sequences used for simulations matches the predicted repeatability well. Following correction for the expected bias of each pulse sequence, consistent glutamine measurements, all in the 1mM range, are reported with the 3 sequences. An explanation for the mismatch between the in vivo 1H MRS and ex vivo results is attempted.

899. Human Breast Lipid Composition Determination by in Vivo Proton MRS at 7T

Ivan Dimitrov¹, Deborah Douglas², Jimin Ren², Andrew G. Webb³, A Dean Sherry², Craig R. Malloy<sup>2

1</sup>Philips Medical Systems, Cleveland, OH, United States; ²Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, United States; ³Radiology, Leiden University Medical Center, Leiden, Netherlands

The role of diet and fat consumption in the pathogenesis of breast cancer is an important subject. We report on the non-invasive determination of lipid composition in human breast by ¹H-MRS at 7T. Two respiratory-triggered TE-averaged STEAMs were performed in healthy volunteers where the second acquisition had all gradients inverted. T₁ and T₂ were also measured. Ten lipid peaks were typically resolved. The average lipid composition was 30.5% saturated, 48.4% mono-unsaturated, and 21.1% di-unsaturated. In conclusion, we have shown that a chemical analysis of lipids in breast tissue can be determined quite simply and non-invasively by proton MRS at 7T.

900. Is Human Glial TCA Cycle Rate Faster Than We Thought?

Napapon Sailasuta¹, Brian D. Ross<sup>1,2

1</sup>Clinical MR Spectroscopy, Huntington Medical Research Institutes, Pasadena, CA, United States; ²Rudi Schulte Research Institute, Santa Barbara , CA, United States

13C MRS uniquely quantifies glutamine-glutamate cycle rate in either neurons or glia, driven by the substrate selection of their cellular membrane transporters. Glial metabolic rate is of increasing interest as the range of human neurological disorders which appears selective to glia (Alzheimer’s, MS; TBI; epilepsy) increases and as selective medications are designed to correct such abnormalities. 13C enrichment followed by localized 13C MRS detection of many specific products has provided valuable background. In a recent study we encountered a mismatch between prior metabolic models and a simplified method described here – with a 5 – 10 fold difference in the measured rate.

901. Quantification Precision of Human Brain ¹H MRS at Different Field Strengths: A Simulation Study

Dinesh K. Deelchand¹, Isabelle Iltis¹, Pierre-Francois Van de Moortele¹, Pierre-Gilles Henry<sup>1

1</sup>Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States

¹H MRS allows measurement of the concentration of a number of brain metabolites in vivo. It is generally accepted that the precision of quantification improves with B₀. In principle, two factors may contribute to this increase in quantification precision: higher signal-to-noise ratio (SNR) and higher spectral resolution. In this work, we assess the respective contribution of these two factors using simulations. We report that, especially above 3-4 Tesla, increased SNR is the major contributor to the increase in quantification precision, as the gain in chemical-shift dispersion is offset by the increase in linewidth in vivo.

902. Regularized Spectral Lineshape Deconvolution