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AbdElMonem M. El-Sharkawy¹, ², Michael Schär¹, ², Ronald Ouwerkerk¹, Robert G. Weiss¹, ³, Paul A. Bottomley¹

¹Johns Hopkins University, Baltimore, USA; ²Philips Medical Systems, Cleveland, USA; ³Johns Hopkins University School of Medicine, Baltimore, USA

Practical limits and solutions for accurate cardiac 31P MRS quantification at 3T are investigated. We find that long adiabatic BIR4 pulses used at 3T to overcome power constraints result in significant errors in steady-state magnetization in BIR4 protocols and T1 measured by the dual angle method. The errors are ameliorated with 90  adiabatic-half-passage (AHP) pulses. A custom coil and protocol for human cardiac 3T 31P MRS are used to measure the T1s of PCr and γ-ATP in the human heart with a new, efficient dual-TR approach that meets bandwidth and power requirements. The measurements are validated against conventional T1 methods.

Susanne Schweizer¹, Nicola De Zanche¹, Giel Mens², Anke Henning¹, Peter Boesiger¹

¹Institute for Biomedical Engineering, University and ETH Zürich, Zürich, Switzerland; ²Philips Medical Systems, Best, Netherlands

Absolute quantification is a desirable tool to determine metabolite changes. Calibration with ERETIC (Electric REference To access In vivo Concentrations) has proven to be an accurate method for the assessment of absolute concentration in spectra. In this work, we present a new implementation of ERETIC on a clinical scanner using a low-power transmit channel, thus permitting simultaneous use of proton decoupling and nuclear Overhauser enhancement with the high-power RF channel of the system during the acquisition of 31P or 13C spectra. Stability of the ERETIC signal is demonstrated. Also, ERETIC was for the first time applied to in-vivo 1H measurements.

Janine M. Lupo¹, Albert P. Chen¹, Charles H. Cunningham², Robert Bok¹, John Kurhanewicz¹, Daniel B. Vigneron¹, Sarah J. Nelson¹

¹University of California, San Francisco, USA; ²Sunnybrook Health Sciences Centre, Toronto, Canada

While the main approach for pre-polarized ¹³C metabolic MR studies has utilized spectroscopic imaging techniques, acquiring high-resolution, full coverage dynamic lactate images to track the time course of ¹³C lactate in vivo after injection of pre-polarized ¹³C-pyruvate may be advantageous.  This study demonstrated the feasibility of using 3D ¹³C dynamic lactate imaging to characterize lactate metabolism in vivo at high spatial and temporal resolution in a transgenic mouse model of prostate cancer.  Non-parametric values obtained from the ¹³C lactate dynamic curves demonstrated differences within individual tumors as well as between tumors with different levels of disease progression.

Simon Hu¹, ², Michael Lustig³, Albert P. Chen¹, Jason Crane¹, Adam Kerr³, Douglas Kelley⁴, Ralph E. Hurd⁴, John Kurhanewicz¹, ², Sarah J. Nelson¹, ², John M. Pauly³, Daniel B. Vigneron¹, ²

¹University of California at San Francisco, San Francisco, California , USA; ²UCSF & UCB Joint Graduate Group in Bioengineering, San Francisco, California , USA; ³Stanford University, Stanford, California , USA; ⁴GE Healthcare, San Francisco, California , USA

Dynamic nuclear polarization has enabled rapid assessment of in vivo ¹³C  metabolism at very high SNR. The high SNR from this hyperpolarization technique makes high-resolution ¹³C 3D-MRSI feasible. However, short T1’s limit the acquisition time and thus spatial resolution and coverage possible with conventional phase-encoding. In this project we developed compressed sensing (CS) methods to enhance spatial resolution without increasing acquisition time for a flyback ¹³C 3D-MRSI sequence. Following phantom testing, we applied this method in normal and prostate cancer rodent studies to achieve a factor-of-2 resolution enhancement in vivo with only a 20% decrease in SNR.

F Boumezbeur¹, K Falk Petersen², R A. de Graaf², G W. Cline², K L. Behar², G I. Shulman³, D L. Rothman², G F. Mason²

¹Neurospin, I2BM, Gif-sur-Yvette, France; ²Yale University, School of Medicine, New Haven, Connecticut, USA; ³Howard Hughes Medical Institute, New Haven, Connecticut, USA

NMR spectroscopy (MRS) combined with ¹³C-labeled glucose allows the study of brain metabolism in vivo. To improve the precision of the quantitative determination of the rates of oxidative energy synthesis V_TCAa, V_TCAnand glutamatergic neurotransmission (V_NT), we combined pairs of dynamic ¹³C MRS time courses on individual subjects who underwent both [1-¹³C]glucose and [2-¹³C]acetate infusions. Our results demonstrate that our new approach allows a more accurate quantification (~2 to 8 fold improvement of the precision of these rates.  However, the rates obtained were consistent with previous studies using just one isotope, providing validation for experiments done with [1-¹³C]glucose.

Siyuan Liu¹, Lisa J. Wilmes¹, Vikram Kodibagkar², Michael F. Wendland¹, Nola Hylton¹, Harriet W. Hopf³, Ralph P. Mason², Mark D. Rollins¹

¹University of California, San Francisco, San Francisco, California , USA; ²University of Texas at Southwestern, Dallas, Texas, USA; ³University of Utah, Salt Lake City, Utah, USA

Critical patients need adequate oxygenation of vital organs.  Measuring individual organ oxygen levels directly provides defined endpoints to titrate medical interventions. We evaluated the feasibility of ¹⁹F MRI for organ oxygen measurement and effects of hyperoxia on individual rat organs using a Varian 7T system, ¹⁹F/¹H volume coil, and FREDOM sequence. The pO₂ in all six organs examined, increased after changing from room air to 100% oxygen. The marked variability and different increases in organ pO₂ show the diversities of oxygenation and potential benefit of regional measurements. This technique has potential to optimize patient resuscitation and guide cancer therapeutics.

Sandro Romanzetti¹, Alexandre A. Khrapitchev², Joachim Kaffanke¹, Bruce J. Balcom², Nadim Joni Shah¹, ³

¹Research Centre Juelich, Juelich, Germany; ²University of New Brunswick, Fredericton, Canada; ³University of Dortmund, Dortmund, Germany

In this work, images of the sodium distribution of an healthy brain were acquired using Conical- and Sectorial-SPRITE and compared in terms of their final resolutions. The Conical-SPRITE sequence provide images of good SNR but at a low-resolution which only allows one to delineate details such as CSF, and the eyes where the sodium signal is very strong. In contrast, Sectorial-SPRITE provides finer anatomical details of the brain that may be critical to monitor and diagnose pathologies leading to change of local Tissue Sodium Content.

Robert Wayne Stobbe¹, Christian Beaulieu¹

¹University of Alberta, Edmonton, Canada

The relaxation mechanism for sodium is different than for proton. The T_2f component of transverse relaxation is related to macromolecular anisotropy and covers a very large relative range in the human brain. For this reason strongly T_2f weighted sodium imaging may prove useful in the investigation of neurological disease, providing different contrast than proton or quantitative sodium concentration imaging.   A new sodium imaging sequence (Na-PACMAN) is proposed for the generation of high quality, strongly T_2f* weighted sodium images.

Matthew Fenty¹, Chenyang Wang¹, Walter RT Witschey II¹, John Bruce Kneeland, M.D. ², Ravinder Reddy, PhD¹, Arijitt Borthakur PhD¹

¹University of Pennsylvania, Philadelphia, Pennsylvania, USA; ²Pennsylvania Hospital, Philadelphia, Pennsylvania, USA

Degenerative Disc Disease (DDD) is a gradual deterioration of the disc between the vertebrae and may be a cause of lower back pain in adults.  Sodium content correlates with proteoglycan content in cartilage tissue and therefore quantifying sodium via MRI may serve as an imaging biomarker for DDD.  We demonstrate the feasibility of quantifying sodium concentrations in the intervertebral discs of the lumbar spine.

Yulin Chang¹, Jaime F. Mata², Jing Cai², Talissa Altes¹, ², James R. Brookeman², Klaus D. Hagspiel², John P. Mugler III², Kai Ruppert¹, ²

¹The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA; ²University of Virginia, Charlottesville, Virginia , USA

Over the years several hyperpolarized Xenon-129 spectroscopy studies revealed a puzzling and little explored discrepancy between the time constant for xenon entering the lung tissue (50-120 ms) and that for xenon returning to the alveoli through exchange (~10 ms in rabbits). By employing an uptake MRS pulse sequence with finely spaced delay times and comparing it to an exchange MRS sequence, we investigated in rabbits the origins of this apparent difference in time constants. Our results indicate that the tissue/plasma peak contains a component that is saturated in just a few milliseconds and clearly dominates the measured exchange time constant.