|Metabolic & Biochemical Tissue Characterization Using Non-Proton MR|
Quantitative Cardiac 31P Spectroscopy at 3T:
Practical Limitations and Solutions
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.
Advances in the ERETIC Method for the Quantification
of In-Vivo 1H and 31P Spectra
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.
Non-Parametric Analysis of
Hyperpolarized Dynamic 13C Lactate Imaging in a Transgenic Mouse Model
of Prostate Cancer<
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.
Compressed Sensing for Resolution Enhancement of
Hyperpolarized Carbon-13 Flyback 3D-MRSI
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.
Combination of Datasets from [2-13C]Acetate and
[1-13C]Glucose Experiments Improve Accuracy of Metabolic Rates
Determination in Humans
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 VTCAa, VTCAnand glutamatergic neurotransmission (VNT), 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.
Quantitative Tissue Oxygen Measurement in Multiple
Organs Using 19F MRI
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.
Improving the Resolution of SPRITE for in Vivo
23Na Imaging: A Comparison of Conical-SPRITE vs Sectorial-SPRITE
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.
Sodium MRI of the Human Brain Using Projection
Acquisition in the Steady-State with Coherent Magnetization (Na-PACMAN)
Robert Wayne Stobbe1, Christian Beaulieu1
1University of Alberta, Edmonton, Canada
The relaxation mechanism for sodium is different than for proton. The T2f component of transverse relaxation is related to macromolecular anisotropy and covers a very large relative range in the human brain. For this reason strongly T2f 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 T2f* weighted sodium images.
Quantifying Sodium in the Lumbar Spine in Vivo
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.
|18:18||201.||Detection of a New Pulmonary Gas-Exchange Component
for Hyperpolarized Xenon-129
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.