Room 155 EF

16:00 - 18:00

Moderators:

Priti Balchandani, Andrew A. Maudsley

Bertram J. Wilm¹, Yolanda Duerst¹, Benjamin E. Dietrich², Michael Wyss¹, David Otto Brunner², Christoph Barmet^2,3, Thomas Schmid¹, Signe Johanna Vannesjo¹, and Klaas P. Pruessmann^1
1Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, ZH, Switzerland, ²Institute for Biomedical Engineering, University and ETH Zurich, Zurich, ZH, Switzerland,³Skope Magnetic Resonance Technologies, 8004, ZH, Switzerland

Dynamic field changes caused by hardware imperfections or physiological induced field perturbations can cause signal loss due to increased T2* decay, inaccurate data averaging and off-resonant application of RF pulses. To prevent artifacts in MR spectroscopy, we present a higher-order real-time feedback field control system based on NMR probes which is tested for field stabilization in single-voxel brain MRS at 7T.

Yi Zhang^1,2, Refaat E. Gabr¹, Jinyuan Zhou^1,3, Robert G. Weiss^1,4, and Paul A. Bottomley^1,2
1Division o MR Research, Department of Radiolgoy, Johns Hopkins University, Baltimore, Maryland, United States, ²Electrical and Computer Engineering, Johns Hopkins University, Baltimore, Maryland, United States, ³F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, United States, ⁴Division of Cardiology, Department of Medicine, Johns Hopkins University, Baltimore, Maryland, United States

The inclusion of potentially useful MRS acquisitions in clinical MRI exams is often precluded by long study times for chemical shift imaging (CSI). Global- or lesion-averaged MRS-measurements can usually suffice for assessing metabolic status. A recently proposed method—spectroscopy with linear algebraic modeling (SLAM)—could provide such assessments, in addition to a many-fold speed-up in scan-time. Here, SLAM applied retroactively to patients with brain tumors, is shown to yield quantitatively indistinguishable results from conventional 2D ¹H CSI with an acceleration factor of six. Proactive studies demonstrate comparable results to CSI with a speedup factor of 14.

Zhao Li¹, Jamie D. Walls¹, Susie Y. Huang¹, and Yung-Ya Lin^1
1Chemistry and Biochemistry, UCLA, Los Angeles, CA, United States

A general spin amplification scheme is developed to enhance the sensitivity of heteronuclear MR spectroscopy and imaging based on dynamic instability of the solvent proton magnetization under collective feedback fields of radiation damping and the distant dipolar field. The heteronuclear solute spins are first detected by the solvent proton spins through various magnetization transfer mechanisms and serve as small “input” signals to perturb the solvent proton magnetization, which is prepared in an unstable state. The weakly detected signal is then amplified through subsequent nonlinear evolution of the solvent proton magnetization to achieve 10x SNR improvement for 13C NMR and MRI.

Shang-Yueh Tsai¹, Ying-Hua Chu², Yi-Cheng Hsu³, Wen-Jui Kuo⁴, and Fa-Hsuan Lin^2
1Graduate Institute of Applied Physics, National Cheng-Chi University, Taipei, Taiwan, ²Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan, ³Department of Mathematics, Nnational Taiwan University, Taipei, Taiwan, ⁴Institute of Neuroscience, National Yang-Ming University, Taipei, Taiwan

Fast MR spectroscopic imaging (MRSI) is challenged by its relative low signal-to-noise ratio (SNR), which can be improved by using a surface coil array. Instead of using a coil array to accelerate image encoding at the cost of the reduced SNR, here we propose to exploit this sensitivity information to enforce the k-space data-consistency (DC) in order to suppress noise and consequently to improve MRSI SNR. With in vivo experimental data at 3T using a 32-channel coil array, we found that the DC constraint can improve the SNR of PEPSI by approximately 40%.

Ben Babourina-Brooks¹, Rob Simpson², Theodoros N. Arvanitis^3,4, Andrew C. Peet^1,4, and Nigel Paul Davies^1,5
1School of Cancer Sciences, University of Birmingham, Birmingham, West Midlands, United Kingdom, ²National Physical Laboratory, Middlesex, Greater London, United Kingdom, ³School of Electronic, Electrical & Computer Engineering, University of Birmingham, Birmingham, West Midlands, United Kingdom, ⁴Birmingham Children's Hospital NHS Foundation Trust, Birmingham, West Midlands, United Kingdom, ⁵Imaging & Medical Physics, University Hospitals Birmingham NHS Foundation Trust, Birmingham, West Midlands, United Kingdom

MRS can be used as a non-invasive temperature probe by measuring the chemical shift difference between water and a reference metabolite. The water chemical shift is linearly dependent on temperature, however protein and ionic concentrations may effect this dependence. Water chemical shift calibrations using accurate temperature methods were used in this study to assess the effect of ionic strength and protein strength at 3T. A recent investigation of the effects of ionic strength and a protein concentration has been performed on a 1.5T clinical scanner, vescovo et al. Temperature calibration curves were sensitive to ionic and protein concentrations. Agreement of results with Vescovo et al for similar solutions were also observed.

David H. Johnson¹, Zhiyu Chen¹, Rizwan Ahmad¹, Alexandre Samouilov¹, and Jay L. Zweier^1
1Davis Heart and Lung Research Institute, Ohio State University, Columbus, OH, United States

Donghan Yang¹, James E. Huettner², Jeffrey J. Neil^3,4, and Joseph J.H. Ackerman^1,5
1Department of Chemistry, Washington University in St. Louis, St. Louis, MO, United States, ²Department of Cell Biology & Physiology, Washington University in St. Louis, St. Louis, MO, United States, ³Department of Neurology, Washington University in St. Louis, St. Louis, MO, United States, ⁴Department of Pediatrics, Washington University in St. Louis, St. Louis, MO, United States,⁵Department of Radiology, Washington University in St. Louis, St. Louis, MO, United States

Knowledge of intracellular water preexchange lifetime in neurons and astrocytes is essential for understanding intracellular water diffusion in brain. Employing a previously described cultured cell system, the longitudinal ¹H MR relaxation of intracellular water in mixed cultured neurons and astrocytes was distinguished from that of the extracellular media where the apparent relaxation rate was greatly enhanced via either rapid flow or relaxation agent. Under such conditions, where the true intracellular T₁ is 50 fold greater than the apparent T₁ of the extracellular media (MR slow exchange regime) the intracellular water preexchange lifetime is readily derived, 0.26  0.3 s.

Noam Shemesh¹, Jean-Nicolas Dumez¹, and Lucio Frydman^1
1Department of Chemical Physics, Faculty of Chemistry, Weizmann Institute of Science, Rehovot, Israel

Modification of proton T1 relaxation upon band-selective excitation is well known in protein solution NMR; however, such effects have never been observed in CNS metabolites. Here, we show statistically significant T1 relaxation enhancement in non-water-suppressed band-selective excitation for several metabolites in excised mouse brains. A 30-50% decrease in T1 was observed compared to conventional water suppressed schemes, suggesting some form of cross-relaxation as a mechanism. Our methodology affords a straightforward way to enhance MRS’s sensitivity per unit time, and opens new routes to investigate the nature of metabolic interactions among them and with water in tissues, at a molecular level.

Christine Leon¹, Cornelius Von Morze¹, Bertram Koelsch¹, Adam B. Kerr², Robert A. Bok³, John M. Pauly², John Kurhanewicz¹, Daniel B. Vigneron¹, and Peder E.Z. Larson^1
1Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, United States, ²Magnetic Resonance Systems Research Laboratory, Department of Electrical Engineering, Stanford University, Stanford, CA, United States, ³Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, United States

Magnetic resonance spectroscopy of hyperpolarized substrates provides a powerful tool to investigate metabolism. Recently, we showed that the T_1,Eff of lactate was significantly shorter in tumors suggesting a different cellular environment, in addition to increased K_Pyr→Lac using MAD-STEAM. However, the measurement of the T_1,Eff is a combination of diffusion and spin-relaxation. We modified the MAD-STEAM pulse sequence to include varying gradient strengths to separate diffusion weighting from T₁ relaxation effects. This new method allows for measurements of ADCs and T₁s values in addition to multiple rates of conversion, simultaneously, providing further biological information about the cellular environment of the metabolites.

Miriam W. Lagemaat¹, Marnix C. Maas¹, Eline K. Vos¹, Thiele Kobus¹, Andreas K. Bitz^2,3, Mark J. van Uden¹, Stephan Orzada^2,3, Arend Heerschap¹, and Tom W.J. Scheenen^1,2
1Radiology, Radboud University Nijmegen Medical Centre, Nijmegen, Netherlands, ²Erwin L. Hahn Institute for Magnetic Resonance Imaging, Essen, Germany, ³Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, Germany

We assessed T₁ relaxation times of ³¹P metabolites in the human prostate and evaluated the nuclear Overhauser effect (NOE) as signal enhancement strategy for ³¹P MRSI of the prostate at 7T. T₁ relaxation times were found to be relatively long compared to other human tissues at 7T. To obtain a 3D ³¹P MRSI dataset within a clinically acceptable measurement time (TR ≤ 1.5s) with optimal SNR per unit time, a strongly reduced flip angle (≤ 45°) is required. Signal enhancement by irradiating the water resonance to obtain NOE was successful, yielding up to 42% more signal for PE.