Spectroscopic Imaging & Excitation
Tuesday 21 April 2009
Room 315 16:00-18:00

Moderators:

 Daniel M. Spielman and Melissa J. Terpstra
 
16:00  327. Short TE (15ms) Spectroscopic Imaging of the Human Brain at 7T Using Transceiver Arrays and B1 Shimming Based Localization
    Hoby Patrick Hetherington1, Andrey M. Kuznetsov1, Nikolai I. Avdievich1, Jullie W. Pan1
1Neurosurgery, Yale University, New Haven, CT, USA
    The presence of ultra high field systems (7T) dating from late 1990s, there have been few reports of their use in spectroscopic imaging (SI) studies. This limitation is due to the inherent disadvantages of high field which result in a 5-12 fold increase in power deposition at 7T in comparison to 3T. These problems become especially severe when in–plane volume localization is used for SI. To overcome these limitations we have developed a short TE (15ms) SI sequence utilizing an 8 element 7T transceiver array and a B1 shimming based method for in-plane localization.
     
16:12 328. Spectroscopic Imaging Using Wideband Parallel RF Excitation at 7T
    Borjan Aleksandar Gagoski1, Kawin Setsompop2, Joonsung Lee1, Vijay Alagappan2, Michael Hamm3, Axel vom Endt3, Lawrennce Wald4,5, Elfar Adalsteinsson5,6
1Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, USA; 2A. A. Martinos Center for Biomedical Imaging, MGH, Charlestown, MA, USA; 3Siemens Medical Solutions, Charlestown, MA, USA; 4A. A. Martinos Center for Biomedical Imaging, Department of Radiology, MGH, Charlestown, MA, USA; 5Harvard-MIT Division of Health Sciences and Technology, Cambridge, MA, USA; 6Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, USA
    pTx mitigation excitation over a 600Hz spectral bandwidth and a 3 cm thick slab, preceded by pTx Gaussian-shaped pulses for water suppression was used in a chemical shift imaging acquisitions. The goal of this work is to demonstrate that compared to the regular birdcage (BC) mode excitation, the proposed pTx wideband excitation provides spatial uniformity of metabolite signals in a spectroscopy phantom containing physiological brain metabolite concentrations.
     
16:24 329. 1H NMR Spectroscopy in the Human Brain in Vivo at 9.4 Tesla: Initial Results
    Dinesh K. Deelchand1, Pierre-Francois Van de Moortele1, Gregor Adriany1, Peter Andersen1, Kamil Ugurbil1, Pierre-Gilles Henry1
1Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, USA
    We report initial 1H NMR spectroscopy results in the human brain in vivo at 9.4 Tesla despite several challenges for human studies at ultra high-field. The increase in signal-to-noise and spectral dispersion has allowed quantification of at least 15 metabolites with greater precision. As expected, the T1 relaxation time was increased and T2 relaxation time was reduced at 9.4 Tesla.
     
16:36 330. Spectroscopic SWIFT
    Djaudat Idiyatullin1, Curt Corum1, Steen Moeller1, Jutta Ellermann2, Michael Garwood1
1CMRR, University of Minnesota, Minneapolis, MN, USA; 2Radiology, University of Minnesota, Minneapolis, MN, USA
    The ability to obtain chemical shift information is often needed and advantageous in MRI. This work describes a new 3D and 4D spectroscopic SWIFT technique involving an intrinsic frequency dimension. In addition to providing chemical shift information, spectroscopic SWIFT can be used to reduce blurring which normally occurs in radial imaging due to frequency shifts. The presented method can be used for spectroscopy of human tissue having transverse relaxation times, T2, in microsecond time scale. As examples of applications, fat-water separation, imaging near metallic implants, and short T2 mapping are illustrated and discussed.
   

 
16:48 331. Accelerated Proton Echo-Planar Spectroscopic Imaging Using Parallel Imaging and Compressed Sensing
    Ricardo Otazo1, Daniel K. Sodickson1, Akio Yoshimoto2, Stefan Posse2,3
1Center for Biomedical Imaging, NYU School of Medicine, New York, NY, USA; 2Electrical and Computer Engineering Department, University of New Mexico, Albuquerque, NM, USA; 3Department of Neurology, University of New Mexico, Albuquerque, NM, USA
    Compressed sensing and parallel imaging are combined into a single joint reconstruction to accelerate Proton Echo Planar Spectroscopic Imaging (PEPSI). The method exploits the joint sparsity in the sensitivity-encoded images to achieve higher accelerations than for coil-by-coil compressed-sensing or parallel imaging alone. We demonstrate the feasibility of simulated 4-fold acceleration for human brain PEPSI using a standard 12-channel array coil.
     
17:00 332. Gradient Offset Independent Adiabatic Pulses for High-Field MR Spectroscopy on Clinical Scanners
    Ovidiu Cristian Andronesi1, Saadallah Ramadan2, Eva Maria Ratai1, Dominique Jennings1, Carolyn Mountford2, A. Gregory Sorensen1
1Martinos Center for Biomedical Imaging, Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA; 2Center for Clinical Spectroscopy, Department of Radiology, Brigham & Women’s Hospital, Harvard Medical School, Boston, MA, USA
    Adiabatic pulses are necessary to mitigate chemical shift artifact and rf inhomogeneity at high-field MRS, but often they need longer durations (≥ 5 ms) and higher rf strengths (> 1 kHz) that limits their application in-vivo. Gradient offset independent adiabatic (GOIA) pulses have been proposed [1] as an elegant solution to reduce these requirements while effectively increasing the excitation bandwidth (> 20 kHz). Despite of the benefits, their use on clinical scanners has not been widespread. Here we report on a new class of GOIA pulses derived from WURST [3] adiabatic pulses that provide accurate localization and increased SNR at 3T and 7T.
     
17:12 333. Application of HSn Low Peak B1 Adiabatic Refocusing Pulses to Hyperpolarized 13C Spectroscopic Imaging
    Simon Hu1,2, Peder E. Larson1, Adam B. Kerr3, Douglas A. Kelley4, James Tropp4, John M. Pauly3, John Kurhanewicz1,2, Daniel B. Vigneron1,2
1Dept. of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA; 2UCSF & UCB Joint Graduate Group in Bioengineering, San Francisco, CA, USA; 3Dept. of Electrical Engineering, Stanford University, Stanford, CA, USA; 4GE Healthcare, San Francisco, CA, USA
    In order to develop methods for human studies, we modified a previously reported double spin-echo hyperpolarized 13C spectroscopic imaging sequence by using stretched hyperbolic secant refocusing pulses instead of standard hyperbolic secant pulses. The previous pulses used in animal model studies had a nominal B1 of 1.7 gauss, which was achievable with small coils but not with human coils. We designed new pulses with a nominal B1 of 0.4 gauss, which we validated in simulations, phantom experiments, and in vivo.
     
17:24 334. Diffusion-Weighted Line-Scan Echo-Planar Spectroscopic Imaging for Improved Accuracy in Metabolite Diffusion Imaging
    Yoshitaka Bito1, Koji Hirata1, Toshihiko Ebisu2, Yuko Kawai3, Yosuke Otake1, Satoshi Hirata1, Toru Shirai1, Yoshihisa Soutome1, Hisaaki Ochi1, Masahiro Umeda3, Toshihiro Higuchi4, Chuzo Tanaka4
1Central Research Laboratory, Hitachi, Ltd., Kokubunji-shi, Tokyo, Japan; 2Neurosurgery, Nantan General Hospital, Kyoto, Japan; 3Medical Informatics, Meiji University of Integrative Medicine, Kyoto, Japan; 4Neurosurgery, Meiji University of Integrative Medicine, Kyoto, Japan
    A diffusion-weighted line-scan echo-planar spectroscopic imaging (DW-LSEPSI) technique to improve accuracy in measuring diffusion-weighted images of metabolites is developed. The most challenging issue to improve accuracy is to reduce motion artifact induced by cardiac pulsation and respiratory. The developed technique uses line-scan technique and echo-planar technique to reduce the influence of phase errors caused by such motions during diffusion time. Acquisition of accurate diffusion-weighted image and ADC maps of metabolites is demonstrated by applying this technique to a phantom and a rat brain in vivo.
     
17:36 335. Improving Spatial Localization in MR Spectroscopic Imaging with PSF-Choice
    Lawrence Patrick Panych1,2, Joseph R. Roebuck3, Robert V. Mulkern2,4, Yi Tang1,2, Bruno Madore1,2, Nan-kuei Chen5
1Radiology, Brigham and Women's Hospital, Boston, MA, USA; 2Radiology, Harvard Medical School, Boston, MA, USA; 3Radiology, University of Texas Medical Branch, Galveston, TX, USA; 4Radiology, Children's Hospital, Boston, MA, USA; 5Brain Imaging and Analysis Center, Duke University, Durham, NC, USA
    The purpose of this work was to improve the point-spread-function (PSF) of MR spectroscopic imaging (MRSI) to avoid corruption from neighboring voxels. PSF-Choice, a method that uses RF manipulation to shape the PSF in phase-encoding directions, was implemented. Evaluation of the method in extensive phantom experiments was conducted. In addition, an implementation of this method is reported for MRSI of the prostate, where it is demonstrated that, in 13 of 16 pilot prostate MRSI scans, intra-voxel spectral contamination from lipid is significantly reduced compared to a standard phase-encoding MRSI method.
     
17:48 336. Enhanced Polyamine Detection at 7T as a Possible in Vivo Biomarker for Prostate Cancer
    Dennis Klomp1, Tom Scheenen2, Jack van Asten2, Vincent Boer1, Peter Luijten1
1Radiology, University Medical Center Utrecht, Utrecht, Netherlands; 2Radiology, Radboud University Nijmegen, Medical Center, Netherlands
    Additional biological markers may improve prostate cancer diagnoses. In this work we demonstrate the use of chemical shift selective refocusing to substantially enhance the polyamine marker in vivo at a field strength of 7T.