TRADITIONAL POSTER - ismrm

Poster Sessions
3002. Detection of Proton Chemical Exchange Between Metabolites and Water Using T1ρ MRI
Feliks Kogan 1 , Walter Witschey 1 , Keijia Cai 1 , Mohammad Haris 1 , Ravinder Reddy 1
1 Center for Magnetic Resonance and Optical Imaging, Department of Radiology, University of Pennsylvania, Philadelphia, PA,
United States
Imaging of chemical exchange processes is important as it allows for quantification of specific metabolites. In this study, we developed a new method based
on T1ρ MRI to create image contrast and quantify the exchange of protons between metabolites and water. We showed that this method is responsive to
changes in concentration as well as pH. The sensitivity of this technique scales quadratically with static magnetic field and becomes much more valuable as
high field magnets become more widely available clinically.
3003. Comparison of Chemical Exchange Saturation Transfer (CEST) and T1ρ MRI for Measurement of
Proton Chemical Exchange Between Metabolites and Water at 7T
Feliks Kogan 1 , Walter Witschey 1 , Keijia Cai 1 , Mohammad Haris 1 , Ravinder Reddy 1
1 Center for Magnetic Resonance and Optical Imaging, Department of Radiology, University of Pennsylvania, Philadelphia, PA,
United States
Recent work on imaging chemical exchange processeshas been focused on exploitingchemical exchange saturation transfer (CEST). T1ρ imaging is another
imaging technique which depends on chemical exchange which can be used to image metabolites based on their proton exchange properties. In this study,
we compared the sensitivities of these two techniques for measuring metabolites based on proton exchange. We observed that at 7T, T1ρ imaging has a
higher sensitivity to exchanges processes compared to that of CEST.
3004. Study of Chemical Exchange in the Intermediate Exchange Regime: A Comparison of Spin-Locking
and CEST Techniques
Joonas Arttu Autio 1,2 , Tao Jin 3 , S-G Kim 3,4 , Takayuki Obata 1
1 Department of Biophysics, National Institute of Radiological Sciences, Chiba, Japan; 2 Department of Neurobiology, University of
Kuopio, Kuopio, Finland; 3 Department of Radiology, University of Pittsburgh, Pittsburgh, PA, United States; 4 Department of
Neurobiology, University of Pittsburgh, Pittsburgh, PA, United States
Previous study has demonstrated an indirect MRI detection of hydroxyl protons of small metabolites via chemical exchange saturation transfer. We used an
on-resonance spin-locking (SL) pulse to detect proton exchange for hydroxyl-, amide- and amine-phantoms, and a protein sample. Analysis of spin-lattice
relaxation rate in the rotating frame dispersion over a range of SL B1 fields, resulted in robust estimates for intermediate proton exchange rates and
exchangeble proton site populations. Our results suggest that SL technique with on-resonance irradiation is not sensitive to very slow exchange, but may be
more suited for quantitative study in the intermediate exchange regime.
3005. A Fast, Quantitative T 1ρ Imaging Method
Timo Liimatainen 1 , Olli Gröhn 2
1 Department of Biotechnology and Molecular Medicine, University of Kuopio, Kuopio, Finland; 2 Department of Neurobiology,
University of Kuopio, Kuopio, Finland
A pulse sequence based on gradient echo design was modified to include four hyperbolic secant pulses, following by a signal acquisition. This was repeated
four times to obtain a T 1ρ weighted signal intensity curve with incrementally increasing spin-lock time for single phase encoding step. T 1ρ relaxation times
were compared between developed method and spin echo readout with a T 1ρ preparation pulse train in mice brains. Similar T 1ρ values were obtained with
both methods. The developed method allows acquisition of several incremented spin-lock times within one repetition time enabling faster quantization of T 1ρ
and/or decreased specific absorption rates.
3006. Evaluating Exchange Processes in the Human Brain: Magnetization Transfer Vs Adiabatic Rotating
Frame Relaxation Methods
Silvia Mangia 1 , Michael Garwood 1 , Steen Moeller 1 , Dennis Sorce 1 , Kamil Ugurbil 1 , Shalom Michaeli 1
1 CMRR - Dept. of Radiology, University of Minnesota, Minneapolis, MN, United States
In the present work we investigate the different sensitivity to exchange processes generated at 4T by a variety of preparation pulses. To this aim, we
quantitatively analyzed images from the human brain acquired by preparing magnetization with an off-resonance hard pulse, to exploit the so-called
magnetization-transfer effect, or by preparing magnetization with a series of adiabatic pulses with different modulation functions, to exploit adiabatic
rotating frame relaxation mechanisms. Results demonstrate that the two approaches are sensitive to completely different regimes of exchange, thus
providing complimentary information to characterize the tissue.
3007. Measuring T 1ρ Changes Related to Acidosis and Alkalosis
Hye Young Heo 1 , Nader Dahdaleh 1 , Daniel Thedens 1 , Bradley Bolster 2 , John Wemmie 1 , Vincent Magnotta 1
1 University of Iowa, Iowa City, IA, United States; 2 Siemens Healthcare, Rochester, MN, United States
The purpose of this study is to determine the ability of magnetic resonance (MR) imaging to assess regional pH levels. Both phantom and mouse models
were used to evaluate pH sensitive changes in T 1ρ imaging. A linear relationship was observed between T 1ρ time and pH. In the mouse model, widespread
increases in T 1ρ times during CO 2 inhalation were found consistent with the expected acidosis, whereas reduced T 1ρ times during HCO 3 - injection were found
to be consistent with the expected alkalosis.