Z-spectroscopy with Alternating-Phase Irradiation.

Magnetization transfer (MT) MRI and Z-spectroscopy are tools to study both water-macromolecule interactions and pH-sensitive exchange dynamics between water and the protons of mobile chemical groups within these macromolecules. Both rely on saturation of frequencies offset from water and observation of the on-resonance water signal. In this work, an RF saturation method called Z-spectroscopy with Alternating-Phase Irradiation (ZAPI) is introduced. Based on the T(2)-selectivity of the irradiation pulse, ZAPI can be used to separate the different contributions to a Z-spectrum, as well as to study the T(2) distribution of the macromolecules contributing to the MT signal. ZAPI can be run at resonance for water and with low power, thus minimizing problems with specific absorption rate (SAR) limits in clinical applications. In this paper, physical and practical aspects of ZAPI are discussed and the sequence is applied in vitro to sample systems and in vivo to rat head to demonstrate the method.

[1]  A. J. Shaka,et al.  APPLICATION OF PHASE-MODULATED CLEAN CHEMICAL EXCHANGE SPECTROSCOPY (CLEANEX-PM) TO DETECT WATER-PROTEIN PROTON EXCHANGE AND INTERMOLECULAR NOES , 1997 .

[2]  Magnetization transfer by simple sequences of rectangular pulses , 1995, Magnetic Resonance Materials in Physics, Biology and Medicine.

[3]  Optimum setting of binomial pulses for magnetization transfer contrast , 2000, Journal of magnetic resonance imaging : JMRI.

[4]  G. G. Stokes.  "J." , 1890, The New Yale Book of Quotations.

[5]  Gottfried Otting,et al.  NMR studies of water bound to biological molecules , 1997 .

[6]  A. Carneiro,et al.  Evaluation of Delayed Neuronal and Axonal Damage Secondary to Moderate and Severe Traumatic Brain Injury Using Quantitative MR Imaging Techniques , 2009, American Journal of Neuroradiology.

[7]  Robert E Lenkinski,et al.  On-resonance low B1 pulses for imaging of the effects of PARACEST agents. , 2005, Journal of magnetic resonance.

[8]  J C Gore,et al.  The role of specific side groups and pH in magnetization transfer in polymers. , 1998, Journal of magnetic resonance.

[9]  Alain Pitiot,et al.  Magnetization transfer phenomenon in the human brain at 7 T , 2010, NeuroImage.

[10]  Jinyuan Zhou,et al.  Detection of the Ischemic Penumbra Using pH-Weighted MRI , 2007, Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism.

[11]  Scott D. Swanson,et al.  Transient Decay of Longitudinal Magnetization in Heterogeneous Spin Systems under Selective Saturation. IV. Reformulation of the Spin-Bath-Model Equations by the Redfield-Provotorov Theory , 1994 .

[12]  Jinyuan Zhou,et al.  Using the amide proton signals of intracellular proteins and peptides to detect pH effects in MRI , 2003, Nature Medicine.

[13]  B. Hills.  The proton exchange cross-relaxation model of water relaxation in biopolymer systems. II: The sol and gel states of gelatine , 1992 .

[14]  Jinyuan Zhou,et al.  Optimization of the irradiation power in chemical exchange dependent saturation transfer experiments. , 2005, Journal of magnetic resonance.

[15]  R M Henkelman,et al.  Quantitative interpretation of magnetization transfer , 1993, Magnetic resonance in medicine.

[16]  R. Balaban,et al.  Magnetization transfer contrast (MTC) and tissue water proton relaxation in vivo , 1989, Magnetic resonance in medicine.

[17]  B. Hills.  The proton exchange cross-relaxation model of water relaxation in biopolymer systems , 1992 .

[18]  Gottfried Otting,et al.  Proton exchange rates from amino acid side chains— implications for image contrast , 1996, Magnetic resonance in medicine.

[19]  R. Bryant,et al.  The dynamics of water-protein interactions. , 1996, Annual review of biophysics and biomolecular structure.

[20]  Ray Freeman,et al.  Selective excitation in Fourier transform nuclear magnetic resonance. 1978. , 1978, Journal of magnetic resonance.

[21]  Craig K. Jones,et al.  Pulsed magnetization transfer imaging with body coil transmission at 3 Tesla: Feasibility and application , 2006, Magnetic resonance in medicine.

[22]  Perunthiruthy K. Madhu,et al.  Bloch Equations Revisited:New Analytical Solutions for the Generalized Bloch Equations , 1997 .

[23]  G. Comi,et al.  Pathologic damage in MS assessed by diffusion-weighted and magnetization transfer MRI , 2000, Neurology.

[24]  S. Swanson,et al.  Transient decay of longitudinal magnetization in heterogeneous spin systems under selective saturation , 1992 .

[25]  R. Bryant,et al.  Nuclear magnetic cross-relaxation spectroscopy , 1990 .

[26]  Jinyuan Zhou,et al.  Quantitative description of the asymmetry in magnetization transfer effects around the water resonance in the human brain , 2007, Magnetic resonance in medicine.

[27]  R M Henkelman,et al.  Pulsed magnetization transfer imaging: evaluation of technique. , 1999, Radiology.

[28]  G. B. Pike,et al.  Quantitative imaging of magnetization transfer exchange and relaxation properties in vivo using MRI , 2001, Magnetic resonance in medicine.

[29]  Gareth A Morris,et al.  Effects of radiation damping on Z-spectra. , 2006, Journal of magnetic resonance.

[30]  Jinyuan Zhou,et al.  Amide proton transfer (APT) contrast for imaging of brain tumors , 2003, Magnetic resonance in medicine.

[31]  S. Forsén,et al.  Exchange Rates by Nuclear Magnetic Multiple Resonance. III. Exchange Reactions in Systems with Several Nonequivalent Sites , 1964 .

[32]  G. Barker,et al.  Precise estimate of fundamental in-vivo MT parameters in human brain in clinically feasible times. , 2002, Magnetic resonance imaging.

[33]  J A Frank,et al.  Perfusion imaging with compensation for asymmetric magnetization transfer effects , 1996, Magnetic resonance in medicine.

[34]  Bennett A Landman,et al.  Water saturation shift referencing (WASSR) for chemical exchange saturation transfer (CEST) experiments , 2009, Magnetic resonance in medicine.

[35]  Risto A Kauppinen,et al.  Proton transfer ratio, lactate, and intracellular pH in acute cerebral ischemia , 2007, Magnetic resonance in medicine.

[36]  R M Henkelman,et al.  Modeling magnetization transfer for biological-like systems using a semi-solid pool with a super-Lorentzian lineshape and dipolar reservoir. , 1995, Journal of magnetic resonance. Series B.

[37]  Susumu Mori,et al.  Mechanism of magnetization transfer during on‐resonance water saturation. A new approach to detect mobile proteins, peptides, and lipids , 2003, Magnetic resonance in medicine.

[38]  R. Henkelman,et al.  Magnetization transfer in MRI: a review , 2001, NMR in biomedicine.

[39]  Jinyuan Zhou,et al.  Chemical exchange saturation transfer imaging and spectroscopy , 2006 .

[40]  Optimization of T2‐selective binomial pulses for magnetization transfer , 1995, Magnetic resonance in medicine.

[41]  Gareth J. Barker,et al.  A comparison between equations describing in vivo MT: The effects of noise and sequence parameters , 2008, Journal of magnetic resonance.