Oral Presentation Australian & New Zealand Society of Magnetic Resonance Conference 2017

Insight into Chemical Exchange Inversion Transfer (#24)

Johnny Chen 1 , Nirbhay N. Yadav 2 , Tim Stait-Gardner 1 , William S. Price 1 , Gang Zheng 1
  1. Nanoscale Organisation and Dynamics Group, Campbelltown, NSW, Australia
  2. Kennedy Krieger Research Institute, Baltimore, Maryland, USA

Chemical exchange saturation transfer (CEST) has been used extensively to indirectly detect low concentration metabolites via the water magnetic resonance signal.[1] To achieve this, the magnetisation of the metabolites’ labile proton pool is saturated using a long, low-powered RF pulse. Simultaneously, chemical exchange with water causes a reduction in the z-magnetisation of the water proton pool (i.e., transfer of Mz,solute = 0 to Mz,water). Therefore, this CEST effect can be used to quantify exchange rates, metabolite concentrations, pH, and temperature changes. Theoretically, up to twice the CEST effect can be achieved by inverting the labile proton pool magnetisation, due to the transfer of Mz,solute = -M0,solute to Mz,water. This can yield higher resolution CEST effects, which is particularly useful in in vivo imaging where low signal-to-noise ratio is problematic. In this study, insight into the use of labelling transfer modules (LTM’s) for chemical exchange inversion transfer (CEIT) is presented via simulation results.[2] The challenges in optimising labelling and mixing times to maximise the CEIT effect for different exchange regimes are also discussed. The simulations are performed by numerically solving the Bloch-McConnell equations for a two-pool exchange system.[3]

  1. Van Zijl, P.C.M. and N.N. Yadav, Magn. Reson. Med., 2011. 65(4): p. 927-948.
  2. Friedman, J.I., M.T. McMahon, J.T. Stivers, and P.C.M. Van Zijl, J. Am. Chem. Soc., 2010. 132(6): p. 1813-1815.
  3. McConnell, H.M., J. Chem. Phys., 1958. 28(3): p. 430-431.