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Magnetic Resonance Imaging

As well as providing the most important structural tool in modern chemistry, magnetic resonance provides the basis of one of the most powerful imaging techniques available to medicine. Our collaborations with the Departments of Medical Biophysics and Diagnostic Radiology have led to a number of advances in MR imaging techniques, including binomial pulse methods for fat/water signal discrimination and an analysis of relaxation contrast in binomial pulse magnetization transfer contrast experiments. An unexpected by-product of the collaborations was the first complete set of analytical solutions of the Bloch equations, just in time for their 50th anniversary.

More recently we have been investigating methods for mapping brain pH, using Z-spectroscopy to measure the pH-dependent rate of exchange between water and amide protons. One unexpected complication is that in high field systems radiation damping can cause the same sort of Z-spectral asymmetery as amide exchange if care is not taken to ensure that the probe is at exact electrical resonance. Our development of the ZAPI technique allows Z-spectroscopy to probe tissue magnetization pools with different dynamics, generating new sources of image contrast.

Axial rat brain images for magnetization transfer contrast with different timescales

Morris, GA and Freemont, AJ, 1992 Direct Observation of the Magnetization Exchange Dynamics Responsible for Magnetization Transfer Contrast in Human Cartilage In Vitro. Magnetic Resonance in Medicine. 28, 97-104.

Morris, GA, Chilvers PB. 1994. General Analytical Solutions of the Bloch Equations. Journal of Magnetic Resonance Series A. 107:236-238.

Zhu, XP, Hutchinson CE, Chilvers PB, Morris GA, Hawnaur JM, Taylor CJ. 1995. Off-resonance binomial composite pulses in 2D and 3D fat/water imaging at 0.5 T. British Journal of Radiology. 68:134-140.

Zhu, XP, Chilvers PB, Hutchinson CE, Morris GA, Hawnaur JM, Adams JE, Taylor CJ. 1997. Contrast-modified gradient echo imaging using rotary echo preparatory pulses. Magnetic Resonance Materials in Physics Biology and Medicine. 5:193-200.

Williamson, DC, Närväinen J, Hubbard PL, Kauppinen RA, Morris GA. 2006. Effects of radiation damping on Z-spectra. Journal of Magnetic Resonance. 183:203-212.

Närväinen, J, Hubbard PL, Kauppinen RA, Morris GA. 2010. Z-spectroscopy with Alternating-Phase Irradiation. Journal of Magnetic Resonance. 207(2):242-250.