Figure 1

Cardiac MRI techniques. These include (a) Cardiac cine imaging (top) and cardiac tagging (bottom) at diastole (left) and systole (right), showing how a rectangular grid of nulled signal applied at diastole remains with the tissue through the cardiac cycle, allowing calculation of strain and torsion. (b) Tagging in two parallel sections allows the calculation of the torsion (the longitudinal-circumferential shear angle ϒ) between two short-axis planes a distance d apart with radius r where one short-axis plane rotates through ΔΦ relative to the other. ϒ = tan⁻¹[(2r sin(ΔΦ/2))/d]. (c) Phosphorus spectroscopy from a control subject (PCr/ATP = 1.95). Spectrum presented before correction for saturation due to blood content, flip angle at the cardiac tissue and heart rate.