Simulation of patient loading in nuclear magnetic resonance imaging through the use of inductive damping loops

The quantitative assessment of the imaging performance of nuclear magnetic resonance (NMR) scanning equipment requires the use of test objects (Orr et al, 1983; Lerski et al, 1984). These are commonly constructed from perspex and are filled with aqueous solutions of paramagnetic salts (e.g. CuSO4 or MnCl2) to provide the NMR signal with a relaxation behaviour (T1 in particular) similar to tissue. The presence of the human body during the NMR imaging procedure has the effect of loading the receiver coil. This is due to energy dissipation by currents induced in the conducting tissue. The solutions of paramagnetic salts do not provide conducting pathways and subsequently have very little loading effect. The signal-to-noise ratio is degraded by coil loading and falsely high values will be obtained if measurements are made without matching this effect when using test objects. Saline-filled containers can be used to load receiver coils, but these may be difficult to construct and may interfere with the position...