What is the modulation transfer function?
The modulation transfer function (MTF) originated in optics. Modulation speaks of variation of some property. In optics, the MTF described the ability of a lens to accurately transfer visual stimuli (through the lens). Degradation occurs as light passes through a lens, and the MTF characterised the extent of the degradation. Although in MRI we aren’t using lenses, we still need to describe the extent of the degradation of the representation of an imaged object, compared to the original object. That’s what the MTF does. The initial “modulation” of an object ranges from fine to coarse detail. Obviously fine detail (or modulation) is lost first, as degradation increases. The MTF is simply the modulation of the image (Mi) divided by the modulation of the original object (Mo). MTF (ν) = Mi / Mo The ν symbol is spatial frequency. What’s that about? Well, the ability of a lens (or MRI machine) to transfer say thick lines, as opposed to thin, close lines will be different. The thinner and clos
