An MTF method immune to aliasing.

@article{Drge1985AnMM,
  title={An MTF method immune to aliasing.},
  author={Raimund Dr{\"o}ge and Mark S. Rzeszotarski},
  journal={Medical physics},
  year={1985},
  volume={12 6},
  pages={721-5}
}
The variance derived from the images of cyclic bar patterns can be used to determine the modulation transfer function (MTF) of an imaging system. Unlike most MTF methods, it is applicable even when the imaging system undersamples the test object and generates aliasing errors. The validity of the variance method in the presence of aliasing is established theoretically and by computer simulation.