Implement Liu et al. low-res thickness algorithm

[mdoube]

IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING BME VOL 61; NUMB 7 (2014) pp.2057-2069
A Robust Algorithm for Thickness Computation at Low Resolution and Its Application to In Vivo Trabecular Bone CT Imaging
Liu, Y.; Jin, D.; Li, C.; Janz, K. F.; Burns, T. L.; Torner, J. C.; Levy, S. M.; Saha, P. K.

http://dx.doi.org/10.1109/TBME.2014.2313564