To cite dti in publications use:

Joerg Polzehl, Karsten Tabelow (2009). Structural Adaptive Smoothing in Diffusion Tensor Imaging: The R Package dti. Journal of Statistical Software, 31(9), 1-23. URL http://www.jstatsoft.org/v31/i09/.

For the underlying methods please cite:

Karsten Tabelow, Joerg Polzehl, Vladimir Spokoiny, Henning U. Voss (2008). Diffusion Tensor Imaging: Structural Adaptive Smoothing. NeuroImage, 39(4), 1763-1773. doi:10.1016/j.neuroimage.2007.10.024

Corresponding BibTeX entries:

  @Article{,
    title = {Structural Adaptive Smoothing in Diffusion Tensor Imaging:
      The {R} Package {dti}},
    author = {J\"org Polzehl and Karsten Tabelow},
    journal = {Journal of Statistical Software},
    year = {2009},
    volume = {31},
    number = {9},
    pages = {1--23},
    url = {http://www.jstatsoft.org/v31/i09/},
  }

  @Article{,
    title = {Diffusion Tensor Imaging: Structural Adaptive Smoothing},
    author = {Karsten Tabelow and J\"org Polzehl and Vladimir Spokoiny
      and Henning U. Voss},
    journal = {NeuroImage},
    year = {2008},
    volume = {39},
    number = {4},
    pages = {1763--1773},
    doi = {10.1016/j.neuroimage.2007.10.024},
  }