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/.

Corresponding BibTeX entry:

  @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/},
  }