  Information theory provides a spectrum of nonlinear methods capable of
grasping an internal structure of a signal together with an insight into its
complex nature. In this work, we discuss the usefulness of the selected entropy
techniques for a description of the information carried by the surface
electromyography signals during colorectal cancer treatment. The electrical
activity of the external anal sphincter can serve as a potential source of
knowledge of the actual state of the patient who underwent a common surgery for
rectal cancer in the form of anterior or lower anterior resection. The
calculation of Sample entropy parameters has been extended to multiple time
scales in terms of the Multiscale Sample Entropy. The specific values of the
entropy measures and their dependence on the time scales were analyzed with
regard to the time elapsed since the operation, the type of surgical treatment
and also the different depths of the rectum canal. The Mann Whithney U test and
Anova Friedman statistics indicate the statistically significant differences
among all of stages of treatment and for all consecutive depths of rectum area
for the estimated Sample Entropy. The further analysis at the multiple time
scales signify the substantial differences among compared stages of treatment
in the group of patients who underwent the lower anterior resection.
