This paper focuses on the evaluation of a prototype for a computer-based
tutoring system for prostate cryosurgery, while reviewing its key building
blocks and their benchmark performance. The tutoring system lists geometrical
constraints of cryoprobe placement, displays a rendered shape of the prostate,
simulates cryoprobe insertion, enables distance measurements, simulates the
corresponding thermal history, and evaluates the mismatch between the target
region shape and a pre-selected planning isotherm. The quality of trainee
planning is measured in comparison with a computer-generated plan, created for
each case study by a previously developed planning algorithm, known as
bubble-packing. While the tutoring level in this study aims only at geometrical
constraints on cryoprobe placement and the resulting thermal history, it creates
a unique opportunity to gain insight into the process outside of the operation
room. System validation of the tutor has been performed by collecting training
data from surgical residents, having no prior experience or advanced knowledge
of cryotherapy. Furthermore, the system has been evaluated by graduate
engineering students having no formal education in medicine. In terms of match
between a planning isotherm and the target region shape, results demonstrate
medical residents’ performance improved from 4.4% in a pretest
to 37.8% in a posttest over a course of 50 minutes of training (within
10% margins from a computer-optimized plan). Comparing those results
with the performance of engineering students indicates similar results,
suggesting that planning of the cryoprobe layout essentially revolves around
geometric considerations.