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[145] Citation: Abstract
Laparscopic surgical skills evaluation of surgery residents is usually asubjective
process, carried out in the operating room by senior surgeons. By its nature,this
process is performed using fuzzy criteria. The objective of the current studentwas to
develop and assess an objective laparoscopic surgical skill scale using HiddenMarkov
Models (HMM) based on haptic information, tool/tissue interactions and visualtask
decomposition. Methods: Eight subjects (six surgical trainees: first yearsurgical
residents 2xR1, third year surgical residents 2xR3, fifth year surgical
residents 2xR5,
and two expert laparoscopic surgeons 2xES)performed laparoscopic cholecystectomyfollowing
a specific 7 steps protocol on a pig. An instrumented laparoscopic grasperequipped
with a three-axis force/torque sensor located at the proximal end with an additional
force sensor located on the handle, was used to measure the forces and torques.
The hand/tool interface force/torque data was synchronized with a video of the tool
operative maneuvers. A synthesis of frame-by-frame video analysis was used todefine 14
different tyupes of tool/tissue interactions, each one associated with uniqueforce/torque (F/T) signatures. HMMs were developed for each subjectrepresenting t
he
surgical skills by defining the various tool/tissue interactions as states andthe
associated F/T signatures as observations. The statistical distance between theHMMs
representing residents at different levels of their training and the HMMs ofexpert
surgeons were calculated in order to generate a learning curve of selected stepsduring laparoscopic cholecystectomy. Results: Comparison of HMMs betweengroup
s
showed significant differences between all skill levels, supporting the
objective
definition of a learning curve. The major differences between skill levels were: (i)
magnitudes of F/T applied, (ii) types of tool/tissue interactions used and the transition
between them and (iii) time intervals spent in each tool/tissue interaction and the overall
completion time. The objective HMM analysis showed that the greatest difference
in performance was between R1 and R3 groups and then decreased as the level ofexpertise
increased, suggesting that significant laparoscopic surgical capability develops
between
the first and the third years of their residency training. The power of themethodology using HMM for objective surgical skill assessment arises from the fact
that it
compiles enormous amount of data regarding different aspects of surgical skill into a
very compact model that can be translated into a single number representing the distance from
expert performance. Moreover, the methodology is not limited to in-vivo condition as
demonstrated
in the current study. It can be extended to other modalities such as measuringperformance in surgical simulators and robotic systems.
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Updated: Tue Jul 15 23:54:51 2008
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