Quantitative Characterization of Components of Computer Assisted Interventions

by   Asli Okur, et al.
Technische Universität München

Purpose: We propose a mathematical framework for quantitative analysis weighting the impact of heterogeneous components of a surgery. While multi-level approaches, surgical process modeling and other workflow analysis methods exist, this is to our knowledge the first quantitative approach. Methods: Inspired by the group decision making problem from the field of operational research, we define event impact factors, which combine independent and very diverse low-level functions. This allows us to rate surgical events by their importance. Results: We conducted surveys with 4 surgeons to determine the importance of roles, phases and their combinations within a laparoscopic cholecystectomy. Applying this data on a recorded surgery, we showed that it is possible to define a quantitative measure for deciding on acception or rejection of calls to different roles and at different phases of surgery. Conclusions: This methodology allows us to use components such as expertise and role of the surgical staff and other aspects of a given surgery in order to quantitatively analyze and evaluate events, actions, user interfaces or procedures.



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1 Introduction

Inside an operating room (OR) a large number of interactions happen on a regular basis. With the introduction of more advanced technical equipment such as imaging or navigation systems, these interactions are becoming even more complex. Every action inside the OR is majorly influenced by different sources, unique to each particular intervention, such as the team constellation and individual characteristics of the staff members. These influences can be very diverse, and quantifying them as a single measurement is not trivial. This paper aims at introducing mathematical methods for impact calculation for events happening inside the OR, and their use in analysis of surgical processes and related computer assisted solutions.

Figure 1: Actions inside the OR are influenced by different sources such as surgical workflow, human roles, devices and surgical tools. Image courtesy of Armin Schneider, MITI, TUM.

Reaching decisions with multiple independent parameters has been under study for several years in operational research. Diverse mathematical models have been developed to help groups decide and act in complex situations. These methods have not yet been widely utilized in the medical domain, despite the importance of different factors when analyzing surgical processes.

A first step towards dividing a surgery into statistically reproducible phases and their characteristics are design and recovery of surgical process models Neumuth2011; Bouarfa2012a; Padoy2010. This analysis and its use in monitoring of the surgical workflow are important prerequisites to design and implement any advanced intraoperative system. Jannin et al. jannin2008 introduced an assessment system for image guided interventions based on six levels. Bigdelou et al. bigdelou2011ipcai proposed a method for usability analysis of computer assisted surgery solutions by defining items within different views in an OR specific domain model. However, they do not provide a mathematical method allowing quantified analysis and in particular measuring the impact of different elements of such models.

In this work we bring a new methodology into the domain of computer assisted interventions in order to determine the impact of surgical events based on different components of the OR. The aim of the rating should be chosen according to an intended study by adjusting the component characteristic functions (CCF) introduced in

LABEL:sub:ccf. This enables many possible applications improving any aspect of a surgery such as patient outcome, surgery duration or healthcare costs. Here we chose a more immediate approach to minimize human error, by evaluating whether a possibly disturbing incoming phone call should be rejected during any point of an intervention.

2 Impact Calculation

The OR domain model proposed by Bigdelou et al. bigdelou2011ipcai consists of three distinct views: surgical workflow, target device and human roles. Mappings are defined as the correlation between two elements of different views. These are represented in mapping tables, which are useful for analyzing the complex connections between views.

Although this model provides a better analysis of the complex OR domain, it lacks a mathematical method allowing quantified analysis. As some surgical workflow phases might be more critical than others or some human roles are much more important than the remaining ones, an intelligent way to distinguish the influence of some view elements on the surgery is required. In this section we will introduce the methodology for impact determination for individual surgical events and clarify it with application examples.

Please note that the methodology we use for impact calculation is inspired by the Group Decision Making Problem (GDM), which has been studied in the field of Operational Research for more than 20 years now. In GDM the opinions of different human experts are intelligently combined to a single, collective opinion to determine the best of several alternatives, e.g. choosing as a group which university to study at, based on different, independent parameters such as costs, reputation, number of professors, social life etc. The approach most suitable to our model was described in herrera_multiperson_2001, while one of the first works in this field was done by Saaty Saaty1990. A very important factor in GDM are the employed similarity measures and combining operators, which are compared and described in Chiclana2012. Usual GDM problems can be found in consensus systems and virtual communities Alonso2010. There have been some applications to the medical domain, but only in a very generic and limited fashion Perez2010.

2.1 Surgical Events

An event is a tuple of different components describing the event, as seen from the different views. The whole surgery can be seen as the finite set of all events that happen within the surgery.