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2 Surgical Training

Medical professionals for centuries have used a training model based on apprenticeship. With this training approach the trainee observes a procedure made by an expert physician and then practices it under the teacher or an expert supervision.

With this traditional approach, many different tools and techniques have been deployed to provide added value to the training process, such as using animals or cadavers or by practicing on mannequins. However, the interactions that occur in an animal's or cadaver's tissues differ from those of living humans due to varying anatomy or absence of physiological behaviour. This type of training can also raise some ethical issues. Mannequins that simulate part or all of a patient anatomy provide a limited range of anatomical variability and also a different response from the living human tissue.

An alternative approach that is becoming more and more accepted by the medical community consists in the use of a virtual reality simulators that can train practitioners on a virtual patient and permit to have a live feedback on the performed procedure. This feedback can then be used to refine the required skills until the operator reaches a target level of proficiency before doing the required procedure on the real patient. In addition, virtual simulations can provide the user the possibility to practice the surgical procedure on rare or difficult medical cases or on virtual models of patients with unconventional anatomy.

3D virtual models offer also the opportunity to be customized. In fact they can be derived from patient medical data in order to replicate the patient's real anatomy and produce a realistic simulation environment.

Laparoscopy is a minimally invasive surgical procedure performed on the patient body through small incisions on the patient skin using long thin tools. The surgeon's view is provided by means of a camera inserted into the patient body. With this kind of "indirect" view and with the manipulation of long surgical instruments, the distance between surgical tool and the organ is difficult to be estimated. For this reason in this surgery field training with virtual simulator is very important [2]. Practitioner needs a long training period using commercial simulators before performing the operation on the real patient.

3 Virtual Surgical Simulators

In the field of surgical simulation, Wang et al. [5] present a physics-based thread simulator that enables realistic knot tying at haptic rendering rate. The virtual thread follows Newton's law and considers main mechanical properties of the real thread such as stretching, compressing, bending and twisting, as well as contact forces due to self-collision and interaction with the environment, and the effect of gravity.

Webster et al. [6] describe a new haptic simulation designed to teach basic suturing for simple wound closure. Needle holders are attached to the haptic device and the simulator incorporates several interesting components such as real-time modeling of deformable skin, tissue and suture material and real-time recording of state of activity during the task.

Le Duc et al. [7] present a suturing simulation using the mass-spring models. Various models for simulating a suture were studied, and a simple linear mass-spring model was determined to give good performance.

Choi et al. [8] explore the feasibility of using commodity physics engine to develop a suturing simulator prototype for manual skills training in the fields of nursing and medicine. Spring-connected boxes of finite dimension are used to simulate soft tissues, whereas needle and thread are modeled with chained segments. The needle insertion and thread advancement through the tissue is simulated and two haptic devices are used in order to provide a force feedback to the user.

Lenoir et al. [9] propose a surgical thread model for surgeons to practice a suturing task. They first model the thread as a spline animated by continuous mechanics. Moreover, to enhance realism, an adapted model of friction is proposed, which allows the thread to remain fixed at the piercing point or slides through it.

Shi et al. [10] present a physics-based haptic simulation designed to teach basic suturing techniques for simple skin or soft tissue wound closure. The objects are modeled using a modified mass-spring method.

LapSim [24] is a commercial surgical simulator that offers a complete portfolio of laparoscopic procedure exercises. It has a modular structure and comprises also a module for laparoscopic suture training.

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