3) Surgical Simulators

Introduction

Surgical Simulation Training is becoming more and more common allowing surgeons to practice performing both routine and complex procedures in order to increase the percentage of successful procedures. Legacy training activities are becoming more costly and are also more time consuming. By simulating these surgeries, doctors can now reduce the time required to get certified to perform all kinds of surgeries.

Surgical Simulation can be achieved by using either hardware or software or a combination of both to help surgeons go through complex and basic procedures. It also allows the standardization of skill sets for establishing training requirements for surgeons so that the qualification level does not vary from one doctor to another. Although simulations training can range from 5 to 200 thousand dollars, the reliance on other expensive training methodologies will be reduced, which will cause it to be cheaper in the long run. [1]

Surgical Education

There is no doubt that we are currently in a point in time where developers are constantly creating higher quality and more advanced surgical simulators. More and more hospitals and doctors are adapting these new surgical training methods in order to train new doctors.

Typical surgical training in the past involved student surgeons watching a more experienced surgeon to learn. However, with the introduction of virtual simulators, doctors use these advanced simulators to create a more standardized approach to this matter.

Although these simulation training methods are currently used only as a supplementary aid, in 2012 the ISCP (Association of Surgeons in Training) curriculum stated that a phased integration into all surgical training programs will be adopted. Studies have shown that simulators have been most successful in the training of laparoscopic surgeries to reduce suture times.

In one case study involving 16 surgical residents, residents that were not given simulation training were five times more likely to injure the patient during the surgery. Also, residents who were training using simulation models in a gallbladder surgery were 29 percent faster than those that did not receive any sort of training. [1][2]

[1]

Surgical Rehearsal

One of the most complicated surgery is Neurosurgery as it required extensive experience and knowledge. Surgical simulation in Neurosurgery allows doctors to gain proficient experience in a controlled environment before having to operate on real patients. Surgical Simulation allows you to incorporate images of real patients who have specific medical problems, and thus the rehearsal can provide a very realistic approach to a complicated surgery for both new and experienced surgeons, similar to that of airplane pilots whom have to fly a specific number of hours on a simulator before being allowed to fly an aircraft. Although the use of simulators for surgeries is still in its early stages, it has shown very promising results.

Surgical Theater has created a technique for reconstructing medical images such as CT and MRI images into interactive 3-D models called the Selman Surgical Rehearsal Platform. It provides the doctor to perform a virtual surgery specific to the patient with the option to plan, rehearse, and perform aneurysm clipping with interactive tools. [3]

Neurosurgical Simulation Devices

There are currently two available devices for training neurosurgeons. They are the NeuroTouch developed by the National Research Counsil in Canada and the Immersive Touch. The NeuroTouch consists of stereovision system, bimanual haptic tool manipulators, and high-end computers. The software for the NeuroTouch is an evolving software that can be updated to allow additional simulation tasks. There are also training tasks that are being developed to allow surgeons hands on experience doing 1 or 2 nostril endonasal surgeries. [4]

"With modules that replicate realistic instruments, imaging, and open neurosurgical procedures, NeuroVR allows risk-free, self-directed practice resulting in reduced medical errors and better patient outcomes." [4]

ImmersiveTouch is also a VR imaging device that allows surgeons to see and feel minimally invasive surgeries to help improve their skills. There are three main steps involved. First the patients CT/MRI images are uploaded onto their cloud. Then, these images are reconstructed so that they can be used in 3D virtual reality. This is also the stage where haptic and tactile feedback is added to the reconstruction to duplicate the real feel of the patient. Finally, all reconstructed images are stores in the cloud for future referencing and utilizing. [6]

NeuroTouch Device [5]

Simulation Components

There are three main components of simulation.

Graphics/Volume Rendering

The most developed parts of a neurosurgical simulation are likely the algorithms that are currently used for creating the 3-dimensional anatomy. Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) is used for constructing 3D volumetric anatomical models using various image processing and geometric modelling techniques. Volume rendering is the technique that these models are usually displayed using. In the last several years, advances that have been made in volume rendering techniques have drastically improved the quality of the realism in current simulators. As a matter of fact, a lot of volume rendering techniques are shared with gaming platforms.

Direct rendering approaches describe an anatomic structure as a volumetric model consisting of cubic elements known as voxels and use image density values to delineate adjacent tissues. Direct rendering produces correct volumetric reflection of the original imaging data, however it does so at the cost of slowing down the fluidity of the simulator due to the extensive computational power required.

Indirect rendering, also known as surface rendering, generates models that describe only the surface of anatomical structures. It does this by ignoring the internal volumetric data and thus reduces the computational power required in doing so drastically thus improving the fluidity of the simulator. Once a structure has been segmented from its adjacent tissue, it can be assigned appropriate visual and biomechanical properties. [7]

Image Rendering [8]

Model Behavior/Tissue Deformation

Volume-rendered models should be able to respond to user manipulation with virtual tissue deformation in order to aid simulation. In real-time simulators, the mass-spring method is a common approach to tissue deformation which describes each point, or voxel, as mass that is linked to neighboring points by a spring. In other terms, the tension at one point in the model is conveyed into surrounding tissue as a spring being stretched by an applied mass. One of the main drawbacks of this method is the inability to accurately depict a surgical cut. [7]

Haptic Feedback

Haptics in the field of surgical simulation usually refers to the simulation of touch by applying forces, vibrations, or motions to the user in order to give it a real feeling. Haptic feedback is usually transmitted to the user via some sort of physical interface such as a laparoscopic device with a computer based graphic model. It basically relates what is seen on the screen with a realistic sensation of touch. Most affordable neurosurgical simulators do not provide accurate haptic feedback, but rather an animated tissue deformation as these simulators are more common and inexpensive. However, within the last several years, the development of tactile sensation in neurosurgical simulation surgeries has drastically improved making haptic feedback an important element in true simulation. [7]

Haptic Feedback Simulation [9]

EDEN 2020

EDEN2020 is a large Research and Innovation Action project that started in 2016 and is set to last for up to 4 years. It is designed to help develop an integrated one stop platform for diagnosing and performing minimally invasive treatment in neurosurgery. [10]

[11]

The EDEN 2020 project will both develop and test a steerable robotic needle that is flexible to reach areas in the brain and treat them. It is meant to minimize risk of brain surgery for patients. In the treatment of brain gliomas, which is dangerous and aggressive tumor in the brain, a rigid needle is used which makes it hard to avoid obstacles on the path of the tumor. The EDEN 2020 will establish trajectory to be followed through human tissue. Over the past decade, the team at Imperial College London has succeeded in creating the first prototypes for flexible, miniaturized needles. Now an extended group of researchers are working together with industrial partners to carry out the first pre-clinical tests on animals.

Thanks to modern magnetic resonance techniques, such as diffusion-weighted MRI, it possible to study the nervous tissue structure and the organisation of the connections between different areas of the brain. A team of neuroradiologists will provide high-resolution images allowing the surgeon to visualize the tissue affected by the tumor in detail. The resulting images will be used to plan the path of the robotic needle, which the neurosurgeon will then guide using a special joystick. An exteroceptive system, located on the outside of the needle will track its position through intra-operative ultrasound imaging, while a sensory system on the needle will measure the needle’s curvature, ensuring adherence to the planned path and absolute safety for the patient.The surgeon will therefore be able to visually monitor the progress of the robotic needle until it reaches the desired treatment site, where the medication will be released through the needle. [11]

EDEN 2002 has 7 goals to achieve including:

1) To engineer a family of steerable catheters for chronic neuro-oncological disease management that can be robotically deployed and kept in situ for extended periods.

2) To control robotic, steerable catheters with enhanced autonomy, surgeon cooperation, targeting proficiency and fault tolerance.

3) To sense and perceive intra-operative, continuously deforming, brain anatomy at unmatched accuracy, precision and update rates.

4) To model, understand and predict drug diffusion properties within brain tissue with unprecedented resolution and comprehensiveness of factors.

5) To study in vivo diagnostic sensing in flexible access surgery.

6) To build a unique database of paired clinical datasets (human and ovine) that includes registered information regarding anatomy, white matter tracts, histology and microstructure.

7) To create a pre-commercial technology platform for neurosurgical catheter insertion that exploits the technological and clinical outputs of all other objectives. [10]

Conclusion

Currently, the limitations of computer based neurosurgery are due to the computational burden of accurate tissue deformation, the grueling process of manually segmenting volume-rendered models, and the expense of advanced haptic interfaces. Although there are some limitations, the potential in the development of models are very valuable as they are excellent for alternate procedures. [7]