computer assisted surgical intervention

Shah Hrishi

Shivaswamy Anirudh

Introduction

“Computer-assisted intervention” is defined as the use of automated systems in surgery

Two different approaches : As a tool (assisting the surgeon)An autonomous system (replacing the

surgeon) Several assistive systems are available, but

the autonomous systems are still in the development stages

History

First robot-assisted surgery performed in 1985, for treating brain lesions

First robot-assisted orthopedic surgery was performed in 1991

In 1991, the first patient was treated with Probot, for prostate cancer.

Newer version of Probot

Classification of surgical systems Surgical Robots Service Robots Prostheses Simulators Robots for diagnosis Passive manipulators Assistive Robots

Surgical Robots

Surgical robots can be tele-manipulators or preprogrammed robots

Tele-manipulators are handled by the surgeon during surgery (intraoperative images used)

Preprogrammed robots are guided by a fixed plan (preoperative images used)

Workflow of tele-manipulators

Typical Workflow of surgical robots

Service Robots.

These are used for rehabilitation They have some pre-programmed

movements which help the patient regain lost functionality

A vision system may be present to support interaction

Simulators

Simulators help in training/ assessment of surgeons

Able to simulate a wide variety of situations

Not subject to the constraints of practicing on humans/animals

Simulator for Orthopaedic operation

Applications

•Orthopaedics

•Urology

•Radiosurgery

•Biopsies / interventional radiotherapy

•Endoscopy/Colonoscopy/Endoscopy

•Cardiac Surgery

•Neurosurgery

•ENT Surgery

•Oral/Cranio-maxillofacial surgery

Orthopaedics.

The operation procedure consists of four main steps:Image acquisitionPlanning with OrthodocRegistration in the operating theatreMilling the cavity by the robot

Examples are RoboDoc, Acrobot, CRIGOS

Parallel Link Robot CRIGOS

Urology.

Probot used for transurethral resection of the prostate

Both imaging and cutting done in the operating theatre - no pre-operative planning required

Main steps:Measuring gland size with ultrasoundImaging and cavity designCutting

Radiosurgery. Main steps:

Image acquisition of CT/MR scansSegmentation and modeling of tumorPlanning of radiation procedureExecution of intervention

Dose distribution and various directions of dose delivery help to protect vital organs from radiation.

Examples:Accuray CyberknifeHitesys NOVAC7

Accuray Cyberknife

Endoscopy/Colonoscopy/Laparoscopy

Surgeon can’t handle instruments and camera at the same time

Other manual control leads to errors so robot control is preferred

Robot may be controlled by surgeon’s head movement.

Examples:EndoassistAesop

Endoassist in operation

Cardiac Surgery.

Generally system consists of a master console and a slave manipulator that executes the commands in the thorax.

Instruments and endoscope inserted through small incisions.

Examples: Zeus, DaVinci.

DaVinci robot in operation

Case study – Needle Insertion…IntroductionIntroduction

Main aim is to avoid obstacles and reach target with minimum invasion

Flexible needle modeled as beam with virtual springs and approximated as a 7 degree polynomial

Initial path planning done Real time correction Experimental verification

Overall setup of system

Case study – Needle Insertion…

Virtual Spring ModelVirtual Spring Model Tissue forces are non-linear with strain –

so modeled as combination of tangential friction force and lateral springs.

Needle broken up into a number of segments at the spring attachment points

Tissue interaction modeled as springs Linear system model

Case study – Needle Insertion…

Forward / Inverse KinematicsForward / Inverse Kinematics Generally, forward kinematics required

to ascertain position of needle end-point from known needle base parameters.

In this scenario, inverse kinematics is done for each point on the planned path to ascertain needle base parameters for this position.

Case study – Needle Insertion…

Path Planning / OptimizationPath Planning / Optimization Relates to finding a path that connects

the target to the needle insertion point while maintaining minimum needle curvature.

Orientation of needle tip unimportant- infinite paths possible.

Minimize sum of squares of virtual spring displacements and slopes.

Multiple solutions for path with same endpoint

Case study – Needle Insertion…Control Loop.Control Loop.

Input is desired needle target excluding its orientation (optimized by controller).

Controller does inverse kinematics and optimization to minimize needle deflections.

Control Loop Diagram

Case study – Needle InsertionNeedle Detection.Needle Detection.

Needle end-point detected by comparison with reference image and rest of needle tracked using low-gradient area.

Full image comparison done only once Needle length also checked Needle fitted using 7 degree polynomial

Actual Needle profile from Fluoroscopy Interpolated needle profile

Current Trends…

MRI-compatible materials / mechatronics / actuators

Safety studies Incorporating haptic feedback into surgical

systems

Challenges/Future Scope

Robotic systems are not usable for routine treatment

Unlike industrial robots, medical robots need to operate in conjunction with the operator

Ease of training and assessment Minimally invasive surgery

References Various product websites ( Prosurgic,

Intuitive etc.) “Robots in the operating theatre—

chances and challenges” - Korb, Marmulla et. al. , Int. J. Oral Maxillofac. Surg. 2004(33)

“Image-Guided Robotic Flexible Needle Steering” – Shoham, Glozman, IEEE Trans. Robotics Vol.23 No.3

Encyclopedia Britannica