Computer Assisted Minimal Invasive Surgery towards Guided Motor Control

1. Computer Assisted Minimal Invasive Surgery towards Guided Motor Control By: Vinay B Gavirangaswamy

2. Introduction • Minimal invasive surgery is practiced over conventional open surgical methods • Advantageous over traditional techniques as it minimizes post operative complications and leave minimum scars on the body • Restricted visibility and dept perception • Difficult to acquire required new motor skills • Difficult to gain experience to develop required motor skills • Very few or no alternatives other than performing actual surgery as teaching method

3. Solution Approach • Increased use of sensors to assist in depth perception • Three-dimensional camera system • Computer Tomography as substitute for improved visibility and depth perception • Computer simulation to act a simulation tool using actual instruments

4. Computer Tomography “Any method that reconstructs internal structural information within an object by mathematically reconstructing it from a series of projections”. Construction techniques • Set of projection • Filtered back projection • Algebraic reconstruction methods

5. Key Terminologies • Constructed using linear attenuation coefficient μ • Depends on element composition and density • Volume element (voxel) a value in three dimensional space, is analogous to pixel in 2D image. • Intensity at voxel is calculated by • - incident intensity • - detected intensity • Sinogram/Radon – View taken from axis position t and at an angle Φ

6. Key Terminologies (Contd.) • Phantom- construction of a planar figure from view points

7. Set of Projections Filtered Back Projections • Uses rectangular co-ordinate system • Projections from all the views contribute too much to the center of the image, and causes overlap (blurring) • Uses polar co-ordinate system • Inverse transformation removes blurring

8. Algebraic Reconstruction Methods • Calculation of linear attenuation coefficient is considered as set of simultaneous equations; written in the form n – number of voxels m – number of projections A – is the matrix of weights x- voxel values b-projection measurements are the b values

9. Algebraic Reconstruction Method Disadvantage (iterative method) Advantages overfiltered back propagation • No single point that represents stable answer • Convergence may not be very fast • When to stop? • Requires small number of view points compared to FBP • FBP view points need to be equally spaced • Acceptable reconstruction is possible through under sampled projections • Can be parallelized* * Similar to Parallel Implementations of Gaussian elimination Vasilije’s Project

10. Refences • J.C. Russ, The image processing Handbook CRC Press (1992) • Raman Rao, Ronald D. Krizet al, “Parallel Implementation of the Filtered Back Projection Algorithm for Tomographic Imaging”, Internet: http://www.sv.vt.edu/xray_ct/parallel/Parallel_CT.html, February 8, 2012