Creating Body Surfaces of the Visible Human Male using IsoSurf

Sharad P. Bhooplapur

Supervised by Drs. R. Martin Arthur and Jason W. Trobaugh
Department of Electrical and Systems Engineering
Washington University in St. Louis
Spring 2005

Introduction

Surface models of the human body are used in electrocardiography to:

  1. Predict the electric potential on the body surface based on known electric potential on the heart surface (forward process), and
  2. Estimate the potential on the heart surface based on measured potentials from the body surface (inverse process).
The aim of the independent study was to develop new surface models using software called IsoSurf created by Dr. Graham Treece at the University of Cambridge, UK.  The input data to IsoSurf are given by the value of points in 3D space. A surface linking the points corresponding to a specified value of the parameter is called an isosurface.

Anatomical data were obtained from the Visible Human Project.  In work done previously by Dr. Arthur, points on the surface of the body were extracted from slices of the body from the Visible Human Project.  After resampling the data points, they were plotted as contours at particular value along the axis of the body.  Contours were separated by 10 mm. The image below displays contours from the head and shoulders in millimeters.

contours
Contours representing data points on the surface

Generating the body surface

The three main steps in generating a surface from anatomical data using IsoSurf are:

  1. Obtaining contours from the anatomical data.
  2. Filling in the contours to generate filled slices.
    This was done using a simple polygon fill algorithm.  Details on the fill algorithm can be found at the Rochester Institute of Technology computer science department:
    http://www.cs.rit.edu/~icss571/filling/
  3. Passing the filled slices to IsoSurf along with other input parameters to generate a triangulated surface, which can be viewed and used for calculations in electrocardiography.

Process of Generating a surface using IsoSurf
unfilled contour This plot displays the contours in millimeters taken from one image of the Visible Human Male. The contours were formed by joining surface points in sequence.
filled contour This image displays the contour above filled using a polygon-fill algorithm.
filled contour Using multiple such filled slices, the surface was generated then displayed using Matlab.

Interactive 3D torso surface model

In the java applet below, you can view a 3D surface model of the torso. The caps at the top and bottom of the model were omitted so that the interior is also visible.

Loading sample geometry.

Press right mouse button to select major interaction mode from popup menu, or use keyboard keys to temporarily switch between different modes (just keep a button pressed to switch mode temporarily). Some essential modes are:

o Rotate surface (this Orbit mode is the default mode)
s Scale surface, drag in vertical direction
t Translate surface in viewing plane
r Reset camera and display, object returns to default position

F1 or Ctrl-s
or
Right-Mouse

Show control window
Help With all keyboard shortcuts, and help on problems.

To modify appearance of the geometry press F1 or Ctrl-s to open the control panel and select the material panel (if not visible) via menu Inspector - Object - Material. Be sure that the mouse focus is inside the viewer otherwise, e.g., the window manager might react. To hide the control panel press F2.

The java applet is made possible by using JavaView, a freely available 3D geometry viewer and a mathematical visualization software which can be obtained from JavaView's website
8th June 2005

 Sharad P. Bhooplapur  

Edited by R. M. Arthur, 9 September 2005.