Magnetic Resonance Image Volume Rendering of a Human Head

Virginia Tech
Reference:
Daniel Carr, Precision Visuals (now Visual Numerics, Inc.), Boulder, CO, 1991.
Problem Statement
From a sequence of 2-D slices the 3-D volume image of a human head cannot be seen with shade surfaces. The objective is to view all the data in the volume at once. Here a translucent feature is used such that brighter portions of an image (that represent regions of higher concentration of carbon) can be more easily seen embedded inside a volume shown in a larger format.

Larger Image
Click on this image to better view the details in a larger image.

Visual Insight
Without rotation it is impossible to determine the location of regions of higher carbon concentration. With rotation, the locaton of high carbon concentrations is discerned by the human eye as a perceived depth. This ability for the human mind to reconstruct a series of 2D images into a 3D volume of information is exactly the same reconstruction done when we backproject an image that was filtered by using convolution or fourier transform methods. Indeed for the resolution needed in practice this reconstruciton is a time consuming numerical calculation but the human "mind's eye" does it effortlessly. For a more complete explanation of the filtered back projection numerical techniques see the section on X-Ray Tomography and a recent Master Thesis "Parallel Implementation of the Filtered Back Projection Algorithm for Topographic Imaging". Obviously this visual data analysis tool has a broad base use for other applications where it is important to view gradients or detect discrete structures within a 3D volume.

Rotating Animation
Click on this image to view an animation of a translucent rotating head.

How to create Translucent Images
This animation is created by using translucent voxel volume elements. There are several visualization software packages that can create translucent voxels volume elements. Here we have posted a copy of the PV-Wave procedure file and a binary data set (filename: man_head.exe, 905625 bytes) located on our anonymous file server ftp.sv.vt.edu/pub/MRI-Head that were used to create this example. NOTE: the file "man_head.exe" must be renamed "man_head.dat" before you use the provided PV-Wave procedure file. You will notice that the procedure file is amazingly simple and is easily adapted to be used with other data sets.
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Send comments to: kriz@wave.esm.vt.edu
Ronald D. Kriz
Virginia Tech
College of Engineering
Revised December 3, 1995

http://www.sv.vt.edu/class/esm5984/GenInfo/Insights/carr/carr.html