In MRI machines, greyscale intensity is related to the strength of the signal emitted by proton particles during relaxation, and after the use of very strong magnetic fields. As different tissues have varying concentrations of protons, different greyscale intensities are used to create the image. By comparison, in a CT scan, the greyscale intensity at a particular voxel relates to the X-ray absorption by the subject at a particular location.
From these processes, a reconstructed image volume is obtained: Raw data taken from a CT or MRI scanner is converted into tomography images for visualization, which is typically completed using the software associated with the scanner itself. A 3D bitmap of greyscale intensities is the result, wherein a voxel (3D pixels) grid is produced. This image data can then be imported to software and visualized in different ways.
For example, in Synopsys Simpleware software, 3D image visualization can involve the following options:
- The background volume can be GPU rendered for quick and easy visualization of the 3D data, creating a realistic object that can be interacted with by the user.
- Live 3D rendering can be used to carry out instant changes to the image, including lighting, transparency, background gradients, and model shading, making it straightforward to create a more realistic-looking model, depending on the application.
- 3D stereoscopic visualization can be applied, for example in modes such as checkerboard, anaglyph, and crystal eyes, to provide a different perspective on the image data.