- The Rainbow Technique:An Innovative Approach to the Artistic Presentation of 3D Computed Tomography
Pointillism is a painting style that uses many tiny brush strokes or dots with brilliant colors to form an image . Its most representative artist is Georges Seurat (1859-1891) of the Neo-Impressionist period. His famous painting A Sunday Afternoon on the Island of the Grande Jatte (1884-1886) is a prime example of pointillism .
Inspired by pointillism, I have conceived a new method of visual representation using lines instead of dots as the basic image elements for portraying 3D space. Each line itself is made up of a rainbow of colors. This form of representation can be realized in 3D computed tomography (CT) through selection of appropriate settings in commercially available software. I call this method the "rainbow technique."
I used a 16-slice multi-detector CT scanner  for data acquisition. Actual data derived from human subjects as a result of CT scanning for medical purposes was utilized. Three-dimensional reconstruction was performed using a dedicated medical workstation with direct volume-rendered 3D software in color . The "rainbow technique" utilizes a unique property of CT: 3D reconstruction builds on a stack of thin image slices fed into an appropriate 3D software program. A critical setting can be chosen so that the surface rendering of the 3D object starts to break up into contour lines representing individual slices. This critical setting depends on the window level and window width of the CT image that is optimized for the CT density value of the selected anatomical structure under study. The resolution setting is also critical in producing this effect. The effect is adjusted interactively in virtual reality. A rainbow color spectrum applied to the image at this critical setting using a spike algorithm gives rise to a striking display of colorful bands forming the 3D object (Color Plate A).
The rainbow technique enhances the artistic quality of 3D CT as a tool for creation of visual art. Like pointillism, it adds brilliance and color to the resultant image. The contour line effect is an artifact of 3D CT, and I turn this characteristic to good use. The effect emphasizes form and enhances sharpness and perspective. Given the appropriate setting, a "Venetian blind effect" is obtained, allowing objects both outside and inside an enclosed 3D space to be clearly seen in sharp contour. Objects with densities outside the optimum range for rainbow formation will be displayed in normal 3D rendering, adding scope to creativity by combining the two forms of representation.