Sep 09 2008
The CT scan feature on the To Live Forever exhibition website seems to have been quite popular (5,588 page views while the exhibition was open, with 23,473 for the landing page) so let’s celebrate with some bonus content. My name is Ed Bachta, and like a couple of the others in the MIS group here, I have a background in scientific visualization. This makes us well suited to work with such things as CT scans of mummies.
During the brainstorming phase for this site, we learned that the Brooklyn team had acquired these detailed scans of Demetrios, and couldn’t resist creating an interactive that would make use of the data. Weeks later, when it was time to begin implementation for the project, Despi brought the discs to my desk and I felt that sense of anticipation that one gets when there are discoveries to be made. It didn’t take long for Charlie, my fellow developer at the IMA, to suggest using Osirix to look at the data (he is more Mac-savvy than I am, and knew of this user-friendly tool).
Now for the fun part. I first looked at the data by simply scanning through slices from head to toe (the great thing about this kind of data is that there is no physical slicing involved, as it can be done virtually). I have seen slices from the Visible Human dataset before, and of course one of the first things of note was the fact that my data was missing a brain. Having the images in front of me, I felt sure that others would enjoy this unique view of a mummy and proceeded to export the most interesting slices. For the final cut I decided to stick with features that a person of average anatomical background such as myself would be able to recognize. With a little thickbox magic and some help from Matt, our web designer, this part of the project was soon complete.
But of course, we couldn’t stop there. I took another look at the data using a technique called volume rendering. When working with CT scans, this technique is essentially virtual X-ray vision. When looking through a window, you observe the scene on the other side because the glass doesn’t absorb much visible light. In the same way, when we “look” through the wrappings in the CT data we can see the bones underneath. However, I did run into a little trouble with something I didn’t expect. When I first brought up the volume rendering of the data, I couldn’t see through the wrappings very well (notice the bright splotches in the full-length image above). Curious as to why this might be, I read more about the mummy in Brooklyn’s blog entries about conservation. It turns out that the exterior of the wrappings is painted with lead paint! To get around this obstacle, I had to apply the technique to a sub-section of the volume, essentially cutting away the linens.
Having revealed the skeleton within the wrappings, I wanted to allow our visitors to be able to view it from multiple angles. I decided to use the Object VR export option. Object VR simulates the effect of rotating an object by using views from evenly spaced positions around the object. By displaying the images in a clockwise or counterclockwise sequence, the object appears to rotate. With a little more help from Matt and thickbox, we were able to present these results as well.
I’m glad to have the opportunity to create these experiences for our visitors, and I’m looking forward to sharing more of my adventures here on the blog.