This article first appeared in MAKE Volume 38, on page 112.
By far the most interesting class I’ve ever taken was advanced brain imaging in graduate school, which introduced me to what I believe are some of the most amazing machines humans have ever built: the magnetic resonance imager (MRI) and computed tomography (CT) scanner. These are volumetric 3D scanners that allow you to scan not only the surface of an object, but also see inside that object. And I really wanted to build one.
These scanners are fantastically expensive, and usually only found in hospitals. As a Canadian living abroad, I recently had my first real contact with the U.S. health care system, and it was a very uncomfortable experience. Without belaboring the point, universal health care is very important to me. It’s something that many consider a basic human right, and most people in the developed world, except for the U.S., have access to it. After seeing the cost for my CT scan, I decided it was time to try to build an open source desktop CT scanner for small objects, and to do it for much less than the cost of a single scan.
Mechanically, this prototype scanner is very similar to the first generation of CT scanners, and it’s almost entirely laser cut. An object is placed on a moving table that goes through the center of a rotating ring. Inside the ring there’s a very low intensity x-ray source, and on the other side a detector. An Arduino Uno with a custom shield controls four stepper motors and interfaces with the detector. For safety I’m using a radioisotope x-ray source that’s barely above background levels, so every photon counts, and I’ve only just recalibrated the detector. I’m expecting the first images with a few more weekends of work.
I confess that I laughed and started to feel like Doc Brown when the “only” thing my CT scanner needed was something radioactive, but with luck projects like this will mature into desktop scanners for the maker community, and perhaps even medical scanners for impoverished countries, where they’re most needed.
Build notes, additional photos, and more: tricorderproject.org/openct