Jansen [i] built an open-source desktop CT scanner (see figure 1) for small objects. The complete design files are available online, [ii] including the mechanical design, circuit schematics and firmware. The CT scanner uses a very low intensity radioisotope X-ray source, which means that even low resolution images take hours of measurement. [iii] It is designed for academic and educational purposes, but the hope is that it could eventually be used as a medical scanner in developing countries.
Jansen designed the almost entirely laser-cuttable CT scanner with four axes of motion, one being a large rotary gantry. The stepper motor to rotate the gantry is a National Electrical Manufacturers Association (NEMA)17 stepper from open-source hardware distributor Adafruit ($14), which transfers motion to the drive shaft using a belt and timing pulleys. Each linear axis has a small carriage that contains mounts for either the source or detector. Each axis has an inexpensive NEMA14 stepper also from Adafruit (under $14) and an idler pulley. [iv] Jansen has used a very small solid state high-energy particle detector called the type-5 from radiation watch, which can be connected to an external microcontroller. The price of this particle detector is just under $80.
Figure 1 Open-source CT scanner (Photo by Peter Jansen, image licensed under the Creative Commons BY-SA license).
To test out the motion and detector, Jansen put together an Arduino shield ($45) with three Pololu stepper controllers [v] and a connector for the detector. An SD card slot can store the image data for large scans.
The source of radiation used in Jansen’s design is Barium-133 (cost between $80 and $125.00) with
80–383 KeV energy. This radioisotope check source is sealed in epoxy, and is of such low intensity that it not licensed [vi] and considered safe unless the material is digested or taped to the body for long periods, and it can be disposed of as general trash. The total cost of Jansen’s open-source CT scanner (excluding the laser cutter) is about $300. Open-source laser cutters can be built for around $1000. All required components are readily available and only basic knowledge of electronics and laser cutting is required.
[i] Jansen P. Open Source CT Scanner. Make 2014;38:112.
[ii] Jansen P. OpenCT GitHub repository. https://github.com/tricorderproject/openct. http://www.webcitation.org/6YgdAQOjB
[iii] Jansen P. The Tricorder Project: OpenCT. http://www.tricorderproject.org/blog/tag/openct/. http://www.webcitation.org/6ZBDB4gwW
[iv] Inventables. Smooth Idler Wheel Kit. https://www.inventables.com/technologies/smooth-idler-wheel-kit.http://www.webcitation.org/6aVTbray4
[v] Pololu. Stepper Motor Drivers. http://www.pololu.com/catalog/category/120.http://www.webcitation.org/6aVTjJFpK
[vi] Images Scientific Instruments. Radioactive sources. http://www.imagesco.com/geiger/radioactive-sources.html. http://www.webcitation.org/6aVTCLB1a