3D Objects, Engineering

X-Ray Tomography (Part A)

X-Ray Computed Tomography is a technique constantly used in medical imaging. You might have heard about CT Scans… Sounds very Sciencey, Medical, and Technical. Because, it is. The CT in CT Scans is short for Computed Tomography. CT Scans can also have non-medical application. For example, seeing what is inside of non-living things, like 3D printed objects—my topic of interest in this instance.

Why am I explaining something I had previously mentioned in a post (kind of)?

Because this is a filler post!

No, it’s not a filler, but I wanted to explain how exactly I did the Tomographic scans of the 3 D printed objects for the Optimization of 3D Prints project, before completing its story through more posts.

The CT Scanner used during the whole process of analyzing the 3D objects was Skyscan 1172 Micro-CT Scanner. Before beginning a scan, safety precautions must be taken, everything should be kept clean, the scanner must be hooked to a computer with powerful graphics card, relevant software must be installed, and this is very important—the power must be turned On. Of course, the machine is designed with all the safety measures taken into consideration. In fact, the X-ray source won’t work if the compartment (look at the image below) is open, even if it is told to start the operation by the software. But still, the most important thing to keep in mind is that the machine is a powerful source of X-Rays, so safety first!

Now we are ready to place the object of interest (which we usually call, a specimen) on one of the many pedestal-types (they are also called stages for some reason, as if the camera is taking the photos of some super model) for the specimen to be scanned, which in this case would be all the different types of printed objects of different infill. The specimen was covered in a paraffin sheet to keep it in place. Paraffin sheet is used because it is transparent to the X-Rays (i.e., the X-Rays ignore it, like a person ignores their ex). These initial settings are a bit convoluted, but they must be performed to capture good quality images without the formation of unnecessary rings in the final images (for now, take my word for it, I know what I’m saying when it come to this). The Skyscan1172 software helps in doing all of these initial operations such as adjusting the voltage and power levels, adjusting the pixel size of the images to be captured, the field of view, position of the object, and other relevant parameters can be adjusted with the software.

Inside the CT Scanner

I don’t want to make this post boring with even more technical details, so in a layman’s example, the setup can be seen (in the image above) for a cylinder inside the compartment of the CT scanner. Behind the cylinder is the camera/sensor, and on the left side (the open square box), is the X-Ray source. More on the technical aspects another day. (Because I want to try and explain some of the details about why this process is complicated and takes time, and the analysis of the data obtained from this takes even more time).

Once the images are captured, certain settings need to be adjusted and images must form the whole picture in the end for analysis: size of the image to be captured, position of the camera, etc. This and more can be done in a software meant to be used with the CT scanner called NRecon. The software shows a captured image. As an example, the image (see below), shows the frustum of a cone when observed by the sensor at a particular angle.

The turn-table-pedestal-stage-thing will rotate the specimen as the stationary sensor captures sectional images, while all along, the source showers the specimen with X-Ray beams. These images are reconstructed using NRecon, where the HSI levels, contrast and other adjustments need to be made before reconstruction of captured image for analysis. 1000 images each were captured for a variety of infill levels and objects of different shapes in my project (Honestly, this number is nothing. You should see the Biology researchers have a go at it for the real deal). The image below shows a snapshot of some of the settings chosen, which was kept constant for all the different objects.

A Snapshot of NRecon in Use

In Part B, I’ll get to the real stuff: the Process of Everything!


P.S.: You guessed it right, this post was supposed to come out a week ago, and it did! However, due to unforeseen circumstances, I couldn’t finish writing it. Unfortunately, the draft was scheduled to be published back then. Even what’s written in this article is incomplete, which is obvious from the Part A in the title. I need more time to finish Part B. Who knows, there might even be a Part C, Part D… Party! We’ll see… Woe is me…

 

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