What is a CT Scanner? Are you sure this isn’t a Time Machine?

Well, CT stands for Computed Tomography.  The machine is basically a traditional X-ray machine that spins around the patient so that it can acquire many different images of the body.  A computer algorithm converts the images into layered scans to allow radiologists to sift through them looking for tumors, internal bleeds, pneumonia, and a range of other conditions. The final images look something like this.

CT scans are one of the most frequently ordered diagnostic tests in emergency departments in the United States (many say they are ordered way too much), so it’s important to know a little bit about how they work… And unfortunately, no, it is not a time machine.

Here is a labeled image to give you a bit more detail into how it works:

1: X-ray tube

2: High voltage power source and transformer

3: Scintillation detectors with 5 cooling fans

4: Fluid pump and radiator for cooling the X-ray tube

All of these components make 2 to 3 complete turns per second around the patient.

So how does the CT Scanner stay electrically powered while spinning?

To keep the machine charged without tangling the cords, CT scanners rely on the technology of the Slip Ring:

A Slip Ring is basically an electromechanical device that allows the transmission of power and electrical signals from a stationary to a rotating structure, in this case, from the base to the rotating scanner.  One difference between the image below and the slip rings of CT Scanners is that there is a pool of liquid metal molecularly bonded to the contacts instead of the sliding brush. This decreases friction even more to allow constant rotation of the scanner.

 

Hopefully you found this interesting and at least somewhat easy to understand. For further reading, head here.

-RSB