We’ve all heard the abbreviations: CAT, PET, MRI, fMRI, SPECT.
Now what the heck do they all mean?
Brain imaging has an interesting start. But generally, brain imaging techniques fall into two broad categories: Structural imaging, and Functional imaging. Structural imaging does just what its name implies: it provides images of the structure of the brain. There’s no indication of blood flow or brain metabolism here; just bone and tissue. Structural images are based on the idea that different bodily tissues have different densities and different physical properties. Structural images provide static, one-shot images of the brain’s structure. They say nothing of function.
Functional imaging also does what its name implies: it images the brain as it functions. Dyes, radioactive tracers, are all used in these imaging modalities to image the brain’s blood flow and metabolism. These images are dynamic, showing changes in brain function over a period of time.
The next few articles in my blog will feature one of the imaging techniques in an article. We’ll start off with CAT scans.
CAT stands for Computerized Axial Tomography. CAT scans are also abbreviated CT scans, for Computerized Tomography. CT scans are possible because different tissues have different X-ray absorptions. How much a tissue absorbs X-rays is related to that tissue’s density. So, bone absorbs the most X-rays, cerebrospinal fluid (CSF) absorbs the least. That’s why on CT scans, bone appears white and the ventricles, which contain CSF, appear black.
There’s a slight danger with CT scans, because the person being imaged is exposed to a slight amount of radiation.
CT scan image can be found here: http://vectorblog.org/wp-content/uploads/2011/06/Head_CT_scan.jpg