MiWord of the Day Is… PET scan!


Peanuts. What a great story. The most popular and influential comic strip in history. Snoopy was my first stuffed animal growing up. He still lives with my parents. So what is a PET scan anyway? I don’t recall ever seeing the picture above in any of the Peanuts cartoon strips.

Positron emission tomography (PET) is somewhat of a special medical imaging modality in that it brings together two different technologies from different times. Let me explain. Back in the early 1930s, George Hevesy was a young Hungarian physicist who developed biologically safe and useful radioactive tracers that could be ingested or incorporated into the body in some way.  Physicians would then manually locate where these radioactive tracers had gone in the body by using a Geiger counter at first and then later using special cameras (Kuhl‘s photoscan) to produce a crude emission image. 

So, how do we get cool pictures like these ones?  Well we would have to wait another 25 years after the development of radioactive tracers by Hevesy for the start of construction of instruments able to not only detect these radioactive sources in the body but to produce tomographic pictures.

It won’t be until the mid 1970s that PET – as we know it today – would be born. Essentially, a patient receives a emissions scan (PET) and a CT (we talked about that here) or MRI (we talked about that here) scan at the same time. The two scans are then merged together thanks to highly specialized computers (see the pictures in the middle frames). Voila! PET. 

PET is both a medical and research tool. Most often used in clinical oncology (medical imaging of tumors and the search for metastases), it is also important in clinical diagnosis of certain diffuse brain diseases such Alzheimer’s disease and other types of dementia.

Relax your brain a little listening to Radioactive by Imagine Dragons and don’t forget the fun part (see the rules here), using PET scan in a sentence by the end of the day:

Serious: Hey Bob, did you know that much of the success of the PET scan is due to the development of the radiopharmaceutical FDG (deoxyglucose) that lead the way to the characterization of Parkinson’s and Huntington’s disease?

Less serious: I can’t believe they developed yet another PET scan. Wasn’t the CAT scan enough?

See you in the blogosphere,

Pascal Tyrrell


MiWord of the Day Is… CAT scan!

A what scan? I am actually a cat guy myself. Not to say I don’t love dogs but if I had to make a choice…

I just finished reading a fantastic book by David Dosa entitled “Making Rounds With Oscar”. The premise of the book is a story about an extraordinary cat but the subject matter is very serious –  dementia and end-of-life care in the elderly. Have a gander.

So what the heck is a cat scan and what does it have to do with medical imaging? 

CT scans – also referred to as computerized axial tomography (CAT) – are special X-ray tests that produce cross-sectional images of the body using X-rays and a computer. CT was developed independently by a British engineer named Sir Godfrey Hounsfield and Dr. Alan Cormack and were jointly awarded the Nobel Prize in 1979. Yes, more Nobel prize winners…

In a nutshell, x-ray computed tomography:

– uses data from several X-ray images of structures inside the body and converts them into 3D pictures – especially useful for soft tissues.

– emits a series of narrow beams through the human body, producing more detail than standard single beam X-rays.

– is able to distinguish tissues inside a solid organ. A CT scan is able to illustrate organ tear and organ injury quickly and so is often used for accident victims.

– is analyzed by radiologists.

Unfortunately, unlike MRI scans, a CT scan uses X-rays and therefore are a source of ionizing radiation.

Now for the fun part (see the rules here), using CAT Scan in a sentence by the end of the day:

Serious: Hey Bob, did you know that the recorded image of a CAT Scan is called a tomogram? 

Less serious: My GP suggested that howling at the moon at night is not normal behavior and he wants to send me for a CAT scan. What? No way, I’m allergic to cats…

OK, listen to Cat Stevens to decompress and I’ll see you in the blogosphere…

Pascal Tyrrell