PET Scan

My mother is scheduled to have a PET scan tomorrow.

What the hell is a PET scan?

I work on an application that is designed to be used by imaging techs at hospitals. When I was in training many years ago they gave us a really nice overview of how the imaging department in an average hospital works, including the different types of machines that are used. PET scans were one of the things we covered. As I said though, that was years ago and the topic has only come up once for me since then and that was unrelated to work. That was in 2006 or 2007 I think, and it was just hearing that some one was about to have one.

(I should probably add for the record that Mass General is not using the application that I work on.)

Here's the wikipedia article on PET scans.

I think the deal is they inject a radioactive agent into the blood stream that will be metabolized by whatever area they want to look at. In this case that must be the tumor itself. The machine then builds a 3D image that not only allows you to see the affected area, but allows you to watch it work on the radioactive agent.

Here is a snippet of the wiki article:

Applications...
Oncology: PET scanning with the tracer fluorine-18 (F-18) fluorodeoxyglucose (FDG), called FDG-PET, is widely used in clinical oncology. This tracer is a glucose analog that is taken up by glucose-using cells and phosphorylated by hexokinase (whose mitochondrial form is greatly elevated in rapidly growing malignant tumours). A typical dose of FDG used in an oncological scan is 200-400 MBq for an adult human. Because the oxygen atom which is replaced by F-18 to generate FDG is required for the next step in glucose metabolism in all cells, no further reactions occur in FDG. Furthermore, most tissues (with the notable exception of liver and kidneys) cannot remove the phosphate added by hexokinase. This means that FDG is trapped in any cell which takes it up, until it decays, since phosphorylated sugars, due to their ionic charge, cannot exit from the cell. This results in intense radiolabeling of tissues with high glucose uptake, such as the brain, the liver, and most cancers. As a result, FDG-PET can be used for diagnosis, staging, and monitoring treatment of cancers, particularly in Hodgkin's lymphoma, non-Hodgkin lymphoma, and lung cancer. Many other types of solid tumors will be found to be very highly labeled on a case-by-case basis—a fact which becomes especially useful in searching for tumor metastasis, or for recurrence after a known highly active primary tumor is removed. Because individual PET scans are more expensive than "conventional" imaging with computed tomography (CT) and magnetic resonance imaging (MRI), expansion of FDG-PET in cost-constrained health services will depend on proper health technology assessment; this problem is a difficult one because structural and functional imaging often cannot be directly compared, as they provide different information. Oncology scans using FDG make up over 90% of all PET scans in current practice.

I wonder then, are they using this to see if the cancer has spread? I guessed that that was part of the reason they did the lumbar puncture last week. I figured if there were cancerous cells in the spinal fluid then it probably meant that the cancer was spreading. That was just a layman's guess though, I really had no idea if that was true or not. Same with this. I have no idea exactly what they will be looking at when run this on my mother tomorrow. I really don't care either, I just want them to come back with good news. The best news being that the first dose of chemo she expects to have today kicks the living shit out of the tumor. That would be good news.