PET Scans

In my last post, I touched on PET scans and may have made it sound like I preferred them over CT scans. There is some preference, and with today's technology, yes, I really would.

Let me start by explaining PET.

PET stands for Positron Emission Tomography (by the way, CT stands for Computed Tomography), and in my cancer assessment both were used together. According to http://www.petscaninfo.com/:

A PET scan demonstrates the biological function of the body before anatomical changes take place, while the CT scan provides information about the body's anatomy such as size, shape and location. By combining these two scanning technologies, a PET/CT scan enables physicians to more accurately diagnose and identify cancer, heart disease and brain disorders.

I began receiving PET scans in December of 2004, after I completed chemotherapy. The prep for the scan was similar to a CT scan, only slightly different. I was given 2 bottles of Barium to drink prior to the scan, and had a CT when I got to the doctor's office. New Mexico Oncology had their own radiology department, so I did not have to go to the hospital for the scan. Once the CT was finished, which ususally took about 5 minutes (with the PET scan, the CT did not need contrast, or the iodine injection). I was then taken to a small room with a recliner, and given the radioactive glucose injection. Petscaninfo.com gives a good explaination for the injection:

The most common form of a PET scan begins with an injection of a glucose-based radiopharmaceutical (FDG), which travels through the body, eventually collecting in the organs and tissues targeted for examination. The patient lies flat on a bed/table that moves incrementally through the PET scanner. The scanner has cameras that detect the gamma rays emitted from the patient, and turns those into electrical signals, which are processed by a computer to generate the medical images. The bed/table moves a few inches again, and the process is repeated.  

This produces the digital images, which are assembled by the computer into a 3-D image of the patient's body. If an area is cancerous, the signals will be stronger there than in surrounding tissue, since more of the radiopharmaceutical (FDG) will be absorbed in those areas.

It takes about 45 minutes for the glucose to move through the blood stream. At this time I would have to relax and not move around. The reason for this is that muscle stimulation could cause the glucose to collect around the muscles, giving a false reading. Also, for this reason, I could not have carbohydrates prior to the scan. The sugars from the carbs would also cause a false reading.

Once the glucose had time to distriubte I was taken into the room with the machine and laid down on a table, similar to a CT scan. The machine however was much smaller, and longer than the CT machine. Kind of reminded me of a hacked up MRI, about 1/4 the length of the tube. As the description from petscaninfo.com says, the bed/table moves a few inches at a time. The machine at NM Oncology took about 2 hours and 15 minutes to complete. The lab tech would put the table all the way through so that the machine started taking pictures of my pelvis and finished with my head. The last 45 minutes of the scan were usually the worst for me, because I am claustrophobic, and the "tube" is not quite wide enough, and my shoulders would be scrunched. The final 20 minutes were generally when I would start to freak out, and I would have to try and calm myself down by counting the minutes. That is a good way to distract yourself. Sometimes I was able to fall asleep, but when my shoulder got pulled in, that mostly woke me up.

 This is similar to the machine used.

In my last post I mentioned that my final PET scan was done at Athens Regional Hospital on a newer machine. That PET scan took less than 30 minutes (for the actual scan) and did not include a seperate CT scan. I was told several times the NM Onocology had purchased a new PET machine, but they did not have the space for it. I know that the building has undergone extensive remodeling since I moved back to Georgia, so I am sure the new machine has been installed, for which I am greatful. Not for me, but for all of the other patients at NM Oncology who need the scans. Cancer is bad enough on its own, without having to suffer through the testing as well.