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Pet or CT???

Mrs. Sarge
Posts: 206
Joined: Apr 2012

Just wondering what the difference is between a PET or a CT w/contrast? I've always had a CT with contrast and never had a PET. My CA was vocal cord and seems like most of you are BOT so wonder which is the more comprehensive or why the difference, if anyone knows??
Should I ask for a PET scan?

Posts: 660
Joined: Mar 2012

I just wanted you to know I Googled CT vs Pet Scan, it brings up a lot of good fyi. Hope that may help, Im sure smarter folks than I will also offer there thoughts, have a good night.

blackswampboy's picture
Posts: 341
Joined: Jul 2012

a big difference is the cost: PET scans are way more $$$.

PET scans are full-body (from legs up, anyway), and give metabolic info on cellular function--such as how much sugar your organs are using. PET scans are handy for evaluating possible spread of cancer, and showing blood flow and organ function.
CT scans give more detailed pics of anatomical structures (such as bone). PET scans show the tracer--the structures, not so much.

that's my [limited] understanding, anyway.

ToBeGolden's picture
Posts: 695
Joined: Aug 2010

For a PET, you get injected with radioactive glucose. (You are on a protein and fat diet for a day. No sugar. No carbohydrates. Hardest part of the test. And nothing but water for the last 12 hours. Of course get the instructions from you healthcare professionals and follow them). Cancer cells are hungrier than normal cells so they eat more of the radioactive glucose.

However: The brain is very active and hungry. So PETs are not good at finding tumors in the brain. Also, and most importantly, inflammation are also "hot" like from infections and arthritis. Often the patient may not know he/she has an infection. This is why a positive PET clears up in three months.

As a patient, I think the thing to ask the healthcare professional: What will be done with a positive PET, or with two consecutive positive PETs. If the answer is we'll watch it until the tumor gets large enough to cause problems: then Why PET. If the answer is that we will surgically remove it: PET. If the answer is we will know where to biopsy: PET.

In my case: I may have met lung cancer (identified by a post-treatment 8 month PET). However, even if they confirm the tumor with a second PET, no treatment is planned until the tumor is much bigger. Why. It's incurrable (but treatable) But chemo will be worse than the early disease. (I will be getting second opinions.) Nevertheless, I'm in no rush for the followup PET.

I'm hoping I'm clear. Of course I could be clear but totally wrong.

A CT is like a super X-Ray. A computer virtually slices the body up so the caregiver can walk thru you body looking at structures.

hlrowe's picture
Posts: 47
Joined: Oct 2012

Easy way to remember

CT = structural
PET = metabolic

My Med onc, rad onc, and ENT overlaid both images to get a complete assessment.

Posts: 1914
Joined: May 2012

Hey there !
I agree with all the other answers. A pet is a great diagnostic for checking on spread. But knowing what is going on in your body...healthwise is a big plus. Alot of us have had a couple of scares with this test only to find out it was arthritis...infections...ect. But if the doctors are looking for specific mets, then this is a good one. I will continue to repeat that any PET should be followed up with CT, or MRI for confirmation. And then if needed a biopsy. And continue to ask your specialist if these tests are absolutely necessary ! Our confidence in our medical proffessionals is a must...and if they say yes, follow their advice. Katie

Mrs. Sarge
Posts: 206
Joined: Apr 2012

Thanks for all the comments. Guess my ENT and Radonc just like the CT with contrast because that's all I've had. Guess if they order a Pet scan I might be scared as they'll probably be looking for mets, tho they've told me if there's a recurrence it most probably will be on the vocal cords again...that's scary too, but don't know what I can do about it all, anyway! I am so educated by all the posters on this board, I thank you much!

LeoS2323's picture
Posts: 156
Joined: Mar 2012

Hey Mrs Sarge - hope you are doing well!

Have a few more things to add to the comments already made from what I have learned during my process. Firstly it's worth bearing in mind that although PET is a fantastic tool, to image your abdomen and pelvic area on a full body scan requires a fairly large dose of radiation.

Of course there are no guarantees, but generally HNC needs to develop in the head and neck area and through the nodes in the neck before it spreads. If your cancer was caught in good time and it hasn't developed too much in its original site or the nodes then there is very little chance of spread, therefore no real need of that dose of radiation from the PET scan.

Also PET is not infallible - as has already been said, there can be false negatives and positives. My case is a great example - I had a 4cm lump in my neck (most of it wasn't tumor but a bit was) that barely reacted at all to PET but turned out to be cancerous. False negative.

I had also had some acid reflux (don't get it anymore, think it was partly stress related back then) and my PET reacted around my oesophagus - the activity was my body repairing the damage. False positive - and I had to have a camera down my throat to biopsy it which was really horrible!

My doctors are giving me MRI scans going forward which is similar to CT, avoiding any more PET radiation. I think if your guys feel CT is enough then that's a good thing. It's worth talking to them about the various options though to ensure the reasoning is sound and to keep yourself informed.

Don't feel that PET is the be all and end all though - it is a fantastic tool for checking spread but has drawbacks as well.

All the best


Mrs. Sarge
Posts: 206
Joined: Apr 2012

Yes, I'm doing well. Going for my 2nd scope the 16th. My first CT was clear! I know i'll feel a little more secure after the 16th! Thanks for the info on the PET.
Best to you too!

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