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Question on Pet Scans

herdizziness's picture
Posts: 3642
Joined: Apr 2010

Okay, so I had my Pet Scan today, they told me they were doing this to see my tumors better.
My last scan was a CT Scan in August, where they said they could barely see the tumors in my liver, etc., except for my colon and that had shrunk too.
Today, after my pet scan I'm in the gyn cancer oncologist's office to make sure I don't have all the female cancers. Checked out good there, BUT, he showed me the Pet Scan taken earlier in the day, and showed me only one tumor could now be seen and that one was in my colon, he was really surprised the liver tumor's didn't show up.
So does the Pet Scan show the cancer tumor's better then the CT scan? I've never had the Pet before and don't understand it.
Winter Marie

Sundanceh's picture
Posts: 4408
Joined: Jun 2009

Hi Winter

CT scans are better able to pick up and see masses of cells - they see physical structure more clearly.

PET scans show if the mass the CT detected is "lit up" or showing glucose uptake to those spots. If they are, then there could be an indication of cancerous activity - maybe and maybe not. PETs have not been completely reliable for me. The CT has accurate picked up most of my tumors.

However, the oncs use the CT and the PET combined, to draw an educated guess or opinion at what they are seeing.

And I've also had scans where the CT said one thing - and the PET scan said another.

It's maddening, it's confusing, and sometimes it's hard for us to draw a conclusion.

PETS can show false as well due to infections or other anomalies.

It will be interesting to see what the scan results reveal - then we'll know some more.


Lori-S's picture
Posts: 1286
Joined: Sep 2010

As Craig said, very well ... they try to use them together to get a better picture as they show different things. It's a little frustrating when they don't line up together and it sort of keeps you guessing. Also, you have to account for time and treatment between the PET and the CT. Since the PET shows uptake (activity) perhaps the liver tumor just isn't active enough to register ... that would be a good thing.

Good news from the gyn onc. Congratulations on that!

Posts: 372
Joined: Aug 2006

Craig is right but there are some problems as I found out. I had a reoccurrence as it turns out back in March 2010. My CEA had gone from 1.4 to 5.6 so Onc ordered a CT/Pet scan. It came back clear. Of course it wasn't clear there was a 2cm tumor in my asending colon. Now I would like to believe that it was as my ONC says "it didn't show up because your tumor at that time was encased in the colon and you have the luck or bad luck to have a low grade (non-agressive) tumor that won't show up well on CT/Pet Scans because of the rate of glucose absorbtion is very low in a low grade tumor". This is strange since when I had rectal cancer low grade it lite up like a Christmas Tree four years ago. However it could also be that the stupid machine and its tech and the hospitals needed to make some bucks did the scan when they knew it wasn't working to standards. You see after injecting me with the radioactive glucose they delayed me well beyond the 90 minutes because they were having techical difficulties with the machine. Or maybe the radiologist couldn't read a scan...who knows? Three months later my CEA was at 14.6. My personal doctor not my ONC ordered a colonoscopy. Good thing because by now the tumor had grown through the wall of my colon and into three nodes. So I am up in the air? They won't do another Pet/CT scan until after 8 treatments of Folfox. I'm hopeful that my ONC explaination is the right one even though they "missed" my colon tumor if the machine was working in March the rest of me would still be clear. Of course there is the nawing feeling that maybe the doctors have circled the old medical wagons on another screw up but again who knows? The good thing about your scans are that they also know where to look and judge based on prior information. It sometimes hard for us to accept good news isn't it? Your news looks great. hugs Lou

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