Hi I'm 20 months out NED. My onc. is leaving it up to me whether I can get a PET vs a CT scan. Any ideas. I'm leaning toward PET as the whole body is shown.


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When was the last time you had a PET scan? They are nuclear lol. In any case they won't show the brain, but they will otherwise give a pretty comprehensive look of most of the body. I guess it would depend on the answer to the question plus which CT scans were ordered.

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Hi Lisa,

Get a pet scan. I had been in remission for 3 months. My onc sent me in for a ct scan for my 3 month checkup. A few very small spots were showing up and he could not tell if it was scar tissue ete or what.

He sent me in for a pet scan and bingo the spots lit up. The cancer had come back. In the pet scans the cancer will light up. Thank God we caught them when they were extremely small. I am back on chemo.

So I will always have a pet scan for my checkups.


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The PET scan shows what is going on at the cellular level (cancer cells eating up the sugar). A small injection of a radioactive sugar is given to the patient. If there would be signs of cancer, the sugar travels thru the body and gets "gobbled up" by cancer cells. Cancer cells metabolize the sugar and trap it. Since the sugar is radioactive, it gives off energies that can be captured and turned into a picture. While this is very informative, the integrated PET/CT gives much more information to the physician.

It works like this: When the patient lies down to be scanned, a whole body CT scan is done on the patient, which shows exemplary anatomic detail. The patient is then moved a little further into the tube to get the PET scan performed. Since these two tests are integrated into one machine, the technician can overlay the physiologic data (PET) with the anatomic data (CT) which will tell the patients physician exactly where the tumor is, and how they can plan their therapy to kill it. A PET/CT scan takes on average 20 minutes, while the more antiquated PET or software fused PET takes in excess of one hour, and is nowhere near as informative to the physician.

Most insurances (including Medicare) pay for PET/CT scans because they change the patient management up to 40% of the time, and may help avoid unnecessary and costly surgery. A plain PET scan or a PET scan that uses software fusion is not as accurate as an integrated PET/CT. It could make a world of difference.

In regards to the accuracy of the procedure, the Cat scan uses a special barrage of X-rays to see through tissue while the Pet scan can detect the kinds of metabolic changes associated with tumor growth. In other words, it can overlay the metabolic data of the Pet and the detailed anatomic data of the CT to pinpoint the location and stage of tumors.

While CT does an excellent job of depicting structures and anatomy, it may miss small or early stage tumor. Because Pet monitors the biochemical functioning of cells, with a high degree of sensitivity, by detecting how they process glucose (cancer cells metabolize glucose at a much higher level than normal tissues), it can identify cancerous cells even at an early stage when other modalities (CT) may miss them.

As you see, each scan has it's own remarkable abilities, but because a patient may not be positioned identically for both scans (separately), the two images can be difficult to line up exactly, degrading the accuracy of the diagnostic information. The combined PET/CT allows physicians to rapidly both scans in one session without having to move the patient.

Once a patient has been injected with a radioactive isotope, the scan allows doctors to measure to within half a billionth of a second the time difference in the detection of two gamma rays coming from the isotope. That allows for more accurate identification of the site of a lesion and a better image of any possible tumor.

The PET/CT can check for early indications of cancer or to see if the cancer has spread. It can also look to see if a particular therapy has been successful in treating a cancer. Possible indications of whether chemotherapy benefits cancer patients can be provided, but the big problem is that the patient is given potentially toxic and ineffective drugs and need to wait and then make tumor measurements.

A note of caution. If the PET/CT is used to screen for cancer/recurrence and increased activity is found, this may lead to undue anxiety and further unnecessary evaluations and procedures that could be harmful to the patient. Some benign processes, including several types of infectious lesions can simulate cancer with this test. For this reason, a biopsy may be required to confirm a diagnosis.

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Dear gpawleski,
Thank you for the information, your post are always so informative.
Do all places that have a PET scan, have a PET/CT ?

It does sound like the best of both worlds....


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Hi Lisa:

There is such a scan as a PET/CT scan, the best of both worlds. They use the same radioactive glucose as the PET, but I have learned that this scan is more in depth than just a Pet or a CT scan by themselves. I have had 5 of these scans so far and am due for another on October 21st. It can't hurt to ask.
Love to all,

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Mt mom has had CT scans, a PET scan, and a CT/PET scan.


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Hi, I already forced my lovely PCP to give me a brain MRI 2 months ago(I'm very pushy). So think everything is alright in my brain. Don't know about the PET/CT Scan. I'm in the sticks in Santa Barbara, but will find out if they have one. L.A. is close enough if need be. Sounds like a winner to me. Last time I had a PET Scan was last December.

MaryLou Oct. 21st is my bday! I think you'll have good news!! :-))


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I use to get PET/Ct Scan all the time, but now I just have the CT scan w/contrast. If something drastically changes in the CT the doctor would do the PET scan but PET scans can give you a false positive at times. That is why I have always had the PET/CT scan together. Good luck.

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HI, Betsy:

Just curious who the radiologist is can you forward me the number. Funny, I'm from's not Monica Lewinsky's(of Bill Clinton fame) father is it?

Lisa Raphael

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Depends on your cancer. I am stage IV BAC, diagnosed via wedge biopsy in March 2009. In further staging, nothing showed up as 'hot" (cancerous) on my PET scan, which is not uncommon for this variety of the disease. The CT scans, however, revealed multiple tumors and densities.

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Hi Lisa

You get what ever you want!!!! You are going to be around a really lonnnnnngggggggg time....maybe we can all make some art work with our scans.....

Love you

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Dear Janet:

Where are you thought you were visiting in September??


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I get a PET/CT, my onc says it shows the bones better.

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You want both the CT/PET scan, I believe. One does not replace the other--they show different things. And, yes, the PET scan may give rise to a false positive--infectious process, and even exercise can increase metabolic activity in a non-cancerous lesion.

You have a clinical relationship with one of the best thoracic oncs. in the country (Gandara), so why not ask him to weigh in.


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