PET/CT: Where is your cancer, exactly?


Doesn’t it make sense to know for sure where the cancer is in your body before you have surgery or begin to treat it?

We think so and that’s why we strongly recommend PET/CT scans for our patients.

PET/CT technology is considered complementary and even superior to other imaging modalities because it shows biological activity within organs and can therefore detect cancer in the earliest stages.

PET/CT can differentiate between normal and tumor cells in your body and can indicate the stage and aggressiveness of your cancer. In other words, not only does the PET/CT show you where the cancer is in your body it also shows you how aggressive it is and can therefore be used to identify primary tumour sites (where the cancer originated) which is very helpful data for treatment.

With PET/CT, patients are injected with a radioactive glucose solution (approximately the same amount of radiation that you might experience with a standard X-Ray). Since cancer cells utilize glucose for their rapid growth, they quickly uptake a significant amount of the solution and glow when imaged, thus we can identify the exact size and location of tumours anywhere in your body.

PET-CT scans are used for many types of cancer and are shown to be more accurate in diagnosing cancer than PET scans alone.  In brief PET-CT scans can help to:

  •  Diagnose cancer
  •  Indicate the stage of a cancer
  •  Make decisions about whether you can have surgery to remove your cancer
  •  Make decisions about which is the best treatment for your cancer
  •  Show how well the treatment is working
  •  Find the place in the body where you cancer first started to grow (primary cancer)
  •  Check whether your cancer has come back
  •  Show the difference between scar tissue and active cancer tissue

After you have had treatment for cancer, a basic CT or MRI scan may show that there are still some signs of the cancer left. But this may not be active cancer. It could be scar tissue left over from cancer killed off by your treatment. A PET-CT scan can show whether this tissue is active cancer or not so you do not worry or continue treatment unnecessarily.

The scientific data exists to show how beneficial a diagnostic tool Pet/CT is. In fact, in the United States there are over 2700 PET/CT machines. In Canada we have 33 PET-CT machines, with half of those in Quebec.

A 2010 study in the Journal of Nuclear Medicine which explored the benefits of PET/CT over other imaging technologies concluded “The clinical use of PET has been specifically demonstrated to be cost-effective for staging of non–small cell lung cancer, differential diagnosis of solitary pulmonary nodules, restaging of Hodgkin disease and non-Hodgkin lymphoma, and restaging of colorectal carcinoma. From a health economic point of view, the use of functional PET in clinical routine seems justified.”* (note – This article looked specifically at just a few forms of cancer but PET/CT has proven to be equally as beneficial with all forms of cancer.)

Despite the mounting evidence for PET/CT as a powerful tool for cancer diagnosis and for observing the outcome of cancer treatment, at present, the standard cancer diagnosis process in Canada typically still begins with an Ultrasound which we find sad and somewhat frightening given how clearly beneficial PET/CT scans are and the following data on Ultrasound Tests in general:

According to the American Cancer Society: Concerns With Ultrasound : Ultrasound images are not as detailed as those from CT or MRI scans. Ultrasound cannot tell a benign (not cancer) tumor from one that is cancer.

Its use is also limited in some parts of the body because the sound waves cannot go through air (such as in the lungs) or through bone.

They go on to say: The quality of the results depends to a large extent on the skill of the technologist or doctor operating the transducer, which is not the case with CT or MRI (and is not at all the case with Pet/CT as the images the PET/CT scan provides truly speak for themselves).

Another common scan, which you may have already experienced is the CT scan.

CT scans provide a little more detail than an ultrasound but still, as the images below indicate, they do not always find the cancer in your body, and again, can often lead to a false negative which means that you miss out on early treatment options that can make a huge difference to the success of your cancer treatment.

For example, in the image below, the patient was told that based on the CT scan, they were cancer free. When the patient opted to get a private PET-CT scan, they identified a tumor that would have otherwise gone untreated,



And here is another image of a CT scan which shows some questionable masses but does not indicate that they are in fact cancerous. This lack of confirmation can, and often does, impact how quickly you get access to the treatment you need and, with cancer, where time is of the essence, waiting is not a good idea.

CT SCAN                                                                                                       PET-CT SCAN

CTOAM CT scan versus PET CT


MRI (Magnetic Resonance Imaging) uses magnetism and radio waves to build up a picture of the inside of the body. It can provide more detail than a CT scan and has been shown to be more effective than CT scan at exploring certain tissues in the body.

MRI, as with CT, looks at variations in density of tissues. Essentially exploring shapes and shadows, leaving technologists to make a best guess as to which shapes are cancerous or not. Neither MRI and CT scans can confidently tell the difference between malignant tumours and benign, nor can they differentiate between cancerous tissue and cysts or fibroids.

With PET/CT you just know if you’re seeing cancer or not. You know where it is and you know, by how it is glowing, how prolific that particular tumour site is.

If you think you may have cancer or have been told that you are free of cancer based on any other imaging modality, we urge you to get a PET-CT scan.

The images speak for themselves. 

Contact us today to ask more questions about PET/CT or to arrange for a PET/CT scan yourself, contact Premier Diagnostic Centre.

*(Quote from: Economic Evaluation of PET and PET/CT in Oncology: Evidence and Methodologic Approaches J Nucl Med Technol. 2010 Mar;38(1):6-17. doi: 10.2967/jnmt.108.059584)