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45 years
For a pet scan after 15 days of treatment for lymphoma.. when it light up for reapparition of 5 lymph nodes could it be false positive ???
Aug 25, 2014

Dr. Rania Mousa General Medicine
PET scans, or Positron Emission Tomography, are a special type of scans. X-rays, CT scans and MR scans take photographs of your body, and identify tumors based on their size, shape and location. But PET scans identify cancers based on the high activity within the cancer cell.

However, sometimes it is difficult to tell whether a lump or mass in the body actually has tumor cells in it only by measuring its size and shape. Small lumps or nodes may contain cancer cells, while larger ones may just be something harmless. That is when you need to measure the activity of the mass a PET scan is used .
PET scans have many uses in lymphomas

They can be used for staging (or mapping the disease in your body)along with other tests like CT scans.
The PET scan report can help decide what kind of treatment is best for you (chemotherapy or radiation).
It can show whether a lump on a CT scan has cancer or not.
It can help in assessing how well you are responding to treatment, when done after a few cycles of chemotherapy.

After treatment is over, PET scans can tell if a lump that still remains has cancer cells or just scar tissue.

The standard form of imaging test in lymphomas is the CT scan. Modern CT scanners have excellent resolution and they can pick up the smallest lymph-nodes. PET scans are used mainly as an additional test for some of the advantages it has. Not all patients need to have PET scans. But they can be very useful in some situations when your CT scans leave some questions unsanswered.

Like any type of diagnostic test, PET scans have limitations such as false positive results.
It is possible to have false results on a PET scan. Blood sugar or insulin levels may affect the test results in people with diabetes.
Most PET scans are now performed along with a CT scan. This combination scan is called a PET/CT
All patients with a positive PET scan are required to have a repeat biopsy to confirm the finding.
Therefore clearly PET is not perfect and false positives are common.
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