What is a PET scan?:
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.
Why do we need PET scans?:
CT scans and MR scans can give us excellent photographs of different parts of the body, and identify enlarged nodes or tumor masses. 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. And a PET scan is the answer.
How are PET scans useful in lymphomas?:
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.
How are PET scans done?:
PET scans are more or less similar to other scans like CT. You will need to eat 4-6 hours before the scan time, and not do any strenuous physical activity before the scan. A small amount of radioactive material (small enough to be essentially harmless), is injected an hour beore th scan is done. The scan itself will last about an hour, and you will have to lie as still as possible during this time. You can listen to music on a CD player to help you relax. When the scan is over, you can leave within a short period of time.
What is FDG?:
FDG is Fluoro-deoxy glucose, a special form of radioactive glucose that is used for PET scans. Tumor tissue uses glucose faster and in a different way that normal tissues. FDG accumulates within tumor cells. That is how a PET scan is able to tell the difference between normal and tumor cells.
Is doing a PET scan essential for lymphomas?:
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.
How frequently should PET scans be done during follow-up?:
PET scans need not be done repeatedly as a follow-up test. Most hospitals use CT scans for routine follow-up, and use PET scnning when they need some extra help. There are no general rules for the frequency of PET scans. You should speak to your doctor regarding your hospital policy.
Are there any side-effects of PET scans?:
PET scans are essentially harmless for the patient. There is little risk of complications. The amount of radioactivity in the injection is low, only about as much as an X-ray.
