Your treatment is over and you visit your oncologist for a checkup. He examines you and finds no disease left. He orders a CT scan - and there in one corner lies a small lymph node that turns your joy into fear. Is there some lymphoma left in my body?

It is not uncommon to find a few lymph nodes left behind when a CT scan is done after completing treatment. CT scans show up nodes that are larger than usual and calls them abnormal. Very often, these nodes may not have disease at all. Till a few years back there was no really good way to find out for sure.

Now PET scans have an answer. PET scans are similar to CT scans, but show up areas of the body where disease activity is taking place. Since cancer cells grow faster than the normal cells of the body, they light up on a PET scan. This is very useful, because it can tell you that even though some lymph nodes are enlarged, they don't have any disease left. (See PET Scans for Assessment of Treatment Response).

A PET-CT machine goes a step further. In a single machine it has both PET and CT scanners. The 2 sets of scans than then be accurately overlaid on each other and compared. It makes it easy to pinpoint whether a suspicious area on the CT has active lymphoma or not. Because of its advantages, a PET-CT scan may become the best scan to do for assessing response to lymphoma treatment.