The university hospital in our town has nuclear imaging to diagnose problems. They have suggested doing a nuclear (PET) scan of our 11-year old son. He has back pain from an unknown cause. I’m concerned about the exposure to radiation. What can you tell me about this?

Nuclear medicine using positron-emission tomography or PET scan does involve the injection of a radioactive dye that can be traced using a special camera. The dye is injected into the blood stream using an intravenous (IV) line. It then moves through the blood vessels throughout the body.

Each tracer has its own affinity for tissues. For example some are more likely to attach to areas of bone and can be used to look at the spine. Any increased area of cell growth or tissue repair will usually mean increased concentration of the tracer.

Fractures or other injuries to the bone show up as a hot-spot seen easily on the image. This represents a place where there is an increase or build-up of the dye.

Nuclear scanning is non-invasive, but it does involve exposure to ionizing radiation. And exposure to radiation does have the potential to cause problems. Damage to the DNA and the possibility of cancer are the major concerns.

However, based on studies to date, the radiation doses delivered to a patient in this type of imaging have a very small chance of causing cancer. The total dose of radiation is small — more than a chest x-ray but less than a CT scan of the chest. The difference is that the dose using nuclear imaging with a PET scan is delivered internally rather than externally from the X-ray.