Keeping an invisible enemy at bay

IT is inevitable in today's high technology diagnostic testing that ionising radiation (X-rays or gamma radiation) is often required to help the doctors make a diagnosis. Exposure to ionising radiation can be divided into two broad categories of tests.

The first involves X-rays where part of the body is exposed to a dose of radiation at the point of diagnostic testing, and there is no residual radiation after the X-ray images have been taken. Such tests include routine X-rays, mammograms and computed tomography (CT) scans.

The second category involves the injection of radioactive isotopes into the blood stream and detecting their distribution in the body using a detector. In this case, the entire body will be exposed to radiation as the isotopes circulate in the blood stream. And the radiation remains as long as the isotopes remain in the body. Such tests include sestamibi scan, thallium scan, and rubidium positron emission tomography (PET) scan - all of the heart. Sometimes, the patient is exposed to both types of radiation sources, for example, when undergoing a whole body PET-CT which is usually used for cancer studies.