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Medical Imaging

A host of medical imaging techniques employ nuclear radiation.

What makes nuclear radiation so useful?

First, gamma radiation can easily penetrate tissue; hence, it is a useful probe to monitor conditions inside the body.

Second, nuclear radiation depends on the nuclide and not on the chemical compound it is in, so that a radioactive nuclide can be put into a compound designed for specific purposes.

The compound is said to be tagged. A tagged compound used for medical purposes is called a radiopharmaceutical. Radiation detectors external to the body can determine the location and concentration of a radiopharmaceutical to yield medically useful information.

Biological Effects of Ionizing Radiation

All the effects of ionizing radiation on biological tissue can be understood by knowing that ionizing radiation affects molecules within cells, particularly DNA molecules.

A cell with a damaged ability to repair DNA, which could have been induced by ionizing radiation, can do one of the following:

• The cell can go into an irreversible state of dormancy, known as senescence.
• The cell can commit suicide, known as programmed cell death.
• The cell can go into unregulated cell division leading to tumors and cancers.