Applications of nuclear physics have become an integral part of modern life. From a bone scan that detects a cancer to a radioiodine treatment that cures another, nuclear radiation has many diagnostic and therapeutic applications in medicine. In addition nuclear radiation is used in other useful scanning applications. The fission power reactor and the hope of controlled fusion have made nuclear energy a part of our plans for the future. That said, the destructive potential of nuclear weapons haunts us, as does the possibility of nuclear reactor accidents.
A host of medical imaging techniques employ nuclear radiation. What makes nuclear radiation so useful? First, γ 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. For example, certain drugs are concentrated in inflamed regions of the body, and this information can aid diagnosis and treatment as seen in Figure 32.4. Another application utilizes a radiopharmaceutical which the body sends to bone cells, particularly those that are most active, to detect cancerous tumors or healing points. Images can then be produced of such bone scans. Radioisotopes are also used to determine the functioning of body organs, such as blood flow, heart muscle activity, and iodine uptake in the thyroid gland.
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