Radioactive isotopes in the treatment of malignant disease and diseases of the thyroid gland.
نویسنده
چکیده
It is difficult to get a balanced picture of any new form of treatment, and much more difficult when new modes of diagnosis and therapy extend into the realms of atomic physics. In this article an attempt will be made to describe the present position of radioactive isotopes as applied' to surgery. Without going deeply into the physics of the subject, the author will present the principles underlying their use. Radioactive elements behave chemically and biologically exactly like their stable isotopes. Radioactive iodine, to take an example, will be metabolized by the thyroid gland along with ordinary iodine without any discrimination on the part of the tissues. But the radioactive atoms are at constant risk of atomic disintegration or rearrangements releasing energy in the form of gamma rays and energetic particles. Each material emits its own characteristic radiation and decays at an equally characteristic rate, and the radioactivity differs widely from one substance to a:iother. The gamma radiations may be soft or hard X-rays according to the energy released. The energetic particles are usually beta rays which are fast-moving electrons, or alpha rays which are fast-moving helium atoms. In any event, there is ionizing energy emitted which has a biological effect on tissues and is capable of detection by &jitable equipment. The gamma rays are of particular value for measurement as they penetrate the body and can be measured externally. The beta rays will only penetrate a few millimeters, the penetration being proportional to the energy reXeased. Consequently, the beta radiation may orly be measured by ordinary methods when es. itted on the surface or on the skin, and it requires a special type of ' probe counter ' for interstitial measurement. Good examples of different radioactivities are provided by radioactive iodine and radioactive phosphorus. Radioactive iodine (13,) gives off beta and gamma radiations. Its presence can be measured quantitatively by virtue of the gamma radiation, but its clinical and biological effect is mainly due to beta radiation. By means of a ' directional counter' the concentration in the body can be mapped out quite accurately, and the modern ' scintillation counter' is so sensitive that only minute and quite harmless quantities are required for this. Furthermore, these concentrations can be mapped out and the contours of the thyroid gland can be plotted in different planes with sufficient accuracy to determine the gland volume within reasonable limits of error. This is of particular importance in the treatment of thyroid diseases by radio-iodine. Radioactive phosphorus (P32) gives off beta radiation and no detectable gamma rays. Consequently, its detection and measurement in the tissues, e.g. in a tumour of the brain, cannot be estimated by external counters. It can, however, be measured by a' probe counter ' pushed into its substance. Its concentration in the blood or in body fluids can be measured by taking appropriate samples.
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عنوان ژورنال:
- Postgraduate medical journal
دوره 29 336 شماره
صفحات -
تاریخ انتشار 1953