Nasopharyngeal brachytherapy for lymphoid hyperplasia: review of dosimetry

Nasopharyngeal implants of radium sources were used in the 1940s and 1950s to treat children with otitis media and military personnel who had aerotitis media. Individuals received one or more treatments, typically for a total of 30 to 50 milligram-hours (mgh). Documentation of treatment parameters, including source strength and treatment times, allows estimation of organ doses in these patients. For example, for 40 mgh, radiation-absorbed doses to adjacent organs in an adult are estimated as follows: brain, 3; pituitary gland, 16; salivary glands, 8.5; and thyroid gland, 1.4 cGy. For a child 6 years of age, the doses for 40 mgh are: brain, 4; pituitary gland, 27; salivary glands, 11; and thyroid gland, 3.1 cGy. beta-Particles, in addition to gamma-rays, produce a high dose within a few millimeters of the source, but beyond 10 mm the dose is due to gamma-rays alone.