Radium in Human Bone: The Dose in Microscopic Volumes of Bone

Abstract

The terminal Ra226 concentrations found in bone samples from individuals who carried radium 20 or more years were measured by the technique of quantitative alpha-track autoradiography. In the diffuse distribution found throughout all of the compact bone a relatively uniform radium concentration exists. The average magnitude of this activity is about 0.5 of the hypothetical uniform distribution, i.e., the body burden divided by the bone mass. The specific activities in the "hot spots" are, on the average, 90 times as great as the diffuse activities. These measured distributions have also been expressed as terminal dose rates. The calculated doses range, in an individual with a terminal burden of 10 [mu]c, from 33 rads/day in hot spots and 0.40 rads/day in the diffuse distribution, down to values of 1.1 rads/day and 0.06 rads/day, respectively, in a case where the burden was 1.2 uc terminally. It is postulated that the radium concentrations within bone slowly diminish in intensity as a result of a long term exchange process which continually exchanges bone calcium for plasma calcium, and that the magnitude of this loss of activity is apparently described by an exponential function with a half-life of about 8 years.