Methods have been developed to investigate the quantitative production and the ultimate fate of <tex-math>${}^{37}{\rm Ar}$</tex-math> produced in bone calcium in the living human body. A healthy male subject's whole body was irradiated using cyclotron-produced neutrons provided by the <tex-math>${}^{9}{\rm Be}({}^{3}{\rm He},{\rm n})$</tex-math> reaction. The dose of fast neutrons was limited to 1.6 mrad. Six breath samples were collected and assayed for <tex-math>${}^{37}{\rm Ar}$</tex-math> content over a 12.5 hr period after irradiation. Low background (0.5-5 counts/day) gas proportional counting techniques were used to assay samples containing as little activity as 0.01 dis/min corrected to end of irradiation. Analysis of the exhalation data by a two-component exponential relation indicated 82% of the activity left the body by way of the lungs with a half-time of 40 min. The remaining 18% was exhaled with a 200 min half-time. Exhalation was demonstrated to account for approximately 70% of the <tex-math>${}^{37}{\rm Ar}$</tex-math> activity produced in the body. Evidence from studies of isolated bone indicated that essentially permanent trapping in bone crystals accounted for the remaining activity.

This content is only available as a PDF.
You do not currently have access to this content.