Measuring Fluorine in Human Bone Using In vivo Neutron Activation Analysis (IVNAA)

Abstract

The subject of whether fluorine (F) is detrimental to human health has been controversial for many years. Much of the discussion focusses on the known benefits and known detriments to dental care and problems that fluorine causes in bone structure at high doses. It is therefore desirable to have the means to monitor fluorine concentrations in the human body as a means to directly assess exposure. A monitoring tool could be applied in studies of human health and perhaps answer some of the questions regarding levels at which fluorine has protective effects and negative health consequences. This thesis presents work in the further development of a low risk non-invasive method for the monitoring of fluorine in human bone. The work was based on the technique of neutron activation analysis (NAA). Fluorine accumulates in bone as a long term storage site following exposure. In this thesis, the McMaster Tandem accelerator was used to produce neutrons through the 7Li(p,n)7Be reaction, measuring F levels in the human hand bone using IVNAA. The gamma rays emitted through the 19F(n,γ )20F reaction are measured using nine NaI(Tl) detectors with 4π geometry. Four published papers are presented in this thesis. The main outcome of the first publication was the development of a new phantom. This was needed to reduce the aluminum contamination. The main outcome of the second publication was a series of improvements to the method for the in vivo measurement of bone fluorine using NAA of the new phantoms. In the third publication the best hand position and neutron flux map in the irradiation cavity were determined through both Monte Carlo simulation (FLUKA) and experimental methods. Finally, the fourth publication describes the utility of the improved technique in a pilot study of environmentally exposed people. The overall conclusion from this thesis work is that a low risk monitoring tool, based on an NAA technique, has been developed which is capable of monitoring fluorine in urban Canadians. The technique can now be applied in studies of human health.