Noninvasive measurement of aluminium in human bone: Preliminary human study and improved system performance

Aluminium has been measured in the hands of 18 referent subjects and six aluminium welders using the technique of in vivo neutron activation analysis. The minimal detection limit (MDL) in the human subjects was 28.0 microgAl/gCa, whereas it was 19.5 microgAl/gCa in calibration standards. On average the aluminium exposed subjects had higher levels of aluminium in their hands than did the referent subjects. However, this difference only just achieved significance at the 5% level and should be treated with caution, since the study had not been deliberately designed to assess this difference. Following the preliminary human study, improvements were made to the measurement system with respect to the gamma-ray detector array and to the timing sequence of irradiation-transfer-counting. These improvements were tested on the calibration standards, lowering the MDL from 19.5 microgAl/gCa to 8.32 microgAl/gCa. A similar improvement in human measurements would result in an in vivo MDL of 12.0 microgAl/gCa.