The development of a technique to measure bone aluminium content using neutron activation analysis

The accumulation and toxicity of aluminium in patients with chronic renal failure is a well recognized hazard, and there is a need for a non-invasive technique to assess Al tissue load in these patients. The technique of in vivo neutron activation analysis, using a thermal neutron beam from a reactor, has been employed by previous workers, who measured Al in the hand with a detection limit of 0.4 mg for a dose equivalent of 20 mSv. However, the application of this technique is restricted by the very limited availability of nuclear reactors. We report the modification of an existing 252Cf-based instrument and construction of a shielded, high-efficiency counting system for the in vivo measurement of Al in the hand. Phantoms containing tissue-equivalent solutions of Ca, P, Na and Cl with various Al loadings were used for validation of the technique. The Al/Ca ratio in the hands of seven patients with renal failure was measured using a cyclic activation technique to compensate for the relatively low neutron output of the 252Cf source, and a detection limit of approximately 2.2 mg Al was achieved for a dose equivalent of 36 mSv. The results were compared with the Al content of iliac crest bone biopsy specimens measured using electrothermal atomic absorption spectrophotometry.