THE DEVELOPMENT OF A TECHNIQUE TO MEASURE BONE ALUMINUM CONTENT USINGNEUTRON-ACTIVATION ANALYSIS

The accumulation and toxicity of aluminium in patients with chronic re nal 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 te chnique of in vivo neutron activation analysis, using a thermal neutro n beam from a reactor, has been employed by previous workers, who meas ured Al in the hand with a detection limit of 0.4 mg for a dose equiva lent of 20 mSv. However, the application of this technique is restrict ed by the very limited availability of nuclear reactors. We report the modification of an existing Cf-252-based instrument and construction of a shielded, high-efficiency counting system for the in vivo measure ment of Al in the hand. Phantoms containing tissue-equivalent solution s of Ca, P, Na and Cl with various Al loadings were used for validatio n of the technique. The Al/Ca ratio in the hands of seven patients wit h renal failure was measured using a cyclic activation technique to co mpensate for the relatively low neutron output of the Cf-252 source, a nd a detection limit of approximately 2.2 mg Al was achieved for a dos e equivalent of 36 mSv. The results were compared with the Al content of iliac crest bone biopsy specimens measured using electrothermal ato mic absorption spectrophotometry.