Characteristics of an accelerator based system for in vivo aluminium measurement in peripheral bone

In healthy individuals, renal clearance maintains tissue and plasma concentrations of aluminium at very low levels. Elevated levels are found in patients on renal dialysis, with dialysis solutions (dialysate) containing trace levels of AL; a further risk results from an associated long term use of AL-based phosphate binders. Amongst dialysis patients AL has been implicated as the causative agent of encephalopathy, osteomalacia, osteodystrophy, anaemia and general malaise. There is no easy, non-invasive, method of investigating AL overload measurements of AL concentration in plasma give only an estimate of recent exposure, while estimates of long term exposure can be derived from analysis of iliac crest biopsy samples which are obtained by a painful procedure, not suitable for serial measurements. The favourable neutron cross-section and energy of the gamma emission of the reaction 27AL(n,gamma) 28AL enables the technique of in-vivo neutron activation analysis to be contemplated for detecting AL. Previous studies have been undertaken at East Kilbride2 using 14 MeV neutrons, at Brookhaven3 using a reactor-based source, and at Swansea4 using a 252Cf source, with emphasis being on the measurement of either total body AL or in the bone of the hand. in all those systems a particular problem concerned the interfering 31P(n,gamma) 28AL reaction. The 252Cf system additionally suffered from a problem of low thermal neutron production and consequently of low usable dose-rate. in contrast, the University of Birmingham Dynamitron accelerator is capable of producing an intense source of fast neutrons from the reaction 3 H(p,n)3 He with a neutron energy that is lower than the threshold (2 MeV) for 31(P)(n,gamma)28 AL. 3 figs, 1 tab