Proton microprobe for analysis of normal and osteoporosis-affected compact bone. 2. Low-Z elements

While μPIXE of normal and osteoporosis-affected bones was suitable for metals from Ca on (abstract 1 from our group, this volume), it fails to detect low-Z elements. Some of them may be involved in osteoporosis, e.g. F prevents demineralization and N occurs in bone proteins. Here we examined the potential of μPIGE, μPBS and μPIXE to study low-Z elements in the outer surface layer of rat and human bones with osteoporosis. The bone sections were as described (abstract 1), and the μPIGE, μPBS and μPIXE measurements were performed at the Rossendorf nuclear microprobe with 3.1 MeV protons focused to ~3 μm, using concomitantly three detectors.
μPIGE was useful to detect light elements like F, P, Na, S- the concentrations of these elements can be calculated by comparing the characteristic X- ray lines of suitable standards. CaF2, NaCl, pyrite and hydroxylapatite (HA) were used as reference materials. PBS provided information about C, N, O, F, Mg, P and Ca, mainly qualitative at this stage.
Further development would allow N and S analysis, which may help evaluate the bone collagen, supposedly altered in osteoporosis. Only P, S, Cl and Ca were monitored here by PIXE and the concentrations of these elements were calculated by GUPIX. In all bones, a P/Ca ratio of 0.32-0.39 was found, below the 0.46 value of HA, suggesting a fraction of Ca as carbonate in addition to HA. Both P and S concentrations showed variability from bone to bone. The μPIXE maps of P were positively corelated to the Ca maps, evidencing well- ressolved patterns.
Thus the information yielded by μPIGE and μPBS on the light elements from osteoporosis-affected bones was potentially quantitative, complementary to μPIXE, and pathologically relevant, and the three methods complement each other in understanding this bone disease.