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Microanalysis of Bone

Trace elements are found naturally in the environment. Human exposure derives from a variety of sources. While some trace elements are important to human health, others are toxic, such a lead (Pb), which causes numerous diseases.

Lead in predominantly accumulated in the skeleton, where 95% of the total Pb burden is stored. The estimated half life of Pb in bone is up to 20 years.

The use of X-Rays or synchrotron radiation in combination with a confocal microscopic X-Ray fluorescence (µ-XRF) setup provides an ideal instrumentation to determine the distribution of Pb and other trace elements like zink (Zn) or strontium (Sr) in bone and of course calcium (Ca), which represents about 20 weight percent of bone.

(a) Backscattered Electron (BE) image of a slice from human patella. Articular cartilage (I), the TM (II), calcified cartilage (III), suchondral bone (IV) and cement lines (V) can be clearly identified. (b) Element maps obtained from confocal micro-XRF at HASYLAB BL-L.

As can be seen in the picture the Pb distribution is not homogeneous. There is a specific accumulation of Pb in the so called tidemark, the transition zone between calcified and non-calcified articular cartilage.

Low (a) and high (b) magnification BE images of a bone sample (c) coloured slice of histological investigation

One aim of the microscopic analysis of human bone is to find out how the distribution of the trace elements as well as the major elements changes in case of certain degenerative bone diseases like osteoarthritis (OA) and osteoporosis (OP). Furthermore there is hope to get more insight into the role of trace elements in bio-mineralization processes.

The measurements are mainly carried out at µ-XRF beamlines at synchrotron facilities in Hamburg (DESY) and Karlsruhe (ANKA).

The table top setup installed at our laboratory, which is currently operating in a non confocal geometry, with a polycapillary focusing optics between X-Ray tube and sample, will be extended to a confocal geometry by installing a polycapillary half lens in front of the detector very soon.

The experiments involving human bone samples are carried out in cooperation with the Ludwig Boltzmann Institute of Osteologie, which provides us with appropriate samples and offers the biomedical expertise when interpreting the data of the microscopic analysis.