Medical applications elemental analysis

The Promochem Group was the first international specialist supplier of certified reference materials (CRMs) and pharmaceutical reference substances used in environmental, medical and trace element analysis. Their experience provides a viewpoint that echoes, reinforces and expands on many of the trends discussed above (Jenks 1997). From the middle of the 1980 s, sales of CRM by Promochem increased between 10 % and 20 % annually, depending on the market sector and application. Since then National and International Metrology Institutes, such as the now privatized U.K. Laboratory of the Government Chemist (LGC), the European and U.S. Pharmacopoeias, the E.U. IRMM and others have recognized that efficient distribution of RMs, backed by available technical support, is as important as production and certification. Thus, they have moved to spread their influence outside their national origins. The Web and e-commerce will continue to grow as major facilitators of better information dissemination and supply of CRMs. 

In spite of the excellent capability and advantages (high selectivity and sensitivity) of RIMS for the ultratrace analysis of isotopes with naturally rare abundance in environmental, geological, medical and nuclear samples, no commercial instrumentation is available to date. In contrast to AMS and RIMS as mono-elemental (element-specific) analytical techniques, ICP-MS and LA-ICP-MS possess, in analogy to GDMS and SIMS, have the ability for multi-element analysis and thus could have the widest fields of application. 

XRF is not a new method since the first measurements of stable iodine in the thyroid by Hoffer et al. (1968), the use of XRF has spread to include several other elements in medical apphcations, as well as applications in occupational and environmental surveillance. Today, XRF is primarily used as a nondestructive method for investigation of metals, minerals, environmental samples, food constituents, and body fluids. Examples of in vivo XRF elemental analysis are measurements of lead in bone (Ahlgren and Mattsson, 1979 Somervaille et al., 1985 Todd and Chettle, 1994) and studies on cadmium, mercury, gold, and platinum (Ahlgren and Mattsson, 1981 Borjesson et al, 1993, 1995), but the method is not, to our knowledge, used clinically as a tool in the routine assessment of thyroid function. Some in vivo applications of the method are listed in Table 3.1. 

PIXE is the preferred method for such applications as the analysis of 15 to 20 elements in a thin sample such as air filters, or for automated analysis of large numbers of geological or archaeological samples, due to its short measurement time. The low absolute detection limit and good sensitivity for elements such as S, P, Cl, K and Ca, Fe make PIXE of great importance in biological and medical applications. 

Figure 11.9 (a) Nucleus 24 contour cochlear implant electrode array (Reprinted with permission from Synthetic Metals, Actuators for the cochlear implant by Zhou, D., Wallace, G.G., Spinks, G.M. et al., 135-136, 39-40. Copyright (2003) Elsevier), (b) A diagram showing a standard nucleus electrode array inserted around the spiral of the first turn of the cochlea to stimulate the auditory nerve fibres 137] (Reprinted with permission from Medical Engineering Physics, Evaluation of trajectories and contact pressures for the straight nucleus cochlear implant electrode array- a two-dimensional application of finite element analysis by Chen, B.K., Clark, G.M. and Jones, R., 25, 2, 141-7. Copyright (2003) Elsevier). 

Chen, B.K., Clark, G.M., Jones, R. (2003) Evaluation of trajectories and contact pressures for the straight nucleus cochlear implant electrode array—a two-dimensional application of finite element analysis. Medical Eng. Phys, IS 141-7. 

Overview. Microbeam experiments are carried out if the structure iu a small volume element of the sample is to be studied. Compared to macrobeam applications, the advantage of this method is the possibility to study spatial variations of nanostructure. An example of a matching scientific question is the analysis of the core-shell structure of polymer fibers, or the study of nanostructure variations in nanostructured gradient materials which are developed for medical applications. All the corresponding experiments are carried out in a scanning microbeam setup . 

It is obvious that the sample preparation technique used influences the detection limits. Table 1 shows this influence on various samples from different fields of application. Table 2 gives an overview of applications of TXRF already analysed. Figure 3 shows a spectrum of a water standard reference sample (NIST 1643c) obtained with a TXRF vacuum chamber, constructed at Atominstitut, Vienna. Generally, an excellent field of application of TXRF in trace element analysis can be seen in liquid samples. All kinds of liquids, ranging from different kinds of water to acids and oils, as well as body fluids, can be analysed. Environmental samples, like airborne particles, plant material or medical and biological samples such as tissue can be analysed directly on a reflector. 

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