A Phantom-Based Study of X-Ray Fluorescence Detectability of Iron, Copper, Zinc, and Selenium in the Human Blood of Superficial and Cutaneous Vasculature

Blood concentrations of essential trace elements can be used to diagnose conditions and diseases associated with excess or deficiency of these elements. Inductively coupled plasma mass spectrometry (ICP-MS) has been employed for such measurements, but maintenance and operation costs are high. XRF detectability in cutaneous blood of iron (Fe), copper (Cu), zinc (Zn), and selenium (Se) was assessed as alternative to ICP-MS. Three phantoms were made up of two polyoxymethylene (POM) plastic cylindrical cups of 0.6-mm and 1.0-mm thick walls and a 5.3-mm diameter POM cylindrical insert. Six water solutions of Fe in 0 to 500 mg/L and Cu, Zn, and Se in 0 to 50 mg/L concentrations, were poured into the phantoms to simulate x-ray attenuation of skin. Measurements using an integrated x-ray tube and polycapillary x-ray lens unit generated 24 calibration lines. Detection limit intervals in mg/L were: (36, 100), (14, 40), (3.7, 10), and (2.1, 3.4) for Fe, Cu, Zn, and Se, respectively. Fe was the only element with detection limits lower than its 480 mg/L median human blood concentration. Estimated radiation dose and equivalent dose to skin were below those of common radiological procedures. Applications will require further instrumental development, and finding a calibration method.