The feasibility of a sensitive low-dose method for the in vivo evaluation of Fe in skin using K-shell x-ray fluorescence (XRF).
An x-ray fluorescence (XRF) system designed for monitoring of skin Fe concentrations has been performance tested for use on patients treated for beta-thalassaemia. The essentials of the system are: a collimated x-ray tube operated at 20 kV and 20 mA; energy selection of the x-ray beam by means of a Cu K-edge filter; use of skin phantoms containing concentrations of Fe in the range 10 to 100 parts per million (ppm); and a high-purity germanium detector placed at 90 degrees to the incident beam. For a Cu K-edge filter of 0.15 mm thickness a quasi-monoenergetic beam of approximately 8.4 keV is obtained which is close to the absorption edge of Fe (7.11 keV). For a real-time counting period of 400s the systemis capable of detecting Fe concentrations of 15+/-2 ppm at a skin dose of the order of 5 mSv. This level of Fe is at the higher end of the normal range found in the skin. In using the same system and operating parameters, measurements on a sample of ferritin obtained from a rat's liver yield an Fe concentration of 36+/-3 ppm for a measurement time of 500 s; this can be compared with suppliers' data indicating an Fe level of 36 ppm.
Farquharson
M J
MJ
Department of Radiography, City University, London, UK.
Bradley
D A
DA
D000818:Animals; D005293:Ferritins / Q000032:analysis; D006801:Humans; D007501:Iron / Q000032:analysis*; D008099:Liver / Q000378:metabolism; D011859:Radiography; D051381:Rats; D012867:Skin / Q000000981:diagnostic imaging* / Q000378:metabolism*; D013052:Spectrometry, X-Ray Emission / Q000295:instrumentation* / Q000379:methods*; D017086:beta-Thalassemia / Q000175:diagnosis
D005293:Ferritins; D007501:Iron