Application of X-ray fluorescence to the study of iodine distribution and content in the thyroid

We have been developing an X-ray fluorescence system designed to determine iodine distribution and content in the thyroid. The X-ray fluorescence unit is composed of a 80 kV X-ray excitation beam and a Si(Li) semi-conductor detector. The angle between the X-ray beam and the axis of the detector is 240. Two single channel analyzers (SCA) are used, the first one corresponding to the Kα peak and the other to the background. The SCA signals are digitised so that the two corresponding images may be processed using a computer. After subtracting the background, an image is obtained that represents the iodine distribution alone, and the iodine content of the whole thyroid or a part of it can be determined with a reproducibility of +-5%. A good correlation (r = 0.98) between iodine chemical analysis and iodine fluorescence analysis was obtained for 13 patients. (orig.)