Energy-dispersive X-ray fluorescence analysis of iodine in thyroid puncture biopsy specimens

Zaichick, V. Y.; Zaichick, S. V.

A device for EDXRF was developed to determine the iodine content of large-needle biopsy specimens of human thyroid nodules. The device includes a 25 mm2 Si(Li) detector, a multichannel analyser and eight sources of the radionuclide 241Am with a total activity of 7.4 GBq. Necropsy (4 subjects) and resected (8 subjects) thyroids were used to evaluate the representativity of specimens weighing 10 to 15 mg which were obtained by means of a large titanium needle. Moreover 7 women with thyroid nodules were subjected to large-needle biopsy prior to being operated. The iodine content of these specimens was measured and they were also used for routine histologic study. The iodine contents (referred to the weight of wet tissues) of intact thyroids and of benign and malignant nodules were 1049 +- 755, 241 +- 108, and 35 +- 26 mugcntdotg-1, respectively. The large-needle biopsy specimens were sufficiently representative with regard to iodine analysis for allowing a differential diagnostics of the benign and malignant nodules. Our present method allows the estimation of iodine concentrations in fresh specimens of large-needle biopsies and in samples of lyophilised and homogenised tissues. The detection limit of iodine is approximately 3 mugcntdotg-1 for 30 min measurements of 10-15 mg specimens of fresh tissues and 10 min measurements of 40-60 mg specimens of homogenised dry tissues.