Background: Within the context of developing techniques to facilitate the diagnosis of the thyroid diseases, the elemental composition of pathological thyroid tissue (neoplastic and non-neoplastic) was investigated by proton induced X-ray emission. The PIXE has been widely used as a sensitive technique for trace elemental analysis in both biological and medical fields.

Materials and Methods: The twenty-eight specimen of thyroid tissue (neoplastic, non-neoplastic and grossly normal tissue) were obtained from operation of 14 patients with different thyroid diseases. Determination of the heavy trace elements distribution (Fe, Co, Ni, Cu, Zn, As, Se, Br, Rb, Mo, I) was carried out by irradiating of the sample surface with a focused proton beam.

Results: Fourteen grossly normal, eleven non-neoplastic and three malignant thyroid neoplasm cases were diagnosed. Trace element contents of the International Atomic Energy Agency (IAEA) MA-B-3/TM Fish tissue was used as standard for calibration of PIXE set up.

Conclusion: The concentration of the heavy trace elements Co, Cu, Zn and Mo in neoplasm of thyroid were higher than other samples. The concentration of the heavy trace elements, Fe, As, Br, Rb, I, are found to be much lower in neoplasm of thyroid than non–malignant and grossly normal thyroid tissue. The concentration of the Se, Co and I in this study is consistent with the others study but there are differences in the concentration of Fe in our study and others works. Iodine concentrations was 11 times lower, on average in neoplasm compared with non-neoplasmic tissue of thyroid. The low levels of I in thyroid neoplasm are correlated to some pathological factors. Iran . J. Radiat. Res., 2004 1(4): 211-216