Background: The method of proton induced X-ray emission (PIXE) has been widely used as a sensitive technique to trace elemental analysis in both biological and medical fields. The sensitivity of this powerful method is in the order of ppm .The aim of this work is to analyze structural composition of 4 heavy trace elements with Z greater than 24 (Mn, Fe, Cu, Zn) in two kinds of gallstones and to compare the results for various ages of patients by PIXE quantitatively.

Materials and methods: The pigment and cholesterole gallstones were obtained from 12 patients during surgical operations and were used for in vitro study. The age of the patients were between 22 and 78 years. Both cholesterol and pigmented types were analyzed for shell and center. The samples were bombarded using a 3.0 MeV van-de-Graff accelerator at nuclear research center of Atomic Energy Organization of Iran for the PIXE measurement.

Results: In pigment gallstones, the mean value of Mn, Fe, and Zn in shell is greater than in the center and Cu in the shell is smaller than center. In cholesterol gallstones, neither in the shell nor in center, Zn was not observed. The composition of Mn and Fe in center is greater than in shell. In the patients older than 40 years, the concentration of heavy trace elements increases, and those in cholesterol stones are nearly two times larger than in pigment stones.