Microprobe studies of inorganic deposits in the aortic wall

The chemical composition and crystalline nature of inorganic deposits present in the human aortic wall were investigated. A proton microprobe in combination with proton induced X-ray emission and proton induced gamma-ray emission were used to determine quantitatively the elemental composition of the inorganic deposits while their structure was studied with the use of an X-ray microprobe in combination with X-ray diffraction and Fourier transform infrared microscopy. It was found that deposits in the aortic wall are composed of Ca-P compounds. Fluorine is accumulated in the inorganic phase. However, the mechanism of F deposition awaits further investigations. The only phase detected by the X-ray diffraction was a defective hydroxyapatite. The relative intensities of reflexes indicate that the c axis of the crystallites is parallel to the long axis of the vessel. IR microscopy revealed that the crystals were contaminated with carbonate groups. Moreover, the band characteristic for octacalcium phosphate was detected.