Mineral Characterization in Human Body: A Dual Energy Approach

Kidney and uteric stones are a common cause of pain and disturbance in numerous people worldwide, as they tend to reappear. There are several studies investigating the association of urolithiasis and nephrolithiasis with atherosclerosis, as patients suffering from the former diseases were found to have been diagnosed with atherosclerotic plaques. Hydroxyapatite and calcium oxalate are the most common mineral crystals found in both kidney/uteric stones and atherosclerotic plaques’ calcifications. Even though for stones smaller than 5 mm surgery is not recommended, the knowledge of the stone composition is an important tool for the physician in order to provide better treatment for the patient. The mineral crystal characterization of atherosclerotic plaques’ calcifications smaller than 3 mm (spotty calcifications) will assist the physician to limit the possibility of myocardial infraction and stroke, as the presence of hydroxyapatite indicates possible plaque rapture. To this aim, a dual energy (DE) X-ray method was developed in this work. The calcium/phosphorus mass ratio ($m_{Ca}/m_P$) was determined through analytical simulations and the results were verified experimentally. Both monoenergetic and polyenergetic simulation studies were implemented for hydroxyapatite, calcium carbonate and calcium oxalate with thicknesses ranging from 0.50 to 3.00 mm, at 100 μm increments, to obtain the optimized irradiation conditions. The experimental verification of the proposed method was performed using an X-ray tube combined with a high resolution complementary metal-oxide-semiconductor (CMOS) active pixel sensor (APS) detector. The Mann–Whitney U test indicated that statistically significant differences were found between the different types of minerals examined for thicknesses of 0.70 mm or higher.