PSI - Issue 33

Niki Martini et al. / Procedia Structural Integrity 33 (2021) 295–303 Martini/ Structural Integrity Procedia 00 (2021) 000–000

296

2

Keywords: dual energy; X-rays; hydroxyapatite; calcium oxalate; calcium carbonate; minerals; calcium/phosphorus ratio

1. Introduction Kidney and uteric stones presence, accompanied with pain, is increased in the population worldwide (Jendeberg et al. 2017, Saigal et al. 2005, Scales et al. 2014). Stones smaller than 5 mm are expected to pass spontaneously (Coll et al. 2002, Parmar 2004, Sandegard 1956, Simon et al. 2017, Ueno et al.1977) and thus no external assistance is needed. Regardless elective surgery is needed (> 5 mm) or not (Jendeberg et al. 2017), the knowledge of stones’ composition is important for the physicians in order to plan the best treatment for each patient as they tend to reappear after a period of time (Eliahou et al. 2010, Qu et al. 2011). Kidney and uteric stones are most frequently composed of calcium oxalate and hydroxyapatite (Bargagli et al. 2020, Basiri et al. 2012, Chen et al. 2020, Eliahou et al. 2010, Evan et al. 2015, Grant et al. 2018, Keshavarzi et al. 2016, Letavernier et al. 2019, Macfarlane 2015, Primak et al. 2007, Qu et al. 2011, Sethmann et al. 2014, Vásquez-Quitral et al. 2017) and more rarely of calcium carbonate (Daudon et al. 1995, Frochot et al. 2021, Keshavarzi et al. 2016). Based on several studies, the presence of kidney/uteric stones is associated with the presence of atherosclerotic plaques (Alexander et al. 2013, Arafa et al. 2020, Aydin et al. 2011, Devarajan 2018, Ferraro et al. 2013, Huang et al. 2020, Luo et al. 2020). The rapture of the atherosclerotic plaque can lead to severe myocardial infarction (Jia et al. 2013, Yahagi et al. 2015) and stroke incidents (Spagnoli 2004). In the early stages of the atherosclerotic plaques’ formation, the coronary arteries are calcified (Adamson et al. 2015, Chen et al. 2013, Creager et al. 2019, New et al. 2013, O’Brien et al. 1995). The vulnerability of the plaques is associated with the calcifications (Li et al. 2018, Sakaguchi et al. 2016). The calcification minerals most commonly found in atherosclerotic plaques are hydroxyapatite (Becker et al. 2004, Creager et al. 2019, Florea et al. 2021, Li et al. 2018, Perrotta et al. 2017, Shi et al. 2020, Viegas et al. 2019) and calcium oxalate (Creager et al. 2019, Herrmann et al. 2020, Perrotta et al. 2017). Hydroxyapatite is associated with both stable and unstable plaques and calcium oxalate only with stable plaques [57]. Calcium carbonate was also found in atherosclerotic plaques (Creager et al. 2019). Motoyama et al. (Motoyama et al. 2007) defined as “spotty” calcifications those that were smaller than 3 mm in size (Feuchtner et al. 2019, Pflederer et al. 2010, Shi et al. 2020). Spotty calcifications are an indicator of both atherosclerosis’ stage and the progression rate (Kataoka et al. 2012, Stefanadis et al. 2017). Computed Tomography (CT) is the gold standard method for both kidney/uteric stones and atherosclerosis diagnosis; however, the mineral characterization is difficult (Eliahou et al. 2010, Jendeberg et al. 2017, Nishizawa et al. 2018, Qu et al. 2011, Wood et al. 2020). To this aim, Dual Energy Computed Tomography (DECT) has been used as it can achieve the differentiation of the minerals (Ding et al. 2021, Eliahou et al. 2010, Nishizawa et al. 2018, Primak et al. 2007). The characterization of the aforementioned minerals can be an important tool for the physicians to remove the stones and prevent atherosclerotic plaques’ rapture as the structural integrity of each mineral will indicate the proper treatment, surgical or not. The mineral characterization of which breast calcifications, kidney/uteric stones and atherosclerotic plaques’ calcifications are composed was studied in previous works of our team (Martini et al. 2017, Martini et al. 2020, Martini et al. 2021). The dual energy (DE) method our team developed estimated the effective calcium/phosphorus mass ratio ( ⁄ ). The results indicated statistically significant difference between the minerals investigated for breast calcifications of 300 μm thick or higher and kidney/uteric stones and atherosclerotic plaques’ calcifications of 0.7 mm thick or higher. In this study, a dual energy X-ray method was developed to characterize the calcific kidney/uteric stones and atherosclerotic plaques’ calcifications as their composition is related to their structural integrity. Monoenergetic and polyenergetic simulation studies were carried out for calcium oxalate, hydroxyapatite and calcium carbonate calcifications with thicknesses ranging from 0.5 to 3 mm, in order to find the optimized irradiation conditions. In all cases the ⁄ was estimated. The method was validated using an X-ray tube combined with a high resolution complementary metal-oxide-semiconductor (CMOS) active pixel sensor (APS) detector. Based on the experimental results, for both kidney stones and atherosclerotic plaques, statistically significant difference was observed between the different types of minerals for thicknesses of 0.7 mm or higher.