Abstract
Purpose The majority of X-ray contrast agents (XCA) are made with iodine, but iodine-based XCA (I-XCA) exhibit low contrast in high kVp X-rays due to iodine's low atomic number (Z = 53) and K-edge (33.1 keV). While rhenium is a transition metal with a high atomic number (Z = 75) and K-edge (71.7 keV), the utilization of rhenium-based XCA (Re-XCA) in X-ray imaging techniques has not been studied in depth. Our study had two objectives: (1) to compare both the image quality and the absorbed dose of I- and Re-XCA and (2) to prepare and image a rhenium-doped scaffold. Procedures. I- and Re-XCA were prepared and imaged from 50 to 120 kVp by Micro-computed tomography (µCT) and digital radiography and from 120 to 220 kVp by planar X-ray imaging. The scans were repeated using 0.1 to 1.6 mm thick copper filters to harden the X-ray beam. A rhenium-doped scaffold was prepared via electrospinning, used to coat catheters, and imaged at 90 kVp by µCT. Results I-XCA have a greater contrast-to-noise ratio (CNR) at 50 and 80 kVp, but Re-XCA have a greater CNR at >120 kVp. The difference in CNR is increased as the thickness of the copper filters is increased. For instance, the percent CNR improvement of rhenium over iodine is 14.2% with a 0.6 mm thick copper filter, but it is 59.1% with a 1.6 mm thick copper filter, as shown at 120 kVp by µCT. Upon coating them with a rhenium-doped scaffold, the catheters became radiopaque. Conclusions Using Monte Carlo simulations, we showed that it is possible to reduce the absorbed dose of high kVp X-rays while allowing the acquisition of high-quality images. Furthermore, radiopaque catheters have the potential of enhancing the contrast during catheterizations and helping physicians to place catheters inside patients more rapidly and precisely.
Highlights
X-ray imaging techniques require the administration of X-ray contrast agents (XCA) to enhance the contrast between fluid, tissue, and/or anatomical structures. e majority of XCA are solutions of iodinated compounds, which are administered to patients via intravenous or intra-arterial injections before radiographic examinations [1]. e evolution in the structure of iodine-based XCA (I-XCA) moved from inorganic iodine to organic mono, di, and tri-iodinated compounds; from lipophilic to hydrophilic compounds; from ionic to nonionic compounds; and more recently, from monomers to dimers
I-XCA have been linked to several adverse effects with an estimated incidence between 1% and 12% [7]. ese adverse effects may range from mild reactions, such as itching and emesis, to life-threatening emergencies, such as hypersensitivity reactions, thyroid dysfunction, anaphylaxis, and nephropathy [8,9,10]
Large doses of I-XCA are administered to patients during catheterizations because the majority of catheters are radiolucent. e incorporation of a rheniumdoped scaffold onto the surface of the catheters has the potential of making them radiopaque, providing a visual guide for physicians during catheterizations and potentially reducing the use of I-XCA
Summary
X-ray imaging techniques require the administration of X-ray contrast agents (XCA) to enhance the contrast between fluid, tissue, and/or anatomical structures. e majority of XCA are solutions of iodinated compounds, which are administered to patients via intravenous or intra-arterial injections before radiographic examinations [1]. e evolution in the structure of iodine-based XCA (I-XCA) moved from inorganic iodine ( sodium iodide, or NaI) to organic mono-, di-, and tri-iodinated compounds; from lipophilic to hydrophilic compounds; from ionic to nonionic compounds; and more recently, from monomers to dimers. Due to its low atomic number (Z 53), iodine attenuates high kVp X-rays ( > 80 kVp) to a lesser degree than other high-Z elements. For this reason, images typically exhibit low contrast and high noise [12, 13]. E utilization of rhenium in X-ray imaging has only been reported in a few manuscripts by Krasilnikova et al [37,38,39,40] despite its high atomic number (Z 75) and low cost compared with gold (1,300 USD per kg of rhenium vs 44,800 USD per kg of gold) [41]. A specific application of the use of rhenium in X-ray imaging was studied by coating catheters with a rheniumdoped scaffold. Large doses of I-XCA are administered to patients during catheterizations because the majority of catheters are radiolucent. e incorporation of a rheniumdoped scaffold onto the surface of the catheters has the potential of making them radiopaque, providing a visual guide for physicians during catheterizations and potentially reducing the use of I-XCA
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