Читать книгу Interventional Cardiology - Группа авторов - Страница 254

Current intravascular imaging approaches such as OCT or IVUS are inable to assess specific biologic processes in the coronary arteries in vivo. Molecular imaging is a relatively new field that aims to image specific molecules and cells involved in the pathogenesis of vascular disease, including macrophages, endothelial cell adhesion molecules, fibrin, and coagulation factor XIII activity [136,137]. Molecular imaging requires injectable targeted imaging agents that bind a specific molecular or internalized within a cell. These agents can then be detected by an appropriate hardware imaging system, including positron‐emission tomography (PET), magnetic resonance imaging (MRI), single‐photon emission tomography (SPECT), ultrasound and, more recently, fluorescence imaging systems.

While PET and MRI molecular imaging approaches appear promising for large arterial beds (e.g. carotids, peripheral arteries), the smaller size of the coronary arteries dictates an intravascular‐based imaging approach to achieve sufficient sensitivity and resolution. To meet this need, optical‐based imaging using near‐infrared fluorescence (NIRF) has evolved to serve as a promising coronary artery‐targeted intravascular imaging platform. The NIR window (650–900 nm) is advantageous for fluorescence imaging as this window exhibits reduced blood absorption and scattering, and reduced background tissue autofluorescence, which serves to increase the ability to detect NIRF molecular imaging agents in vivo.

In the last decade, several intravascular NIRF systems have been engineered, including a one‐dimensional wire spectroscopic‐based system, a standalone two‐dimensional imaging system, and most recently, a combined NIRF‐OCT imaging system [138,139].(Figure 9.9). Several preclinical investigations have provided the first clinical‐type demonstrations of imaging inflammatory protease activity and endothelial leakage in atheroma [138–142], fibrin deposition and inflammation on stents[143,144], and imaging the plaque response to paclitaxel drug‐coated balloons [145]. Imaging occurred in vivo in human coronary‐sized arteries of rabbits and pigs, suggesting the potential for clinical translation. The most recent NIRF‐OCT system has the further advantage of providing simultaneous anatomic information that is precisely co‐registered with NIRF molecular information, which further allows quantitative NIRF imaging (Figure 9.8). Similarly to NIRF‐OCT, a NIRF‐IVUS catheter has been developed and is undergoing clinical translation [146].

Figure 9.9 Intravascular near‐infrared fluorescence molecular imaging of plaque inflammation integrated with exactly co‐registered OCT. A dual‐modal near‐infrared fluorescence (NIRF) OCT catheter was evaluated in inflammatory atherosclerosis in the rabbit aorta, a vessel of similar caliber to the human coronary artery. Twenty‐four hours after an intravenous injection of Prosense VM110, a NIRF molecular imaging agent that reports on cathepsin protease activity in atheroma, in vivo intravascular NIRF‐OCT was performed. NIRF revealed augmented protease activity in OCT‐defined atheroma, with substantial inflammation heterogeneity seen across atheroma (a,d). The OCT catheter is seen in the middle of the image; the NIRF signal intensity (representing quantitative protease inflammatory activity) is represented by a color scale bar mapped on to the luminal border. The NIRF‐OCT findings were confirmed by histology (H&E, middle column b and e), and cathepsin B immunohistochemistry (right column, c and f).

Source: Yoo et al. 2011 [135]. Reproduced with permission of Nature Publishing Group.