Molecular evaluation of thrombosis using X-ray phase contrast imaging with microbubbles targeted to P-selectin in mice.

Abstract

OBJECTIVES: X-ray phase contrast imaging (PCI) provides excellent image contrast by utilizing the phase shift. The introduction of microbubbles into tissues can cause a phase shift to make microbubbles visibly identified on PCI. In this study, we assessed the feasibility of targeted microbubble-based PCI for the detection of thrombosis. METHODS: The absorption and phase contrast images of P-selectin-targeted microbubbles (MBP) were obtained and compared in vitro. MBP, control IgG-targeted microbubbles (MBC), and unbound microbubbles (MBU) were tested for binding specificity on thrombi expressing P-selectin. MBP were used as molecular PCI probes to evaluate P-selectin expression in a mouse model of arteriovenous shunt thrombosis that was created using PE tubes in the bypass outside of the mouse body. RESULTS: PCI clearly showed the microbubbles not viewable via absorption contrast imaging (ACI). In vitro attachment of MBP (91.60&#x2009;&#xb1;&#x2009;11.63) to thrombi was significantly higher than attachment of MBC (17.80&#x2009;&#xb1;&#x2009;4.02, P&#x2009;<&#x2009;0.001) or MBU (9.80&#x2009;&#xb1;&#x2009;2.59, P&#x2009;<&#x2009;0.001). In the mouse model of arteriovenous shunt thrombosis, the binding affinity of MBP (15.50&#x2009;&#xb1;&#x2009;6.25) was significantly greater than that of MBC (0.50&#x2009;&#xb1;&#x2009;0.84, P&#x2009;<&#x2009;0.001) or MBU (0.33&#x2009;&#xb1;&#x2009;0.52, P&#x2009;<&#x2009;0.001). CONCLUSIONS: Our results indicate that molecular PCI may be considered as a novel and promising imaging modality for the investigation of thrombosis. KEY POINTS: &#x2022; Small thrombi are rarely detected by conventional radiography. &#x2022; Phase contrast imaging (PCI) provides higher contrast and spatial resolution than conventional radiography. &#x2022; P-selectin targeted microbubbles detected by PCI may suggest early thrombosis.