Novel Contrast-Enhanced Ultrasound for Imaging Platelets
Platelets play a crucial role in both normal hemostasis and pathological thrombosis. The ability to locate sites of platelet accumulation would aid in the identification of blood clots during ultrasonic imaging. A research team at the BRIC co-led by Dr. Amy Oldenburg and Dr. Caterina Gallippi has recently reported a novel method for contrast-enhanced ultrasound to detect platelet-rich blood clots. This work was recently highlighted in MedicalPhysicsWeb and reported in Physics in Medicine and Biology. The method makes use of a time-varying magnetic field gradient to mechanically modulate platelets containing SPIOs (superparamagnetic iron oxides). Importantly, while SPIOs are non-echogenic and generally not detectible via normal ultrasound, this magnetomotive ultrasound method detects the induced motion of echogenic materials mechanically coupled to the SPIOs (Fig. 1).
Fig. 1. Concept diagram of magnetomotive ultrasound hardware.
This system was deployed to image platelet-rich clots embedded within tissue phantom material (Fig. 2). In comparison to negative controls, SPIO-platelets formed into a blood clot exhibited over 6 dB of signal above the background (Fig. 2). The long-term direction of this research is to use rehydratable lyophilized (RL) platelets that are tagged with SPIOs to monitor their efficacy in hemostasis applications, and to use them as sentinels to detect pre-occlusive thrombosis. In the immediate future, the team plans to study in vivo animal models of vascular damage in collaboration with the Francis Owen Blood Research Laboratory to address remaining challenges on the pathway to translation.
Fig. 2. En face magnetomotive ultrasound images of an agar phantom (left), and an SPIO-platelet rich blood clot embedded in agar (right).