The aim of the current study is to investigate the ability of micro-ultrasound (μUS) to identify microvasculature in CTOs in vivo. Results are compared with MRI studies. CTOs were developed in nine porcine superficial femoral arteries (SFA) by percutaneous insertion of a dissolvable polymer plug. This model is characterized by acute thrombosis that later organizes into a fibrotic CTO containing abundant microchannels. 3D μUS images with Power Doppler (PD) overlays from the arteries were acquired at two timepoints: one and eight weeks after placement of the polymer plug. Phase contrast MRI and contrast enhanced MRI was also performed. Imaging was performed transcutaneously. Microvessels were identified in vivo in six of eight CTOs using μUS, and in three of seven CTO vessels with MRI, compared with five of seven seen histologically. PW Doppler profiles showed pulsatile blood velocities of ∼2 cm/s. Intraluminal microvessels within CTOs can be consistently identified by 3D μUS. This technique appears to be more sensitive than MRI. μUS may play a role in guiding CTO interventions.
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