Coronary Flow Assessment Using 3-Dimensional Ultrafast Ultrasound Localization Microscopy

BACKGROUNDDirect assessment of the coronary microcirculation has long been hampered by the limited spatial and temporal resolutions of cardiac imaging modalities. OBJECTIVESThe purpose of this study was to demonstrate 3-dimensional (3D) coronary ultrasound localization microscopy (CorULM) of the whole heart beyond the acoustic diffraction limit (1000 images/s). METHODSCorULM was performed in isolated beating rat hearts (N = 6) with ultrasound contrast agents (Sonovue, Bracco), using an ultrasonic matrix transducer connected to a high channel-count ultrafast electronics. We assessed the 3D coronary microvascular anatomy, flow velocity, and flow rate of beating hearts under normal conditions, during vasodilator adenosine infusion, and during coronary occlusion. The coronary vasculature was compared with micro-computed tomography performed on the fixed heart. In vivo transthoracic CorULM was eventually assessed on anaesthetized rats (N = 3). RESULTSCorULM enables the 3D visualization of the coronary vasculature in beating hearts at a scale down to microvascular structures (