Ultrasound micro-elastography: A new imaging modality to phenotype hypertension in rat models
Keywords:Biological organs, Blood, Blood vessels, Elasticity, Rats, Stiffness, Ultrasonic imaging, Carotid artery, Elastogram, Strain cartography, Ultrasound probes
AbstractNew ultrasound imaging methods are proposed to non-invasively characterize the mechanical properties of superficial arteries (MicroNIVE) and kidneys (MicroNIKE) in rodents. In MicroNIVE, the vessel wall is compressed/dilated by the blood flow pulsation, whereas time-sequences of high-resolution radio-frequency (RF) ultrasound data are externally acquired. The kinematics of the vascular tissue, assessed with the Lagrangian Speckle Model Estimator (LSME), provides a strain cartography also known as elastogram. Because the LSME assumes linear elasticity conditions, strain is inversely proportional to stiffness, which is an intermediate phenotype of the hypertension (HT) trait. Results are presented for the common carotid artery of spontaneously hypertensive rats (SHR, n = 5) and control normotensive Brown Norway (BN, n = 5) rats. At 15-weeksold, the SHR rats'carotid artery (4.46 ± 1.79% of strain) was found, on average, stiffer that of the BN's, which exhibited strains of 6.76 ± 1.48% (p < .059). On the other hand, in MicroNIKE, the kidney is externally compressed with the ultrasound probe while time-sequences of high-resolution RF data are acquired. For the purpose of investigating the feasibility of MicroNIKE, a fresh excised kidney from a Recombinant Inbred (RI) rat was investigated. The elastograms, computed with the LSME, clearly exhibited the medulla with distinct mechanical properties. It is concluded that MicroNIVE and MicroNIKE are promising new imaging tools to non-invasively and longitudinally study the impact of targeted genes on vascular tissue remodeling and nephroangiosclerosis in engineered rat models of HT.
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