P3A-6 Non-Invasive Micro-Vascular Ultrasound Elastography: Comparisons with M-Mode Strain Measurements in Rat Models of Hypertension

Noninvasive micro-vascular ultrasound elastography (MicroNIVE) was recently proposed for
in

situ
phenotyping in rat models of hypertension through the assessment of mechanical properties of carotid arteries. This paper reports comparisons between MicroNIVE and M-Mode strain measurements. Brown Norway male rats (n = 5) were investigated over 24 weeks. The common carotid arteries were imaged with an ultrasound biomicroscope equipped with a 40-MHz central frequency probe and an external workstation to collect radio-frequency (RF) data. Time-sequences of RF and M-mode signals were recorded over several consecutive cardiac cycles. MicroNIVE strain cartographies were computed for each pair of successive RF images with the Lagrangian Speckle Model Estimator. Diastolic strain (s
_D
) and systolic strain (s
_s
) parameters were estimated. M- mode strain estimations were computed as s
_M
(t) = (w(t)-w
_max
)/w
_max
, with w(t) and w
_max
being the wall thicknesses at time "t" and at end-diastole, respectively. MicroNIVE diastolic and systolic strains were consistent with a Pearson correlation coefficient (r) of 0.75 (p < 10
^-11
). M-mode and MicroNIVE strain measurements were correlated with r = 0.74 (p < 10
^-5
) between s
_M
and s
_D
and r = 0.67 (p < 10
^-4
) between s
_M
and s
_s
. Corroborated by Bland-Altman plots, M-mode and MicroNIVE were found in very good concordance.