Measurement of turbulent kinetic energy with color Doppler echocardiography and particle tracing velocimetry in an ex-vivo aortic stenosis model

Figures

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  Figure 1. Preparation of the porcine valves. (A) Preparation of the aortic valve: Explanted porcine aortic valve sewn on neoprene fixed between two flanges. The sino-tubular junction is sewn to in indented ring, which is then inserted inside a silicone aorta phantom. (B) Stiffness grades: Three stiffness grades (SGa: native, SGb: stiffer, SGc: stiffest) are obtained through a step-wise stiffening procedure. These grades represent different stages of AS, from healthy valves (SGa) to severely affected ones (SGc).

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  Figure 2. Experimental setup: mock left heart phantom with camera and ultrasound probe. (A) Mock Left Heart Phantom Overview: The experiment includes a motor pump generating flow through a mock left heart flow loop. This loop comprises components such as the left ventricle, aortic valve, silicone aorta phantom, compliance chamber, resistor, left atrium, and mechanical mitral valve. PG are measured using pressure transducers in the left ventricle and in the compliance chamber to assess stenosis severity. Two techniques are used for measuring TKE: backlight PTV via a high-speed camera and colour Doppler echocardiography via an ultrasound probe. The field of view of the TKE measurement using backlight PTV with LED light providing luminosity. (B) Mock Left Heart Phantom: side view. (C) Mock Left Heart Phantom: front view.

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  Figure 3. (A) PG measured using pressure transducers within the aortic (ao) compliance chamber and the left ventricle (lv) chamber (PGaolv) over one cardiac cycle at a flow rate of 1 L/min for the native stiffness grade (SGa), (B) 2.5 L/min for the first added stiffness grade (SGb), and (C) 4 L/min for the second added stiffness grade (SGc). (D) PG measured with continuous wave Doppler ultrasound (PGuscw) at the vena contracta over three cardiac cycles at a flow rate of 1 L/min for the native stiffness grade (SGa), (E) 2.5 L/min for the first added stiffness grade (SGb) and (F) 4 L/min for the second added stiffness grade (SGc). Abbreviations.

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  Figure 4. (A) Assessment of optical refraction: assessment of visual distortion of the calibration target (checkerboard) induced by refraction at the silicone/air interface. (B, C) Matching refraction: adding the blood-mimicking fluid with matched refraction index eliminates visual distortion and ensuring accurate measurements. (D) Camera calibration: the camera's field of view is calibrated using a calibration target with dedicated software to ensure precision in subsequent observations. (E) Field of view picture illustrates the camera's perspective, showing the valve on the left and the field of view highlighted in red. This image represents preliminary findings from experiments employing a different valve cutting techniques and number of cell densities within the field of view G. Computation of the TKE with backlight PTV for native stiffness grade (SGa) at 1 L/min, (H) SGb at 2.5 L/min and (I) SGc at 4 L/min.

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  Figure 5. (A) Raw data acquisition: displays the of the colour Doppler ultrasound with the velocity scale coding within the green box on the top right corner. (B) Image cropping, retaining the field of view containing the colour Doppler velocity data. (C) Velocity map extraction (D) Computation of the TKE with colour Doppler echocardiography using the extracted velocity map.

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  Figure 6. Boxplots presenting the difference between stiffness grades: (SGa: native stiffness grade, SGb: stiffer stiffness grade, SGc: stiffest stiffness grade). The green, blue, and red lines represent the flowrate of 1 L/min, 2.5 L/min, and 4 L/min, respectively. (A) Velocity component parallel to the main axis of the valve. (B) Velocity component perpendicular to the main axis of the valve inside the plane of the field of view. (C & D) Systolic mean and maximal pressure gradient measured with aortic and left ventricle pressures (PGaolv). (E & F) Systolic mean and maximal pressure gradient measured with continuous wave Doppler ultrasound at the vena contracta (PGuscw). (G) & H) Mean and maximal TKE computed with backlight PTV. (I) TKE computed with ultrasound colour Doppler (uscd). (J) TKE computed with backlight PTV normalized to flowrate (nq) (K) TKE computed with uscd normalized to flowrate.

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  Figure 7. Correlation between mean TKE computed with backlight PTV and TKE computed with ultrasound colour Doppler (uscd) with corresponding Pearson correlation coefficient (r).