Validation of Echodynamography in Comparison with Particle-image Velocimetry.

Echodynamography (EDG) is a computational method to estimate and visualize two-dimensional flow velocity vectors by applying dynamic flow theories to color Doppler echocardiography. The EDG method must be validated if applied to human cardiac flow function. However, a few studies of flow estimated have compared by EDG to the flow data were acquired by other methods. In this study, EDG was validated by comparing the analysis of estimating and visualizing flow velocity vectors obtained by original particle image velocimetry (PIV) based on a left ventricular (LV) phantom hydrogel (in vitro studies) and by EDG based on the virtual Doppler velocity. Velocity measured by PIV method and velocity estimated by EDG method in the perpendicular direction and the radial direction were compared. Regression analysis for the velocity estimated in the radial direction revealed an excellent correlation (R2=0.99, slope = 0.96) and moderate correlation in the perpendicular direction (R2=0.44, slope = 0.46). As revealed by the Bland-Altman plot, however, overestimations and higher relative error were observed in the perpendicular direction (0.51 ± 2.75 mm/s) and in the radial direction (-2.15 ± 21.13 mm/s). The percentage error of the norm-wise relative error of the velocity discrepancy is less than 10%, and velocity magnitude followed the same trends and are of comparable magnitude. These findings indicate that good estimates of velocity can be obtained by the EDG method. Therefore, the EDG method was appropriate for estimating and visualizing velocity vectors in clinical studies for higher measurement accuracy and reliability. The clinical in vivo application showed that the EDG method has the ability to visualize blood flow velocity vectors and differentiate the clinical information of vortex parameters both in normal and abnormal LV subjects. In conclusion, the EDG method has potentially greater clinical acceptance as a tool assessment of LV during the cardiac cycle.

Left Ventricular Vortices in Myocardial Infarction Observed with Echodynamography.

Echodynamography (EDG) is a computational method to deduce two-dimensional (2D) blood flow vector from conventional color Doppler ultrasound image by considering that the blood flow is divided into vortex and base flow components. Left ventricular (LV) vortices indicate cardiac flow status influenced by LV wall motion. Thus, quantitative assessment of LV vortices may become new and sensitive parameters for cardiac function. In the present study, quantitative parameters of LV vortices such as vortex index, vortex size, and Reynolds number were calculated and relation between each parameter was assessed. Six healthy volunteers and three patients with myocardial infarction (MI) who underwent color Doppler echocardiography (CDE) were involved in the study. Serial CDE images in apical three-chamber view were recorded and 2D blood flow vector was superimposed on the CDE image. Vortex index, vortex size, and Reynolds number were compared between the normal volunteers and the MI patients. The results showed that vortex index (3.09±2.06 vs. 3.34±2.33, p<; 0.05), vortex size (1.76 0.69 vs. 2.01 ±0.68, p<; 0.05), Reynolds number (1020±603 vs.±1312 1046, p<; ±0.05) were significantly greater in the MI patients than in the healthy volunteers. Vortex equivalent diameter in LV showed significant positive correlation with Reynolds number (R2 = 0.799, y = 0.001x + 0.7098, p <; 0.05) in healthy volunteers and (R2 = 0.6404, y = 0.0005x+1.3185, p<; 0.05) in MI patients. Vortex index showed positive correlation with Reynolds number (R2 = 0.9351, y = 0.002x+0.1397, p<; 0.05) in healthy volunteers and (R2 = 0.758, y = 0.0019x+0.7957, p<; 0.05) in MI patients. In conclusion, EDG provides information on LV hemodynamics by quantitative LV vortices parameters both in healthy volunteers and MI patients.

Left Ventricular Blood Flow Dynamics In Aortic Stenosis Before And After Aortic Valve Replacement.

Surgical intervention for aortic valve stenosis (AS) has been established; however its diagnosis based on echocardiographic assessment is still limited by aortic valvular velocity, aortic valvular pressure gradients, and color Doppler imaging. Echo-dynamography (EDG) is a method to determine intracardiac flow dynamics, such as two-dimensional blood flow velocity, vortex, and dynamic pressure. These flow dynamics may be influenced by left ventricular (LV) wall motion and the resistance in LV outflow caused by AS. The objective of the present study was to assess the changes and differences in LV vortices and vorticity before and after AS surgery. Five patients who underwent aortic valve replacement surgery for AS and five control patients were included. Besides routine echocardiographic measurement, EDG was applied to determine the two-dimensional blood flow vector and vorticity. The LV vortex flow in the isovolumetric contraction phase had multiple formations in preoperative cases. The clockwise vortex was found in all cases postoperatively; the vortex formation showed no significant difference between postoperative and normal control groups. EDG may serve important information on LV flow dynamics, non-invasively.

A Theoretical Model of Laser Heating Carbon Nanotubes.

We present a theoretical model of laser heating carbon nanotubes to determine the temperature profile during laser irradiation. Laser heating carbon nanotubes is an essential physics phenomenon in many aspects such as materials science, pharmacy, and medicine. In the present article, we explain the applications of carbon nanotubes for photoacoustic imaging contrast agents and photothermal therapy heating agents by evaluating the heat propagation in the carbon nanotube and its surrounding. Our model is constructed by applying the classical heat conduction equation. To simplify the problem, we assume the carbon nanotube is a solid cylinder with the length of the tube much larger than its diameter. The laser spot is also much larger than the dimension of carbon nanotubes. Consequently, we can neglect the length of tube dependence. Theoretically, we show that the temperature during laser heating is proportional to the diameter of carbon nanotube. Based on the solution of our model, we suggest using the larger diameter of carbon nanotubes to maximize the laser heating process. These results extend our understanding of the laser heating carbon nanotubes and provide the foundation for future technologically applying laser heating carbon nanotubes.