Kiyotsugu Sekioka

Automatic left ventricular endocardium detection in echocardiograms based on ternary thresholding method

This study proposes a new automatic detection method based on ternary thresholding method for echocardiograms. Two thresholds are determined by the discriminant analysis for the gray level histogram so that the input image is segmented into three regions: cardiac cavity, near epicardium, and the rest. Then the input echocardiogram is binarized with the lower threshold (between black and gray) to detect the cardiac cavity. The binary images are contracted n times to remove small regions and to disconnect the region of cardiac cavity from the other false regions. Among the obtained regions which corresponds to the cardiac cavity is selected and dilated 2n times to create a mask which restricts the region of the second thresholding operation. The masked image of each frame is binarized with another threshold determined by the discriminant analysis in the restricted area. Results of the evaluation test showed that the accuracy of the extracted contours was favorably compared with the accuracy of manually traced contours.The purpose of this edge detection and segmentation method for two-dimensional echocardiogram is to present the procedures to detect and segment an image from Two-dimensional echocardiogram and to generate a scanline that can be used to detect the distance between two endocardiums which is useful to analyze heart disease. This method applies image processing and computer graphic algorithms which were divided into 3 steps. Firstly, we used image improvement algorithms of noise suppression, histogram, brightness adjustment, threshold and median filtering. Then, edge detection algorithm with sobel compass gradient mask was applied to show the edge of endocardium border. Finally, segmentation and some computer graphics algorithms were used to identify and generate contour line of the endocardium border. Later in the study, Pearson correlation coefficient was used to evaluate performance of this method compared with that of manual track. The average correlation computes from this method is 0.9 which shows a good result because 0.9 is very close to 1. However, some part of contour line has a big error value. The unexpected result from incomplete of endocardium border came from color value of some part of border very close to background or noise color value. This problem occurred in first step can be solved by carefully collecting in collection process.

Sevoflurane anaesthesia for one-lung ventilation with PEEP to the dependent lung in sheep: effects on right ventricular function and oxygenation

This study was undertaken to examine the effect of sevoflurane on right ventricular junction, the safety of sevoflurane for onelung ventilation and the effects of PEEP (positive end-expiratory pressure) to the dependent lung in this model using 12 openchest sheep. Haemodynamic variables, including cardiac output, mean arterial blood pressure, right ventricular pressure and pulmonary arterial pressure, and right ventricular segment shortening (sonomicrometry) were measured. First, animals received 2.0, 3.0 or 4.0% sevoflurane for 20 min each, respectively, during two-lung ventilation to measure the dose-dependent haemodynamic effects of sevoflurane. Then one-lung ventilation was performed with a randomized sequence of 0 (ZEEP), 5 and 10 cm H2O PEEP to the dependent lung under 2.0% sevoflurane anaesthesia after one-hour stabilization. A decrease in systolic segment shortening along with increases in both the end-diastolic and end-systolic lengths of the right ventricle were observed at 3.0 and 4.0% sevoflurane, while global right ventricular function remained substantially unchanged during twolung ventilation. During one-lung ventilation the PaO2 was greater with 5 cm H2O PEEP 198 mmHg (± 25 SEM) than with ZEEP 138 mmHg (± 22) or with 10 cm H2O PEEP 153 mmHg (± 23) (P < 0.05). No differences in haemodynamic variables or segment shortening between ZEEP and PEEPs during one-lung ventilation were observed. We conclude that although sevoflurane causes a dose-dependent depression of right ventricular function, sevoflurane anaesthesia can be safely applied to one-lung ventilation, and that 5 cm H2O PEEP to the dependent lung can improve arterial oxygenation without causing changes in right ventricular function.RésuméCe travail vise à évaluer les effets du sévoflurane sur la fonction ventriculaire droite, sa sécurité en ventilation monopulmonaire et les effets de la pression positive télé-expiratoire (PEEP) sur le poumon inférieur à thorax ouvert chez 12 moutons. On mesure les variables hémodynamiques habituelles: débit cardiaque, pression artérielle moyenne, pression ventriculaire droite, pression artérielle pulmonaire; et par sonomicrométrie, le raccourcissement segmentaire ventriculaire droit. D’abord, les animaux sont anesthésiés au sévoflurane à 2,0, 3,0, or 4,0% pour 20 minutes pendant la ventilation bipulmonaire pour mesurer les effets hémodynamiques du sévoflurane. Ensuite, la ventilation monopulmonaire est initiée avec une séquence randomisée de 0 (ZEEP), 5 et 10 cm H2O PEEP sur le poumon inférieur et maintenue à une concentration de sévoflurane 2% pour une période de stabilisation d’une heure. Une diminution du raccourcissement systolique segmentaire droit et un allongement télédiastolique et télésystolique ventriculaire droit simultanés sont observés sous sévoflurane 3,0 et 4,0%. La fonction ventriculaire droite globale demeure inchangée pendant la ventilation bipulmonaire. Pendant la ventilation monopulmonaire, la PaO2 est plus élevée sous PEEP 5 cm H2O (198 mmHg ± 25 SEM) que sous ZEEP (138 mmHg ± 22) ou sous PEEP 10 cm H2O (153 mmHg ± 23) (P < 0,05). On n’observe pas de différences entre les diverses variables hémodynamiques et au regard du raccourcissement segmentaire entre le ZEEP et le PEEP pendant la ventilation monopulmonaire. Nous concluons que bien que le sévoflurane puisse produire une dépression de la fonction ventriculaire droite proportionnelle à la dose, le sévoflurane peut être utilisé avec sécurité pour la ventilation monopulmonaire et qu’une PEEP de 5 cm H2O appliquée au poumon inférieur peut améliorer l’oxygénation artérielle sans modifier la fonction ventriculaire droite.

MCI-154, a Ca2+ sensitizer, decreases the oxygen cost of contractility in isolated canine hearts

An increase in the responsiveness of the contractile machinery to Ca2+ could theoretically enhance the mechanoenergetics of the heart. To clarify this unresolved issue, we studied the effects of MCI-154, a Ca2+ sensitizer, on the mechanoenergetics in terms of the left ventricular contractility index [slope of end-systolic pressure-volume relationship (Emax)] and the relationship between myocardial oxygen consumption (VO2) and left ventricular pressure-volume area in excised cross-circulated canine hearts. MCI-154 increased Emax by 42 +/- 31% (SD), although the slope of the VO2-PVA relationship (an indicator of contractile efficiency) was unchanged by MCI-154. Despite equal increases in Emax, the relative increase in unloaded VO2 (delta VO2/delta Emax) during infusion of MCI-154 was, however, significantly less than that during CaCl2 infusion (0.0016 +/- 0.0018 vs. 0.0059 +/- 0.0054; P < 0.05). By contrast, delta VO2/delta Emax for milrinone was the same as that for CaCl2 (0.0043 +/- 0.0041 vs. 0.0039 +/- 0.0045; P > 0.05). Basal metabolism in KCl-arrested hearts was unchanged by MCI-154, indicating that MCI-154 consumes less energy than CaCl2 for excitation-contraction coupling. These findings suggest that MCI-154 acts energetically as a Ca2+ sensitizer in beating canine whole hearts.An increase in the responsiveness of the contractile machinery to Ca2+could theoretically enhance the mechanoenergetics of the heart. To clarify this unresolved issue, we studied the effects of MCI-154, a Ca2+ sensitizer, on the mechanoenergetics in terms of the left ventricular contractility index [slope of end-systolic pressure-volume relationship ( E max)] and the relationship between myocardial oxygen consumption (Vo 2) and left ventricular pressure-volume area in excised cross-circulated canine hearts. MCI-154 increased E max by 42 ± 31% (SD), although the slope of the Vo 2-PVA relationship (an indicator of contractile efficiency) was unchanged by MCI-154. Despite equal increases in E max, the relative increase in unloaded Vo 2(ΔVo 2/Δ E max) during infusion of MCI-154 was, however, significantly less than that during CaCl2 infusion (0.0016 ± 0.0018 vs. 0.0059 ± 0.0054; P < 0.05). By contrast, ΔVo 2/Δ E maxfor milrinone was the same as that for CaCl2 (0.0043 ± 0.0041 vs. 0.0039 ± 0.0045; P > 0.05). Basal metabolism in KCl-arrested hearts was unchanged by MCI-154, indicating that MCI-154 consumes less energy than CaCl2 for excitation-contraction coupling. These findings suggest that MCI-154 acts energetically as a Ca2+ sensitizer in beating canine whole hearts.

Speckle Reduction of Echocardiograms via Wavelet Shrinkage of Ultrasonic RF Signals

We propose a new speckle reduction algorithm for clinical echocardiograms. The proposed method employs Wavelet Shrinkage to reduce the noise on an ultrasonic signal. In the wavelet shrinkage, at first, original ultrasonic signal is decomposed into wavelet coefficients by multiresolution de- composition using orthogonal wavelet. A threshold of which objective is suppression of noise component is estimated on the resultant complex wavelet coefficient. Wavelet coefficients corresponding to noise are eliminated by soft-thresholding. The noise reduction by the wavelet shrinkage can remove specific frequency components. In this study, we employed the RI-Spline wavelet that was proposed as a shift-invariant moth- er wavelet. We conducted experiments using clinical ultrasonic signals to evaluate the noise reduction performance of the proposed method. Ten clinical subjects were used in the ex- periments. The experimental results show that the algorithm provides superior performance on speckle and noise reduction compared to that of existing speckle reduction method.

Differences in direction-dependent shortening of the left ventricular wall in hypertrophic cardiomyopathy and in systemic hypertension

To determine whether patients with hypertrophic cardiomyopathy (HC) have an altered mode of contraction of the left ventricular (LV) wall related to underlying myocardial abnormalities, geometric changes in the LV wall were analyzed at 2 points of the cardiac cycle (end-diastole and end-systole) using 2-dimensional echocardiography. The relations between meridional and circumferential shortening of the LV midwall, mean wall thickening, and the changes in the short-axis cross-sectional area of the LV wall at the level of chordae tendineae were determined in 18 patients with nonobstructive HC, and were compared with those in 31 normal subjects and 19 patients with essential systemic hypertension. In normal subjects, no significant difference was observed between meridional (16.3 +/- 2.4%) and circumferential (17.1 +/- 4.0%) shortening, whereas cross-sectional LV wall area increased significantly at end-systole (p < 0.001). In patients with hypertension, all measured indexes were not different from those in normal subjects. In contrast, patients with HC had significantly reduced meridional shortening (p < 0.001) and mean wall thickening (p < 0.01). Consequently, a striking difference was observed between meridional (8.9 +/- 2.4%) and circumferential (16.9 +/- 3.2%) shortening (p < 0.001). Furthermore, no increase in cross-sectional LV wall area was observed at end-systole. Thus, echocardiographic detection of direction-dependent contraction can be a useful index for distinguishing HC from systemic hypertension.

Automatic tracking of local myocardial motion by correlation weighted velocity method

In this paper, we propose a new method for automatically tracking the motion of local region in left ventricular myocardium by means of ultrasonic pulsed Doppler signal. This method consists of a velocity detection procedure based on correlation weighted mean instantaneous velocity and a motion tracking procedure employing a myocardial elastic model. Most of ultrasonic pulsed Doppler signals observed in clinical diagnosis contain considerable amount of speckle noise, which causes detection error of velocity. The detection error is accumulated in the motion tracking procedure and yields obviously incorrect motion trajectory. The procedure of correlation weighted mean velocity is aimed to reduce the velocity detection error and the myocardial elastic model is used to avoid the accumulation of the error to keep track of the motion of the myocardium in reasonable accuracy. The result of evaluation test shows that this method is able to improve the accuracy of tracking approximately 40% relative to a conventional CLS approach.

Changes in calcium transient and left ventricular function during positive inotropic stimulation and myocardial ischemia in indo-1-loaded beating guinea pig heart

To elucidate the issues such as excitation-contraction coupling and myocardial ischemia, it is necessary to measure intracellular free Ca2+ concentration and mechanical function of hearts perfused via the normal arterial circulation. For this purpose, we simultaneously measured Ca(2+)-dependent indo-1 fluorescence and left ventricular (LV) pressure on a beat-to-beat basis in Langendorff guinea-pig hearts, and investigated the changes in Ca2+ transient and LV function during inotropic stimulation and myocardial ischemia. The indo-1 fluoresence ratio and LV developed pressure increased the perfusate [Ca2+] increased from 1.6 to 3.2 mmol/L, and there was a good correlation between Ca2+ transient and LV contractility. Digoxin (10(-6) mol/L) and milrinone (10(-5) mol/L) increased LV contractility with a concomitant increase in Ca2+ transient, and the relative increase of Ca2+ transient produced by milrinone was much more than that by digoxin. The reduction of coronary perfusion pressure from 80 to 40 mm Hg decreased LV contractility with an increase in indo-1 fluorescence ratio. These results suggest that Ca2+ responsiveness of contractile apparatus declines during inotropic stimulation by milrinone and during myocardial ischemia. Thus, this experimental technique is useful to investigate the interrelation of Ca2- regulation and LV function during a variety of pharmacological and physiologic perturbations.

Quantitative Assessment of Left Ventricular Myocardial Motion Using Shape-Constraint Elastic Link Model

We propose a novel technique to track the motion of the left ventricular myocardium on a sequence of transthoracic two-dimensional echocardiogram. Although the proposed method is generally based on the traditional correlation based motion tracking, the tracking accuracy and stability are improved by the introduction of new objective function. In our method, the objective function is defined from the model where multiple Regions of Interest (ROIs) are connected to each other with elastic links. The elastic links reflect both elastic and shape properties of myocardium. The proposed method is implemented and evaluated using ten clinical subjects. The experimental results show that the tracking accuracy of the proposed method is higher than that of the conventional method.

Motion Tracking of Local Myocardial Tissue Using a DP+E Tracking Method on M-mode Echocardiograms

We propose a new methodology for motion tracking of local myocardial tissue on M-mode echocardiograms. This methodology is applicable to the quantitative assessment of myocardial performance in clinics. The M-mode echo cardiogram is widely used in clinics to measure diagnostic indexes like thickening and thinning of myocardial muscle layers. To measure such indexes, doctors are required to track myocardial motion manually, however the tracking of myocardial motion by hand is tedious and time-consuming process. Our proposed method is able to tracking the myocardial motion on M-mode echocardiograms automatically by employing DP-based optimization. In this report we present the proposed method.

3-D Display of the Wall Motion for Regional Cardiac Muscle from Ultrasonic B-mode Image -Wall Motion of Thickness, Thickening Rate using Contour of Inner and Outer Wall-

We have developed extracting the inner and outer walls of the cardiac muscle from a set of ultrasonic B-mode images. In this paper, we propose a new 3-D (radius, angle and time) display method of the motion function on the inner wall to evaluate the motion of the myocardium objectively. Its method displays the time transition of a cardiac wall during one cardiac cycle, and it is colored the thickness or the thickening rate of the myocardium on the surface of the 3-D object. The inner and outer walls of the heart are extracted from a set of ultrasonic B-mode Images. We implemented 3-D display system using C language and DirectX 3D in MS-Windows. We calculate the position of the points for 3-D display from the contour lines of the cardiac muscle by the cubic spline curve. The curve connects smoothly between one point and the other one point. And we found the thickness and thickening rate by using the contour lines of the cardiac muscle. We define the thickness by the shortest distance between the outer wall and the inner wall, and we calculate the thickness rate from the obtained thickness. We add the rotation view of the 3-D object to see the every side of myocardium. We confirmed the usefulness of our 3-D display.