Nonlinear multiscale wavelet diffusion for speckle suppression and edge enhancement in ultrasound images.

This paper introduces a novel nonlinear multiscale wavelet diffusion method for ultrasound speckle suppression and edge enhancement. This method is designed to utilize the favorable denoising properties of two frequently used techniques: the sparsity and multiresolution properties of the wavelet, and the iterative edge enhancement feature of nonlinear diffusion. With fully exploited knowledge of speckle image models, the edges of images are detected using normalized wavelet modulus. Relying on this feature, both the envelope-detected speckle image and the log-compressed ultrasonic image can be directly processed by the algorithm without need for additional preprocessing. Speckle is suppressed by employing the iterative multiscale diffusion on the wavelet coefficients. With a tuning diffusion threshold strategy, the proposed method can improve the image quality for both visualization and auto-segmentation applications. We validate our method using synthetic speckle images and real ultrasonic images. Performance improvement over other despeckling filters is quantified in terms of noise suppression and edge preservation indices.

Nitric oxide versus prostaglandin E1 for reduction of pulmonary hypertension in heart transplant candidates.

BACKGROUND: We sought to directly compare the effects of prostaglandin E1 (PGE1) and nitric oxide (NO) in testing for pulmonary hypertension reversibility in heart transplant candidates. METHODS: We included 19 heart transplant candidates who fulfilled at least 1 of 3 criteria: pulmonary vascular resistance (PVR) of >4 Wood units; transpulmonary gradient (TPG) of >12 mmHg; or systolic pulmonary artery pressure (PAP) of >60 mmHg. Patients randomly received either PGE1 (0.05, 0.2 and 0.5 microg/kg/min) or NO (40, 60 and 80 ppm) and were crossed-over to the second medication after receiving the maximal dose of the first. RESULTS: With PGE1, TPG decreased by 21% (baseline 20.3 +/- 6.8 mmHg; final 16.0 +/- 7.0 mmHg) compared to a 34% decrease with NO (baseline 20.8 +/- 6.2 mmHg; final 13.8 +/- 5.4 mmHg) (p = 0.13). PVR decreased by 42% with PGE1 (baseline 6.2 +/- 4.0 Wood units; final 3.6 +/- 1.8 Wood units) and by 47% with NO (baseline 6.0 +/- 3.9 Wood units; final 3.2 +/- 1.6 Wood units) (p = 0.87). Mean systemic pressure decreased with PGE1 (baseline 76.1 +/- 10.5 mmHg; final 69.4 +/- 12.2 mmHg; -9%) but not with NO administration (baseline 70.2 +/- 14.7 mmHg; final 71.6 +/- 10.9 mmHg; +2%) (p = 0.01). TPG was lowered to <12 mmHg in 14 patients. Of these, 6 (46%) responded to both PGE1 and NO, 4 (27%) responded only to PGE1, and 4 (27%) responded only to NO. CONCLUSIONS: The effects of PGE1 and NO on pulmonary hypertension are comparable, with PGE1 having more systemic hypotensive effects. Due to variability of patient responses, we recommend multiple rather than single-agent pharmacologic testing for the reversibility of pulmonary hypertension.

Evaluation of myocardial function in patients with end-stage heart failure during support with the Jarvik 2000 left ventricular assist device.

In 2 patients with the Jarvik 2000 left ventricular assist device (LVAD), we assessed left ventricular systolic function through pressure-volume loops and E(max) at the beginning and end of the support period to potentially predict the possibility of pump removal without transplantation. Immediately before LVAD implantation and explantation, pressure and volume measurements were made with catheters and echocardiography, respectively, the E(max) being calculated from the slope of the pressure-volume loops, and the left ventricular ejection fraction (LVEF) being estimated by echocardiography. Transplantation was performed after 14 and 62 days, respectively, during which the LVEF increased by 75% (from 12% to 21%) in Patient 1 and remained unchanged (from 16% to 18%) in Patient 2, whereas the E(max) increased from 0.63 and 0.42 mm Hg/ml, respectively, to 1.31 and 1.07 mm Hg/ml, reflecting a 107% and 155% improvement. In these 2 cases, the E(max) was a more reliable indicator of intrinsic myocardial contractility than was the LVEF.

Ultrasound speckle suppression and edge enhancement using multiscale nonlinear wavelet diffusion.

This paper introduces a novel multiscale nonlinear wavelet diffusion (MNWD) method for ultrasound speckle suppression and edge enhancement. It considers wavelet diffusion as an approximation to nonlinear diffusion within the framework of the dyadic wavelet transform. Consequently, this knowledge is exploited in the design of a speckle suppression filter with an edge enhancement feature. MNWD takes advantage of the sparsity and multiresolution properties of wavelet, and the iterative edge enhancement feature of nonlinear diffusion. In our algorithm, speckle is suppressed by employing the iterative multiscale diffusion on the wavelet coefficients, while the edges of the image are enhanced by using an iterative signal compensation process. We validate the proposed method using synthetic and real echocardiographic images. Performance improvement over other traditional denoising filters is quantified in terms of noise suppression and structural preservation indices. The application of the proposed method is demonstrated by the segmentation of the echocardiographic image using the active contour.

Echocardiographic evaluation of the Jarvik 2000 axial-flow LVAD.

From April 2000 through September 2001, we studied 11 patients with the Jarvik 2000--a left ventricular assist device with an axial-flow pump that provides continuous blood flow--to determine the echocardiographic characteristics. All patients underwent complete echocardiographic examination, including outflow-graft flow evaluation 24 hours after implantation and each month thereafter for the duration of support. Data were obtained at each pump setting (8000-12000 rpm in 1000-rpm increments) and with the pump off. Left ventricular dimensions and shortening fraction and the duration of aortic valve systolic opening decreased as pump speed increased. Although the aortic valve remained closed at higher pump speeds, pump outflow-graft flow remained pulsatile, because of the systolic thrust of the assisted ventricle. Systolic dominance of phasic flow was more pronounced at lower pump speeds, due to normalization of the diseased heart's Starling response. When the aortic valve was closed continuously, echocardiographic contrast (indicating blood stasis) was noted in the aortic root. Because of the pump outflow graft's proximity to the chest wall, device output could be measured independently of cardiac contributions. Mean peak outflow-graft flow velocities were 0.75 +/- 0.30 m/s (systolic) and 0.41 +/- 0. 13 m/s (diastolic). When the pump was turned off briefly there was minimal regurgitation through the device into the left ventricle. This 1st echocardiographic heart function analysis of the Jarvik 2000 confirms that the device unloads the ventricle and increases cardiac output. Cardiac responses to device-speed changes can be evaluated readily with echocardiography in the early and late postoperative period.

Initial clinical experience with the Jarvik 2000 implantable axial-flow left ventricular assist system.

BACKGROUND: Implantable left ventricular assist systems (LVASs) are used for bridging to transplantation, bridging to myocardial improvement, and for permanent circulatory support. Conventional implantable systems have inherent limitations that increase morbidity during support. In contrast, small, efficient, axial-flow pumps, which have been under development for the past decade, have the potential to improve the length and quality of life in patients with severe heart failure. Methods and Results- To assess the safety and clinical utility of the Jarvik 2000, we implanted this device in 10 transplant candidates (mean age 51.3 years) in New York Heart Association (NYHA) class IV. Implantation was achieved through a left thoracotomy during partial cardiopulmonary bypass. The mean support period was 84 days. Within 48 hours postoperatively, the cardiac index increased 43%, pulmonary capillary wedge pressure decreased 52%, systemic vascular resistance decreased significantly, and inotropic support became unnecessary. Eight patients underwent physical rehabilitation and returned to NYHA class I. Their left ventricular dimensions, cardiothoracic ratios, and pressure-volume loop analyses showed good left ventricular unloading. Seven patients underwent transplantation and 3 died during support. No device thrombosis was observed at explantation. CONCLUSIONS: The Jarvik 2000 functions as a true assist device by partially unloading the left ventricle, thereby optimizing the patient's hemodynamics. Our preliminary results indicate that this LVAS may safely provide circulatory assistance for heart transplant candidates.