一种抑制IVUS图像序列中运动伪像的方法

针对连续回撤超声导管采集的冠状动脉血管内超声(intravascularultrasound,IVUS)图像序列中存在由周期性心脏运动所致运动伪像的问题,提出一种抑制方法,以改善IVUS纵向视图的视觉效果。首先,在综合分析运动伪像产生机制和表现形式的基础上,对相邻帧之间血管壁的刚性运动进行定量估计;然后,采用谱分析方法完成刚性运动参数中运动分量和几何分量的分离;最后,通过对各帧图像中血管壁的运动分量进行补偿,完成对运动伪像的抑制。该方法既不需要专门的ECG门控图像采集装置,也无需记录ECG信号,同时不需要抛弃有用帧,在抑制运动伪像的同时保证图像数据集合的完整性。对模拟图像和临床图像的实验验证了方法的可行性。     

用于血管内超声成像的高频换能器研制

血管内超声(Intravascular Ultrasound,IVUS)成像技术可以精确评估血管腔口径、血管壁形态和其他相关血流和血管特性,在冠状动脉疾病的诊断、治疗指导和治疗后的评估中发挥着重要作用。文章设计并制备了一种用于血管内超声成像的高频超声换能器,并对换能器的电学和声学性能进行测试和表征。结果表明,所制备IVUS换能器的中心频率为38.9 MHz,-6 dB相对带宽为56.6%,在谐振频率42.3 MHz处的电阻抗为22.6Ω,在反谐振频率48.2MHz处的电阻抗为56.5Ω,有效机电耦合系数为0.48。使用该换能器进行线仿体成像实验的结果显示,换能器的纵向分辨率为54μm,横向分辨率为209μm。最后,将文中制备的超声换能器与国外同类型换能器进行比较,结果表明,该换能器的性能良好,能够满足血管内超声临床检测需求,未来有望能够突破技术瓶颈,实现国产替代。     

多普勒血流信号最大频率曲线的特征分析及应用

文章主要研究从超声多普勒血流信号的最大频率曲线中提取特征值,并用于临床血管疾病诊断的方法。先利用短时傅里叶变换分析采样所得的音频多普勒血流信号,接着用百分比法得到信号的最大频率曲线,然后提取最大频率曲线频谱各峰值的比作为特征值,并将它们用于血管疾病的诊断。通过对颈动脉多普勒血流信号的临床分析表明：此方法比传统的声谱参数法有更高的诊断准确性。     

调频信号发射超声成像的参数优化与成像实验

研究调频信号发射超声成像中影响成像质量的各种参数,提高现有超声图像的信号噪声比.用仿真计算和声学实验来研究不同调频超声信号发射参数下的成像质量.增加超声发射能量,提高图像的信号噪声比;同时,采用相关算法对接收的超声信号解码,保证图像的轴向精度不会下降.优化了调频信号发射超声成像的发射参数,并得到了仿体的B型超声图像,此图像的质量优于传统成像方法的图像质量.该成像方法能够提高超声图像的信号噪声比,尤其是提高超声衰减严重的深部组织图像的信号噪声比.     

血栓多普勒信号的多参数提取及分类

血栓的准确检测可以用于早期脑血管疾病的诊断，超声多普勒是一种无损的血栓检测技术。文章使用三种信号处理方法：传统的声谱分析法、小波分析法、renyi信息量分析法对血栓多普勒信号进行分析，提取出相应的特征参数，然后对敏感的特征参数采用反向传输(Back-Propagation，简称BP)神经网络进行分类，建立起血栓、干扰噪声和正常血流信号的自动判别系统。通过对300例仿真多普勒信号和163例临床采集的大脑中动脉多普勒信号进行分析，结果表明：本文建立的系统对血栓的检测率高于传统的方法，有望可用于血栓多普勒信号的自动检测。     

应用血管内超声与X射线造影图像融合的血管三维重建

针对X射线血管造影和血管内超声各自显示血管形态的局限以及互补性问题,提出将两种数据进行融合,准确重建血管的方法。首先从在超声导管回撤路径起点拍摄的两个角度的造影图像对中提取出导管并进行三维重建。然后采用基于snake模型的半自动方法从各帧超声图像中提取出血管壁的内外膜边缘。最后,在Frenet-Serret标架中确定各相邻帧超声图像间的相对方位后,利用非迭代的统计优化方法确定各帧超声图像沿导管轴向的绝对方位,完成两种数据的融合。采用临床数据的实验结果验证了算法的可行性,并分析了可能存在的误差和计算成本。     

血管内超声图像后处理综述

血管内超声显像是目前临床常用的诊断血管病变的介入影像手段,可在活体中观察血管壁和管腔的形态,以及斑块的形态和成分。采用数字图像处理技术,对血管内超声图像序列进行自动或半自动地处理和分析,对于血管病变的计算机辅助诊断和制定最佳诊疗方案具有重要意义。本文就近年来血管内超声图像计算机后处理的研究现状进行综述,包括图像分割和组织标定、运动伪影的抑制、血管的三维重建、血管形态和血流动力学参数的测量、组织定征显像及与其他影像的融合等,评价了目前的研究情况,并对未来的研究提出了展望。     

腔内导管超声系统

腔内导管超声已用来评价很多病变,微探头可以置于血管腔内和非血管腔内来显示病变.二维基础上的三维重建在腔内超声图像中是一种新的方法.这篇综述将探讨腔内超声系统装置及一些进展.     

一种基于FPGA的超声信号高速采集与压缩方法

针对超声检测系统中对超声信号的高速采集与处理问题,探讨了一种利用高速模数转换芯片AD9057在特定的时序信号控制下对超声信号进行高速采集,并且在FPGA（现场可编程门阵列）的控制下对采集到的超声信号进行压缩处理的方法。该方法以FPGA作为核心控制单元,结合高速数据采集模块,利用VHDL编程构建双端口的RAM,在FPGA中实现对采集过程中数组的存储与处理。给出了相关的仿真结果以及对实际采集到的超声信号的压缩处理波形,实验结果表明该方法可靠、可行。     

单边狭窄血管中超声多普勒信号的仿真研究

超声多普勒技术作为一种无损检测手段被广泛应用于血管狭窄的检测。以往的血管狭窄仿真信号的研究仅限于双边狭窄的对称情况,文章提出了一种单边狭窄血管中超声多普勒信号的仿真方法。首先用有限元分析方法(FEM)计算出狭窄血管中血流流速场分布情况,然后用总体分布非参数估计法计算出超声多普勒信号的功率谱密度(PSD),再用余弦叠加法获取仿真的超声多普勒时域信号。用快速傅里叶变换(FFT)计算仿真超声多普勒信号的频谱,从中计算最大频率、平均频率和频谱宽度等参数,分析它们在不同流速和狭窄程度下的特征,为血管疾病的诊断提供敏感的参数。     

冠脉内超声多普勒血流信号的极点特征

研究冠脉内超卢多普勒血流信号的极点特征，期望为微循环障碍等缺血性心脏病的诊断提供客观指标。先对冠脉内超声多普勒血流信号分段建立自回归滑动平均（Auto-regressive＆moving-average，即ARMA）模型，获取一个心动用期信号的极点分布，计算极点分布的特征参数。通过分析18例冠脉内超声多普勒血流信号，得出若干个对冠脉微循环障碍敏感的特征参数。结果表明：冠脉内超声多普勒血流信号的极点特征参数，可以一定程度反映冠脉循环的状况。     

Blood speed imaging with an intraluminal array

In applications in which Doppler processing is not possible, such as side-looking intravascular imaging systems, decorrelation methods can be used to estimate blood speed. Here, a method is presented measuring relative blood speed using an FIR filter bank to estimate temporal decorrelation rates. It can be implemented in a modern commercially available ultrasound imaging system with no additional hardware. Both simulations and experiments using an intraluminal scanner appropriate for coronary artery applications have tested the system. In this study, the FIR filter bank is contrasted with previous methods, and its utility is further demonstrated with real-time color flow images from a pig model.     

An equivalent pressure source for the heart

A technique is described for the representation of the left ventricle as a one-port source characterized by a generator pressure and an internal impedance. The Fourier components of the pressure and impedance are determined from phasor analysis performed on recorded time-domain functions of pressure and flow under two conditions of loading. One condition is the quiescent state corresponding to normal operation of the circulatory system, and the other is obtained by use of a phase-shift balloon pump situated in the descending thoracic aorta. The use of the balloon pump for determining source parameters is novel. The Fourier components of pressure and impedance are determined for the first five harmonics of the quiescent pulse rate. Heart failure is simulated by ligation of all branches of the anterior descending coronary artery. The source parameters have been found to vary considerably between normal and failing hearts. Valve impedance and the impedance at the root of the aorta were also measured. The generator time-domain pressure waveforms were determined from the Fourier components. Effects of long duration pumping, upon the source parameters were found. The ratio of the calculated magnitudes of internal to external or load impedance indicates the possibility of considering the heart as a pressure source.     

A numerical study of pulsatile blood flow in an eccentric catheterized artery using a fast algorithm

The pulsatile blood flow in an eccentric catheterized artery is studied numerically by making use of an extended version of the fast algorithm of Borges and Daripa [J. Comp. Phys., 2001]. The mathematical model involves the usual assumptions that the arterial segment is straight, the arterial wall is rigid and impermeable, blood is an incompressible Newtonian fluid, and the flow is fully developed. The flow rate (flux) is considered as a periodic function of time (prescribed). The axial pressure gradient and velocity distribution in the eccentric catheterized artery are obtained as solutions of the problem. Through the computed results on axial pressure gradient, the increases in mean pressure gradient and frictional resistance in the artery due to catheterization are estimated. These estimates can be used to correct the error involved in the measured pressure gradients using catheters.     

下肢截肢患者心血管系统集中参数模型的血流动力学数值研究

下肢截肢虽已发现是心血管疾病的可能危险因素,但潜在的生物力学机制仍未得到充分了解。该研究的目的是了解术后不同时期和生活状态下肢截肢患者的心血管血流动力学状况,以评估异常血流动力学对心血管系统的影响。该文建立了含下肢动脉的心血管系统集中参数模型,模拟了截肢术后、术后成熟期和术后长期久坐三种常见的截肢患者状态。该文以7名下肢截肢患者超声实测下肢动脉直径为模型的参数设置参考。通过将正常人模型和下肢截肢模型的血压和血流量波形对比分析,发现截肢术后血管收缩压和舒张压幅值上升,腹主动脉及以下的动脉流量峰值明显下降;术后成熟期和长期久坐血压在舒张期早期峰值上升。这种异常的血流动力学变化可能是下肢截肢患者患高血压与心室肥大等心血管疾病的危险因素。该文建立的集中参数模型提供了截肢后血流动力学的变化规律,可为未来截肢患者康复治疗和心血管疾病预防提供理论指导。     

A mathematical modeling of pulsatile flow in carotid artery bifurcation

Real carotid arteries are elastic and perfused with a non-Newtonian fluid. The blood flow is pulsatile characterized by the reverse flow regions at the non-divider wall of internal carotid artery and external carotid artery. A coupling effect between fluid flow and elastic deformation is introduced. In addition we have calculated volumetric flow rate, pressure gradient and Impedance due to pulsatile flow in elastic carotid artery. We analyzed the flow at various locations in common carotid artery and internal carotid artery for different frequencies 60, 90, 120 pulse/min and Reynolds number 500 using a compliance mismatch model of carotid artery. Reverse flow of blood increases the impedance and should not be discarded. The problem has been analyzed mathematically and the agreement between present results and the available literature was found to be quite satisfactory.     

Wireless Batteryless Implantable Blood Pressure Monitoring Microsystem for Small Laboratory Animals

A novel, wireless, batteryless, implantable blood pressure monitoring microsystem for small laboratory animals is developed for advanced biological and system biology research. The system employs an instrumented elastic circular cuff, wrapped around a blood vessel, for real-time blood pressure monitoring. The elastic circular cuff is made of soft bio-compatible silicone material, which is filled with bio-compatible insulating fluid with an immersed microelectromechanical systems (MEMS) pressure sensor and integrated electronic system to detect a down-scaled vessel blood pressure waveform. This technique avoids vessel penetration and substantially minimizes vessel restriction due to the soft cuff elasticity, thus attractive for long-term monitoring. A large-model engineering experiment is first developed to verify and demonstrate the concept. A miniature prototype monitoring cuff is then fabricated and implanted in two laboratory rats to evaluate its functionality. A wireless and batteryless monitoring microsystem is then implanted and characterized in a laboratory rat. The measured in vivo blood pressure waveform by the microsystem and a reference waveform recorded by a commercial catheter-tip transducer are closely matched in shape with a constant scaling factor, demonstrating a blood pressure signal with high fidelity can be wirelessly obtained by the implantable monitoring microsystem. The overall implant dissipates 300 ?W, which is powered by an external adaptive RF powering source.     

高强度聚焦超声消融滋养动脉治疗子宫肌瘤的临床价值

目的：探讨高强度聚焦超声消融滋养动脉治疗子宫肌瘤的可行性及有效性。方法：47例直径4~10cm肌壁间肌瘤,高强度聚焦超声治疗前通过彩色多普勒及超声造影确定肌瘤滋养动脉的蒂,对该区域进行消融,观察治疗前后肌瘤内部彩色多普勒及超声造影等影像学变化、随访临床症状及并发症。结果：治疗后肌瘤体积有不同程度的缩小,瘤体假包膜环状血流信号消失,肌瘤内部处于持续无灌注状态,部分患者临床症状消失或明显改善。结论：HIFU消融滋养动脉治疗子宫肌瘤能够缩短治疗时间,减少并发症,是一种微创和有效的方法。     

Quantitative blood speed imaging with intravascular ultrasound

Previously, we presented a method of real-time arterial color flow imaging using an intravascular ultrasound (IVUS) imaging system, where real-time RF A-scans were processed with an FIR (finite-impulse response) filter bank to estimate relative blood speed. Although qualitative flow measurements are clinically valuable, realizing the full potential of blood flow imaging requires quantitative flow speed and volume measurements in real time. Unfortunately, the rate of RF echo-to-echo decorrelation is not directly related to scatterer speed in a side-looking IVUS system because the elevational extent of the imaging slice varies with range. Consequently, flow imaging methods using any type of decorrelation processing to estimate blood speed without accounting for spatial variation of the radiation pattern will have estimation errors that prohibit accurate comparison of speed estimates from different depths. The FIR filter bank approach measures the rate of change of the ultrasound signal by estimating the slow-time spectrum of RF echoes. A filter bank of M bandpass filters is applied in parallel to estimate M components of the slow-time DFT (discrete Fourier transform). The relationship between the slow-time spectrum, aperture diffraction pattern, and scatterer speed is derived for a simplified target. Because the ultimate goal of this work is to make quantitative speed measurements, we present a method to map slow time spectral characteristics to a quantitative estimate. Results of the speed estimator are shown for a simulated circumferential catheter array insonifying blood moving uniformly past the array (i.e., plug flow) and blood moving with a parabolic profile (i.e., laminar flow)     

Oxygen mass transfer in a model three-dimensional artery

Arterial geometry is commonly non-planar and associated with swirling blood flow. In this study, we examine the effect of arterial three-dimensionality on the distribution of wall shear stress (WSS) and the mass transfer of oxygen from the blood to the vessel wall in a U-bend, by modelling the blood vessels as either cylindrical or helical conduits. The results show that under physiological flow conditions, three-dimensionality can reduce both the range and extent of low WSS regions and substantially increase oxygen flux through the walls. The Sherwood number and WSS distributions between the three-dimensional helical model and a human coronary artery show remarkable qualitative agreement, implying that coronary arteries may potentially be described with a relatively simple idealized three-dimensional model, characterized by a small number of well-defined geometric parameters. The flow pattern downstream of a planar bend results in separation of the Sh number and WSS effects, a finding that implies means of investigating them individually.