超声心动图评价左房形态和功能的临床应用进展

左房形态和功能既可反映机体的生理状态,也可反映其病理状态,左房形态和功能异常改变是冠心病、高血压、心血管硬化、中风等诸多心血管疾病的早期表现之一,是心血管死亡、心肌梗死、卒中、心力衰竭等不良心血管事件的危险因素之一,与这类疾病的预后密切相关,因而准确、有效评估左房形态和功能在不良心血管事件的诊疗及预后评估中意义重大。采用超声心动图评价左房形态和功能具有无创、实时高效、价格低廉及可重复性高等优点,临床上应用非常广泛。随着超声技术的进步,除二维超声心动图、彩色多普勒超声心动图等常规超声技术外,组织多普勒显像(TDI)技术、由TDI派生出来的应变及应率显像技术、实时三维超声心动图(RT-3DE)、二维斑点追踪成像(2D-STI)技术、三维斑点追踪成像(3D-STI)技术等新型超声技术也逐渐应用于左房形态、功能的评价中,然而不同的超声技术评价左房形态和功能仍有一定的不足之处,本研究就不同超声心动图评价左房形态和功能的临床应用及研究进展进行综述。     

Contrast-enhanced ultrasound imaging of prostate cancer

Ultrasound imaging of the prostate is commonly used to assess the size of the gland and for needle placement during systematic biopsy. Ultrasound evaluation of prostate cancer is limited by difficulty in distinguishing benign from malignant tissue. Although Doppler techniques may provide some improvement in the detection of prostate cancer, targeted biopsy based on conventional ultrasound with Doppler is not sufficient to replace systematic biopsy. Contrast-enhanced ultrasound imaging techniques that employ microbubble contrast agents represent an innovative approach to imaging of the neovascularity associated with prostate cancer. This review describes the application of contrast-enhanced ultrasound to improve detection and assessment of prostate cancer.     

Evaluation of biological effects induced by diagnostic ultrasound in the rat foetal tissues

In recent years, there has been growing interest in estimating the degree of heating caused by the diagnostic ultrasound in clinical practice. Both theoretical and experimental methods have been suggested for estimating the heating potential, or thermal hazard, of diagnostic ultrasound. Aim of this study was to evaluate in vivo effects of ultrasound exposure of variable duration (from 10 up to 20 min) with commercially available imaging systems commonly used for diagnostic imaging. Numerical results related to the thermal effect are obtained by simulation program based on B-mode (scanning) and Doppler (non-scanning). To investigate the biological effects of the ultrasound exposure to the brain and liver tissues, the antioxidant enzyme activity and thiobarbituric acid reactive substances (TBARS) of the tissues were evaluated. In liver tissue, as a lipid peroxidation index, TBARS levels very significantly increase in Doppler group compared to control. However, in B-mode, TBARS levels are the same with the control group. Use of B-mode in foetal tissue is more reliable than Doppler mode because temperature rise is very small compared to the Doppler mode. On the other hand, the antioxidant enzyme activities tend to increase in B-mode and Doppler groups compared to the control group as a defensive mechanism. In the brain tissue, lipid peroxidation is increased slightly in B-mode compared to the control group. This situation is related to the molecular structure of the brain tissue because of its high lipid concentration. In brain tissue, the antioxidant enzyme activities and lipid peroxidation were significantly increased, such as liver tissue in Doppler groups. Doppler ultrasound may produce harmful effects in rat foetus liver and brain tissues as a result of the high temperature rises.     

Implementation of a field programmable gate array based transcranial Doppler ultrasound system using pulse compression techniques

A field programmable gate array (FPGA) based hardware platform that is used to implement a digital, multi-gate pulsed Doppler ultrasound system for transcranial Doppler (TCD) use is described. The Doppler audio signal is extracted from the digitised radio-frequency signal by matched filtering and suitable sampling. The system was configured to acquire Doppler signals from 16 depth locations and to display Doppler signal power versus depth as well as a sonogram from a user specified depth. The signal-to-noise performance of the system was comparable with that of a commercially available TCD unit for equivalent pulse repetition frequency and sample volume settings.The flexibility of the platform was used to demonstrate the feasibility of using coded transducer excitation and pulse compression techniques to improve axial resolution compared to a non-coded implementation. The axial resolution improvement was demonstrated using a flow phantom and measured using a vibrating wire phantom. The measured resolutions were 9.1 and 2.4 mm for the conventional and coded implementations, respectively. The reduction in signal-to-noise ratio of approximately 5 dB associated with the configuration using coded excitation was attributable to the frequency response characteristics of the transducer rather than the processing technique used. This work demonstrates both the flexibility associated with an FPGA implementation of a Doppler ultrasound system and the potential for coded excitation to improve axial resolution in TCD systems.     

Doppler echocardiographic reference values for healthy rhesus monkeys under ketamine hydrochloride sedation

Cardiac ultrasound is a noninvasive technique that is commonly used to serially evaluate cardiac structure and function. Recent advances in Doppler-Echocardiography enable the ultrasonographer to perform a sophisticated noninvasive assessment of cardiovascular physiology. The Rhesus monkey is a frequently used non-human primate animal model of human cardiovascular disease because this species closely models human anatomy and physiology. However, while this species is frequently used in cardiovascular research, standardized echocardiographic values generated from large numbers of normal Rhesus are not available. In the present study, we performed cardiac ultrasound imaging on 28 healthy Rhesus monkeys to obtain normal reference values of cardiovascular structure and function in this species. Nomograms were generated from these data by plotting parameters of cardiovascular geometry and function with body weight. These normal reference data were compared to previously reported values obtained from prior studies that used noninvasive, invasive, and morphometric techniques. Cardiac ultrasound is a noninvasive technique that is commonly used to serially evaluate cardiac structure and function. Recent advances in Doppler-Echocardiography enable the ultrasonographer to perform a sophisticated noninvasive assessment of cardiovascular physiology. The Rhesus monkey is a frequently used non-human primate animal model of human cardiovascular disease because this species closely models human anatomy and physiology. However, while this species is frequently used in cardiovascular research, standardized echocardiographic values generated from large numbers of normal Rhesus are not available. In the present study, we performed cardiac ultrasound imaging on 28 healthy Rhesus monkeys to obtain normal reference values of cardiovascular structure and function in this species. Nomograms were generated from these data by plotting parameters of cardiovascular geometry and function with body weight. These normal reference data were compared to previously reported values obtained from prior studies that used noninvasive, invasive, and morphometric techniques.     

Improved biomechanical metrics of cerebral vasospasm identified via sensitivity analysis of a 1D cerebral circulation model

Cerebral vasospasm (CVS) is a life-threatening condition that occurs in a large proportion of those affected by subarachnoid haemorrhage and stroke. CVS manifests itself as the progressive narrowing of intracranial arteries. It is usually diagnosed using Doppler ultrasound, which quantifies blood velocity changes in the affected vessels, but has low sensitivity when CVS affects the peripheral vasculature. The aim of this study was to identify alternative biomarkers that could be used to diagnose CVS. We used a 1D modelling approach to describe the properties of pulse waves that propagate through the cardiovascular system, which allowed the effects of different types of vasospasm on waveforms to be characterised at several locations within a simulated cerebral network. A sensitivity analysis empowered by the use of a Gaussian process statistical emulator was used to identify waveform features that may have strong correlations with vasospasm. We showed that the minimum rate of velocity change can be much more effective than blood velocity for stratifying typical manifestations of vasospasm and its progression. The results and methodology of this study have the potential not only to improve the diagnosis and monitoring of vasospasm, but also to be used in the diagnosis of many other cardiovascular diseases where cardiovascular waves can be decoded to provide disease characterisation.     

Comparison of blood flow parameters measured by Doppler ultrasound and radionuclide techniques in the baboon (Papio ursinus)

Ascending aortic blood velocity was measured in the baboon (Papio ursinus) by using continuous wave Doppler ultrasound. The blood flow parameters thus obtained were compared to those by the standardized radionuclide technique. It appears that, due to the anatomical position of the ascending aorta and brachiocephalic trunks in relation to the ultrasound beam, Doppler ultrasound does not provide an accurate method of measuring aortic blood velocity in the baboon, which could be the reason for the poor correlation of the results from the two techniques.     

The thin latissimus dorsi perforator-based free flap for resurfacing

The authors present their experience with "thin" latissimus dorsi perforator-based free flaps for resurfacing defects. Perforator-based free flaps have been used for various kinds of reconstruction by presenting important donor structures. The thin latissimus dorsi perforatorbased free flap included only the skin and superficial adipose layer to reduce its bulkiness by dissection through the superficial fascial plane. This flap was used in 12 clinical cases, without flap necrosis or other serious postoperative complications. All of the patients were examined by preoperative power Doppler ultrasound in the spectral Doppler mode to search for the most reliable perforator. This noninvasive ultrasound technique determines the exact location and course of and ensures the reliable flow of the perforators; therefore, it greatly assists microsurgeons in saving operation time and in selecting the most suitable design for perforator flap reconstruction. We used perforators that were identified several centimeters from the lateral border of the latissimus dorsi muscle. The thin flap dimensions could be safely designed for flaps measuring up to 20 cm in length and 8 cm in width for primary closure of the donor site. Generally, a long pedicle is not required for resurfacing reconstructions, where small recipient arteries in the bed are acceptable for anastomosis with pedicles. However, pedicle dissection to the proximal vessels through the latissimus dorsi muscle was required when it was necessary to match the recipient vein for anastomosis. The authors conclude that this thin latissimus dorsi perforator-based free flap has great potential for resurfacing because of its constant thickness, easy elevation with the help of power Doppler ultrasound information, and proper flap size for moderate defects caused by scar contracture release, superficial tumor ablation, and so on.     

Doppler velocity measurements from large and small arteries of mice

With the growth of genetic engineering, mice have become increasingly common as models of human diseases, and this has stimulated the development of techniques to assess the murine cardiovascular system. Our group has developed nonimaging and dedicated Doppler techniques for measuring blood velocity in the large and small peripheral arteries of anesthetized mice. We translated technology originally designed for human vessels for use in smaller mouse vessels at higher heart rates by using higher ultrasonic frequencies, smaller transducers, and higher-speed signal processing. With these methods one can measure cardiac filling and ejection velocities, velocity pulse arrival times for determining pulse wave velocity, peripheral blood velocity and vessel wall motion waveforms, jet velocities for the calculation of the pressure drop across stenoses, and left main coronary velocity for the estimation of coronary flow reserve. These noninvasive methods are convenient and easy to apply, but care must be taken in interpreting measurements due to Doppler sample volume size and angle of incidence. Doppler methods have been used to characterize and evaluate numerous cardiovascular phenotypes in mice and have been particularly useful in evaluating the cardiac and vascular remodeling that occur following transverse aortic constriction. Although duplex ultrasonic echo-Doppler instruments are being applied to mice, dedicated Doppler systems are more suitable for some applications. The magnitudes and waveforms of blood velocities from both cardiac and peripheral sites are similar in mice and humans, such that much of what is learned using Doppler technology in mice may be translated back to humans.     

Noninvasive cardiovascular phenotyping in mice

With the growth of genetic engineering, mice have become common as models of human diseases, which in turn has stimulated the development of techniques to monitor and image the murine cardiovascular system. Invasive methods are often more quantitative, but noninvasive methods are preferred when measurements must be repeated serially on living animals during development or in response to pharmacological or surgical interventions. Because of the small size and high heart rates in mice, high spatial and temporal resolutions are required to preserve signal fidelity. Monitoring of body temperature and the electrocardiogram is essential when animals must be anesthetized for a measurement or other procedure. Several other groups have developed cardiovascular imaging modalities suitable for murine applications, and ultrasound is the most widely used. Our group has developed and applied high-resolution Doppler probes and signal processing for measuring blood velocity in the heart and peripheral vessels of anesthetized mice noninvasively. We can measure cardiac filling and ejection velocities as indices of systolic and diastolic ventricular function and for timing of cardiac events; velocity pulse arrival times for determining pulse-wave velocity and arterial stiffness; peripheral velocity waveforms as indices of arterial resistance, compliance, and wave reflections; stenotic velocities for estimation of pressure drop and detection of vorticity; and tail artery velocity for determining systolic and diastolic blood pressure using a pressure cuff. These noninvasive methods are convenient and easy to apply and have been used to detect and evaluate numerous cardiovascular phenotypes in mutant mice.     

缺血性心肌病的多模态心血管影像学方法进展

近年来,超声(ultrasound, US)、CT冠状动脉造影(CT coronary angiography, CCTA)、血管内超声(intravenous ultrasound,IVUS)、光学相干断层成像(optical coherence tomography, OCT)、多层螺旋CT成像(multi-slice computed tomography, MSCT)、单光子发射计算机断层成像(single-photon emission computed tomography, SPECT)、正电子发射计算机断层成像(positron emission computed tomography, PET)及心脏磁共振(cardiac magnetic resonance, CMR)等多种心血管成像技术能够提供与冠脉病变及心肌形态和功能相关的解剖学、血流动力学、细胞生物学及病理生理学等方面的重要信息,在缺血性心肌病的临床诊疗及预后评估中发挥着日益重要的作用。然而,如何恰当选择的多模态心血管影像技术是临床医师面临的一大难题。因此,本文在归纳总结主要心血管成像技术临床应用进展的基础上,对多模态心血管影像学在缺血性心肌病相关的冠脉解剖与斑块成像、心肌功能、心肌灌注及心肌活性显像中的临床应用价值进行综述。旨在帮助临床医师客观认识各种成像技术的优势与不足,从而制定最优化的选择方案。     

Measurement of Thermal Effects of Doppler Ultrasound: An In Vitro Study

Objective

Ultrasound is considered a safe imaging modality and is routinely applied during early pregnancy. However, reservations are expressed concerning the application of Doppler ultrasound in early pregnancy due to energy emission of the ultrasound probe and its conversion to heat. The objective of this study was to evaluate the thermal effects of emitted Doppler ultrasound of different ultrasound machines and probes by means of temperature increase of in-vitro test-media.

Methods

We investigated the energy-output of 5 vaginal and abdominal probes of 3 ultrasound machines (GE Healthcare, Siemens, Aloka). Two in-vitro test objects were developed at the Center for Medical Physics and Biomedical Engineering, Medical University Vienna (water bath and hydrogel bath). Temperature increase during Doppler ultrasound emission was measured via thermal sensors, which were placed inside the test objects or on the probes’ surface. Each probe was emitting for 5 minutes into the absorbing test object with 3 different TI/MI settings in Spectral Doppler mode.

Results

During water bath test, temperature increase varied between 0.1 and 1.0°C, depending on probe, setting and focus, and was found highest for spectral Doppler mode alone. Maximum temperature increase was found during the surface heating test, where values up to 2.4°C could be measured within 5 minutes of emission.

Conclusions

Activation of Doppler ultrasound in the waterbath model causes a significant increase of temperature within one minute. Thermally induced effects on the embryo cannot be excluded when using Doppler ultrasound in early pregnancy.     

Mesadenitis in children with acute abdominal pain syndrome: clinical and echographic parallels

The paper pools the experience of ultrasound assessment of acute mesadenitis in children with acute abdominal pain syndrome. It reviews the literature on its etiology, pathology, and diagnosis and treatment principles. B-mode and Doppler echograms made by general practice ultrasound diagnosticians are shown. The technique is demonstrated to be effective and of informative value in the early stages of diagnosis in the patient contingent in question.     

A Novel Application of Musculoskeletal Ultrasound Imaging

Ultrasound is an attractive modality for imaging muscle and tendon motion during dynamic tasks and can provide a complementary methodological approach for biomechanical studies in a clinical or laboratory setting. Towards this goal, methods for quantification of muscle kinematics from ultrasound imagery are being developed based on image processing. The temporal resolution of these methods is typically not sufficient for highly dynamic tasks, such as drop-landing. We propose a new approach that utilizes a Doppler method for quantifying muscle kinematics. We have developed a novel vector tissue Doppler imaging (vTDI) technique that can be used to measure musculoskeletal contraction velocity, strain and strain rate with sub-millisecond temporal resolution during dynamic activities using ultrasound. The goal of this preliminary study was to investigate the repeatability and potential applicability of the vTDI technique in measuring musculoskeletal velocities during a drop-landing task, in healthy subjects. The vTDI measurements can be performed concurrently with other biomechanical techniques, such as 3D motion capture for joint kinematics and kinetics, electromyography for timing of muscle activation and force plates for ground reaction force. Integration of these complementary techniques could lead to a better understanding of dynamic muscle function and dysfunction underlying the pathogenesis and pathophysiology of musculoskeletal disorders.     

Doppler ultrasound signal analysis based on the TMS320 signal processor

Doppler ultrasound is an established method for the study of haemodynamics. Considerable improvement in accuracy and resolution can be achieved by utilizing advanced data processing techniques. Such a system has been developed and used to assess the cardiac component of the Baroreceptor Reflex in adults and to examine cerebral blood flow in neonates.     

Thematic review series: patient-oriented research. Imaging atherosclerosis: state of the art

The ability to image obstructive arterial disease brought about a revolution in clinical cardiovascular care; the development of newer technologies that image arterial wall thicknesses, areas, volumes, and composition allows valid imaging of atherosclerosis for the first time. Development of noninvasive imaging of atherosclerosis has further led to a quantum shift in research in the field by enabling the study of asymptomatic populations and thus allowing investigators to focus on preclinical disease without the many biases associated with the study of symptomatic patients. These noninvasive investigations have broad implications for clinical care as well. Coronary angiography, computed tomographic (CT) imaging of coronary calcium, intravascular ultrasound, multidetector CT angiography, B mode ultrasound of the carotid arteries, and MRI of the carotid arteries all have unique strengths and weaknesses for imaging atherosclerosis. Certain of these techniques are extremely useful as outcome variables for clinical trials, and others are uniquely useful as predictors of the risk of cardiovascular disease. All are informative in one way or another with regard to the role of plaque remodeling and composition in disease causation. CT and MRI technology are advancing very rapidly, and research and clinical uses of these imaging modalities promise to further advance our understanding of atherosclerosis and its prevention.     

Surrogate markers for atherosclerotic disease

PURPOSE OF REVIEW: Novel treatment modalities for cardiovascular prevention are emerging rapidly. Since it is virtually impossible to evaluate all these new compounds in long-term trials using clinical end points, there is an urgent need for validated surrogate markers of atherosclerosis to save both time and costs. Over the last decade, the use of imaging markers has been widely introduced into drug-development strategies. Here we will discuss the most commonly used techniques. RECENT FINDINGS: Whereas both testing of endothelial function, assessed as flow-mediated dilation, and assessment of carotid intima-media thickness have been shown to predict future cardiovascular events, predominantly intima-media thickness has been used successfully as a surrogate marker in intervention studies. More recently, standardization of intravascular ultrasound has also enabled reproducible assessment of coronary atheroma volume. Multidetector computed tomography and electron-beam computed tomography have proven useful in providing quantitative information on plaque burden and coronary calcium content, respectively. Although cardiovascular magnetic resonance (CMR) is improving continuously, additional technical improvements will be mandatory before this technique can be implemented in multicenter clinical studies. SUMMARY: The imaging modalities reviewed here all provide specific information on either functionality or morphology of the vasculature. The value of carotid intima-media thickness for cardiovascular risk prediction has been studied most extensively. Whereas assessment of plaque burden using intravascular ultrasound appears to be the most direct way to quantify coronary changes, its predictive value for future cardiovascular events remains to be established. Awaiting further technical improvements, CMR is expected to provide the most valuable information for the evaluation of atherosclerosis in the near future.     

Non-invasive measurement of human fetal circulation using ultrasound: a new method.

We combined two ultrasound techniques to develop a safe, non-invasive, transcutaneous method of observing the circulation in the umbilical arteries and vein in the fetus. The umbilical cord can be located by standard echo ultrasound procedures, and this information can be used to direct a Doppler ultrasound beam on to the vessels in the cord. The signals can be heard through audio headphones or recorded on a tape recorded and spectrum-analysed. The method was successful in each of 20 patients examined, whose pregnancies ranged from 12 to 40 weeks'' gestational age, and was suitable for outpatient use. It should be useful in assessing such conditions as pre-eclampsia and intrauterine growth retardation.