Quantification of Ultrasound Correlation‐Based Flow Velocity Mapping and Edge Velocity Gradient Measurement

This study investigated the use of ultrasound speckle decorrelation‐ and correlation‐based lateral speckle‐tracking methods for transverse and longitudinal blood velocity profile measurement, respectively. By studying the blood velocity gradient at the vessel wall, vascular wall shear stress, which is important in vascular physiology as well as the pathophysiologic mechanisms of vascular diseases, can be obtained. Decorrelation‐based blood velocity profile measurement transverse to the flow direction is a novel approach, which provides advantages for vascular wall shear stress measurement over longitudinal blood velocity measurement methods. Blood flow velocity profiles are obtained from measurements of frame‐to‐frame decorrelation. In this research, both decorrelation and lateral speckle‐tracking flow estimation methods were compared with Poiseuille theory over physiologic flows ranging from 50 to 1000 mm/s. The decorrelation flow velocity measurement method demonstrated more accurate prediction of the flow velocity gradient at the wall edge than the correlation‐based lateral speckle‐tracking method. The novelty of this study is that speckle decorrelation‐based flow velocity measurements determine the blood velocity across a vessel. In addition, speckle decor‐relation‐based flow velocity measurements have higher axial spatial resolution than Doppler ultrasound measurements to enable more accurate measurement of blood velocity near a vessel wall and determine the physiologically important wall shear.     

Flux or speed? Examining speckle contrast imaging of vascular flows

Speckle contrast imaging enables rapid mapping of relative blood flow distributions using camera detection of back-scattered laser light. However, speckle derived flow measures deviate from direct measurements of erythrocyte speeds by 47 ± 15% (n = 13 mice) in vessels of various calibers. Alternatively, deviations with estimates of volumetric flux are on average 91 ± 43%. We highlight and attempt to alleviate this discrepancy by accounting for the effects of multiple dynamic scattering with speckle imaging of microfluidic channels of varying sizes and then with red blood cell (RBC) tracking correlated speckle imaging of vascular flows in the cerebral cortex. By revisiting the governing dynamic light scattering models, we test the ability to predict the degree of multiple dynamic scattering across vessels in order to correct for the observed discrepancies between relative RBC speeds and multi-exposure speckle imaging estimates of inverse correlation times. The analysis reveals that traditional speckle contrast imagery of vascular flows is neither a measure of volumetric flux nor particle speed, but rather the product of speed and vessel diameter. The corrected speckle estimates of the relative RBC speeds have an average 10 ± 3% deviation in vivo with those obtained from RBC tracking.OCIS codes: (170.0170) Medical optics and biotechnology, (110.6150) Speckle imaging     

Real-time high resolution laser speckle imaging of cerebral vascular changes in a rodent photothrombosis model

The study of hemodynamic and vascular changes following ischemic stroke is of great importance in the understanding of physiological and pathological processes during the thrombus formation. The photothrombosis model is preferred by researchers in stroke study for its minimal invasiveness, controllable infarct volume and lesion location. Nevertheless, there is a lack in high spatiotemporal resolution techniques for real time monitoring of cerebral blood flow (CBF) changes in 2D-profile. In this study, we implemented a microscopic laser speckle imaging (LSI) system to detect CBF and other vascular changes in the rodent model of photothrombotic stroke. Using a high resolution and high speed CCD (640 × 480 pixels, 60 fps), online image registration technique, and automatic parabolic curve fitting, we obtained real time CBF and blood velocity profile (BVP) changes in cortical vessels. Real time CBF and BVP monitoring has been shown to reveal details of vascular disturbances and the stages of blood coagulation in photothrombotic stroke. Moreover, LSI also provides information on additional parameters including vessel morphologic size, blood flow centerline velocity and CBF spatiotemporal fluctuations, which are very important for understanding the physiology and neurovascular pathology in the photothrombosis model.OCIS codes: (110.6150) Speckle imaging, (170.3880) Medical and biological imaging     

Accessing to arteriovenous blood flow dynamics response using combined laser speckle contrast imaging and skin optical clearing

Laser speckle contrast imaging (LSCI) shows a great potential for monitoring blood flow, but the spatial resolution suffers from the scattering of tissue. Here, we demonstrate the capability of a combination method of LSCI and skin optical clearing to describe in detail the dynamic response of cutaneous vasculature to vasoactive noradrenaline injection. Moreover, the superior resolution, contrast and sensitivity make it possible to rebuild arteries-veins separation and quantitatively assess the blood flow dynamical changes in terms of flow velocity and vascular diameter at single artery or vein level.OCIS codes: (120.6150) Speckle imaging, (290.0290) Scattering, (170.1470) Blood or tissue constituent monitoring, (150.1135) Algorithms     

握力大小对留置PICC肿瘤患者腋静脉血流动力学的影响

目的 探讨肿瘤患者置入PICC导管后握力大小对上肢静脉血流动力学的影响,为握球锻炼提供科学依据。方法 采用前瞻性临床观察的研究方法,选取北京市某三级甲等医院2018年7-8月收治的40例置入PICC导管的肿瘤患者,采用自身前后对照的方法使用握力器进行握力,并在超声监测下观察不同握力大小对静脉血管直径、血流速度和血管压力的影响。结果 患者在静息状态下静脉血流的血管直径为（4.18±0.83）mm,血流峰速度为（12.39±3.17）cm/s,静脉对血管壁的压力为（0.06±0.03）mmHg,不同握力大小下血管直径比较差异无统计学意义（P>0.05）、血流峰速度和血管压力比较有统计学意义（P<0.05）,所有不同握力大小下的静脉血流动力学变化均有统计学意义,其中使用80%最大握力、90%最大握力、100%最大握力握力后静脉血流峰速度和静脉血管压力与静息状态下比较差异有统计学意义（P<0.05）。结论 握力可有效增加静脉血流速度,加大静脉对血管壁的压力,未引起患者不适,可用于指导临床上置入PICC导管的肿瘤患者进行功能锻炼。80%最大握力~100%最大握力范围内的握力为患者功能锻炼时最适宜的握力大小,可用于临床推广使用。     

彩色多普勒超声检测移植肝血流变化预测胆道并发症发生的可行性

目的探讨肝移植术后彩色多普勒超声检测血流变化预测胆道发生并发症的可行性。 方法超声观察125例肝移植患者术后肝脏动静脉血流变化，主要观测血管内径（D），峰值流速（PS），阻力指数（RI），时间平均流速（TAV）。 结果肝移植术后，发生胆道并发症者49例，各项指标分别与术后未发现并发症的对照组59例相比：（1）术后30d内肝动脉PS减低，RI增高，2项指标差异均有显著性意义；（2）术后15d内并发症组肝静脉D较细，TAV减低，差异均有显著性意义；（3）两组间门静脉TAV差异无显著性意义，但并发症组中，单纯肝动脉供血不足者13例，门静脉TAV增高，与对照组相比，差异有非常显著性意义；单纯出现排异反应者8例，门静脉TAV减低，与对照组相比，差异有显著性意义。 结论超声预测肝移植术后肝动脉供血不足及排异反应导致的胆道并发症是可行的。     

Quantifying the vascular response to ischemia with speckle variance optical coherence tomography

Longitudinal monitoring techniques for preclinical models of vascular remodeling are critical to the development of new therapies for pathological conditions such as ischemia and cancer. In models of skeletal muscle ischemia in particular, there is a lack of quantitative, non-invasive and long term assessment of vessel morphology. Here, we have applied speckle variance optical coherence tomography (OCT) methods to quantitatively assess vascular remodeling and growth in a mouse model of peripheral arterial disease. This approach was validated on two different mouse strains known to have disparate rates and abilities of recovering following induction of hind limb ischemia. These results establish the potential for speckle variance OCT as a tool for quantitative, preclinical screening of pro- and anti-angiogenic therapies.OCIS codes: (170.4500) Optical coherence tomography, (170.3880) Medical and biological imaging, (170.2655) Functional monitoring and imaging, (100.2960) Image analysis, (110.6150) Speckle imaging     

On the potential of the Lagrangian speckle model estimator to characterize atherosclerotic plaques in endovascular elastography: in vitro experiments using an excised human carotid artery

Endovascular ultrasound (US) elastography (EVE) was introduced to supplement endovascular US echograms in the assessment of vessel lesions and for endovascular therapy planning. Indeed, changes in the vascular tissue stiffness are characteristic of vessel wall pathologies and EVE appears as a very appropriate imaging technique to outline the elastic properties of vessel walls. Recently, a model-based approach was proposed to assess tissue motion in EVE. It specifically consists of a nonlinear minimization algorithm that was adapted to speckle motion estimation. Regarding the theoretical framework, such an approach considers the speckle as a material property; this assumption then led to the derivation of the optical flow equations, which were suitably combined with the Lagrangian speckle model estimator to provide the full 2-D polar strain tensor. In this study, the proposed algorithm was validated in vitro using a fresh excised human carotid artery. The experimental setup consisted of a cardiovascular imaging system (CVIS) US scanner, working with a 30-MHz mechanical rotating single-element transducer, a digital oscilloscope and a pressuring system. A sequence of radiofrequency (RF) images was collected while incrementally adjusting the intraluminal static pressure steps. The results showed the potential of this 2-D algorithm to characterize and to distinguish an atherosclerotic plaque from the normal vascular tissue. Namely, the geometry as well as some mechanical characteristics of the detected plaque were in good agreement with histology. The results also suggested that there might exist a range of intraluminal pressures for which plaque detectability is optimal.     

Non-invasive Assessment by B-Mode Ultrasound of Arterial Pulse Wave Intensity and Its Reduction During Ventricular Dysfunction

Arterial pulse waves contain clinically useful information about cardiac performance, arterial stiffness and vessel tone. Here we describe a novel method for non-invasively assessing wave properties, based on measuring changes in blood flow velocity and arterial wall diameter during the cardiac cycle. Velocity and diameter were determined by tracking speckles in successive B-mode images acquired with an ultrafast scanner and plane-wave transmission. Blood speckle was separated from tissue by singular value decomposition and processed to correct biases in ultrasound imaging velocimetry. Results obtained in the rabbit aorta were compared with a conventional analysis based on blood velocity and pressure, employing measurements obtained with a clinical intra-arterial catheter system. This system had a poorer frequency response and greater lags but the pattern of net forward-traveling and backward-traveling waves was consistent between the two methods. Errors in wave speed were also similar in magnitude, and comparable reductions in wave intensity and delays in wave arrival were detected during ventricular dysfunction. The non-invasive method was applied to the carotid artery of a healthy human participant and gave a wave speed and patterns of wave intensity consistent with earlier measurements. The new system may have clinical utility in screening for heart failure.     

Hemodynamic and morphological vasculature response to a burn monitored using a combined dual-wavelength laser speckle and optical microangiography imaging system

A multi-functional imaging system capable of determining relative changes in blood flow, hemoglobin concentration, and morphological features of the blood vasculature is demonstrated. The system combines two non-invasive imaging techniques, a dual-wavelength laser speckle contrast imaging (2-LSI) and an optical microangiography (OMAG) system. 2-LSI is used to monitor the changes in the dynamic blood flow and the changes in the concentration of oxygenated (HbO), deoxygenated (Hb) and total hemoglobin (HbT). The OMAG system is used to acquire high resolution images of the functional blood vessel network. The vessel area density (VAD) is used to quantify the blood vessel network morphology, specifically the capillary recruitment. The proposed multi-functional system is employed to assess the blood perfusion status from a mouse pinna before and immediately after a burn injury. To our knowledge, this is the first non-invasive, non-contact and multifunctional imaging modality that can simultaneously measure variations of several blood perfusion parameters.     

彩超诊断腓动脉末支血管的研究

目的　对２０ 例腓动脉末支血管作血流动力学检测。方法　被检查者取侧卧位,下肢髋、膝关节弯曲呈放松状态,探头置在距膝关节约６ ｃｍ 处,声像图显示腓骨和周围诸肌。观察血管的内径及彩色血流的充盈情况等。结果　管径为１－３３±０－１３ ｍ ｍ ,收缩期峰值流速为１５－６±１１－６ ｃｍ／ｓ,阻力指数为０－９ ±０－０７ ,平均流速为８－６ ±３－１６ ｃｍ／ｓ。结论　本文的腓动脉末支血管的收缩期峰值流速与文献报道的胫后动脉收缩期峰值流速近似,作者在检查该血管时发现大多数为单相波型,很少为三相波型,认为接近骨面区的动脉末支血管受肌肉阻力少或无。彩超可较准确地评估下肢动脉的功能信息。     

B—flow超声显像技术诊断精索静脉曲张

目的探讨B—flow超声显像技术对精索静脉曲张的诊断价值。方法将30例彩色多普勒超声已经诊断精索静脉曲张的患者按临床症状分为临床型和亚临床型，分别进行B—flow显像，观察反流情况，测量部分患者的反流时间与反流速度，并进行统计学分析。结果临床型和亚临床型精索静脉曲张两组之间静脉内径有明显差异fP〈0．01）。CDFI和B—flow对于临床型组反流阳性检出率之间存在明显差异（P〈0．05），而两者对于亚临床型组阳性检出率之间存在明显差异（P〈0．01）两组患者在反流时间与反流速度之间均存在显著差异（P〈0．01）（P〈0．05）结论B—flow显像技术能更好地诊断精索静脉曲张，特别能提高亚临床精索静脉曲张反流阳性检出率，对于早期临床症状不明显的亚临床型精索静脉曲张诊断有重要意义。     

大鼠脊髓急性损伤后血流动力学变化的光学监测

目的 观察脊髓损伤后血流动力学的变化,探讨脊髓损伤的血流动力学机制.方法 雌性SD大鼠20只,分为对照组和损伤组,每组10只.Nystrom法制造大鼠脊髓(T10-11)中度压迫性损伤模型.利用激光散斑成像系统监测大鼠脊髓损伤后第10分钟、30分钟、1小时、2小时、3小时、6小时背部血管内的血流速度和血流量以及血管管径的变化.结果 对照组大鼠各时间点血管内的血流速度、血流量以及血管管径均较稳定,无明显波动.损伤组大鼠各项指标均低于对照组.结论 激光散斑成像技术可以用于监测脊髓血流动力学的变化;急性脊髓损伤后血流动力学的变化提示进行性的"创伤后缺血",静脉回流受阻可能是引起创伤后缺血的一个重要因素.     

Shunt Flow Evaluation in Congenital Heart Disease Based on Two-Dimensional Speckle Tracking

High-frame-rate ultrasound speckle tracking was used for quantification of peak velocity in shunt flows resulting from septal defects in congenital heart disease. In a duplex acquisition scheme implemented on a research scanner, unfocused transmit beams and full parallel receive beamforming were used to achieve a frame rate of 107 frames/s for full field-of-view flow images with high accuracy, while also ensuring high-quality focused B-mode tissue imaging. The setup was evaluated in vivo for neonates with atrial and ventricular septal defects. The shunt position was automatically tracked in B-mode images and further used in blood speckle tracking to obtain calibrated shunt flow velocities throughout the cardiac cycle. Validation toward color flow imaging and pulsed wave Doppler with manual angle correction indicated that blood speckle tracking could provide accurate estimates of shunt flow velocities. The approach was less biased by clutter filtering compared with color flow imaging and was able to provide velocity estimates beyond the Nyquist range. Possible placements of sample volumes (and angle corrections) for conventional Doppler resulted in a peak shunt velocity variations of 0.49–0.56 m/s for the ventricular septal defect of patient 1 and 0.38–0.58 m/s for the atrial septal defect of patient 2. In comparison, the peak velocities found from speckle tracking were 0.77 and 0.33 m/s for patients 1 and 2, respectively. Results indicated that complex intraventricular flow velocity patterns could be quantified using high-frame-rate speckle tracking of both blood and tissue movement. This could potentially help increase diagnostic accuracy and decrease inter-observer variability when measuring peak velocity in shunt flows.     

Reproducibility of ultrasonic fetal volume blood flow measurements

The intraobserver reproducibility of ultrasonic volume blood flow measurements in the human fetus was evaluated in this study. A new approach, simultaneous measurement of the vessel diameter and the flow velocity with a pulsed-wave Doppler ultrasound synchronized with a real-time ultrasound phase-locked echo-tracking system, was used to estimate volume blood flow (VBF) in the fetal descending aorta. Measurements were performed in a longitudinal study on 20 normally grown fetuses. Intraobserver reproducibility of repeated estimations of mean blood flow velocities throughout gestation was very good, with high values of intraclass correlation coefficient (IntraCC 0·80–0·91) and low values of coefficient of variation (CV 4–11%). The IntraCC of repeated vessel diameter measurements throughout gestation was low (0·30–0·68), whereas the values of CV were acceptable (< 12%), with the exception of the period between 140 and 167 gestational days (CV > 12%). The lower reproducibility of vessel diameter measurement contributed directly to the relatively low reproducibility of VBF estimations overall (IntraCC 0·25–0·70; CV 17–28%), as these are calculated from a formula using both flow velocity and vessel diameter. Nevertheless, the synchronized approach gives absolute values of vessel diameter, flow velocity and VBF comparable with values reported in the human fetus previously. The new method provides, by taking the vessel wall pulsations into consideration and by measuring diameter and velocity simultaneously, a more complete information on fetal haemodynamics and fetal physiology.     

In Vivo Lateral Blood Flow Velocity Measurement Using Speckle Size Estimation

In previous studies, we proposed blood measurement using speckle size estimation, which estimates the lateral component of blood flow within a single image frame based on the observation that the speckle pattern corresponding to blood reflectors (typically red blood cells) stretches (i.e., is “smeared”) if blood flow is in the same direction as the electronically controlled transducer line selection in a 2-D image. In this observational study, the clinical viability of ultrasound blood flow velocity measurement using speckle size estimation was investigated and compared with that of conventional spectral Doppler of carotid artery blood flow data collected from human patients in vivo. Ten patients (six male, four female) were recruited. Right carotid artery blood flow data were collected in an interleaved fashion (alternating Doppler and B-mode A-lines) with an Antares Ultrasound Imaging System and transferred to a PC via the Axius Ultrasound Research Interface. The scanning velocity was 77 cm/s, and a 4-s interval of flow data were collected from each subject to cover three to five complete cardiac cycles. Conventional spectral Doppler data were collected simultaneously to compare with estimates made by speckle size estimation. The results indicate that the peak systolic velocities measured with the two methods are comparable (within ±10%) if the scan velocity is greater than or equal to the flow velocity. When scan velocity is slower than peak systolic velocity, the speckle stretch method asymptotes to the scan velocity. Thus, the speckle stretch method is able to accurately measure pure lateral flow, which conventional Doppler cannot do. In addition, an initial comparison of the speckle size estimation and color Doppler methods with respect to computational complexity and data acquisition time indicated potential time savings in blood flow velocity estimation using speckle size estimation. Further studies are needed for calculation of the speckle stretch method across a field of view and combination with an appropriate axial flow estimator.     

速度向量成像评价冠心病患者颈动脉粥样斑块力学特性的临床研究

目的 探讨颈动脉正常和斑块部佗、硬斑块和软斑块及斑块的肩部和纤维帽顶部速度、应变及应变率变化规律.方法对86例冠心病伴颈动脉粥样斑块患者和50例正常人双侧颈动脉进行高频超声检查,检测颈动脉内膜-中层厚度(IMT);应用速度向量成像(VVI)斑点追踪技术检测颈动脉的运动速度、应变、应变率,并分组进行分析.结果冠心病组颈动脉IMT高于正常组,差异有统计学意义(P＜0.05);正常对照组颈动脉收缩期径向最大运动速度高于冠心病颈动脉无斑块部位的测值,差异有统计学意义(P＜0.05);软斑块收缩期最大运动速度、最大应变率高于硬斑块组,差异有统计学意义(P＜0.001或P＜0.05);颈动脉斑块肩部收缩期最大运动速度、应变率高于斑块纤维帽顶部.差异有统计学意义(P＜0.05或P＜0.001).结论 VVI技术可早期检测血管壁的弹性度,早期检测颈动脉荆样硬化及颈动脉粥样硬化斑块部位内膜运动的机械不一致性和不同部位的力学指标差别,有可能作为动脉粥样硬化不稳定斑块的初查和量化评价指标.     

Measurement of the total retinal blood flow using dual beam Fourier-domain Doppler optical coherence tomography with orthogonal detection planes

We present a system capable of measuring the total retinal blood flow using a combination of dual beam Fourier-domain Doppler optical coherence tomography with orthogonal detection planes and a fundus camera-based retinal vessel analyzer. Our results show a high degree of conformity of venous and arterial flows, which corroborates the validity of the measurements. In accordance with Murray’s law, the log-log regression coefficient between vessel diameter and blood flow was found to be ~3. The blood’s velocity scaled linearly with the vessel diameter at higher diameters (> 60 µm), but showed a clear divergence from the linear dependence at lower diameters. Good agreement with literature data and the large range and high measurement sensitivity point to a high potential for further investigations.OCIS codes: (170.0110) Imaging systems, (280.2490) Flow diagnostics, (170.2655) Functional monitoring and imaging, (170.4460) Ophthalmic optics and devices, (170.4500) Optical coherence tomography     

能量多普勒显像与彩色多普勒显像显示血管内径准确性的实验比较

目的：比较能量多普勒显像（ＰＤＩ）和彩色多普勒血流显像（ＣＤＦＩ）显示离体模拟血流血管内边界的准确性。方法：在０．４ｍｍ、３ｍｍ和８ｍｍ内径的硅胶管中模拟低速血流,分别用二维超声（２ＤＵＳ）、ＣＤＦＩ及ＰＤＩ进行显像,准确测量各显像模式中各血管的血管内径或彩色血流直径。结果：①、２ＤＵＳ测量的各种血管内径与实际内径均无明显差别（Ｐ＞０．０５）;②、ＰＤＩ在０．４ｍｍ内径血管的血流显示中,ＰＤＩ血流直径比２ＤＵＳ的血管内径大２．４倍（Ｐ＜０．０１）;在３ｍｍ和８ｍｍ内径血管,ＰＤＩ血流直径与２ＤＵＳ的血管内径无明显差异（Ｐ＞０．０５）;③、在三种内径血管显示中,ＣＤＦＩ血流直径均明显大小ＰＤＩ血流直径（Ｐ＜０．０１）,且血流前后径明显大于血流横径（Ｐ＜０．０１）。结论：ＰＤＩ用血流直径代表血管内径的准确性明显高于ＣＤＦＩ,尤其在较粗的血管中,ＰＤＩ血流直径能准确反映血管内径。     

Optical microangiography of retina and choroid and measurement of total retinal blood flow in mice

We present a novel application of optical microangiography (OMAG) imaging technique for visualization of depth-resolved vascular network within retina and choroid as well as measurement of total retinal blood flow in mice. A fast speed spectral domain OCT imaging system at 820nm with a line scan rate of 140 kHz was developed to image the posterior segment of eyes in mice. By applying an OMAG algorithm to extract the moving blood flow signals out of the background tissue, we are able to provide true capillary level imaging of the retinal and choroidal vasculature. The microvascular patterns within different retinal layers are presented. An en face Doppler OCT approach [Srinivasan et al., Opt Express 18, 2477 (2010)] was adopted for retinal blood flow measurement. The flow is calculated by integrating the axial blood flow velocity over the vessel area measured in an en face plane without knowing the blood vessel angle. Total retinal blood flow can be measured from both retinal arteries and veins. The results indicate that OMAG has the potential for qualitative and quantitative evaluation of the microcirculation in posterior eye compartments in mouse models of retinopathy and neovascularization.OCIS codes: (170.4500) Optical coherence tomography, (170.3880) Medical and biological imaging