Conventional Doppler Method Research Articles

Rotational Doppler effect of vortex beam with frequency-shifted laser feedback

We propose and demonstrate a rotational Doppler measurement system based on frequency-shifted laser feedback interferometry. The system utilizes a vortex beam as the probe, which is modulated by the target and then reflected back into the laser cavity. Compared with the conventional rotational Doppler methods, this approach effectively enhances the amplitude of the generated beat signal through intra-cavity interference between the echo signal and local oscillator. Consequently, it improves sensitivity in weak-signal detection and enables measurement with low probe-beam power. A signal to noise (SNR) enhancement of over 15 dB was observed compare to the Mach-Zehnder structure. This system inherits the advantages of rotational Doppler effect, possessing the capacity to get a frequency proportional to the topological charge of vortex. Experimental validation demonstrates accurate measurement of rotational angle and velocity, with the ability to distinguish rotational direction through heterodyne detection. For vortices with topological charge ranging from 18 to 21 and rotational speeds in range of 150 to 600 revolutions per minute (RPM), the measurement error is within ±3 RPM. Overall, the proposed system possesses high sensitivity to echo signal, low photon consumption, and direction information availability, which provides a new approach for optimizing the rotational Doppler effect in practical applications.

Analysis for Improvement of Doppler Tomography Imaging of Objects Scattering Continuous Ultrasonic Waves

The paper describes an innovative ultrasound imaging method called Doppler Tomography (DT), otherwise known as Continuous Wave Ultrasonic Tomography (CWUT). Thanks to this method, it is possible to image the tissue cross-section in vivo using a simple two-transducer ultrasonic probe and using the Doppler effect. It should be noted that DT significantly differs from the conventional ultrasound Doppler method of measuring blood flow velocity. The main difference is that when measuring blood flow, we receive information with an image of the velocity distribution in a given blood vessel (Nowicki, 1995), while DT allows us to obtain a cross-sectional image of stationary tissue structure. In the conventional method, the probe remains stationary, while in the DT method, the probe moves and the examined tissue remains stationary. This paper presents a method of image reconstruction using the DT method. First, the basic principle of correlation of generated Doppler frequencies with the location of inclusions from which they originate is explained. Then the exact process and algorithm in this method are presented. Finally, the impact of several key parameters on imaging quality is examined. As a result, the conclusions of the research allow to improve the image reconstruction process using the DT method.

TELARŞLI PUBERTE PREKOKS HASTALARINDA VASKÜLARİTENİN DOPPLER ULTRASONOGRAFI YÖNTEMLERİ İLE DEĞERLENDİRİLMESİ

OBJECTIVE: The aim of this study is to investigate the correlation between breast vascularity level and Tanner staging in the evaluation of thelarche, and to compare Doppler methods for demonstrating vascularity.MATERIAL AND METHODS: Girls aged 6–10 who were referred to the radiology clinic with a complaint of breast swelling and prediagnosed with precocious puberty between October and December 2017 were included in the study. Breast ultrasonography (US) and color doppler ultrasonography (CDUS) examinations were performed on all participants. Age, Follicle Stimulating Hormone (FSH), Luteinizing Hormone (LH), Estradiol (E2), thelarche stage, both breast volumes were recorded for all participants. Vascular scores were measured for both breasts using imaging modalities such as color doppler (CD), Power US (PD), and superb microvascular imaging (SMI).RESULTS: We included 116 girls and 213 thelarche breasts in the study. A significant correlation was found between the depth and transverse and longitudinal diameter for each breast and breast volume and Tanner stages (rs = 0.762, rs = 0.830, rs = 0.774 rs = 0.824, respectively; p < 0.001). Although the highest correlation between Doppler methods was found in PD (PD rs =0.68, CD rs =: 0.61, SMI rs =:0.61, p<0.001), the methods did not have any superiority over each other (p>0.05). Vascularization with SMI was demonstrated in 30 of 65 breasts for which vascularization could not be demonstrated with power Doppler. Among these 30 cases, 90% (n = 27) were Tanner stage I and II.CONCLUSIONS: In conclusion, although SMI is as successful as conventional Doppler methods in the evaluation of thelarche vascularity, it can provide more data in some cases.

Quantitative Ultrasound: An Emerging Technology for Detecting, Diagnosing, Imaging, Evaluating, and Monitoring Disease.

Ultrasound has been a popular clinical imaging modality for decades. It is a well-established means of displaying the macroscopic anatomy of soft-tissue structures. While conventional ultrasound methods, i.e., B-mode and Doppler methods, are well proven and continue to advance technically in many ways, e.g., by extending into higher frequencies and taking advantage of harmonic phenomena in tissues, fundamentally new so-called quantitative ultrasound (QUS) technologies also are emerging and offer exciting promise for making significant improvements in clinical imaging and characterization of disease. These emerging quantitative methods include spectrum analysis, image statistics, elasticity imaging, contrast-agent methods, and flow-detection and -measurement techniques. Each provides independent information. When used alone, each can provide clinically valuable imaging capabilities; when combined with each other, their capabilities may be more powerful in many applications. Furthermore, all can be used fused with other imaging modalities, such as computed tomography (CT), magnetic-resonance (MR), positron-emission-tomography (PET), or single-photon emission computerized tomography (SPECT) imaging, to offer possibly even greater improvements in detecting, diagnosing, imaging, evaluating, and monitoring disease. This chapter focuses on QUS methods that are based on spectrum analysis and image statistics.

A Narrative Review of Clinical Applications of Systolic Time Intervals

Systolic time interval (STI) estimation is an established noninvasive method for the quantifiable assessment of left ventricular (LV) performance in well-being and disease states; it stays valuable for clinical application and forms no burden to the subjects. This manuscript reviews the potential clinical applications and prognostic value of STI for the assessment of LV systolic function in cardiovascular disease (CVD). STIs could be obtained by several noninvasive imaging modalities such as transthoracic echocardiography, tissue Doppler imaging M-mode echocardiography, conventional echocardiography, and so on. In view of that, a literature review for studies reporting the clinical applications of STI in assessing LV systolic function among CVD patients was carried out using PubMed search. Accordingly, the current review describes how STI can be measured; reliability of cardiac time interval measurement in patients with CVD and its role in a clinical setting. With the advent of modern techniques, STI could be easily measured in a clinical setting. Likewise, STI parameter, particularly preejection period and LV ejection time ratio (PEP/LVET), has got the highest degree of correlation with LV ejection fraction (LVEF) in assessing LV performance. Furthermore, reproducibility of systolic ejection time (SET) achieved by the TDI M-mode method is outstanding and better when compared with the reproducibility of SET obtained by the conventional pulsed Doppler method. Furthermore, prolonged SET is independently related with enhanced outcomes among heart failure with reduced EF (HFrEF, i.e., EF ≤40%) but not HF with preserved EF (HFpEF, i.e., EF >40%) patients, indicating that stabilizing SET would be helpful in the case of systolic dysfunction. Clinically, tissue Doppler-derived time intervals could be beneficial to analyze abnormal cases in comparison with other invasive and noninvasive methods of ventricular function examination. Furthermore, phonoelectrocardiography-derived STI parameters, particularly electromechanical activation time-to-LVET ratio, may have a significant role in the diagnostic approach of heart failure (HF) in patients with undifferentiated dyspnea. In addition, in HF patients, PEP/LVET of >0.43 helps to detect LVEF <35% by pulsed Doppler echocardiography. Moreover, LVET continues to be an independent predictor of incident HF and provides incremental prognostic value on the future HF risk and death but not myocardial infarction. In conclusion, STI measurement could be useful, particularly in identifying LVEF <35% in the case of refractory HF patients. This could be beneficial in the selection of patients requiring cardiac resynchronization, specifically when accurate LVEF evaluation by echocardiography proves challenging in atrial fibrillation or if the evaluation is done by a trainee echocardiographer. Furthermore, the cardiac time intervals including SET can be acquired irrespective of rhythm. Good image quality is required for the assessment of LVEF. In contrast, evaluation of SET could be useful in the case of echocardiograms with poor quality images. As a final point, the present review suggests using an echocardiographic parameter like STIs to procure additional information regarding the risk of mortality in patients with HFrEF along with LVEF measurement.

Blood flow image by multi-angle composite ultrasonic Doppler vector

Precise measurement of blood flow is of vital importance in studying the formation of thrombus and atherosclerotic plaque. However, conventional color Doppler methods are limited to obtaining the velocity component along the ultrasound beam and have poor accuracy. Several Doppler flow imaging methods based on the plane wave emission can estimate the blood velocity vectors and visualize hemodynamic parameters, which provide more detailed blood flow information and effectively improve the capability of clinical diagnosis treatment. Considering the low accuracy of the Doppler flow methods for measuring velocity in complex flow fields, an optimization technique is used to improve the imaging quality and the accuracy of velocity estimation. In this study we propose a modified vector Doppler method through combining multi-angle compound technique, to reconstruct blood velocity vectors of carotid bifurcations obtained from 3D printing. Since the multi-angle compound technology can effectively improve the quality of imaging, this technology is applied to Doppler imaging to achieve high-accuracy velocity estimation. It can significantly reduce the velocity estimation errors. Comparing the velocity estimation accuracy of different angle compound numbers (<i>n</i> = 1, 3, 5, and 7) in the simulation, it is found that the accuracy of velocity estimation increases with angle compound increasing. Beside, the 5-angle compound method is more robust for velocity estimation and can obtain higher frames. The experiments were carried out using a programmable ultrasonic array system and a high-frequency linear array transducer L12-5c with a central frequency of 8.125 MHz. The sample rate is set to be 31.25 MHz. The imaging results of carotid bifurcation also show that the vector Doppler based on 5-angle compound can obtain a clear image of intravascular vector flow, which is beneficial to the identifying of complex flow state, and realize intravascular dynamic imaging. Especially, it can capture the vortex phenomenon in the blood stream. The quantitative results indicate that this method significantly reduces the error between the flow calculation results and the reference results, making the estimation results more accurate. In conclusion, the vector Doppler method based on multi-angle compound has the good performance of visualizing complex blood flow and calculating hemodynamic parameters. It also provides the reference for the diagnosis of cardiovascular disease and the research of flow imaging methods.

Emerging Technology: Ultrasound Vector Flow Imaging—A Novel Approach to Arterial Hemodynamic Quantification

Accurate, reliable, and easily obtainable quantification of peripheral arterial hemodynamic states has long been a holy grail of vascular ultrasound. While conventional Doppler modalities have been relied upon for decades to provide velocity, directionality, and flow volume data for integration into patient management schema, they carry limitations in accurately and reproducibly quantifying complex arterial hemodynamic patterns. Advances in ultrasound imaging architecture, such as virtual beamforming, integration of “big data” capabilities, and the use of enhanced digital signal processing methods have opened the door for a novel approach to arterial hemodynamic mapping and quantification—ultrasound vector flow imaging (VFI). This article presents an overview of the technological underpinnings of VFI, compares it with conventional pulsed wave and color Doppler methods, and describes the potential clinical benefits of this emerging vascular ultrasound modality.

Blood speckle imaging: A new echocardiographic approach to study fluid dynamics in congenital heart disease

IntroductionBlood speckle imaging (BSI) is a new speckle-tracking-based technique for blood flow study. Flows assessment is particularly challenging in Congenital heart diseases (CHDs), where a profound distortion in cardiac anatomy gives reason of alteration in fluid mechanics. Up until now doppler methods were the only ones used for the analysis of fluid. Overcoming standard Doppler limits, BSI is becoming a promising new approach for the study of fluid dynamics.The aim of the study was to assess fluid-dynamics of different CHDs by using BSI. Methods and resultsTen children (7 with suspected CHDs and 3 controls) were enrolled for the purpose between January and June 2019. All of them underwent a complete 2D and Doppler echocardiographic assessment plus a further BSI study. We studied: one complex transposition of great arteries, one coarctation of aorta, one tetralogy of Fallot, one complete atrio-ventricular septal defect, one suspicious flow in pulmonary artery, one aortic stenosis, one hypertrophic cardiomyopathy and three normal controls. ConclusionCompared to conventional Doppler methods, BSI was able to better describe fluid dynamics and hemodynamics of these CHDs by showing laminar and turbulent flows and vortices. In our experience, it helped to define the diagnosis and, in some cases, drove the management.

A randomized cross-over trial in patients suspected of PAD on diagnostic accuracy of ankle-brachial index by Doppler-based versus four-point oscillometry based measurements.

Background: For diagnosis of peripheral arterial occlusive disease (PAD), a Doppler-based ankle-brachial-index (dABI) is recommended as the first non-invasive measurement. Due to limitations of dABI, oscillometry might be used as an alternative. The aim of our study was to investigate whether a semi-automatic, four-point oscillometric device provides comparable diagnostic accuracy. Furthermore, time requirements and patient preferences were evaluated. Patients and methods: 286 patients were recruited for the study; 140 without and 146 with PAD. The Doppler-based (dABI) and oscillometric (oABI and pulse wave index- PWI) measurements were performed on the same day in a randomized cross-over design. Specificity and sensitivity against verified PAD diagnosis were computed and compared by McNemar tests. ROC analyses were performed and areas under the curve were compared by non-parametric methods. Results: oABI had significantly lower sensitivity (65.8%, 95% CI: 59.2%-71.9%) compared to dABI (87.3%, CI: 81.9-91.3%) but significantly higher specificity (79.7%, 74.7-83.9% vs. 67.0%, 61.3-72.2%). PWI had a comparable sensitivity to dABI. The combination of oABI and PWI had the highest sensitivity (88.8%, 85.7-91.4%). ROC analysis revealed that PWI had the largest area under the curve, but no significant differences between oABI and dABI were observed. Time requirement for oABI was significantly shorter by about 5min and significantly more patients would prefer oABI for future testing. Conclusions: Semi-automatic oABI measurements using the AngER-device provide comparable diagnostic results to the conventional Doppler method while PWI performed best. The time saved by oscillometry could be important, especially in high volume centers and epidemiologic studies.

Big steps in advances of doppler ultrasound

Doppler Ultrasound is clinically important for evaluation of various hepatic vascular disease as well as hepatic vessel evaluation after liver transplantation. However, there are some limitations in conventional Doppler methods as follows: 1) time consuming and labor intensive and 2) limited slow flow sensitivity. There are two recently advanced Doppler signal-processing methods (i.e., UltraFast and superb microvascular imaging), which overcome those limitations. UltraFast Doppler ultrasound, which emerged with the advent of massive parallel computing (or processing) capabilities, transmits several tilted plane waves into the medium and coherently sums the backscattered echoes to reconstruct US images, leading to a marked increase in the frame rate, while conventional ultrasound imaging involves sequential medium insonification via focused beams and successive image reconstruction. A stored UltraFast Doppler clip contains information on both spectral analysis and color-coded flow imaging and could be retrospectively evaluated quantitative analysis, because UltraFast ultrasound has high spatio-temporal resolution. Superb microvascular imaging (SMI, Cannon Medical Systems Corporation, Tochigi, Japan) uses a different kind of adaptive wall filter, which could minimize the flash artifact and increased sensitivity to slow flow and improve the signal detection of flow from small vessels. Therefore, in clinical practice, UltraFast Doppler can be performed by anyone. If the exam protocol such as acquisition of clip by less experienced sonographer and evaluation by retrospective wave reconstruction by specialist can be established, efficient work force management can be possible. Superb Microvascular imaging can distinguish very slow portal flow by portal hyper tension and so forth from thrombus. Thrombus can be evaluated with almost the same resolution as CT. The weak flow of a small hepatic artery hiding by vigorous flow of portal vein after liver transplantation can be also distinguished. In conclusion, smart application of recent advanced Doppler technique will help comprehensive assessment of hepatic vascular abnormalities.

Demonstration of a Speckle Based Sensing with Pulse-Doppler Radar for Vibration Detection.

In previous works, an optical technique for extraction and separation of remote static vibrations has been demonstrated. In this paper, we will describe an approach in which RF speckle movement is used to extract remote vibrations of a static target. The use of conventional radar Doppler methods is not suitable for detecting vibrations of static targets. In addition, the speckle method has an important advantage, in that it is able to detect vibrations at far greater distances than what is normally detected in classical optical methods. The experiment described in this paper was done using a motorized vehicle, which engine was turned on and off. The results showed that the system was able to distinguish between the different engine states, and in addition, was able to determine the vibration frequency of the engine. The first step towards real time detection of human vital signs using RF speckle patterns is presented.

Complex regression Doppler optical coherence tomography.

.We introduce a new method to measure Doppler shifts more accurately and extend the dynamic range of Doppler optical coherence tomography (OCT). The two-point estimate of the conventional Doppler method is replaced with a regression that is applied to high-density B-scans in polar coordinates. We built a high-speed OCT system using a 1.68-MHz Fourier domain mode locked laser to acquire high-density B-scans (16,000 A-lines) at high enough frame rates () to accurately capture the dynamics of the beating embryonic heart. Flow phantom experiments confirm that the complex regression lowers the minimum detectable velocity from to , whereas the maximum velocity of is measured without phase wrapping. Complex regression Doppler OCT also demonstrates higher accuracy and precision compared with the conventional method, particularly when signal-to-noise ratio is low. The extended dynamic range allows monitoring of blood flow over several stages of development in embryos without adjusting the imaging parameters. In addition, applying complex averaging recovers hidden features in structural images.

Impaired Cardiac Functions and Aortic Elastic Properties in Patients with Severe Vitamin D Deficiency.

Background:The study explored the effect of severe Vitamin D deficiency on cardiac functions and aortic elastic properties determined by echocardiography.Patients and Methods:It included 56 patients with Vitamin D deficiency (Group 1; 16 men, 40 women; mean age 43.1 ± 11.4 years) and 42 healthy individuals with normal Vitamin D levels (Group 2; 11 men, 31 women; mean age 40.0 ± 7.5 years). Calcium, parathormone, alkaline phosphatase, and Vitamin D levels were measured from blood samples, and all participants underwent echocardiographic examination.Results:Left ventricular diastolic functions were determined by both conventional and tissue Doppler methods and were found to be impaired in Group 1 compared to Group 2. Aortic distensibility was significantly reduced in Group 1 compared to Group 2, whereas aortic stiffness index was significantly increased. Left atrial active emptying volume and fraction (LAAEV and LAAEF) were significantly higher in Group 1 than in Group 2. There were significant negative correlations between Vitamin D level and LAAEV, LAAEF, and septal E/E′ ratio and significant positive correlations between Vitamin D level and septal, lateral, anterior, and right ventricular annular E′ velocities.Conclusion:In severe Vitamin D deficiency, echocardiographically assessed diastolic functions appeared particularly impaired, and ventricular myocardial velocities and aortic elastic parameters were also adversely affected. In addition, LA mechanical functions were impaired, probably secondary to disturbed diastolic functions.

Cardiac changes in moderately malnourished children and their correlations with anthropometric and electrolyte changes.

To evaluate electrocardiographic and echocardiographic changes in moderately malnourished children and to correlate them with both anthropometric and electrolyte changes. Sixty moderately malnourished children were taken as patient group, and 60 healthy children of matched age and sex were taken as control group. Weight, height, body mass index (BMI), serum albumin, and electrolytes were measured for all children. Electrocardiographic evaluation for calculated QT (QTc) and QT dispersion (QTd) was performed. Left ventricular (LV) function was also evaluated using conventional echocardiography, tissue Doppler, and strain methods. Left ventricular mass index (LVMI) was also calculated. Weight, BMI, serum levels of albumin, total calcium, and ionized calcium were significantly lower, while QTc and QTd were significantly prolonged in malnourished children (P=.001 for all). There was significant reduction in LV fraction shortening (FS), LV E'/A', LV strain (S), LV myocardial performance index (MPI), LV global systolic strain (GLSS), and LVMI (P=.001 for all) in malnourished children. There was significant correlation between BMI and all cardiac variables. Moreover, there was significant positive correlation between serum albumin level and LV E'/A' (P=.02), LV GLSS (P=.03), and LVMI (P=.03).Total and ionized calcium level were significantly correlated with QTc, QTd, and LVMI (P<.05 for all). BMI was the most powerful predictor of these electrocardiographic and echocardiographic changes. Cardiac changes were present in moderately malnourished children as documented by electrocardiographic and echocardiographic changes, and these changes are in strong association with BMI and for a lesser extent with electrolyte changes especially serum calcium.

Precision Phenotyping in Heart Failure and Pattern Clustering of Ultrasound Data for the Assessment of Diastolic Dysfunction

ObjectivesThe aim of this study was to investigate whether cluster analysis of left atrial and left ventricular (LV) mechanical deformation parameters provide sufficient information for Doppler-independent assessment of LV diastolic function. BackgroundMedical imaging produces substantial phenotyping data, and superior computational analyses could allow automated classification of repetitive patterns into patient groups with similar behavior. MethodsThe authors performed a cluster analysis and developed a model of LV diastolic function from an initial exploratory cohort of 130 patients that was subsequently tested in a prospective cohort of 44 patients undergoing cardiac catheterization. Patients in both study groups had standard echocardiographic examination with Doppler-derived assessment of diastolic function. Both the left ventricle and the left atrium were tracked simultaneously using speckle-tracking echocardiography (STE) for measuring simultaneous changes in left atrial and ventricular volumes, volume rates, longitudinal strains, and strain rates. Patients in the validation group also underwent invasive measurements of pulmonary capillary wedge pressure and LV end diastolic pressure immediately after echocardiography. The similarity between STE and conventional 2-dimensional and Doppler methods of diastolic function was investigated in both the exploratory and validation cohorts. ResultsSTE demonstrated strong correlations with the conventional indices and independently clustered the patients into 3 groups with conventional measurements verifying increasing severity of diastolic dysfunction and LV filling pressures. A multivariable linear regression model also allowed estimation of E/e′ and pulmonary capillary wedge pressure by STE in the validation cohort. ConclusionsTracking deformation of the left-sided cardiac chambers from routine cardiac ultrasound images provides accurate information for Doppler-independent phenotypic characterization of LV diastolic function and noninvasive assessment of LV filling pressures.

The hemodynamics of late-onset intrauterine growth restriction by MRI

Late-onset intrauterine growth restriction (IUGR) results from a failure of the placenta to supply adequate nutrients and oxygen to the rapidly growing late-gestation fetus. Limitations in current monitoring methods present the need for additional techniques for more accurate diagnosis of IUGR in utero. New magnetic resonance imaging (MRI) technology now provides a noninvasive technique for fetal hemodynamic assessment, which could provide additional information over conventional Doppler methods. The objective of the study was to use new MRI techniques to measure hemodynamic parameters and brain growth in late-onset IUGR fetuses. This was a prospective observational case control study to compare the flow and T2 of blood in the major fetal vessels and brain imaging findings using MRI. Indexed fetal oxygen delivery and consumption were calculated. Middle cerebral artery and umbilical artery pulsatility indexes and cerebroplacental ratio were acquired using ultrasound. A score of ≥ 2 of the 4 following parameters defined IUGR: (1) birthweight the third centile or less or 20% or greater drop in the centile in estimated fetal weight; (2) lowest cerebroplacental ratio after 30 weeks less than the fifth centile; (3) ponderal index < 2.2; and (4) placental histology meets predefined criteria for placental underperfusion. Measurements were compared between the 2 groups (Student t test) and correlations between parameters were analyzed (Pearson's correlation). MRI measurements were compared with Doppler parameters for identifying IUGR defined by postnatal criteria (birthweight, placental histology, ponderal index) using receiver-operating characteristic curves. We studied 14 IUGR and 26 non-IUGR fetuses at 35 weeks' gestation. IUGR fetuses had lower umbilical vein (P = .004) and pulmonary blood flow (P = .01) and higher superior vena caval flow (P < .0001) by MRI. IUGR fetuses had asymmetric growth but smaller brains than normal fetuses (P < .0001). Newborns with IUGR also had smaller brains with otherwise essentially normal findings on MRI. Vessel T2s, oxygen delivery, oxygen consumption, middle cerebral artery pulsatility index, and cerebroplacental ratio were all significantly lower in IUGR fetuses, whereas there was no significant difference in umbilical artery pulsatility index. IUGR score correlated positively with superior vena caval flow and inversely with oxygen delivery, oxygen consumption, umbilical vein T2, and cerebroplacental ratio. Receiver-operating characteristic curves revealed equivalent performance of MRI and Doppler techniques in identifying IUGR that was defined based on postnatal parameters with superior vena caval flow area under the curve of 0.94 (95% confidence interval, 0.87-1.00) vs a cerebroplacental ratio area under the curve of 0.80 (95% confidence interval, 0.64-0.97). MRI revealed the expected circulatory redistribution in response to hypoxia in IUGR fetuses. The reduced oxygen delivery in IUGR fetuses indicated impaired placental oxygen transport, whereas reduced oxygen consumption presumably reflected metabolic adaptation to diminished substrate delivery, resulting in slower fetal growth. Despite brain sparing, placental insufficiency limits fetal brain growth. Superior vena caval flow and umbilical vein T2 by MRI may be useful new markers of late-onset IUGR.

Left and Right Ventricle Functions in Patients Obstructive Sleep Apnea and Their Relationship with Apelin Levels

Aim of this study is to determine the left and right ventricle functions by echocardiography in patients with newly diagnosed obstructive sleep apnea (OSA) and to investigate whether there is a relationship between the apelin levels and systolic and diastolic functions of the right and left ventricles. Study included 44 patients (30 males, 14 females; mean age 49.8±11.5 years) diagnosed with obstructive sleep apnea according to polysomnographically determined apnea hypopnea index, and 30 control subjects (25 males, 5 females; mean age 43.03±10.89 years) diagnosed with simple snoring. Apelin levels of all the study subjects are measured. Systolic and diastolic functions of both ventricles were evaluated with the help of conventional and tissue Doppler methods. Results: Systolic and diastolic blood pressure levels of the OSA group were significantly higher compared to those of the AHI control group. Lateral inferior and anterior E’ were significantly lower whereas E/E’ was significantly higher in the OSA group compared to the control group (8.40±3.24 vs. 10.80±3.24; p=0.001, 7.50±2.60 vs 9.00±2.51; p=0.009, 7.90±2.68 vs. 8.90±2.73; p=0.006, 7.57±3.20 vs. 6.44±1.55; p=0.023, respectively). Although the apelin levels were higher in the OSA group compared to the control group, this difference did not reach statistical significance. Age, AHI, and echocardiographic indices were not cor related with the apelin levels. There was no relationship between the severity of OSA and the apelin levels, either. This study showed diastolic functions may be impaired in patinets with newly diagnosed OSA. Apelin levels which has been shown to play an important role in cardiovascular hemodynamics, had no significant correlation with OSA severity. Moreover, there was no signifi cant correlation between the apelin levels and echocardiographically assessed systolic and diastolic functions of both ventricles.

A dealiasing method for use with ultrasonic pulsed Doppler in measuring velocity profiles and flow rates in pipes

The ultrasonic pulsed Doppler method (UDM) is a powerful tool for measuring velocity profiles in a pipe. However, the maximum detectable velocity is limited by the Nyquist sampling theorem. Furthermore, the maximum detectable velocity (also called Nyquist velocity), vmax, and the maximum measurable length are related and cannot be increased at the same time. If the velocity is greater than vmax, velocity aliasing occurs. Hence, the higher velocity that occurs with a larger pipe diameter, i.e. under higher flow rate conditions, cannot be measured with the conventional UDM. To overcome these limitations, dual-pulse repetition frequency (dual PRF) and feedback methods were employed in this study to measure velocity profiles in a pipe. The velocity distributions obtained with the feedback method were found to be more accurate than those obtained with the dual PRF method. However, misdetection of the Nyquist folding number using the feedback method was found to increase with the flow velocity. A feedback method with a moving average is proposed to improve the measurement accuracy. The method can accurately measure the velocity distributions at a velocity five times greater than the maximum velocity that can be measured with the conventional UDM. The measurement volume was found to be among the important parameters that must be considered in assessing the traceability of the reflector during the pulse emission interval. Hence, a larger measurement volume is required to measure higher velocities using the dual PRF method. Integrating velocity distributions measured using the feedback method with a moving average makes it possible to accurately determine flow rates six times greater than those that can be determined using the conventional pulsed Doppler method.

Fetal Dual Doppler Echocardiography

ABSTRACT Dual Doppler echocardiography is a recently developed technique performed using an instrument with two separate sample gates, allowing simultaneous recording of signals from two locations. We describe the use of dual Doppler echocardiography to assess fetal cardiac rhythm. Fetal arrhythmias are common and encountered in 1 to 2% pregnancies. They often resolve spontaneously and do not require treatment, but sometimes lead to severe morbidity and mortality. Fetal arrhythmias are responsive to fetal therapy and require appropriate management through accurate diagnosis. Pulsed wave Doppler and M-mode echocardiography are widely used to assess fetal cardiac rhythm. Both methods have advantages and limitations, which are influenced by fetal position, image resolution, and the complexity of the arrhythmia. We developed a new technique that records pulsed wave Doppler signals in the hepatic vein (HV) and the descending aorta (DAo) simultaneously using dual Doppler. This method is less influenced by fetal position and the complexity of the arrhythmia, and the images have better resolution than those acquired using conventional Doppler methods in most cases. Although, electrical parameters, such as the QT interval cannot be evaluated, dual Doppler recording of flows in HV and DAo is an efficient and effective method for assessing fetal cardiac rhythms, allowing precise diagnosis of cardiac arrhythmias. How to cite this article Kaji T, Maeda K, Hichijo A, Takahashi Y, Nakayama S, Irahara M. Fetal Dual Doppler Echocardiography. Donald School J Ultrasound Obstet Gynecol 2014; 8(4):376-381.

Experimental verification of color flow imaging based on wideband Doppler method.

The purpose of this study is to eliminate the aliasing in color flow imaging. The wideband Doppler method is applied to generate a color flow image, and the validity of the method is experimentally confirmed. The single beam experiment is carried out to confirm the velocity estimation based on the wideband Doppler method. The echo data for the conventional pulsed Doppler method and the wideband Doppler method are obtained using a flow model, and the estimated velocity for each method is compared. The color flow images for each method are also generated using several types of flow model. The generated images are compared, and the characteristics of the imaging based on the wideband Doppler method are discussed. The high velocity beyond the Nyquist limit is successfully estimated by the wideband Doppler method, and the availability in low velocity estimation is also confirmed. The aliasing in color flow images is eliminated, and the generated images show the significance of the elimination of the aliasing in the flow imaging. The aliasing in color flow imaging can be eliminated by the wideband Doppler method. This technique is useful for the exact understanding of blood flow dynamics.