Combined Doppler Research Articles

3D ultrafast ultrasound imaging in vivo

Very high frame rate ultrasound imaging has recently allowed for the extension of the applications of echography to new fields of study such as the functional imaging of the brain, cardiac electrophysiology, and the quantitative imaging of the intrinsic mechanical properties of tumors, to name a few, non-invasively and in real time. In this study, we present the first implementation of Ultrafast Ultrasound Imaging in 3D based on the use of either diverging or plane waves emanating from a sparse virtual array located behind the probe. It achieves high contrast and resolution while maintaining imaging rates of thousands of volumes per second. A customized portable ultrasound system was developed to sample 1024 independent channels and to drive a 32 × 32 matrix-array probe. Its ability to track in 3D transient phenomena occurring in the millisecond range within a single ultrafast acquisition was demonstrated for 3D Shear-Wave Imaging, 3D Ultrafast Doppler Imaging, and, finally, 3D Ultrafast combined Tissue and Flow Doppler Imaging. The propagation of shear waves was tracked in a phantom and used to characterize its stiffness. 3D Ultrafast Doppler was used to obtain 3D maps of Pulsed Doppler, Color Doppler, and Power Doppler quantities in a single acquisition and revealed, at thousands of volumes per second, the complex 3D flow patterns occurring in the ventricles of the human heart during an entire cardiac cycle, as well as the 3D in vivo interaction of blood flow and wall motion during the pulse wave in the carotid at the bifurcation. This study demonstrates the potential of 3D Ultrafast Ultrasound Imaging for the 3D mapping of stiffness, tissue motion, and flow in humans in vivo and promises new clinical applications of ultrasound with reduced intra—and inter-observer variability.

Effects of Thoratec pulsatile ventricular assist device timing on the abdominal aortic wave intensity pattern.

Arterial waves are seen as possible independent mediators of cardiovascular risks, and the wave intensity analysis (WIA) has therefore been proposed as a method for patient selection for ventricular assist device (VAD) implantation. Interpreting measured wave intensity (WI) is challenging, and complexity is increased by the implantation of a VAD. The waves generated by the VAD interact with the waves generated by the native heart, and this interaction varies with changing VAD settings. Eight sheep were implanted with a pulsatile VAD (PVAD) through ventriculoaortic cannulation. The start of PVAD ejection was synchronized to the native R wave and delayed between 0 and 90% of the cardiac cycle in 10% steps or phase shifts (PS). Pressure and velocity signals were registered, with the use of a combined Doppler and pressure wire positioned in the abdominal aorta, and used to calculate the WI. Depending on the PS, different wave interference phenomena occurred. Maximum unloading of the left ventricle (LV) coincided with constructive interference and maximum blood flow pulsatility, and maximum loading of the LV coincided with destructive interference and minimum blood flow pulsatility. We believe that noninvasive WIA could potentially be used clinically to assess the mechanical load of the LV and to monitor the peripheral hemodynamics such as blood flow pulsatility and risk of intestinal bleeding.

An acoustic metamaterial with unusual wave properties

Several structural variants of a new acoustic metamaterial are proposed with unusual wave properties, and normal wave dispersion is studied. One of the variants is a bandpass filter in whose passband the phase velocity of a normal wave is negative. In another variant, there are two passbands: in the first, the phase velocity is positive; in the second, negative. As a result, unusual physical phenomena can be observed in it, in particular, a special type of birefringence and the combined Doppler effect. In the long-wavelength range, where the metamaterial behaves like a continuous medium, the corresponding equations have been derived in partial derivatives. Essential differences from the common wave equation are noted.

Noninvasive evaluation of left ventricular force-frequency relationships by measuring carotid arterial wave intensity during exercise stress.

Background and purposeEstimation of the contractility of the left ventricle during exercise is important in drawing up a protocol of cardiac rehabilitation. It has been demonstrated that color Doppler- and echo tracking-derived carotid arterial wave intensity is a sensitive index of global left ventricular (LV) contractility. We assessed the feasibility of measuring carotid arterial wave intensity and determining force−frequency (contractility−heart rate) relations (FFRs) during exercise totally noninvasively.MethodsWe measured carotid arterial wave intensity with a combined color Doppler and echo tracking system in 25 healthy young male volunteers (age 20.8 ± 1.2 years) at rest and during exercise. FFRs were constructed by plotting the maximum value of wave intensity (WD1) against heart rate (HR).ResultsWe first confirmed that HR increased linearly with an increase in work load in each subject (r2 = 0.95 ± 0.04). WD1 increased linearly with an increase in HR. The goodness-of-fit of the regression line of WD1 on HR in each subject was very high (r2 = 0.48−0.94, p < 0.0001, respectively). The slope of the WD1-HR relation ranged 0.30−2.20 [m/s3 (beat/min)].ConclusionsGlobal LV FFRs can be generated in healthy young volunteers with an entirely noninvasive combination of exercise and wave intensity. These data should show the potential usefulness of the FFR in the context of cardiac rehabilitation.

The effect of ageing on ocular blood flow, oxygen tension and retinal function during and after intraocular pressure elevation.

PurposeTo investigate the effect of ageing on the recovery of ocular blood flow, intravitreal oxygen tension and retinal function during and after intraocular pressure (IOP) elevation.MethodsLong Evans rats (3- and 14-month-old) underwent acute stepwise IOP elevation from 10 to 120 mmHg (5 mmHg steps each 3 minutes). IOP was then returned to baseline and recovery was monitored for 2 hours. Photopic electroretinograms (ERG) were recorded at each IOP step during stress and at each minute during recovery. Ocular blood flow and vitreal oxygen tension (pO2) were assayed continuously and simultaneously using a combined laser Doppler flow meter (LDF) and an oxygen sensitive fibre-optic probe, respectively. The combined sensor was placed in the vitreous chamber, proximal to the retina. Data were binned into 3 minute intervals during stress and 1 min intervals during recovery. Recovery data was described using a bi-logistic function.ResultsRats of both ages showed similar susceptibility to IOP elevation, with pO2 showing a closer relationship to ERG than LDF. During recovery, both ages showed a distinctive two-phased recovery for all three measures with the exception of the LDF in 3-month-old rats, which showed only 1 phase. In all animals, LDF recovered fastest (<1 minute), followed by pO2 (<10 minute) and ERG (>1 hour). 14-month-old rats showed surprisingly faster and greater LDF recovery compared to the younger group, with similar levels of pO2 recovery. However, the ERG in these middle-aged animals did not fully recover after two hours, despite showing no difference in susceptibility to IOP during stress compared to the young group.ConclusionsYoung and middle-aged eyes showed similar susceptibility to IOP elevation in terms of pO2, LDF and ERG. Despite this lack of difference during stress, older eyes did not completely recover function, suggesting a more subtle age-related susceptibility to IOP.

Blunted cerebrovascular response to exogenous nitric oxide in POTS (1068.12)

Cognitive deficits are characteristic of postural tachycardia syndrome (POTS). Intact nitrergic nitric oxide (NO) is important to cerebral blood flow (CBF) regulation, to neurovascular coupling, and to cognitive efficacy. POTS patients often experience defective (NO) mediated vasodilation caused by oxidative stress. We used combined transcranial Doppler ultrasound, to measure CBF velocity (CBFv), and near‐infrared spectroscopy (NIRS), to measure cerebral oximetry while supine. We previously showed dilation of the middle cerebral artery (MCA) in response to a bolus administration of the NO donor sodium nitroprusside (SNP) in healthy volunteers. We hypothesized a blunted MCA response to SNP in POTS. The SNP responses of 17 POTS patients were compared with 12 healthy controls (ages 14‐28). CBFv in POTS and control were not different at baseline (75 ± 3 vs. 71 ±2 cm • s‐1 P = 0.31) and decreased to a lesser degree with SNP in POTS (to 71 ± 3 vs 62 ± 2 cm • s‐1; P = 0.02). The changes in total and oxygenated hemoglobin (8.83 ± 0.45 and 8.13 ± 0.48 µmol/kg tissue) were markedly reduced in POTS compared to control (14.2 ± 1.4 and 13.6 ± 1.6 µmol/kg tissue), primarily due to increased venous efflux. The data indicate reduced cerebral oxygenation, blunting of cerebral arterial vasodilation and heightened cerebral venodilation in response to exogenous NO.Grant Funding Source: NHLBI

Role of real time elastography in preoperative diagnostic of solitary thyroid nodules

Background: In the presence of a solid thyroid nodule, the therapeutically approach is imposed by the probability of a malignancy. Ultrasound is considered to be “the” imagistic diagnostic tool, and the golden standard is represented by the FNAB. US elastography is currently used in differentiation of malignant from benign lesions. Method: This prospective study included 112 patients, mean age 52.08 ± 11.43 years, 65 females and 47 men, with solitary thyroid nodules on conventional US, with a volume higher than 0.50 ml. Complete ultrasound evaluation was performed for each case: gray scale, Doppler and strain elastography. All patients underwent surgery after complete evaluation. Extemporaneous and postsurgical histopathological exam were performed in all cases. Results: We identified 19 cases with cancer and 93 benign lesions. We calculated the diagnostic value for each ultrasound parameter, and we saw that some parameters are significant in diagnosing thyroid malignancy: irregular margins (AUC = 0.761, p = 0.00001), taller than wide (AUC = 0.723, p = 0.0001), positive calcification (AUC = 0.7416, p = 0.0001), absent halo sign (AUC = 0.717, p = 0.0001), extracapsular invasion (AUC = 0.684, p = 0.0012). Presence of 4 suspect signs increases diagnostic quality (AUC = 0.8529, p = 0.000), and combined evaluation US-2B and Doppler have even better results (AUC = 0.8985, p = 0.00001. Nevertheless, diagnostic quality of RTE is higher than all separate or combine conventional ultrasound evaluation: AUC = 0.99, p = 0.0001 Conclusion: RTE color map screen is a useful tool in discriminating solitary thyroid masses.

Tissue Doppler imaging optical flow (TDIOF): a combined B-mode and tissue Doppler approach for cardiac motion estimation in echocardiographic images.

The quantitative analysis of cardiac motion from echocardiographic images helps clinicians in the diagnosis and therapy of patients suffering from heart disease. Quantitative analysis is usually based on tissue Doppler imaging (TDI) or speckle tracking. These methods are based on two techniques which to a large degree are independent: the Doppler phenomenon and image sequence processing. Herein, to increase the accuracy of the speckle tracking technique and to cope with the angle dependence of TDI, a combined approach dubbed tissue Doppler imaging optical flow (TDIOF) is proposed. TDIOF is formulated based on the combination of B-mode and Doppler energy terms minimized using algebraic equations and is validated on simulated images, and in vivo data. It was observed that the additional Doppler term is able to increase the accuracy of speckle tracking, compared to two popular motion estimation and speckle tracking techniques (Horn-Schunck and block matching methods). This observation was more pronounced when noise was present. The magnitude and angular error for TDIOF applied to simulated images, when comparing estimated motion with ground-truth motion, were 15% and 9.2°/frame, respectively. As an additional validation, echocardiography-derived strains were compared to tagged MRI-derived myocardial strains in the same subjects. The correlation coefficient (r) between the TDIOF-derived radial strains and tagged MRI-derived radial strains value was 0.83 (P < 0.001). The correlation coefficient ( r) for the TDIOF-derived circumferential strains compared to the tagged MRI-derived circumferential strains was 0.86 (P < 0.001). The comparison of TDIOF-derived and block matching speckle tracking and Horn-Schunck optical flow strain values using student t-test demonstrated superiority of TDIOF (95% confidence interval, P < 0.001).

Assessment of ventriculo-arterial interaction in pulmonary arterial hypertension using wave intensity analysis

To the Editor: Wave intensity analysis (WIA) is a recently described haemodynamic analysis methodology which enables assessment of ventriculo-arterial interactions via time-domain analysis of pressure and flow waveforms [1]. It enables quantification of wave energy, separation of waves into forward and backward components, and estimation of wave speed [2]. To date, WIA has not been applied to the pulmonary arterial circulation in humans. As WIA offers a potential novel approach for the study of pulmonary haemodynamics, the present study sought to evaluate the feasibility of invasive WIA of the pulmonary circulation during right heart catheterisation (RHC). The study was approved by the institutional review board (Sydney Local Health District Ethics Review Committee (RPA Zone)) and consent was obtained from seven controls (mean±sd age 69±9 years, three females) and six patients (age 56±13 years, four females) with pulmonary arterial hypertension (PAH). Control subjects presented to the cardiac catheterisation laboratory for investigation of possible coronary artery disease. Following standard pulmonary haemodynamic measurements (including thermodilution cardiac output), a combined dual-tipped pressure and Doppler wire (ComboWire; Volcano, Rancho Cordova, CA, USA) was positioned distal to the origin of the right or left lower lobe pulmonary artery via a 6 Fr multipurpose catheter (Mach 1; Boston Scientific, Natick, MA, USA) under angiographic guidance. Pressure and flow measurements were acquired simultaneously at a sampling frequency of 1000 Hz, once stable signals were obtained. Data were processed offline using customised MatLab software (MathWorks, Natick, MA, USA). Signals were ensemble-averaged with timing gated to the ECG R-wave and smoothed using a Savitzky–Golay filter [3]. Intrinsic hardware processing delays (between pressure and flow signals) were corrected by shifting signals to achieve a linear pressure–flow (P–U) relationship in early systole [4]. Wave speed (c) was derived from the P-U loop method …

Real-time 3D curved needle segmentation using combined B-mode and power Doppler ultrasound.

This paper presents a real-time segmentation method for curved needles in biological tissue based on analysis of B-mode and power Doppler images from a tracked 2D ultrasound transducer. Mechanical vibration induced by an external voice coil results in a Doppler response along the needle shaft, which is centered around the needle section in the ultrasound image. First, B-mode image analysis is performed within regions of interest indicated by the Doppler response to create a segmentation of the needle section in the ultrasound image. Next, each needle section is decomposed into a sequence of points and transformed into a global coordinate system using the tracked transducer pose. Finally, the 3D shape is reconstructed from these points. The results of this method differ from manual segmentation by 0.71 ± 0.55 mm in needle tip location and 0.38 ± 0.27 mm along the needle shaft. This method is also fast, taking 5-10 ms to run on a standard PC, and is particularly advantageous in robotic needle steering, which involves thin, curved needles with poor echogenicity.

A new coarse-time GPS positioning algorithm using combined Doppler and code-phase measurements

A new coarse-time Global Positioning System (GPS) positioning algorithm based on the use of Doppler and code-phase measurements is proposed and described. The proposed method was demonstrated to be essential for reducing the time to first fix and the power consumption in a GPS receiver. Only 1 ms of data is required to obtain a positioning fix with accuracy comparable to that of the traditional GPS navigation algorithm. The algorithm is divided into two parts. In the first part, the Doppler measurement of the GPS signal is used to determine the coarse user position. With proper constraints, the required time accuracy for the Doppler measurements can be relaxed to be as long as 12 h. In the second part of the algorithm, the accurate user position is calculated by means of the 1 ms code-phase data. The traditional tracking process is no longer necessary in the proposed algorithm. Using the acquired 1-ms code-phase measurement, the positioning accuracy was determined to be approximately a few tens of meters in our experimental results. However, if the data length is extended to 10 ms, the positioning accuracy can be improved to within 10---20 m, which is similar to that of the traditional GPS positioning method. Various experiments were conducted to verify the usefulness of the proposed algorithm.

Responsiveness of a combined gray-scale and power Doppler synovitis ultrasound score in comparison to a sum score of 5 joints of the wrist and hand - One-year evaluation of an RA cohort

Purpose: To evaluate the responsiveness of a combined gray-scale (GS) and power Doppler (PD) US score over one year compared to synovitis sum scores of five joints (US5) in RA patients taking different anti-rheumatic therapies.

Specific formulas improve the estimation of fetal weight by ultrasound scan

Objective: To develop and evaluate local, sex specific, small for gestational age (SGA) specific, large for gestational age (LGA) specific and combined (biometry, sex and Doppler indices) formulas for ultrasound estimated fetal weight (EFW).Method: Low-risk singleton pregnancies that delivered within 7 days from ultrasound examination were assessed. A formula-generating group (1407 pregnancies) and a validation group (469 pregnancies) were created. Fractional regression analysis was used to develop the formulas. Systematic error, random error, fraction within the 10% of actual birth weight and Bland–Altman analysis were used.Results: The local formula and the Hadlock formula with local co-efficients performed better than the Hadlock formula. The SGA-specific formula, the LGA-specific formula and the combined formula had the lower systematic error (MSE: +0.0022291, −0.4226888, +0.8386222, respectively) and the narrower 95% LOA (−292.8 to +292.23, −485.6 to +461.5, −425.7 to +450.46, respectively). The SGA- and the LGA-specific formulas had higher fraction within the 10% of actual birth weight (81.5% and 84%, respectively).Conclusions: Local formulas improve the EFW calculation. The combined formula can further optimize the accuracy and precision. Application of specific formulas for the small and the large fetus had the most pronounced effect in improving fetal weight estimation.

Zonal perfusion patterns in pedicled free-style perforator flaps

Local perforator flaps have become a standard procedure in reconstructive surgery. They allow the transfer of large tissue units with minimal donor-site morbidity. However, clinical studies on flap perfusion changes over time are lacking. The aim of this study was to investigate the perfusion of free-style single perforator flaps with an eccentrically located main perforator by combined laser Doppler spectrophotometry. Ten patients (six male, four female, 29-71 years) were included in this prospective clinical study. All flaps were based on one perforator. Flaps were harvested from the trunk (n = 6) or the proximal upper or lower extremity (n = 4). Flap perfusion was assessed using a combined laser Doppler spectrophotometry (CLDS) device (O2C, Oxygen to See, LEA Medizintechnik, Giessen, Germany) at days 0, 1, 7 and 14 in different zones. Flap dimensions were 18.6 ± 4.7 × 7.2 ± 1.6 cm. Two flaps developed minor tip necroses (<10%), eight flaps survived completely. CLDS proved to be very sensitive for the detection of regional perfusion problems. A considerable perfusion gradient was observed at days 0 and 1. Here, reduced blood flow and post-capillary oxygen saturations were found at the tip when compared to the region above main perforator (RAMP). Blood flow remained stable proximally while it improved significantly from day 1 to 14 at the tip region. CLDS is an effective method for objective evaluation of flap perfusion. Although distal flap perfusion is diminished initially, the majority of perforator flaps with eccentrically located perforators survive completely. Obviously, flap perfusion improved between days 1 and 14. This clinical finding might be explained by reorganisation of the vascular system with opening of so-called connecting or choke vessels. This knowledge might influence decision making in perforator flap surgery.

In vitro assessment of combined Doppler ultrasound and CFD modeling in arterial blood flow quantification

Spatiotemporal quantification of the blood flow in the human vasculature has been greatly aided with the non-invasive proposition offered by Doppler ultrasound. However, relatively large deviation of the blood flow measurement from the actual value is expected, owing to a number of contributing factors. The research work expounded here attempts to ameliorate the accuracy of the blood flow output quantification by combining the Doppler measurement with the computational fluid dynamics modeling based on Navier–Stokes equation. In vitro assessment of the integrated approach was carried out with custom made phantom and probe positioning Mechatronic system. Analysis of the experimental results showed that, compared to the stand alone Doppler ultrasound measurement, the integrated model gives better accuracy in quantifying the volume flow rate.

THE TRENDS HIGH-CONTRAST IMAGING SURVEY. II. DIRECT DETECTION OF THE HD 8375 TERTIARY

We present the direct imaging detection of a faint tertiary companion to the single-lined spectroscopic binary HD 8375 AB. Initially noticed as an 53 m/s/yr Doppler acceleration by Bowler et al. 2010, we have obtained high-contrast adaptive optics observations at Keck using NIRC2 that spatially resolve HD 8375 C from its host(s). Astrometric measurements demonstrate that the companion shares a common proper-motion. We detect orbital motion in a clockwise direction. Multiband relative photometry measurements are consistent with a spectral-type of M1V. Our combined Doppler and imaging observations place a lower-limit of m>0.297Msun on its dynamical mass. We also provide a refined orbit for the inner pair using recent RV measurements obtained with HIRES. HD 8375 is one of many triple-star systems that are apparently missing in the solar neighborhood.

Subclinical Myocardial Deformation Abnormalities in Asymptomatic Patients with Moderate to Severe Aortic Regurgitation: A Combined Tissue Doppler and Strain Rate Imaging Study

Background: Early detection of myocardial contractility disturbances in patients with asymptomatic moderate to severe aortic regurgitation (AR) leads to the early operative intervention early enough to prevent from poor postoperative heart failure (HF) prognosis. Objective: Our aim was to study the subclinical left ventricular (LV) dysfunction, by novel echocardiographic methods, myocardial deformation indices in patients with asymptomatic, and significant aortic regurgitation (AR). Patients and Methods: Standard echocardiogram and complementary tissue Doppler imaging (TDI) and Doppler based strain and strain rate (S/SR) imaging were performed in 44 asymptomatic patients with pure and significant AR and ejection fraction (EF) more than 50% (mean age:49.9 ± 17.2 years, 50% male) and 20 healthy participants (mean age: 47.3 ± 13.8 years, 65% male). In addition to TDI velocities to investigate the LV longitudinal deformation, peak systolic S and SR were measured at septal, lateral and posterior walls. The LV modified myocardial performance index (MPI) or Tie index also were calculated via TDI study. Results: AR group had significantly increased LV end systolic and end diastolic volumes, interventricular septum and posterior wall thickness compared to controls. In AR, Sm and Em of septal wall, Sm of lateral wall; S and SR of both septal and lateral walls were significantly decreased while MPI were significantly increased compared to healthy participants. Conclusions: Our results demonstrated the ability of PW-TDI and S/SR modalities in detection of the early subclinical abnormalities in asymptomatic patients with significant chronic AR.

SAT0488 Sensitivity to Change of a Combined Gray-Scale and Power Doppler Ultrasound Score for Synovitis in Comparison to a Sum Score of 5 Joints of the Wrist and Hand – One-Year Evaluation of an RA Cohort.

BackgroundSeveral ultrasound (US) scoring systems have been proposed for evaluating objectively RA patients’ responsiveness under treatment [1-3].ObjectivesTo evaluate the sensitivity to change over one year of a combined gray-scale (GS)...

Study of the thermal mixing between two non-isothermal sprays using combined three-color LIF thermometry and phase Doppler analyzer

The aim of this experimental work was to demonstrate the ability of three-color laser-induced fluorescence (3cLIF) thermometry to study the thermal mixing of two non-isothermal water sprays. Combined 3cLIF-phase Doppler analyzer measurements were also implemented to derive correlations between droplet size and temperature. Both sprays had different characteristics in terms of flow rate and droplet size distribution. The liquid spray was successively pre-heated, and the other spray was maintained and injected at ambient temperature. The thermal mixing will be discussed in light of a wide set of experimental results obtained under various experimental conditions, including different liquid flow rates, droplet size distributions and droplet concentrations. To analyze the potential effect of droplet coalescence on the mean local liquid temperature, both sprays were alternatively seeded with fluorescent dye. Main results show that significant heating of cold spray is possible when the hot spray is injected with the higher flow rate. Moreover, this heating affects only the smallest droplets.

The mechanism of mid-latitude Pi2 waves in the upper ionosphere as revealed by combined Doppler and magnetometer observations

Abstract. The interpretation of simultaneous ionospheric Doppler sounding and ground magnetometer observations of low-latitude Pi2 waves is revised. We compare the theoretical estimates of the ionospheric Doppler velocity for the same amplitude of the ground magnetic disturbances produced by a large-scale compressional mode and an Alfvén mode. The plasma vertical displacement caused by the wave electric field is shown to be the dominating effect. Taking into account the correction of the previous paper, the observations of low-latitude Pi2 in the F layer ionosphere by Doppler sounding and SuperDARN (Super Dual Auroral Radar Network) radars give consistent results. We suggest that the Doppler response to Pi2 waves is produced by the Alfvén wave component, but not the fast-mode component, whereas the ground magnetic signal is composed from both Alfvén and fast magnetosonic modes.