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pulsed wave Doppler ultrasound pulsed Doppler ultrasound [keywords]
- Respirophasic carotid artery peak velocity variation as a predictor of fluid responsiveness in mechanically ventilated patients with coronary artery disease. [JOURNAL ARTICLE]
- Br J Anaesth 2014 Apr 9.
/st>We studied respirophasic variation in carotid artery blood flow peak velocity (ΔVpeak-CA) measured by pulsed wave Doppler ultrasound as a predictor of fluid responsiveness in mechanically ventilated patients with coronary artery disease./st>Forty patients undergoing elective coronary artery bypass surgery were enrolled. Subjects were classified as responders if stroke volume index (SVI) increased ≥15% after volume expansion (6 ml kg(-1)). The ΔVpeak-CA was calculated as the difference between the maximum and minimum values of peak velocity over a single respiratory cycle, divided by the average. Central venous pressure, pulmonary artery occlusion pressure, pulse pressure variation (PPV), and ΔVpeak-CA were recorded before and after volume expansion./st>PPV and ΔVpeak-CA correlated significantly with an increase in SVI after volume expansion. Area under the receiver-operator characteristic curve (AUROC) of PPV and ΔVpeak-CA were 0.75 [95% confidence interval (CI) 0.59-0.90] and 0.85 (95% CI 0.72-0.97). The optimal cut-off values for fluid responsiveness of PPV and ΔVpeak-CA were 13% (sensitivity and specificity of 0.74 and 0.71) and 11% (sensitivity and specificity of 0.85 and 0.82), respectively. In a subgroup analysis of 17 subjects having pulse pressure hypertension (≥ 60 mm Hg), PPV failed to predict fluid responsiveness (AUROC 0.70, P=0.163), whereas the predictability of ΔVpeak-CA remained unchanged (AUROC 0.90, P=0.006)./st>Doppler assessment of respirophasic ΔVpeak-CA seems to be a highly feasible and reliable method to predict fluid responsiveness in mechanically ventilated patients undergoing coronary revascularization.Clinical trial registrationNCT 01836081.
- Guidance for accurate and consistent tissue Doppler velocity measurement: comparison of echocardiographic methods using a simple vendor-independent method for local validation. [JOURNAL ARTICLE]
- Eur Heart J Cardiovasc Imaging 2014 Apr 2.
Variability has been described between different echo machines and different modalities when measuring tissue velocities. We assessed the consistency of tissue velocity measurements across different modalities and different manufacturers in an in vitro model and in patients. Furthermore, we present freely available software tools to repeat these evaluations.We constructed a simple setup to generate reproducible motion and used it to compare velocities measured using three echocardiographic modalities: M-mode, speckle tracking, and tissue Doppler, with a straightforward, non-ultrasound, optical gold standard. In the clinical phase, 25 patients underwent M-mode, speckle tracking, and tissue Doppler measurements of s', e', and a' velocities.In vitro, the M-mode and speckle tracking velocities agreed with optical assessment. Of the three possible tissue Doppler measurement conventions (outer, middle, and inner edge) only the middle agreed with optical assessment (discrepancy -0.20 (95% CI -0.44 to 0.03) cm/s, P = 0.11, outer +5.19 (4.65 to 5.73) cm/s, P < 0.0001, inner -6.26 (-6.87 to -5.65) cm/s, P < 0.0001). A similar pattern occurred across all four studied manufacturers. M-mode was therefore chosen as the in vivo gold standard.Clinical measurements of s' velocities by speckle tracking and the middle line of the tissue Doppler showed concordance with M-mode, while the outer line overestimated significantly (+1.27(0.96 to 1.59) cm/s, P < 0.0001) and the inner line underestimated (-1.82 (-2.11 to -1.52) cm/s, P < 0.0001).Echocardiographic velocity measurements can be more consistent than previously suspected. The statistically modal velocity, found at the centre of the spectral pulsed wave tissue Doppler envelope, most closely represents true tissue velocity. This article includes downloadable, vendor-independent software enabling calibration of echocardiographic machines using a simple, inexpensive in vitro setup.
- Ultrasonic detection of decompression-induced bubbles. [Editorial]
- Diving Hyperb Med 2014 Mar; 44(1):2-3.
Detection of gas emboli (bubbles) using ultrasound is a principle tool for monitoring decompression stress short of symptom development. Decompression-induced bubbles were first observed 47 years ago at the Virginia Mason Research Center as audible signals from sheep being monitored with a Doppler ultrasonic flowmeter. Bubbles were later observed in human divers following decompression. Aural detection of decompression induced bubbles usually employs continuous-wave Doppler ultrasonic bubble detection (DUBD) using transcutaneous transducers to monitor a three-dimensional volume of blood in the precordial region (pulmonary artery or right ventricle of the heart) or peripheral veins such as the subclavian. Pulsed DUBD may provide more sensitivity and reduce background noise since 'range-gating' can be used to look at a specific distance from the transducer where bubbles are expected. However, it is more difficult to use, particularly with multiple subjects who are measured serially, and not widely applied in decompression studies. In either case, the portability of the instruments makes them useful for both laboratory and field studies. The use of two-dimensional (2D) echocardiography to look for bubbles in the chambers of the heart is a more recent development. 2D systems can provide a cross-sectional view along a single plane of all four chambers of the heart. Thus, unlike DUBD systems that assess only blood prior to pulmonary filtration, 2D imaging systems can also assess blood that will be sent systemically. Initially, 2D scanning devices were of sufficient bulk to be limited to laboratory studies. However, within the last 15 years, battery-operated portable units with sufficient resolution have become available for field studies. Technological advances, particularly harmonic processing, which allows analysis of less noisy signals at a harmonic frequency other than at the return of the fundamental frequency sent out by the device, have made it possible to achieve image resolution close to that of standard clinical laboratory instruments. While transoesophageal echocardiography offers better resolution, transthoracic echocardiography is more appropriate for the relatively prolonged and repeated sampling used in decompression studies and is generally adequate to identify highly reflective gas bubbles. DUBD requires observers who have the aural skills (and aptitude) to identify and semi-quantify bubbles in the complex signals arising from blood flow and heart motion artifacts. Bubbles are usually graded with one of two common scales. Disparities in technician skill, technician bias, signal quality and the grading scales used create a degree of inherent subjectivity in grading. Automated detection and counting systems, whether hardware-based or software-driven, have long been desired but difficult to produce in a robust form. 2D echocardiography, on the other hand, can produce visual representations of bubbles, potentially more easily assessed with automated counting algorithms. It remains to be seen how such systems can address the confounding introduced by bubbles in the blood volume either not passing through or repeatedly passing through the imaging plane. Other major challenges are the estimation of bubble size and total gas volume when direct measurement is not available for confirmation. While dual frequency ultrasound holds potential for future bubble sizing (the first pulse excites bubbles of a diameter related to the ultrasound frequency and the second pulse identifies vibrating bubbles; a sweep of frequencies could identify a range of bubble sizes), the issues are complex. The shape of bubbles, for example, particularly larger bubbles, can be substantially distorted, potentially affecting size estimates. While current efforts can be valuable, any size and volume estimates must be considered very critically and with substantial restraint. A final practical challenge is the comparability of different methods of grading bubbles. While there has been some evaluation of sequential DUBD and 2D scans, such efforts have been completed with very few of the many devices available. Questions of comparability are likely to increase as technology evolves and resolution continues to improve. The evolution of 2D imaging has become apparent in recent reports documenting a greater than expected frequency of bubbles in the left heart. Classically, left heart bubbles have been associated with an elevated risk of serious decompression sickness (DCS) since they have bypassed pulmonary filtration and are about to be sent forth systemically; the jump in observations with current devices (in asymptomatic subjects) suggests that their impact in decompression stress likely requires a more nuanced assessment. While the relationship between bubbles and DCS is not simple, there is a clear association. Practically, bubbles occur far more frequently than DCS, sometimes following exposures that have very good safety records. The great utility of bubble assessment is likely to remain, not in determining absolute decompression risk, but in assessing relative decompression stress, in studies with a repeated measures design. Bubble studies can be useful in developing and validating dive tables and/or in evaluating and modifying dive profiles and procedures. Repeated-measures design is very important given the marked inter-individual variability in bubble expression. Intra-individual variability will remain a concern, moderated by the tightest controls feasible. In this issue, two papers consider 2D ultrasound systems to detect and quantify decompression stress. Blogg et al provide a review of the comparability of Doppler and 2D imaging technologies and evaluate the impact of harmonic processing and estimates of bubble load by obtaining paired 2D ultrasound images made using conventional and harmonic imaging. Germonpré et al look at 2D imaging procedures, bubble grading, statistical methodologies for determining inter- and intra-rater agreement, and how a frame-based bubble counting system can improve agreement. The framebased system allows bubbles to be treated as a continuous variable and may, perhaps, ultimately lead to computer-based algorithms for real-time analysis. A third paper in this issue, by Doolette et al, analyzes sample sizes required for sufficient statistical power to assess the differences in DCS risk between two decompression schedules when using observations of bubbles (that may have substantial variability) as an endpoint. Paired samples (from subjects monitored with 2D echocardiography) of different sizes were investigated. The considerations raised in this paper may provide guidance in estimating appropriate sample sizes for future studies using observed bubbles for comparison of different dive profiles. While these authors employed a somewhat novel scale, it is possible that the methods described can be applied as a general standard to a variety of scales. The common thread in these three papers is 2D imaging. They reflect a trend in decompression research towards a greater reliance on these techniques. Key benefits are their increased sensitivity and the ability to assess both sides of the heart. Still, despite these benefits, the relatively high cost of 2D systems and the extensive record of DUBD studies will undoubtedly keep DUBD technology in play, demanding ongoing attention to comparability.
- Ultrafast Doppler reveals the mapping of cerebral vascular resistivity in neonates. [JOURNAL ARTICLE]
- J Cereb Blood Flow Metab 2014 Mar 26.
In vivo mapping of the full vasculature dynamics based on Ultrafast Doppler is showed noninvasively in the challenging case of the neonatal brain. Contrary to conventional pulsed-wave (PW) Doppler Ultrasound limited for >40 years to the estimation of vascular indices at a single location, the ultrafast frame rate (5,000 Hz) obtained using plane-wave transmissions leads to simultaneous estimation of full Doppler spectra in all pixels of wide field-of-view images within a single cardiac cycle and high sensitivity Doppler imaging. Consequently, 2D quantitative maps of the cerebro-vascular resistivity index (RI) are processed and found in agreement with local measurements obtained on large arteries of healthy neonates using conventional PW Doppler. Changes in 2D resistivity maps are monitored during recovery after therapeutic whole-body cooling of full-term neonates treated for hypoxic ischemic encephalopathy. Arterial and venous vessels are unambiguously differentiated on the basis of their distinct hemodynamics. The high spatial (250 × 250 μm(2)) and temporal resolution (<1 ms) of Ultrafast Doppler imaging combined with deep tissue penetration enable precise quantitative mapping of deep brain vascular dynamics and RI, which is far beyond the capabilities of any other imaging modality.Journal of Cerebral Blood Flow & Metabolism advance online publication, 26 March 2014; doi:10.1038/jcbfm.2014.49.
- 2-D tracking Doppler: a new method to limit spectral broadening in pulsed wave Doppler. [Journal Article]
- IEEE Trans Ultrason Ferroelectr Freq Control 2013 Sep; 60(9):1896-905.
Transit time broadening is a major limitation in pulsed wave (PW) Doppler, especially when the angle between the flow direction and the ultrasound beam is large. The associated loss in frequency resolution may give severe overestimation of blood velocities, and finer details in the spectral display are lost. By using plane wave transmissions and parallel receive beamforming, multiple PW Doppler signals can be acquired simultaneously in a 2-D region. This enables tracking of the moving blood scatterers over a longer spatial distance to limit transit time broadening. In this work, the new method was tested using in vitro ultrasound recordings from a flow phantom, and in vivo recordings from a human carotid artery. The resulting 2-D tracking Doppler spectra showed significantly reduced spectral broadening compared with Doppler spectra generated by Welch's method. The reduction in spectral broadening was 4-fold when the velocity was 0.82 m/s and the beam-to-flow angle was 62°. A signal model was derived and the expected Doppler power spectra were calculated, showing good agreement with experimental data. Improved spectral resolution was shown for beam-to-flow angles between 40° and 82°.
- Doppler ultrasonographic assessment of maternal and fetal arteries during normal feline gestation. [Journal Article]
- Anim Reprod Sci 2014 Apr; 146(1-2):63-9.
The aim of this study was to describe Doppler parameters of uterine, umbilical, fetal abdominal aorta, fetal renal and fetal internal carotid arteries, as well as fetal heart rate (FHR), during normal feline gestation. Fifteen, 1-4 years of age, weighing 2.5-3.9kg, domestic short-hair pregnant queens, which were born in our institutional cat colony were included in this study. Color and pulsed-wave Doppler evaluations of uterine arteries were performed every 10 days (Day 0, 10, 20, 30, 40, 50, 60) from mating. Fetal Doppler and M-mode ultrasonography were performed to assess umbilical, fetal abdominal aorta, fetal renal, fetal internal carotid arteries and FHR. Both peak systolic velocity (PSV) and end diastolic velocity (EDV) of uterine artery increased up to parturition (P<0.01), while resistance index (RI) decreased from Day 10 onwards (P<0.01). From Day 40 onwards, RI of umbilical artery diminished, while PSV and EDV augmented (P<0.01). Fetal abdominal aorta (P<0.01), renal (P<0.01) and internal carotid (P<0.01) arteries diminished their RI from Days 40, 60 and 40 onwards, respectively. Both PSV and EDV of these three arteries increased progressively. Fetal heart rate was first registered on Day 20 when it began to increase up to Day 40 and then diminished to the end of gestation (P<0.01). It is concluded that blood flow of uterine, umbilical, fetal abdominal aorta, fetal renal and fetal internal carotid arteries progressively increased during normal feline pregnancy, while FHR rose to mid gestation and then decreased up to parturition.
- Left atrial mechanical functions in patients with anterior myocardial infarction: a velocity vector imaging-based study. [Controlled Clinical Trial, Journal Article]
- Kardiol Pol 2013; 71(12):1266-72.
The contribution of the left atrium (LA) to left ventricular (LV) function increases in myocardial infarction (MI).To evaluate LA function by using volume measurements and a novel strain imaging method, namely velocity vector imaging (VVI), in patients with acute anterior MI.Twenty-four patients with previous anterior MI (aged 63.8 ± 4.2 years, 56% men) and 30 healthy controls (aged 60.7 ± 5.3 years, 60% men) were enrolled. LA volume measurements and VVI-derived LA peak systolic strain (S), strain rate (SRs), early diastolic (ESRd) and late diastolic strain rate (LSRd) were measured. LV diastolic function was analysed by pulsed wave-Doppler and tissue velocity ımaging.LA maximum volume index was increased in patients compared to controls (28.83 ± 7.2 vs. 19.72 ± 6.27 mL/m²,p = 0.0001). As LA active emptying volume index and fraction were increased (6.16 ± 0.7 vs. 5.46 ± 0.99 mL/m², p = 0.009 and 22.16 ± 3.07 vs. 16.78 ± 2.93%, p = 0.0001, respectively), passive emptying volume index and fraction were decreased in the patient group (6.09 ± 0.57 vs. 7.57 ± 0.61 mL/m², p = 0.0001 and 45.76 ± 6.86 vs. 56.45 ± 5.36%, p = 0.0001, respectively). However, total emptying volume index of the LA was similar between the two groups. VVI-derived LA peak systolic S, SRs and ESRd were impaired in the patient group. LA LSRd was similar between the groups. LA active emptying fraction was positively correlated with LV diastolic dysfunction and negatively correlated with LV systolic dysfunction.We demonstrated increased LA booster function and decreased LA conduit and reservoir functions in patients with prior anterior MI. Improvement in LA booster function correlated with the degree of LV systolic and diastolic dysfunction, suggesting a compensatory response of the LA.
- Advanced echocardiography for the critical care physician: part 1. [Journal Article, Review, Video-Audio Media]
- Chest 2014 Jan; 145(1):129-34.
This is the first of a two-part series that reviews advanced critical care echocardiography (CCE) techniques designed for critical care physicians. In this section, we review training in basic and advanced CCE. This is followed by a review of Doppler principles, including pulsed wave, continuous wave, and color flow Doppler. Included are Doppler measurement techniques that are useful for assessing the patient with cardiopulmonary failure and the common pitfalls of Doppler. This section ends with a review of the quantitative and semiquantitative measurements of stroke volume, as well as problems with measurement of stroke volume in the ICU and its useful clinical applications. Video-based examples will help demonstrate the techniques that are described in the text.
- Limits of Spatial Resolution for Thermography and Other Non-destructive Imaging Methods Based on Diffusion Waves. [JOURNAL ARTICLE]
- Int J Thermophys 2013.:1617-1632.
In this work the measured variable, such as temperature, is a random variable showing fluctuations. The loss of information caused by diffusion waves in non-destructive testing can be described by stochastic processes. In non-destructive imaging, the information about the spatial pattern of a samples interior has to be transferred to the sample surface by certain waves, e.g., thermal waves. At the sample surface these waves can be detected and the interior structure is reconstructed from the measured signals. The amount of information about the interior of the sample, which can be gained from the detected waves on the sample surface, is essentially influenced by the propagation from its excitation to the surface. Diffusion causes entropy production and information loss for the propagating waves. Mandelis has developed a unifying framework for treating diverse diffusion-related periodic phenomena under the global mathematical label of diffusion-wave fields, such as thermal waves. Thermography uses the time-dependent diffusion of heat (either pulsed or modulated periodically) which goes along with entropy production and a loss of information. Several attempts have been made to compensate for this diffusive effect to get a higher resolution for the reconstructed images of the samples interior. In this work it is shown that fluctuations limit this compensation. Therefore, the spatial resolution for non-destructive imaging at a certain depth is also limited by theory.
- Correlation of myocardial performance index assessed by different echocardiographic methods in patients with acute myocard infarction receiving different reperfusion treatment. [Comparative Study, Journal Article]
- Minerva Med 2013 Dec; 104(6):593-604.
Myocardial performance index (MPI) is a well known prognostic parameter in acute myocardial infarction (AMI) patients, which has been used to assess global cardiac functions. In this study, we aimed to evaluate the corelation between the MPI levels obtained by PW doppler and Tissue doppler ultrasonography with reperfusion in AMI patients.Fifty-four consecutive acute ST elevatation myocardial infarction patients, 26 treated with primary percutaneous coronary intervention (PCI) and 28 with thrombolytic therapy (TT); and 15 consecutive healthy controls were included in the study. MPI levels were measured with pulsed-wave (PW) doppler and tissue Doppler ultrasonography in all patients. The isovolumic relaxation time (IVRT), isovolumic contraction time (IVCT) and ejection time (ET) values used to measure MPI levels were determined. Corelation between the time intervals obtained with both methods were evaluated. MPI variations were evaluated in patients treated with PCI and TT. A significant corelation was observed in MPI levels obtained with PW doppler and tissue doppler ultrasonography (P<0.001) as well as between IRT, ICT and ET values (for all parameters; P<0.001). No significant corelation was observed between the MPI levels obtained with PW doppler and tissue doppler ultrasonography in patients treated with primary PTCA and TT (P=0.128, P=0.991, respectively). A significant corelation was observed between the MPI values obtained by PW doppler and tissue doppler ultrasonography with reperfusion interval (P=0.002, P<0.001, respectively).As a result, tissue Doppler ultrasonography may be used as an alternative to PW doppler to evaluate MPI, which is a well known prognostic factor in AMI. No relation has been observed between MPI values in early phases of AMI with reperfusion pattern, while a connection has been observed between MPI and reperfusion interval.