Evaluation of the thyroid gland vascularity during pregnancy using 2-dimensional color Superb Microvascular Imaging vascularization index technique.

PURPOSE: We aimed to investigate maternal thyroid parenchymal vascularity with 2-dimensional color superb microvascular imaging vascularization index (2D-cSMIVI) levels and thyroid gland volume in the first, second and third trimesters. METHODS: This longitudinal prospective study was carried out with participants selected from 30 healthy asymptomatic pregnant women. Ultrasonography (US) for the thyroid gland was performed in each trimester. The vascularization index (VI) values obtained by manually drawing the contours of the thyroid parenchyma in the longutidinal plane, using the free region of interest (ROI) with 2DcSMIVI mode. VI values obtained in each trimester, thyroid hormone levels (TSH, T3, T4) and thyroid volumes were compared. RESULTS: We have detected that thyroid gland vascularity increased significantly as pregnancy progresses. The mean VI values of thyroid gland in third trimester were significantly higher than first and second trimester (p < 0.001), and the mean VI values of the thyroid gland in the second trimester were significantly higher than first trimester (p < 0.001). During pregnancy, we detected the increase in VI values, TSH levels and thyroid gland volumes. CONCLUSION: Maternal thyroid gland gray scale findings, parenchymal vascularization, thyroid volumes should be evaluated routinely for the healthy fetal development. 2D-cSMIVI method allows us to evaluate vascularization with quantitative numerical values objectively. We have detected that the VI values and volume of the thyroid gland increases as pregnancy progresses. In the complex situation of pregnancy process, the thyroid gland can be evaluated quantitatively with SMI method effectively.

First-trimester 3D power Doppler imaging markers of utero-placental vascular development are associated with placental weight and diameter at birth: The Rotterdam Periconception Cohort.

INTRODUCTION: Early utero-placental vascular development impacts placental development and function throughout pregnancy. We investigated whether impaired first-trimester utero-placental vascular development is associated with pathologic features of the postpartum placenta. METHODS: In this prospective observational study of 65 ongoing pregnancies, we obtained three-dimensional power Doppler ultrasounds of the placenta at 7, 9 and 11 weeks of gestation. We applied VOCAL software to measure placental volume (PV), virtual reality based segmentation to measure utero-placental vascular volume (uPVV) and applied a skeletonization algorithm to generate the utero-placental vascular skeleton (uPVS). Vascular morphology was quantified by assigning a morphologic characteristic to each voxel in the uPVS (i.e. end-, bifurcation-, crossing- or vessel point). Following delivery, placentas were measured and histologically examined according to the Amsterdam criteria to assess maternal vascular malperfusion (MVM). We used linear mixed models to estimate trajectories of PV, uPVV and uPVS development. Multivariable linear regression analysis with adjustments for confounders was used to evaluate associations between PV, uPVV and uPVS development and features of the postpartum placenta. RESULTS: We observed no associations between first-trimester PV development and measurements of the postpartum placenta. Increased first-trimester utero-placental vascular development, reflected by uPVV (ß = 0.25 [0.01; 0.48]), uPVS end points (ß = 0.25 [0.01; 0.48]), bifurcation points (ß = 0.22 [0.05; 0.37]), crossing points (ß = 0.29 [0.07; 0.52]) and vessel points (ß = 0.09 [0.02; 0.17]) was positively associated with the postpartum placental diameter. uPVV was positively associated with postpartum placental weight. No associations were found with MVM. DISCUSSION: Development of the first-trimester utero-placental vasculature is associated with postpartum placental size, whereas placental tissue development contributes to a lesser extent.

Competitive Swarm Optimized SVD Clutter Filtering for Ultrafast Power Doppler Imaging.

Ultrafast power Doppler imaging (uPDI) can significantly increase the sensitivity of resolving small vascular paths in ultrasound. While clutter filtering is a fundamental and essential method to realize uPDI, it commonly uses singular value decomposition (SVD) to suppress clutter signals and noise. However, current SVD-based clutter filters using two cutoffs cannot ensure sufficient separation of tissue, blood, and noise in uPDI. This article proposes a new competitive swarm-optimized SVD clutter filter to improve the quality of uPDI. Specifically, without using two cutoffs, such a new filter introduces competitive swarm optimization (CSO) to search for the counterparts of blood signals in each singular value. We validate the CSO-SVD clutter filter on public in vivo datasets. The experimental results demonstrate that our method can achieve higher contrast-to-noise ratio (CNR), signal-to-noise ratio (SNR), and blood-to-clutter ratio (BCR) than the state-of-the-art SVD-based clutter filters, showing a better balance between suppressing clutter signals and preserving blood signals. Particularly, our CSO-SVD clutter filter improves CNR by 0.99 ± 0.08 dB, SNR by 0.79 ± 0.08 dB, and BCR by 1.95 ± 0.03 dB when comparing a spatial-similarity-based SVD clutter filter in the in vivo dataset of rat brain bolus.

Clinical significance of three-dimensional power Doppler combined with two-dimensional Doppler ultrasonography for evaluating fetal growth restriction.

OBJECTIVES: To assess the predictive accuracy of three-dimensional (3D) power Doppler combined with two-dimensional (2D) Doppler ultrasonography in detecting fetal growth restriction (FGR). METHODS: The study was conducted on singleton pregnancies presenting for growth ultrasound examinations between 20 and 40 weeks of gestation. 63 patients with FGR were enrolled and matched 1:1.8 for gestational age with normal fetuses. Both groups were further divided into subgroups, with 32 weeks as the threshold-early-onset and late-onset FGR groups, and corresponding control groups. Conventional 2D Doppler parameters and standardized 3D power Doppler measurements of the placenta, including vascularization index (VI), flow index (FI), and vascularization-flow index (VFI) were obtained for each patient. RESULTS: (1) The average gestational weeks of delivery and birth weight of newborns in early-onset and late-onset FGR case groups were lower than those in control groups, while the incidence of placenta previa and adverse pregnancy outcomes were higher than those in control groups. (2) The biparietal diameter, head circumference, abdominal circumference, femur length, estimated fetal weight, middle cerebral artery systolic/diastolic velocity ratio (S/D), pulsatility index (PI), resistance index (RI), and placental blood perfusion indices of vascular index (VI), flow index (FI), vascular flow index (VFI), and cerebro-placental ratio (CPR) of the early-onset and late-onset FGR case groups were all lower than those of the control group. Moreover, the S/D, PI, and RI of the umbilical and uterine arteries were higher than those of the corresponding control group. (3) For early-onset FGR, the area under the curve (AUC) of the umbilical artery PI was the largest (0.861), exhibiting the highest predictive value. When combined with the placental blood perfusion index, the AUC was 0.789. For late-onset FGR, the AUC of the CPR was 0.861. After integrating the placental blood perfusion index, the AUC increased to 0.877. The positive likelihood ratio (PLR) of combined 2D Doppler indexes (21.938) and negative likelihood ratio (NLR) of VFI (0.565) were the highest in the early-onset FGR group. The PLR of combined 3D Doppler indexes (8.536) and NLR of VFI (0.557) were the highest in the late-onset FGR group. CONCLUSIONS: The combination of 3D Doppler indices with 2D Doppler ultrasonography demonstrated superior predictive value in diagnosing late-onset FGR compared to other conventional indicators. The 3D Dower index, VFI, has a good true-negative predictive value for both early- and late-onset FGR.

Ultrafast Doppler Imaging for Early Detection of Synovitis in Rheumatoid Arthritis.

OBJECTIVE: Current medical ultrasound systems possess limited sensitivity in detecting slow and weak blood flow during the early stages of rheumatoid arthritis (RA), leading to potential misdiagnosis. Ultrafast Doppler is capable of detecting slow and weak flow. This study was aimed at evaluating the diagnostic value of ultrafast Doppler for RA. METHODS: Thirty-three RA patients (19 established, 14 early stage) and 15 healthy participants were enrolled. A programmable imaging platform with ultrafast Doppler capability was used. The benchmark was a clinical system with conventional Doppler imaging. Standardized dorsal long-axis scanning of both wrists was performed. Both ultrafast and conventional power Doppler (PD) images were quantitatively analyzed with computer assistance and semiquantitatively scored with the Outcome Measures in Rheumatology (OMERACT) scoring system. RESULTS: Ultrafast PD revealed more blood area than conventional PD in both RA wrists and healthy wrists. Ultrafast PD OMERACT was positive in 65 of 66 RA wrists and 26 of 30 healthy wrists (sensitivity [SEN] = 0.985, accuracy [ACC] = 0.719), while conventional PD OMERACT was positive in 28 of 66 RA wrists and 0 of 30 healthy wrists (SEN = 0.424, ACC = 0.604). Ultrafast PD revealed a higher synovial PD area, dilated vessels and PD brightness in RA wrists. Peak synovial PD brightness had the best diagnostic value for RA (area under the receiver operating characteristic curve = 0.802, SEN = 0.909, ACC = 0.813). For early-stage RA patients, ultrafast peak synovial PD brightness had higher sensitivity and accuracy than conventional PD indexes. CONCLUSION: Ultrafast PD had an increase of 0.561 in sensitivity and 0.209 in accuracy when compared with conventional PD. With its high sensitivity, ultrafast PD can detect early synovitis and identify RA patients during the early phase.

Detection of Individual Microbubbles by Burst-Wave-Aided Contrast-Enhanced Active Doppler Ultrasonography.

We propose burst-wave-aided, contrast-enhanced, active Doppler ultrasonography for visualizing lymph vessels. This technique forces ultrasound contrast agents (UCAs) to move using the acoustic radiation force induced by burst waves with low amplitude while suppressing their destruction. Using a flow phantom, we measured the average, decrease rate of echo intensity [i.e., pulse intensity integral (PII)], and the velocity of individual contrast agents, which directly affects the performance of imaging and tracking contrast agents under stationary flow conditions. Comparison with pulse-inversion Doppler without exposure to the burst wave demonstrated that the velocity of the contrast agents could be enhanced up to several tens of millimeters per second by the effect of the burst wave, maximizing the echo intensity extracted by a clutter filter. The contrast ratio (CR), defined as the ratio of the contrast echo to the phantom echo outside the channel, did not change appreciably, even when the lower cut-off velocity of the clutter filter was increased up to 10 mm/s. This implies a better robustness against the motion of the tissue. In addition, the performance for detecting contrast agents (i.e., echo intensity) was superior or similar to that of pulse-inversion Doppler, even in undesirable conditions where the flow had a velocity component in the opposite direction to that of the acoustic radiation force. The echo intensity was lower or the same as that in pulse-inversion Doppler, demonstrating the potential for suppressing the destruction of contrast agents and enabling long-term observations. From these results, we expect that the proposed method will be beneficial for visualizing lymph vessels.

Fetal aortic isthmus Doppler assessment to predict the adverse perinatal outcomes associated with fetal growth restriction: systematic review and meta-analysis.

PURPOSE: Fetal growth restriction (FGR) management and delivery planning is based on a multimodal approach. This meta-analysis aimed to evaluate the prognostic accuracies of the aortic isthmus Doppler to predict adverse perinatal outcomes in singleton pregnancies with FGR. METHODS: PubMed, EMBASE, the Cochrane Library, ClinicalTrials.gov and Google scholar were searched from inception to May 2021, for studies on the prognostic accuracy of anterograde aortic isthmus flow compared with retrograde aortic isthmus flow in singleton pregnancy with FGR. The meta-analysis was registered on PROSPERO and was assessed according to PRISMA and Newcastle-Ottawa Scale. DerSimonian and Laird's random-effect model was used for relative risks, Freeman-Tukey Double Arcsine for pooled estimates and exact method to stabilize variances and CIs. Heterogeneity was quantified using I2 statistics. RESULTS: A total of 2933 articles were identified through the electronic search, of which 6 studies (involving 240 women) were included. The quality evaluation of studies revealed an overall acceptable score for study group selection and comparability and substantial heterogeneity. The risk of perinatal death was significantly greater in fetuses with retrograde Aortic Isthmus blood flow, with a RR of 5.17 (p value 0.00001). Similarly, the stillbirth rate was found to have a RR of 5.39 (p value 0.00001). Respiratory distress syndrome had a RR of 2.64 (p value = 0.03) in the group of fetuses with retrograde Aortic Isthmus blood flow. CONCLUSION: Aortic Isthmus Doppler study may add information for FGR management. However, additional clinical trial are required to assess its applicability in clinical practice.

Automatic Max-Likelihood Envelope Detection Algorithm for Quantitative High-Frame-Rate Ultrasound for Neonatal Brain Monitoring.

OBJECTIVE: Post-operative brain injury in neonates may result from disturbed cerebral perfusion, but accurate peri-operative monitoring is lacking. High-frame-rate (HFR) cerebral ultrasound could visualize and quantify flow in all detectable vessels using spectral Doppler; however, automated quantification in small vessels is challenging because of low signal amplitude. We have developed an automatic envelope detection algorithm for HFR pulsed wave spectral Doppler signals, enabling neonatal brain quantitative parameter maps during and after surgery. METHODS: HFR ultrasound data from high-risk neonatal surgeries were recorded with a custom HFR mode (frame rate = 1000 Hz) on a Zonare ZS3 system. A pulsed wave Doppler spectrogram was calculated for each pixel containing blood flow in the image, and spectral peak velocity was tracked using a max-likelihood estimation algorithm of signal and noise regions in the spectrogram, where the most likely cross-over point marks the blood flow velocity. The resulting peak systolic velocity (PSV), end-diastolic velocity (EDV) and resistivity index (RI) were compared with other detection schemes, manual tracking and RIs from regular pulsed wave Doppler measurements in 10 neonates. RESULTS: Envelope detection was successful in both high- and low-quality arterial and venous flow spectrograms. Our technique had the lowest root mean square error for EDV, PSV and RI (0.46 cm/s, 0.53 cm/s and 0.15, respectively) when compared with manual tracking. There was good agreement between the clinical pulsed wave Doppler RI and HFR measurement with a mean difference of 0.07. CONCLUSION: The max-likelihood algorithm is a promising approach to accurate, automated cerebral blood flow monitoring with HFR imaging in neonates.

Evaluation of placenta in patients with gestational diabetes using shear wave elastography and superb microvascular imaging.

BACKGROUND: Gestational diabetes mellitus (GDM) is a common disease, and the placenta shows various functional and morphological changes in these patients. Superb microvascular imaging (SMI) and shear wave elastography (SWE) are innovative ultrasound (US) methods that provide detailed information about tissue vascularization and elasticity. PURPOSE: To evaluate placental changes in patients with GDM with SMI and SWE methods. MATERIAL AND METHODS: For this case-control study, 20 healthy and 20 women with GDM were included. Women at >21 weeks of pregnancy were evaluated with SMI and SWE by two independent radiologists. Mean SMI values and mean SWE values from three different region of interest-based measurements were compared between the two groups. RESULTS: We identified that the mean SMI and SWE value ​​of the GDM group was found to be significantly higher than that of the control group (P = 0.002, P = 0.001 respectively). Using a receiver operating characteristic curve, the cutoff value of the SMI ratio, which maximizes the prediction of the presence of GDM, was 0.1234279750 (95% confidence interval [CI] = 0.625-0.920), the SWE cut-off value was 15.5 kPa (95% CI = 0.794-0.989). CONCLUSION: We have demonstrated that evaluation with SMI and SWE might allow quantitative assessment of the morphological changes of placentas in women with GDM. We believe that the use of innovative methods such as SMI and SWE in addition to conventional US examinations in daily practice and studies will provide significant clinical benefits to patient management.

Clutter filtering of angular domain data for contrast-free ultrafast microvascular imaging.

Objective. Contrast-free microvascular imaging is clinically valuable for the assessment of physiological status and the early diagnosis of diseases. Effective clutter filtering is essential for microvascular visualization without contrast enhancement. Singular value decomposition (SVD)-based spatiotemporal filter has been widely used to suppress clutter. However, clinical real-time imaging relies on short ensembles (dozens of frames), which limits the implementation of SVD filtering due to the large error of eigen-correlated estimations and high dependence on optimal threshold when used in such ensembles.Approach. To address the above challenges of imaging in short ensembles, two optimized filters of angular domain data are proposed in this paper: grouped angle SVD (GA-SVD) and angular-coherence-based higher-order SVD (AC-HOSVD). GA-SVD applies SVD to the concatenation of all angular data to improve clutter rejection performance in short ensembles, while AC-HOSVD applies HOSVD to the angular data tensor and utilizes angular coherence in addition to spatial and temporal features for filtering. Feasible threshold selection strategies in each feature space are provided. The clutter rejection performance of the proposed filters and SVD was evaluated with Doppler phantom andin vivostudies at different cases. Moreover, the robustness of the filters was explored under wrong singular value threshold estimation, and their computational complexity was studied.Main results. Qualitative and quantitative results indicated that GA-SVD and AC-HOSVD can effectively improve clutter rejection performance in short ensembles, especially AC-HOSVD. Notably, the proposed methods using 20 frames had similar image quality to SVD using 100 frames.In vivostudies showed that compared to SVD, GA-SVD increased the signal-to-noise-ratio (SNR) by 6.03 dB on average, and AC-HOSVD increased the SNR by 8.93 dB on average. Furthermore, AC-HOSVD remained better power Doppler image quality under non-optimal thresholds, followed by GA-SVD.Significance. The proposed filters can greatly enhance contrast-free microvascular visualization in short ensembles and have potential for different clinical translations due to the performance differences.

A Robust Approach Assisted by Signal Quality Assessment for Fetal Heart Rate Estimation from Doppler Ultrasound Signal.

Fetal heart rate (FHR) monitoring, typically using Doppler ultrasound (DUS) signals, is an important technique for assessing fetal health. In this work, we develop a robust DUS-based FHR estimation approach complemented by DUS signal quality assessment (SQA) based on unsupervised representation learning in response to the drawbacks of previous DUS-based FHR estimation and DUS SQA methods. We improve the existing FHR estimation algorithm based on the autocorrelation function (ACF), which is the most widely used method for estimating FHR from DUS signals. Short-time Fourier transform (STFT) serves as a signal pre-processing technique that allows the extraction of both temporal and spectral information. In addition, we utilize double ACF calculations, employing the first one to determine an appropriate window size and the second one to estimate the FHR within changing windows. This approach enhances the robustness and adaptability of the algorithm. Furthermore, we tackle the challenge of low-quality signals impacting FHR estimation by introducing a DUS SQA method based on unsupervised representation learning. We employ a variational autoencoder (VAE) to train representations of pre-processed fetal DUS data and aggregate them into a signal quality index (SQI) using a self-organizing map (SOM). By incorporating the SQI and Kalman filter (KF), we refine the estimated FHRs, minimizing errors in the estimation process. Experimental results demonstrate that our proposed approach outperforms conventional methods in terms of accuracy and robustness.

Wavelet Scattering Transform based Doppler signal classification.

Normal blood supply to the human brain may be marred by the presence of a clot inside the blood vessels. This clot structure called emboli inhibits normal blood flow to the brain. It is considered as one of the main sources of stroke. Presence of emboli in human's can be determined by the analysis of transcranial Doppler signal. Different signal processing and machine learning algorithms have been used for classifying the detected signal as an emboli, Doppler speckle, and an artifact. In this paper, we sought to make use of the wavelet transform based algorithm called Wavelet Scattering Transform, which is translation invariant and stable to deformations for classifying different Doppler signals. With its architectural resemblance to Convolutional Neural Network, Wavelet Scattering Transform works well on small datasets and subsequently was trained on a dataset consisting of 300 Doppler signals. To check the effectiveness of extracted Scattering transform based features for Doppler signal classification, learning algorithms that included multi-class Support vector machine, k-nearest neighbor and Naive Bayes algorithms were trained. Comparative analysis was done with respect to the handcrafted Continuous wavelet transform features extracted from samples and Wavelet scattering with Support vector machine achieved an accuracy of 98.89%. Also, with set of extracted scattering coefficients, Gaussian process regression was performed and a regression model was trained on three different sets of scattering coefficients with zero order scattering coefficients providing least prediction loss of 34.95%.

Pregnancy prediction via ultrasound-detected endometrial blood for hormone replacement therapy-frozen embryo transfer: a prospective observational study.

BACKGROUND: This study aimed to assess the predictive value of endometrial blood flow branches on pregnancy outcomes after hormone replacement therapy-frozen embryo transfer (HRT-FET). METHODS: This prospective observational study involved 292 reproductive-aged women who underwent endometrial receptivity assessment in a tertiary care academic medical center in southwest China using power Doppler ultrasonography during HRT-FET. Three-dimensional power Doppler ultrasound was performed on the day of endometrial transformation and the day before embryo transfer. The endometrial blood flow branches of the endometrial and subendometrial regions were compared in the non-pregnant and pregnant groups at the two time points mentioned above. RESULTS: The endometrial blood flow branches were higher in pregnant patients than in non-pregnant patients on the day of endometrial transformation (P = 0.009) and the day before embryo transfer (P = 0.001). Changes in endometrial blood flow pattern and endometrial blood flow branches at the two time points did not differ among the pregnancy outcome samples. After adjusting for age, antral follicles, and embryos transferred, the endometrial blood flow branches on the day before embryo transfer was the independent factor influencing the chance of clinical pregnancy, with an odds ratio of 3.001 (95% confidence interval: 1.448 - 6.219, P = 0.003). CONCLUSIONS: Endometrial blood flow perfusion during the peri-transplantation period of the HRT-FET cycle is a good indicator of pregnancy outcomes, suggesting that valuation of endometrial branches via power Doppler ultrasound is a simple and effective approach for achieving indicator measurements.

Optimal timing of delivery for growth restricted fetuses with gastroschisis: A decision analysis.

OBJECTIVE: Our objective was to determine the optimal timing of delivery of growth restricted fetuses with gastroschisis in the setting of normal umbilical artery (UA) Dopplers. METHODS: We designed a decision analytic model using TreeAge software for a hypothetical cohort of 2000 fetuses with isolated gastroschisis, fetal growth restriction (FGR), and normal UA Dopplers across 34-39 weeks of gestation. This model accounted for costs and quality adjusted life years (QALYs) for the pregnant individual and the neonate. Model outcomes included stillbirth, respiratory distress syndrome (RDS), necrotizing enterocolitis (NEC), intraventricular hemorrhage (IVH), short gut syndrome (SGS), neonatal sepsis, neonatal death, and neurodevelopmental disability (NDD). RESULTS: We found 38 weeks to be the optimal timing of delivery for minimizing overall perinatal mortality and leading to the highest total QALYs. Compared to 37 weeks, delivery at 38 weeks resulted in 367.98 more QALYs, 2.22 more cases of stillbirth, 2.41 fewer cases of RDS, 0.02 fewer cases of NEC, 1.65 fewer cases of IVH, 0.5 fewer cases of SGS, 2.04 fewer cases of sepsis, 11.8 fewer neonatal deaths and 3.37 fewer cases of NDD. However, 39 weeks were the most cost-effective strategy with a savings of $1,053,471 compared to 38 weeks. Monte Carlo analysis demonstrated that 38 weeks was the optimal gestational age for delivery 51.70% of the time, 39 weeks were optimal 47.40% of the time, and 37 weeks was optimal 0.90% of the time. CONCLUSION: Taking into consideration a range of adverse perinatal outcomes and cost effectiveness, 38-39 weeks gestation is ideal for the delivery of fetuses with gastroschisis, FGR, and normal UA Dopplers. However, there are unique details to consider for each case, and the timing of delivery should be individualized using shared multidisciplinary decision making.

Contrast Agent-Free 3D Renal Ultrafast Doppler Imaging Reveals Vascular Dysfunction in Acute and Diabetic Kidney Diseases.

To combat the irreversible decline in renal function associated with kidney disease, it is essential to establish non-invasive biomarkers for assessing renal microcirculation. However, the limited resolution and/or vascular sensitivity of existing diagnostic imaging techniques hinders the visualization of complex cortical vessels. Here, a 3D renal ultrafast Doppler (UFD) imaging system that uses a high ultrasound frequency (18 MHz) and ultrahigh frame rate (1 KHz per slice) to scan the entire volume of a rat's kidney in vivo is demonstrated. The system, which can visualize the full 3D renal vascular branching pyramid at a resolution of 167 µm without any contrast agent, is used to chronically and noninvasively monitor kidneys with acute kidney injury (AKI, 3 days) and diabetic kidney disease (DKD, 8 weeks). Multiparametric UFD analyses (e.g., vessel volume occupancy (VVO), fractional moving blood volume (FMBV), vessel number density (VND), and vessel tortuosity (VT)) describe rapid vascular rarefaction from AKI and long-term vascular degeneration from DKD, while the renal pathogeneses are validated by in vitro blood serum testing and stained histopathology. This work demonstrates the potential of 3D renal UFD to offer valuable insights into assessing kidney perfusion levels for future research in diabetes and kidney transplantation.

Adjunctive technologies in postoperative free-flap monitoring: a systematic review.

Patent microvascular anastomoses are essential for successful free tissue transfer. Early accurate detection of microvascular compromise is required for flap salvage. Adjunctive monitoring techniques, in addition to clinical examination, are increasingly used to detect flap compromise. This systematic review synthesized and appraised the literature to determine the efficacy of different postoperative monitoring technologies. Rates of flap takeback, salvage, failure, and mean time to detection of microvascular compromise were extracted, synthesized, and reviewed. Twenty-two studies were included, comprising 6370 flaps. One thousand three hundred and ninety-five flaps were monitored with Cook Swartz Doppler (21.83%), 1417 flaps with tissue oximetry (22.24%), 291 with laser Doppler (4.56%), 175 with duplex echography (2.74%), 210 with indocyanine green (ICG) fluorescence (3.30%), 196 with Synovis flow coupler (3.07%), and 81 (1.27%) with light spectroscopy. The overall true positive rate for microvascular compromise in taken back flaps was 70.18%. Cook Swartz Doppler (n = 1391) had a true positive rate of 80.17% and 83.63% salvage rate and was associated with an overall 2.60% rate of flap failure. Tissue oximetry (n = 1417) had a true positive rate of 74.76% and a salvage rate of 88.62%. Laser Doppler, duplex echography, light spectroscopy, and Synovis flow coupler demonstrated true positive rates between 69.4% and 100% with salvage rates between 64% and 100%. Cook Swartz Doppler and tissue oximetry are associated with prompt identification of microvascular compromise and return to theatre. Alternative modalities, including near-infrared spectroscopy, laser Doppler, and duplex echography, show promise. Further well-designed randomised controlled trials (RCTs) appraising head-to-head efficacy are required to comparatively assess adjunctive technologies.

Ultra-fast ultrasound blood flow velocimetry for carotid artery with deep learning.

Accurate measurement of blood flow velocity is important for the prevention and early diagnosis of atherosclerosis. However, due to the uncertainty of parameter settings, the autocorrelation velocimetry methods based on clutter filtering are prone to incorrectly filter out the near-wall blood flow signal, resulting in poor velocimetric accuracy. In addition, the Doppler coherent compounding acts as a low-pass filter, which also leads to low values of blood flow velocity estimated by the above methods. Motivated by this status quo, here we propose a deep learning estimator that combines clutter filtering and blood flow velocimetry based on the adaptive property of one-dimensional convolutional neural network (1DCNN). The estimator is operated by first extracting the blood flow signal from the original Doppler echo signal through an affine transformation of the 1D convolution, and then converting the extracted signal into the desired blood flow velocity using a linear transformation function. The effectiveness of the proposed method is verified by simulation as well as in vivo carotid artery data. Compared with typical velocimetry methods such as high-pass filtering (HPF) and singular value decomposition (SVD), the results show that the normalized root means square error (NRMSE) obtained by 1DCNN is reduced by 54.99 % and 53.50 % for forward blood flow velocimetry, and 70.99 % and 69.50 % for reverse blood flow velocimetry, respectively. Consistently, the in vivo measurements demonstrate that the goodness-of-fit of the proposed estimator is improved by 8.72 % and 4.74 % for five subjects. Moreover, the estimation time consumed by 1DCNN is greatly reduced, which costs only 2.91 % of the time of HPF and 12.83 % of the time of SVD. In conclusion, the proposed estimator is a better alternative to the current blood flow velocimetry, and is capable of providing more accurate diagnosis information for vascular diseases in clinical applications.

Swept-3-D Ultrasound Imaging of the Mouse Brain Using a Continuously Moving 1-D-Array-Part I: Doppler Imaging.

Volumetric 3-D Doppler ultrasound imaging can be used to investigate large scale blood dynamics outside of the limited view that conventional 2-D power Doppler images (PDIs) provide. To create 3-D PDIs, 2-D-matrix array transducers can be used to insonify a large volume for every transmission; however, these matrices suffer from low sensitivity, high complexity, and high cost. More typically, a 1-D-array transducer is used to scan a series of stationary 2-D PDIs, after which a 3-D volume is created by concatenating the 2-D PDIs in postprocessing, which results in long scan times due to repeated measurements. Our objective was to achieve volumetric 3-D Doppler ultrasound imaging with a high Doppler sensitivity, similar to that of a typical stationary recording using a 1-D-array transducer, while being more affordable than using 2-D-matrix arrays. We achieved this by mounting a 1-D-array transducer to a high-precision motorized linear stage and continuously translating over the mouse brain in a sweeping manner. For Part I of this article, we focused on creating the best vascular images by investigating how to best combine filtered beamformed ultrasound frames, which were not acquired at the same spatial locations, into PDIs. Part II focuses on the implications of sampling transient brain hemodynamics through functional ultrasound (fUS) while continuously translating over the mouse brain. In Part I, we show how the speed at which we sweep our 1-D-array transducer affects the Doppler spectrum in a flow phantom. In vivo recordings were performed on the mouse brain while varying the sweeping speed, showing how higher sweeping speeds negatively affect the PDI quality. A weighting vector is found to combine frames while continuously moving over the mouse brain, allowing us to create swept PDIs of similar sensitivity when compared with those obtained using a stationary 1-D-array while allowing a significantly higher 3-D Doppler volume rate and maintaining the benefits of having a low computational and monetary cost. We show that a vascular subvolume of 6 mm can be scanned in 2.5 s, with a PDI reconstructed every [Formula: see text], outperforming classical staged recording methods.

Cerebral Microvascular Imaging in Infants: Scan Technique and Potential Clinical Applications.

ABSTRACT: Brain ultrasound in infants, although widely utilized, provides limited functional insights into the brain. Although color and power Doppler ultrasounds have allowed quantitative assessment of cerebral macrovascular flow dynamics, there is no standardized tool integrated into the current neurosonography protocol that allows cerebral microvascular flow assessment. The evaluation of anatomic and functional changes in cerebral microvessels is important, as microvascular alterations have been shown to precede macrovascular and tissue injury in a variety of neurologic diseases of infancy. In this regard, the cerebral microvascular imaging technique is a commercially available, advanced Doppler technique in which slow flow of cerebral microvessels can be detected via a static noise suppression algorithm. This article therefore shares the basic scan technique and clinical examples of the integrated use of microvascular imaging in neurosonography for infants, setting the stage for future clinical integration of the technique.

Optimización de la exploración eco Doppler mediante la manipulación de los controles del equipo (knobology); primera parte / Doppler ultrasound exploration optimization by manipulating the controls of the equipment: knobology; part one

La ecografía Doppler es una modalidad diagnóstica dependiente de un operador indispensable por disponibilidad, eficacia y costes. además de conocimientos anatómicos y clínicos, exige un mínimo conocimiento de sus principios físicos y tecnológicos. Conocer, practicar, ajustar las funciones del eco Doppler de forma ordenada y en función del paciente y de la exploración indicada harán que nuestras exploraciones sean más sencillas, rápidas, seguras y precisas. este artículo de formación intenta repasar y esquematizar cómo ajustar las principales aplicaciones del equipo mediante los botones y controles del dispositivo ("knobology").(AU)

doppler ultrasound is an operator-dependent diagnostic modality, essential due to its availability, efficacy and costs.in addition to anatomical and clinical knowledge, it requires a minimum knowledge of its physical and technologicalprinciples. the knowledge, training, and set up the functions of the duplex scan in a properly way depending onthe patient and kind of exploration, will make our examinations easier, faster, safer, and more precise. this papertries to review and outline how to adjust the main applications of the equipment using the buttons and controlsof the device (knobology).(AU)