High Doppler Research Articles

Management of large placental chorioangioma: two-port laser approach for fetal intervention.

There is a paucity of literature providing evidence-based guidelines for the management of large placental chorioangioma (≥ 4 cm in diameter). The objectives of this study were to compare outcomes between patients managed expectantly and those undergoing in-utero intervention and to describe the different in-utero techniques used for cessation of blood flow to the tumor and the associated outcome. This was a retrospective cohort study of 34 patients referred for the management of large placental chorioangioma in a single center between January 2011 and December 2022, who were managed expectantly or underwent in-utero intervention. In-utero intervention was performed when the fetus developed any signs of impending compromise, including high combined cardiac output (CCO), worsening polyhydramnios or abnormal fetal Doppler velocimetry findings. Interventions included radiofrequency ablation (RFA), interstitial laser ablation (ILA) and single-port or two-port fetoscopic laser photocoagulation (FLP). Treatment selection was dependent on the proximity of the tumor to the umbilical cord insertion (UCI) and placental location. The two-port technique was performed in patients with a chorioangioma with large feeding vessels (≥ 3 mm) located in the posterior placenta, in which one port was used for occlusion using bipolar forceps and the other port was used for laser photocoagulation of the feeding vessels downstream. The single-port technique was used for chorioangioma with small feeding vessels (< 3 mm) located in the posterior placenta. ILA or RFA was performed in cases with an anterior placenta. Supportive treatments, including amnioreduction and intrauterine transfusion (IUT), were performed for worsening polyhydramnios and suspected fetal anemia based on middle cerebral artery Doppler flow studies, respectively. Comparative statistical analysis between cases undergoing expectant management vs in-utero intervention was performed. Descriptive details were provided for patients who underwent in-utero intervention. Thirty-four cases of large chorioangioma were evaluated, of which 25 (73.5%) were managed expectantly and nine (26.5%) underwent intervention. The frequency of polyhydramnios was significantly higher in the intervention group compared with the expectant-management group (66.7% vs 8.0%, P < 0.001). The live-birth rate among expectantly managed cases with large chorioangioma was significantly higher compared with that in cases that underwent in-utero intervention (96.0% vs 62.5%, P = 0.01). In the intervention group, preoperative CCO was elevated in all cases with available information and preoperative hydrops was present in 33.3% (3/9) of cases. One patient experienced fetal demise following IUT prior to planned FLP. Among the remaining eight patients, four underwent two-port FLP, two underwent single-port FLP, one underwent ILA and one underwent both ILA and RFA. All three cases in which hydrops was present at the time of intervention resulted in fetal demise. In-utero interventions aimed at cessation of blood flow in the feeding vessels are a therapeutic option for the management of cases with large chorioangioma. The two-port percutaneous technique appears to improve the efficiency of FLP when a large chorioangioma with large feeding vessels is located in the posterior placenta. We propose that in-utero interventions for large chorioangioma should be initiated prior to the development of fetal hydrops. © 2023 International Society of Ultrasound in Obstetrics and Gynecology.

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.

Reconfigurable-Intelligent-Surface-Aided OTFS: Transmission Scheme and Channel Estimation

In this paper, we study the uplink transmission scheme and channel estimation design for reconfigurable intelligent surfaces (RIS)-aided orthogonal time frequency space (OTFS) systems in high-mobility scenarios. To this end, we first propose an efficient and reliable transmission scheme which utilizes the delay-Doppler information in OTFS to facilitate the configuration of RIS. Specifically, the proposed scheme exploits the estimated delay and Doppler shifts of the cascaded channel to sense the channel parameters, and the sensing parameters are then used for RIS passive beamforming. It is noteworthy that we estimate the channel state information (CSI) by employing only one OTFS frame and configure the RIS based on the predicted channel parameters, leading to substantially reduced channel training overhead and more real-time RIS configuration. To obtain the essential information for channel information sensing, we then propose a low-complexity algorithm which determines the Doppler and delay shifts of the channel between the user and RIS based on linear systems and the mapping relationship of the delay-Doppler pairs, respectively. With the delay-Doppler information in hand, a user localization algorithm constructed by the least square (LS) and a channel tracking method relying on extended Kalman filter (EKF) are then presented to obtain the spatial angle information. By making use of the channel parameters acquired at the base station (BS), the RIS reflection vector is designed to maximize the achievable rate. The results obtained from the simulation experiments affirm the efficacy of the proposed scheme, thereby confirming its capability to attain efficient communications under high Doppler channels.

Age of Onset of High Transcranial Doppler Measurements Predicts Discrepant Cognitive Profiles in Children with Sickle Cell Disease

Background: Children with Sickle Cell Disease (SCD) have documented compromises in neurocognitive functioning, with notable weaknesses in executive functioning. There is limited published research to define the impact of SCD on the development of visual spatial processing, which is the brain's ability to use and interpret visual stimuli and then apply it to novel situations. We hypothesized that the risk for deficits in visual spatial processing is correlated to high velocity transcranial dopplers (TCD) measurements and the age at which a high TCD velocity first occurred. Our team hypothesized that younger age at time of initial high TCD is associated with a larger impact on visual spatial skills in school aged children. Methods: This review includes data from standard of care practices within our pediatric multidisciplinary sickle cell program. Our clinic began offering neurocognitive screenings in January 2023 to patients who are school entry age (between 5 to 6 years old) or older. Children are identified to participate in screening based on age, parental interest, and provider recommendation. Patients ranging in age from 5 to 15 years of age were screened using either the Weschler Preschool and Primary Scale of Intelligence, fourth edition (WPPSI-IV) or the Wechsler Intelligence Scale for Children, fifth edition (WISC-V). Retrospective chart reviews were performed to identify relevant data including TCD and MRI results. The Visual Spatial Index (VSI) is a primary index obtained from the Wechsler standard batteries. VSI assesses a child's ability to construct designs utilizing visual spatial reasoning, attention to visual detail, and visual-motor integration. The average child can demonstrate these skills at age 5 by mentally rotating an object such as a block and matching it with a picture or into a shaped hole. This requires the appropriate development of the basal ganglia, thalamus, parietal lobe, and temporal lobe. The Mean Index Score (MIS) is a broad representation of all cognitive domains measured on the assessment. The difference between the obtained VSI score and a child's MIS is used to determine whether a statistically significant difference exists within the Wechsler assessment system. The difference between the VSI and MIS is compared to a critical value, and if the difference of the VSI and MIS is greater than the critical value then we can say with confidence (p&amp;lt;0.05) that the difference in scores is not due to chance. Chi-square was then used to explore the relationship between the presence of a high TCD before age 5 (the age at which primary visual spatial skills are onboard) and the presence of a statistically significant visual spatial skill weakness. Results: 11 children (mean age 9.73 years; 82% Hemoglobin SS and 18% Hemoglobin SC) were assessed during the first 6 months of this new protocol. 27% (3) of the children had both a high TCD prior to age 5 and a statistically significant (p&amp;lt;0.05) visual spatial weakness, 9% (1) had only high TCD before age 5 but not VSI weakness, and 64% (7) had neither. Due to the small sample size, we used Fisher's exact to test the hypothesis that these two categorical variables (high TCD velocity before age 5 and VSI weakness) were related (P&amp;lt;0.05, P=0.024). We rejected the null hypothesis and found evidence to support a relationship between the presence of high velocities in early childhood and visual spatial skills deficit. Therefore, there is clinical indication that high TCD velocities in early childhood impact the development of visual spatial skills. Conclusion: The impact of sickle cell disease on brain development has been explored, but most published data focus on broad executive functioning skills. Our data yields evidence that the presence of high velocities in the brain before age five may be predictive of future visual spatial abilities as measured using standardized measures (i.e., Wechsler Assessments). It is anticipated that further data exploration will inform the optimization of standard of care practices within our clinic. This may include medical practices such as neuroimaging, changing how we communicate with children and their families, and enhanced practices for supporting students at school through IEPs.

The Accuracy and Reliability of Automated Oscillometric Measurement of Ankle-Brachial Index in the Diagnosis of Peripheral Artery Disease

Comparing the accuracy and reliability of ankle-brachial index (ABI) measured by an oscillometric device with the Doppler method in peripheral arterial disease (PAD). 122 patients admitted to the department of interventional radiology with PAD were studied. ABI was measured with the 2 methods in random order. After excluding the inconclusive results, Doppler ABIs were compared with the oscillometric ABIs in each limb, the reliability was evaluated by intraclass correlation coefficient (ICC), and the accuracy and consistency were assessed by receiver operating characteristic curves and Bland-Altman method. In 122 patients (244 legs), 27 legs got inconclusive oscillometric results, 4 legs got inconclusive oscillometric and inconclusive dorsalis pedis artery Doppler results, 2 legs had oscillometric cuff pressure intolerance. Using Doppler ABI <0.9 as a diagnostic threshold, compared with the high Doppler ABI, oscillometric method had a sensitivity of 57.81%, a specificity of 95.18%, the ICC was 0.626 (95% confidence interval [CI]: 0.536-0.701), Bland-Altman method showed 11/211 (5.21%) difference points outside the 95% limits of agreement. Compared with the low Doppler ABI, oscillometric method had a sensitivity of 50.66%, a specificity of 98.31%, the ICC was 0.541(95% CI: 0.483-0.630), Bland-Altman method showed 11/211 (5.21%) difference points outside the 95% limits of agreement. Using 1.00 as the diagnostic threshold and considering error oscillometric results as abnormal ABIs, the sensitivity improved to 88.05% with high Doppler ABI and 81.42% with the low. The accuracy and reliability of oscillometric ABI in patients with PAD is unsatisfied, which makes it not suitable as an alternative method in clinic disease assessment. Using 1.0 as the ABI oscillometric threshold for PAD diagnosis can improve the diagnostic value.

A Low-Cost High-Throughput C-Band Communication System for CubeSats

This paper presents the physical layer of a proprietary broadband communication system for CubeSats. The system operates in the C band (5.8 GHz), delivering at least 10 Mbps of the net user throughput. Operation at low elevation angles (and therefore low SNRs) and high Doppler shifts is made possible thanks to a sophisticated synchronization subsystem. The system can be adapted to propagation conditions experienced during a given visibility window by changing the signal bandwidth and coding rate. It is implemented using Software Defined Radio (SDR) technology. The system will be used in two missions that are scheduled for 2023 and 2024 and are planned in cooperation with the National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute” and SatRev S.A.

Robust Doppler compensation for low frequency underwater communications

Impairment caused by Doppler frequency shift and harsh channel condition distinguish underwater acoustic communications from radio communications. Slow speed of acoustic waves produces relatively high Doppler shift and result in expansion or compression in time samples, which is known as Doppler scaling. In particular, the Doppler scaling causes significant carrier frequency offset (CFO) in orthogonal frequency division modulation (OFDM). To compensate the CFO, it is essential to resample signal samples according to the Doppler scale. In theory, the Doppler scale can be estimated by measuring the distance between peaks of the matched filter output of consecutive Doppler-invariant preambles. In practice, multi-path reflections and non-orthogonality between the HFM and OFDM payload produce large numbers of local false peaks. In this paper, we propose a robust Doppler estimation technique by employing constant false alarm rate (CFAR) filter to remove false peaks. We validate the performance of the proposed scheme through two sea-trials carried out in shallow water near Jervis Bay, Australia. In the sea-trials, a slow-moving towed hydrophone array was deployed as the receiver and the source was a stationary, low source level, vertical transmit array. Sea-trial results demonstrated up to 112bps information rate using bit-interleaved coded OFDM over 400 Hz bandwidth.

Reduction of PAPR in OTFS signal using airy special function

Abstract Orthogonal time frequency space (OTFS) is a new two dimensional modulation technique that use the delay-Doppler domain. Despite the fact that OTFS can handle time varying channels and high Doppler scenarios, it has a high Peak-to-Average Power Ratio (PAPR). In this study, we developed an airy-based companding technique for the OTFS signal to address this issue. The airy function is a particular function that is commonly used in optics. We evaluate the proposed airy based companded OTFS with various companding techniques in order to assess its performance. Simulations signify that the proposed airy based companding outperforms the rooting companding, and μ − law companding in terms of both PAPR and instantaneous to average power ratio (IAPR).

Improved Ultrafast Power Doppler Imaging Using United Spatial-Angular Adaptive Scaling Wiener Postfilter.

Ultrafast power Doppler imaging (uPDI) using high-frame-rate plane-wave transmission is a new microvascular imaging modality that offers high Doppler sensitivity. However, due to the unfocused transmission of plane waves, the echo signal is subject to interference from noise and clutter, resulting in a low signal-to-noise ratio (SNR) and poor image quality. Adaptive beamforming techniques are effective in suppressing noise and clutter for improved image quality. In this study, an adaptive beamformer based on a united spatial-angular adaptive scaling Wiener (uSA-ASW) postfilter is proposed to improve the resolution and contrast of uPDI. In the proposed method, the signal power and noise power of the Wiener postfilter are estimated by uniting spatial and angular signals, and a united generalized coherence factor (uGCF) is introduced to dynamically adjust the noise power estimation and enhance the robustness of the method. Simulation and in vivo data were used to verify the effectiveness of the proposed method. The results show that the uSA-ASW can achieve higher resolution and significant improvements in image contrast and background noise suppression compared with conventional delay-and-sum (DAS), coherence factor (CF), spatial-angular CF (SACF), and adaptive scaling Wiener (ASW) postfilter methods. In the simulations, uSA-ASW improves contrast-to-noise ratio (CNR) by 34.7 dB (117.3%) compared with DAS, while reducing background noise power (BNP) by 52 dB (221.4%). The uSA-ASW method provides full-width at half-maximum (FWHM) reductions of [Formula: see text] (59.5%) and [Formula: see text] (56.9%), CNR improvements of 25.6 dB (199.9%) and 42 dB (253%), and BNP reductions of 46.1 dB (319.3%) and 12.9 dB (289.1%) over DAS in the experiments of contrast-free human neonatal brain and contrast-free human liver, respectively. In the contrast-free experiments, uSA-ASW effectively balances the performance of noise and clutter suppression and enhanced microvascular visualization. Overall, the proposed method has the potential to become a reliable microvascular imaging technique for aiding in more accurate diagnosis and detection of vascular-related diseases in clinical contexts.

Joint Design of Complementary Sequence and Receiving Filter with High Doppler Tolerance for Simultaneously Polarimetric Radar

Simultaneously polarimetric radar (SPR) realizes the rapid measurement of a target’s polarimetric scattering matrix by transmitting orthogonal radar waveforms of good ambiguity function (AF) properties and receiving their echoes via two orthogonal polarimetric channels at the same time, e.g., horizontal (H) and vertical (V) channels (antennas) sharing the same phase center. The orthogonality of the transmitted waveforms can be realized using low-correlated phase-coded sequences in the H and V channels. However, the Doppler tolerances of the waveforms composed by such coded sequences are usually quite low, and it is hard to meet the requirement of accurate measurement regarding moving targets. In this paper, a joint design approach for unimodular orthogonal complementary sequences along with the optimal receiving filter is proposed based on the majorization–minimization (MM) method via alternate iteration for obtaining simultaneously polarimetric waveforms (SPWs) of good orthogonality and of the desired AF. During design, the objective function used for minimizing the sum of the complementary integration sidelobe level (CISL) and the complementary integration isolation level (CIIL) is constructed under the mismatch constraint of signal-to-noise ratio (SNR) loss. Different SPW examples are given to show the superior performance of our design in comparison with other designs. Finally, practical experiments implemented with different SPWs are conducted to show our advantages more realistically.

Radar detection and speed estimation of high‐speed targets using phase‐modulated waveforms

AbstractSpecifying parameters of high‐speed targets as range and velocity in radar systems operating with phase‐modulated signals is a problematic process because of the serious effect of high Doppler frequency on these types of waveforms. In the existence of a high‐speed target, its Doppler frequency will be very high such that it totally changes the phase sequence of the received signal. As a result, the matched filter output will be distorted. Therefore, estimating target parameters will be impossible. In this letter, a new method is proposed for detecting and estimating velocity of high speed targets using phase‐modulated signals. The suggested technique methodology depends on compensating the target high‐Doppler frequency for signal recovery using a customized waveform shape. Moreover, the Doppler frequency value is estimated without ambiguity from one pulse, and without the need for a range‐Doppler module. As such, the implementation of the proposed method is simple and inexpensive. The performance evaluation of the new method shows its superiority in compensation and estimation compared to other techniques when examined under higher Doppler frequency and noise compared to the conventional radar.

Integrated Sensing and Communications System With Multiple Cyclic Prefixes

This letter proposes an integrated sensing and communications (ISAC) system with multiple cyclic prefixes (CPs) to achieve effectiveness of ISAC in high Doppler scenarios. Multiple CPs include sensing CP and communication CP, which are prepended at the beginning of the transmitted signal and before each modulation symbol, respectively. For transmission, the introduction of multiple CPs obtains abundant maximum unambiguous Doppler by decoupling sensing and communication requirements. For sensing reception, a sensing parameter estimation method is developed which achieves robustness to Doppler shifts. Moreover, the multiple CPs are utilized to enhance sensing processing gain and reduce the complexity of sensing parameter estimation. Theoretical and numerical analyses reveal that the proposed system possesses robustness to Doppler shifts, high processing gain, reliable estimation accuracy and affordable complexity.

Assessment of High Frequency Imaging and Doppler System for the Measurements of the Radial Artery Flow-Mediated Dilation

Objectives: In the article we describe the new, high frequency, 20 MHz scanning/Doppler probe designed to measure the flow mediated dilation (FMD) and shear rate (SR) close to the radial artery wall. Methods: We compare two US scanning systems, standard vascular modality working below 12 MHz and high frequency 20 MHz system designed for FMD and SR measurements. Axial resolutions of both systems were compared by imaging of two closely spaced food plastic foils immersed in water and by measuring systolic/diastolic diameter changes in the radial artery. The sensitivities of Doppler modalities were also determined. The diagnostic potential of a high frequency system in measurements of FMD and SR was studied in vivo, in two groups of subjects, 12 healthy volunteers and 14 patients with stable coronary artery disease (CAD). Results: Over three times better axial resolution was demonstrated for a high frequency system. Also, the sensitivity of the external single transducer 20 MHz pulse Doppler proved to be over 20 dB better (in terms of a signal-to-noise ratio) than the pulse Doppler incorporated into the linear array. Statistically significant differences in FMD and FMD/SR values for healthy volunteers and CAD patients were confirmed, p-values < 0:05. The areas under Receiver Operating Characteristic (ROC) curves for FMD and FMD/SR for the prediction CAD had the values of 0.99 and 0.97, respectively. Conclusions: These results justify the usefulness of the designed high-frequency scanning system to determine the FMD and SR in the radial artery as predictors of coronary arterial disease.

Contrast-Enhanced Ultrasound and High Sensitive Doppler for Monitoring Outcomes of Uterine Artery Embolization

To monitor fibroid microvascularity using contrast-enhanced ultrasound (CEUS) and a new high-sensitive Doppler mode (SMI) for assessment of uterine artery embolization (UAE) outcomes. Forty women with symptomatic uterine fibroids scheduled for UAE were enrolled in this Institutional Review Board-approved study. Subjects underwent three examinations (day 0, 15, and 90 post-UAE) with Color Doppler (CDI), power Doppler (PDI), color and monochrome SMI (cSMI and mSMI), and CEUS imaging of the fibroids. Clips were assessed by two radiologists classifying fibroids based on their vascularity. Fibroid fractional vascularity (FV; % of enhanced pixels within the fibroid) and flow intensity (as mean brightness level of the enhanced pixels) were quantified. Results were analyzed using repeated measures ANOVA and nonparametric Wilcoxon sign rank tests. Inter-reader agreement was assessed with κ-values. There was overall agreement between readers for all imaging modalities and examination times (P=.25; κ=0.70). The FV analysis showed statistically significant differences between CEUS and the Doppler imaging modes (CDI, PDI, cSMI, and mSMI) for the three examination times were compared (P<.0001). The comparison using CDI, PDI, and cSMI showed no statistically significant difference (P=.53). The flow intensity analysis comparison between the Doppler imaging modes (CDI, PDI, cSMI and mSMI) and examination times showed statistically significant differences between all the Doppler imaging modalities (P=.02), except for the 90days post-UAE (P=.34). When the comparison was made for CDI, PDI, and cSMI there was no statistically significant differences (P<.47). CEUS and SMI can accurately evaluate fibroid microvascularity, and therefore, can be a noninvasive and accurate method for monitoring outcomes following UAE treatment.

Comparing Non-Stress Test versus Umbilical Artery Doppler Velocimetry among Aample of High-risk Pregnant Women in Erbil City

Background: The mainstay of care for lowering maternal and perinatal mortality and morbidity is antepartum foetal surveillance. Numerous techniques are used, including fetal movements, Vibroacoustic stimulation tests, contraction stress tests, biophysical profiles of the fetus, modified biophysical profiles, non-stress testing and Doppler Umbilical artery of the fetus's. The fetal heart reaction to internal and extrinsic stimuli is seen on electronic fetal monitoring devices. The benefit of high resolution dynamic ultrasonography and Doppler imaging is that it allows for the visualization of the fetus and its surroundings as well as the monitoring of fetal health by measuring utero-placental circulation. Patients and techniques: The cross-sectional investigation including 120 pregnant women who visited the Maternity Teaching Hospital between 26 June and 31 August 2022 and complained of decreased uterine contractions have been included. The questionnaire included sociodemographic data, obstetrical data, information on the fetal outcome and method of delivery. In accordance with the American Academy of Obstetricians and Gynecologists, cardiotopography was utilized to conduct a non-stress test, and the outcomes were categorized as reactive and non-reactive. Cardiotopography was used to perform a non-stress test, and the results were classified as reactive or non-reactive in accordance with the American Academy of Obstetricians and Gynecologists. Also, during 32 weeks or more of gestation, the inferior vena cava was not compressed by the gravid uterus during ultrasonography of the umbilical arteries, which was performed in a semi-recumbent position with a slight lateral tilt. Result: Based on NST and Doppler velocimetry of the umbilical artery, all cases were classified into two groups. The outcomes of the two tests didn't significantly differ from one another. The rate of Cesarean section (CS) was 46.1% among women with non-reactive (abnormal) CTG, compared with 25% among women with normal CTG (p = 0.0316). Only one neonate (1.3%) died among women with normal CTG, while none of the neonates died among women with abnormal CTG. The rate of CS among women with abnormal ultrasonography was 80% compared to women (11%) with normal ultrasonography. Furthermore, one neonate (2.1%) in the group of abnormal doppler, compared with 0% in the normal group. Conclusion: NST and umbilical artery Doppler of are sensitive and specific tests with strong positive prognostic value to suggest a poor prognosis for the newborn. Doppler velocimetry of umbilical artery is more important than a non-stress test because it lowers the likelihood of a CS birth in non-reactive non-stress test situations without increasing the risk of perinatal morbidity and mortality. Bangladesh Journal of Medical Science Vol.22 (Special Issue) 2023 p.10-17

Assessment of early vascular changes in adult females with polycystic ovary syndrome: correlation with insulin resistance

Polycystic ovary syndrome (PCOS) is the commonest endocrine disorder in females in the reproductive period with estimated prevalence of 5% to 18% [1]. It contributes to the mortality and morbidity in patients with PCOS due to the increased risk of different metabolic and cardiovascular (CV) complications [2]. Despite the presence of obesity in 40-60% of cases [3], the disease may occur in non-obese women. The occurrence of metabolic disorders in non-obese PCOS patients, suggests that the syndrome itself may play a role in the development of metabolic and CV co-morbidities [4]. The identification of early stages of atherosclerosis in patients with PCOS might be useful in the development of new strategies to control modifiable CV risk factors [5]. Assessment of vascular endothelial function (ED) as an initial reversible step in atherosclerosis development, may serve as an integral index for CV risk factor burden [6]. In addition, carotid intima media thickness (CIMT) is a helpful marker for atherosclerosis and for the identification of increased risk of CV disease [7]. Our study assessed the early vascular changes in Egyptian women with PCOS both physically and functionally by looking at the CIMT using high resolution Doppler ultrasound and by measuring ED using brachial artery flow–mediated vasodilatation (FMD). Our results indicate that patients with PCOS have significant ED and premature atherosclerosis which is, to a great extent, independent of obesity and IR. This suggests that PCOS patients are at increased risk for premature CVD and may benefit from early detection and management.

Efficient Rate-Splitting Multiple Access for the Internet of Vehicles: Federated Edge Learning and Latency Minimization

Rate-Splitting Multiple Access (RSMA) has recently found favour in the multi-antenna-aided wireless downlink, as a benefit of relaxing the accuracy of Channel State Information at the Transmitter (CSIT), while in achieving high spectral efficiency and providing security guarantees. These benefits are particularly important in high-velocity vehicular platoons since their high Doppler affects the estimation accuracy of the CSIT. To tackle this challenge, we propose an RSMA-based Internet of Vehicles (IoV) solution that jointly considers platoon control and FEderated Edge Learning (FEEL) in the downlink. Specifically, the proposed framework is designed for transmitting the unicast control messages within the IoV platoon, as well as for privacy-preserving FEEL-aided downlink Non-Orthogonal Unicasting and Multicasting (NOUM). Given this sophisticated framework, a multi-objective optimization problem is formulated to minimize both the latency of the FEEL downlink and the deviation of the vehicles within the platoon. To efficiently solve this problem, a Block Coordinate Descent (BCD) framework is developed for decoupling the main multi-objective problem into two sub-problems. Then, for solving these non-convex sub-problems, a Successive Convex Approximation (SCA) and Model Predictive Control (MPC) method is developed for solving the FEEL-based downlink problem and platoon control problem, respectively. Our simulation results show that the proposed RSMA-based IoV system outperforms both the popular Multi-User Linear Precoding (MU–LP) and the conventional Non-Orthogonal Multiple Access (NOMA) system. Finally, the BCD framework is shown to generate near-optimal solutions at reduced complexity.

Radar Range Deception With Time-Modulated Scatterers

Modern radar systems are designed to have high Doppler tolerance to detect fast-moving targets. This means range and Doppler estimations are inevitably coupled, opening pathways to concealing objects by imprinting artificial Doppler signatures on the reflected echoes. Proper temporal control of the backscattered phase can cause the investigating radar to estimate wrong range and velocity, thus cloaking the real position and trajectory of the scatterer. This deception method is exploited here theoretically for arbitrary Doppler tolerant waveforms and then tested experimentally on an example of the linear frequency modulated radar, which is the most common waveform of that class used in practice. The method allows retaining radio silence with a semi passive (battery assisted) approach that can work well with time-dependent metasurfaces. Furthermore, as an insight into new capabilities, we demonstrate that temporally concealed objects could even be made to appear closer than they truly are without violating the laws of relativity.

Unimodular Perfect and Nearly Perfect Sequences: a Variation of Björck’s Scheme

Constant Amplitude (CA), Zero Auto Correlation (ZAC) sequences (or CAZAC sequences, aka perfect sequences) have numerous applications. We generalize the CAZAC notion to what we term as CASAC by permitting small autocorrelations (SAC). We extend Björck’s classification result of two-valued CAZAC sequences by providing a complete classification of all almost 2-valued (i.e., two-valued except for the first position which uses a third value) CASAC sequences. While Björck’s original work dealt only with primes p, we extend his ideas to any abelian group of order <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$v\equiv 1\pmod {4}$ </tex-math></inline-formula> , as opposed to restricting just to the prime fields GF(p). Björck sequences have better ambiguity function than Zadoff-Chu sequences, making them suitable for radar and communications applications in the presence of high Doppler shifts. In fact, the discrete narrow band ambiguity function has an optimal bound in case of Björck sequences (as opposed to Gauss sequences). A one-parameter infinite family of CASAC we construct would have applications in Multiple-Input Multiple-Output (MIMO) areas. Toward MIMO applications, we introduce a performance measure we term as cross merit factor to study cross correlation behavior, generalizing the well-known notion of Golay Merit Factor (GMF).

Orthogonal Time Frequency Space and Predictive Beamforming-Enabled URLLC in Vehicular Networks

To fulfill the requirements of future intelligent transportation system in 6G era, ultra-reliable and low-latency vehicular communications is of great importance. In high-mobility scenarios, the conventional orthogonal frequency division multiplexing (OFDM) modulation may fail to work due to high Doppler spreads. Moreover, the dynamic network topology imposes challenges on aligning the beams in multiple antenna systems. In this context, this article introduces a new orthogonal time frequency space (OTFS) and sensing-assisted predictive beamforming framework for supporting reliable and low-latency vehicular communications. In particular, we will first overview the OTFS modulation scheme, which performs data transmission in the delay-Doppler (DD) domain and discuss its superiority in improving communication reliability in vehicular networks. Then the sensing-assisted predictive beamforming scheme will be introduced, which does not rely on dedicated pilots for beam pairing, leading to very low overhead and latency. Benefiting from the DD channel representation, we briefly discuss the potential of channel prediction. Lastly, the challenges and future research directions are summarized.