Acoustic Window Research Articles

The Representation of Time Windows in Primate Auditory Cortex.

Whether human and nonhuman primates process the temporal dimension of sound similarly remains an open question. We examined the brain basis for the processing of acoustic time windows in rhesus macaques using stimuli simulating the spectrotemporal complexity of vocalizations. We conducted functional magnetic resonance imaging in awake macaques to identify the functional anatomy of response patterns to different time windows. We then contrasted it against the responses to identical stimuli used previously in humans. Despite a similar overall pattern, ranging from the processing of shorter time windows in core areas to longer time windows in lateral belt and parabelt areas, monkeys exhibited lower sensitivity to longer time windows than humans. This difference in neuronal sensitivity might be explained by a specialization of the human brain for processing longer time windows in speech.

New echocardiographic indices of shift to biventricular failure to optimize risk stratification of chronic heart failure.

AimsThe present study investigated the prognostic impact of either isolated left atrial (LA) impairment, or its association with right ventricular (RV) failure, in heart failure (HF) with reduced ejection fraction (HFrEF), using basic and speckle tracking echocardiography (STE).Methods and resultsOne hundred and six outpatients with HFrEF were enrolled in this prospective observational study. Patients with primary lung diseases, non‐sinus rhythm, previous cardiac surgery, and poor acoustic window were excluded. After clinical examination and basic echocardiography, STE was used to measure peak atrial longitudinal strain (PALS) and a new marker of RV performance and pulmonary circulation relation: free‐wall RV longitudinal strain (fwRVLS)/systolic pulmonary artery pressure (sPAP). Patients were followed for all‐cause/cardiovascular death and HF hospitalization. Of 84 eligible patients (60.1 ± 11.5 years; 82% male patients), 48 reached the combined endpoint (cardiovascular death and/or HF hospitalization). Population was divided into three groups: Group 1 (PALS ≥ 15 and fwRVLS/sPAP ≤ −0.5), Group 2 (PALS ≤ 15 and fwRVLS/sPAP ≤ −0.5), and Group 3 (PALS ≤ 15 and fwRVLS/sPAP > −0.5). Mean follow up was 3.5 ± 0.3 years. The higher severity groups were associated with higher LA volume index (P < 0.0001), New York Heart Association class (P = 0.02), mitral regurgitation (P = 0.0004) and tricuspid regurgitation grades (P < 0.0001), lower left ventricular (LV) ejection fraction (P = 0.0003), LV global longitudinal strain (P < 0.0001), PALS (P < 0.0001), tricuspid annular plane systolic excursion (P < 0.007), sPAP (P < 0.0001), and RV strain (P < 0.0001). Reduced PALS and fwRVLS/sPAP were independent predictors of the combined endpoint with adjusted Cox models (hazard ratio = 9.54; 95% confidence interval = 2.95–30.92; P = 0.0002 for Group 3 vs. Group 1). Kaplan–Meier curves showed early and persistent divergence between the three groups for the prediction of the combined endpoint and of all‐cause death (P < 0.0001).ConclusionsThe combination of LA and right heart damage entails worse prognosis in patients with HFrEF. The evaluation of PALS and fwRVLS/sPAP could aid risk stratification of HFrEF patients to provide them early treatment.

Transcranial color Doppler ultrasonography: methodology and usefulness for the study of patent foramen ovale in cryptogenic stroke

Non-invasive Doppler ultrasonographic study of cerebral arteries (transcranial Doppler, TCD) has been extensively applied on both outpatient and inpatient settings. It is performed placing a low-frequency (≤2 MHz) transducer on the scalp of the patient over specific acoustic windows, in order to visualize the intracranial arterial vessels and to evaluate the cerebral blood flow velocity and its alteration in many different conditions. Nowadays a valid indication for TCD in the outpatient setting is the research of right-to-left shunting, responsible for the so-called "paradoxical embolism", most often due to patency of foramen ovale, which is responsible for the majority of cryptogenic strokes occurring in patients younger than 55 years. TCD also allows to classify the grade of severity of such shunts using the so-called "microembolic signal grading score". Therefore, TCD is an essential cardiological exam for the detection of patent foramen ovale, assuming an important role as a first-level examination to guide the subsequent diagnostic-therapeutic management. In addition, TCD has found many useful applications in neurocritical care practice. It is useful for the identification of intracranial vascular stenosis and for the assessment of critical conditions including vasospasm in subarachnoid hemorrhage, traumatic brain injury and brain stem death. It is also used to evaluate cerebral hemodynamic changes after stroke, to investigate cerebral pressure autoregulation, and for the clinical evaluation of cerebral vasomotor reactivity.

The AIUM Practice Parameter for the Performance of an Ultrasound Examination of the Neonatal and Infant Spine.

The AIUM Practice Parameter for the Performance of an Ultrasound Examination of the Neonatal and Infant Spine.

Abstract 10639: Abbreviated Cardiac Magnetic Resonance Imaging versus Echocardiography for Interval Assessment of Systolic Function in Duchenne Muscular Dystrophy: Patient Satisfaction, Clinical Utility and Image Quality

Introduction: Interval assessment of systolic function in patients with Duchenne Muscular Dystrophy (DMD) is challenging by echocardiography (echo). Cardiac magnetic resonance imaging (CMR) has been limited due to study duration and patient experience. We developed an abbreviated CMR (aCMR) protocol which consisted only of cine acquisitions in the short axis, 4 chamber and vertical long axis planes, and compared it to echo in regard to: exam duration, patient satisfaction, clinical utility and image quality scores. Methods: DMD patients were recruited prospectively to undergo simultaneous echo and aCMR. Exclusion criteria included need for continuous positive pressure ventilation (PPV) and inability to lay supine ≥ 30 minutes. Subjects completed a patient satisfaction survey (PSS) comparing modalities. The clinical cardiologist completed a survey (CUS) assessing the clinical utility of each modality. A blinded expert reviewer completed an image quality survey (GQAS) for each modality. Results were compared using the Wilcoxon signed-rank test and Spearman correlation. Results: 19 DMD patients participated. PSS scores and exam duration were equivalent between modalities, while CUS and GQAS scores favored aCMR. ACMR scored particularly higher than echo in RV visualization and judgement of atrial size. Older age had a statistically significant negative correlation with echo GQAS and CUS scores, as well as aCMR PSS scores. Nighttime PPV requirement and non-ambulatory status were associated with worse echo CUS scores. Poor image quality precluding quantification existed in 4 (21%) echo and 0 aCMR studies. Conclusions: The aCMR protocol resulted in improved clinical utility and quality scores relative to echocardiography, without detriment in patient satisfaction or exam duration. For DMD patients known to have challenging echo acoustic windows, aCMR should be considered in lieu of echocardiography for interval assessment of systolic function.

Transgastric imaging-The key to successful periprocedural TEE guiding for edge-to-edge repair of the tricuspid valve.

Intraprocedural transesophageal echocardiography (TEE) guidance plays an essential role in transcatheter repair therapy of the tricuspid valve (TV). So far, several different imaging concepts are in use. We propose an imaging protocol that fully addresses the morphological complexity of the TV and further offers efficacious workarounds for the frequently occurring restrictions of TV imaging in edge-to-edge repair of the TV. As a tertiary referral center with a large experience of more than 250 cases of transcatheter edge-to-edge repair (TEER) of the TV performed at the Heart Valve Center in Mainz/Germany, we have constantly adapted our peri-interventional echocardiographic approach to accomplish both. As a key measure for success, we intensely rely on the transgastric acoustic windows that not only deliver high-resolution information on the morphology of the TV and all relevant procedural steps but also help to avoid the frequent shadowing artifacts experienced in transesophageal imaging.

Review of Neonatal and Infant Cranial US.

Review of Neonatal and Infant Cranial US.

Cerebral autoregulation in anoxic brain injury patients treated with targeted temperature management

BackgroundLittle is known about the prevalence of altered CAR in anoxic brain injury and the association with patients’ outcome. We aimed at investigating CAR in cardiac arrest survivors treated by targeted temperature management and its association to outcome.MethodsRetrospective analysis of prospectively collected data. Inclusion criteria: adult cardiac arrest survivors treated by targeted temperature management (TTM). Exclusion criteria: trauma; sepsis, intoxication; acute intra-cranial disease; history of supra-aortic vascular disease; severe hemodynamic instability; cardiac output mechanical support; arterial carbon dioxide partial pressure (PaCO2) > 60 mmHg; arrhythmias; lack of acoustic window. Middle cerebral artery flow velocitiy (FV) was assessed by transcranial Doppler (TCD) once during hypothermia (HT) and once during normothermia (NT). FV and blood pressure (BP) were recorded simultaneously and Mxa calculated (MATLAB). Mxa is the Pearson correlation coefficient between FV and BP. Mxa > 0.3 defined altered CAR. Survival was assessed at hospital discharge. Cerebral Performance Category (CPC) 3–5 assessed 3 months after CA defined unfavorable neurological outcome (UO).ResultsWe included 50 patients (Jan 2015–Dec 2018). All patients had out-of-hospital cardiac arrest, 24 (48%) had initial shockable rhythm. Time to return of spontaneous circulation was 20 [10–35] min. HT (core body temperature 33.7 [33.2–34] °C) lasted for 24 [23–28] h, followed by rewarming and NT (core body temperature: 36.9 [36.6–37.4] °C). Thirty-one (62%) patients did not survive at hospital discharge and 36 (72%) had UO. Mxa was lower during HT than during NT (0.33 [0.11–0.58] vs. 0.58 [0.30–0.83]; p = 0.03). During HT, Mxa did not differ between outcome groups. During NT, Mxa was higher in patients with UO than others (0.63 [0.43–0.83] vs. 0.31 [− 0.01–0.67]; p = 0.03). Mxa differed among CPC values at NT (p = 0.03). Specifically, CPC 2 group had lower Mxa than CPC 3 and 5 groups. At multivariate analysis, initial non-shockable rhythm, high Mxa during NT and highly malignant electroencephalography pattern (HMp) were associated with in-hospital mortality; high Mxa during NT and HMp were associated with UO.ConclusionsCAR is frequently altered in cardiac arrest survivors treated by TTM. Altered CAR during normothermia was independently associated with poor outcome.

Echocardiographic assessment of radial right ventricular function in heart transplant recipients.

AimsRight ventricular (RV) allograft dysfunction is present in half of all heart transplant (HT) recipients. Non‐invasive assessment of RV function in the setting of rejection is not well described. We outline an echocardiographic technique, short‐axis fractional area change (SAXFAC), to evaluate RV function in the HT population and correlate this with the grade of pathologic rejection.Methods and resultsWe retrospectively reviewed the electronic medical records of 110 people who received a HT between 1 January 2015 and 29 February 2020 and had no evidence of rejection. One hundred eighty‐two transthoracic echocardiograms (TTEs) completed up to 1 year from the date of transplantation were analysed for the target acoustic window, the parasternal mid‐ventricular short‐axis view. Sixty‐one TTEs from 23 healthy transplants were deemed appropriate for SAXFAC determination. Thirty‐three organ recipients with at least grade 1R allograft rejection were also identified, and their TTEs screened for SAXFAC analysis. Two expert readers independently calculated SAXFAC as follows: RV end‐diastolic area minus end‐systolic area divided by end‐diastolic area. Using commercially available software (Epsilon, Ann Arbor, Michigan), we quantified RV radial strain, longitudinal strain, and apical fractional area change (FAC). Twenty‐eight transplant recipients with grade 0R or 1R rejection and nine patients with clinically significant rejection completed the study analysis. SAXFAC demonstrated significant variability in the entire population with an inverse relationship to severity of allograft rejection (P ≤ 0.01). Radial strain and FAC were also associated with clinically significant rejection (P ≤ 0.01).ConclusionsShort‐axis fractional area change is a simple two‐dimensional technique to assess RV function in HT recipients and showed no significant inter‐observer variability. In our small, single‐centre, retrospective case series, lower SAXFAC values were associated with clinically significant allograft rejection. The small sample size and infrequent occurrence of rejection make our observations hypothesis‐generating only. We advocate dedicated RV SAXFAC imaging planes be included when assessing allograft function.

Right ventricular ejection fraction as predictor of outcome in acute heart failure using RV ellipsoid model. A retrospective analysis of a prospective cross-sectional study

Abstract Introduction Echocardiography (TTE) is an essential imaging modality for assessment of RV function in acute heart failure. Established parameters are useful and easy to perform but fail to reflect on global volumes due to reliability on one acoustic window. It is therefore attractive to calculate RV volumes and ejection fraction using an ellipsoid model (RVEF/E) which has been validated against MRI in healthy adults but not in the HF patients. Purpose Predictive value of RVEF/E were compared with two established echo parameters of RV function over two-year follow-up period in patients with acute HF. Primary outcome measure was all-cause mortality. Methods Prospective cross-sectional study enrolling 418 consecutive patients with symptoms of acute HF according to a predefined study protocol. All patients underwent TTE assessment of RV function using Tricuspid Annular Plane Systolic Excursion (TAPSE) and RV fractional area change (RVFAC) and RVEF/E. RV Volumes calculated using formula, RVIT is RV inflow tract diameter, RVLAX is RV length and LVD is LV maximal diameter in 2 chamber view. RVV=(3.14/6) x RVIT x RVLAX x LVD Results ROC analyses established an RVEF/E cut-off of 46.8%, TAPSE of 1.6cm and RVFAC of 38.2%. RVEF/E was able to separate patients with higher BNP level (p≤0.0001) and lower systolic BP (p≤0.002). As expected TAPSE and RVFAC were significantly reduced in patients with impaired RVEF. RVEF/E was found equal to TAPSE &amp; RVFAC in predicting outcome (HR 1.48 vs HR 1.48, p≤0.01 vs p≤0.01) and provided benefit of RV volume estimation. Conclusions This is the first study to demonstrate that RVEF/E derived from ellipsoid model is not inferior to well established measures of RV function as a prognostic indicator of medium-term outcome in the acute HF. Funding Acknowledgement Type of funding sources: None. Kaplan Meier survival curvesBaseline characteristics

Exercise stress echocardiography with probe fixated on patient's chest

Abstract Background Stress echocardiography (SE) has been widely used in clinical practice for decades and recently has gained even more importance in diagnostic approach to ischemic heart disease. However, it still has numerous limitations. Despite advantages of physical exercise as most physiologic stressor, it is impossible to continuously monitor the cardiac function during treadmill test and difficult to maintain an optimal acoustic window during cycle ergometer exercise test. We aimed to assess the feasibility of probe fixation for the use during exercise echocardiography. Methods 48 subjects (47 men, mean age 42±17 years, 25 healthy volunteers, 23 patients with suspected coronary artery disease) were included in this study. All subjects underwent exercise stress test on treadmill (32 cases) or cycle ergometer (16 cases). Both sector and matrix probes were used (in 17 and 31 tests, respectively). We assessed semi-quantitatively the quality of acquired apical views at each stage using four-point grading system (0 = poor, 1 = suboptimal, 2 = acceptable, 3 = optimal). Results The mean time required for probe fixation was 9±2 min. At baseline, 10 patients had at least one apical window of quality precluding reliable analysis. 25 patients probe repositioning during exercise (more often on treadmill). During peak exercise quality of images in all views declined, but it remained sufficient in 29 patients for diagnostic purposes. Thus, 76% of performed tests (60% for all study population) were of sufficient image quality. Conclusion Probe fixation offers the possibility of continuous acquisition of echocardiographic images during physical exercise. However the device is suitable almost exclusively for male patients. Moreover, in some patients it requires repositioning. Funding Acknowledgement Type of funding sources: None.

Deformation imaging by strain in chronic heart failure over sacubitril/valsartan: a multicenter echocardiographic registry (DISCOVER) ARNI

Abstract Background Sacubitril/valsartan changed the treatment of heart failure with reduced ejection fraction (HFrEF), due to the positive effects morbidity and mortality partly mediated by left ventricular reverse remodeling (LVRR). The aim of this multicenter study was to identify echocardiographic predictors of LVRR after sacubitril/valsartan administration. Methods Patients with HFrEF requiring therapy with sacubitril/valsartan from 13 Italian centers were included. Echocardiographic indexes including speckle tracking echocardiography (STE) were used to predict LVRR (defined as LV end-systolic volume reduction and ejection fraction [LVEF] improvement &amp;gt;10% at follow-up) at 6 months follow-up as the primary endpoint. Changes in symptoms (NYHA class) and neurohormonal activations (N-terminal-pro-brain natriuretic peptide [NTproBNP]) were also evaluated as secondary endpoints. Patients with poor acoustic windows and missing data were excluded. Results The final population consisted of 341 patients (mean age: 65±10 years; 18% female, median LVEF 30% [interquartile range:25; 34]. At 6 months follow-up, cardiac dimensions and function, including left heart STE parameters, improved (Table 1). Moreover, 82 (24%) patients showed early complete response (LVRR and LVEF ≥35%), 55 (16%) early incomplete response (LVRR and LVEF &amp;lt;35%), 204 (60%) no response (no LVRR and LVEF &amp;lt;35%) after 6 months of sacubitril/valsartan. Among patients with ischemic etiology, 68% (108) did not develop LV RR. Age, sex, general characteristics, baseline NYHA class and NT-pro BNP did not significantly differ between the groups.Conversely, baseline LV dimensions and LVEF showed significant differences between the groups (p&amp;lt;0.0001). Also, STE parameters were considerably better in group 1 compared to group 2 and 3 both at baseline and follow-up. Non-ischemic etiology, a lower left atrial volume index and a higher global longitudinal strain were all independent predictors of LVRR at multivariable logistic analysis (all p&amp;lt;0.01). With ROC and spline curves, LV GLS &amp;gt;−9.3% showed a good accuracy in predicting LV RR (Figure 1). LA strain was the best predictor of positive changes in NYHA class and NT-proBNP (all p&amp;lt;0.05). Conclusions STE parameters at baseline could be useful to predict LVRR and early clinical response to sacubitril-valsartan, and thus could be used as a guide for treatment in patients with HFrEF. Funding Acknowledgement Type of funding sources: None. Table 1Figure 1

Semi-automated left ventricular endocardial detection versus hand-tracing in the measurement of left ventricular volumes and ejection fraction in daily clinical practice

Abstract Background The common method of assessing left ventricle (LV) volumes and ejection fraction (EF) is hand-tracing Biplane Simpson method. Alternatively, ultrasound vendors offer different semi-automated LV endocardial border detection software with anatomical intelligence to assess LV volumes and EF. By using speckle-tracking technique, this software tracks the LV endocardium throughout the cardiac cycle and computes the LV volumes in every image frame using the disk summation method from which a volume-curve is generated, and the EF is calculated using the maximum and minimum volumes obtained. Data on the performance of this method in comparison with the hand-tracing Biplane Simpson method in daily clinical practice is scarce. Purpose To determine the accuracy of LV volumes and EF using semi-automated LV endocardial detection tracing, and to compare the reproducibility of this method with the hand-tracing Biplane Simpson method, among operators with varying level of experience in echocardiography. Methods This was a single center retrospective observational study, conducted in year 2020. 127 patients, aged &amp;gt;18 years, who underwent clinically indicated transthoracic echocardiography were recruited. The echocardiographic images were analyzed independently in a blinded fashion by 3 operators – a sonographer, a fellow-in-training and a cardiologist specialized in echocardiography. The LV volumes and EF were first measured using hand-tracing Biplane Simpson method, then repeated using semi-automated tracing at a different time and the operator were blinded to the initial hand-tracing measurements. Results The mean age of patients was 50±16 years, 35.4% were male, mean body surface area was 1.62±0.18m2, 92.1% were in sinus rhythm, and 61.4% had good acoustic window. Table 1 shows the LV end-diastolic volume (EDV), end-systolic volume (ESV) and EF, measured using different method, by the 3 operators. There were excellent correlation and agreement between semi-automated tracing measurements and hand-tracing measurements of LV EDV (r=0.985, LOA [mean ± 1.96 SD] 16.9 ml, ICC 0.991), ESV (r=0.990, LOA 12.7 ml, ICC 0.994) and EF (r=0.962, LOA 7.43%, ICC 0.967) by experienced cardiologist. The limit of agreement (LOA) between cardiologist and sonographer for semi-automated tracing measurement of LV EDV, ESV and EF were 29.13 ml, 19.74 ml and 9.25% respectively, which was comparable with that of hand-tracing measurement. The agreement between cardiologist and fellow-in-training for semi-automated tracing measurement of LV volumes and EF was slightly better than hand-tracing method, with a LOA of 25.60 ml, 17.48 ml and 7.08%, for EDV, ESV and EF respectively (Table 2). Conclusion In daily clinical practice, measurement of LV volumes and EF using semi-automated LV endocardial tracing method is accurate and demonstrates comparable reproducibility with hand-tracing Biplane Simpson method among operators with different level of experience in echocardiography. Funding Acknowledgement Type of funding sources: None.

Dual mode piezoelectric lithotripter for efficient breakup of urinary stones

The coalescence and dispersion of cavitation bubbles through Bjerknes forces created by supplemental low amplitude acoustic fields has been shown to greatly improve the efficiency of shockwave lithotripsy for breaking urinary stones. Unfortunately, the large size of extracorporeal lithotripters typically leaves little acoustic window for additional transducers to create these fields. In this study, we explored the feasibility of using a piezoelectric lithotripter transducer in a dual mode generating both shockwaves for stone comminution and low amplitude tone bursts for bubble coalescence and dispersion. A piezoelectric lithotripter head and driver unit (piezolith 3000) was provided by the manufacturer (Richard Wolf GmbH). A custom class-D driver circuit was constructed from very high voltage blocking IGBTs and wired in parallel with the manufacturer’s excitation circuit for shockwave generation. Acoustic output was measured with a fiber optic probe hydrophone at the focus in a tank of degassed water. The driver produced acceptable 200 kHz tone bursts of 5–100 cycles up to at least 1 MPa amplitude. Lithotripter power settings 1–3 could be safely used with the combined driver and were sufficient to break model begostones in vitro. Future studies will compare efficiency of stone comminution using the dual mode system.

Multimodality imaging and clinical significance of isolated congenital absence of the pericardium

Background. Congenital absence of the pericardium is a rare anomaly characterized by variable and non-specific clinical manifestations. The prevalence of this pathology in the population is approximately 0.0001 – 0.044% and it is almost three times more common in men. However, the real prevalence, including asymptomatic and undiagnosed cases, may be higher. Purpose – highlighting the echocardiographic and tomographic signs of isolated congenital absence of the pericardium. Materials and methods. A 42-year-old patient M. Echocardiography did not permit to obtain standard echo images via typical echocardiographic approaches due to poor acoustic window. Magnetic resonance imaging and computed tomography of the heart revealed marked left heart rotation and confirmed the most common variant of congenital absence of the pericardium, that is complete left-sided absence pericardial agenesis. Results. The presented case illustrates the non-specificity of clinical symptoms in patients with congenital absence of the pericardium. The electrocardiogram of the patient showed right axis deviation, right bundle branch block, poor R wave progression in the precordial leads. Chest X-ray in the anterior-posterior projection typically shows a pronounced displacement of cardiac silhouette to the left without deviation of the trachea, elongated left border of the heart and inability to delineate the right border, indicating left heart rotation. Echocardiography revealed an unusual orientation of the heart in the chest, i.e. the displacement of the heart (particularly, of the apical segments) to the left and backwards. In cases when the pericardium is absent on the right and on both sides, the right ventricle can indeed be enlarged, sometimes there is a paradoxical motion of the interventricular septum, severe tricuspid regurgitation as well as the swinging motion of the cardiac apex. Magnetic resonance imaging and computed tomography of the heart enable detection of the displacement of the heart to the left half of the chest with cardiac apex directed backwards, the interposition of lung tissue between the ascending aorta and the pulmonary artery trunk. Conclusions. Congenital absence of the pericardium is a rare pathology and thus it can be challenging in terms of diagnosis, while sometimes it remains undiagnosed. The combination of echocardiography with magnetic resonance imaging and/or computed tomography allows to accurately diagnose congenital absence of the pericardium and assess the risks associated with it. Most patients with complete unilateral or bilateral congenital absence of the pericardium have a favorable prognosis and do not require treatment.

Prediction and measurement of acoustic transmission loss of acoustic window with composite sandwich structure

Underwater acoustic detection sensors are mounted on the outside of the submarine; the acoustic window for protecting these sensors must be structurally robust while also minimizing any deterioration of sensor's sound detection performance. These two conditions are typically satisfied simultaneously by using composite materials with acoustic window materials. However, since such composite material is manufactured by laminating fibers, there is the probability that delamination occurs, in which an air layer is formed inside, due to manufacturing process errors. Delamination inside the acoustic window degrades the sensor's acoustic performance and results in a failure of military operations. In the case of composites composed of sandwich structures located in the central part, the possibility of internal delamination is higher than in a single composite material. Therefore, it is very important to discriminate the presence or absence of internal delamination after producing an acoustic window. This article uses numerical and analytical methods to determine the internal delamination of the acoustic window fabricated with a sandwich structure. In addition, the results were analyzed and compared through ultrasonic measurement and acoustic transmission loss test.

Bladder Point-of-Care Ultrasound: A Time Saver in the Pediatric Emergency Department.

Pediatric patients undergoing transabdominal pelvic ultrasound require a full bladder as an acoustic window. Patients are typically relied upon to subjectively identify bladder fullness, but inaccurate reporting often leads to delays in test results, diagnosis, and treatment. Our aim was to objectively evaluate bladder fullness by comparing the height of the bladder to the height of the uterus on point-of-care ultrasound (POCUS). Our hypothesis was that this method would result in faster time to imaging and decrease emergency department length of stay (ED LOS). Bladder fullness was assessed using POCUS every 30 min until the bladder was full. If the height of the bladder was equal to or greater than the height of the uterus in the sagittal view, the bladder was considered full. The POCUS group was compared with a control group that relied solely on patients' self-identified bladder fullness. Females aged 8-18 years old with pelvic pain in the pediatric ED were included in the study. Forty POCUS patients were compared with a control group of 105 patients. The POCUS group demonstrated a decrease in time to pelvic imaging by 38.7 min (95% confidence interval -59.2 to -18.2; p < 0.0001) and a decrease in LOS by 49.2 min (95% CI -89.7 to -8.61; p = 0.004). There was poor overall agreement on bladder fullness between patient's subjective sensation and POCUS (k = 0.04). POCUS to evaluate bladder fullness by comparing the height of the bladder with the height of the uterus reduces time to pelvic imaging and ED LOS.

Dual-Use Transducer for Ultrasound Imaging and Pulsed Focused Ultrasound Therapy.

Pulsed focused ultrasound (pFUS) uses short acoustic pulses delivered at low duty cycle and moderate intensity to noninvasively apply mechanical stress or introduce disruption to tissue. Ultrasound-guided pFUS has primarily been used for inducing cavitation at the focus, with or without contrast agents, to promote drug delivery to tumors. When applied in tandem with contrast agents, pFUS is often administered using an ultrasound imaging probe, which has a small footprint and does not require a large acoustic window. The use of nonlinear pFUS without contrast agents was recently shown to be beneficial for localized tissue disruption, but required higher ultrasound pressure levels than a conventional ultrasound imaging probe could produce. In this work, we present the design of a compact dual-use 1-MHz transducer for ultrasound-guided pFUS without contrast agents. Nonlinear pressure fields that could be generated by the probe, under realistic power input, were simulated using the Westervelt equation. In water, fully developed shocks of 42-MPa amplitude and peak negative pressure of 8 MPa were predicted to form at the focus at 458-W acoustic power or 35% of the maximum reachable power of the transducer. In absorptive soft tissue, fully developed shocks formed at higher power (760 W or 58% of the maximum reachable power) with the shock amplitude of 33 MPa and peak negative pressure of 7.5 MPa. The electronic focus-steering capabilities of the array were evaluated and found to be sufficient to cover a target with dimensions of 19 mm in axial direction and 44 mm in transversal direction.

Design and Analysis of an Active Reflection Controller That Can Reduce Acoustic Signal Refer to the Angle of Incidence.

Techniques for reducing the reflection of acoustic signals have recently been actively studied. Most methods for reducing acoustic signals were studied using the normal-incidence wave reduction technique. Although the technique of canceling an object from the normal incidence wave is essential, research on reducing acoustic signals according to the angle of incidence is required for practical applications. In this study, we designed, fabricated, and experimented with an active reflection controller that can reduce acoustic signals according to the angle of incidence. The controller consists of a transmitter on one layer, a receiver sensor on two layers, and an acoustic window on three layers. To reduce the reflected signal, a combination of the time delay and phase was applied to the controller to minimize the acoustic signal by up to −23 dB at an angle of 10°. A controller array simulation was performed based on the results of a controlled experiment. In conclusion, our proposed controller can reduce acoustic signals according to the angle of incidence, which makes it suitable for many applications.

The Crossed-leg Position Increases the Dimensions Within the Acoustic Target Window for Neuraxial Needle Placement in Term Pregnancy: A Prospective Observational Study

(Int J Obstet Anesth. 2020;44:106–111) Anatomic changes associated with pregnancy may render conduct of neuraxial procedures in parturients more difficult. The standard position for a neuraxial block requires a patient to sit on a bed with the spine flexed and legs supported on a stool, but spinal flexion may be improved by instead sitting cross-legged on the bed. Given the lack of prospective studies on this topic, the aim of this study was ultrasonographic assessment of the paramedian target area’s size when a pregnant woman sits in the cross-legged position (CLP) for neuraxial needle placement compared with standard sitting position (SP). The authors hypothesized that a CLP would increase the measured lengths of the posterior longitudinal ligament (PLL) indicating an improved acoustic window between vertebrae.