Frame rate required for speckle tracking echocardiography: A quantitative clinical study with open-source, vendor-independent software

Background Assessing left ventricular function with speckle tracking is useful in patient diagnosis but requires a temporal resolution that can follow myocardial motion. In this study we investigated the effect of different frame rates on the accuracy of speckle tracking results, highlighting the temporal resolution where reliable results can be obtained. Material and methods 27 patients were scanned at two different frame rates at their resting heart rate. From all acquired loops, lower temporal resolution image sequences were generated by dropping frames, decreasing the frame rate by up to 10-fold. Results Tissue velocities were estimated by automated speckle tracking. Above 40 frames/s the peak velocity was reliably measured. When frame rate was lower, the inter-frame interval containing the instant of highest velocity also contained lower velocities, and therefore the average velocity in that interval was an underestimate of the clinically desired instantaneous maximum velocity. Conclusions The higher the frame rate, the more accurately maximum velocities are identified by speckle tracking, until the frame rate drops below 40 frames/s, beyond which there is little increase in peak velocity. We provide in an online supplement the vendor-independent software we used for automatic speckle-tracked velocity assessment to help others working in this field

Open-source, vendor-independent, automated multi-beat tissue Doppler echocardiography analysis

Current guidelines for measuring cardiac function by tissue Doppler recommend using multiple beats, but this has a time cost for human operators. We present an open-source, vendor-independent, drag-and-drop software capable of automating the measurement process. A database of ~8000 tissue Doppler beats (48 patients) from the septal and lateral annuli were analyzed by three expert echocardiographers. We developed an intensity- and gradient-based automated algorithm to measure tissue Doppler velocities. We tested its performance against manual measurements from the expert human operators. Our algorithm showed strong agreement with expert human operators. Performance was indistinguishable from a human operator: for algorithm, mean difference and SDD from the mean of human operators’ estimates 0.48 ± 1.12 cm/s (R2= 0.82); for the humans individually this was 0.43 ± 1.11 cm/s (R2= 0.84), −0.88 ± 1.12 cm/s (R2= 0.84) and 0.41 ± 1.30 cm/s (R2= 0.78). Agreement between operators and the automated algorithm was preserved when measuring at either the edge or middle of the trace. The algorithm was 10-fold quicker than manual measurements (p < 0.001). This open-source, vendor-independent, drag-and-drop software can make peak velocity measurements from pulsed wave tissue Doppler traces as accurately as human experts. This automation permits rapid, bias-resistant multi-beat analysis from spectral tissue Doppler images.European Research Council and British Heart Foundatio

Sex difference and intra-operative tidal volume: Insights from the LAS VEGAS study

BACKGROUND: One key element of lung-protective ventilation is the use of a low tidal volume (VT). A sex difference in use of low tidal volume ventilation (LTVV) has been described in critically ill ICU patients.OBJECTIVES: The aim of this study was to determine whether a sex difference in use of LTVV also exists in operating room patients, and if present what factors drive this difference.DESIGN, PATIENTS AND SETTING: This is a posthoc analysis of LAS VEGAS, a 1-week worldwide observational study in adults requiring intra-operative ventilation during general anaesthesia for surgery in 146 hospitals in 29 countries.MAIN OUTCOME MEASURES: Women and men were compared with respect to use of LTVV, defined as VT of 8 ml kg-1 or less predicted bodyweight (PBW). A VT was deemed 'default' if the set VT was a round number. A mediation analysis assessed which factors may explain the sex difference in use of LTVV during intra-operative ventilation.RESULTS: This analysis includes 9864 patients, of whom 5425 (55%) were women. A default VT was often set, both in women and men; mode VT was 500 ml. Median [IQR] VT was higher in women than in men (8.6 [7.7 to 9.6] vs. 7.6 [6.8 to 8.4] ml kg-1 PBW, P &lt; 0.001). Compared with men, women were twice as likely not to receive LTVV [68.8 vs. 36.0%; relative risk ratio 2.1 (95% CI 1.9 to 2.1), P &lt; 0.001]. In the mediation analysis, patients' height and actual body weight (ABW) explained 81 and 18% of the sex difference in use of LTVV, respectively; it was not explained by the use of a default VT.CONCLUSION: In this worldwide cohort of patients receiving intra-operative ventilation during general anaesthesia for surgery, women received a higher VT than men during intra-operative ventilation. The risk for a female not to receive LTVV during surgery was double that of males. Height and ABW were the two mediators of the sex difference in use of LTVV.TRIAL REGISTRATION: The study was registered at Clinicaltrials.gov, NCT01601223

Domain walls in ferromagnetic nanowires for atom trapping applications

In this thesis I demonstrate that is possible to transport DWs in ferromagnetic nanowires at arbitrarily low velocities. The approach used here is to confine the DWs into geometrically defined energy minima. DWs are transported by applying a rotating field. The velocity at which the DWs travel depends on the ring radius and the frequency of the applied field. Several rings of different widths were analysed under different applied fields and a range of frequencies of the applied field. The results show that the walls are pinned by defects as they travel in the ring. The defects cause the walls to lag behind the vector field. The lag depends strongly on the field strength, so that at higher fields the walls move smoother. On the other hand, a high field would cant the magnetic moments in the ring and widen the DW. Also the frequency of the applied field influences the local velocity when DWs depin from defects and a method of calculating this local velocity was described. The analysis is extended further to a structure which allows linear transport of DWs still at low velocities. The structure is based on the analysis presented for rings, where rotating fields drive the DWs in the structure. By applying successive clockwise and anticlockwise fields, the walls travel through half-rings over large distances. Finally, multi-ring structures are analysed to study the influence of large periodic pinning of DWs across a correlated system. This is relevant in the light of interacting magnetic systems as well as to DW atom trapping as a means of stimulating collisional atomic interactions. Neighbour rings in this kind of structures can introduce DWs into other rings through junctions. Also, due to pinning, DWs might also annihilate. In low fields, each field cycle the number of DWs can be different

Magneto-optic Kerr microscopy (MOKE)

This resource is a Power Pont presentation with embedded audio and animations on magneto-optic Kerr microscopy. Magneto-optic Kerr effect (MOKE) is one of the magneto-optic effects; it describes the changes of light reflected from magnetized media. A Kerr microscope relies on the MOKE in order to image differences in magnetic orientation. In addition to a regular optical microscope, a polarizer and analyzer are needed as a source and sensor for polarized light.

A method for determining local pulse wave velocity in human ascending aorta from sequential ultrasound measurements of diameter and velocity

BACKGROUND:Pulse wave velocity (PWV) is an indicator of arterial stiffness, and predicts cardiovascular events independently of blood pressure. Currently, PWV is commonly measured by the foot-to-foot technique thus giving a global estimate of large arterial stiffness. However, and despite its importance, methods to measure the stiffness of the ascending aorta are limited. OBJECTIVE:To introduce a method for calculating local PWV in the human ascending aorta using non-invasive ultrasound measurements of its diameter (D) and flow velocity (U). APPROACH:Ten participants (four females) were recruited from Brunel University students. Ascending aortic diameter and velocity were recorded with a GE Vivid E95 equipped with a 1.5-4.5 MHz phased array transducer using M-mode in the parasternal long axis view and pulse wave Doppler in the apical five chamber view respectively. Groups of six consecutive heartbeats were selected from each 20 s run based on the most similar cycle length resulting in three groups for D and three for U each with six waveforms. Each D waveform was paired with each U waveform to calculate PWV using ln(D)U-loop method. MAIN RESULTS:The diastolic portions of the diameters or velocities waveforms were truncated to allow the pairs to have equal length and were used to construct ln(D)U-loops. The trimmed average, excluding 10% of extreme values, resulting from the 324 loops was considered representative for each participant. Overall mean local PWV for all participants was 4.1(SD  =  0.9) m s-1. SIGNIFICANCE:Local PWV can be measured non-invasively in the ascending aorta using ultrasound measurements of diameter and flow velocity This should facilitate more widespread assessment of ascending aortic stiffness in larger studies

Non-invasive Technique for Determining Local Pulse Wave Velocity in Humans Ascending Aorta

Background: Pulse wave velocity (PWV) is a measure of arterial stiffness and widely used as a predictor of cardiovascular risk. Local PWV (lPWV) can be calculated non-invasively using the ln(D)U-loop method. Aim: To develop a novel non-invasive technique for the determination of lPWV in human ascending aorta. Methods: 13 healthy volunteers (19-33 years, 6 females) were studied using ultrasound (GE, Vivid E95) with a 1.5–4.5 MHz phased array transducer. M-mode in the parasternal long axis view was used for diameter measurements, Pulsed Wave Doppler ultrasound in the apical 5 chamber view was used for blood velocity measurements in the ascending aorta. Diameter and flow were measured sequentially. The ln(D)U-loop method was used to determine lPWV, and the SphygmoCor Xcel (AtCor Medical, Australia) was used to measure carotid-femoral PWV (cfPWV). Results: Mean lPWV using ln(D)U-loop was 3.6±0.7 m/s with higher values for men compared to women. The results showed that lPWV was systematically lower than cfPWV. Conclusions: lPWV can be measured non-invasively at the ascending aorta by ultrasound with sequential recordings of diameter and velocity using the ln(D)Uloop method

Semi-automatic Vendor-Independent Software for Assessment of Local Arterial Stiffness

Background: Stiffened arteries represent a major cardiovascular risk. Aim: We describe a vendor independent software for the non-invasive determination of arterial stiffness using ultrasound images. Methods: We have developed an intensity-based semiautomatic software for determining the edges of the luminal arterial walls (M-mode) and blood velocity (PW Doppler) to extract diameter and velocity waveform from ultrasound images. The upstroke of the two waveforms is automatically determined as well as the fit of the initial linear portion of the ln(D)U-loop. Pulse wave velocity (PWV), which is proportional to the slope of ln(D)U-loop during early systole is calculated as a measure of arterial stiffness. The user can over-ride and correct the automatically determined parameters if necessary. Results: A semi-automatic code was developed for tracing the luminal diameter and blood velocity in the human ascending aorta. D and U waveforms were extracted and used in ln(D)U-loops to calculate PWV. Conclusions: The software described here can be used to assess, local aortic stiffness non-invasively, by using ultrasound measurements/images of the diameter and velocity waveforms

How Many Times Can One Go Back to the Drawing Board before the Accurate Diagnosis and Surgical Treatment of Glucagonoma?

Glucagonomas are neuroendocrine tumors (NETs) that arise from the alpha cells of the pancreatic islets. They are typically slow-growing tumors associated with abnormal glucagon secretion, resulting in one or more non-specific clinical features, such as necrolytic migratory erythema (NME), diabetes, diarrhea, deep vein thrombosis, weight loss, and depression. Here, we report the case of a 44-year-old male with a history of diabetes mellitus, presenting with a pruritic and painful disseminated cutaneous eruption of erythematous plaques, with scales and peripheral pustules, misdiagnosed as disseminated pustular psoriasis and treated for 2 years with oral retinoid and glucocorticoids. During this period, the patient complained of weight loss of 32 kg and diarrhea and developed deep vein thrombosis. These symptoms, together with an inadequate response to therapy of the skin lesions, led to the reassessment of the initial diagnosis. Laboratory tests confirmed elevated plasma glucagon levels (>1000 pg/mL) and computed tomography (CT) scans revealed a 35/44 mm tumor in the pancreatic tail. Due to considerable disease complications and the COVID-19 pandemic, the surgical removal of the tumor was delayed for nearly 2 years. During this time, somatostatin analogue therapy efficiently controlled the glucagonoma syndrome and likely prevented tumor progression. As in other functional pancreatic NETs, the early clinical recognition of hormonal hypersecretion syndrome and the multidisciplinary approach are the keys for best patient management