Trigger Delay Research Articles

Measurement of the timing behaviour of off-the-shelf cameras

This paper presents a measurement method suitable for investigating the timing properties of cameras. A single light source illuminates the camera detector starting with a varying defined delay after the camera trigger. Pixels from the recorded camera frames are summed up and normalised, and the resulting function is indicative of the overlap between illumination and exposure. This allows one to infer the trigger delay and the exposure time with sub-microsecond accuracy. The method is therefore of interest when off-the-shelf cameras are used in reactive systems or synchronised with other cameras. It can supplement radiometric and geometric calibration methods for cameras in scientific use. A closer look at the measurement results reveals deviations from the ideal camera behaviour of constant sensitivity limited to the exposure interval. One of the industrial cameras investigated retains a small sensitivity long after the end of the nominal exposure interval. All three investigated cameras show non-linear variations of sensitivity at to during exposure. Due to its sign, the latter effect cannot be described by a sensitivity function depending on the time after triggering, but represents non-linear pixel characteristics.

A comparison of leak compensation in six acute care ventilators during non-invasive ventilation

Objective: To compare the ability of leak compensation in 6 medical ventilators during non-invasive ventilation. Methods: Six medical ventilators were selected, including 3 non-invasive ventilators (V60, Flexo and Stellar150), and 3 invasive ventilators(Avea, Servo I and BellaVist). Using a lung simulator, the ability of leak compensation was evaluated during triggering and cycling in 2 respiratory mechanics conditions (high airway resistance condition and high elastance resistance condition), and each condition was performed under 2 PEEP levels (4, and 8 cmH(2)O, 1 mmHg=0.098 kPa) at 4 air leak level conditions (L0: 2-3 L/min, L1: 8-10 L/min, L2: 22-27 L/min, L3: 35-40 L/min). Results: In the high elastance resistance condition (L2, L3)with different leak levels, the number of auto-triggering and miss-triggering of the non-invasive ventilator Flexo was significantly less than those of the others (L2: 1, 1; L3: 1.67, 1.33, P<0.01), and had better synchronization (L2: 2.33, 2.33; L3: 3.33, 3.33, P<0.01). In the high airway resistance condition with PEEP 4 cmH(2)O, V60 had less number of auto-triggering than other ventilators (P<0.01), while in the high airway resistance condition with PEEP 8 cmH(2)O, Stellar150 had less number of miss-triggering than other ventilators (1, 0.67, 0, P<0.01). Flexo had a shorter trigger delay time than other ventilators in both high airway resistance and high elastance resistance conditions with L0 and L1 leak levels and PEEP levels [ARDS, PEEP=4: (109.8±1.8) ms, (112.0±0.6) ms; ARDS, PEEP=8: (103.1±0.7) ms, (109.7±0.7) ms; COPD, PEEP=4: (207.3±1.1) ms, (220.8±1.1) ms; COPD, PEEP=8: (195.6±6.7) ms, (200.0±1.2) ms , P<0.01]. Stellar150 had the shortest trigger delay time in high airway resistance condition with PEEP 4 cmH(2)O and high leak level L3[(262.8±0.8) ms , P<0.01]. V60 had a good performance on trigger delay time in high elastance resistance condition with PEEP 4 and 8 cmH(2)O, and also was most stable in increasing leak levels. Conclusion: In high airway resistance and high elastance resistance conditions with different PEEP levels and leak levels, V60, Stellar150, Flexo and BellaVista ventilators could be synchronized, among which V60, Stellar150 and Flexo presented a good performance features in specific conditions.

A diaphragmatic electrical activity-based optimization strategy during pressure support ventilation improves synchronization but does not impact work of breathing

BackgroundPoor patient-ventilator synchronization is often observed during pressure support ventilation (PSV) and has been associated with prolonged duration of mechanical ventilation and poor outcome. Diaphragmatic electrical activity (Eadi) recorded using specialized nasogastric tubes is a surrogate of respiratory brain stem output. This study aimed at testing whether adapting ventilator settings during PSV using a protocolized Eadi-based optimization strategy, or Eadi-triggered and -cycled assisted pressure ventilation (or PSVN) could (1) improve patient-ventilator interaction and (2) reduce or normalize patient respiratory effort as estimated by the work of breathing (WOB) and the pressure time product (PTP).MethodsThis was a prospective cross-over study. Patients with a known chronic pulmonary obstructive or restrictive disease, asynchronies or suspected intrinsic positive end-expiratory pressure (PEEP) who were ventilated using PSV were enrolled in the study. Four different ventilator settings were sequentially applied for 15 minutes (step 1: baseline PSV as set by the clinician, step 2: Eadi-optimized PSV to adjust PS level, inspiratory trigger, and cycling settings, step 3: step 2 + PEEP adjustment, step 4: PSVN). The same settings as step 3 were applied again after step 4 to rule out a potential effect of time. Breathing pattern, trigger delay (Td), inspiratory time in excess (Tiex), pressure-time product (PTP), and work of breathing (WOB) were measured at the end of each step.ResultsEleven patients were enrolled in the study. Eadi-optimized PSV reduced Td without altering Tiex in comparison with baseline PSV. PSVN reduced Td and Tiex in comparison with baseline and Eadi-optimized PSV. Respiratory pattern did not change during the four steps. The improvement in patient-ventilator interaction did not lead to changes in WOB or PTP.ConclusionsEadi-optimized PSV allows improving patient ventilator interaction but does not alter patient effort in patients with mild asynchrony.Trial registrationClinicaltrials.gov identifier: NCT 02067403. Registered 7 February 2014.

Performance of the New Turbine Mid-Level Critical Care Ventilators

During recent years, ventilators using turbines as flow-generating systems have become increasingly more relevant. This bench study was designed to compare triggering and pressurization of 7 turbine mid-level ICU ventilators. We used a dual-chamber lung model to test 7 mid-level ICU ventilators in pressure support mode with levels of 10, 15, and 20 cm H2O with 2 PEEP levels of 5 cm H2O and the minimum level allowed by the ventilator. A ventilator was connected to the master chamber to simulate 2 different effort levels. Pressure drop, trigger delay time, time to minimum pressure, and pressure time products (PTP) during trigger and the first 300 and 500 ms were analyzed. In the trigger evaluation, the Savina had the highest delay time, whereas the C2, the V60, and the Trilogy had the lowest pressure drops and PTP values in both effort levels. In pressurization capacity assessment using ideal PTP300 and PTP500 percentages, the C2 and the V680 had the best results, and the Carina and the Savina had lower values, with no differences between both effort levels. Differences between PEEP levels did not seem to be relevant. Pressure support mode for tested ventilators worked properly, but pressurization capacity and trigger function performance were clearly superior in the newest machines. The use of PEEP did not modify the results.

Effect of non-invasive NAVA on the patients with acute exacerbation of chronic obstructive pulmonary disease

Objective: To observe the effect of non-invasive neurally adjusted ventilatory assist (NIV-NAVA) on patient-ventilator synchrony and effect of gas exchange in patients with acute exacerbation of chronic obstructive pulmonary disease compared with NIV-pressure support ventilation (PSV). Methods: This was a prospective study of 40 patients with AECOPD given 30-min trials of NIV with NIV-PSV group (n=20) and NAVA group (n=20) in random order. Arterial blood gas analysis (ABGs), main asynchrony events and asynchrony index were quantified. Results: There were no significant difference between the two groups on effect of gas exchange (P>0.05). Main asynchrony events during NIV-NAVA including autotriggering, ineffective efforts and double triggering were less frequent than NIV-PSV (P<0.05). The trigger delay in the NIV-NAVA group was markedly shorter than the NIV-PSV (62.20±8.91 vs 112.65±15.10)ms (P<0.001). The inspiratory/expiratory off-cycle delay was significantly shorter in the NIV-PSV group than that in the NIV-NAVA group (73.00±18.27 vs 187.95±39.24)ms (P<0.001). The occurrence of severe asynchrony (AI>10%) was also less under NAVA (P<0.05). Conclusions: Both NIV-NAVA and NIV-PSV can improve gas exchange. As compared with NIV-PSV, NIV-NAVA can reduce main asynchrony events, improve patient-ventilator synchrony in patients with AECOPD.

Synchronization of multiple USB 3.0 devices using Isochronous Timestamp Packet

In test and measurement, synchronizing multiple devices to timely coordinate data acquisition is crucial. This is due to the limited number of channels on a single device and the need for mixed-signal channels. Currently, various techniques have been proposed for triggering and synchronization among multiple devices such as GPIB, VXI, PXI/PXIe and LXI. However, they are expensive and need large footprint and additional cable or hardware to set up. Due to that, with the low cost and easy-to-setup USB 2.0, it is enhanced to have synchronization ability. There are various synchronization methods in USB 2.0 such as software-timed trigger, external hardware trigger and USB-inSync. The software-timed trigger is purely implemented in software and has high trigger delay, which is up to microseconds. Besides that, for both external hardware trigger and USB-inSync, they can achieve up to nanoseconds of synchronization precision. However, both of those methods need extra hardware or setup to synchronize multiple devices. In this paper, to overcome the drawbacks from the existing techniques, a trigger algorithm is proposed based on the study of USB 3.0 technology. The Isochronous Timestamp Packet (ITP) in USB 3.0 is used as the main component in the trigger algorithm. Without any hardware implementation, the trigger algorithm is able to trigger multiple USB 3.0 devices with a trigger delay around 200ns. In addition, the trigger algorithm can support up to maximum to three consecutive connected hubs without affecting the performance. In conclusion, the trigger algorithm increases the performance of synchronization of multiple USB device with only software intervention.

SU‐F‐T‐263: Dosimetric Characteristics of the Cine Acquisition Mode of An A‐Si EPID

Purpose:To investigate the dosimetric characteristics of Varian a‐Si‐500 electronic portal imaging device (EPID) operated in cine mode particularly considering linearity with delivered dose, dose rate, field size, phantom thickness, MLC speed and common IMRT fields.Methods:The EPID that attached to a Varian Clinac 21iX linear accelerator, was irradiated with 6 and 18 MV using 600 MU/min. Image acquisition is controlled by the IAS3 software, Trigger delay was 6 ms, BeamOnDelay and FrameStartDelay were zero. Different frame rates were utilized. Cine mode response was calculated using MATLAB as summation of mean pixel values in a region of interest of the acquired images. The performance of cine mode was compared to integrated mode and dose measurements in water using CC13 ionization chamber.Results:Figure1 illustrates that cine mode has nonlinear response for small MU, when delivering 10 MU was about 0.5 and 0.64 for 6 and 18 MV respectively. This is because the missing acquired images that were calculated around four images missing in each delivery. With the increase MU the response became linear and comparable with integrated mode and ionization chamber within 2%. Figure 2 shows that cine mode has comparable response with integrated mode and ionization chamber within 2% with changing dose rate for 10 MU delivered. This indicates that the dose rate change has no effect on nonlinearity of cine mode response. Except nonlinearity, cine mode is well matched to integrated mode response within 2% for field size, phantom thickness, MLC speed dependences.Conclusion:Cine mode has similar dosimetric characteristics to integrated mode with open and IMRT fields, and the main limitation with cine mode is missing images. Therefore, the calibration of EPID images with this mode should be run with large MU, and when IMRT verification field has low MU, the correction for missing images are required.

Patient-Ventilator Asynchrony During Assisted Ventilation in Children.

To describe the frequency and type of patient-ventilator asynchrony in mechanically ventilated children by analyzing ventilator flow and pressure signals. Prospective observational study. Tertiary PICU in a university hospital. Mechanically ventilated children between 0 and 18 years old and who were able to initiate and maintain spontaneous breathing were eligible for inclusion. Patients with congenital or acquired neuromuscular disorders, those with congenital or acquired central nervous system disorders, and those who were unable to initiate and maintain spontaneous breathing from any other cause were excluded. None. All patients were ventilated in a time-cycled, pressure-limited mode with flow triggering set at 1.0 L/min by using the Evita XL (Dräger, Lubeck, Germany). Patient-ventilator asynchrony was identified by a random 30-minute continuous recording and an offline analysis of the flow and pressure signals. Patient-ventilator asynchrony was categorized and labeled into four different groups: 1) trigger asynchrony (i.e., insensitive trigger, double triggering, autotriggering, or trigger delay), 2) flow asynchrony, 3) termination asynchrony (i.e., delayed or premature termination), and 4) expiratory asynchrony. Flow and pressure signals were recorded in 45 patients for 30 minutes. A total number of 57,651 breaths were analyzed. Patient-ventilator asynchrony occurred in 19,175 breaths (33%), and it was seen in every patient. Ineffective triggering was the most predominant type of asynchrony (68%), followed by delayed termination (19%), double triggering (4%), and premature termination (3%). Patient-ventilator asynchrony significantly increased with lower levels of peak inspiratory pressure, positive end-expiratory pressure, and set frequency. Patient-ventilator asynchrony is extremely common in mechanically ventilated children, and the predominant cause is ineffective triggering.

Accuracy of delivered airway pressure and work of breathing estimation during proportional assist ventilation: a bench study.

BackgroundProportional assist ventilation+ (PAV+) delivers airway pressure (Paw) in proportion to patient effort (Pmus) by using the equation of motion of the respiratory system. PAV+ calculates automatically respiratory mechanics (elastance and resistance); the work of breathing (WOB) is estimated by the ventilator. The accuracy of Pmus estimation and hence accuracy of the delivered Paw and WOB calculation have not been assessed. This study aimed at assessing the accuracy of delivered Paw and calculated WOB by PAV+ and examining the factors influencing this accuracy.MethodsUsing an active lung model with different respiratory mechanics, we compared (1) the actual delivered Paw by the ventilator to the theoretical Paw as defined by the equation of motion and (2) the WOB value displayed by the ventilator to the WOB measured from a Campbell diagram.ResultsIrrespective of respiratory mechanics and gain, the ventilator provided a Paw approximately 25 % lower than expected. This underassistance was greatest at the beginning of the inspiration. Intrinsic PEEP (PEEPi), associated with an increase in trigger delay, was a major factor affecting PAV+ accuracy. The absolute value of total WOB displayed by the ventilator was underestimated, but the changes in WOB were accurately detected by the ventilator.ConclusionThe assistance provided by PAV+ well follows Pmus but with a constant underassistance. This is associated with an underestimation by the ventilator of the WOB. PEEPi can be a major factor contributing to PAV+ inaccuracy. Clinical recommendations should include using a high trigger sensitivity and a careful PEEP titration.Electronic supplementary materialThe online version of this article (doi:10.1186/s13613-016-0131-y) contains supplementary material, which is available to authorized users.

Work of breathing using different interfaces in spontaneous positive pressure ventilation: helmet, face-mask, and endotracheal tube.

Noninvasive positive pressure ventilation (NPPV) using a helmet is expected to cause inspiratory trigger delay due to the large collapsible and compliant chamber. We compared the work of breathing (WOB) of NPPV using a helmet or a full face-mask with that of invasive ventilation by tracheal intubation. We used a lung model capable of simulating spontaneous breathing (LUNGOO; Air Water Inc., Japan). LUNGOO was set at compliance (C)=50mL/cmH2O and resistance (R)=5cmH2O/L/s for normal lung simulation, C=20mL/cmH2O and R=5cmH2O/L/s for restrictive lung, and C=50mL/cmH2O and R=20cmH2O/L/s for obstructive lung. Muscle pressure was fixed at25cmH2O and respiratory rate at20bpm. Pressure support ventilation and continuous positive airway pressure were performed with each interface placed on a dummy head made of reinforced plastic that was connected to LUNGOO. We tested the inspiratory WOB difference between the interfaces with various combinations of ventilator settings (positive end-expiratory pressure 5cmH2O; pressure support 0, 5, and 10cmH2O). In the normal lung and restrictive lung models, WOB decreased more with the face-mask than the helmet, especially when accompanied by the level of pressure support. In the obstructive lung model, WOB with the helmet decreased compared with the other two interfaces. In the mixed lung model, there were no significant differences in WOB between the three interfaces. NPPV using a helmet is more effective than the other interfaces for WOB in obstructive lung disease.

Parameter optimization for reproducible cardiac 1 H-MR spectroscopy at 3 Tesla.

To optimize data acquisition parameters in cardiac proton MR spectroscopy, and to evaluate the intra- and intersession variability in myocardial triglyceride content. Data acquisition parameters at 3 Tesla (T) were optimized and reproducibility measured using, in total, 49 healthy subjects. The signal-to-noise-ratio (SNR) and the variance in metabolite amplitude between averages were measured for: (i) global versus local power optimization; (ii) static magnetic field (B0 ) shimming performed during free-breathing or within breathholds; (iii) post R-wave peak measurement times between 50 and 900 ms; (iv) without respiratory compensation, with breathholds and with navigator triggering; and (v) frequency selective excitation, Chemical Shift Selective (CHESS) and Multiply Optimized Insensitive Suppression Train (MOIST) water suppression techniques. Using the optimized parameters intra- and intersession myocardial triglyceride content reproducibility was measured. Two cardiac proton spectra were acquired with the same parameters and compared (intrasession reproducibility) after which the subject was removed from the scanner and placed back in the scanner and a third spectrum was acquired which was compared with the first measurement (intersession reproducibility). Local power optimization increased SNR on average by 22% compared with global power optimization (P = 0.0002). The average linewidth was not significantly different for pencil beam B0 shimming using free-breathing or breathholds (19.1 Hz versus 17.5 Hz; P = 0.15). The highest signal stability occurred at a cardiac trigger delay around 240 ms. The mean amplitude variation was significantly lower for breathholds versus free-breathing (P = 0.03) and for navigator triggering versus free-breathing (P = 0.03) as well as for navigator triggering versus breathhold (P = 0.02). The mean residual water signal using CHESS (1.1%, P = 0.01) or MOIST (0.7%, P = 0.01) water suppression was significantly lower than using frequency selective excitation water suppression (7.0%). Using the optimized parameters an intrasession limits of agreement of the myocardial triglyceride content of -0.11% to +0.04%, and an intersession of -0.15% to +0.9%, were achieved. The coefficient of variation was 5% for the intrasession reproducibility and 6.5% for the intersession reproducibility. Using approaches designed to optimize SNR and minimize the variation in inter-average signal intensities and frequencies/phases, a protocol was developed to perform cardiac MR spectroscopy on a clinical 3T system with high reproducibility. J. Magn. Reson. Imaging 2016;44:1151-1158.

Second-order motion compensated PRESS for cardiac spectroscopy.

Second-order motion compensation for point-resolved spectroscopy (PRESS) is proposed to allow for robust single-voxel cardiac spectroscopy throughout the entire cardiac cycle and at various heart rates. Bipolar FID spoiling gradient pairs compensating for first and second-order motion were designed and implemented into a cardiac-triggered PRESS sequence on a clinical MR system. A numerical three-dimensional model of cardiac motion was used to optimize and validate the gradient waveforms. In vivo measurements in healthy volunteers were obtained to assess the signal-to-noise ratio (SNR) and triglyceride-to-water ratio (TG/W). SNR gains and variability of TG/W of the proposed approach were evaluated against a conventional PRESS sequence with optimized gradients. The proposed sequence increases the mean SNR by 32% (W) and 23% (TG) on average with significantly lower variability for different trigger delays. The variability of TG/W quantification over the cardiac cycle is significantly decreased with second-order motion compensated PRESS when compared with conventional PRESS with reduced-spoiler gradients (coefficient of variation: 0.1 ± 0.02 versus 0.37 ± 0.26). Second-order motion compensated PRESS effectively reduces cardiac motion-induced signal degradation during FID spoiling, providing higher SNR and less variability for TG/W quantification. The sequence is considered promising to assess the TG/W modulation during various interventions including pharmacologically induced stress. Magn Reson Med 77:57-64, 2017. © 2016 Wiley Periodicals, Inc.

Streamlining trigger delay estimation for T1 mapping

Background T1 mapping in end diastole requires correct identification of the diastolic pause, and an appropriate input of the trigger delay time (TD) into acquisition parameters to ensure parametric mapping during the true diastolic pause for minimal motion-related blurring of myocardium. This diascan can be derived for individual patients from either the 4 chamber or the short axis stack. However, this additional step adds complexity and time to the scan and potentially introduces error. We investigated whether the TD could be estimated from the heart rate (HR) to simplify MOLLI acquisitions.

Variable ultrasound trigger delay for improved magnetic resonance acoustic radiation force imaging

Magnetic resonance acoustic radiation force imaging (MR-ARFI) allows the quantification of microscopic displacements induced by ultrasound pulses, which are proportional to the local acoustic intensity. This study describes a new method to acquire MR-ARFI maps, which reduces the measurement noise in the quantification of displacement as well as improving its robustness in the presence of motion.Two MR-ARFI sequences were compared in this study. The first sequence ‘variable MSG’ involves switching the polarity of the motion sensitive gradient (MSG) between odd and even image frames. The second sequence named ‘static MSG’ involves a variable ultrasound trigger delay to sonicate during the first or second MSG for odd and even image frames, respectively. As previously published, the data acquired with a variable MSG required the use of reference data acquired prior to any sonication to process displacement maps. In contrary, data acquired with a static MSG were converted to displacement maps without using reference data acquired prior to the sonication. Displacement maps acquired with both sequences were compared by performing sonications for three different conditions: in a polyacrylamide phantom, in the leg muscle of a freely breathing pig and in the leg muscle of pig under apnea.The comparison of images acquired at even image frames and odd image frames indicates that the sequence with a static MSG provides a significantly better steady state (p < 0.001 based on a Student’s t-test) than the images acquired with a variable MSG. In addition no reference data prior to sonication were required to process displacement maps for data acquired with a static MSG. The absence of reference data prior to sonication provided a 41% reduction of the spatial distribution of noise (p < 0.001 based on a Student’s t-test) and reduced the sensitivity to motion for displacements acquired with a static MSG. No significant differences were expected and observed for thermal maps acquired with a variable MSG and a static MSG.The use of a static MSG with a variable ultrasound trigger delay improves the ARFI displacement map quality without additional acquisition time and remains compatible with the simultaneous acquisition of MR thermal maps.

A physical action potential generator: design, implementation and evaluation.

The objective was to develop a physical action potential generator (Paxon) with the ability to generate a stable, repeatable, programmable, and physiological-like action potential. The Paxon has an equivalent of 40 nodes of Ranvier that were mimicked using resin embedded gold wires (Ø = 20 μm). These nodes were software controlled and the action potentials were initiated by a start trigger. Clinically used Ag-AgCl electrodes were coupled to the Paxon for functional testing. The Paxon's action potential parameters were tunable using a second order mathematical equation to generate physiologically relevant output, which was accomplished by varying the number of nodes involved (1–40 in incremental steps of 1) and the node drive potential (0–2.8 V in 0.7 mV steps), while keeping a fixed inter-nodal timing and test electrode configuration. A system noise floor of 0.07 ± 0.01 μV was calculated over 50 runs. A differential test electrode recorded a peak positive amplitude of 1.5 ± 0.05 mV (gain of 40x) at time 196.4 ± 0.06 ms, including a post trigger delay. The Paxon's programmable action potential like signal has the possibility to be used as a validation test platform for medical surface electrodes and their attached systems.

Monte Carlo calculations of PET coincidence timing: single and double-ended readout

We present Monte Carlo computational methods for estimating the coincidence resolving time (CRT) of scintillator detector pairs in positron emission tomography (PET) and present results for Lu2SiO5 : Ce (LSO), LaBr3 : Ce, and a hypothetical ultra-fast scintillator with a 1 ns decay time. The calculations were applied to both single-ended and double-ended photodetector readout with constant-fraction triggering. They explicitly include (1) the intrinsic scintillator properties (luminosity, rise time, decay time, and index of refraction), (2) the exponentially distributed depths of interaction, (3) the optical photon transport efficiency, delay, and time dispersion, (4) the photodetector properties (fill factor, quantum efficiency, transit time jitter, and single electron response), and (5) the determination of the constant fraction trigger level that minimizes the CRT. The calculations for single-ended readout include the delayed photons from the opposite reflective surface. The calculations for double-ended readout include (1) the simple average of the two photodetector trigger times, (2) more accurate estimators of the annihilation photon entrance time using the pulse height ratio to estimate the depth of interaction and correct for annihilation photon, optical photon, and trigger delays, and (3) the statistical lower bound for interactions at the center of the crystal. For time-of-flight (TOF) PET we combine stopping power and TOF information in a figure of merit equal to the sensitivity gain relative to whole-body non-TOF PET using LSO.For LSO crystals 3 mm × 3 mm × 30 mm, a decay time of 37 ns, a total photoelectron count of 4000, and a photodetector with 0.2 ns full-width at half-maximum (fwhm) timing jitter, single-ended readout has a CRT of 0.16 ns fwhm and double-ended readout has a CRT of 0.111 ns fwhm. For LaBr3 : Ce crystals 3 mm × 3 mm × 30 mm, a rise time of 0.2 ns, a decay time of 18 ns, and a total of 7600 photoelectrons the CRT numbers are 0.14 ns and 0.072 ns fwhm, respectively. For a hypothetical ultra-fast scintillator 3 mm × 3 mm × 30 mm, a decay time of 1 ns, and a total of 4000 photoelectrons, the CRT numbers are 0.070 and 0.020 ns fwhm, respectively. Over a range of examples, values for double-ended readout are about 10% larger than the statistical lower bound.

Ventilator triggering.

Allowing spontaneous respiration during mechanical ventilation requires that the ventilator system can interpret a trigger signal from the patient and then deliver a synchronous breath. The majority of current ventilators are triggered by preset changes in pressure or flow detected in the system as a patient is initiating a breath. However, other triggers such as chest wall motion, waveform alteration, and diaphragmatic electromyograms have also been utilized. The time between initiation of a breath by a patient and delivery of a breath by the ventilator is known as trigger delay. Most trigger delay is inherent in the mechanics of the patient-ventilator interaction. However, recent advances in technology have captured a neural signal from the diaphragm to trigger the ventilator to deliver a breath, reducing trigger delay. Understanding trigger delay is important as it may lead to increased work of breathing and patient-ventilator asynchrony. Types of asynchrony related to the triggering phase are ineffective triggering, double triggering, and autotriggering. The presence of asynchrony has been shown to have deleterious effects on patients, including duration of mechanical ventilation and increased length of hospital stay. Recognizing asynchrony and understanding how to manipulate the trigger variable will reduce adverse effects on patients.

Non-invasive neurally adjusted ventilatory assist in preterm infants: a randomised phase II crossover trial

ObjectiveTo compare non-invasive ventilation neurally adjusted ventilatory assist (NIV-NAVA) and non-invasive pressure support (NIV-PS) in preterm infants on patient–ventilator synchrony.DesignA randomised phase II crossover trial.SettingNeonatal intensive care units of two...

Second-order motion-compensated spin echo diffusion tensor imaging of the human heart.

Myocardial microstructure has been challenging to probe in vivo. Spin echo-based diffusion-weighted sequences allow for single-shot acquisitions but are highly sensitive to cardiac motion. In this study, the use of second-order motion-compensated diffusion encoding was compared with first-order motion-compensated diffusion-weighted imaging during systolic contraction of the heart. First- and second-order motion-compensated diffusion encoding gradients were incorporated into a triggered single-shot spin echo sequence. The effect of contractile motion on the apparent diffusion coefficients and tensor orientations was investigated in vivo from basal to apical level of the heart. Second-order motion compensation was found to increase the range of systolic trigger delays from 30%-55% to 15%-77% peak systole at the apex and from 25%-50% to 15%-79% peak systole at the base. Diffusion tensor analysis yielded more physiological transmural distributions when using second-order motion-compensated diffusion tensor imaging. Higher-order motion-compensated diffusion encoding decreases the sensitivity to cardiac motion, thereby enabling cardiac DTI over a wider range of time points during systolic contraction of the heart.

Study on the Collaborative Triggering of Multiple STRETCH Meat Grinder With ICCOS Modules

The energy density of the inductive energy storage systems is one order of magnitude higher than that of the capacitive ones. The slow transfer of energy through capacitive hybrid (STRETCH) meat grinder with inverse current commutation with semiconductor (ICCOS) devices put forward by Tsinghua University is a typical inductive pulsed-power supply for electromagnetic launch system, which has remarkable current amplification ability as a single module. However, one module cannot provide enough amplitude and width for the load current of the railgun launching. Therefore, the collaborative work of multiple inductive source modules is necessary for practical usage. In this paper, the designed inductive power supply system of about 1 MJ is composed of 40 STRETCH meat grinders with ICCOS modules. All the main switches are opened simultaneously to reduce the magnetic field coupling among the modules and make the current rising edge steep. The modules are divided into several groups. The triggering delays of the thyristors between every two adjacent groups are carefully designed. After the first triggers for all the modules, the energy stored in the capacitors can be further utilized with the second triggers. The numerical simulation results show that the appropriate collaborative triggering delay can increase the adjustability of the output current width and the second triggers can further increase the current width and the system efficiency. Therefore, the load current with flat shape, appropriate amplitude, and longer duration can be provided with modular design and collaborate triggering discharge of the multiple modules. This can provide a theoretical foundation for the future study and implementation.