Universal Pulse Research Articles

Comparison of commercial smart watch and universal pulse oximeter on heart rate, oxygen saturation, and distance covered using the 6-minute walk test: A cross-sectional study

Comparison of commercial smart watch and universal pulse oximeter on heart rate, oxygen saturation, and distance covered using the 6-minute walk test: A cross-sectional study

Universal and waveform-resolving dual pulse reconstruction through interferometric strong-field ionization

Universal and waveform-resolving dual pulse reconstruction through interferometric strong-field ionization

Distribution and reference values of peripheral perfusion index in neonates from population-wide screening

BackgroundPeripheral perfusion index (PPI) is useful in a variety of neonatal settings. Currently, available reference values are from small numbers and highly variable.MethodsWe sought to generate reference values of PPI...

Universal modes: Calibration-free time-interleaved acquisition of modes.

To introduce universal modes by applying the universal pulse concept to time-interleaved acquisition of modes (TIAMO), thereby achieving calibration-free inhomogeneity mitigation for body imaging at ultra-high fields. Two databases of different RF arrays were used to demonstrate the feasibility of universal modes. The first comprised 31 cardiac in vivo data sets acquired at 7T while the second consisted of 6 simulated 10.5T pelvic data sets. Subject-specific solutions and universal modes were computed and subsequently evaluated alongside predefined default modes. For the cardiac database, subdivision into subpopulations was investigated. The optimization was performed using least-squares (LS) TIAMO and acquisition modes optimized for refocused echoes (AMORE). Finally, universal modes based on simulated pelvis data were applied in vivo at 10.5T. In all studied cases, the universal modes yield improvements over the predefined default modes of up to 51% (cardiac) and 30% (pelvic) in terms of median excitation error when using two modes. The subpopulation-specific cardiac solutions revealed a further improvement of universal modes at the expense of increased errors when applied outside the appropriate subpopulation. Direct application of simulation-based universal modes in vivo resulted in up to a 14% reduction in excitation error compared to default modes and up to a 34% reduction in peak 10 g local specific absorption rate (SAR) compared to subject-specific solutions. Universal modes are feasible for calibration-free inhomogeneity mitigation at ultra-high fields. In addition, simulation-based solutions can be applied directly in vivo, eliminating the need for large in vivo databases.

What can we gain from subpopulation universal pulses? A simulation-based study.

The aim of the study was to explore a novel methodology for designing universal pulses (UPs) that balances the benefits of a calibration-free approach with subject-specific online pulse design. The proposed method involves segmenting the population into subpopulations with variability in anatomical shapes and positions reduced to 75%, 50%, and 25% of their original values while keeping the mean values unchanged. An additional 25% extreme case with a large volume of interest and shifted position was included. For each group, a 5kT-points universal inversion pulse was designed and assessed by the normalized root mean square error (NRMSE) on the target longitudinal magnetization profile. The performance was compared to the conventional one-size-fits-all approach. A total of 132 electromagnetic simulations were executed to generate representative anatomies and specific absorption rate (SAR) distributions in a three-dimensional parameter space comprised of head breadth, head length, and Y-shift. The 99.9th percentile on the peak local SAR distribution was utilized to establish an intersubject variability safety margin. UPs designed for subpopulations with decreased head shape and position variability reduced the anatomical safety margin by up to 20%. Furthermore, when a head was significantly different to the average case, the proposed approach improved the inversion homogeneity by up to 24%, compared to the conventional one-size-fits-all approach. Subpopulation UPs present an opportunity to improve the homogeneity and reduce anatomical SAR safety margins at 7T without additional acquisition time for calibration.

State of Newborn Care in Armed Forces Hospitals

Organized perinatal and newborn care in armed forces hospitals includes preconception and antenatal care, care during labor and childbirth, immediate newborn care, care of small and sick newborn including screening for hypoglycemia, care of healthy newborns in the first week including newborn screening for thyroid disorders, Glucose 6 phosphate dehydrogenase deficiency, universal hearing screening, and universal pulse oximetry. Neonatal mortality was 24.3% in less than 26 weeks (n = 37), 32.6% in neonates born between 26 weeks to 27+6 weeks (n = 95), 6.2% in neonates born between 28 weeks and 31+6 weeks (n = 242), 0.8% in 32 weeks to 36+6 weeks (n = 1890), and 0.1% in term neonates (n = 21,292). The comprehensive health care model in armed forces can be a model for other institutes and health systems for more effective neonatal health care.

Meta-analysis and open-source database for in vivo brain Magnetic Resonance spectroscopy in health and disease

Proton (1H) Magnetic Resonance Spectroscopy (MRS) is a non-invasive tool capable of quantifying brain metabolite concentrations in vivo. Prioritization of standardization and accessibility in the field has led to the development of universal pulse sequences, methodological consensus recommendations, and the development of open-source analysis software packages. One on-going challenge is methodological validation with ground-truth data. As ground-truths are rarely available for in vivo measurements, data simulations have become an important tool. The diverse literature of metabolite measurements has made it challenging to define ranges to be used within simulations. Especially for the development of deep learning and machine learning algorithms, simulations must be able to produce accurate spectra capturing all the nuances of in vivo data. Therefore, we sought to determine the physiological ranges and relaxation rates of brain metabolites which can be used both in data simulations and as reference estimates. Using the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines, we've identified relevant MRS research articles and created an open-source database containing methods, results, and other article information as a resource. Using this database, expectation values and ranges for metabolite concentrations and T2 relaxation times are established based upon a meta-analyses of healthy and diseased brains.

ARBITRARY DURATION PULSE SHAPER

This paper considers the possibility of constructing a universal pulse generator based on TTL (transistor-transistor logic) elements, which provides pulses of a given duration at the time of entry to the input of the negative edge of the input start pulse (difference from logical unit to logical zero). The duration of the generated output pulse can be set by the capacitance of one capacitor and does not depend on the duration of the input pulse. A significant advantage of the proposed pulse shaper is the high steepness of both the positive front (difference from logical zero to logical unit) and the negative edge of the generated output pulse (difference from logical unit to logical zero), which depends only on the operation time of logical elements and not depends on the duration of both input (start) and output pulses. This advantage is based on the action of positive feedback at the time of formation of both positive and negative fronts of the output pulse. In this case, the feedback circuits in the formation of positive and negative fronts of the output pulse are different, which does not allow the circuit to switch to self-excitation mode (autogeneration). The advantages of the proposed pulse shaper (high steepness of the fronts with little complication of the circuit compared to the known capacitor pulse shapers) are determined by using the internal structure of the logic elements of the TTL series. This paper also considers the possibility of reducing the capacitance of the capacitor by several tens of times, which determines the duration of long output pulses, due to the introduction of an emitter repeater. The main disadvantage of the proposed pulse shaper is the low temperature and time stability of the duration of the formed output pulse, which is characteristic of all capacitor pulse shapers.

OTUP workflow: target specific optimization of the transmit k-space trajectory for flexible universal parallel transmit RF pulse design.

To optimize transmit k-space trajectories for a wide range of excitation targets and to design "universal pTx RF pulses" based on these trajectories. Transmit k-space trajectories (stack of spirals and SPINS) were optimized to best match different excitation targets using the parameters of the analytical equations of spirals and SPINS. The performances of RF pulses designed based on optimized and non-optimized trajectories were compared. The optimized trajectories were utilized for universal pulse design. The universal pulse performances were compared with subject specific tailored pulse performances. The OTUP workflow (optimization of transmit k-space trajectories and universal pulse calculation) was tested on three test target excitation patterns. For one target (local excitation of a central area in the human brain) the pulses were tested in vivo at 9.4 T. The workflow produced appropriate transmit k-space trajectories for each test target. Utilization of an optimized trajectory was crucial for the pulse performance. Using unsuited trajectories diminished the performance. It was possible to create target specific universal pulses. However, not every test target is equally well suited for universal pulse design. There was no significant difference in the in vivo performance between subject specific tailored pulses and a universal pulse at 9.4 T. The proposed workflow further exploited and improved the universal pulse concept by combining it with gradient trajectory optimization for stack of spirals and SPINS. It emphasized the importance of a well suited trajectory for pTx RF pulse design. Universal and tailored pulses performed with a sufficient degree of similarity in simulations and a high degree of similarity in vivo. The implemented OTUP workflow and the B0 /B1+ map data from 18 subjects measured at 9.4 T are available as open source (https://github.com/ole1965/workflow_OTUP.git).

Coarctation of the aorta: Prenatal assessment, postnatal management and neonatal outcomes

Coarctation of the aorta (Coa) is a potentially life threatening diagnosis. It occurs in 0.3 per 1000 live births and accounts for 6-8% of all infants with congenital heart defects. Neonates with severe Coa may be completely asymptomatic at birth, as the ductus arteriosus can provide flow to the lower body. Those who are not diagnosed prenatally may be diagnosed only after constriction of the ductus arteriosus, when they present in cardiogenic shock. This group has a higher risk for mortality and morbidity relative to those diagnosed prenatally. Despite the increasing practice of universal pulse oximetry screening, many cases with significant coarctation of the aorta still go undiagnosed in the newborn period. In this article, we present the pathophysiology, diagnosis, presentation, treatment and outcomes of Coa.

Respiration induced changes and their impact on universal and tailored 3D kT-point parallel transmission pulses for 7T cardiac imaging.

Human heart imaging at ultra-high fields is highly challenging because of respiratory motion-induced artefacts and spatially heterogeneous profiles. This work demonstrates that respiration resolved 3D -maps can be used with a dedicated tailored and universal parallel transmission (pTx) pulse design to compensate respiration related changes in subjects performing shallow and deep breathing (SB/DB). Three-dimensional (3D) -maps of the thorax were acquired in 31 subjects under SB and in 15 subjects under SB and DB. Different universal and tailored non-selective pTx pulses were designed from non-respiration resolved (NRR) and respiration resolved (RR) reconstructions of the SB/DB -maps. The performance of all pulses was tested with RR-SB/DB -maps. Respiration-robust tailored and universal pulses were applied in vivo in 5 subjects at 7T in 3D gradient-echo free-breathing scans. All optimized pTx pulses performed well for SB. For DB, however, only the universal and the tailored respiration-robust pulses achieved homogeneous flip angles (FAs) in all subjects and across all respiration states, whereas the tailored respiration-specific pulses resulted in a higher FA variation. The respiration-robust universal pulse resulted in an average coefficient of variation in the FA maps of 12.6% compared to 8.2% achieved by tailored respiration-robust pulses. In vivo measurements at 7T demonstrate the benefits of using respiration-robust pulses for DB. Universal and tailored respiration-robust pTx pulses based on RR -maps are highly preferred to achieve 3D heart FA homogenization at 7T when subjects perform DB, whereas universal and tailored pulses based on NRR -maps are sufficient when subjects perform SB.

Standardized universal pulse: A fast RF calibration approach to improve flip angle accuracy in parallel transmission.

In parallel transmission (pTX), subject-tailored RF pulses allow achieving excellent flip angle (FA) accuracy but often require computationally extensive online optimizations, precise characterization of the static field ( ), and the transmit RF field ( ) distributions. This costs time and requires expertise from the MR user. Universal pulses (UPs) have been proposed to reduce this burden, yet, with a penalty in FA accuracy. This study introduces the concept of standardized universal pulses (SUPs), where pulses are designed offline and adjusted to the subject through a fast online calibration scan. A SUP is designed offline using a so-called standardized database, wherein each map has been normalized to a reference transmit RF field distribution. When scanning a new subject, a 3-slice acquisition (scan time s) is performed and used to adjust the SUP to the subject through a linear transform. SUP performance was assessed at 7T with simulations by computing the FA-normalized root mean square error (FA-NRMSE) and the FA pattern stability as measured by the average and coefficient of variation of the FA across 15 control subjects, along with in vivo experiments using an MP2RAGE sequence implementing the SUP variant for the FLASH readout. Adjusted SUP improved the FA-NRMSE (8.8 for UP vs. 7.1 for adjusted SUP). Experimentally in vivo, this translated in an improved signal homogeneity and more accurate quantification using MP2RAGE. The proposed SUP approach improves excitation accuracy (FA-NRMSE) while preserving the same offline pulse design principle as offered by UPs.

Standardized Universal Pulse: a fast RF calibration approach to improve flip angle accuracy in parallel transmission

Standardized Universal Pulse: a fast RF calibration approach to improve flip angle accuracy in parallel transmission

Reflections on Pulse Oximetry Screening for CCHD.

The idea of using pulse oximetry to screen for critical congenital heart disease (CCHD) began >20 years ago.1 The concept, which is simple in principle, took a laborious path from curious possibility to national standard.Much of the delay in implementing this screening process related to anxiety about the impact of false-positive tests and the burden on the health care system. Thankfully, since the broader acceptance of this screening approach, much of the anxiety has been allayed through our increased understanding of the logistics of pulse oximetry screening.In this issue of Pediatrics, Schwartz et al describe their experience at a large community hospital over 8 years.2 It should be noted that this hospital and this clinical team were instrumental in moving the pulse oximetry screening model forward. It is exciting to see this longer-term experience.The results described by Schwartz et al are largely reassuring. The positive predictive value for screening was 39% for CCHD. Over an 8-year period, only 31 out of almost 65 000 newborns failed the pulse oximetry screening. When the concept of universal pulse oximetry screening was first proposed, there were concerns that a high proportion of newborns would require detailed and expensive cardiology screening with echocardiography and, potentially, additional consultation. But, as Schwartz and others have shown, this turns out not to be the case. Most centers have been able to implement the pulse oximetry screening in an efficient manner incorporated into the routine care of newborns. Although there is admittedly substantial amount of work to screen 65 000 newborns only to uncover 12 children with critical congenital heart disease, such early detection can certainly be lifesaving. The yield is higher than many other newborn screens that have been endorsed by national organizations.3At this point, the pulse oximetry screening paradigm has largely been embraced. There had been some hope that, over time, prenatal detection might continue to increase such that the need for pulse oximetry screening would be unnecessary. However, the trends in prenatal diagnosis improvement seem to have plateaued. Therefore, for the foreseeable future, pulse oximetry–based CCHD screening in the newborns will continue to have an important role.Several investigators have shown that pulse oximetry screening for CCHD is cost-effective and lifesaving.4 The work by Schwartz et al has helped catalyze this national effort to advance pulse oximetry screening. This new critical appraisal of their experience over 8 years helps to provide context and further refinement to the pulse oximetry screening model. Their work, and that of others, has suggested refinements to this screening paradigm to minimize work but still achieve a high yield but low false-negative rate.5 Schwartz et al and the other pioneers in this arena deserve to be congratulated. Children with CCHD are alive today and thriving because of pulse oximetry–based screening. We can celebrate a successful paradigm of public health, clinician, and most importantly, patient and family collaboration to reduce unnecessary deaths from missed CCHD.

Calibration-free pTx of the human heart at 7T via 3D universal pulses.

MRI at ultra-high fields in the human body is highly challenging and requires lengthy calibration times to compensate for spatially heterogeneous profiles. This study investigates the feasibility of using pre-computed universal pulses for calibration-free homogeneous 3D flip angle distribution in the human heart at 7T. Twenty-two channel-wise 3D data sets were acquired under free-breathing in 19 subjects to generate a library for an offline universal pulse (UP) design (group 1: 12 males [M] and 7 females [F], 21-66 years, 19.8-28.3 kg/m2 ). Three of these subjects (2M/1F, 21-33 years, 20.8-23.6 kg/m2 ) were re-scanned on different days. A 4kT-points UP optimized for the 22 channel-wise 3D data sets in group 1 (UP22-4kT) is proposed and applied at 7T in 9 new and unseen subjects (group 2: 4M/5F, 25-56 years, 19.5-35.3 kg/m2 ). Multiple tailored and universal static and dynamic parallel-transmit (pTx) pulses were designed and evaluated for different permutations of the data sets in group 1 and 2. The proposed UP22-4kT provides low variation in all subjects, seen and unseen, without severe signal drops. Experimental data at 7T acquired with UP22-4kT shows comparable image quality as data acquired with tailored-4kT pulses and demonstrates successful calibration-free pTx of the human heart. UP22-4kT allows for calibration-free homogeneous flip angle distributions across the human heart at 7T. Large inter-subject variations because of sex, age, and body mass index are well tolerated. The proposed universal pulse removes the need for lengthy (10-15 min) calibration scans and therefore has the potential to bring body imaging at 7T closer to the clinical application.

A Nested Eight-Channel Transmit Array With Open-Face Concept for Human Brain Imaging at 7 Tesla

Purpose: Parallel transmit technology for MRI at 7 tesla will significantly benefit from high performance transmit arrays that offer high transmit efficiency and low mutual coupling between the individual array elements. A novel dual-mode transmit array with nested array elements has been developed to support imaging the human brain in both the single-channel (sTx) and parallel-transmit (pTx) excitation modes of a 7 tesla MRI scanner. In this work, the design, implementation, validation, specific absorption rate (SAR) management, and performance of the head coil is presented.Methods: The transmit array consisted of a nested arrangement to improve decoupling between the second-neighboring elements. Two large cut-outs were introduced in the RF shield for an open-face design to reduce claustrophobia and to allow patient monitoring. A hardware interface allows the coil to be used in both the sTx and pTx modes. SAR monitoring is done with virtual observation points (VOP) derived from human body models. The transmit efficiency and coverage is compared with the commercial single-channel and parallel-transmit head coils.Results: Decoupling inductors between the second-neighboring coil elements reduced the coupling to less than −20 dB. Local SAR estimates from the electromagnetic (EM) simulations were always less than the EM-based VOPs, which in turn were always less than scanner predictions and measurements for static and dynamic pTx waveforms. In sTx mode, we demonstrate improved coverage of the brain compared to the commercial sTx coil. The transmit efficiency is within 10% of the commercial pTx coil despite the two large cut-outs in the RF shield. In pTx mode, improved signal homogeneity was shown when the Universal Pulse was used for acquisition in vivo.Conclusion: A novel head coil which includes a nested eight-channel transmit array has been presented. The large cut-outs improve patient monitoring and reduce claustrophobia. For pTx mode, the EM simulation and VOP-based SAR management provided greater flexibility to apply pTx methods without the limitations of SAR constraints. For scanning in vivo, the coil was shown to provide an improved coverage in sTx mode compared to a standard commercial head coil.

Local excitation universal parallel transmit pulses at 9.4T.

To demonstrate that the concept of "universal pTx pulses" is applicable to local excitation applications. A database of B0 / maps from eight different subjects was acquired at 9.4T. Based on these maps, universal pulses that aim at local excitation of the visual cortex area in the human brain (with a flip angle of 90° or 7°) were calculated. The remaining brain regions should not experience any excitation. The pulses were designed with an extension of the "spatial domain method." A 2D and a 3D target excitation pattern were tested, respectively. The pulse performance was examined on non-database subjects by Bloch simulations and in vivo at 9.4T using a GRE anatomical MRI and a presaturated TurboFLASH mapping sequence. The calculated universal pulses show excellent performance in simulations and in vivo on subjects that were not contained in the design database. The visual cortex region is excited, while the desired non-excitation areas produce the only minimal signal. In simulations, the pulses with 3D target pattern show a lack of excitation uniformity in the visual cortex region; however, in vivo, this inhomogeneity can be deemed acceptable. A reduced field of view application of the universal pulse design concept was performed successfully. The proposed design approach creates universal local excitation pulses for a flip angle of 7° and 90°, respectively. Providing universal pTx pulses for local excitation applications prospectively abandons the need for time-consuming subject-specific B0 / mapping and pTx-pulse calculation during the scan session.

Pulse Oximetry Screening and Critical Congenital Heart Disease in the State of Oregon.

Late diagnosis of critical congenital heart disease (CCHD) is associated with higher levels of morbidity and mortality in neonates. Nearly all states have passed laws mandating universal pulse oximetry screening (POxS) of newborns to improve early detection rates of CCHD. We performed a retrospective chart review of all transthoracic echocardiograms (TTEs) interpreted by our institution on patients between 0 and 30 days of life in the years 2010 (prior to POxS) and 2015 (after POxS). Between 2010 and 2015, the number of neonatal TTEs interpreted by our institution decreased by 18.2%. In 2015, there were 46 neonates diagnosed with CCHD with a 78% prenatal detection rate. There was only one case of a true-positive POxS. Our study demonstrated that the initiation of POxS coincided with a significant decrease in neonatal TTEs, suggesting universal POxS may impart reassurance to primary providers leading to a decrease in TTE utilization.

Pulp Vitality Testing with a Developed Universal Pulse Oximeter Probe Holder.

Background and Objectives An accurate determination of the pulp status is relevant for a proper endodontic diagnosis. Objectives: The aim was to develop a universal pulse oximeter probe holder for measuring the oxygen saturation and to evaluate the use of pulse oximetry as a test for pulp vitality, by comparing the levels of oxygen saturation in the index finger and in the healthy dental pulp. Materials and Methods The universal holder was designed with software and printed with a 3D printer. The study was carried out on 128 healthy teeth. They were divided into eight groups according to tooth type. Ten root canal treated teeth served as a negative control group. For each patient, a pulse oximeter was first applied on the tooth followed by the index finger. The significance level (α) was set at 0.05. Results: The developed and manufactured universal pulse oximeter probe holder was suitable to measure the pulp vitality of all types of teeth. The handle allowed for holding the pulse oximeter on the tooth in parallel, firmly and securely. Significantly higher oxygen saturation was observed in the index finger (97.22%) compared to the dental pulp (93.17%) (p < 0.001). No correlation was observed between the maxillary teeth and index finger oxygen saturation values (r = 0.05, p = 0.72), whereas, between the mandibular teeth and index finger, a positive correlation was detected (r = 0.29, p = 0.02). There were no significant differences in the pulp oxygen saturation values between different teeth groups. Conclusion: The newly developed universal pulse oximeter probe holder is an effective device for pulp vitality testing.

Pulse oximetry screening for detection of congenital heart defects at 1646 m in Albuquerque, New Mexico.

To determine the false-positive rate of pulse oximetry screening at moderate altitude, presumed to be elevated compared with sea level values and assess change in false-positive rate with time. We retrospectively analysed 3548 infants in the newborn nursery in Albuquerque, New Mexico, (elevation 5400 ft) from July 2012 to October 2013. Universal pulse oximetry screening guidelines were employed after 24 hours of life but before discharge. Newborn babies between 36 and 36 6/7 weeks of gestation, weighing >2 kg and babies >37 weeks weighing >1.7 kg were included in the study. Log-binomial regression was used to assess change in the probability of false positives over time. Of the 3548 patients analysed, there was one true positive with a posteriorly-malaligned ventricular septal defect and an interrupted aortic arch. Of the 93 false positives, the mean pre- and post-ductal saturations were lower, 92 and 90%, respectively. The false-positive rate before April 2013 was 3.5% and after April 2013, decreased to 1.5%. There was a significant decrease in false-positive rate (p = 0.003, slope coefficient = -0.082, standard error of coefficient = 0.023) with the relative risk of a false positive decreasing at 0.92 (95% CI 0.88-0.97) per month. This is the first study in Albuquerque, New Mexico, reporting a high false-positive rate of 1.5% at moderate altitude at the end of the study in comparison to the false-positive rate of 0.035% at sea level. Implementation of the nationally recommended universal pulse oximetry screening was associated with a high false-positive rate in the initial period, thought to be from the combination of both learning curve and altitude. After the initial decline, it remained steadily elevated above sea level, indicating the dominant effect of moderate altitude.