Delayed care in myocardial infarction and ischemic stroke patients during the COVID-19 pandemic.

COVID-19 has profound direct health consequences, however secondary effects were much broader as rates of hospital visits steeply declined for non-COVID-19 concerns, including myocardial infarction (MI) and stroke, with patients choosing to wait longer before symptoms convince them to seek medical attention. Thus, patients where ischemia leads to tissue loss should be a major concern. METHODS: The months of March to June 2019 and 2020 were compared to each other at 4 Denver area hospitals. Reduction in overall ED visits and an increase in patient refusal for emergency transport were clear in the data collected. During this period in 2019, 49 MI and 90 stroke patients were admitted. In 2020 this was 40 and 90 respectively. All were matched for age and gender. For MI patients ejection fraction and door to EKG and intervention times were measured. For stroke patients last known well time, time to evaluation, and modified Rankin scores were measured. RESULTS: 254 (8.12%) patients refused emergency services transportation before the pandemic compared to 479 (18.35%) during the pandemic (p-value <0.001, chi square test). In the MI cohort, no significant difference was detected in measured ejection fraction (48% vs 49% p-value = 0.682). Additionally, no significant difference was detected between door to EKG time or door to MI intervention time. During the pandemic 8 (22%) expired with an MI prior to discharge, compared to 2 (4%) before the pandemic. The stroke cohort Door to Evaluation Time, Time since last well known, and modified Rankin scores were all found to have insignificant differences. DISCUSSION: ED volume was significantly lower during the early stages of the pandemic. During this time however only death from cardiac events increased, in spite of similar ejection fractions at discharge. The cause of this remains unclear as ejection fraction similarities make it less attributable to loss of tissue than to other factors. Patient behavior significantly changed during the pandemic, making this a likely source of the increase in mortality seen.

Robotically applied hemostatic clamping for care-under-fire: harnessing bomb robots for hemorrhage control.

BACKGROUND: Early hemorrhage control after interpersonal violence is the most urgent requirement to preserve life and is now recognized as a responsibility of law enforcement. Although earlier entry of first responders is advocated, many shooting scenes remain unsafe for humans, necessitating first responses conducted by robots. Thus, robotic hemorrhage control warrants study as a care-under-fire treatment option. METHODS: Two bomb disposal robots (Wolverine and Dragon Runner) were retrofitted with hemostatic wound clamps. The robots' ability to apply a wound clamp to a simulated extremity exsanguination while controlled by 4 experienced operators was tested. The operators were randomly assigned to perform 10 trials using 1 robot each. A third surveillance robot (Stair Climber) provided further visualization for the operators. We assessed the success rate of the application of the wound clamp to the simulated wound, the time to application of the wound clamp and the amount of fluid loss. We also assessed the operators' efforts to apply the wound clamp after an initial attempt was unsuccessful or after the wound clamp was dropped. RESULTS: Remote robotic application of a wound clamp was demonstrated to be feasible, with complete cessation of simulated bleeding in 60% of applications. This finding was consistent across all operators and both robots. There was no difference in the success rates with the 2 robots (p = 1.00). However, there were differences in fluid loss (p = 0.004) and application time (p < 0.001), with the larger (Wolverine) robot being faster and losing less fluid. CONCLUSION: Law enforcement tactical robots were consistently able to provide partial to complete hemorrhage control in a simulated extremity exsanguination. Consideration should be given to using this approach in care-under-fire and care-behind-the-barricade scenarios as well as further developing the technology and doctrine for robotic hemorrhage control.

A "human-proof pointy-end": a robotically applied hemostatic clamp for care-under-fire

Summary: Providing the earliest hemorrhage control is now recognized as a shared responsibility of all members of society, including both the lay public and professionals, consistent with the Stop the Bleed campaign. However, providing early hemorrhage control in a hostile environment, such as the scene of a mass shooting, is extremely challenging. In such settings, the first access to a bleeding victim may be robotic. An all-purpose bomb robot was thus retrofitted with a commercial, off-the-shelf wound clamp and successfully applied to an extremity exsanguination simulator as a demonstration of remote robotic hemorrhage control. As this method can potentially control extremity hemorrhage, further development of the techniques, equipment and, most importantly, the guidelines and rules of engagement should continue. We suggest that in order to minimize the loss of life during an active shooter incident, the armamentarium of prehospital medical resources may be extended to include law-enforcement robots.

Reliability of the Faces, Legs, Activity, Cry, and Consolability Scale in Assessing Acute Pain in the Pediatric Emergency Department.

OBJECTIVES: The Faces, Legs, Activity, Cry, and Consolability (FLACC) scale is one of the most widely utilized observational pain assessment scales in clinical practice. Although designed and validated to assess postoperative pain, the tool is currently applied to assess acute pain in multiple settings, including the emergency department. Scarce literature exists evaluating the reliability of the FLACC scale in the nonsurgical population and none in the emergency department. We sought to investigate the reliability of the FLACC scale in assessing acute pain in the pediatric emergency department and to examine the sensitivity of FLACC scores after the administration of analgesia. METHODS: In phase 1 of this prospective study, a series of 2 independent evaluators, blinded to each other's evaluations, scored 66 patients using the FLACC tool. Degree of concordance among the 6 dyads was used to measure interrater reliability. In phase 2, FLACC scores were obtained just before the administration of analgesia in 35 patients and measured at 30 and at 60 minutes after administration. RESULTS: Among the 6 dyads of evaluators, Kendall W demonstrated a strong concordance (27 of 30 measures; range, 0.63-1.00) for individual components of the scale and for the composite scores (range, 0.85-0.96). Significant mean reductions from preanalgesia FLACC scores [5.54; 95% confidence interval (CI), 4.79-6.30] were seen at 30 minutes (2.00; 95% CI, 1.61-2.39) and 60 minutes (1.14; 95% CI, 0.79-1.50) postanalgesia (P < 0.0001 for all comparisons). CONCLUSIONS: The FLACC scale demonstrated high interrater reliability for both individual FLACC items and total scores in a convenience sample of patients aged 6 months to 5 years in a pediatric emergency department. It seems to be an appropriate observational tool to assess acute pain in this population.

Intraoperative optical coherence tomography for assessing human lymph nodes for metastatic cancer.

BACKGROUND: Evaluation of lymph node (LN) status is an important factor for detecting metastasis and thereby staging breast cancer. Currently utilized clinical techniques involve the surgical disruption and resection of lymphatic structure, whether nodes or axillary contents, for histological examination. While reasonably effective at detection of macrometastasis, the majority of the resected lymph nodes are histologically negative. Improvements need to be made to better detect micrometastasis, minimize or eliminate lymphatic disruption complications, and provide immediate and accurate intraoperative feedback for in vivo cancer staging to better guide surgery. METHODS: We evaluated the use of optical coherence tomography (OCT), a high-resolution, real-time, label-free imaging modality for the intraoperative assessment of human LNs for metastatic disease in patients with breast cancer. We assessed the sensitivity and specificity of double-blinded trained readers who analyzed intraoperative OCT LN images for presence of metastatic disease, using co-registered post-operative histopathology as the gold standard. RESULTS: Our results suggest that intraoperative OCT examination of LNs is an appropriate real-time, label-free, non-destructive alternative to frozen-section analysis, potentially offering faster interpretation and results to empower superior intraoperative decision-making. CONCLUSIONS: Intraoperative OCT has strong potential to supplement current post-operative histopathology with real-time in situ assessment of LNs to preserve both non-cancerous nodes and their lymphatic vessels, and thus reduce the associated risks and complications from surgical disruption of lymphoid structures following biopsy.

Molecular specificity in photoacoustic microscopy by time-resolved transient absorption.

We have recently harnessed transient absorption, a resonant two-photon process, for ultrahigh resolution photoacoustic microscopy, achieving nearly an order of magnitude improvement in axial resolution. The axial resolution is optically constrained due to the two-photon process unlike traditional photoacoustic microscopy where the axial resolution is inversely proportional to the frequency bandwidth of the detector. As a resonant process, the arrival time of the two photons need not be instantaneous. Systematically recording the signal as a function of the delay between two pulses will result in the measurement of an exponential decay whose time constant is related to the molecular dynamics. This time constant, analogous to the fluorescence lifetime, but encompassing nonradiative decay as well, can be used to differentiate between molecular systems with overlapping absorption spectra. This is frequently the situation for closely related yet distinct molecules such as redox pairs. In order to enable the measure of the exponential decay, we have reconfigured our transient absorption ultrasonic microscopy (TAUM) system to incorporate two laser sources with precisely controlled pulse trains. The system was tested by measuring Rhodamine 6G, an efficient laser dye where the molecular dynamics are dominated by the fluorescence pathway. As expected, the measured exponential time constant or ground state recovery time, 3.3±0.7 ns, was similar to the well-known fluorescence lifetime, 4.11±0.05 ns. Oxy- and deoxy-hemoglobin are the quintessential pair whose relative concentration is related to the local blood oxygen saturation. We have measured the ground state recovery times of these two species in fully oxygenated and deoxygenated bovine whole blood to be 3.7±0.8 ns and 7.9±1.0 ns, respectively. Hence, even very closely related pairs of molecules may be differentiated with this technique.

The mechanics and behavior of cliff swallows during tandem flights.

Cliff swallows (Petrochelidon pyrrhonota) are highly maneuverable social birds that often forage and fly in large open spaces. Here we used multi-camera videography to measure the three-dimensional kinematics of their natural flight maneuvers in the field. Specifically, we collected data on tandem flights, defined as two birds maneuvering together. These data permit us to evaluate several hypotheses on the high-speed maneuvering flight performance of birds. We found that high-speed turns are roll-based, but that the magnitude of the centripetal force created in typical maneuvers varied only slightly with flight speed, typically reaching a peak of ~2 body weights. Turning maneuvers typically involved active flapping rather than gliding. In tandem flights the following bird copied the flight path and wingbeat frequency (~12.3 Hz) of the lead bird while maintaining position slightly above the leader. The lead bird turned in a direction away from the lateral position of the following bird 65% of the time on average. Tandem flights vary widely in instantaneous speed (1.0 to 15.6 m s(-1)) and duration (0.72 to 4.71 s), and no single tracking strategy appeared to explain the course taken by the following bird.

The length-force behavior and operating length range of squid muscle vary as a function of position in the mantle wall.

Hollow cylindrical muscular organs are widespread in animals and are effective in providing support for locomotion and movement, yet are subject to significant non-uniformities in circumferential muscle strain. During contraction of the mantle of squid, the circular muscle fibers along the inner (lumen) surface of the mantle experience circumferential strains 1.3 to 1.6 times greater than fibers along the outer surface of the mantle. This transmural gradient of strain may require the circular muscle fibers near the inner and outer surfaces of the mantle to operate in different regions of the length-tension curve during a given mantle contraction cycle. We tested the hypothesis that circular muscle contractile properties vary transmurally in the mantle of the Atlantic longfin squid, Doryteuthis pealeii. We found that both the length-twitch force and length-tetanic force relationships of the obliquely striated, central mitochondria-poor (CMP) circular muscle fibers varied with radial position in the mantle wall. CMP circular fibers near the inner surface of the mantle produced higher force relative to maximum isometric tetanic force, P0, at all points along the ascending limb of the length-tension curve than CMP circular fibers near the outer surface of the mantle. The mean ± s.d. maximum isometric tetanic stresses at L0 (the preparation length that produced the maximum isometric tetanic force) of 212 ± 105 and 290 ± 166 kN m(-2) for the fibers from the outer and inner surfaces of the mantle, respectively, did not differ significantly (P=0.29). The mean twitch:tetanus ratios for the outer and inner preparations, 0.60 ± 0.085 and 0.58 ± 0.10, respectively, did not differ significantly (P=0.67). The circular fibers did not exhibit length-dependent changes in contraction kinetics when given a twitch stimulus. As the stimulation frequency increased, L0 was approximately 1.06 times longer than LTW, the mean preparation length that yielded maximum isometric twitch force. Sonomicrometry experiments revealed that the CMP circular muscle fibers operated in vivo primarily along the ascending limb of the length-tension curve. The CMP fibers functioned routinely over muscle lengths at which force output ranged from only 85% to 40% of P0, and during escape jets from 100% to 30% of P0. Our work shows that the functional diversity of obliquely striated muscles is much greater than previously recognized.

Undulatory locomotion of flexible foils as biomimetic models for understanding fish propulsion.

An undulatory pattern of body bending in which waves pass along the body from head to tail is a major mechanism of creating thrust in many fish species during steady locomotion. Analyses of live fish swimming have provided the foundation of our current understanding of undulatory locomotion, but our inability to experimentally manipulate key variables such as body length, flexural stiffness and tailbeat frequency in freely swimming fish has limited our ability to investigate a number of important features of undulatory propulsion. In this paper we use a mechanical flapping apparatus to create an undulatory wave in swimming flexible foils driven with a heave motion at their leading edge, and compare this motion with body bending patterns of bluegill sunfish (Lepomis macrochirus) and clown knifefish (Notopterus chitala). We found similar swimming speeds, Reynolds and Strouhal numbers, and patterns of curvature and shape between these fish and foils, suggesting that flexible foils provide a useful model for understanding fish undulatory locomotion. We swam foils with different lengths, stiffnesses and heave frequencies while measuring forces, torques and hydrodynamics. From measured forces and torques we calculated thrust and power coefficients, work and cost of transport for each foil. We found that increasing frequency and stiffness produced faster swimming speeds and more thrust. Increasing length had minimal impact on swimming speed, but had a large impact on Strouhal number, thrust coefficient and cost of transport. Foils that were both stiff and long had the lowest cost of transport (in mJ m(-1) g(-1)) at low cycle frequencies, and the ability to reach the highest speed at high cycle frequencies.

Point-of-Care Ultrasound Use by EMS Providers in Out-of-Hospital Cardiac Arrest.

AIM: Paramedics received training in point-of-care ultrasound (POCUS) to assess for cardiac contractility during management of medical out-of-hospital cardiac arrest (OHCA). The primary outcome was the percentage of adequate POCUS video acquisition and accurate video interpretation during OHCA resuscitations. Secondary outcomes included POCUS impact on patient management and resuscitation protocol adherence. METHODS: A prospective, observational cohort study of paramedics was performed following a four-hour training session, which included a didactic lecture and hands-on POCUS instruction. The Prehospital Echocardiogram in Cardiac Arrest (PECA) protocol was developed and integrated into the resuscitation algorithm for medical non-shockable OHCA. The ultrasound (US) images were reviewed by a single POCUS expert investigator to determine the adequacy of the POCUS video acquisition and accuracy of the video interpretation. Change in patient management and resuscitation protocol adherence data, including end-tidal carbon dioxide (EtCO2) monitoring following advanced airway placement, adrenaline administration, and compression pauses under ten seconds, were queried from the prehospital electronic health record (EHR). RESULTS: Captured images were deemed adequate in 42/49 (85.7%) scans and paramedic interpretation of sonography was accurate in 43/49 (87.7%) scans. The POCUS results altered patient management in 14/49 (28.6%) cases. Paramedics adhered to EtCO2 monitoring in 36/36 (100.0%) patients with an advanced airway, adrenaline administration for 38/38 (100.0%) patients, and compression pauses under ten seconds for 36/38 (94.7%) patients. CONCLUSION: Paramedics were able to accurately obtain and interpret cardiac POCUS videos during medical OHCA while adhering to a resuscitation protocol. These findings suggest that POCUS can be effectively integrated into paramedic protocols for medical OHCA.

Quantitative imaging of cochlear soft tissues in wild-type and hearing-impaired transgenic mice by spectral domain optical coherence tomography.

Human hearing loss often occurs as a result of damage or malformations to the functional soft tissues within the cochlea, but these changes are not appreciable with current medical imaging modalities. We sought to determine whether optical coherence tomography (OCT) could assess the soft tissue structures relevant to hearing using mouse models. We imaged excised cochleae with an altered tectorial membrane and during normal development. The soft tissue structures and expected anatomical variations were visible using OCT, and quantitative measurements confirmed the ability to detect critical changes relevant to hearing.

Imaging high-frequency periodic motion in the mouse ear with coherently interleaved optical coherence tomography.

Vibratory measurements of the structures of the ear are key to understanding much of the pathology in mouse models of hearing loss. Unfortunately the high-speed sampling required to interrogate the high end of the mouse hearing spectrum is beyond the reach of most optical coherence tomography (OCT) systems. To address this issue, we have developed an algorithm that enables phase-sensitive OCT measurements over the full range of the mouse hearing spectrum (4-90 kHz). The algorithm phase-locks the line-trigger to the acoustic stimulation and then uses interleaved sampling to reconstruct the signal with higher temporal sampling. The algorithm was evaluated by measuring the vibratory response of mouse tympanic membrane to a pure tone stimulus.

In vivo dynamic characterization of the human tympanic membrane using pneumatic optical coherence tomography.

Decreased mobility of the human eardrum, the tympanic membrane (TM), is an essential indicator of a prevalent middle ear infection. The current diagnostic method to assess TM mobility is via pneumatic otoscopy, which provides subjective and qualitative information of subtle motion. In this study, a handheld spectral-domain pneumatic optical coherence tomography system was developed to simultaneously measure the displacement of the TM, air pressure inputs applied to a sealed ear canal, and to perform digital pneumatic otoscopy. A novel approach based on quantitative parameters is presented to characterize spatial and temporal variations of the dynamic TM motion. Furthermore, the TM motions of normal middle ears are compared with those of ears with middle ear infections. The capability of noninvasively measuring the rapid motion of the TM is beneficial to understand the complex dynamics of the human TM, and can ultimately lead to improved diagnosis and management of middle ear infections.

Randomized Controlled Trial of Point-of-Care Ultrasound Education for the Recognition of Tension Pneumothorax by Paramedics in Prehospital Simulation.

OBJECTIVE: The primary goal of this study was to determine if ultrasound (US) use after brief point-of-care ultrasound (POCUS) training on cardiac and lung exams would result in more paramedics correctly identifying a tension pneumothorax (TPTX) during a simulation scenario. METHODS: A randomized controlled, simulation-based trial of POCUS lung exam education investigating the ability of paramedics to correctly diagnose TPTX was performed. The US intervention group received a 30-minute cardiac and lung POCUS lecture followed by hands-on US training. The control group did not receive any POCUS training. Both groups participated in two scenarios: right unilateral TPTX and undifferentiated shock (no TPTX). In both scenarios, the patient continued to be hypoxemic after verified intubation with pulse oximetry of 86%-88% and hypotensive with a blood pressure of 70/50. Sirens were played at 65 decibels to mimic prehospital transport conditions. A simulation educator stated aloud the time diagnoses were made and procedures performed, which were recorded by the study investigator. Paramedics completed a pre-survey and post-survey. RESULTS: Thirty paramedics were randomized to the control group; 30 paramedics were randomized to the US intervention group. Most paramedics had not received prior US training, had not previously performed a POCUS exam, and were uncomfortable with POCUS. Point-of-care US use was significantly higher in the US intervention group for both simulation cases (P <.001). A higher percentage of paramedics in the US intervention group arrived at the correct diagnosis (77%) for the TPTX case as compared to the control group (57%), although this difference was not significantly different (P = 0.1). There was no difference in the correct diagnosis between the control and US intervention groups for the undifferentiated shock case. On the post-survey, more paramedics in the US intervention group were comfortable with POCUS for evaluation of the lung and comfortable decompressing TPTX using POCUS (P <.001). Paramedics reported POCUS was within their scope of practice. CONCLUSIONS: Despite being novice POCUS users, the paramedics were more likely to correctly diagnose TPTX during simulation after a brief POCUS educational intervention. However, this difference was not statistically significant. Paramedics were comfortable using POCUS and felt its use improved their TPTX diagnostic skills.

Fourier domain Pump-Probe Optical Coherence Tomography imaging of melanin.

We report the development of a two-color Fourier domain Pump-Probe Optical Coherence Tomography (PPOCT) system. Tissue phantom experiments to characterize the system performance demonstrated imaging depths in excess of 725 microm, nearly comparable to the base Optical Coherence Tomography system. PPOCT A-line rates were also demonstrated in excess of 1 kHz. The physical origin of the PPOCT signal was investigated with a series of experiments which revealed that the signal is a mixture of short and long lifetime component signals. The short lifetime component was attributed to transient absorption while the long lifetime component may be due to a mixture of transient absorption and thermal effects. Ex vivo images of porcine iris demonstrated the potential for imaging melanin in the eye, where cancer of the melanocytes is the most common form of eye cancer in adults.

The next nine minutes: Lessons learned from the large-scale active shooter training prior to the STEM school shooting.

OBJECTIVE: As the incidence of active shooters increase, local emergency response has also changed. South Metro Fire Rescue coordinated a series of hyper-realistic active shooter simulation drills involving multiple agencies. METHODS: "The Next Nine Minutes" was one of the largest active shooter drills performed to date with 904 personnel that were trained in 18 mass casualty active shooter drills. Evaluation was from point of injury to and including care in the operating room (OR), and evaluation of real-time system logistics. RESULTS: A total of 126 patients in Cut Suits® received a total of 479 procedures such as needle decompressions, cricothyrotomies, tourniquets, wound packs, and chest tubes. Central to this exercise, law enforcement (LE) established a warm zone from the initial shooting. EMS was able to move into the facility, locate casualties, extract the first victim, move them to a casualty collection point (CCP), and transport them to safety within 12 minutes. CONCLUSIONS: Strengths and weaknesses were identified in prehospital and in-hospital care. These included what roles agencies play in a true event, specific timing in establishing areas such as the warm zone and CCP, transportation, and logistics at the accepting hospitals. Only after the barriers to success were identified and addressed did the timing of casualty movement drastically improve. Lessons learned from this training were ultimately used to save lives at the STEM School, Highlands Ranch, and Colorado Shooting. This in situ immersion training should be practiced as a whole system.

Otitis Media Middle Ear Effusion Identification and Characterization Using an Optical Coherence Tomography Otoscope.

OBJECTIVE: To determine the feasibility of detecting and differentiating middle ear effusions (MEEs) using an optical coherence tomography (OCT) otoscope. STUDY DESIGN: Cross-sectional study. SETTING: US tertiary care children's hospital. SUBJECTS AND METHODS: Seventy pediatric patients undergoing tympanostomy tube placement were preoperatively imaged using an OCT otoscope. A blinded reader quiz was conducted using 24 readers from 4 groups of tiered medical expertise. The primary outcome assessed was reader ability to detect presence/absence of MEE. A secondary outcome assessed was reader ability to differentiate serous vs nonserous MEE. RESULTS: OCT image data sets were analyzed from 45 of 70 total subjects. Blinded reader analysis of an OCT data subset for detection of MEE resulted in 90.6% accuracy, 90.9% sensitivity, 90.2% specificity, and intra/interreader agreement of 92.9% and 87.1%, respectively. Differentiating MEE type, reader identification of nonserous MEE had 70.8% accuracy, 53.6% sensitivity, 80.1% specificity, and intra/interreader agreement of 82.9% and 75.1%, respectively. Multivariate analysis revealed that age was the strongest predictor of OCT quality. The mean age of subjects with quality OCT was 5.01 years (n = 45), compared to 2.54 years (n = 25) in the remaining subjects imaged (P = .0028). The ability to capture quality images improved over time, from 50% to 69.4% over the study period. CONCLUSION: OCT otoscopy shows promise for facilitating accurate MEE detection. The imageability with the prototype device was affected by age, with older children being easier to image, similar to current ear diagnostic technologies.

Magnetomotive Displacement of the Tympanic Membrane Using Magnetic Nanoparticles: Toward Enhancement of Sound Perception.

OBJECTIVE: A novel hearing-aid scheme using magnetomotive nanoparticles (MNPs) as transducers in the tympanic membrane (TM) is proposed, aiming to noninvasively and directly induce a modulated vibration on the TM. METHODS: In this feasibility study, iron oxide (Fe3O4) nanoparticles were applied on ex vivo rat TM tissues and allowed to diffuse over ∼2 h. Subsequently, magnetic force was exerted on the MNP-laden TM via a programmable electromagnetic solenoid to induce the magnetomotion. Optical coherence tomography (OCT), along with its phase-sensitive measurement capabilities, was utilized to visualize and quantify the nanometer-scale vibrations generated on the TM tissues. RESULTS: The magnetomotive displacements induced on the TM were significantly greater than the baseline vibration of the TM without MNPs. In addition to a pure frequency tone, a chirped excitation and the corresponding spectroscopic response were also successfully generated and obtained. Finally, visualization of volumetric TM dynamics was achieved. CONCLUSION: This study demonstrates the effectiveness of magnetically inducing vibrations on TMs containing iron oxide nanoparticles, manipulating the amplitude and the frequency of the induced TM motions, and the capability of assessing the magnetomotive dynamics via OCT. SIGNIFICANCE: The results demonstrated here suggest the potential use of this noninvasive magnetomotive approach in future hearing aid applications. OCT can be utilized to investigate the magnetomotive dynamics of the TM, which may either enhance sound perception or magnetically induce the perception of sound without the need for acoustic speech signals.

Ratiometric analysis of optical coherence tomography-measured in†vivo retinal layer thicknesses for the detection of early diabetic retinopathy.

Influence of diabetes mellitus (DM) and diabetic retinopathy (DR) on parafoveal retinal thicknesses and their ratios was evaluated. Six retinal layer boundaries were segmented from spectral-domain optical coherence tomography images using open-source software. Five study groups: (1) healthy control (HC) subjects, and subjects with (2) controlled DM, (3) uncontrolled DM, (4) controlled DR and (5) uncontrolled DR, were identified. The one-way analyses of variance (ANOVA) between adjacent study groups (i. e. 1 with 2, 2 with 3, etc) indicated differences in retinal thicknesses and ratios. Overall retinal thickness, ganglion cell layer (GCL) thickness, inner plexiform layer (IPL) thickness, and their combination (GCL+ IPL), appeared to be significantly less in the uncontrolled DM group when compared to controlled DM and controlled DR groups. Although the combination of nerve fiber layer (NFL) and GCL, and IPL thicknesses were not different, their ratio, (NFL+GCL)/IPL, was found to be significantly higher in the controlled DM group compared to the HC group. Comparisons of the controlled DR group with the controlled DM group, and with the uncontrolled DR group, do not show any differences in the layer thicknesses, though several significant ratios were obtained. Ratiometric analysis may provide more sensitive parameters for detecting changes in DR. Picture: A representative segmented OCT image of the human retina is shown.

Low-cost hand-held probe for depth-resolved low-coherence interferometry.

We report on the development of a low-cost hand-held low-coherence interferometric imaging system based on the principle of linear optical coherence tomography (Linear OCT), a technique which was first proposed in the early 2000s as a simpler alternative to the conventional time-domain and Fourier-domain OCT. A bench-top implementation of the proposed technique is first presented and validated. The axial resolution, SNR, and sensitivity roll-of of the system was estimated to be 5.2 µm and 80 dB, and 3.7 dB over a depth of 0.15 mm, respectively. After validating the bench-top system, two hand-held probe implementations for contact-based imaging and in vivo human tympanic membrane imaging are presented. The performance of the proposed system was compared with a research-grade state-of-the-art Fourier-domain low coherence interferometry (LCI) system by imaging several biological and non-biological samples. The results of this study suggest that the proposed system might be a suitable choice for applications where imaging depth and SNR can be traded for lower cost and simpler optical design.