An Adaptive SCG-ECG Multimodal Gating Framework for Cardiac CTA.

Cardiovascular disease (CVD) is the leading cause of death worldwide. Coronary artery disease (CAD), a prevalent form of CVD, is typically assessed using catheter coronary angiography (CCA), an invasive, costly procedure with associated risks. While cardiac computed tomography angiography (CTA) presents a less invasive alternative, it suffers from limited temporal resolution, often resulting in motion artifacts that degrade diagnostic quality. Traditional ECG-based gating methods for CTA inadequately capture cardiac mechanical motion. To address this, we propose a novel multimodal approach that enhances CTA imaging by predicting cardiac quiescent periods using seismocardiogram (SCG) and ECG data, integrated through a weighted fusion (WF) approach and artificial neural networks (ANNs). We developed a regression-based ANN framework (r-ANN WF) designed to improve prediction accuracy and reduce computational complexity, which was compared with a classification-based framework (c-ANN WF), ECG gating, and US data. Our results demonstrate that the r-ANN WF approach improved overall diastolic and systolic cardiac quiescence prediction accuracy by 52.6% compared to ECG-based predictions, using ultrasound (US) as the ground truth, with an average prediction time of 4.83 ms. Comparative evaluations based on reconstructed CTA images show that both r-ANN WF and c-ANN WF offer diagnostic quality comparable to US-based gating, underscoring their clinical potential. Additionally, the lower computational complexity of r-ANN WF makes it suitable for real-time applications. This approach could enhance CTA's diagnostic quality, offering a more accurate and efficient method for CVD diagnosis and management.

Mentor training for junior faculty: a brief evaluation report from the Georgia Clinical and Translational Science Alliance.

To provide a foundation for mentoring, junior faculty participated in a mentor training workshop informed by the Mentoring Clinical and Translational Researchers curriculum. The goal was to develop skills and behaviors that engender more rewarding and inclusive mentoring practices. Attendees responded to baseline and follow-up surveys assessing perceived mentoring skills. Follow-up surveys included closed- and open-ended questions about the value and satisfaction of the training, and intended behavior changes. Junior faculty respondents (n = 39) reported significantly higher overall mentoring skills after the training (t = -2.6, p = 0.012) with a medium effect size (Cohen's D = 0.59). Domains with statistically significant improvement from baseline to follow-up included aligning mentor-mentee expectations and assessing understanding. Thirty-eighty (97%) found the training valuable, and 32 (82%) indicated they would change mentoring-related behaviors because of the training. Intended behavior changes described in open-ended responses aligned with mentoring skills assessed (e.g., aligning expectations). An additional competency domain of evaluating mentoring relationships was also described. A mentor training workshop for junior faculty appeared to contribute to changes in mentoring skills and intended behaviors. Mentor training has the potential to enhance mentorship, which is critical to strengthening a diverse pipeline of clinical and translational science researchers.

Development and Characterization of a Micromagnetic Alternative to Cochlear Implant Electrode Arrays.

To stimulate the auditory nerve, cochlear implants directly inject electrical current into surrounding tissue via an implanted electrode array. While many cochlear implant users achieve strong speech perception scores, there remains significant variability. Since cochlear implant electrode arrays are surrounded by a conductive fluid, perilymph, a spread of excitation occurs. The functionality of the cochlea is spatially dependent, and a wider area of excitation negatively affects the hearing of the user. Importantly, magnetic fields are unaffected by the material properties of biological components. To utilize the electromagnetic properties of the human ear, a microcoil array was developed. The microcoils are 4-turn solenoids with a 250- [Formula: see text] turn radius and a 31.75- [Formula: see text] wire radius, coated with Parylene-C. The efficient design was implemented to accelerate testing. The obtained results describe stimulation capabilities. Functionality was validated using a frequency response analyzer to measure how the generated electromagnetic power radiates in space. 99.8% power loss was observed over a 100- [Formula: see text] separation between a pair of identical microcoils. Obtained through finite-element modeling, the microcoils can be driven by a 60 mA, 5 kHz, sinusoidal input for 10 minutes before predicted inflammation. Rattay's activating function was calculated to evaluate the magnetic stimulation effect of external fields on target neurons. Combined with the frequency response analysis, magnitude and spatial effects of the generated potential is established. As a result, each microcoil requires a 400- [Formula: see text]-wide area for each independent stimulation channel, which is 84% narrower than a commercial cochlear array channel, thereby suggesting greater spatial selectivity.

Combining Optical Character Recognition With Paper ECG Digitization.

OBJECTIVE: We propose a MATLAB-based tool to convert electrocardiography (ECG) waveforms from paper-based ECG records into digitized ECG signals that is vendor-agnostic. The tool is packaged as an open source standalone graphical user interface (GUI) based application. METHODS AND PROCEDURES: To reach this objective we: (1) preprocess the ECG records, which includes skew correction, background grid removal and linear filtering; (2) segment ECG signals using Connected Components Analysis (CCA); (3) implement Optical Character Recognition (OCR) for removal of overlapping ECG lead characters and for interfacing of patients' demographic information with their research records or their electronic medical record (EMR). The ECG digitization results are validated through a reader study where clinically salient features, such as intervals of QRST complex, between the paper ECG records and the digitized ECG records are compared. RESULTS: Comparison of clinically important features between the paper-based ECG records and the digitized ECG signals, reveals intra- and inter-observer correlations of 0.86-0.99 and 0.79-0.94, respectively. The kappa statistic was found to average at 0.86 and 0.72 for intra- and inter-observer correlations, respectively. CONCLUSION: The clinically salient features of the ECG waveforms such as the intervals of QRST complex, are preserved during the digitization procedure. Clinical and Healthcare Impact: This open-source digitization tool can be used as a research resource to digitize paper ECG records thereby enabling development of new prediction algorithms to risk stratify individuals with cardiovascular disease, and/or allow for development of ECG-based cardiovascular diagnoses relying upon automated digital algorithms.

High-density cochlear implants with position sensing and control.

Silicon-based thin-film technology has been used to develop high-density cochlear electrode arrays with up to 32 sites and four parallel channels of simultaneous stimulation. The lithographically-defined arrays utilize a silicon-dielectric-metal-parylene structure with 180 microm-diameter IrO sites on 250 microm centers. Eight on-board strain gauges allow real-time imaging of array shape during insertion, and a tip sensor measures forces on any structures contacted in the scala tympani (e.g., the basilar membrane). The array can be pre-stressed to hug the modiolus, which provides position reference. Tip position can be resolved to better than 50 microm. Circuitry mounted on the base of the array generates stimulating currents, records intra-cochlear responses and position information, and interfaces with a custom microcontroller and inductively-coupled wireless interface over an eight-lead ribbon cable. The circuitry delivers biphasic 500 microA current pulses with 4 microA resolution and a minimum pulse width of 4 micros. Multiple sites can be driven in parallel to provide higher current levels. Backing structures and articulated insertion tools are being developed for dynamic closed-loop insertion control.

Seismocardiography-Based Cardiac Computed Tomography Gating Using Patient-Specific Template Identification and Detection.

To more accurately trigger cardiac computed tomography angiography (CTA) than electrocardiography (ECG) alone, a sub-system is proposed as an intermediate step toward fusing ECG with seismocardiography (SCG). Accurate prediction of quiescent phases is crucial to prospectively gating CTA, which is susceptible to cardiac motion and, thus, can affect the diagnostic quality of images. The key innovation of this sub-system is that it identifies the SCG waveform corresponding to heart sounds and determines their phases within the cardiac cycles. Furthermore, this relationship is modeled as a linear function with respect to heart rate. For this paper, B-mode echocardiography is used as the gold standard for identifying the quiescent phases. We analyzed synchronous ECG, SCG, and echocardiography data acquired from seven healthy subjects (mean age: 31; age range: 22-48; males: 4) and 11 cardiac patients (mean age: 56; age range: 31-78; males: 6). On average, the proposed algorithm was able to successfully identify 79% of the SCG waveforms in systole and 68% in diastole. The simulated results show that SCG-based prediction produced less average phase error than that of ECG. It was found that the accuracy of ECG-based gating is more susceptible to increases in heart rate variability, while SCG-based gating is susceptible to high cycle to cycle variability in morphology. This pilot work of prediction using SCG waveforms enriches the framework of a comprehensive system with multiple modalities that could potentially, in real time, improve the image quality of CTA.

A Low-Power ASIC Signal Processor for a Vestibular Prosthesis.

A low-power ASIC signal processor for a vestibular prosthesis (VP) is reported. Fabricated with TI 0.35 µm CMOS technology and designed to interface with implanted inertial sensors, the digitally assisted analog signal processor operates extensively in the CMOS subthreshold region. During its operation the ASIC encodes head motion signals captured by the inertial sensors as electrical pulses ultimately targeted for in-vivo stimulation of vestibular nerve fibers. To achieve this, the ASIC implements a coordinate system transformation to correct for misalignment between natural sensors and implanted inertial sensors. It also mimics the frequency response characteristics and frequency encoding mappings of angular and linear head motions observed at the peripheral sense organs, semicircular canals and otolith. Overall the design occupies an area of 6.22 mm (2) and consumes 1.24 mW when supplied with ± 1.6 V.

A low-power, time-division-multiplexed vector matrix-multiplier for a vestibular prosthesis.

A custom analog vector matrix multiplier (VMM) for a vestibular prosthesis is reported. The VMM functions to reduce misalignment between implanted angular rate sensors and associated peripheral sense organs and precompensate for spurious electrical stimulation of vestibular neurons. Operating in the CMOS subthreshold region, the VMM performs a 3-by-3 vector matrix multiplication of rate sensor outputs, magnitude <; ±250 mV, and bandwidth <; 1.25 kHz. To reduce susceptibility to device mismatches, time-division-multiplexed multiplication is employed requiring 727 µs for a complete operation cycle. Fabricated with TSMC 0.35 µm CMOS technology, the footprint is 1523 µm × 1548 µm and consumes 5.37 µW of power.

Silicone-coated thin film array cochlear implantation in a feline model.

OBJECTIVES: Some limitations of cochlear implants can be attributed to a restricted spectral representation of sound provided by contemporary electrode arrays. Microfabricated high-density thin film array (TFA) technology enables a greater density of stimulating sites and, thus, a more complete spectral representation. Previous pilot cadaveric studies have documented insertion characteristics, although not electrical characteristics. STUDY DESIGN: Electrode evoked auditory brainstem response (ABR) testing in a feline model. METHODS: Six healthy, normal hearing cats were unilaterally deafened and implanted with a silicone coated TFA, measuring 27.8 × 0.4 × 80µm (L × W × H). Monopolar stimulation of single electrodes was used to evoke a triple peaked ABR. Thresholds to evoke a minimal ABR were determined. RESULTS: All 6 cats underwent successful full insertion and activation. Thresholds to evoke minimal ABR's varied among implants ranging from 75 to 450 µA. Over the basal portion of the array, thresholds were either larger or unable to evoke an ABR. CONCLUSION: Two-thirds of the implants showed ABR's along the entire array, whereas the others evoked ABR's at the apical end and less robustly more basally. This may reflect increased distance of the electrodes from the modiolus, as the basal half of the array is narrower relative to the width of the scala. A tapered design to ensure array distance to modiolus is minimized may enable the basal half of the arrays to stimulate more consistently.

A system for seismocardiography-based identification of quiescent heart phases: implications for cardiac imaging.

Seismocardiography (SCG), a representation of mechanical heart motion, may more accurately determine periods of cardiac quiescence within a cardiac cycle than the electrically derived electrocardiogram (EKG) and, thus, may have implications for gating in cardiac computed tomography. We designed and implemented a system to synchronously acquire echocardiography, EKG, and SCG data. The device was used to study the variability between EKG and SCG and characterize the relationship between the mechanical and electrical activity of the heart. For each cardiac cycle, the feature of the SCG indicating Aortic Valve Closure was identified and its time position with respect to the EKG was observed. This position was found to vary for different heart rates and between two human subjects. A color map showing the magnitude of the SCG acceleration and computed velocity was derived, allowing for direct visualization of quiescent phases of the cardiac cycle with respect to heart rate.

Current steering and current focusing with a high-density intracochlear electrode array.

Creating high-resolution or high-density, intra-cochlear electrode arrays may significantly improve quality of hearing for cochlear implant recipients. Through focused activation of neural populations such arrays may better exploit the cochlea's frequency-to-place mapping, thereby improving sound perception. Contemporary electrode arrays approach high-density stimulation by employing multi-polar stimulation techniques such as current steering and current focusing. In our procedure we compared an advanced high-density array with contemporary arrays employing these strategies. We examined focused stimulation of auditory neurons using an activating function and a neural firing probability model that together enable a first-order estimation of an auditory nerve fiber's response to electrical stimulation. The results revealed that simple monopolar stimulation with a high-density array is more localized than current steering with a contemporary array and requires 25-30% less current. Current focusing with high-density electrodes is more localized than current focusing with a contemporary array; however, a greater amount of current is required. This work illustrates that advanced high-density electrode arrays may provide a low-power, high-resolution alternative to current steering with contemporary cochlear arrays.

Low-power sensing for vestibular prostheses.

This paper describes a novel sensing approach for reducing power requirements of implantable vestibular prostheses. A passive, microfabricated polymeric inertial sensor for detecting angular head rotations based on the biomechanics of the human semicircular canal is described. Angular head motion is coded by deflection of a highly compliant capacitor plate placed in parallel with a rigid reference electrode. This capacitance change serves to detect instantaneous angular velocity along a given axis of rotation. Designed for integration with a microelectromechanical systems-based fully implantable vestibular prosthesis, this sensing method can provide substantial power savings when compared with contemporary gyroscopes.

Cochlear implantation using thin-film array electrodes.

OBJECTIVE: Current limitations in language perception may stem from an inability to provide high-resolution sound input. Thin-film array technology allows for a greater density of stimulating sites within the limited diameter of the scala tympani. This study examines the use of a flexible carrier to achieve adequate depth of insertion. STUDY DESIGN: A prospective human cadaveric temporal bone insertion analysis. SETTING: Academic otolaryngology department and school of electrical and computer engineering collaboration. METHODS: A prototype thin-film array electrode coupled with an insertion test device (ITD) was manufactured and inserted into 10 human cadaveric temporal bones. As controls, 2 additional temporal bones were implanted with the ITD only and 2 were unimplanted. Radiologic and histologic data were collected. RESULTS: Ten thin-film array electrodes were successfully implanted into 10 individual temporal bones via round window (5) and cochleostomy (5) approaches. Seventeen millimeters of insertion was noted for each device, with an average angular insertion depth of 292° by radiographic measurements and 392° by histologic sectioning. Electrode distance to the modiolus averaged 0.88 mm by computed tomography and 0.67 mm by histologic measurements. Average percentage trauma was 26% for the ITD-backed arrays compared with 15% and 29% for ITD only and unimplanted temporal bones, respectively. CONCLUSION: Thin-film array electrodes coupled with an ITD were successfully inserted into the human cochlea with limited trauma. With continued development and testing of this electrode design, the thin-film array may improve the language perception achieved through cochlear implantation.

A Prototype Head-Motion Monitoring System for In-Home Vestibular Rehabilitation Therapy.

This work reports the use of a head-motion monitoring system to record patient head movements while completing in-home exercises for vestibular rehabilitation therapy. Based upon a dual-axis gyroscope (yaw and pitch, ± 500-degrees/sec maximum), angular head rotations were measured and stored via an on-board memory card. The system enabled the clinician to document exercises at home. Several measurements were recorded in one patient with unilateral vestibular hypofunction: The total time of exercise for the week (118 minutes) was documented and compared with expected weekly exercise time (140 minutes). For gaze stabilization exercises, execution time of 60 sec was expected, and observed times ranged from 75-100 sec. An absence of rest periods between each exercise instead of the recommended one minute rest period was observed. Maximum yaw head velocities from approximately 100-350 degrees/sec were detected. A second subject provided feedback concerning the ease of use of the HAMMS device. This pilot study demonstrates, for the first time, the capability to capture the head-motion "signature" of a patient while completing vestibular rehabilitation exercises in the home and to extract exercise regime parameters and monitor patient adherence. This emerging technology has the potential to greatly improve rehabilitation outcomes for individuals completing in-home gaze stabilization exercises.

A trimodal system for the acquisition of synchronous echocardiography, electrocardiography, and seismocardiography data.

A novel system was developed to acquire synchronous echocardiography, electrocardiography (EKG), and seismocardiography (SCG) data. The system was developed to facilitate the study of the relationship between the mechanical and electrical characteristics of the heart. The system has both a hardware and software component. The hardware component consists of an application-specific device designed and built to acquire both SCG and EKG signals simultaneously. The software component consists of a package developed to record and synchronize data from both the device and a clinical ultrasound machine. A feasibility test was performed by simultaneous acquisition of a synchronous dataset from a human subject.