Gerald Hefferman

• Doctor of Medicine
• Clinical Fellow at Harvard Medical School

Background and aim: In recent years, there has been an increased interest in recording high-quality electromyographic signals from within the sockets of lower-limb amputees. However, successful recording presents major challenges to both researchers and clinicians. This article details and compares four prototypical integrated socket-sensor designs...

This paper reports the experimental demonstration of a coiled coaxial cable resonator capable of meeting the critical coupling condition using a reduced number of coils relative to previously reported coiled resonators. By introducing a second slot along the length of the device, a two-slot coiled coaxial cable resonator was fabricated and critical...

This article details the generation of an extended-bandwidth frequency sweep using a single, communication grade distributed feedback (DFB) laser. The frequency sweep is generated using a two-step technique. In the first step, injection current modulation is employed as a means of varying the output frequency of a DFB laser over a bandwidth of 99.2...

Purpose. The purpose of this study was to evaluate various objective, quantitative, time-resolved fluoroscopic imaging parameters for use in the peri-interventional evaluation of stenotic peripheral arterial disease lesions. Material and Methods. Ten patients (median age, 64; age range, 52 to 79; 8 males, 2 females) with high-grade stenoses of eith...

Purpose: The goal of this study was to determine whether the benefits of multiphase CTA (mCTA) over single-phase CTA (sCTA) for the detection of proximal cerebrovascular occlusions similarly extend to the distal cerebral vasculature. Methods: Four attending radiologists, two neuroradiologists and two emergency radiologists, contributed as readers...

Purpose : Hip osteoarthritis (HOA) is known to have a multifactorial pathogenesis. Recent studies suggest that spinopelvic alignment may represent an important additional pathogenic abnormality resulting in HOA. This study aims to assess the correlation between spinopelvic parameters (pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS) and l...

Purpose To evaluate the safety and efficacy of rotational thrombectomy (RT) in a large single-center real-world cohort for total vascular occlusions of the lower extremity. Materials and Methods The clinical records and images of all patients between 2010 and 2020 treated via RT (Rotarex, BD) were assessed. Patient demographics, clinical data, proc...

The aim was to evaluate the accuracy of a prototypical artificial intelligence-based algorithm for automated segmentation and diameter measurement of the thoracic aorta (TA) using CT. One hundred twenty-two patients who underwent dual-source CT were retrospectively included. Ninety-three of these patients had been administered intravenous iodinated...

This paper describes an integrated, accurate, and inexpensive semiconductor laser -based optical frequency domain reflectometry (OFDR) system design. The system utilizes the fiber under test for both sensing and frequency sweep linearization functions, allowing the system to mitigate and compensate for phase errors without the need for an auxiliary...

Objective This study aims to investigate the correlation between spinopelvic parameters in supine position (pelvic incidence (PI), sacral slope (SS), pelvic tilt (PT), lumbar lordosis (LL)), disc degeneration and herniation of the thoracolumbar spine, as well as cardiovascular risk factors and back pain in a southern German cohort from the general...

Time-domain reflectometry (TDR) is an established means of measuring impedance inhomogeneity of a variety of waveguides, providing critical data necessary to characterize and optimize the performance of high-bandwidth computational and communication systems. However, TDR systems with both the high spatial resolution (sub-cm) and voltage resolution...

Background Little is known about the associations between cardiovascular risk factors (CRF) and disc degeneration (DD). Purpose To evaluate the potential association between CRFs and intervertebral DD in a population-based sample. Methods A total of 400 participants from the community-based KORA-study were assessed in terms of CRFs, specifically...

Time-domain reflectometry (TDR) is an established means of measuring impedance inhomogeneity of a variety of waveguides, providing critical data necessary to characterize and optimize the performance of high-bandwidth computational and communication systems. However, TDR systems with both the high spatial resolution (sub-cm) and voltage resolution...

Background: Combination therapy using hepatic resection (HR) and intra-operative thermal ablation is a treatment approach for patients with technically unresectable liver malignancies. The aim of this study was to investigate safety, survival and local recurrence rates for patients with technically unresectable liver tumors undergoing HR and separ...

As the security of optical fiber lines in data centers has attracted growing attention, it has become increasingly important to accurately characterize the fiber that is used. Optical frequency domain reflectometry (OFDR) has been demonstrated as a means of identifying specific segments of optical fiber; however, OFDR measurements are limited in le...

This paper describes a flexible, compact, semiconductor laser (SCL)-based optical frequency-domain reflectometry (OFDR) design, incorporating swept-laser linearization functions (both passive and active), in-situ phase error evaluation function, and phase error compensation function. At the core of the proposed design, a fiber-optic Mach-Zehnder in...

This paper reports a reconfigurable architecture to generate and maintain the linearity of frequency-swept semiconductor lasers for both current rising (up-sweep) and falling (down-sweep) edges, respectively. This method combines both passive and active controls to achieve a high frequency-sweep linearity using an integrated digital architecture. B...

PURPOSE The aim of this investigation was to quantitatively evaluate the effects of the addition of peak and delayed venous phase imaging to arterial phase CTA for the detection of distal ischemic strokes. Changes in sensitivity, specificity, time required to render a final decision, and subjective level of diagnostic confidence were quantified. M...

This paper introduces an integrated fiber physical unclonable function (PUF) verification system based on a semiconductor laser source at substantially lower complexity and cost than existing alternatives. A source sub-section consisting of a linear frequency-swept semiconductor laser is used in combination with an optical frequency domain reflecto...

Objective The objective of this study was to evaluate the potential benefit of a dedicated cone-beam-CT streak metal artifact removal technique (SMART) in terms of both image quality and diagnostic confidence in patients undergoing bronchial artery embolization. Methods A total of 17 patients were included in this retrospective study. The SMART al...

The present disclosure provides a novel distributed coaxial cable strain sensor that can measure a strain profile over the entire length of a cable. Individual strain sensing elements are constructed using Fabry-Perot interferometers, coaxial cable Bragg gratings, or other reflectometry-based sensing structures. By assembling three or more strain s...

Objective: To investigate the outcome and safety data of chemosaturation with percutaneous hepatic perfusion (CS-PHP) of melphalan in patients with liver-dominant metastatic uveal melanoma. Material and methods: This is a HIPAA compliant, IRB approved, retrospective study. A total of 28 CS-PHPs were performed in 16 individual patients (six men and...

This letter reports a digitally integrated, self-trained pre-distortion curve finder for linearly frequency-swept semiconductor lasers. In this method, we introduce an iteration machine to train the laser current curves by utilizing the feedback signals from the laser's output. By measuring the phase and frequency information of lasers, we find tha...

The present disclosure provides methods and apparatus to improve the dynamic coherent length of a sweep velocity-locked laser pulse generator (SV-LLPG) in an all-electronic fashion. A digital SV-LLPG is disclosed with two operation modes, i.e., unidirectional and bidirectional sweep modes; self-adaptive and time-dependent loop parameters (gain and...

Optical frequency-domain reflectometry and frequency-modulated continuous wave (FMCW)-based sensing technologies, such as LiDAR and distributed fiber sensors, fundamentally rely on the performance of frequency-swept laser sources. Specifically, frequency-sweep linearity, which determines the level of measurement distortion, is of paramount importan...

Purpose The purpose of this study is to detail the current state of the websites of each of the currently established emergency radiology fellowship programs within the USA, in terms of publicly available information. The goal of the project is to present data for emergency radiology fellowship programs to tailor that information to attract those m...

Distributed optical fiber sensors are an increasingly utilized method of gathering distributed strain and temperature data. However, the large amount of data they generate presents a challenge that limits their use in real-time, in situ applications. This article describes a parallel and pipelined computing architecture that accelerates the signal-...

The present disclosure provides a novel fiber optic sensing device using ultra-weak, terahertz-range reflector structures. A fiber optic sensor device for distributed measurements (strain/temperature) includes an optical fiber detection arm having an inner core extending along a length of the optical fiber, an outer cladding surrounding the inner c...

Distributed optical fiber sensors are increasingly utilized method of distributed strain and temperature sensing, and the swept laser source plays an significant role in these applications. However, there is dynamic frequency-noise as the laser sweeping. In this paper, we proposed and experimentally demonstrated a real-time in-situ phase noise dete...

Primary pancreatic lymphoma (PPL) is of very rare occurrence as an extra nodal site of Non-Hodgkin’s lymphoma (NHL). It represents less than 1% of NHL. Out of which Burkitt lymphoma of pancreas is of a rare presentation. It usually occurs in children and presenting in adults is uncommon. The prevalence of pancreatic Burkitt lymphoma is not known as...

The present disclosure provides a sweep velocity-locked laser pulse generator (SV-LLPG) controlled using a digital phase locked loop (DPLL) circuit. The SV-LLPG is utilized for the interrogation of sub-terahertz-range fiber structures for sensing applications that require real-time data collection with mm-level spatial resolution. A laser generates...

This letter reports an all-digital sweep velocity-controlled pulse laser with enhanced sweep bandwidth. A vertical cavity surface emitting laser (VCSEL) was employed as the optical source. An all-digital phase locked loop (ADPLL) was designed and implemented using a field programmable logic array (FPGA) chip to lock the laser sweep velocity within...

A field-programmable gate array (FPGA)-controlled sweep velocity-locked laser pulse generator (SV-LLPG) design based on an all-digital phase-locked loop (ADPLL) is proposed. A distributed feedback laser with modulated injection current was used as a swept-frequency laser source. An open-loop predistortion modulation waveform was calibrated using a...

This Letter reports a sweep velocity-locked laser pulse generator controlled using a digital phase-locked loop (DPLL) circuit. This design is used for the interrogation of sub-terahertz-range fiber structures for sensing applications that require real-time data collection with millimeter-level spatial resolution. A distributed feedback laser was em...

Data intensive analysis is the major challenge in smart cities because of the ubiquitous deployment of various kinds of sensors. The natural characteristic of geo-distribution requires a new computing paradigm to offer location-awareness and latency-sensitive monitoring and intelligent control. Fog Computing, which extends the computing to the edge...

This letter reports an all-electronic, low bandwidth swept frequency laser used to interrogate terahertz-range fiber Bragg gratings (THz FBGs) for distributed strain sensing applications. A distributed feedback (DFB) laser with current injection modulation was employed as the swept frequency laser source. Using the resulting narrow bandwidth (~110...

This paper describes a series of terahertz-range weak reflection fiber optic structures engineered for distributed temperature and strain sensing applications. Four specific structures are described: an intrinsic Fabry-Perot interferometer, a terahertz-range fiber Bragg grating, a phase-shifted terahertz-range fiber Bragg grating, and a terahertz-r...

This paper presents a rapid signal processing approach for OCMI system, which could significantly reduce the complexity of computations while maintaining decent performances. A direct phase demodulator can be pre-calibrated and applied to extract the absolute phase change to target reflectors at different locations, where the strain change can be f...

We report a two-axis fiber inclinometer fabricated using an ultraweak terahertz-range fiber Bragg grating. Three sensing grating structures were inscribed along a single-mode optical fiber using a femtosecond laser, bound together into a sensing array using thermoformed plastic, and fixed to a two-axis rotational stage. Inclination tests were perfo...

This letter reports a fiber Bragg grating (FBG) for distributed sensing applications fabricated using single-mode optical fiber and a femtosecond laser and interrogated in the terahertz (THz) range. A theoretical model of device behavior was derived, which agreed well with experimentally observed device behavior. In order to investigate the utility...

Recent advances in optical fiber sensing techniques have demonstrated the utility of terahertz (THz) gratings as a modality for strain and temperature sensing. However, these techniques remain reliant on the use of higher-order resonant peaks, enhancing their sensitivity at the cost of limited dynamic range. The use of a lower-order resonant peak f...

This letter reports a multiplexed optical displacement sensor using a thin core fiber (TCF) exciter. The TCF exciter is followed by a stripped single mode optical fiber. A small section of buffer is used as the movable component along the single mode fiber. Ultra-weak cladding mode reflection (< − 75 dB) was employed to probe the refractive index d...

This Letter reports on an ultraweak intrinsic Fabry–Perot interferometer (IFPI) array fabricated by a femtosecond (fs) laser for distributed sensing applications. Ultralow reflectors ( ) were obtained. IFPIs with different physical lengths showed identical temperature sensitivity ( ). A distributed temperature sensing test was conducted. No crossta...

This paper describes a new physical unclonable function for identification, FiberID, which uses the molecular level Rayleigh backscatter pattern within a small section of telecommunication-grade optical fiber as a means of verification and identification. The verification process via FiberID is experimentally studied, and an equal error rate (EER)...