Current status of virtual reality simulation education for orthopedic residents: the need for a change in focus.

Introduction: Advances in technology are changing surgical education. Simulation provides an important adjunct to operative experience. This pedagogy has arguably become more important in light of the COVID-19 pandemic, with resultant reduction in operative exposure for trainees. Virtual reality (VR) simulators may provide significant contribution to experiential learning; however, much of the investigative focus to date has, correctly, been on establishing validity evidence for these constructs. The aim of this work was to perform a scoping review to assess the current status of VR simulation education to determine curricular development efforts for orthopedic residents. Methods: With a trained medical librarian, searches of PubMed, EMBASE, and Web of Science were conducted for all articles in the last 10 years (September 2011-September 2021). Controlled vocabulary Medical Subject Headings (MeSH) terms and natural language developed with subject matter experts describing virtual reality or VR simulation and orthopedic training were used. Two trained reviewers evaluated all abstracts for inclusion. Exclusion criteria were all articles that did not assess VR simulation education involving orthopedic residents. Data were extracted from the included full-text articles including: study design, type of participants, type of VR simulation, simulated orthopedic skill, type of educational event, learner assessment including Kirkpatrick's level, assessment of quality using the Medical Education Research Study Quality Instrument (MERSQI), and level of effectiveness (LoE). Results: Initial search identified 1,394 articles, of which 61 were included in the final qualitative synthesis. The majority (54%) were published in 2019- 2021, 49% in Europe. The commonest VR simulator was ArthroS (23%) and the commonest simulated skill was knee arthroscopy (33%). The majority of studies (70%) focused on simulator validation. Twenty-three studies described an educational module or curriculum, and of the 21 (34%) educational modules, 43% were one-off events. Most modules (18/21, 86%) assessed learners at Kirkpatrick level 2. With regard to methodological quality, 44% of studies had MERSQI 11.5-15 and 89% of studies had LoE of 2. Two studies had LoE of 3. Conclusion: Current literature pertaining to VR training for orthopedic residents is focused on establishing validity and rarely forms part of a curriculum. Where the focus is education, the majority are discrete educational modules and do not teach a comprehensive amalgam of orthopedic skills. This suggests focus is needed to embed VR simulation training within formal curricula efforts guided by the work of Kern, and assess the efficacy of these against patient outcomes.

Fabrication and characterization of laser-heated, multiplexed electrospray emitter.

We present a one-step fabrication method for a new multiplexed electrospray emitter with nine parallel micronozzles. The nozzles were formed by wet chemical etching of the end of a microstructured silica fiber containing nine 10 µm flow channels. By carefully adjusting the water flow through the channels while etching, we controlled the shape of the conical micronozzles and were able to obtain conditions under which the micronozzles, together with the flow channels, formed optical micro-axicon lenses. When 1064 nm light was guided through the flow channels and focused by the micro-axicon lenses into the Taylor cones, we were able to increase the desolvation of a model analyte and thereby increased the spray current produced by the emitter. This work paves the way towards a rapidly modulated mass-spectrometry source having a greatly enhanced throughput.

Broadband Vibration Detection in Tissue Phantoms Using a Fiber Fabry-Perot Cavity.

OBJECTIVE: A fiber optic vibration sensor is developed and characterized with an ultrawide dynamic sensing range, from less than 1 Hz to clinical ultrasound frequencies near 6 MHz. The vibration sensor consists of a matched pair of fiber Bragg gratings coupled to a custom-built signal processing circuit. The wavelength of a laser diode is locked to one of the many cavity resonances using the Pound-Drever-Hall scheme. METHODS: A calibrated piezoelectric vibration element was used to characterize the sensor's strain, temperature, and noise responses. To demonstrate its sensing capability, an ultrasound phantom with built-in low frequency vibration actuation was constructed. RESULTS: The fiber optic senor was shown to simultaneously capture the low frequency vibration and the clinical ultrasound transmission waveforms with nanostrain sensitivity. CONCLUSION: This miniaturized and sensitive vibration sensor can provide comprehensive information regarding strain response and the resultant ultrasound waveforms.

Application of coupled mode theory and coherent superposition theory to phase-shift measurements on optical microresonators.

Several mathematical models exist in the literature to describe the properties of optical resonators. Here, coupled mode theory and coherent superposition theory are compared and their consistency is demonstrated as they are applied to phase-shift cavity ring-down measurements in optical (micro-)cavities. In the particular case of a whispering gallery mode in a microsphere cavity these models are applied to transmission measurements and backscattering measurements through the fiber taper that couples light into the microresonator. It is shown that both models produce identical relations when applied to these traveling wave cavities.

In-fiber Mach-Zehnder interferometer for gas refractive index measurements based on a hollow-core photonic crystal fiber.

We describe an in-fiber interferometer based on a gas-filled hollow-core photonic crystal fiber. Expressions for the sensitivity, figure of merit and refractive index resolution are derived, and values are experimentally measured and theoretically validated using mode field calculations. The refractive indices of nine monoatomic and molecular gases are measured with a resolution of δns < 10-6.

Quantitative diffusion and swelling kinetic measurements using large-angle interferometric refractometry.

The uptake and release of sorbates into films and coatings is typically accompanied by changes of the films' refractive index and thickness. We provide a comprehensive model to calculate the concentration of the sorbate from the average refractive index and the film thickness, and validate the model experimentally. The mass fraction of the analyte partitioned into a film is described quantitatively by the Lorentz-Lorenz equation and the Clausius-Mosotti equation. To validate the model, the uptake kinetics of water and other solvents into SU-8 films (d = 40-45 µm) were explored. Large-angle interferometric refractometry measurements can be used to characterize films that are between 15 µm to 150 µm thick and, Fourier analysis, is used to determine independently the thickness, the average refractive index and the refractive index at the film-substrate interface at one-second time intervals. From these values the mass fraction of water in SU-8 was calculated. The kinetics were best described by two independent uptake processes having different rates. Each process followed one-dimensional Fickian diffusion kinetics with diffusion coefficients for water into SU-8 photoresist film of 5.67 × 10(-9) cm(2) s(-1) and 61.2 × 10(-9) cm(2) s(-1).

Quantification of different water species in acetone using a NIR-triple-wavelength fiber laser.

A fiber laser using a thulium-doped ZBLAN gain medium was used to generate laser radiation simultaneously at 1461, 1505 and 1874 nm, with > 5 mW output power at each of the wavelengths. The laser was used to quantify the near-infrared absorption of liquid water in acetone. Additionally, near-infrared spectra were recorded using a broad band source and were interpreted using parallel factor (PARAFAC) analysis to rationalize the concentration-dependent peak shifts.

Absorption measurements in liquid core waveguides using cavity ring-down spectroscopy.

Short liquid core waveguides (LCWs) were included into a fiber-loop cavity ring-down absorption spectrometer to reduce the detection limit over, both, single pass absorption in a LCW and cavity-enhanced absorption using a conventional fiber-loop cavity. LCWs of 5 and 10 cm length were interfaced with a pressure-flow system and a multimode fiber-loop cavity using concave fiber lenses with matching numerical apertures and diameters. Two red dyes, Allura Red AC and Congo Red, were detected with a 532 nm pulsed laser at a 5 nM limit of detection in a detection volume of less than 1 µL, corresponding to a minimal detectable absorbance of less than 4 × 10(-4) cm(-1) and a minimal detectable change in absorption cross section, σ(min) = V(det) × Îµ × C(LOD), of about 14 µm(2) (Allura Red AC) and 37 µm(2) (Congo Red).

Monitoring of vapor uptake by refractive index and thickness measurements in thin films.

We report a method for real-time monitoring of vapor uptake by simultaneous detection of the refractive index, n, and thickness, d, of thin transparent films with a precision of δn=10(-4) and δd<100 nm. The setup combines total internal reflection (Abbé) refractometry with an interferometric imaging method. A fast Fourier transform and phase fitting method is applied for accurate and independent determination of refractive indices and thicknesses. While the uptake of acetone vapor by polydimethylsiloxane is investigated, the system is also suited for characterization of other solid and liquid films.

Fluorescence excitation-emission matrix (EEM) spectroscopy and cavity ring-down (CRD) absorption spectroscopy of oil-contaminated jet fuel using fiber-optic probes.

Excitation emission matrix (EEM) and cavity ring-down (CRD) spectral signatures have been used to detect and quantitatively assess contamination of jet fuels with aero-turbine lubricating oil. The EEM spectrometer has been fiber-coupled to permit in situ measurements of jet turbine oil contamination of jet fuel. Parallel Factor (PARAFAC) analysis as well as Principal Component Analysis and Regression (PCA/PCR) were used to quantify oil contamination in a range from the limit of detection (10 ppm) to 1000 ppm. Fiber-loop cavity ring-down spectroscopy using a pulsed 355 nm laser was used to quantify the oil contamination in the range of 400 ppm to 100,000 ppm. Both methods in combination therefore permit the detection of oil contamination with a linear dynamic range of about 10,000.

Musical instrument pickup based on a laser locked to an optical fiber resonator.

A low-noise transducer based on a fiber Fabry-Perot (FFP) cavity was used as a pickup for an acoustic guitar. A distributed feedback (DFB) laser was locked to a 25 MHz-wide resonance of the FFP cavity using the Pound-Drever-Hall method. The correction signal was used as the audio output and was preamplified and sampled at up to 96 kHz. The pickup system is largely immune against optical noise sources, exhibits a flat frequency response from the infrasound region to about 25 kHz, and has a distortion-free audio output range of about 50 dB.

Chemical sensing using fiber cavity ring-down spectroscopy.

Waveguide-based cavity ring-down spectroscopy (CRD) can be used for quantitative measurements of chemical concentrations in small amounts of liquid, in gases or in films. The change in ring-down time can be correlated to analyte concentration when using fiber optic sensing elements that change their attenuation in dependence of either sample absorption or refractive index. Two types of fiber cavities, i.e., fiber loops and fiber strands containing reflective elements, are distinguished. Both types of cavities were coupled to a variety of chemical sensor elements, which are discussed and compared.

Optical fiber sensing based on reflection laser spectroscopy.

An overview on high-resolution and fast interrogation of optical-fiber sensors relying on laser reflection spectroscopy is given. Fiber Bragg-gratings (FBGs) and FBG resonators built in fibers of different types are used for strain, temperature and acceleration measurements using heterodyne-detection and optical frequency-locking techniques. Silica fiber-ring cavities are used for chemical sensing based on evanescent-wave spectroscopy. Various arrangements for signal recovery and noise reduction, as an extension of most typical spectroscopic techniques, are illustrated and results on detection performances are presented.

Chemical sensor based on a long-period fibre grating modified by a functionalized polydimethylsiloxane coating.

A chemical sensor based on a coated long-period grating has been prepared and characterized. Designer coatings based on polydimethylsiloxane were prepared by the incorporation of diphenylsiloxane and titanium cross-linker in order to provide enhanced sensitivity for a variety of key environmental pollutants and optimal refractive index of the coating. Upon microextraction of the analyte into the polymer matrix, an increase in the refractive index of the coating resulted in a change in the attenuation spectrum of the long-period grating. The grating was interrogated using ring-down detection as a means to amplify the optical loss and to gain stability against misalignment and power fluctuations. Chemical differentiation of cyclohexane and xylene was achieved and a detection limit of 300 ppm of xylene vapour was realized.

Biochemical signal detection in miniaturized fluidic systems by integrated microresonator.

An optical sensor integrated into a polymer microfluidic chip is proposed as a low cost solution to highly parallel biochemical analysis. The sensor consists of a single high-finesse optical resonator for direct analytes detection. High quality silica microspheres (diameter approximately 300 microm) are easily produced and low-loss whispering gallery modes were excited through evanescent coupling at wavelengths near 1550 nm and 544 nm. The quality factor (Q) and ring down time of these modes is sensitive to minute changes in the microresonator environment thus making it an excellent candidate for a sensor. Instead of the traditional time domain studies, we determine quality factors and ring down times as long as 53.8 +/- 0.6 ns (Q approximately 10(6)) from phase shift measurements using optical sources with sinusoidal intensity modulations of 300 kHz and below.

What are the priorities in basic asthma research? A United Kingdom perspective.

The National Asthma Campaign (in the United Kingdom) has recently completed a strategic review of priorities for basic asthma research over the next 5 to 10 years. Leading asthma experts and representatives of the main funding agencies were involved in a nationwide consultation. Discussions were carried out in 7 thematic areas: Genetics of asthma, early-life events, environmental influences, immunology and immunotherapy, inflammation and anti-inflammation, airway remodeling, and the interface between academia and industry. Discussions were not restricted by considerations of financial affordability but were driven by vision and science. The consultation highlighted a number of generic issues pertaining to the organization of basic asthma research. Phenotypes of asthma require more robust characterization, particularly for genetic studies. Emphasis on longitudinal studies should be encouraged, and more information can still be gained from existing well-characterized asthma cohorts, though this requires some coordination. Human research is particularly strong and should continue, and the use of human tissue is vital to our understanding of the disease at the cellular and molecular levels. Animal models of asthma remain an important tool with which to dissect disease mechanisms, but they must be improved and refined. The consultation covered a wide range of issues and highlighted the need for collaboration at all levels between research groups and with industry and also between funding agencies. The recommendations made have relevance to everyone involved in basic asthma research. This article describes the recommendations and reviews the specific research issues relating to each of the 7 thematic areas.