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Selected Topics in Quantum Electronics, IEEE Journal of

Issue 4 • Date July-Aug. 1999

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Displaying Results 1 - 25 of 43
  • In memoriam - Robert T. Wangemann

    Page(s): 891 - 892
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    Freely Available from IEEE
  • Introduction to the issue on lasers in medicine and biology

    Page(s): 893 - 894
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    Freely Available from IEEE
  • Clinical optical tomography and NIR spectroscopy for breast cancer detection

    Page(s): 1143 - 1158
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    The results of the first set of clinical trials with the Philips optical mammography prototype system are summarized. This optical mammo prototype is designed to image the interior of the female breast with the help of near-infrared (NIR) laser light transmission measurements. This study is expected to lead to optical tomography systems for breast cancer detection. This paper presents information on the design of the optical mammo system, the clinical measurements and the imaging results from an initial group of ten patients, and discussions about ongoing research on optical tomography. View full abstract»

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  • Laser-induced acoustic stresses under submerged biological membranes

    Page(s): 1027 - 1031
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    Er:YAG lasers are being widely studied as candidates for surgical procedures in liquid environments, such as in ophthalmology. However, while the Er:YAG laser can be a precise and efficient light scalpel, this surgical method includes accompanying stress waves that must be quantified and evaluated for potential harm. In this study, Er:YAG laser-induced stress waves for free running laser pulses were measured over various consecutive treatment periods. Using a spot-poled PVDF hydrophone, measurements were acquired beneath a biological membrane submerged in a saline bath. Results yielded pressures peaks of 300-600 mbar beneath the uncut membrane, which could be harmful for the optic nerve if located directly below the treatment area. Acoustic waves representative of direct laser-liquid interactions were observed immediately following membrane rupture, and yielded much larger pressures. The morphological changes in the acoustic wave can be used as a feedback signal to indicate when the membrane has been cut View full abstract»

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  • Corneal refractive surgery with femtosecond lasers

    Page(s): 902 - 910
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    We investigated the use of ultrashort pulsed (femtosecond) laser technology in corneal refractive surgery. When compared to longer pulsewidth nanosecond or picosecond laser pulses, femtosecond laser-tissue interactions are characterized by significantly smaller and more deterministic photodisruptive energy thresholds, as well as reduced shock waves and smaller cavitation bubbles. We utilized a highly reliable all-solid-state femtosecond laser system for all studies to demonstrate practicality in real-world operating conditions. Contiguous tissue effects were achieved by scanning a 5-μm focused laser spot below the corneal surface at pulse energies of approximately 2-4 μJ. A variety of scanning patterns was used to perform three prototype procedures in animal eyes; corneal flap cutting, keratomileusis, and intrastromal vision correction. Superior dissection and surface quality results were obtained for lamellar procedures (corneal flap cutting and keratornileusis). Preliminary in vivo studies of intrastromal vision correction suggest that consistent refractive changes can also be achieved with this method. We conclude that femtosecond laser technology may be able to perform a variety of corneal refractive procedures with high precision, offering advantages over current mechanical and laser devices and techniques View full abstract»

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  • Experimental validation of a backpropagation algorithm for three-dimensional breast tumor localization

    Page(s): 1049 - 1057
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    To validate a new backpropagation algorithm for three-dimensional (3-D) tumor localization in breast tissue with a two-dimensional measurement, we performed experiments on breast phantoms using a heterodyne, frequency-domain photon migration system. The near-infrared (680 or 780 nm) laser diode used to provide illumination was intensity modulated at both megahertz (20-60 MHz) and kilohertz (10 kHz) frequencies. The breast phantoms were made of plastic resin with a variety of simulated tumors imbedded inside and then scanned with the system in a planar geometry. With megahertz modulation signals, both of the amplitude and phase of the transmitted light were used in the data reduction process, whereas with kilohertz modulation signals only the amplitudes were used for the reconstruction. In both cases, the backpropagation reconstruction algorithm was used to accomplish 3-D localization of the imbedded tumors. In all cases, the reconstructed locations for the hidden objects are in good agreement with the true values. Our current work demonstrates the possibility and potential of developing low-cost optical tomographic instruments View full abstract»

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  • Time-gated transillumination of objects in highly scattering media using a subpicosecond optical amplifier

    Page(s): 895 - 901
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    We have developed an optical system that simultaneously selects and amplifies photons in a time window of less than 10 ps. This new subpicosecond optical amplifier allowed us to realize one-dimensional images of a striped pattern with a spatial resolution of 200-μm through a 30-mm liquid scattering medium. Monte Carlo simulations were performed to study the relative importance of parameters characterizing the medium and the time-gated amplifying system in relation to the image sharpness. The potential application of this system in medical imaging is discussed View full abstract»

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  • Optical Doppler tomography

    Page(s): 1134 - 1142
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    Optical Doppler tomography (ODT) is an imaging modality that takes advantage of the short coherence length of a broad-band light sources to perform micrometer-scale, cross-sectional imaging of tissue structure and blood flow dynamics simultaneously. The authors review in this paper the principal of ODT and its applications. Results from in vitro and in vivo model studies demonstrated that ODT can map the blood flow velocity profile with high spatial resolution in scattering medium. ODT detection mechanisms are illustrated using Monte Carlo simulations. The application of ODT to image brain hemodynamics is demonstrated. Finally, the authors discuss the limitations of the current technology and application of a phase resolved technique to improve image speed and quality View full abstract»

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  • Optical coherence tomography: high-resolution imaging in nontransparent tissue

    Page(s): 1185 - 1192
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    Optical coherence tomography (OCT) is a method of high-resolution imaging originally developed for the transparent tissue of the eye. Recently, the technology has been advanced toward the difficult challenge of imaging in nontransparent tissue. In the paper, three topics are addressed. First, the principles behind OCT imaging are discussed. Second, the difficulties associated with OCT imaging in nontransparent tissue are outlined. Finally, the feasibility of OCT for medical imaging is discussed. Specifically, OCT demonstrates its greatest potential in situations where conventional biopsy is either dangerous or ineffective View full abstract»

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  • Picosecond electronic time-gated imaging of bones in tissues

    Page(s): 916 - 922
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    Two-dimensional in vivo optical images of metacarpal bones of a human palm and in vitro images of turkey and chicken bones embedded in tissues were obtained in the near-infrared region using femtosecond pulse transillumination and picosecond electronic time-sliced detection technique. A small hole drilled in chicken bone and embedded in chicken breast tissue was imaged using early arriving light. Time-gated fluorescence images of an interior marrow region of a bone injected with a fluorescent dye were recorded. The techniques have potential for monitoring bone fracture, bone diseases such as, osteoporosis and arthritis, and diseases that originate in or affect bone marrow View full abstract»

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  • High magnification imaging with a laser-based hard X-ray source

    Page(s): 911 - 915
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    The usefulness of laser-based X-ray sources for imaging is assessed. A very bright point source of 20-keV X-rays, with a diameter of 10 μm, has been created by the interaction of a high contrast femtosecond laser pulse with solid targets. This X-ray source has been used for a feasibility study of high magnification imaging. Images of mammography phantoms have been obtained and spatial resolution of 35 μm has been demonstrated with object magnification up to ten. A new laser technology recently introduced allows the construction of very intense, compact and cost effective short pulse laser systems and makes now the ultrafast laser based hard X-ray sources very attractive for medical application View full abstract»

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  • Sensitivity of laser opto-acoustic imaging in detection of small deeply embedded tumors

    Page(s): 981 - 988
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    Current imaging modalities fail to detect small tumors in the breast. Opto-acoustic tomography is a novel technique for early cancer detection with promising diagnostic capability. The experimental limit of sensitivity and maximal depth of the laser opto-acoustic detection for small model tumors located within bulk phantom tissue were studied. Two phantoms with optical properties similar to that of breast tissue in the near infrared spectral range were used in these studies: turbid gelatin slabs with the thickness of 100 mm and chicken breast muscle slabs with the thickness of up to 80 mm. Gelatin spheres with enhanced absorption coefficient relative to the background absorption and liver tissue were used to simulate small tumors. The experiments demonstrated the capability of laser optoacoustic imaging to detect and localize phantom tumors with the diameter of 2 mm at a depth of up to 60 mm within the gelatin phantoms and 3×2×0.6-mm piece of liver tissue within 80-mm chicken breast tissue. Theoretical studies on sensitivity of opto-acoustic detection at various diameters, depths of location, and absorption coefficients of small tumors were performed using the experimental data. Our results suggest that the opto-acoustic imaging may occupy a significant niche in early detection of cancer in the breast and other organs View full abstract»

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  • Optical coherence tomography (OCT): a review

    Page(s): 1205 - 1215
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    This paper reviews the state of the art of optical coherence tomography (OCT), an interferometric imaging technique that provides cross-sectional views of the subsurface microstructure of biological tissue. Following a discussion of the basic theory of OCT, an overview of the issues involved in the design of the main components of OCT systems is presented. The review concludes by introducing new imaging modes being developed to extract additional diagnostic information View full abstract»

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  • High-power continuous-wave 3- and 2-μm cascade Ho3+:ZBLAN fiber laser and its medical applications

    Page(s): 936 - 943
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    A new medical fiber laser oscillating at two useful wavelengths (3 and 2 μm) is reported. We have demonstrated highly efficient and high-power continuous-wave cascade oscillation at room temperature with a holmium ion-doped fluoride glass fiber laser pumped with a 1.15-μm fiber Raman laser. The simultaneous oscillation wavelengths were 3 and 2 μm, and their combined output power was 3.0 W with a slope efficiency of 65%. To our best knowledge, this is the first achievement of watt-level-output power in the mid-infrared region with ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) glass fiber. In experiments to evaluate potential for medical applications, we tested the two wavelength beam as a laser surgical knife on soft rabbit tissues and demonstrated that it had strong cutting capability, and that the coagulation layer thickness could be controlled by varying the power ratio of the two-wavelength laser View full abstract»

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  • Polarization effects in optical coherence tomography of various biological tissues

    Page(s): 1200 - 1204
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    Polarization sensitive optical coherence tomography (PS-OCT) was used to obtain spatially resolved ex vivo images of polarization changes in skeletal muscle, bone, skin and brain. Through coherent detection of two orthogonal polarization states of the signal formed by interference of light reflected from the biological sample and a mirror in the reference arm of a Michelson interferometer, the depth resolved change in polarization was measured. Inasmuch as any fibrous structure will influence the polarization of light, PS-OCT is a potentially powerful technique investigating tissue structural properties. In addition, the effects of single polarization state detection on OCT image formation is demonstrated View full abstract»

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  • Single-pulse 30-J holmium laser for myocardial revascularization-a study on ablation dynamics in comparison to CO2 laser-TMR

    Page(s): 969 - 980
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    Endocardial laser revascularization (ELR) is a new technique to treat coronary heart disease in a percutaneous, minimally invasive approach. A holmium laser (λ=2.12 μm) was developed to emit pulse energies of up to 30 J in order to ablate the desired channels in a single laser pulse. The energy was transmitted by multimode flexible optical waveguides as required for ELR. Ablation dynamics were investigated in two model systems, water serving as blood model and polyacrylamide (PAA) as a transparent tissue phantom. Measurements were undertaken using pulse energies of 12 J at pulse durations of 2.2 and 8 ms with a beam diameter of 1 mm. For comparison with the clinically established method of transmyocardial revascularization (TMR), ablations were also investigated with a standard 800 W TMR CO2 laser. The dynamics were recorded with a drum camera and stroboscope illumination providing a high framing rate of a single ablation process. Tissue ablation was quantified with the holmium laser in vitro on porcine heart tissue using pulse energies of up to 20 J. Tissue morphology was evaluated using polarization light microscopy to determine thermal and mechanical collateral damage zones. Oscillating vapor bubble channels were found in water and PAA with all laser systems and parameters used. Quasi-static vapor bubbles are observed in water in the millisecond time range using the holmium laser. CO2 laser radiation performed deeper channels in PAA than holmium laser pulses using the same radiant exposure. Channel depths of up to 10 mm were achieved with the holmium laser in myocardial tissue with pulse energies of 17 J, Thermal damage zones of about 150 μm for the CO2 and 500 μm for the holmium laser were found. The orientation of myocardial fibrils significantly influences the shape of the ablated cavities and the thermo-mechanical collateral damage zones. In conclusion, the results are very encouraging and demonstrate the potential of a catheter-based minimal invasive procedure for heart reperfusion using single high energy laser pulses View full abstract»

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  • Fluorescence lifetime imaging: an application to the detection of skin tumors

    Page(s): 923 - 929
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    A portable system based on fluorescence lifetime imaging has been developed and tested for the detection of skin tumors in humans. The Heme precursor δ-aminolevulinic acid, which promotes the preferential accumulation of the endogenous Protoporphyrin IX (PpIX) in proliferative tissues, is used as an exogenous marker to target the tumor, δ-aminolevulinic acid is topically administered to the patient 1 h before the measurement. Then, using a gated intensified camera, two or more images of the sample are acquired after different delays with respect to the excitation pulses. The images are processed in real time in order to calculate the spatial map of the fluorescence decay time of the sample. The localization of the tumor is based on the longer decay time detected in neoplastic tissues as a result of the stronger emission of PpIX, which has a long decay time, and the reduction in the short living natural tissue fluorescence View full abstract»

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  • Polarized light scattering spectroscopy for quantitative measurement of epithelial cellular structures in situ

    Page(s): 1019 - 1026
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    We report an in situ method of probing the structure of living epithelial cells, based on light scattering spectroscopy with polarized light. The method makes it possible to distinguish between single backscattering from uppermost epithelial cells and multiply scattered light. The spectrum of the single backscattering component can be further analyzed to provide histological information about the epithelial cells such as the size distribution of the cell nuclei and their refractive index. These are valuable quantities' to detect and diagnose precancerous changes in human tissues View full abstract»

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  • Evaluation of four different laser systems for a minimally invasive scoliosis treatment

    Page(s): 1067 - 1071
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    Today most surgical treatment of spinal deformations is concentrated on invasive techniques with long operation times and major effects on the patient's mobility. The proposed minimally invasive technique using laser light for tissue ablation offers a possibility of gentle scoliosis treatment. Four different laser systems including argon, Nd:YAG (Q-switched), Nd:YAG (CW) and Ho:YAG were compared with respect to thermal damage to adjacent tissue, ablation rates, efficiency and laser handling. For in vitro investigation, fresh lamb spine was used. Comparison showed that the Ho:YAG laser is the most appropriate laser for the given goal, however, heating of adjacent tissue had to be minimized by intermediate laser action and irrigation View full abstract»

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  • Frequency-domain optical detection of subsurface blood vessels: experimental and computational studies using a scattering phantom

    Page(s): 1032 - 1039
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    A simple method to localize blood vessels beneath the surface of tissue could be very useful during laparoscopic and endoscopic procedures. However, the detection of blood vessels deep within tissue using light is limited by tissue scattering. In the study, frequency-domain photon migration methods were used to detect blood vessels within a scattering medium. The depth at which blood vessels could be detected was greater than 10 mm. The experimental measurements agree well with predictions obtained from the diffusion approximation to the radiative transport equation. These studies demonstrate the potential of frequency-domain optical methods to detect subsurface blood vessels View full abstract»

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  • Tunable diode laser spectroscopy at 1.6 and 2 μm for detection of Helicobacter pylori infection using 13C-urea breath test

    Page(s): 1040 - 1048
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    Tunable diode laser spectroscopy has been applied to diagnosis of Helicobacter pylori by detecting the 13CO2 to isotope ratio in human breath. A number of line pairs in the 1.6- and 2.0-μm band suitable for isotope ratio detection has been investigated in terms of temperature and pressure stability of the detected isotope ratio. Two wavelength modulated diode laser absorption spectrometers (WMS), one in each band, were set up to find the detection limit in isotope abundance difference. Isotope ratio measurements have been performed on 13CO2 enriched gases with isotope ratios calibrated against an isotope ratio mass spectrometer (IRMS). The agreement between the delta values measured with the WMS technique and the IRMS was excellent. Eight breath samples from otherwise healthy volunteers were simultaneously analyzed by IRMS and the present method for possible infection with Helicobacter pylori View full abstract»

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  • Laser-generated stress waves and their effects on the cell membrane

    Page(s): 997 - 1003
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    High-power lasers can generate well characterized stress (pressure) waves. The characteristics of the stress waves can be controlled by the appropriate choice of the laser parameters and the properties of the target material. Laser-generated stress waves can alter the structure and function of cells in vitro. Furthermore, they render the cell membrane permeable. Molecules present in the extracellular medium diffuse into the cytoplasm under the concentration gradient. Subsequently, the plasma membrane reseals, keeping the exogenous molecules inside the cell. Laser-generated stress waves can provide a potentially powerful tool for drug delivery View full abstract»

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  • Laser-induced photodecomposition of amino acids and peptides: extrapolation to corneal collagen

    Page(s): 1107 - 1115
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    Recent studies on the laser photochemistry of aromatic and aliphatic amino acids and small peptides in neutral aqueous solution are described. We report on major parameters such as photoionization and photodecomposition quantum yields for the cases of direct (and indirect) photolysis. Although four different UV laser sources were used, the impact is made on 193-nm-induced photoprocesses. The relative probabilities of photochemical damage of specific residues are estimated. It is shown that the peptide bond is likely to be the main target in collagen. Its scission could be the most important photochemical reaction taking place at 193-nm laser irradiation of the cornea. We have found strong arguments in favor of the ablative photodecomposition mechanism of photorefractive keratectomy View full abstract»

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  • Application of the 980-nm diode laser in stereotaxic surgery

    Page(s): 1090 - 1094
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    With recent developments in laser technology, diode laser and optical delivery systems have become highly promising surgical devices with advantages of lower cost and higher precision. The aim of the study was to test the 980-nm diode laser for its potential use in stereotaxic surgery. In our dosimetric study, the response of cortical tissue to different energy levels of laser irradiation was investigated with different exposure durations. In vivo stereotaxic neurosurgical procedure was performed on female Wistar rats weighing 180 to 220 gr. In order to investigate the lesioning effects of the 980-nm diode laser as a function of pulse duration, laser power was adjusted to 2.0 and 3.0 W with exposure times ranging from 1.3 to 3.0 s resulting in an irradiance of 5.97 to 17.91 J/mm2. Histologic investigation of brain specimens indicated that the 980-nm diode laser has the potential to create lesions in stereotaxic surgery. With proper selection of power level and exposure duration, target tissues could be evaporated and/or coagulated. We found the 980-nm diode laser a promising tool for neurosurgical applications View full abstract»

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  • On the possibility of high-precision photothermal microeffects and the measurement of fast thermal denaturation of proteins

    Page(s): 954 - 962
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    The precision of laser-induced effects is often limited by thermal and thermomechanical collateral damage. Adjusting the pulsewidth of the laser to the size of the absorbing structure can at least avoid thermal side effects and facilitates a selective treatment of vessels or pigmented cells. Further extending the precision of thermal effects below cellular dimensions by using nanometer sized particles could open up new fields of applications for lasers in medicine and biology. Calculations show that under irradiation with nano- or picosecond laser pulses gold particles of submicrometer size can easily be heated by several hundred K. High temperatures have to be used for subcellular thermal effects, because heat confinement to such small structures requires the thermal damage to occur in extremely short times. Estimating the denaturation temperature by extrapolating the Arrhenius equation from a time range of minutes and seconds into a time range of nano- and picoseconds leads to temperatures between 370 K-470 K. There is evidence that in aqueous media, due to the surface tension, these temperatures can be generated at the surface of nanometer sized particles without vaporization of the surrounding water. In order to show whether or not an extrapolation of the damage rates over six to nine orders of magnitude gives correct data, a temperature-jump experiment was designed and tested which allows to measure denaturation rates of proteins in the millisecond time range. Denaturation of chymotrypsin was observed within 300 ps at temperatures below 380 K. The rate constants for the unfolding of chymotrypsin followed the Arrhenius equation up to rates of 3000 s-1 View full abstract»

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Aims & Scope

Papers published in the IEEE Journal of Selected Topics in Quantum Electronics fall within the broad field of science and technology of quantum electronics of a device, subsystem, or system-oriented nature.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
John Cartledge
Queen's University