Identification of tumor margins using diffuse reflectance spectroscopy with an extended-wavelength spectrum in a porcine model.

OBJECTIVE: A novel extended-wavelength diffuse reflectance spectroscopy (EWDRS) technique is being developed for future clinical non-invasive tumor margin delineation. In this study, the ability of EWDRS to identify the margins of pigmented skin lesions in an in vivo pig model was evaluated. MATERIALS AND METHODS: Extended-wavelength diffuse reflectance spectroscopy recordings (350-1550 nm) were made on 13 pigmented skin lesions and non-pigmented skin, as a reference. The hand-held probe was swept toward the pigmented area until the signal changed, thus indicating that the margin had been identified. A needle was inserted as a marker, and tissue samples were sent for histological analysis. The distance between the EWDRS-defined border and the histological border was measured by 3 independent examiners. RESULTS: The median difference between the EWDRS-defined border and the histological border was 70 µm toward the pigmented tissue (range: -579 to 538 µm). A Pearson correlation coefficient of .95 was obtained for the examiners. CONCLUSIONS: Extended-wavelength diffuse reflectance spectroscopy can be used in vivo to delineate the border of pigmented skin lesions in a porcine model with high accuracy, indicating that it may be a useful tool for non-invasive tumor margin delineation in the future.

Cavity enhanced absorption spectroscopy of multiple trace gas species using a supercontinuum radiation source.

Supercontinuum radiation sources are attractive for spectroscopic applications owing to their broad wavelength coverage, which enables spectral signatures of multiple species to be detected simultaneously. Here we report the first use of a supercontinuum radiation source for broadband trace gas detection using a cavity enhanced absorption technique. Spectra were recorded at bandwidths of up to 100 nm, encompassing multiple absorption bands of H(2)O, O(2) and O(2)-O(2). The same instrument was also used to make quantitative measurements of NO(2) and NO(3). For NO(3) a detection limit of 3 parts-per-trillion in 2 s was achieved, which corresponds to an effective 3sigma sensitivity of 2.4 x 10(-9) cm(-1)Hz(-1/2). Our results demonstrate that a conceptually simple and robust instrument is capable of highly sensitive broadband absorption measurements.

Use of (130)Te(2) for frequency referencing and active stabilisation of a violet extended cavity diode laser.

This paper reports on the use of (130)Te(2) absorption lines in active laser-locking, and in frequency referencing, of the emission of a violet extended cavity diode laser with a wavelength of around 410 nm. We note the existence of closely spaced tellurium absorption lines, suitable for referencing purposes in gas sensing applications, at wavelengths below the lower limit (417 nm) of the spectral region covered by the tellurium atlas [J. Cariou, P. Luc, Atlas du spectre d'Absorption de la Molecule de Tellure, CNRS, Paris, 1980]. The absolute positions of the lines in the acquired spectra were estimated by comparison to a simultaneously acquired fluorescence spectrum of atomic indium, and were identified using calculations based on fundamental spectroscopic data. The laser frequency was stabilised within a range of 40 MHz, which is negligible compared to typical transition widths at atmospheric pressure.

Nonlinear diffusion filtering of images obtained by planar laser-induced fluorescence spectroscopy.

The application of nonlinear anisotropic diffusion filtering to reduce noise and enhance contours in images obtained by two-dimensional planar laser-induced fluorescence (PLIF) spectroscopy is presented. In this process the diffusion coefficient is locally adapted, becoming negligible as object boundaries are approached. Noise is efficiently removed, and object contours are strongly enhanced. The technique is demonstrated with PLIF images obtained from the OH radical recorded in turbulent flames. We show that nonlinear diffusion is suitable as a preprocessing step, before image segmentation becomes possible, and we demonstrate how the technique is applied for the quantitative extraction of flame reaction boundaries from PLIF data.

Effect of femoral stem length on stress raisers associated with revision hip arthroplasty.

The objective of this study was to experimentally determine the optimal length of a femoral component in revision total hip arthroplasty (THA). Embalmed cadaveric femurs were loaded in a physiologic manner, and strains on the lateral cortex were measured. Two kinds of defects were tested to simulate THA after removal of a nail plate and after removal of a loose femoral stem. A drill hole was made in the lateral cortex of the femur to simulate the removal of a nail plate. A reaming defect was made, using flexible reamers to thin the cortex from the lesser trochanter distally to a site corresponding to the tip of a standard femoral component, to simulate THA after removal of a previously inserted femoral stem. Femurs were tested intact, with the defects, and after insertion of femoral components with stem lengths of 100 to 250 mm. The strain increased with the creation of a defect and decreased with the insertion of an implant. For a femur with a defect, the strain was minimized when the stem length extended 1.5 femoral diameters past the defect.