Peter J. Dwyer

Confirmation of onychomycosis by in vivo confocal microscopy

Onychomycosis is common in adults and constitutes 20% of all nail disease. Widely used methods to confirm a clinical diagnosis of onychomycosis often yield negative results (ie, potassium hydroxide [KOH] preparation) or are slow (ie, dermatophyte cultures). We report a case of onychomycosis in which we used in vivo confocal microscopy to diagnose the disease; we also correlated our findings with results from routine KOH preparations. On the basis of our findings, we hypothesize that in vivo confocal microscopy may be faster and more accurate than the conventional microscope used in KOH preparations in the diagnosis of onychomycosis.

Optical integrating balloon device for photodynamic therapy

It is difficult to deliver light uniformly and efficiently over the complex shapes presented by various organs for photodynamic therapy (PDT). A balloon delivery device for photodynamic therapy was designed and tested for treatment of various anatomic tissues. The device uses the principle of optical integration by multiple internal diffuse reflections to achieve uniform output illumination.

Hyperspectral imaging for dermal hemoglobin spectroscopy

It has been shown previously that images collected at selected wavelengths in a sufficiently narrow bandwidth can be used to produce maps of the oxygen saturation of hemoglobin in the dermis. A four-wavelength algorithm has been developed based on a two-layer model of the skin, in which the blood is contained in the lower layer (dermis), while the upper layer attenuates some of the reflection and adds a clutter term. In the present work, the algorithm is compared analytically to simpler algorithms using three wavelengths and based on a single-layer model. It is shown through Monte-Carlo models that, for typical skin, the single-layer model is adequate to analyze data from fiber-optical reflectance spectroscopy, but the two-layer model produces better results for imaging systems. Although the model does not address the full complexity of reflectance of a two-layer skin, it has proven to be sufficient to recover the oxygen saturation, and perhaps other medically relevant information. The algorithm is demonstrated on a suction blister, where the epidermis is removed to reveal the underlying dermis. Applications for this imaging modality exist in dermatology, in surgery, and in developing treatment plans for various diseases.

Mapping blood oxygen saturation using a multispectral imaging system

Recent advances in imaging spectroscopy provide the opportunity for mapping the oxygen saturation of blood in skin with high accuracy, large spatial coverage, small spatial resolution, and high update rate. A four-wavelength algorithm, specifically designed to compute the oxygen saturation of hemoglobin, in vivo, from a set of narrow-band visible images was used to analyze various skin tissue disorders. To illustrate the spatial capability of this algorithm, mapping of the oxygen saturation of normal skin, hypoxic tissue and various skin lesions was performed using reflectance spectroscopy, demonstrating the spatial resolution of the images of blood oxygen in the tissues. To explore the accuracy of the algorithm, Monte-Carlo modeling was used to generate reflectivities of skin with known parameters. These reflectivities were used to evaluate the limiting effects of quantization error, photon noise, and finite filter bandwidth on the accuracy of the algorithm. In addition, a signal-to-noise analysis was performed to determine the illumination requirements. It is shown that accurate maps of blood oxygen can be produced with good spatial resolution.

Confocal Reflectance Theta Line-Scanning Microscope for Imaging Human Skin

A confocal reflectance theta line scanning microscope demonstrates imaging of nuclear and cellular detail in human epidermis in vivo. Experimentally measured line-spread functions determine the instrumental optical section thickness to be 1.7 +/- 0.1 microm and the lateral resolution to be 1.0 +/- 0.1 microm. Within human dermis (through full-thickness epidermis), the measured section thickness is 9.2 +/- 1.7 microm and the lateral resolution is 1.7 +/- 0.1 microm. An illumination line is scanned directly in the pupil of the objective lens, and the backscattered descanned light is detected with a linear array, such that the theta line scanner consists of only seven optical components.

Confocal theta line-scanner for imaging skin: A comparison to the point scanner

A confocal reflectance theta line-scanner provides optical sectioning of 2-10 ?m and images nuclear, cellular and architectural detail within human skin in vivo, comparable to that of point scanners and histology. Key design challenges are mismatch between illumination and detection paths, linear detector sensitivity, pupil edge aberrations and pixel crosstalk.

Confocal reflectance theta line-scanner for imaging human skin in vivo

A confocal reflectance theta line-scanning microscope provides axial resolution of 2-8 µm and images nuclear, cellular and architectural detail within human skin in vivo.