Shifted position-diffuse reflectance imaging is a technique for the non-invasive assessment of microcirculation. In this study, its lateral resolution and imaging depth were determined to be 95 μm and 295 μm, respectively, by Monte-Carlo simulations.
Lasers have become a generally accepted tool for surgery due to their advantages compared to traditional approaches like the scalpel. However, lasers lack a feedback system for safe laser guidance. This problem prevents the potential laser application for a lot of medical cases in the clinical environment. In this work, a new tissue differentiation modality which might be implemented as a feedback system using remote speckle-sensing is presented. This modality is tested on three tissue types and the results are discussed.
The Er:YAG laser has gained significant interest in the field of oral surgery due to its high water absorptivity, precision and patient acceptance. However, its application is limited by the lack of a contact-free feedback system which would enable safe laser guidance. In this work, a potential new, robust feedback modality based on speckle-analysis is presented which detects the acoustic signals produced during laser surgery. Oral soft- and hard tissue samples are investigated ex-vivo for its differentiation capability using the speckle modality. This technique might help to broaden the clinical application of Er:YAG lasers.
To provide clinically relevant insights into the device performance of an optical imaging approach to reconstruct the superficial cutaneous micro-circulation (skin angiography), a phantom device with turbid matrix and perfusable micro-vessels is essential. In this work, we describe a novel microfluidic-based device to mimic the micro-vessels and the turbid nature of the epidermis and dermis. This phantom device contains a hollow assay with a diameter of the channels of 50 μm. The hollow assay includes the geometry of the inlet, the river-like assay, and the outlet, which can be perfused by e.g. meta-hemoglobin solution. This imitates the superficial micro-circulation in the skin. The absorption coefficient μa and the reduced scattering coefficient μs' are adjusted to match those of skin. As an application case, we attempt to reconstruct a 2-D velocity field of the hemoglobin flow in the scattering microfluidic device via the Doppler-mode of an OCT.
An imging resolution of micron-scale has not yet been discovered by diffuse optical imaging (DOI), while a superficial response was eliminated. In this work, we report on a new approach of DOI with a local off-set alignment to subvert the common boundary conditions of the modified Beer-Lambert Law (MBLL). It can resolve a superficial target in micron scale under a turbid media. To validate both major breakthroughs, this system was used to recover a subsurface microvascular mimicking structure under an skin equivalent phantom. This microvascular was included with oxy-hemoglobin solution in variant concentrations to distiguish the absolute values of CtRHb and CtHbO2 . Experimental results confirmed the feasibility of recovering the target vascular of 50 µm in diameter, and graded the values of the concentrations of oxy-hemoglobin from 10 g/L to 50 g/L absolutely. Ultimately, this approach could evolve into a non-invasive imaging system to map the microvascular pattern and the associated oximetry under a human skin in-vivo.
Remote laser surgery lacks of haptic feedback during the laser ablation of tissue. Hence, there is a risk of iatrogenic
damage or destruction of anatomical structures like nerves or salivary glands. Diffuse reflectance spectroscopy provides
a straightforward and simple approach for optical tissue differentiation. We measured diffuse reflectance from seven
various tissue types ex vivo. We applied Linear Discriminant Analysis (LDA) to differentiate the seven tissue types and
computed the area under the ROC curve (AUC). Special emphasis was taken on the identification of nerves and salivary
glands as the most crucial tissue for maxillofacial surgery. The results show a promise for differentiating tissues as
guidance for oral and maxillofacial laser surgery by means of diffuse reflectance.
In the current study we try to optimise the cancerous/normal tissue contrast perception using white light and
autofluorescence image processing. We deconvolved the RGB channels of both white light and autofluorescence
images pixel by pixel and pointed out the best contrast enhancement technique, manipulating each channel seperately.
By using false-color mapping according to a particular Look-Up Table, the borders between normal and
cancerous area of the tissue are better delineated. Cancer tissue identification was confirmed by the histological
examination that followed our investigation.
Laser surgery gives the possibility to work remotely which leads to high precision, little trauma and high level sterility.
However these advantages are coming with the lack of haptic feedback during the laser ablation of tissue. Therefore
additional means are required to control tissue-specific ablation during laser surgery supporting the surgeon regardless of
experience and skills. Diffuse Reflectance Spectroscopy provides a straightforward and simple approach for optical
tissue differentiation. We measured diffuse reflectance from four various tissue types ex vivo. We applied Linear
Discriminant Analysis (LDA) to differentiate the four tissue types and computed the area under the ROC curve (AUC).
Special emphasis was taken on the identification of nerve as the most crucial tissue for maxillofacial surgery. The results
show a promise for differentiating soft tissues as guidance for tissue-specific laser surgery by means of the diffuse
reflectance.
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