Hyperspectral imaging is an optical technique that recently started being used in medical field. The correct extraction of spectral and spatial information from hyperspectral images depends on preprocessing, processing and analysis methods applied for an accurate diagnosis and monitoring medical treatments. A fundamental task in preprocessing hyperspectral images is the elimination of various types of noise generated by the hyperspectral systems. One of the major causes for the noise in a hyperspectral system is dark current noise. This type of noise arises from the temperature difference between environment and charge-coupled device of the hyperspectral camera. Electrons are generated over time and they are independent of the light falling on the detector. These electrons are captured by the potential wells of the charge-coupled device and counted as signal. The dark current noise removal can lead to an improvement in the performance of classification, target detection, anomaly detection and mapping methods, thus contributing to a better and more accurate diagnosis. Two denoising techniques - principal component analysis and minimum noise fractions were used until now in medical hyperspectral imaging applications. In this paper, the wavelet transform was proposed as a denoising technique for medical applications. The study was performed in both laboratory and clinical conditions. Two hyperspectral systems were used for the hyperspectral images acquisition of rabbit liver and a burn wound located on the posterior side of the patient left leg respectively using the same pushbroom hyperspectral camera but with two different scanning components (translation table and scanning mirror). The pushbroom hyperspectral camera acquires the image collecting the x-axis and λ information completely at the same time for a line on the y-axis. The two scanning components are used to move the sample (liver or patient leg) across the field of view of the hyperspectral camera so that the images are acquired line by line. The experimental results showed that the proposed denoising technique achieves better performance when applied to hyperspectral images acquired under laboratory conditions than in clinical situations. In conclusion, the wavelet transform could be considered a successful approach to denoising in laboratory hyperspectral measurements.
Testing the human body’s reaction to hypoxia (including the one generated by high altitude) is important in aeronautic medicine. This paper presents a method of monitoring blood oxygenation during experimental hypoxia using hyperspectral imaging (HSI) and a spectral unmixing model based on a modified Beer–Lambert law. A total of 20 healthy volunteers (males) aged 25 to 60 years were included in this study. A line-scan HSI system was used to acquire images of the faces of the subjects. The method generated oxyhemoglobin and deoxyhemoglobin distribution maps from the foreheads of the subjects at 5 and 10 min of hypoxia and after recovery in a high oxygen breathing mixture. The method also generated oxygen saturation maps that were validated using pulse oximetry. An interesting pattern of desaturation on the forehead was discovered during the study, showing one of the advantages of using HSI for skin oxygenation monitoring in hypoxic conditions. This could bring new insight into the physiological response to high altitude and may become a step forward in air crew testing.
Hyperspectral imaging is a technology that is beginning to occupy an important place in medical research with good prospects in future clinical applications. We evaluated the role of hyperspectral imaging in association with a mixture-tuned matched filtering method in the characterization of open wounds. The methodology and the processing steps of the hyperspectral image that have been performed in order to obtain the most useful information about the wound are described in detail. Correlations between the hyperspectral image and clinical examination are described, leading to a pattern that permits relative evaluation of the square area of the wound and its different components in comparison with the surrounding normal skin. Our results showed that the described method can identify different types of tissues that are present in the wounded area and can objectively measure their respective abundance, which proves its value in wound characterization. In conclusion, the method that was described in this preliminary case presentation shows promising results, but needs further evaluation in order to become a reliable and useful tool.
This paper proposes to explore the pattern of lymphoblastic cell line K562 cells death, the effects on their cell cycle
induced by 5,10,15,20-tetra-p-sulphonato-phenyl-porphyrin-based photodynamic therapy (TS4PP-PDT). Flow cytometry
combined with Annexin V-FITC/PI labeling was used to detect the pattern of K562 cells' death induced by TS4PP-PDT.
These effects frequently lead to induction of apoptosis by the mitochondrial pathway involving caspases. The
transmission electron microscope (TEM) and confocal laser scanning microscopy (CLSM) were used to detect the
localization and time-biodistribution of sensitizers in the cells. After 1 h of TS4PP administration, the sensitizer shows a
non-uniform distribution, following that after 4h of administration, the sensitizer to be localized in some cellular targets
and an increased fluorescence intensity is being detected. After 8 h and 24 h post-administration, the sensitizer is
released from the cells and the light-irradiation (He-Ne laser, &lgr;=632.8 nm) could start. Immediately after irradiation,
many typical apoptotic bodies were seen in the cells treated. Most of the cells treated were necrotic at 24 hours following
irradiation.
This work presents some contribution in the non-conventional optical components field. The idea is concerning to fluid optical components, having in view to elaborate a documentation--like a catalogue of optical fluids--for optical system design. The using of optical fluids represents a new method of attaining apochromatic color correction in refractive optical systems.
The medical laser applications use the thermal effects of laser irradiation. The present work contains applications of the thermovision. This method offers the following advantages recording and processing of the thermal distribution on the irradiated zone. The study has in view the development of an algorithm of work for an useful data base regarding the laser application in medicine. The experiments used Ar laser, laser diode and some kinds of biological tissues. The paper presents some thermal distributions before, during and after laser irradiation and the images processing.
This paper reports on the optical properties of polycrystalline p-type InxGa1-xSb (x equals 0.20) over the wavelength range 15 - 30 micrometers , at room temperature. The material was obtained by direct synthesis from the elements and rapidly crystallized following a particular temperature regime. Transmittance and reflectance measurements were performed at room temperature by using a SPECORD M80 spectrophotometer. From the resulted values we calculated the absorption coefficient (alpha) as a function of the photon energy. Considerations are made concerning the peculiarities involved by the polycrystalline structure and the surface imperfections on the absorption phenomena over the mentioned wavelength range.
In vitro (absorption spectroscopy) and in vivo (fluorescence microscopy) studies before and after the uptake of intraperitoneal injected Hematoporphyrin Derivative (HpD) were made in mice. The absorption spectrum of HpD is characterized by four bands in the visible region with decreasing absorption towards longer wavelengths (510 nm, 540 nm, 568 nm and 621 nm). These spectra were obtained only at low concentration (10-5 M). After (15 - 30) minutes postirradiation (He-Ne laser, 1 mW) the features of curves were the same with those of nonirradiated samples but with a deplacement of wavelengths. The presence of laser emitting products was pointed out by fluorescence microscopy (cryostat section in fluorescence microscopy).
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