Permanent grasslands (meadows and pastures) are the most common agricultural land use type covering 34% (0.65 million hectares) of agricultural land in Latvia. The Common Agriculture Policy (CAP) stipulates that the EU Member States have to designate permanent grasslands, ensure that farmers do not convert or plough them and that the ratio of permanent grasslands to the total agricultural area does not decrease by more than 5% in order to receive support payments. Mapping of grasslands and assessment of their biomass (productivity) is of interest for evaluation of bioeconomical potential. Field sampling is the most precise approach assessment of biomass but it is expensive and timeconsuming when applied to a larger territory. In contrast, remote sensing can provide large coverage and mapping of grass biomass distribution for further use in the assessment of the available fodder for livestock and/or the optimal location for biomass-based renewable energy production sites.
The study was carried out in Cesis Municipality in Latvia using airborne flying laboratory ARSENAL – the constellation of hyperspectral imagers in the visible to mid-wave infrared (400-5000 nm) spectral range, topographic LiDAR and high-resolution RGB camera for simultaneous multi-sensor data acquisition. Hyperspectral data were used for both mapping of grasslands and assessment of grass biomass. Different spectral ranges and machine learning algorithms were tested in order to find the best one. The performance of Sentinel-2 like spectral bands also was tested for further possible further use of multispectral satellite data.
In this study, we aimed to determine whether the combination of electroporation (EP) and ultrasound (US) waves (sonoporation) can affect the plasmid DNA transfection to mice tibialis cranialis muscle. Multispectral imaging technique combined with fluorescence spectroscopy point measurements has been used for the transcutaneous detection of enhanced green fluorescent protein (EGFP) fluorescence, providing information on location and duration of EGFP expression. We found that electrosonoporation, commonly enhancing pDNA transfection in vitro, had no positive effect on EGFP transfection efficiency increase in vivo with respect to electroporation alone. We presume that this may be associated with decreased viability of transfected fibers.
Remote sensing has proved to be an accurate and reliable tool in clear water environments like oceans or the Mediterranean Sea. However, the current algorithms and methods usually fail on optically complex waters like coastal and inland waters. The whole Baltic Sea can be considered as optically complex coastal waters. Remote assessment of water quality parameters (eg., chlorophyll-a concentration) is of interest for monitoring of marine environment, but hasn’t been used as a routine approach in Latvia.
In this study, two simultaneous hyperspectral airborne data and in situ measurement campaigns were performed in the Gulf of Riga near the River Daugava mouth in summer 2015 to simulate Sentinel-3 data and test existing algorithms for retrieval of Level 2 Water products. Comparison of historical data showed poor overall correlation between in situ measurements and MERIS chlorophyll-a data products. Better correlation between spectral chl-a data products and in situ water sampling measurements was achieved during simultaneous airborne and field campaign resulting in R2 up to 0.94 for field spectral data, R2 of 0.78 for airborne data. Test of all two band ratio combinations showed that R2 could be improved from 0.63 to 0.94 for hyperspectral airborne data choosing 712 and 728 nm bands instead of 709 and 666 nm, and R2 could be improved from 0.61 to 0.83 for simulated Sentinel-3 OLCI data choosing Oa10 and Oa8 bands instead of Oa11 and Oa8.
Repeated campaigns are planned during spring and summer blooms 2016 in the Gulf of Riga to get larger data set for validation and evaluate repeatability. The main challenges remain to acquire as good data as possible within rapidly changing environment and often cloudy weather conditions.
Land cover mapping in Latvia is performed as part of the Corine Land Cover (CLC) initiative every six years. The advantage of CLC is the creation of a standardized nomenclature and mapping protocol comparable across all European countries, thereby making it a valuable information source at the European level. However, low spatial resolution and accuracy, infrequent updates and expensive manual production has limited its use at the national level. As of now, there is no remote sensing based high resolution land cover and land use services designed specifically for Latvia which would account for the country’s natural and land use specifics and end-user interests. The European Space Agency launched the Sentinel-2 satellite in 2015 aiming to provide continuity of free high resolution multispectral satellite data thereby presenting an opportunity to develop and adapted land cover and land use algorithm which accounts for national enduser needs.
In this study, land cover mapping scheme according to national end-user needs was developed and tested in two pilot territories (Cesis and Burtnieki). Hyperspectral airborne data covering spectral range 400-2500 nm was acquired in summer 2015 using Airborne Surveillance and Environmental Monitoring System (ARSENAL). The gathered data was tested for land cover classification of seven general classes (urban/artificial, bare, forest, shrubland, agricultural/grassland, wetlands, water) and sub-classes specific for Latvia as well as simulation of Sentinel-2 satellite data. Hyperspectral data sets consist of 122 spectral bands in visible to near infrared spectral range (356-950 nm) and 100 bands in short wave infrared (950-2500 nm). Classification of land cover was tested separately for each sensor data and fused cross-sensor data. The best overall classification accuracy 84.2% and satisfactory classification accuracy (more than 80%) for 9 of 13 classes was obtained using Support Vector Machine (SVM) classifier with 109 band hyperspectral data. Grassland and agriculture land demonstrated lowest classification accuracy in pixel based approach, but result significantly improved by looking at agriculture polygons registered in Rural Support Service data as objects. The test of simulated Sentinel-2 bands for land cover mapping using SVM classifier showed 82.8% overall accuracy and satisfactory separation of 7 classes. SVM provided highest overall accuracy 84.2% in comparison to 75.9% for k-Nearest Neighbor and 79.2% Linear Discriminant Analysis classifiers.
We highlight the options available for noninvasive optical diagnostics of reporter gene expression in mouse tibialis cranialis muscle. An in vivo multispectral imaging technique combined with fluorescence spectroscopy point measurements has been used for the transcutaneous detection of enhanced green fluorescent protein (EGFP) expression, providing information on location and duration of EGFP expression and allowing quantification of EGFP expression levels. For EGFP coding plasmid (pEGFP-Nuc Vector, 10 μg/50 ml) transfection, we used electroporation or ultrasound enhanced microbubble cavitation [sonoporation (SP)]. The transcutaneous EGFP fluorescence in live mice was monitored over a period of one year using the described parameters: area of EGFP positive fibers, integral intensity, and mean intensity of EGFP fluorescence. The most efficient transfection of EGFP coding plasmid was achieved, when one high voltage and four low voltage electric pulses were applied. This protocol resulted in the highest short-term and long-term EGFP expression. Other electric pulse protocols as well as SP resulted in lower fluorescence intensities of EGFP in the transfected area. We conclude that noninvasive multispectral imaging technique combined with fluorescence spectroscopy point measurements is a suitable method to estimate the dynamics and efficiency of reporter gene transfection in vivo.
Airborne hyperspectral imaging is widely used for remote sensing of environment. The choice of spectral region usually depends on the availability and cost of the sensor. Visible-to-near infrared (400-1100 nm) spectral range corresponds to spectral sensitivity of relatively cheap Si detectors therefore it is the most commonly used. The implementation of shortwave infrared (1100-3000 nm) requires more expensive solutions, but can provide valuable information about the composition of the substance. Mid wave infrared (3000-8000 nm) is rarely used for civilian applications, but it provides information on the thermal emission of materials. The fusion of different sensors allows spectral analysis of a wider spectral range combining and improving already existing algorithms for the analysis of chemical content and classification. Here we introduce our Airborne Surveillance and Environmental Monitoring System (ARSENAL) that was developed by fusing seven sensors. The first test results from the fusion of three hyperspectral imaging sensors in the visible-to-mid wave infrared (365-5000 nm) are demonstrated. Principal component analysis (PCA) is applied to test correlation between principal components (PCs) and common vegetation indices.
Assessment of skin blood flow is of interest for evaluation of skin viability as well as for reflection of the overall condition of the circulatory system. Laser Doppler perfusion imaging (LDPI) and laser speckle contrast imaging (LASCI) are optical techniques used for assessment of skin perfusion. However, these systems are still too expensive and bulky to be widely available. Implementation of such techniques as connection kits for mobile phones have a potential for primary diagnostics. In this work we demonstrate simple and low cost LASCI connection kit for mobile phone and its comparison to laser Doppler perfusion imager. Post-occlusive hyperemia and local thermal hyperemia tests are used to compare both techniques and to demonstrate the potential of LASCI device.
Electroporation and ultrasound induced sonoporation has been showed to induce plasmid DNA transfection to the mice tibialis cranialis muscle. It offers new prospects for gene therapy and cancer treatment. However, numerous experimental data are still needed to deliver the plausible explanation of the mechanisms governing DNA electro- or sono-transfection, as well as to provide the updates on transfection protocols for transfection efficiency increase. In this study we aimed to apply non-invasive optical diagnostic methods for the real time evaluation of GFP transfection levels at the reduced costs for experimental apparatus and animal consumption. Our experimental set-up allowed monitoring of GFP levels in live mice tibialis cranialis muscle and provided the parameters for DNA transfection efficiency determination.
Laser speckle contrast analysis (LASCA) offers a non-contact, full-field, and real-time mapping of capillary blood flow and can be considered as an alternative method to Laser Doppler perfusion imaging. LASCA technique has been implemented in several commercial instruments. However, these systems are still too expensive and bulky to be widely available. Several optical techniques have found new implementations as connection kits for mobile phones thus offering low cost screening devices.
In this work we demonstrate simple implementation of LASCA imaging technique as connection kit for mobile phone for primary low-cost assessment of skin blood flow. Stabilized 650 nm and 532 nm laser diode modules were used for LASCA illumination. Dual wavelength illumination could provide additional information about skin hemoglobin and oxygenation level.
The proposed approach was tested for arterial occlusion and heat test. Besides, blood flow maps of injured and provoked skin were demonstrated.
The diffuse reflectance multispectral imaging technique has been used for distant mapping of in vivo skin chromophores (hemoglobin and melanin). The fluorescence multispectral imaging is not so common for skin applications due to complicity of data acquisition and processing, but could provide additional information about skin fluorophores. Both techniques are compatible, and could be combined into a multimodal solution.
The multispectral imaging system Nuance based on liquid crystal tunable filters was adapted for diffuse reflectance and fluorescence spectral imaging of in vivo skin. Uniform illumination was achieved by LED ring light. Combination of four LEDs (warm white, 770 nm, 830 nm and 890 nm) was used to support diffuse reflectance mode in spectral range 450-950 nm. 405 nm LEDs were used for excitation of skin autofluorescence. Multispectral imaging system was adapted for spectral working range of 450-950 nm with scanning step of 10 nm and spectral resolution of 15 nm. An average field of view was 50x35 mm in size with spatial resolution 0,05 mm (the pixel size). Due to spectrally different illumination intensity and system sensitivity, various exposure times (from 7…500 ms) were used for each image acquisition.
The proposed approach was tested for different skin lesions: benign nevus, hemangioma, basalioma and halo nevus. Spectral image cubes of different skin lesions were acquired and analyzed to test its diagnostic potential.
A prototype low-cost RGB imaging system consisting of a commercial RGB CMOS sensor, RGB light-emitting diode ring light illuminator, and a set of polarizers was designed and tested for mapping the skin erythema index, in order to monitor skin recovery after phototherapy of vascular lesions, such as hemangiomas and telangiectasias. The contrast of erythema index (CEI) was proposed as a parameter for quantitative characterization of vascular lesions. Skin recovery was characterized as a decrease of the CEI value relative to the value before the treatment. This approach was clinically validated by examining 31 vascular lesions before and after phototherapy.
The effect of ultrasound exposure on bleomycin fluorescence and pharmacological properties is studied. Bleomycin was treated by ultrasound for 7 min. Bleomycin fluorescence was measured during ultrasound exposure by means of fiber-optic spectrometry. Cell colony test was used to evaluate blemycin cytotoxity before and after ultrasound exposure.
KEYWORDS: Green fluorescent protein, Luminescence, RGB color model, In vivo imaging, Imaging systems, Imaging devices, Proteins, Skin, Ultrasonography, Cameras
Simple RGB method for fluorescence in vivo imaging is presented to assess efficiency of electroporation and sonoporation methods by measuring distribution and accumulation of green fluorescence protein (GFP) concentration. 20 laboratory measurements were performed on mice to test the method.
Non-invasive and fast primary diagnostics of pigmented skin lesions is required due to frequent incidence of skin cancer – melanoma. Diagnostic potential of principal component analysis (PCA) for distant skin melanoma recognition is discussed. Processing of the measured clinical multi-spectral images (31 melanomas and 94 nonmalignant pigmented lesions) in the wavelength range of 450-950 nm by means of PCA resulted in 87 % sensitivity and 78 % specificity for separation between malignant melanomas and pigmented nevi.
Diagnostic potential of principal component analysis (PCA) of multi-spectral imaging data in the wavelength range 450- 950 nm for distant skin melanoma recognition is discussed. Processing of the measured clinical data by means of PCA resulted in clear separation between malignant melanomas and pigmented nevi.
Laser speckle contrast analysis (LASCA) offers a non-contact, full-field, and real-time mapping of capillary blood flow
and can be considered as an alternative method to Laser Doppler perfusion imaging (LDPI). Photoplethysmography
(PPG) is well known technique for assessment of skin blood pulsations that can be related to blood flow. In recent years
several studies have been done on development of non-contact PPG imaging (PPGI).
LASCA and PPGI techniques are simpler and cheaper compared with LDPI. LASCA technique has been implemented in
several commercial instruments. However, these systems are still too expensive and bulky to be widely available.
Several optical techniques have found new implementations as connection kits for mobile phones thus offering low cost
screening device.
In this work we demonstrate simple implementation of LASCA and PPG imaging technique for primary low-cost
assessment of skin blood flow. Both devices comprise a widely available 1.3 mega pixel CMOS camera. Stabilized 650
nm laser diode module is used for LASCA illumination, and white LEDs are illuminators for PPG imaging device.
An arterial occlusion test was performed to test LASCA and PPGI imaging devices. An example of scratch color image
and corresponding blood flow map also was demonstrated. The results showed that both techniques can be used for fast
monitoring and mapping of skin blood flow and implemented as connection kits for smartphone.
Possibilities to determine chromophore distribution in skin by spectral imaging were explored. Simple RGB sensor devices were used for image acquisition. Totally 200 images of 40 different bruises of 20 people were obtained in order to map chromophores bilirubin and haemoglobin. Possibilities to detect water in vitro and in vivo were estimated by using silicon photodetectors and narrow band LEDs. The results show that it is possible to obtain bilirubin and haemoglobin distribution maps and observe changes of chromophore parameter values over time by using a simple RGB imaging device. Water in vitro was detected by using differences in absorption at 450 nm and 950 nm, and 650 nm and 950 nm.
A prototype RGB imaging system for mapping of skin chromophores consists of a commercial RGB CMOS sensor,
RGB LEDs ring-light illuminator and orthogonally orientated polarizers for reducing specular reflectance. The system
was used for monitoring of vascular malformations (hemagiomas and telangiectasias) therapy.
Influence of low power laser irradiance on healthy skin using diffuse reflectance spectroscopy and multispectral
imaging was studied. Changes of diffuse reflectance spectra in spectral range from 500 to 600 nm were observed after
405 nm, 473 nm and 532 nm laser provocation, leading to conclusion that the content of skin hemoglobin has changed.
Peaks in spectral absorbance (optical density) curves corresponded to well-known oxy-hemoglobin absorbance peaks at
542 and 577 nm.
There are a number of techniques for body composition assessment in clinics and in field-surveys, but in all cases the
applied methods have advantages and disadvantages. High precision imaging methods are available, though expensive
and non-portable, however, the methods devised for the mass population, often suffer from the lack of precision.
Therefore, the development of a safe, mobile, non-invasive, optical method that would be easy to perform, precise and
low-cost, but also would offer an accurate assessment of subcutaneous adipose tissue (SAT) both in lean and in obese
persons is required. Thereof, the diffuse optical spectroscopy is advantageous over the aforementioned techniques.
A prototype device using an optical method for measurement of the SAT thickness in vivo has been developed. The
probe contained multiple LEDs (660nm) distributed at various distances from the photo-detector which allow different
light penetration depths into the subcutaneous tissue.
The differences of the reflected light intensities were used to create a non-linear model, and the computed values were
compared with the corresponding thicknesses of SAT, assessed by B-mode ultrasonography.
The results show that with the optical system used in this study, accurate results of different SAT thicknesses can be
obtained, and imply a further potential for development of multispectral optical system to observe changes of SAT
thickness as well as to determine the percentage of total body fat.
Skin assessment technology based on comparative analysis of single-pixel RGB signal values at poly-chromatic
illumination has been proposed. Multi-spectral imaging information from a single snapshot RGB image data set with the
inter-channel crosstalk correction can be extracted this way. Proof-of-concept evaluations and measurement results are
presented and discussed. Potential of bi-chromatic illumination for skin hemoglobin mapping during arterial occlusion
test has been demonstrated.
A prototype R-G-B imaging system for mapping of skin hemoglobin distribution has been designed and tested. Device
basically consists of a commercial RGB sensor (CMOS, max. frame rate 87 fps for VGA resolution), RGB LED ringlight
illuminator and orthogonally orientated polarizers for reducing specular reflectance. The system was examined for
monitoring of hemoglobin concentration changes during specific provocations - arterial/venous occlusions and heat test.
Hemoglobin distribution maps of several skin malformations were obtained, as well.
An experimental RGB imaging system based on commercial color camera was constructed, and its potential for mapping
of hemoglobin distribution in skin was studied. Two types of LEDs (RGB and white "warm" LEDs) were compared as
illuminators for acquiring images of vascular and pigmented skin malformations. A novel approach for studies of skin
capillary refill by RGB analysis has been proposed and discussed.
A clinical trial comprising 334 pigmented and vascular lesions has been performed in three Riga clinics by means of multispectral imaging analysis. The imaging system Nuance 2.4 (CRi) and self-developed software for mapping of the main skin chromophores were used. Specific features were observed and analyzed for malignant skin melanomas: notably higher absorbance (especially as the difference of optical density relative to the healthy skin), uneven chromophore distribution over the lesion area, and the possibility to select the "melanoma areas" in the correlation graphs of chromophores. The obtained results indicate clinical potential of this technology for noncontact selection of melanoma from other pigmented and vascular skin lesions.
A clinical trial comprising 266 pigmented lesions and 49 vascular lesions has been performed in three Riga clinics by
means of multi-spectral imaging analysis. The imaging system Nuance 2.4 (CRI) and self-developed software for
mapping of the main skin chromophores were used. The obtained results confirm clinical potential of this technology for
non-contact quantitative assessment of skin pathologies.
The paper investigates influence and efficacy of laser therapy on pigmented and vascular cutaneous malformations by
multispectral imaging technique. Parameter mapping of skin pigmented and vascular lesions and monitoring of the laser
therapy efficacy are performed by multispectral imaging in wavelength range 450-700nm by scanning step - 10nm.
Parameter maps of the oxyhemoglobin deoxyhemoglobin and melanin derived from the images are presented. Possibility
of laser therapy efficacy monitoring by comparison of the parameter maps before and after laser treatment has been
demonstrated. As both cutaneous pigmented and vascular malformations are commonly found lesions, the parameter
mapping would be a valuable method to use routinely.
In-vivo skin photo-bleaching (intensity decrease during irradiation) has been investigated at 405 nm cw laser excitation.
Digital RGB photo-camera was used for studies of the bleaching features by analysis of fluorescent images at separated
R, G and B spectral bands. Diagnostic potential based on correlations between skin pigmentation and bleaching rates is
discussed.
KEYWORDS: Skin, Chromophores, In vivo imaging, Absorption, Superposition, Associative arrays, Ultraviolet radiation, Chemical analysis, Image processing, Signal processing
The multi-spectral imaging technique has been used for distant mapping of in-vivo skin chromophores by analyzing
spectral data at each reflected image pixel and constructing 2-D maps of the relative concentrations of oxy-/deoxyhemoglobin
and melanin. Instead of using a broad visible-NIR spectral range, this study focuses on narrowed spectral
band 500-700 nm, so speeding-up the signal processing procedure. Regression analysis confirmed that superposition of
three Gaussians is optimal analytic approximation for the
oxy-hemoglobin absorption tabular spectrum in this spectral
band, while superposition of two Gaussians fits well for
deoxy-hemoglobin absorption and exponential function - for
melanin absorption. The proposed approach was clinically tested for three types of in-vivo skin provocations - ultraviolet
irradiance, chemical reaction with vinegar essence and finger arterial occlusion. Spectral range 500-700 nm provided
better sensitivity to oxy-hemoglobin changes and higher response stability to melanin than two reduced ranges 500-600
nm and 530-620 nm.
The possibilities to perform multi-band spectral imaging by means of a consumer color camera without external
filters have been studied. Images at up to 6 spectral bands may be extracted from a single color image after
appropriate signal processing. The proposed technique was tested in pilot measurements of in-vivo skin hemoglobin
maps and laser-excited autofluorescence images.
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