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This thesis outlines problems in the estimation of concentration value of an absorber present in a medium that is scattering and shortcomings of using the currently available techniques for the characterisation of such a scattering medium. The work describes experiment and analytic techniques used to overcome these problems. This thesis explored ex...
Citations
... With every new value assigned, the attenuation values are recalculated form (6) values are assumed to have been achieved. The E and iteration limit were arbitrarily selected following previous related work [36] who revealed that these values are sufficient for the convergence of the calculated attenuation spectrum, A c , to that of the measured spectrum. An increase in the number of iterations or decrease in the E limit would result in an improved accuracy of the estimated value, although this would inadvertently result in an increased computation time. ...
The high prevalence of the world’s population diagnosed with diabetes mellitus, with a significant number suffering from diabetic foot ulcer (DFU), has always been a global concern over the years. The rapid rise of this disease in the last decades is deemed increasingly alarming as it has left deleterious effects not only on affected patients but also on the society and nation. This paper aims to develop a reliable diagnostic tool to address the tremendous need for coordinated and efficient DFU management via prediction of transcutaneous oxygen saturation (StO2) and relative blood perfusion (τ) in the affected limb. This system integrates the use of a multispectral imaging and laser speckle contrast imaging technique for two-dimensional (2D) mapping of tissue oxygen and blood perfusion level in ulcerated foot. Longitudinal study revealed a slightly higher mean StO2 and τ level in healed ulcer than in impaired healing, despite the data indicating no statistical significance between these two groups (p – value > 0.05). It was observed that a mean StO2 of at least 70 % and τ value of 1.5 (!Q103) are necessary during the proliferative phase to ensure progressive healing. Based on these findings, this study concluded that high tissue oxygenation and perfusion levels are pivotal to ensure progressive wound healing. This work provides a rationale for evaluating the healing outcomes of skin grafting procedures in diabetic ulcers based on observation of quantitative changes in blood perfusion and tissue oxygen level during its revascularization phase.
... Where, (X , Y ) are the spatial pixel coordinates, (ω) is the spectral coordinate (wavelength), Ĩ t (X , Y , ω) is the HS image of the complete forehand subject, b(X , Y , ω) is the HS image of the ROI to highlight the oxygenated arteries and de-oxygenated veins, Ĩ c (X , Y , ω) is the reference HS image. The expectation of the essential health parameter quantity is through the wavelength (ω), dependent light diffusion calculation model defined in equation (4) [35]: ...
Significance
The estimation of tissue oxygenation is vital in the diagnosis and therapeutic evaluation of a huge assortment of diseases. However, the hyperspectral (HS) imaging system is a rising innovation that can be utilized to build a highly sensitive, non-invasive, and tissue hemoglobin immersion map.
Objective
As a result of the urgent need to design and implement early detection devices and applications for the COVID-19 pandemic, we propose building a non-invasive custom optical imaging system to assist with phlebotomy and vascular approach to survey the reliability of blood oxygen saturation (SpO2) levels recovered from spectral images.
Materials and Methods
HS images were gathered from 15 healthy subjects without previous medical history complications and with an average age range of 20 to 38 years, who were undergoing phlebotomy. The forearm was vigorously illuminated utilizing an HS camera with polychromatic source light of spectrum range (400∼980 nm). Spectroscopic reflectance images were caught by a focal plane exhibit for the region of interest (ROI). Then the custom algorithm comprising normalization and moving average filtering for noise removal was applied, followed by K-mean clustering for image segmentation to visualize and highlight the arteries and the veins in the investigated forearm.
Results
The investigations show that after normalization of the recorded signal from the HS camera of the participating subjects it was noticed that at wavelength of 460 nm the oxygenated arteries had a stronger signal than the de-oxygenated veins, and at a wavelength of 750 nm the de-oxygenated veins had a stronger signal than the oxygenated arteries. Thus, the ideal wavelength to reveal the oxygenated arteries was 460 nm, and the ideal wavelength to reveal the de-oxygenated veins was 750 nm.
Conclusions
HSI is a prospective technique to assist with phlebotomy and non-contact oxygen saturation approach. Additionally, it may permit future surgical or pharmacological intercessions that titrate or limit ischemic injury continuously.
... The Monte Carlo (MC) simulation model [20] was used here for the investigation work due to its known blood oxygen saturation value in the medium. The simulation results from this MC model was previously shown to be in good agreement with experimental data of absorbing-scattering phantom media (refer to [21] for the details). In this study, human skin was modeled as a two-layered medium with homogeneously distributed scattering and absorbing centers: the upper layer was an infinite slab of thickness 100 µm superimposed on a semi-infinite bottom layer. ...
... Even though the use of this proposed approach is feasible for real time system implementation with average processing time of 1.1 ms, this is at the price of poorer performance stability. By increasing the complexity of the analytic model, for example through the adequate representation of non-linear µ a and light attenuation relationship [20][21][22][23][24][25], the accuracy of the prediction could be improved. Such system, however, requires the use of a more advanced processing strategy involving more light wavelength bands, placing a higher demand on the processing power. ...
p> This paper presented the use of a three-wavelength system coupled with a prediction-correction model for the measurement of a person’s tissue oxygen levels and in the efforts towards the development of a field-portable system. This study considered light wavelength of market-available emitters in the range 500 − 650 nm for its practical implementation. This approach required the use of light attenuation and hemoglobin absorptivity information of three different wavelengths in determining tissue oxygen saturation value, StO2. It was found through the analysis of results using Monte Carlo method that considerable improvement in the accuracy of the predictions was obtained using the corrective models (ρ =0.874). The low mean prediction errors of similar magnitude, not exceeding 4 %, given by two wavelength combinations 538, 560, 633 nm and 538, 560, 650 nm were observed for signals with signal-noise ratio (SNR) of down to 30 dB. A significant statistical difference was found between the prediction errors and the wavelength combination used under this noise condition (ρ =0.011). This work concluded that the findings of this study provide insights into technology implementation of skin oximetry and the possible impacts it might have in medical arena. </p
... In comparison to its counterparts namely frequency-domain and time-domain measurement techniques, this technique is relatively simpler. This system is often integrated with polarizer system to reduce scattering effects in the detected light [21]. The multidisciplinary applications of hyperspectral imaging system range from agricultural and food processing [22], remote sensing to pharmaceutical and medical image processing [23,24]. ...
... In comparison to its counterparts namely frequency-domain and time-domain measurement techniques, this technique is relatively simpler. This system is often integrated with polarizer system to reduce scattering effects in the detected light [21]. The multidisciplinary applications of hyperspectral imaging system range from agricultural and food processing [22], remote sensing to pharmaceutical and medical image processing [23,24]. ...
... This model was later being expanded into Extended Modified Lambert Beer Law by Huong and Ngu [15] to allow a more accurate prediction of the SO2 and percent carbon monoxide (CO) in the blood system. Other analytical models include the cumulant based attenuation model [17], Kubelka Munk theory [18], Kramer's rule [19], Monte Carlo model [20] and cubic model [21]. Even though most of the aforementioned models were adopted to predict blood SO2, Kramer's rule [16] was designed to predict Cbil using a lookup table. ...
Noninvasive measurement of health parameters such as blood oxygen saturation and bilirubin concentration predicted via an appropriate light reflectance model based on the measured optical signals is of eminent interest in biomedical research. This is to replace the use of conventional invasive blood sampling approach. This study aims to investigate the feasibility of using Modified Lambert Beer model (MLB) in the prediction of one’s bilirubin concentration and blood oxygen saturation value, SO2. This quantification technique is based on a priori knowledge of extinction coefficients of bilirubin and hemoglobin derivatives in the wavelength range of 440 – 500 nm. The validity of the prediction was evaluated using light reflectance data from TracePro raytracing software for a single-layered skin model with varying bilirubin concentration. The results revealed some promising trends in the estimated bilirubin concentration with mean ± standard deviation (SD) error of 0.255 ± 0.025 g/l. Meanwhile, a remarkable low mean ± SD error of 9.11 ± 2.48 % was found for the predicted SO2 value. It was concluded that these errors are likely due to the insufficiency of the MLB at describing changes in the light attenuation with the underlying light absorption processes. In addition, this study also suggested the use of a linear regression model deduced from this work for an improved prediction of the required health parameter values.
... An algorithm was written in MATLAB to calculate the light attenuation of each wavelength given by: = log ( ) (2) where Is is the light intensity reflected from the palm of the hand while Iw is the light intensity reflected from the surface of a white reference sheet. The prediction of the required health parameter value is via the wavelength, λ, dependent light diffusion approximation model defined as followed [6]: ...
This paper presents the use of the developed spectroscopic system for noncontact measurement of one's skin blood oxygen saturation (StO2). This study employed light diffusion model in the prediction of the required value using light source of wavelength 488 nm, 522 nm and 684 nm. The performance of this system was tested on ten volunteers of different skin tone to investigate the robustness of the system. The mean and standard deviation of StO2 value calculated for the recruited subjects is given by 71 ± 4.7 %. The results revealed differences in the predicted value with the recruits' skin tone. This work concluded that the developed system may potentially be used in clinical settings to determine skin oxygen saturation and to monitor wound healing progress.
... This is followed by mean StO2 of 84.8 0.9% for detection distance of 50 mm. These values are comparable to that observed in the works of previous researchers who used different analytical model namely Kubelka Munk [14] and Cumulant based forward model (CM) [15,16]. The results in Table 1 and Figure 3 also revealed small standard deviation among these subjects, indicating good repeatability of the analytical technique and the proposed experimental method when the imaged skin site is of close proximity to the detection system (<50 mm). ...
This paper aims to investigate the variation in one's percent mean transcutaneous oxygen saturation (StO2) with differences in spatial resolution of data. This work required the knowledge of extinction coefficient of hemoglobin derivatives in the wavelength range of 520 – 600 nm to solve for the StO2 value via an iterative fitting procedure. A pilot study was conducted on three healthy subjects with spectroscopic data collected from their right index finger at different arbitrarily selected distances. The StO2 value estimated by Extended Modified Lambert Beer (EMLB) model revealed a higher mean StO2 of 91.1 ± 1.3% at a proximity distance of 30 mm compared to 60.83 ± 2.8% at 200 mm. The results showed a high correlation between data spatial resolution and StO2 value, and revealed a decrease in StO2 value as the sampling distance increased. The preliminary findings from this study contribute to the knowledge of the appropriate distance range for consistent and high repeatability measurement of skin oxygenation.
... papillary dermal and deep dermal layers) would lose their polarization memory, whereas weakly scattered photons backscattered from thin epidermal layer preserve their polarization information. Previous works [1] showed a relatively linear relationship between the weakly polarized light attenuation value and the microcirculatory activities dependent medium's absorption, allowing interpretation of the latter using the linear Lambert Beer function. This eliminated the necessity of finding either the optimum wavelengths [2] or suitable analytical model [3] in the analysis of spectroscopic data. ...
... Categories of light detected from different polarization mode[1] ...
This study demonstrates the use of a polarized optical system for localized imaging of superficial tissue while removing multiple scattered lights by means of polarization gating. This study performed co-circular and cross-linear polarization experiments on the palm of the hand of thirteen Asian volunteers at resting and during arterial blood occlusion condition for the demonstration work. These co-circular and cross-linear polarized images were mathematically subtracted to remove the deeper backscattered lights. The resultant images were then processed using an algorithm written in MATLAB to calculate changes in the ratio of the color information of the polarization maintaining images, βGB, with different experimental condition. The results revealed an overall lower unitless βGB value of 1.12 ± 0.35 calculated for blood occlusion case compared to 1.73 ± 0.48 for at rest condition. The paired student's t-test revealed a strong correlation between βGB and the employed experimental methods that were hypothesized to modify one's blood oxygen level. This work has concluded that the developed system can potentially be used as an alternative means for noncontact localized imaging of superficial skin microcirculatory activities and may be used for wound evaluation and skin condition assessment.
... This work assumed light absorption by Carboxyhemoglobin (COHb) and Methemoglobin (MetHb) are negligible, the absorption coefficient of blood, µa(Hb), at wavelength, λ, is given by the absorptivity of oxyhemoglobin (OxyHb), µa(OxyHb), and deoxyhemoglobin (dHb), µa(dHb), as followed [10]: ...
... The main source of light scattering in the modeled skin was by the adipose layer that comprised of intralipid tissue. The wavelength dependent reduced scattering coefficient, µꞌs(λ), for intralipid-10% in the units of cm -1 is given by [10]: ...
... It was assumed that with the medium thickness, d, of 150 mm none of the photons can escape from the medium without being scattered and absorbed. Further discussion of the Monte Carlo model can be found in [10]. ...
An empirical technique that allows noninvasive prediction of skin (transcutaneous) oxygen saturation (StO2) using the absorption coefficients of the preprocessing stored wavelength pairs is proposed. The highest probable StO2 value is decided by selecting the bin containing wavelength pairs that produce the smallest variation in the distribution of the calculated attenuation gradient value. The performance this technique was evaluated using Monte Carlo simulated data. The simulation results revealed that this technique worked reasonably well even at low StO2 condition with an overall mean error of not more than 2 %. This shows that the proposed analytic technique can potentially be used for measurement of the blood oxygen level of individuals with respiratory disease or with oxygen deprivation conditions such as hypoxic-hypoxia.
