Detection of Signal Parameters and Backscattering Polarimetric Imaging Signatures Using Molecular Optical Contrast Agents and Preclinical Liquid Phantoms PDF Download

Author: Vandana Adya
Publisher:
ISBN:
Category : Biomedical engineering
Languages : en
Pages : 93

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Book Description
"The main purpose of this study is to explore the potential of optically active molecules in conjunction with single pixel detectors and polarimetric techniques for early detection of tissue pathologies. Optical polarimetry can provide invaluable biological information based on molecular composition of the medium, structure, geometry, and metabolism. The preclinical phantom used was a rectangular plexiglass container and the experiments were carried out under backscattering detection geometry. A NIRVANA (Newfocus Inc., Model 2007, Santa Clara, CA, USA) auto balance detector was employed throughout the study. Initial readings were taken with water, and then aqueous solution of optically active molecules was added into it. The readings were obtained for the two states of polarization of light, parallel and perpendicular polarization. The signal-to-noise ratio and detective quantum efficiency (DQE) were calculated. The outcome of this study indicated an increase of the backscattered detected signal, signal-to-noise ratio, and the DQE of the imaging system, with increase in the concentration of optically active contrast agents. The results obtained were validated by performing linear regression analysis and paired t-test. The statistical analysis indicated increase in backscattered detected signal, signal to noise ratio, DQE and significant difference between the two states of polarization. This increase in the backscattered signal due to difference in the refractive index between the background and the object, leads to an increased contrast image that would assist in the early detection of tumor, other tissue pathologies, and biological structures."--Abstract.

Author: Sriram Atreya Paturi
Publisher:
ISBN:
Category : Biology
Languages : en
Pages : 97

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Book Description
The main purpose of this study was to explore the potential of optical active molecules as biomolecular photonic contrast agents in increasing the image contrast of biological structures in conjunction with optical polarimetric techniques using a preclinical phantom. The outcome of this study may contribute to enhanced detection of early diseases and pathologies in tissue. In this study, a preclinical phantom was designed and experiments were performed using a backscattered polarimetric imaging system. By using the principles of a rotating retarder polarimeter and data reduction algorithm based on polarimetric measurement matrix, Stokes parameters were calculated and finally the Degree of Linear Polarization (DOLP) images were calculated. The obtained S0 and DOLP images were fused to obtain an enhanced image which offers a high contrast resolution. This step was repeated for each concentration of optically active molecular contrast agents added to the preclinical phantom. The signal-to-noise ratio (SNR), signal-to-background ratio (SBR) and the number of pixels detected as edges were calculated to determine the image quality.The outcome of this study indicates clearly an increase in image quality parameters with increase in concentration of contrast agents like isopropyl alcohol, sugar solution and salt solution, to the preclinical phantom. It also indicates that the DOLP and fused images provide unsurpassable image quality with respect to S0 images highlighting the fact that the polarized light measurements yield a better output than the total intensity measurements. Overall, this optical polarimetric system in conjunction with the contrast agents can contribute to an effective imaging system for enhanced imaging characteristics and early tumor or tissue pathologies detection.

Author: Keerthi Srivastav Valluru
Publisher:
ISBN:
Category : Biology
Languages : en
Pages : 91

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The purpose of this research study is to explore novel imaging methodologies using advanced polarimetric principles in conjunction with molecular contrast agents and biomarkers for early detection of tissue abnormalities. The novelty of this work consists in the use of optically active polar molecules, proteins and enzymes as innovative biomolecular contrast agents to extract biochemical and structural information contained within the optical signatures emitted by the tissue upon light interrogation. A preclinical phantom with multiple refractive-index variations was designed for the study and the experiments were conducted in two phases. The first phase of experiments was performed using a Near-Infrared (NIR) Laser source by combining Rotating Retarder Polarimeter Method and Polarimetric Measurement Matrix reduction techniques. L-Phenylalanine and Insulin Glargine were chosen as molecular contrast agents for this study. The resulting Degree of Linear Polarization (DOLP) images were analyzed for contrast differences and the image quality was assessed by computing Signal-to-Background Ratios (SBRs) for every concentration of molecular contrast agent added to the surrounding medium of the target.The second phase of experiments involved a broadband visible light source (655nm) and a microscopic objective lens system to interrogate the target utilizing Polarization Discrimination Methodologies. Isopropyl Alcohol, Glucose solution and Insulin Glargine were chosen as the molecular contrast agents for this study. The resulting co-polarized and cross-polarized images were processed to obtain DOLP images which were subsequently analyzed for contrast variations for every concentration of molecular contrast agent added. The quality of images obtained was assessed by implementing edge detection techniques on the DOLP images and tracing the changes in number of pixels detected as edges for varying concentrations of molecular contrast agents. Experimental results from both the studies indicate clearly that the molecular contrast agents used in this study were successful in improving the image contrast of the DOLP images obtained through (NIR) polarimetric imaging as well as broadband visible light polarimetric imaging techniques. Specifically, the results of this study indicate that the DOLP images were more sensitive to the variations in concentrations of the molecular contrast agents added to the surrounding medium of target compared to nonpolarimetric (S0) images, leading to a net enhancement of the image contrast. Overall, the contributions of this study suggest that the presented optical principles can be successfully applied to the diagnosis and assessment of cancer in early stages utilizing molecular contrast agents in conjunction to polarimetry concepts.

Author: Kamalakar Ambadipudi
Publisher:
ISBN:
Category : Imaging systems in biology
Languages : en
Pages : 89

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Book Description
"In optical imaging, the high random scattering of light in biological tissue can degrade the contrast of an image which could be a drawback in detection of tumors. Polarization based imaging has shown its capability in overcoming such drawbacks over the recent years. It depends on discrimination of randomly polarized light from weakly polarized light yielding an enhanced image contrast. The purpose of this research study was to investigate, compare and assess the imaging potential of two widely used techniques in the field of polarimetric imaging namely, Linear Polarimeter method (uses linearly polarized light) and Rotating Retarder Polarimeter method (uses circularly polarized light) to interrogate targets embedded in turbid biological media. This novel study may contribute to early detection of diseases and pathologies in biological tissues. The polarization properties of the backscattered light from a turbid medium containing a target submerged in a scattering solution were studied. A preclinical optical phantom was designed and the experiments were done in two phases, each phase corresponding to a different polarimetric technique. Specifically, a polystyrene cylinder was used as the target and the turbid medium was simulated by adding skim milk in volume percentage increments in both the phases. The first phase of experiments involved the Rotating Retarder Polarimeter method and the Polarimetric Measurement Matrix Reduction techniques. The images obtained by this method were processed by iv means of a data reduction algorithm, based on Polarimetric Measurement matrix method to calculate the Degree of Linear Polarization (DOLP) image and total intensity (S0) image. The second phase of experiments involved the Linear Polarimeter method. The resulting co-polarized and cross-polarized images from this method were processed to obtain Degree of Polarization (Rpol) images. Both of these experiments were performed using a backscattered polarimetric imaging system. The images obtained by both the techniques were analyzed by computing signal to background ratio (SBR) values and number of pixels detected as edges for every concentration of skim milk solution added to the surrounding medium of the target. The obtained images were then compared to determine the image quality. Experimental results from both these techniques showed that the DOLP images obtained by the Rotating Retarder Polarimeter method provide better contrast in terms of signal to background ratio (SBR) values and number of pixels detected as edges compared to Degree of Polarization (Rpol) images obtained by the linear Polarimeter method. Overall, the contributions of this study suggest that the interrogation of targets in turbid media using circularly polarized light exhibits superior imaging characteristics with respect to linearly polarized light interrogation."--Abstract.

Author: Praneeth Bathini
Publisher:
ISBN:
Category : Biomedical engineering
Languages : en
Pages : 70

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Book Description
This research study purpose is to design an optical transillumination based system and explore the potential of imaging enhancement, utilizing various contrast agents and polarimetry. This novel design can be used to study the polarimetric image characteristics of an optical phantom which replicates the nature of biological tissue, determining the morphological and metabolic information. Linearly polarized light was used to probe the phantom under test. Subsurface structure of the phantom was detected, with contrast agents like sugar solution, isopropyl alcohol and insulin solution. Co-polarized images provided results to affirm efficacy of the system design and principle adopted. A significant increase in the signal detected was observed with the increased contrast agent concentration, as an outcome of this study. Even under increased scattering conditions, the designed system was superior enough to provide enhanced detection. Polarization difference images have exhibited that the contrast, defined as signal to background ratio, can be augmented by multiple folds in comparison with just co-polarized images. Classification of the materials based on the results would be effective to learn about the embedded tissue structure and its optical characteristics. It would be interesting to apply advanced image processing algorithms that can reveal more information on this data. The whole study gives an additional dimension to optical imaging as significant platform with applications in the medical diagnostic arena.

Author: Suman Shrestha
Publisher:
ISBN:
Category : Electrical engineering
Languages : en
Pages : 131

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Book Description
In the year 2012, there were approximately 226,160 cases of lung cancer and 160,340 deaths out of it as per the National Cancer Institute. There are mainly two types of lung cancer, small cell lung cancer and non-small cell lung cancer, of which 87% are diagnosed as non-small cell. A physical algorithm and a systematic study relating the morphological, chemical and metabolic properties of lung cancer to the physical and optical parameters of the polarimetric detection process are missing. Therefore, one of the purposes of the study is to explore the polarimetric phenomenology of near infrared light interaction with healthy and lung cancer monoline cells by using efficient polarimetric backscattering detection techniques. Preliminary results indicate that enhanced discrimination between healthy and different types of lung cancer cells can be achieved based on their backscattered intensities, Mueller matrix, diattenuation and depolarization properties. Also, various optical parameters like linear depolarization ratio and degree of linear polarization play an important role in discriminating healthy and different lung cancer cells. Specifically, the sizes of the nuclei of the cancer cells and the nucleus-to-cytoplasmic ratios appear to have potential impact on the detected polarimetric signatures leading to enhanced discrimination of lung cancer cells. The second work in this thesis has been done with the support of the Air Force Research Laboratory (AFRL). Polarimetric signals have always played an important role in the identification, discrimination and analysis of a material's optical properties. This work presents a novel remote sensing approach based on polarimetric fractal detection principles. Backscattered polarimetric signals contribution from different materials used in space applications have already been detected using a laboratory LADAR testbed and this thesis presents implememtation of the LADAR testbed and analysis techniques of these backscattered signals based on fractal analysis. Fractal dimension has been chosen as a measure for the discrimination purposes of these materials. The outcome of this thesis indicates that polarimetric fractal principles may enhance the capabilities of the LADAR for characterization and discrimination of different materials.

Author: Valery V. Tuchin
Publisher: Springer Science & Business Media
ISBN: 3540453210
Category : Science
Languages : en
Pages : 281

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Book Description
Optical Polarization in Biomedical Applications introduces key developments in optical polarization methods for quantitative studies of tissues, while presenting the theory of polarization transfer in a random medium as a basis for the quantitative description of polarized light interaction with tissues. This theory uses the modified transfer equation for Stokes parameters and predicts the polarization structure of multiple scattered optical fields. The backscattering polarization matrices (Jones matrix and Mueller matrix) important for noninvasive medical diagnostic are introduced. The text also describes a number of diagnostic techniques such as CW polarization imaging and spectroscopy, polarization microscopy and cytometry. As a new tool for medical diagnosis, optical coherent polarization tomography is analyzed. The monograph also covers a range of biomedical applications, among them cataract and glaucoma diagnostics, glucose sensing, and the detection of bacteria.

Author: Srinivasan Sukumar
Publisher:
ISBN:
Category : Diagnostic imaging
Languages : en
Pages : 0

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Book Description
"The purpose of this research was to investigate the potential of a laser-based optical polarimetric imaging system, operating under light backscattering geometry, for tumor detection utilizing an optical tumor phantom. Image plays a key role in tumor detection studies. The polarization state of the scattered light from a tumor-like structure and the discrimination of randomly polarized light from weakly polarized light can provide meaningful information regarding the nature of the tumor itself. This information can be both physiological and structural. In this research study, experiments were performed at two optical wavelengths, one visible and one near-infrared wavelength. The weakly scattered light from the tumor tissue like phantom had the necessary information relevant to the structure of the tumor. A Rotating Retarder Polarimeter was used to analyze this weakly scattered light from the phantom. The images obtained from the Rotating Retarder Polarimeter were then processed by means of a data reduction algorithm, based on Polarimetric Measurement matrix method to calculate the Degree of Linear Polarization (DOLP) image. Then, the DOLP images obtained from the two different wavelength lasers were subtracted to enhance the information present in the image. The Signal-to-Background ratio, a measure of contrast, was calculated to determine the quality of the image. Results from the experiments and the contrast analysis procedures showed that, the subtracted DOLP images provides better contrast in terms of higher numerical value compared to the single DOLP image. Overall, this optical imaging system combined with data reduction algorithm and image processing technique served as an effective imaging methodology in optical tumor phantom study."--Page iii-iv.

Author: Yun-Sheng Chen
Publisher:
ISBN:
Category :
Languages : en
Pages : 370

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Book Description
Molecular imaging is an emerging imaging principle which can visually represent the biological processes both spatially and temporally down to the sub-cellular level in vivo. The outcome of this research is expected to have a profound impact on facilitating the early diagnosis of diseases, accelerating the development of new drugs, and improving the efficacy of therapy. In general, molecular imaging highly relies on probes to sense the occurrence of molecular biological events, and to generate signals which could be picked up by diagnostic imaging modalities. The advances in the design of molecular probes not only have equipped traditional anatomical medical imaging with new capabilities but also, in some cases, stimulated developments of new imaging modalities and renaissance of existing medical imaging modalities. One of these is photoacoustic imaging, which as an emerging medical imaging modality, unites the merits from both optical imaging and ultrasound imaging. It shares with optical imaging, that it uses non-ionizing radiation and provides higher contrast and higher sensitivity than ultrasound imaging. Unlike optical imaging, which requires ballistic photons for imaging, photoacoustic imaging requires only diffusive photons to excite the ultrasound signal from the imaging target; therefore, it is capable of imaging much deeper into the tissue. In combination with molecular probes, photoacoustic molecular imaging has been demonstrated by several research groups using various photoacoustic molecular probes. However, the molecular probes used for most of these studies were contrast agents simply adopted from other optical imaging modalities. Our research on photoacoustic contrast agents indicated that the mechanism of photoacoustic signal generation from nanometer-sized contrast agents is distinct from that of optically homogeneous materials, such as tissue. We have discovered that, the amplitude of the photoacoustic signal generated from nano-contrast agents depends not only on the optical absorption of the particles, but more importantly, on the dynamic process of the heat conduction from the nanoparticles to the ambient, and the thermal properties of the surrounding materials. Based on our finding, we explored and further improved the photoacoustic response of the nanoparticles by exploiting the heat conduction process between the nanoparticle and its surrounding materials and by manipulating the excitations. This research allows to create optimized molecular specific contrast enhanced photothermal stable probes which can aid photoacoustic imaging and image guided photothermal cancer therapy.

Author: Khushbu Dipak Patel
Publisher:
ISBN:
Category : Diagnostic imaging
Languages : en
Pages : 58

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Book Description
In vivo fluorescence imaging is an emerging technique with potential for usage in non-invasive cancer screening, surveillance, real-time surgical guidance, and staging. Fluorescence imaging uses the interaction of non-ionizing optical radiation with endogenous fluorophores or fluorescent labels to provide real-time wide-field images of tissue structure and/or functional components. When imaging in vivo, excitation light must travel through overlying tissue to reach the fluorescent target and emitted fluorescence must then propagate back through the overlying tissue in order to be imaged onto a camera. Recently, fluorescent contrast agents have been developed with excitation and emission wavelengths in the near infrared (NIR) spectrum (~700 - 1,000 nm) in order to minimize attenuation and maximize the measured signal from tissue. While several clinical trials have shown the potential benefits of NIR contrast agents over visible fluorophores, there may still be room for improvement by moving to even longer wavelengths. As scattering is reduced as wavelength increases, some researchers are investigating fluorophores that emit in the short-wave infrared (SWIR) wavelength region (~1,000 - 2,300 nm). This study focuses on examining optical transmission and image contrast at NIR wavelengths and SWIR wavelengths to determine which wavelength region may be optimal for development of fluorescent contrast agents. Transmission and contrast measurements were performed on both tissue simulating phantoms and real biological tissues using 780 nm, 980 nm, and 1550 nm wavelengths. From the experiments conducted, it appears that fluorophore emissions should be chosen based on the goals of the specific application. For an application that requires simple detection of signal, near infrared wavelengths will be better as they can be detected with higher signal levels. For an application that focuses on imaging fluorophore-labeled tissues, short-wave infrared wavelengths will be the better option as they provided better image contrast.