1. Articles from Evgenia Bousi

    1-12 of 12
    1. Using speckle to measure tissue dispersion in optical coherence tomography

      Using speckle to measure tissue dispersion in optical coherence tomography

      Tissue dispersion could be used as a marker of early disease changes to further improve the diagnostic potential of optical coherence tomography (OCT). However, most methods to measure dispersion, described in the literature, rely on the presence of distinct and strong reflectors and are, therefore, rarely applicable in vivo . A novel technique has been developed which estimates the dispersion-induced resolution degradation from the image speckle and, as such, is applicable in situ . This method was verified experimentally ex vivo and was applied to the classification of a set of normal and cancerous colon OCT images resulting in 96% correct classification.

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    2. Using speckle to measure tissue dispersion in optical coherence tomography

      Using speckle to measure tissue dispersion in optical coherence tomography

      In Optical Coherence tomography (OCT), dispersion mismatches cause degradation of the image resolution. However, dispersion is specific to the material that is causing the effect and can therefore carry useful information regarding the composition of the samples. In this summary, we propose a novel technique for estimating the dispersion in tissue which uses the image speckle to calculate the PSF degradation and is therefore applicable to any tissue and can be implemented in vivo and in situ. A Wiener-type deconvolution algorithm was used to estimate the image PSF degradation from the speckle. The proposed method was verified ex vivo resulting ...

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    3. Lateral resolution improvement of oversampled OCT images using Capon estimation of weighted subvolume contribution

      Lateral resolution improvement of oversampled OCT images using Capon estimation of weighted subvolume contribution

      A novel technique for lateral resolution improvement in optical coherence tomography (OCT) is presented. The proposed method is based on lateral oversampling of the image. The locations and weights of multiple high spatial resolution sub-volumes are calculated using a Capon estimator assuming each contributes a weighted portion to the detected signal. This technique is independent of the delivery optics and the depth of field. Experimental results demonstrate that it is possible to achieve ~4x lateral resolution improvement which can be diagnostically valuable, especially in cases where the delivery optics are constrained to low numerical aperture (NA).

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    4. Estimation of weighted multi-scatterer contributions for improvement of lateral resolution of optical coherence tomography images

      Estimation of weighted multi-scatterer contributions for improvement of lateral resolution of optical coherence tomography images

      A method for improvement of lateral resolution in Optical Coherence Tomography (OCT) is presented. The resolution improvement achieved with this method does not depend on the delivery optics. Moreover the depth of focus is not restricted. The method is based on the lateral oversampling of the image. The laterally oversampled signals are backscattered signals from shifted and overlapped resolution volumes. Signals from successive volumes are correlated due to the region shared by adjacent resolution volumes. By utilizing the cross correlation of signals from such overlapped volumes, resolution can be improved by various degrees depending on which pairs of signals are ...

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    5. Lateral resolution improvement in Optical Coherence Tomography (OCT) images

      Lateral resolution improvement in Optical Coherence Tomography (OCT) images

      A novel method for lateral resolution improvement of Optical Coherence Tomography (OCT) images, which is independent of the focusing of the delivery optics and the depth of field, is presented. This method was inspired by radar range oversampling techniques. It is based on the lateral oversampling of the image and the estimation of the locations of the multiple scatterers which contribute to the signal. The information in the oversampled images is used to estimate the locations of multiple scatterers assuming each contributes a weighted portion to the detected signal, the weight determined by the location of the scatterer and the ...

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    6. Axial resolution improvement by modulated deconvolution in Fourier domain optical coherence tomography

      Axial resolution improvement by modulated deconvolution in Fourier domain optical coherence tomography

      A novel technique for axial resolution improvement in Fourier domain optical coherence tomography (FDOCT) is presented. The technique is based on the deconvolution of modulated optical coherence tomography signals. In FDOCT, the real part of the Fourier transform of the interferogram is modulated by a frequency which depends on the position of the interferogram in k space. A slight numerical k shift results in a different modulation frequency. By adding two shifted signals, beating can appear in the A-scan. When the amount of shifting is appropriately selected, deconvolution of the resulting depth profile, using suitable modulated kernels, yields a narrower ...

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    7. Lateral resolution improvement in oversampled Optical Coherence Tomography images assuming weighted oversampled multi-scatterer contributions

      Lateral resolution improvement in oversampled Optical Coherence Tomography images assuming weighted oversampled multi-scatterer contributions

      A novel method for lateral resolution improvement of Optical Coherence Tomography (OCT) images, which is independent of the focusing of the delivery optics and the depth of field, is presented. This method was inspired by radar range oversampling techniques. It is based on the lateral oversampling of the image and the estimation of the locations of the multiple scatterers which contribute to the signal. The information in the oversampled images is used to estimate the locations of multiple scatterers assuming each contributes a weighted portion to the detected signal, the weight determined by the location of the scatterer and the ...

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    8. Fourier domain optical coherence tomography axial resolution improvement with modulated deconvolution

      Fourier domain optical coherence tomography axial resolution improvement with modulated deconvolution

      In this manuscript the application of a novel technique for axial resolution improvement in Fourier Domain Optical Coherence Tomography (FDOCT) is demonstrated. Axial resolution in FDOCT can be improved by ~7x without the need for a broader bandwidth light source using modulated deconvolution. In FDOCT the real part of FFT of each interferofram is modulated by a frequency which depends on the position of the interferogram. If an interferogram is shifted slightly, the frequency of the real part of the FFT changes. By adding two shifted interferograms, beating can be appeared in the OCT A-Scans. Subsequently deconvolution with suitable kernels ...

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    9. Modulated deconvolution for resolution improvement in Fourier domain optical coherence tomography

      Modulated deconvolution for resolution improvement in Fourier domain optical coherence tomography

      This manuscript presents a novel technique for axial resolution improvement in Fourier Domain Optical Coherence Tomography (FDOCT). The technique is based on the modulated deconvolution of OCT signals which results in a resolution improvement by a factor of ~ 7 without the need for a broader bandwidth light source. This method relies on a combination of two basic properties: beating, which appears when adding two signals of slightly different frequencies, and the resolution improvement, achieved by deconvolution of an OCT image with the encoded source autocorrelation function. In FDOCT the real part of the FFT of the interferogram is modulated by ...

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    10. Optical coherence tomography axial resolution improvement by step-frequency encoding

      Optical coherence tomography axial resolution improvement by step-frequency encoding

      A novel technique for axial resolution improvement of Optical Coherence Tomography (OCT) systems is proposed. The technique is based on step-frequency encoding, using frequency shifting, of the OCT signal. A resolution improvement by a factor of ~7 is achieved without the need for a broader bandwidth light source. This method exploits a combination of two basic principles: the appearance of beating, when adding two signals of slightly different carrier frequencies, and the resolution improvement by deconvolution of the interferogram with an encoded autocorrelation function. In time domain OCT, step-frequency encoding can be implemented by performing two scans, with different carrier ...

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    11. Scatterer size-based analysis of optical coherence tomography images using spectral estimation techniques

      Scatterer size-based analysis of optical coherence tomography images using spectral estimation techniques

      A novel spectral analysis technique of OCT images is demonstrated in this paper for classification and scatterer size estimation. It is based on SOCT autoregressive spectral estimation techniques and statistical analysis. Two different statistical analysis methods were applied to OCT images acquired from tissue phantoms, the first method required prior information on the sample for variance analysis of the spectral content. The second method used k-means clustering without prior information for the sample. The results are very encouraging and indicate that the spectral content of OCT signals can be used to estimate scatterer size and to classify dissimilar areas in ...

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    12. AM-FM techniques in the analysis of optical coherence tomography signals

      The subtle tissue changes associated with the early stages of malignancies, such as cancer, are not clearly discernible even at the current, improved, resolution of optical coherence tomography (OCT) systems. However, these changes directly affect the spectral content of the OCT image that contains information regarding these unresolvable features. Spectral analysis of OCT signals has recently been shown to provide additional information, resulting in improved contrast, directly related to scatterer size changes. Amplitude modulation-frequency modulation (AM-FM) analysis, a fast and accurate technique for the estimation of the instantaneous frequency, phase, and amplitude of a signal, can also be applied to ...

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    1-12 of 12
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    Scatterer size-based analysis of optical coherence tomography images using spectral estimation techniques Optical coherence tomography axial resolution improvement by step-frequency encoding Modulated deconvolution for resolution improvement in Fourier domain optical coherence tomography Fourier domain optical coherence tomography axial resolution improvement with modulated deconvolution Lateral resolution improvement in oversampled Optical Coherence Tomography images assuming weighted oversampled multi-scatterer contributions Axial resolution improvement by modulated deconvolution in Fourier domain optical coherence tomography Lateral resolution improvement in Optical Coherence Tomography (OCT) images Estimation of weighted multi-scatterer contributions for improvement of lateral resolution of optical coherence tomography images Lateral resolution improvement of oversampled OCT images using Capon estimation of weighted subvolume contribution The use of OCT to detect signs of intracranial hypertension in patients with sagittal suture synostosis: Reference values and correlations In Vivo Imaging of Retinal and Choroidal Morphology and Vascular Plexuses of Vertebrates Using Swept-Source Optical Coherence Tomography Widefield OCT Imaging for Quantifying Inner Retinal Thickness in the Nonhuman Primate