• Korean Journal of Optics and Photonics
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• v.22 no.3
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• pp.134-140
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• 2011

In this paper, we developed a frequency-domain diffuse optical tomography(DOT) system for non-invasively imaging in vivo. The system uses near-infrared(NIR) light sources and detectors for which the photon propagation in human tissue is dominated by scattering rather than by absorption. We present the experimental reconstruction images of absorption and scattering coefficients using a liquid tissue phantom, and we obtain the location and shape of an anomaly which has different optical properties than the phantom.

• Journal of Biomedical Engineering Research
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• v.28 no.2
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• pp.229-234
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• 2007

Diffuse optical tomography (DOT) is a relatively new medical imaging modality which uses near infrared light to image large-sized tissues noninvasively. We constructed a frequency-domain DOT system to measure the optical properties of optical phantoms and human tissues. The FD-DOT uses the intensity-modulated infrared light source that illuminates the biological tissues. The phase shift and modulation changes at each detector site are separately processed to measure the optical properties. The absorption and scattering coefficients are separately estimated using inverse algorithms.

• Proceedings of the Optical Society of Korea Conference
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• 2007.07a
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• pp.37-38
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• 2007

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.10a
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• pp.658-660
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• 2021

The work within this study develops an algorithm based on the structural similarity index to assess numerically between reconstructed images with a reference image to separate the homogeneity and heterogeneity for diffuse optical tomography. Global geometry and region of interest assessment have been measured to yield the similarity. The results indicate that the mean of structural similarity index shows potential performance to distinguish between visible and invisible inclusion inside the model. Therefore, the structural similarity index may promise to assist the image assessment for evaluating breast structural information.

• Journal of the Optical Society of Korea
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• v.20 no.5
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• pp.607-613
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• 2016

The pleura is known as an end target organ of exposure to toxic environmental materials such as fine particulate matter and asbestos. Moreover, long-term exposure to hazardous materials can eventually lead to fatal lung disease such as diffuse pleural fibrosis or mesothelioma. Chest computed tomography (CT) and ultrasound are gold standard imaging modalities for detection of advanced pleural disease. However, a diagnostic tool for early detection of pleural reaction has not been developed yet due to difficulties in imaging ultra-fine structure of the pleura. Optical coherence tomography (OCT), which provides cross-sectional images of micro tissue structures at a resolution of 2-10 μm, can image the mesothelium with a thickness of ~100 μm and therefore enables investigation of the early pleural reaction. In this study, we induced the early pleural reaction according to a time sequence after pleurodesis using talc, which has been widely used in the clinical field. The pleural reaction in talc grouped according to the time sequence (1st, 2nd, 4th weeks) showed a significant thickening (average thickness: 45 ± 7.5 μm, 80 ± 10.7 μm, 90 ± 12.5 μm), while the pleural reaction in sham and normal groups showed pleural change from normal to minimal thickening (average thickness: 16 ± 5.5 μm, 17 ± 4.5 μm, 15 ± 6.5 μm, and 12 ± 7.5 μm, 13 ± 2.5 μm, 12 ± 3.5 μm). The measurement of pleural reaction by pathologic examinations was well-matched with the measurement by OCT images. This is the first study for measuring the thickness of pleural reactions using a biophotonic modality such as OCT. Our results showed that OCT can be useful for evaluating the early pleural reaction.

• Journal of the Korean Society of Radiology
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• v.15 no.4
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• pp.525-531
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• 2021

The detector of the positron emission tomography (PET) is composed using a plurality of scintillation pixels and photo sensors. The use of multiple photo sensors increases cost and complicates signal processing. In this study, a detector with reduced cost and simple signal processing was designed using a small number of photo sensors. A scintillation pixel and a small number of photo sensors were used, and a optical guide was used to deliver light to all the photo sensors. A reflector is applied to the scintillation pixel and the optical guide to transmit the maximum amount of light to the photo sensor. A diffuse reflector and a specular reflector were used for the reflector, and a flood image was obtained by applying different thicknesses of the optical guide. An optimal combination was selected through comparative analysis of the acquired flood images. As a result, when specular reflectors were used for both the scintillation pixel and the optical guide, excellent flood images were obtained from optical guides of all thicknesses. For the optical guide, the optimal image was obtained when using a 3 mm thickness in consideration of the size of the image and the analysis of the point where the image of the scintillation pixel was formed.

• Journal of the Korean Society of Radiology
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• v.13 no.6
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• pp.825-830
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• 2019

A detector module measuring a depth of interaction was developed using silicon photomultiplier (SiPM) and two layers of scintillation crystal array treated with multiple reflectors. When reconstructing an image based on a signal obtained by using different types of reflector of each layer, the interaction positions of scintillation pixels and gamma rays could be tracked by utilizing the feature that all scintillation pixels were recorded at different positions. The bottom layer uses a specular reflector, and the top layer uses a diffuse reflector to differently process the size of the signal obtained from the SiPM. The optical grease was used to recude the sharp refractive index change between the layers of scintillator and the SiPM. The signals obtained from the 16 SiPMs were reduced to four signals using the Anger equations, and the images were reconstructed using them. All the scintillation pixels composed of the two layers appeared in the reconstructed image, which distinguished the layer where the scintillation pixels and gamma rays interacted. If the detectors, which measure the interaction depth of two layers using different reflectors, will be applied to preclinical positron emission tomography, the degradation of spatial resolution appearing outside the field of interest could be solved.