Ms. Haruna Nakazawa Profile

Haruna Nakazawa

at Keio Univ

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Proceedings Article | 23 October 2018 Paper

Modified optical coefficient measurements using a single high-NA fiber with detection parameter changes at a tip

Haruna Nakazawa, Marika Doi, Emiyu Ogawa, Tsunenori Arai

Proceedings Volume 10820, 1082020 (2018) https://doi.org/10.1117/12.2500742

KEYWORDS: Tissue optics, Monte Carlo methods, Optical fibers, Ray tracing

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To avoid the instability of an optical coefficient measurement using sliced tissue preparation, an attenuation coefficient measurement by puncturing an optical fiber in bulk tissue have been reported. We proposed a modified puncturing method to obtain an absorption coefficient and scattering coefficient by increasing optical information. We used the light intensity measurement through a single high-NA fiber puncturing into an optically thick bulk tissue varying detection parameters, the depth and field of view (FOV), at the tip. The light intensity measurement and ray trace calculation using the Monte Carlo method (inverse or normal) were employed. We constructed the measurement system which can change the FOV at the fiber tip inside the bulk tissue using the variable aperture outside the bulk tissue. A 200 μmΦ NA:0.5 fiber installed in a 21G needle was punctured down to surface of the bulk tissue to measure light intensity in the bulk tissue. Using homogeneous optical model solution, the accuracy about attenuation coefficients of the constructed experimental system was confirmed. The error in the attenuation coefficient was up to 1.4%. We demonstrated the optical coefficient measurement of porcine myocardium using the proposed method. To fit dependence of the measured attenuation coefficients on FOV, we decided that the absorption coefficient, the scattering coefficient, and anisotropic parameter were 0.2 mm^-1, 10 mm^-1, and 0.96, respectively. We proposed modified puncturing optical coefficient measurement varying depth and FOV. We demonstrated its usefulness on myocardium.

Proceedings Article | 13 February 2018 Presentation + Paper

Optical coefficient measurements using bulk living tissue by an optical fiber puncture with FOV change

Haruna Nakazawa, Marika Doi, Emiyu Ogawa, Tsunenori Arai

Proceedings Volume 10492, 104920P (2018) https://doi.org/10.1117/12.2289332

KEYWORDS: Tissue optics, Optical testing, Optical fibers, Signal attenuation, Monte Carlo methods, Ray tracing, Absorption, Scattering, Tissues, Geometrical optics

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To avoid an instability of the optical coefficient measurement using sliced tissue preparation, we proposed the combination of light intensity measurement through an optical fiber puncturing into a bulk tissue varying field of view (FOV) and ray tracing calculation using Monte-Carlo method. The optical coefficients of myocardium such as absorption coefficient μa, scattering coefficient μs, and anisotropic parameter g are used in the myocardium optical propagation. Since optical coefficients obtained using thin sliced tissue could be instable because they are affected by dehydration and intracellular fluid effusion on the sample surface, variety of coefficients have been reported over individual optical differences of living samples.

The proposed method which combined the experiment using the bulk tissue with ray tracing calculation were performed. In this method, a 200 μmΦ high-NA silica fiber installed in a 21G needle was punctured up to the bottom of the myocardial bulk tissue over 3 cm in thickness to measure light intensity changing the fiber-tip depth and FOV. We found that the measured attenuation coefficients decreased as the FOV increased. The ray trace calculation represented the same FOV dependence in above mentioned experimental result. We think our particular fiber punctured measurement using bulk tissue varying FOV with Inverse Monte-Carlo method might be useful to obtain the optical coefficients to avoid sample preparation instabilities.

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