Mr. Masahiro Yajima Profile

Masahiro Yajima

at Keio Univ

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Publications (2)

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Proceedings Article | 4 March 2014 Paper

Prediction of myocardial damage depth induced by extracellular photosensitization reaction using fluorescence measurement in vivo

M. Takahashi, E. Ogawa, T. Nakamura, H. Kawakami, N. Machida, M. Yajima, M. Kurotsu, A. Ito, T. Kimura, T. Arai

Proceedings Volume 8926, 89262X (2014) https://doi.org/10.1117/12.2036506

KEYWORDS: Luminescence, Backscatter, Heart, In vivo imaging, Sodium, Oxygen, Blood circulation, Laser irradiation, Francium, Ions

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We experimentally studied the correlation between myocardial damage depth due to the extracellular photosensitization reaction (PR) using talaporfin sodium and fluorescence-fall amount (FA), which is calculated from the measured backscattering fluorescence intensity via a manipulatable 7 Fr. laser catheter during the PR operation in vivo to establish treatment depth predictor for a non-thermal tachyarrhythmia treatment. The PR was performed to left and/or right ventricle in the open-chest canine heart. The laser irradiation of 663±2 nm in wavelength via the laser catheter was operated 15 min after the intravenous administration of talaporfin sodium with concentration of 36.2±8.0 μg/ml in plasma. The irradiation was operated with irradiance of 5, 10, 20 W/cm², and duration of 5, 10, 20 s. Backscattering fluorescence of 710±2 nm in wavelength was measured via the laser catheter during the PR. The FA was calculated multiplying the irradiation duration by the fluorescence-fall, which is subtraction of the fluorescence intensity at the kickoff and end of the irradiation. The canine heart was extracted 1 week after the PR and HE stained specimen was histologically evaluated. The correlation of the myocardial damage depth and FA was investigated. We found that FA obtained a logarithmic relation to the myocardial damage depth. We think that the FA might be available to predict the PR induced myocardial damage depth for the application of tachyarrhythmia treatment under catheterization in vivo.

Proceedings Article | 26 February 2014 Paper

Photosensitization reaction along depth of a culture well with high concentration of talaporfin sodium for extra-cellular photodynamic therapy study

Masahiro Yajima, Hiroshige Kawakami, Emiyu Ogawa, Mei Takahashi, Tsunenori Arai

Proceedings Volume 8941, 89410V (2014) https://doi.org/10.1117/12.2041950

KEYWORDS: Oxygen, Sodium, Electrodes, Photodynamic therapy, Temperature metrology, Laser irradiation, In vitro testing, Tissue optics, Tissues, Diffusion

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We studied photosensitization reaction progress in a cell culture well by oxygen partial pressure distribution measurement along the well depth direction with a high concentration of talaporfin sodium solution. The talaporfin sodium solution of 20 μg/ml in concentration with 2.8 mm thickness in the well was irradiated from the well bottom by 663 nm excitation laser with 0.29 W/cm². A small Clark-type oxygen electrode was used to measure oxygen partial pressure during the photosensitization reaction with approximately 200 μm resolution. Corrections against solution temperature change and direct light irradiation were applied to the electrode output. The oxygen partial pressures at various depths were decreased uniformly from the atmospheric oxygen partial pressure with the photosensitization reaction progress up to the irradiation of 1.0 J/cm² in radiant exposure. In the case of photosensitization reaction over 1.0 J/cm² in radiant exposure, the oxygen partial pressure distribution along the well depth was non-uniform. In the case of photosensitization reaction with 40 J/cm² in radiant exposure in the solution without cells, there was pressure gradient of 2.8×10⁴ mmHg/m from 0.5 to 1.0 mm in depth from the solution surface. In this case, there was no pressure gradient near the bottom of the well. In contrast, with myocardial cells at the bottom, oxygen partial pressure gradient of 7.5×10³ mmHg/m from 1.5 to 2.0 mm in the depth was appeared after irradiation with 40 J/cm² in radiant exposure. Consequently, we found that oxygen partial pressure distribution along the depth in the well with high concentration of talaporfin sodium solution was dynamically changed with time of the photosensitization reaction using the laser irradiation from the bottom. We think this dynamic pressure change in the well might be useful to understand the photosensitization reaction progress in the well experiment system in vitro corresponding to the extracellular PDT.

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