Recently, clinical treatments applying drug delivery system (DDS) have been being developed. However, it is quite difficult to in vivo diagnose spatiotemporal distribution of drug infiltration, so the validation study should be too insufficient to progress the DDS development. In this study, we propose a visualizing assay of DDS, namely 2-Color Optical Coherence Dosigraphy (2C-OCD). 2C-OCD is based on optical coherence tomography using two waveband "2-Color" light sources having different optical absorbance of drug. This can simultaneously provide microscale tomographic images of scatterer density and drug concentration. In order to evaluate the efficacy of this technique, this was applied to drug-diffusion phenomena in microchannel and lipidrich plaques of rabbit with drug administration, respectively. As a result of diffusion experiment, it was confirmed that 2C-OCD can visualize a cross-sectional map of drug concentration, with spatial resolution 5 micro m × 10 μm and accuracy plus-minus 13.0 μM. In ex vivo animal experiment, the enhancement of absorptivity could be observed inside lipidrich plaques, in which DDS drug could be therein uptaken by drug administration.
The absorption maps corresponding to drug concentration were calculated, comparing with their histological images.
Consequently, they had good coincidence with histological examinations, therefore, it was concluded that 2C-OCD could visualize drug infiltration in biological tissue with almost the same spatial resolution as OCT system.
Recently, Fourier-Domain Optical Coherence Tomography (FDOCT), which is a spectral interferometer having
a high speed scanning system, has been improved as 3-dimensional micro imaging technique. This has attracted
the attention of medical scientists as a promising system of early cancer detection. It, however, has been difficult
to quantitatively detect tumor lesion and its malignancy, because interference signals could be dependent on
optical properties of biological tissue. In this study, we propose a tumor detection system based on FDOCT
and oncotropic dye, namely Fourier-Domain Optical Coherence Dosimetry (FDOCD). OCT signals have the
information of absorption by oncotropic dye as well as scattering from tissue, which are separately extracted by
Windowed Inverse FFT corresponding to wavelength bands of interest. Therefore, FDOCD can simultaneously
obtain two optical kinds of tomography, i.e. absorption profile as disease demarcation and scattering profile from
morphologic distribution. In the present report, the calibration experiment was carried out to verify separate
detection of scattering and absorbance. As a result, it indicated that FDOCD could determine the distribution
of scatterer density, eliminating the signal degradation by optical absorption, e.g. drug concentration. It was
suggested that FDOCD could separately and quantitatively monitor scatterer density and drug concentration.
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