arXiv subjects

Yoshiaki Yasuno

Publications and source records attributed to Yoshiaki Yasuno.

24 records · Page 2Linked to original sources

arXiv2023

Critique of optical coherence tomography in epistemological metrology

This treaties aims to introduce a speculative framework to comprehend modern metrology. In a classical sense, measurement measures physically existing quantities, such as length, mass, and time. By contrast, modern measurement measures a wide spectrum of objects, for example, an imaging biomarker, which is a user-defined pattern. Artificial-intelligence (AI)-based diagnosis is another example. If we regard an optical coherence tomography (OCT) device equipped with diagnostic AI as a comprehensive "measurement system," the object being measured is a "disease," which is not a physical quantity but a concept. To comprehend the wide range of modern measurements, we introduce a speculative, i.e., philosophical and theoretical, model called the "epistemological-metrology model." In this model, we describe the act of measurement as cascading encoding-and-decoding processes. In the encoding processes, three types of objects-to-be measured are considered, which include substance, existence, and concept. Then we classify acts of measurement into "sensing," "understanding," and "reasoning," which measure the substance, existence, and concept, respectively. We note that the measurements in the understanding and reasoning classes are constructive. Namely, they proactively define the quantity-to-be-measured by the measurement modalities themselves. A speculative method to warrant the relevance of such constructive measurements is presented. We investigate several modern OCT-related measurements, including AI-based diagnosis, types of polarization sensitive OCT, and attenuation coefficient imaging, using our theoretical framework.

physics.med-ph↗

arXiv2023

Synthesizing the degree of polarization uniformity from non-polarization-sensitive optical coherence tomography signals using a neural network

Degree of polarization uniformity (DOPU) imaging obtained by polarization-sensitive optical coherence tomography (PS-OCT) has the potential to provide biomarkers for retinal diseases. It highlights abnormalities in the retinal pigment epithelium that are not always clear in the OCT intensity images. However, a PS-OCT system is more complicated than conventional OCT. We present a neural-network-based approach to estimate the DOPU from standard OCT images. DOPU images were used to train a neural network to synthesize the DOPU from single-polarization-component OCT intensity images. DOPU images were then synthesized by the neural network, and the clinical findings from ground truth DOPU and synthesized DOPU were compared. There is a good agreement in the findings for RPE abnormalities: recall was 0.869 and precision was 0.920 for 20 cases with retinal diseases. In five cases of healthy volunteers, no abnormalities were found in either the synthesized or ground truth DOPU images. The proposed neural-network-based DOPU synthesis method demonstrates the potential of extending the features of retinal non-PS OCT.

physics.med-ph↗

arXiv2023

Multi-contrast Jones-matrix optical coherence tomography -- the concept, principle, implementation, and applications

Jones-matrix optical coherence tomography (JM-OCT) is an extension of OCT that provides multiple types of optical contrasts of biological and clinical samples. JM-OCT measures the spatial distribution of the Jones matrix of the sample and also its time sequence. All contrasts (i.e., multi-contrast OCT images) are then computed from the Jones matrix. The contrasts obtained from the Jones matrix include the conventional and polarization-insensitive OCT intensity, cumulative and local phase retardation (birefringence), degree-of-polarization uniformity quantifying the polarization randomness of the sample, signal attenuation coefficient, sample scatterer density, Doppler OCT, OCT angiography, and dynamic OCT. JM-OCT is a generalized version of OCT because it measures the generalized form of the sample information; i.e., the Jones matrix sequence. This review summarizes the basic conception, mathematical principle, hardware implementation, signal and image processing, and biological and clinical applications of JM-OCT. Advanced technical topics, including JM-OCT-specific noise correction and quantity estimation and JM-OCT's self-calibration nature, are also described.

physics.med-ph↗

arXiv2022

Optical coherence tomography -- principles, implementation, and applications in ophthalmology

This short textbook was written for someone who newly start studying, doing research, or development about optical coherence tomography (OCT) or using OCT. The first chapter summarizes the concept and the history of OCT. In the second chapter, the technologies of OCT are summarized, which includes the mathematical principle, hardware implementation, the instructions for designs such as interferometer and wavelength selections, and theories of resolutions and sensitivity. In the third chapter, some examples of ophthalmic applications of OCT are described. In the last chapter, instructions for next learning steps are given.

physics.med-ph↗

arXiv2022

Label-free drug response evaluation of human derived tumor spheroids using three-dimensional dynamic optical coherence tomography

We demonstrate label-free drug response evaluations of human breast (MCF-7) and colon (HT-29) cancer spheroids via dynamic optical coherence tomography (OCT). The MCF-7 and HT-29 spheroids were treated with paclitaxel (PTX, or Taxol) and the active metabolite of irinotecan (SN-38), respectively. The drugs were applied using 0 (control), 0.1, 1, and 10 uM concentrations with treatment times of 1, 3, and 6 days. The samples were scanned using a repeated raster scan protocol and two dynamic OCT algorithms, logarithmic intensity variance (LIV) and late OCT correlation decay speed (OCDSl) analyses, were applied to visualize the tissue and cellular dynamics. Different drug response patterns of the two spheroid types were visualized clearly and analyzed quantitatively by LIV and OCDSl imaging. For both spheroid types, structural corruptions and reduction of LIV and OCDSl were observed. These results may indicate different mechanisms of the drug action. The results suggest that dynamic OCT can be used to highlight drug response patterns and perform anti-cancer drug testing.

physics.med-ph↗

arXiv2022

Label-free metabolic imaging of non-alcoholic-fatty-liver-disease (NAFLD) liver by volumetric dynamic optical coherence tomography

Label-free metabolic imaging of non-alcoholic fatty liver disease (NAFLD) mouse liver is demonstrated ex vivo by dynamic optical coherence tomography (OCT). The NAFLD mouse is a methionine choline-deficient (MCD)-diet model, and two mice fed MCD diet for 1 and 2 weeks are involved in addition to a normal-diet mouse. The dynamic OCT is based on repeating raster scan and logarithmic intensity variance (LIV) analysis which enables volumetric metabolic imaging with a standard-speed (50,000 A-lines/s) OCT system. Metabolic domains associated with lipid droplet accumulation and inflammation are clearly visualized three-dimensionally. Particularly, the normal-diet liver exhibits highly metabolic vessel-like structures of peri-vascular hepatic zones. The 1-week MCD-diet liver shows ring-shaped highly metabolic structures formed with lipid droplets. The 2-week MCD-diet liver exhibits fragmented vessel-like structures associated with inflammation. These results imply that volumetric LIV imaging is useful for visualizing and assessing NAFLD abnormalities.

physics.med-ph↗