Summary: The attachments of muscles onto the hyoid bone were observed macroscopically, and the lengths and widths of each muscles onto the hyoid bone were measured. The tongue-pharyngeal block as a whole obtained from 50 cadavers were used. Each muscle was colored by acrylic pigments for identification. The results showed that the mylohyoid muscles were attached onto the lower anterior surface of the hyoid bone body. The geniohyoid muscles had many types of attachment forms and significant individual differences. The hyoglossal muscles showed various attachments at the posterior end of the greater cornu. The middle pharyngeal constrictor muscles attached with two bundles in some cases. The sternohyoid muscles and omohyoid muscles were classified by their positional relationship with each other. The thyrohyoid muscles were classified by the conditions of their overlaps with the omohyoid muscles and the sternohyoid muscles. From the aforementioned results, the following muscles were found attached to the hyoid bone in a further developed state: mylohyoid muscles, geniohyoid muscles, hyoglossal muscles, thyrohyoid muscles and hyoglossal muscles.

We propose and demonstrate a fiber optic multipoint bending measurement system that uses Bragg gratings inscribed along a multi-core fiber (MCF) and a silicon avalanche photodiode (Si-APD) that produces two-photon absorption (TPA) photocurrent for 1.55-μm light. Because the TPA photocurrent from the Si-APD is proportional to the mean square of the optical intensity, the intensity correlation between 1.55-μm probe and reference beams is measured from it without using complex electrical circuits. The proposed system has different lengths of optical fibers between each core of MCF and input/output ends of a single mode fiber optic system, which makes different the correlation signal between the reference beam and the probe beam reflected from different Bragg gratings in MCF. That enables the reflection spectra of all the Bragg gratings in MCF to be separately measured even when they are overlapped in the wavelength domain. As a result, the bending radius and its direction are measured without using multiple detectors or optical switching devices. We conducted proof-of-concept experiments by using a 7-core MCF with almost the same Bragg gratings inscribed in each core at three points along the fiber. We also demonstrated an example of application to shape measurement.

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We have experimentally investigated feasibility of force measurement based on three-dimensional curvature measurement using a multi-core fiber Bragg grating in a medical catheter along with two-photon absorption process in a silicon avalanche photodiode.