Regeneration of chronic tympanic membrane perforation using 3D collagen with topical umbilical cord serum.

Chronic tympanic membrane (TM) perforation is one of the most common otology complications. Current surgical management of TM perforation includes myringoplasty and tympanoplasty. The purpose of this study was to evaluate the efficacy and feasibility of three dimensional (3D) porous collagen scaffolds with topically applied human umbilical cord serum (UCS) for the regeneration of chronic TM perforation in guinea pigs. To achieve this goal, we fabricated porous 3D collagen scaffolds (avg. strut diameter of 236 ± 51 µm, avg. pore size of 382 ± 67 µm, and a porosity of 96%) by using a 3 axis robot dispensing and low temperature plate systems. Guinea pigs were used in a model of chronic TM perforation. In the experimental group (n=10), 3D collagen scaffold was placed on the perforation and topically applied of UCS every other day for a period of 8 days. The control group ears (n=10) were treated with paper discs and phosphate buffered saline (PBS) only using the same regimen. Healing time, acoustic-mechanical properties, and morphological analysis were performed by otoendoscopy, auditory brainstem response (ABR), single-point laser Doppler vibrometer (LDV), optical coherence tomography (OCT), and light microscopic evaluation. The closure of the TM perforation was achieved in 100% of the experimental group vs. 43% of the control group, and this difference was statistically significant (p=0.034). The ABR threshold at all frequencies of the experimental group was significantly recovered to the normal level compared to the control group. TM vibration velocity in the experimental group recovered similar to the normal control level. The difference is very small and they are not statistically significant below 1 kHz (p=0.074). By OCT and light microscopic examination, regenerated TM of the experimental group showed thickened fibrous and mucosal layer. In contrast, the control group showed absence of fibrous layer like a dimeric TM.

Single-step method for fiber-optic probe-based full-range spectral domain optical coherence tomography.

We propose a single-step method appropriated for a fiber-optic probe-based full-range spectral domain optical coherence tomography (OCT). The fiber-optic probe was scanned over a sample with a magnetically driven actuator. In the reference arm, a phase shift of π/2 was applied during two neighbor axial scanning, from which the complex spectral interferogram was directly reconstructed. Since the complex-conjugate-free OCT image is obtained by doing just one Fourier transform on the complex interferogram, obtaining the full-range image is simple in algorithm and effective in computation time. Some full-range images of biological samples created with the proposed method are presented and the processing time is analyzed.

Full range spectral domain optical coherence tomography using a fiber-optic probe as a self-phase shifter.

We present a full range handheld probe type spectral domain optical coherence tomography (SD-OCT) method. Here, the sample arm is composed of a tilted fiber-optic cantilever scanner; thus, the phase shift concurrently occurs while sample scanning. With the phase shift, we could achieve a full range complex-conjugate-free OCT image with no additional phase shifters in the reference arm. To realize this technique, a magnetically actuated probe was adopted. Full range SD-OCT images of a pearl, human fingernail, and human tooth were subsequently obtained using this suggested probe. The scanning range and acquisition speed were 3 mm and 20 frames/s, respectively.

High-penetration swept source Doppler optical coherence angiography by fully numerical phase stabilization.

A high-penetration swept-source optical coherence tomography (HP-SS-OCT) system based on a 1-µm short cavity laser is developed. Doppler OCT processing is applied, along with a custom-made numerical phase stabilization algorithm; this process does not require additional calibration hardware. Thus, our phase stabilization method is simple and can be employed in a variety of SS-OCT systems. The bidirectional blood flow and vasculature in the deep choroid was successfully imaged via two Doppler modes that use different time intervals for Doppler processing. En face projection image of squared power of Doppler shift is compared to ICGA, and the utility of our method is verified.

Two-dimensional scanning probe driven by a solenoid-based single actuator for optical coherence tomography.

We propose the two-dimensional scanning probe operating with a single actuator, which is thought useful as a sample probe for optical coherence tomography (OCT). The probe was designed to use a single-body lensed fiber cantilever loaded with an iron-bead and driven by a single-solenoid actuator. Elliptic spiral trace patterns were achieved using off-axis magnetic fields of the solenoid. A three-dimensional OCT image was obtained for a scanning area of 3.8 mm × 3.4 mm at an acquisition speed of 16.7 s/V. Up to 27 Hz B-scan rate, the proposed probe worked well, and 1000 A-scans were made per each B-scan.

Enhanced imaging of choroidal vasculature by high-penetration and dual-velocity optical coherence angiography.

Dual-beam-scan Doppler optical coherence angiography (DB-OCA) with a 1-µm-wavelength probe is demonstrated for improved in vivo choroidal angiograms of the human eye. This method utilizes two scanning beams with spatial and temporal separation on the retina, and provides two measurable velocity ranges. The method achieves higher sensitivity to very low velocity flows than conventional Doppler optical coherence tomography. Moreover, longer wavelengths allowing greater penetration, enhanced visualization of choroidal vessels is verified with en-face projection images of the Doppler shift squared. Specifically, better choroidal vasculature visibility is achieved at a wavelength of 1 µm than at 840 nm.

Evaluating and identifying pearls and their nuclei by using optical coherence tomography.

Optical coherence tomography (OCT) has been utilized to evaluate pearls including their nuclei noninvasively. By visualizing the internal structure of a pearl, we could measure the thickness of its nacre layer, observe the fine sub-structure of the nacre, and inspect the nucleus through the nacre. The system also allowed us to classify pearls into beaded- and non-beaded ones; usually, the saltwater ones have nuclei even though there are beaded freshwater pears and non-beaded saltwater pearls. Any cracks, crevices, or blemishes not only in the nacre but in the nucleus of a pearl could be clearly visualized. The OCT system was based on a 20 kHz swept-source of a 1.31microm central wavelength and an 110 nm full-width-at-half-maximum (FWHM) bandwidth. To get the 2-D images all around the circumference of a pearl, the pearl was rotated by a motorized rotating stage. And to achieve 3-D volume images, galvano-scans were made along two axes. Of all things, the OCT allowed us to check the use of a forbidden nucleus, usually made of a Giant Clam shell thus fragile, without hurting the pearl. With this modality, we believe, it would be possible evaluating pearls both in qualitative and quantitative. Comparison with the images taken with an optical microscope and X-ray radiograph gives the refractive index of pearl as about 1.53 in average.

Single-body lensed-fiber scanning probe actuated by magnetic force for optical imaging.

We propose a fiber-based hand-held scanning probe suitable for the sample arm of an optical imaging system including optical coherence tomography. To achieve compactness, a single-body lensed-fiber and a solenoid actuator were utilized. The focusing lens of the probe was directly formed onto the distal end of a fiber, which eliminated the need for additional optical components and optical alignment. A ferromagnetic iron bead was glued onto the middle of the fiber to enable actuation by magnetic force, which allowed easy fabrication and good practicality. The fiber piece having the built-in fiber lens was forced to oscillate in its resonant frequency. With the implemented probe, optical coherence tomography images of a human fingertip and a pearl were obtained at an imaging speed of 30 frames/s over a scanning range of 4 mm.