Yuki Hata

Effects of the in vivo predegenerated nerve graft on early Schwann cell migration: Quantitative analysis using S100-GFP mice

In peripheral nerve transection injury, continuity of axons as well as that of the basal lamina is disconnected. In such case, migrating Schwann cells (SCs) would be the only axonal guidance at an early stage of regeneration. However, it takes a few days for the dedifferentiated SCs to start migration, while axonal growth begins a few hours after injury. Consequently, the axons without guidance extensively branch out and wander off at the lesion, resulting in aberrant reinnervation. Therefore, enhancing SCs migration could be an attractive therapeutic strategy. In this study, we investigated the effects of the in vivo nerve predegeneration on SC migration and the time course of these changes. In our analysis, we established a novel animal model by nerve transplantation from S100-GFP mice (in which SCs constitutively express green fluorescent protein driven by the S100B promoter), by which SC migration could be exclusively visualized. Our results showed that SCs acquire the maximal migration ability with 14-day predegeneration, but subsequently it gradually decreased. There was a correlation between the time course of the changes in SC migration and the number of activated macrophages. These findings suggest that using predegenerated nerve grafts in repairing the transected nerves could facilitate SC migration into the recipient nerve stump. This technique could be beneficial for early establishment of axonal guidance and possible functional improvement after transection injury.

DIEP Flap Breast Reconstruction Using 3-dimensional Surface Imaging and a Printed Mold.

Summary: Recent advances in 3-dimensional (3D) surface imaging technologies allow for digital quantification of complex breast tissue. We performed 11 unilateral breast reconstructions with deep inferior epigastric artery perforator (DIEP) flaps (5 immediate, 6 delayed) using 3D surface imaging for easier surgery planning and 3D-printed molds for shaping the breast neoparenchyma. A single- or double-pedicle flap was preoperatively planned according to the estimated tissue volume required and estimated total flap volume. The DIEP flap was then intraoperatively shaped with a 3D-printed mold that was based on a horizontally inverted shape of the contralateral breast. Cosmetic outcomes were assessed as satisfactory, as confirmed by the postoperative 3D measurements of bilateral breasts. We believe that DIEP flap reconstruction assisted with 3D surface imaging and a 3D-printed mold is a simple and quick method for rebuilding a symmetric breast.

Open-air type plasma chemical vaporization machining by applying pulse-width modulation control

Photolithography techniques have been used to enable the low-cost and high-speed transfer of a pattern onto a silicon wafer. However, owing to the high integration of semiconductors, extreme ultraviolet will be increasingly used as the exposure light source and all optics must be reflective to focus light because the wavelength of the light will be so short that it cannot pass through a lens. The form accuracy of reflective optics affects the accuracy of transfer, and a flatness of less than 32 nm on a 6 inch photomask substrate is required according to the International Technology Roadmap for Semiconductors roadmap. Plasma chemical vaporization machining is an ultraprecise figuring technique that enables a form accuracy of nanometre order to be obtained. In our previous study, the removal volume was controlled by changing the scanning speed of the worktable. However, a discrepancy between the theoretical scanning speed and the actual scanning speed occurred owing to the inertia of the worktable when the change in speed was rapid. As an attempt to resolve this issue, we controlled the removal volume by controlling the electric power applied during plasma generation while maintaining a constant scanning speed. The methods that we adapted to control the applied electric power were amplitude-modulation (AM) control and pulse-width modulation (PWM) control. In this work, we evaluate the controllability of the material removal rate in the AM and PWM control modes.

Topological Analysis for Arteriovenous Malformations via Computed Tomography Angiography: Part 2: Practical Application.

Background: In a previous study, the authors outlined a technique for calculating the number of abnormal vascular loop structures described in 3-dimensional computed tomography angiography. To be developed into a quantitative evaluation method for soft-tissue arteriovenous malformations (AVMs), the concept needs assessment of validity. Methods: Computed tomography angiography results of 19 soft-tissue AVMs and 18 control abdominal vessels are utilized. Enhanced vascular lumen regions over 120 HU were extracted by a region growing method and skeletonized into wire frame graph models. The number of vascular loop structures in graphs is calculated as 1 − [Number of nodes] + [Number of edges], and results are compared between AVM/control groups, pre-/postprogression, and pre-/posttreatment. Results: Average vascular lumen capacity of AVMs was 57.5 ml/lesion, and average number of vascular loops was 548 loops/lesion. Loop density of AVMs (weighted average, 9.5 loops/ml) exhibited statistically significant (P < 0.001) greater value than normal abdominal blood vessels (weighted average, 1.3 loops/ml). In all 4 cases without treatment, number of loops and loop density both increased. Particularly, number of loops increased greatly by 2 times or more in 3 cases. In all 7 cases with treatment, number of loops and vascular lumen capacity significantly (P = 0.0156) decreased. Particularly, number of loops showed clearer decrease in cases with entire lesion treatment than partial treatment. Conclusions: Total number of described vascular loop structures and their density or volume well reflected the existence, progression, and remission of soft-tissue AVMs. Topological analysis can be expected to be developed into a quantitative evaluation for AVMs.

Topological Analysis for Arteriovenous Malformations via Computed Tomography Angiography: Part 1: Mathematical Concepts

Background: Evaluating the progression of soft-tissue arteriovenous malformation (AVMs) is still problematic. To establish a quantitative method, we took a morphological approach. Methods: Normal blood vessels in early-phase 3D-computed tomography angiography images are theoretically expected to be tree-like structures without loops, whereas AVM blood vessels are expected to be mesh-like structures with loops. Simplified to the utmost limit, these vascular structures can be symbolized with wire-frame models composed of nodes and connecting edges, in which making an extra loop always needs one more of edges than of nodes. Results: Total amount of abnormal vascular structures is estimated from a simple equation: Number of vascular loops = 1 − ([Number of nodes] − [Number of edges]). Conclusion: Abnormalities of AVM vascular structures can be mathematically quantified using computed tomography angiography images.

Material Removal Rate Control in Open-Air Type Plasma Chemical Vaporization Machining by Pulse Width Modulation of Applied Power

Plasma chemical vaporization machining (PCVM) is an ultraprecise figuring technique for optical components without introducing the subsurface damage. In our previous study, the material removal volume was controlled by changing the scanning speed of the worktable. However, because of inertia of the worktable, a discrepancy between the theoretical scanning speed and the actual scanning speed will occur if the spatial change rate of speed is rapid. Therefore, we proposed the application of the pulse width modulation (PWM) control and the amplitude modulation (AM) control of the applied RF power to control the material removal rate (MRR). Experimental results showed that the relationship between the MRR and the average RF power had high linearity, the control range of the PWM control mode was from 0.19 x 10-2 mm3/min to 3.90 x 10-2 mm3/min (from 5% to 100%), which was much wider than that of the AM control mode.

Material Removal Rate Control in Open-Air Type Plasma Chemical Vaporization Machining Using Optical Actinometry

Open-air type numerically controlled plasma chemical vaporization machining (NC-PCVM) is promising technique to fabricate the ultra-precision optical components and to finish the functional materials. The objective shape is fabricated by controlling the scanning speed of the localized plasma because removal volume is proportional to the dwelling time of the plasma on the workpiece surface. To achieve deterministic figuring with shape accuracy of nanometer level, it is essential to keep volumetric material removal rate (MRR) constant during and batch to batch processing. The removal rate is proportional to the density of fluorine radical generated by plasma. So, we control the electric power to keep the removal rate constant during the process based on the fluorine atomic density obtained by optical emission actinometry. We report the relationship between MRR and fluorine atomic density measured by optical emission actinometry.