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RISS 인기검색어
- 검색키워드
- 저자 : Yusuke Wakabayashi (검색결과 4 건)
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Response of a Plate-type Thermoluminescence Dosimeter to a Therapeutic Carbon Beam
Yusuke Koba,Shigekazu Fukuda,Kiyomitsu Shinsho,Genichiro Wakabayashi,Satoshi Tamatsu 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.7
In order to measure the three-dimensional dose distribution in X-ray radiotherapy, we developeda plate-type thermoluminescence dosimeter (TLD) using the TL phosphor Li3B7O12:Cu, which hasZeff = 7.42 and a density of 1.01 gcm−3. This detector was expected on useful application inadvanced X-ray radiotherapies such as intensity-modulated ratiation therapy (IMRT) etc., becauseit can obtain 3D dose measurements simply and quickly with a single exposure. In this paper, wereport the response of this plate-type TLD to a therapeutic carbon beam at the Heavy Ion MedicalAccelerator in Chiba (HIMAC). Using a plate heater and charge coupled device (CCD) camera, wecaptured thermoluminescence images of plate-type TLDs irradiated by a therapeutic carbon beam. The TL intensity was measured at each water equivalent depth and compared with output of theionization chamber. The relative TL efficiency of this TLD as 60Co gamma-ray equivalent decreasedgradually with increasing dose-averaged linear-energy-transfer (LET), reaching about 20% at theBragg peak of 290 MeV/u carbon ions.
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A Morphologically Atypical Case of Atlantoaxial Rotatory Subluxation
Umebayashi, Daisuke,Hara, Masahito,Nishimura, Yusuke,Wakabayashi, Toshihiko The Korean Neurosurgical Society 2014 Journal of Korean neurosurgical society Vol.55 No.5
A rare case of atlantoaxial rotatory subluxation occurred after pediatric cervical spine surgery performed to remove a dumbbell-shaped meningioma at the level of the C1/C2 vertebrae. This case is classified as a post-surgical atlantoaxial rotatory subluxation, but has a very rare morphology that has not previously been reported. Although there are several reports about post-surgical atlantoaxial rotatory subluxation, an important point of this case is that it might be directly related to the spinal cord surgery in C1/C2 level. On day 6 after surgery, the patient presented with the Cock Robin position, and a computed tomography scan revealed a normal type of atlantoaxial rotatory subluxation. Manual reduction was performed followed by external fixation with a neck collar. About 7 months after the first surgery, the subluxation became severe, irreducible, and assumed an atypical form where the anterior tubercle of C1 migrated to a cranial position, and the posterior tubercle of C1 and the occipital bone leaned in a caudal direction. The pathogenic process suggested deformity of the occipital condyle and bilateral C2 superior facets with atlantooccipital subluxation. A second operation for reduction and fixation was performed, and the subluxation was stabilized by posterior fixation. We encountered an unusual case of a refractory subluxation that was associated with an atypical deformity of the upper spine. The case was successfully managed by posterior fixation.
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Biomechanical Analysis of a Pedicle Screw-Rod System with a Novel Cross-Link Configuration
Yasuhiro Nakajima,Masahito Hara,Daisuke Umebayashi,Shoichi Haimoto,Yu Yamamoto,Yusuke Nishimura,Toshihiko Wakabayashi 대한척추외과학회 2016 Asian Spine Journal Vol.10 No.6
Study Design: The strength effects of a pedicle screw-rod system supplemented with a novel cross-link configuration were biomechanically evaluated in porcine spines. Purpose: To assess the biomechanical differences between a conventional cross-link pedicle screw-rod system versus a novel crosslink instrumentation, and to determine the effect of the cross-links. Overview of Literature: Transverse cross-link systems affect torsional rigidity, but are thought to have little impact on the sagittal motion of spinal constructs. We tested the strength effects in pullout and flexion-compression tests of novel cross-link pedicle screw constructs using porcine thoracic and lumbar vertebrae. Methods: Five matched thoracic and lumbar vertebral segments from 15 porcine spines were instrumented with 5.0-mm pedicle screws, which were then connected with 6.0-mm rods after partial corpectomy in the middle vertebral body. The forces required for construct failure in pullout and flexion-compression tests were examined in a randomized manner for three different cross-link configurations: un-cross-link control, conventional cross-link, and cross-link passing through the base of the spinous process. Statistical comparisons of strength data were analyzed using Student’s t -tests. Results: The spinous process group required a significantly greater pullout force for construct failure than the control group (p =0.036). No difference was found between the control and cross-link groups, or the cross-link and spinous process groups in pullout testing. In flexion-compression testing, the spinous processes group required significantly greater forces for construct failure than the control and cross-link groups (p <0.001 and p =0.003, respectively). However, there was no difference between the control and cross-link groups. Conclusions: A novel cross-link configuration that features cross-link devices passing through the base of the spinous processes increased the mechanical resistance in pullout and flexion-compression testing compared to un-cross-link constructs. This configuration provided more resistance to middle-column damage under flexion-compression testing than conventional cross-link configuration.
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