Surgical Outcome for Hemodialysis-Related Upper Cervical Lesions

Keiji Wada,Yasuaki Murata,Yoshiharu Kato 대한척추외과학회 2015 Asian Spine Journal Vol.9 No.5

Study Design: A retrospective study. Purpose: To investigate the surgical outcome for hemodialysis-related upper cervical lesions. Overview of Literature: Surgical outcome of lower cervical lesions in patients undergoing hemodialysis has been reported. However, surgical outcome for upper cervical lesions in hemodialysis patients is unclear. Methods: Upper cervical lesions in nine patients undergoing hemodialysis were surgically treated. Mean age at surgery was 61.6 years (range, 52–68 years), and the mean follow-up period was 45.4 months (range, 2–98 months). Patients had undergone hemodialysis for an average of 25.3 years (range, 16–40 years) at surgery. Seven patients with destructive spondyloarthropathy (DSA) of the upper cervical spine were treated with atlantoaxial or occipitocervical fixation. Two patients with retro-odontoid pseudotumors were treated with C1 posterior arch resection alone. Japanese Orthopedic Association (JOA) scores for cervical myelopathy, postoperative complications, postoperative radiography, and preoperative and postoperative occipital pain were evaluated. Results: Mean preoperative and postoperative JOA score was 3.7 and 8.1, respectively. The seven patients with DSA had severe preoperative occipital pain that disappeared postoperatively. Postoperative radiography showed solid bone union in DSA cases and no instability in pseudotumor cases. Conclusions: Satisfactory surgical outcome was observed for hemodialysis-related upper cervical lesions.

Experimental Verification of a 200-㎑ PWM Inverter with a Current Control for 20-㎑ Sinusoidal Waveform

Keiji Wada,Toshihisa Shimizu 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5

This paper presents design procedure of a 200 ㎑ PWM inverter with a current controller. The switching devices of the inverter consist of Si-MOSFETs and SiC-SBDs, and FPGA is used for control a current waveform. The authors have been developed FPGA controller with AD converter for power electronics circuits. The processing time of FPGA can be ignored time delay because of less than 100 ㎱, but DC current transformer and AD converter should be considered their time delay. A laboratory system rated at 200-㎑ and 200-VA PWM inverter is confirmed that the validity of the design procedure from the experimental results.

Differential Diagnosis of Tumoral Lesions in the Spinal Canal in Patients Undergoing Hemodialysis

Keiji Wada,Yasuaki Murata,Yoshiharu Kato 대한척추외과학회 2015 Asian Spine Journal Vol.9 No.2

Study Design: A retrospective study. Purpose: To clarify the features useful for the differential diagnosis of spinal canal tumoral lesions in patients undergoing hemodialysis. Overview of Literature: Tumoral lesions in the spinal canal are rarely found in hemodialysis patients. Therefore, the differential diagnosis of tumoral lesions in the spinal canal in hemodialysis patients has been very difficult. Methods: Spinal canal tumors in 17 patients undergoing hemodialysis or continuous ambulatory peritoneal dialysis were investigated. Histopathological analysis was conducted for all specimens obtained during surgery. The tumoral lesions were categorized into 3 groups on the basis of histopathology: spinal cord tumor, amyloidoma, and other. Patient medical history and diagnostic images of each group were reviewed. Results: Eight of 17 cases were histopathologically diagnosed as spinal cord tumors and were neurinomas, 6 were amyloidomas, and 3 were classified as other. The rate of spinal cord tumors was 47.1% (8 of 17 cases), which revealed the most frequent lesion type. The rate of amyloidomas and other types was 35.3% (6 of 17 cases) and 17.6% (3 of 17cases), respectively. In the amyloidoma group, the mean duration of hemodialysis (24.3 years) was longer than that of spinal cord tumors and other types (9.2 years and 8.6 years, respectively). All spinal cord tumors were intradural extramedullary, whereas all amyloidomas and other types were extradural. Conclusions: The rate of each tumoral lesion, the duration of hemodialysis, and the tumoral localization are important features for the differential diagnosis of tumoral lesions in the spinal canal in hemodialysis patients.

Design and Implementation of a 500 kHz Switching PWM Inverter without a Dead-Time

Keiji Wada,Takuya Fujii 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

Developments of a high-frequency switching PWM inverter have been presented. In high-switching frequency PWM inverter, a dead time for preventing a short circuit of the inverter circuit is a one of the most critical issues. Especially, it will be affected to inverter operations, such as current distortions, output voltage reduction, and switching frequency limitations. In the case of using the Si-MOSFET, the dead time is normally set to at least 500-ns, and it is fixed value in each circuit. Therefore, the upper limitation of the switching frequency is limited by the dead time. This paper proposes a 500-kHz switching PWM inverter without dead time using Si-MOSFET, and it can be realized for setting low-voltage gate-drive operations. Moreover, it will present the experimental results for a single-phase PWM inverter, when the switching frequency is set to 500 kHz and DC voltage is set to 300 V.

Pycnodysostosis with Multi-Segmental Spinal Canal Stenosis due to Ossification of the Yellow Ligament

Keiji Wada,Koichi Kanaya,Yasuaki Murata,Yoshiharu Kato 대한척추외과학회 2015 Asian Spine Journal Vol.9 No.2

Pycnodysostosis is an autosomal recessive disorder characterized by osteosclerosis, small stature, acro-osteolysis of the distal phalanges, loss of the mandibular angle, separated cranial sutures with open fontanels, and frequent fractures. One identified cause of the disease is reduced activity of the cysteine protease cathepsin K. A 48-year-old woman with a history of frequent fractures presented with a severe gait disturbance. Radiography, computed tomography, magnetic resonance imaging, and gene analysis were performed. Physical examination revealed open fontanels, and radiographs showed increased bone density. DNA sequence analysis revealed a deletion mutation of the cathepsin K gene. We diagnosed pycnodysostosis based on these findings. The magnetic resonance and computed tomography images demonstrated multilevel spinal canal stenosis due to ossification of the yellow ligament. We performed a laminectomy, and the patient’s neurological signs and symptoms improved. To our knowledge, this is the first case of pycnodysostosis with ossification of the yellow ligament.

Surgical Treatment for Atlanto-Occipital Subluxation due to Destructive Spondyloarthropathy in a Patient Undergoing Long-Term Hemodialysis

Keiji Wada,Yasuaki Murata,Yoshiharu Kato 대한척추외과학회 2015 Asian Spine Journal Vol.9 No.4

Destructive spondyloarthropathy (DSA) has been reported in patients undergoing long-term hemodialysis. Cervical spinal lesions, including those of the upper cervical spine, are reported to be some of the most common. To our knowledge, we report for the first time, a case of atlanto-occipital subluxation requiring surgical treatment due to severe myelopathy and nuchal pain in a patient undergoing long-term hemodialysis. The patient was a 66-year-old woman who had undergone hemodialysis for 40 years. She visited our hospital due to an acute progression of gait disturbance and severe nuchal pain. Computed tomography showed posterior subluxation of the atlanto-occipital joints. DSA was also observed in the lower cervical spine. Magnetic resonance imaging showed spinal canal stenosis at both the upper and lower cervical levels. We performed Oc-C7 fixation, C1 laminectomy, and C3–C7 laminoplasty. We first recognized that the atlanto-occipital subluxation was caused by the extremely long-term, in this case, 40 years, hemodialysis.

Role of additional surgical resection for long-term chemo-responder by Gemcitabine with S1 for advanced unresectable pancreatic cancer : a pilot study

Keita Wada,Keiji Sano,Hodaka Amano,Fumihiko Miura,Naoyuki Toyota,Yoshiko Aoyagi,Yutaka Ikeda,Tadahiro Takada 한국간담췌외과학회 2013 한국간담췌외과학회 학술대회지 Vol.2013 No.4

Is “Surgery-First” Treatment Feasible For Both Resectable and Borderline Resectable Pancreatic Ductal Adenocarcinoma?

Keita Wada,Keiji Sano,Hodaka Amano,Fumihiko Miura,Naoyuki Toyota,Tadahiro Takada 한국간담췌외과학회 2012 한국간담췌외과학회 학술대회지 Vol.2012 No.4

A Gate Drive Circuit for Low Switching Losses and Snubber Energy Recovery

Shimizu, Toshihisa,Wada, Keiji The Korean Institute of Power Electronics 2009 JOURNAL OF POWER ELECTRONICS Vol.9 No.2

In order to increase the power density of power converters, reduction of the switching losses at high-frequency switching conditions is one of the most important issues. This paper presents a new gate drive circuit that enables the reduction of switching losses in both the Power MOSFET and the IGBT. A distinctive feature of this method is that both the turn-on loss and the turn-off loss are decreased simultaneously without using a conventional ZVS circuit, such as the quasi-resonant adjunctive circuit. Experimental results of the switching loss of both the Power MOSFET and the IGBT are shown. In addition, an energy recovery circuit suitable for use in IGBTs that can be realized by modifying the proposed gate drive circuit is also proposed. The effectiveness of both the proposed circuits was confirmed experimentally by the buck-chopper circuit.

Thyme (Thymus vulgaris L.) Leaves and Its Contituents Increase the Activities of Xenobiotic-Metabolizing Enzymes in Mouse Liver

Keiko Sasaki,Keiji Wada,Yoshiko Tanaka,Teruki Yoshimura,Koozi Matuoka,Takahiko Anno 한국식품영양과학회 2005 Journal of medicinal food Vol.8 No.2

The effects of thyme (Thymus vulgarisL.) leaves and its phenolic compounds, thymol and carvacrol, on theactivities of xenobiotic-metabolizing enzymes, i.e., phase I enzymes such as 7-ethoxycoumarin O-deethylase (ECOD) andphase II enzymes such as glutathione S-transferase (GST) and quinone reductase (QR), were investigated. Mice were fed witha diet containing thyme (0.5% or 2.0%) or treated orally with thymol (50200 mg/kg) or carvacrol (50200 mg/kg) once aday for 7 successive days, and then the enzyme activities in the livers were analyzed. Dietary administration of 2% thymecaused slightly but significantly higher ECOD, GST, and QR activities by 1.11.4-fold. Thymol (200 mg/kg) treatment re-sulted in significantly higher ECOD, GST, and QR activities by 1.31.9-fold, and carvacrol (200 mg/kg) treatment causedsignificantly higher ECOD, GST, and QR activities by 1.31.7-fold. Thymol-treated animals had significantly higher proteinlevels of GST . and GST ., and carvacrol-treated animals had significantly higher levels of GST .. These results imply thatthyme contains bifunctional inducers (i.e., substances capable of inducing both phase I and phase II enzymes) and that thy-mol and carvacrol may account for the effects of thyme.