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Shinya Hayashi

Publications and source records attributed to Shinya Hayashi.

12 recordsLinked to original sources
PubMed2007

CT-based postimplant dosimetry of prostate brachytherapy: comparison of 1-mm and 5-mm section CT.

PURPOSE: The aim of this study was to compare the outcomes between 1-mm and 5-mm section computed tomography (CT)-based postimplant dosimetry. MATERIALS AND METHODS: A series of 21 consecutive patients underwent permanent prostate brachytherapy. The postimplant prostate volume was calculated using 1-mm and 5-mm section CT. One radiation oncologist contoured the prostate on CT images to obtain the reconstructed prostate volume (pVol), prostate V(100) (percent of the prostate volume receiving at least the full prescribed dose), and prostate D(90) (mean dose delivered to 90% of the prostate gland). The same radiation oncologist performed the contouring three times to evaluate intraobserver variation and subjectively scored the quality of the CT images. RESULTS: The mean +/-1 SD postimplant pVol was 20.17 +/- 6.66 cc by 1-mm section CT and 22.24 +/- 8.48 cc by 5-mm section CT; the difference in the mean values was 2.06 cc (P < 0.01). The mean postimplant prostate V(100) was 80.44% +/- 7.06% by 1-mm section CT and 77.33% +/- 10.22% by 5-mm section CT. The mean postimplant prostate D(90) was 83.28% +/- 10.81% by 1-mm section CT and 78.60% +/- 15.75% by 5-mm section CT. In the evaluation of image quality, 5-mm section CT was assigned significantly higher scores than 1-mm section CT. In regard to intraobserver variation, 5-mm section CT revealed less intraobserver variation than 1-mm section CT. CONCLUSION: Our current results suggested that the outcomes of postimplant dosimetry using 1-mm section CT did not improved the results over those obtained using 5-mm section CT in terms of the quality of the CT image or reproducibility.

Brachytherapy↗
PubMed2006

Comparison of electrode structures and photovoltaic properties of porphyrin-sensitized solar cells with TiO2 and Nb, Ge, Zr-added TiO2 composite electrodes.

Electrode structures and photovoltaic properties of porphyrin-sensitized solar cells with TiO2 and Nb-, Ge-, and Zr-added TiO2 composite electrodes were examined to disclose the effects of partial substitution of Ti atom by the other metals in the composite electrodes. The TiO2 and Nb-, Ge-, and Zr-added TiO2 composite electrodes were prepared by sol-gel process using laurylamine hydrochloride as a template for the formation of micellar precursors yielding well-defined mesoporous nanocrystalline structures, as in the cases of the formation of silica and titania tubules and nanoparticles by the templating mechanism. The TiO2 and Nb-, Ge-, and Zr-added TiO2 composite electrodes were characterized by transmission electron microscopy, BET surface area analysis, X-ray diffraction analysis, Raman spectroscopy, and impedance measurements. The TiO2 anatase nanocrystalline structure is retained after doping a small amount (5 mol %) of Nb, Ge, or Zr into the TiO2 structure, suggesting the homogeneous distribution of the doped metals with replacing Ti atom by the doped metal. The power conversion efficiency of the porphyrin-sensitized solar cells increases in the order Zr-added TiO2 (0.8%) < Nb-added TiO2 (1.2%) < TiO2 (2.0%) < Ge-added TiO2 cells (2.4%) under the same conditions. The improvement of cell performance of the Ge-added TiO2 cell results from the negative shift of the conduction band of the Ge-added TiO2 electrode. The Ge-added TiO2 cell exhibited a maximum power conversion efficiency of 3.5% when the porphyrin was adsorbed onto the surface of the Ge-added TiO2 electrode with a thickness of 4 microm in MeOH for 1 h.

Journal Article↗
PubMed2006

Importance of the CT/MRI fusion method as a learning tool for CT-based postimplant dosimetry in prostate brachytherapy.

BACKGROUND AND PURPOSE: To compare the CT-based and CT/MRI fusion-based postimplant dosimetry after permanent prostate brachytherapy and to evaluate the improvement in CT-based dosimetry by physicians with or without experience in using the CT/MRI fusion method. PATIENTS AND METHODS: Thirty-eight consecutive patients agreed to participate in a prospective study. The prostate contours from CT/MRI fusion are the gold standard for determining the prostate volume and dose volume histogram (DVH). CT-based postimplant dosimetries were performed by two physicians. Observer 1 was a radiologist who had never used CT/MRI fusion method for postimplant dosimetric analysis. Observer 2 was a radiation oncologist experienced in postimplant analysis using the CT/MRI fusion method. The prostate dosimetry was evaluated by prostate D90 and V100. RESULTS: No significant difference was observed in the mean prostate volumes between the two observers and the CT/MRI fusion data. However, the correlation coefficient value for observer 2 (R(2)=0.932) was greater than that for observer 1 (R(2)=0.793). The D90 and V100 values as evaluated by the two observers were significantly underestimated in comparison to those evaluated using the CT/MRI fusion methods. The DVH related parameters were underestimated more frequently by observer 1 than by observer 2: (prostate D90: 99.56% for observer 1, 102.97% for observer 2, 109.37% for CT/MRI fusion. Prostate V100: 88.12% for observer 1, 90.14% for observer 2, 91.91% for CT/MRI fusion). CONCLUSIONS: The difference in the mean value in D90 and V100 by observer 1 was significantly greater than that for observer 2. These findings suggest that the CT/MRI fusion method provides accurate feedback which thereby improves CT-based postimplant dosimetry for prostate brachytherapy.

Brachytherapy↗
PubMed2006

Comparison of MRI-based and CT/MRI fusion-based postimplant dosimetric analysis of prostate brachytherapy.

PURPOSE: The aim of this study was to compare the outcomes between magnetic resonance imaging (MRI)-based and computed tomography (CT)/MRI fusion-based postimplant dosimetry methods in permanent prostate brachytherapy. METHODS AND MATERIALS: Between October 2004 and March 2006, a total of 52 consecutive patients with prostate cancer were treated by brachytherapy, and postimplant dosimetry was performed using CT/MRI fusion. The accuracy and reproducibility were prospectively compared between MRI-based dosimetry and CT/MRI fusion-based dosimetry based on the dose-volume histogram (DVH) related parameters as recommended by the American Brachytherapy Society. RESULTS: The prostate volume was 15.97+/-6.17 cc (mean+/-SD) in MRI-based dosimetry, and 15.97+/-6.02 cc in CT/MRI fusion-based dosimetry without statistical difference. The prostate V100 was 94.5% and 93.0% in MRI-based and CT/MRI fusion-based dosimetry, respectively, and the difference was statistically significant (p=0.002). The prostate D90 was 119.4% and 114.4% in MRI-based and CT/MRI fusion-based dosimetry, respectively, and the difference was statistically significant (p=0.004). CONCLUSION: Our current results suggested that, as with fusion images, MR images allowed accurate contouring of the organs, but they tended to overestimate the analysis of postimplant dosimetry in comparison to CT/MRI fusion images. Although this MRI-based dosimetric discrepancy was negligible, MRI-based dosimetry was acceptable and reproducible in comparison to CT-based dosimetry, because the difference between MRI-based and CT/MRI fusion-based results was smaller than that between CT-based and CT/MRI fusion-based results as previously reported.

Brachytherapy↗
PubMed2006

Random and sequential copolypeptides containing O-phospho-L-threonine and L-aspartic acid; roles in CaCO3 biomineralization.

The present study describes the synthesis of novel polypeptides containing O-phospho-L-threonine [Thr(PO(3)H(2))] and L-aspartic acid. Random copolypeptides copoly[Thr(PO(3)H(2))(X)Asp(Y)] (X:Y = 25:75, 50:50, 75:25), were conventionally prepared by copolymerization of Thr(PO(3)Ph(2)) N-carboxyanhydride (NCA) and Asp(OBzl) NCA followed by deprotection of the phenyl and benzyl groups by catalytic hydrogenolysis over PtO(2). Polycondensation of the protected peptide p-nitrophenyl esters [Thr(PO(3)Ph(2))](Z)-Asp(OBzl)-ONp and subsequent deprotection yielded the sequential polypeptides poly[Thr(PO(3)H(2))(Z)-Asp] (Z = 1-4). By using the synthetic polypeptides, their effects on the growth of CaCO(3) crystals were examined. In the poly[Thr(PO(3)H(2))(Z)-Asp]/CaCO(3) systems, brushlike calcite and spherical vaterite were formed, with the former being found at [Ca(2+)]/[Res] ratios of > or =180, > or =140, > or =120, and > or =100 for Z = 1, 2, 3, and 4, respectively. These results indicate that an increase of Thr(PO(3)H(2)) residues in the repetitive unit induces the characteristic brushlike calcite, a fact indicating that Thr(PO(3)H(2)) residues can modify the CaCO(3) crystal morphology.

Amino Acid Sequence↗
PubMed2005

Aerobic biodegradation behavior of nonylphenol polyethoxylates and their metabolites in the presence of organic matter.

In this paper, the aerobic biodegradation behavior of nonylphenol polyethoxylates (NPnEOs) with ethoxy (EO) units of specific lengths, which were fractionated using high-performance liquid chromatography(HPLC) with photodiode array detection, was studied in the presence of different types of organic materials. NPnEOs and their related metabolites under a modified OECD 301E biodegradation test were monitored using liquid chromatography/mass spectrometry (LC/MS) and gas chromatography/mass spectrometry (GC/MS). Biodegradation tests in the presence of organic matters, such as methanol, glucose, and yeast extract, showed the formation of the corresponding nonylphenol polyethoxy carboxylates by the oxidation of the terminal alcoholic group. However, aerobic biodegradation tests without organic matter revealed that NP2EO and NP3EO were predominant metabolites of the long-chain-oligomer precursor system which undergo fast and complete shortening. Degradation rates were higher for the long-chain oligomers than for shorter ones. The degradation pathway of NPnEOs was greatly influenced by the presence or absence of organic matter. Organic materials such as those given above apparently play a significant role in the formation of the carboxylated metabolites of NPnEOs.

Aerobiosis↗
PubMed2003

Biological activities and pore formation of Clostridium perfringens beta toxin in HL 60 cells.

Clostridium perfringens beta toxin is an important agent of necrotic enteritis. Of the 10 cell lines tested, only the HL 60 cell line was susceptible to beta toxin. The toxin induced swelling and lysis of the cell. Treatment of the cells with the toxin resulted in K+ efflux from the cells and Ca2+, Na+, and Cl- influxes. These events reached a maximum just before the cells were lysed by the toxin. Incubation of the cells with the toxin showed the formation of toxin complexes of about 191 and 228 kDa, which were localized in the domains that fulfilled the criteria of lipid rafts. The complex of 228 kDa was observed until 30 min after incubation, and only the complex of 191 kDa was remained after 60 min. Treatment of the cells with methyl-beta-cyclodextrin or cholesterol oxidase blocked binding of the toxin to the rafts and the toxin-induced K+ efflux and swelling. The toxin-induced Ca2+ influx and morphological changes were inhibited by an increase in the hydrodynamic diameter of polyethylene glycols from 200 to 400 and markedly or completely inhibited by polyethylene glycol 600 and 1000. However, these polyethylene glycols had no effect on the toxin-induced K+ efflux. The toxin induced carboxyfluorescein release from phosphatidyl-choline-cholesterol liposomes containing carboxyfluorescein and formed an oligomer with 228 kDa in a dose-dependent manner but did not form an oligomer with the 191-kDa complex. We conclude that the toxin acts on HL 60 cells by binding to lipid rafts and forming a functional oligomer with 228 kDa.

Amino Acid Sequence↗
PubMedDate not supplied

Migration of prostate brachytherapy seeds to the vertebral venous plexus.

PURPOSE: We report two cases of seed migration to the vertebral venous plexus after iodine-125 (I-125) transperineal interstitial permanent prostate brachytherapy. METHODS AND MATERIALS: Case 1: A 67-year-old Japanese man underwent percutaneous transperineal interstitial permanent prostate brachytherapy at our institution. Three months after brachytherapy, routine followup kidney-urinary bladder (KUB) radiography showed two seeds that had migrated to the pelvic area and were overlapped by sacral bone. It was very difficult to detect the seeds by visceral CT, because seeds were in contact with to vertebral bone, and seeds and bone were of the same CT value in visceral CT. But bone CT could distinguish seeds and bone, and it showed seed migration to the vertebral venous plexus in the sacral vertebral canal. Case 2: A 75-year-old Japanese man underwent percutaneous transperineal interstitial permanent prostate brachytherapy at our institution. The day after seed implantation, routine followup KUB radiography showed that a seed had migrated to the pelvic area and was overlapped by sacral bone. Bone CT clearly showed seed migration to the vertebral venous plexus in the vertebral canal in comparison with visceral CT. RESULTS: Seeds that have migrated to the vertebral venous plexus are difficult to be detected by visceral CT or KUB radiography. In visceral CT, it is difficult to distinguish seed and bone, especially when they are touching each other because they have the same CT value in visceral CT. It is therefore necessary to perform bone CT to detect such migrating seeds. CONCLUSIONS: To our knowledge, this is the first report of seed migration to the vertebral venous plexus after prostate brachytherapy. We thought that seeds migrate to the vertebral plexus via the pelvic venous pathway. If seed migration to the pelvic area and the overlapped sacral bone area is found after brachytherapy, bone CT should be performed, especially when it is difficult to detect the seed in visceral CT.

Adenocarcinoma↗
PubMedDate not supplied

Reirradiation with local-field radiotherapy for painful bone metastases.

PURPOSE: The purpose of this study was to evaluate retrospectively the effectiveness, prognostic factors, and sequelae of the first course of local-field reirradiation for painful bone metastases. PATIENTS AND METHODS: From 1994 to 2000, a total of 30 patients were reirradiated for painful bone metastases. The most commonly used initial treatment regimen was 30 Gy/10 Fr/2 wk. An additional dose in the range from 10 Gy/5 Fr to 26 Gy/13 Fr was reirradiated. RESULTS: Fifteen patients (50%) showed some type of pain relief after reirradiation. Patients with initial CR were more likely to respond than those with previous PR (100% vs. 41%). The median duration of pain relief was five months. The duration of response was longer in initial CR than initial PR. The median survival time of responders after retreatment was 11 months. No patient developed radiation myelopathy. Prognostic factors for pain relief were duration from initial treatment, performance status (PS), and status of bone metastases. CONCLUSION: Reirradiation for patients with a long duration from initial treatment (> or = 4 months), good PS (ECOG: 1-2), or solitary bone metastases was effective for pain relief. The appropriate indications, optimal dose, fractions, and technique for reirradiation to painful bone metastases should be further explored in randomized study.

Adult↗