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Biomedical subjects

Hiroshi Onishi

Publications and source records attributed to Hiroshi Onishi.

At least 19 recordsLinked to original sources
PubMed2006

Dosimetric verification in participating institutions in a stereotactic body radiotherapy trial for stage I non-small cell lung cancer: Japan clinical oncology group trial (JCOG0403).

A multicentre phase II trial of stereotactic body radiotherapy for T1N0M0 non-small cell lung cancer was initiated in Japan as the Japan Clinical Oncology Group trial (JCOG0403). Before starting the trial, a decision was made to evaluate the treatment machine and treatment planning in participating institutions to minimize the variations of the prescription dose between the institutions. We visited the 16 participating institutions and examined the absolute dose at the centre of a simulated spherical tumour of 3.0 cm diameter in the lung using the radiation treatment planning systems in each institution. A lung phantom for stereotactic body radiotherapy (SBRT) was developed and used for the treatment planning and film dosimetry. In the JCOG radiotherapy study group, the no model-based calculation algorithm or the model-based calculation algorithm with a dose kernel unscaled for heterogeneities were selected for use in the initial SBRT trials started in 2004, and the model-based calculation algorithm with a dose kernel scaled for heterogeneities was selected for the coming trial. The findings of this study suggest that the clinical results of lung SBRT trials should be carefully evaluated in comparison with the actual dose given to patients.

Algorithms↗
PubMed2006

Local work function of Pt clusters vacuum-deposited on a TiO2 surface.

Surface topography and work function maps were simultaneously obtained for Pt-evaporated titanium dioxide (TiO(2)) surfaces by using a Kelvin probe force microscope (KPFM). Platinum clusters with diameters of 2-3 nm and heights of 0.2-0.4 nm were obtained on rutile TiO(2)(110)-(1 x 1) surfaces. The work function on the Pt clusters was smaller than that on the surrounding TiO(2) surface. With the assumption that the work function was perturbed by electric dipole moments created at the Pt-TiO(2) interface, the work function decrease indicates that dipole moments were created at the interface and directed toward the vacuum. Such dipole moments can be formed by electron transfer from the originally neutral Pt atoms to the Ti cations exposed on the (1 x 1) surface. A simple model is constructed by assuming a uniform dipole moment per unit interface area. Using this model, the size-dependent perturbation of the work function can be interpreted. The electrostatic potential is more perturbed above the Pt clusters with a larger interface area since the number density of dipole moments is equal to that of the Ti cations and is uniform. A similar correlation between the work function decrease and interface area was observed for the clusters formed on terraces and on step edges. The work function maps showed no peculiar contribution for Ti atoms exposed at the step edges. Vacuum annealing caused a considerable change in the work function on the clusters. The work function was decreased on some clusters relative to the TiO(2) substrate, while it increased on the other clusters. The atomistic structure of the interface may be modified upon annealing, thus perturbing the electron transfer across the interface.

Journal Article↗
PubMed2006

Postoperative radiotherapy for patients with prostate cancer in Japan; Changing trends in national practice between 1996-98 and 1999-2001: Patterns of care study for prostate cancer.

OBJECTIVE: To evaluate the changing trends of standards and practices for postoperative radiotherapy (RT) for patients with prostate cancer in Japan. METHODS: The Japanese Patterns of Care Study (PCS) conducted a national survey in 84 institutions from 1996 to 1998 (PCS96-98) and 76 institutions from 1999 to 2001 (PCS99-01). Detailed information relevant to RT was collected on a total of 169 patients (64 from 1996 to 1998 and 105 from 1999 to 2001) with prostate cancer who had undergone radical prostatectomy. RESULTS: The fraction of clinical T3-4 tumours before prostatectomy decreased from 63% in the period 1996-98 to 26% in the period 1999-2001 (P = 0.0004). The pre-RT prostate-specific antigen level was significantly lower in 1999-2001 than in 1996-98 (P = 0.0002). We did not find a significant difference in the percentage of patients who received pelvic irradiation in the time periods between PCS96-98 and PCS99-01 (P = 0.18). Although the median radiation doses of 60 Gy were not changed between the surveys, various doses (from 20 to 74.6 Gy) were delivered to the prostatic bed. In the 1999-2001 survey, 73 of 105 patients received a median dose of 56 Gy in an adjuvant setting, while the other 32 received a median dose of 60 Gy in a salvage setting (P = 0.0015). CONCLUSION: These data suggest that consensus has not been reached on the practice and management of postoperative RT for patients with prostate cancer in Japan.

Adult↗
PubMed2006

Probe microscope observation of platinum atoms deposited on the TiO2(110)-(1 x 1) surface.

Titanium dioxide (TiO2) (110) surfaces with Pt adatoms were examined using a noncontact atomic force microscope (NC-AFM) and a Kelvin probe force microscope (KPFM). Topographic images with NC-AFM identify Pt atoms adsorbed at three different sites. These sites are on the Ti atom rows, on the O atom rows, and in O atom vacancies. Most Pt adatoms were observed on Ti atom rows. Successively recorded images show that the Pt adatoms on Ti atom rows (adatoms A) and O atom rows (adatoms C) are mobile while the adatoms in the O atom vacancies (adatoms B) are not. Adatoms A and adatoms B were identified in KPFM images. However, adatoms C were not visualized in KPFM images because they moved quickly or were swept out by the tip. The KPFM measurements reveal that the work function on adatoms A are lower than that on the surrounding (1 x 1) surface by 0.24 eV whereas adatoms B reduced the work function by 0.26 eV. The work function decrease is interpreted with an electric dipole moment directed toward the vacuum, as a result of electron transfer from the adatoms to the TiO2 substrate. In an O atom vacancy, the adatom B is in contact with two Ti atoms and therefore the electron transfer can be enhanced.

Journal Article↗
PubMed2006

Molecular vibrations at a liquid-liquid interface observed by fourth-order Raman spectroscopy.

Interface-selective, Raman-based observation of molecular vibrations is demonstrated at a liquid-liquid interface. An aqueous solution of oxazine 170 dye interfaced with hexadecane is irradiated with pump and probe light pulses of 630-nm wavelengths in 17-fs width. The ultrashort pulses are broadened due to group velocity dispersion when traveling through the hexadecane layer. The dispersion is optically corrected to give an optimized instrumental response. The pump pulse induces a vibrational coherence of the dye via impulsive stimulated Raman scattering. The probe pulse generates second-harmonic light at the interface. The efficiency of the generation is modulated as a function of the pump-probe delay by the coherently excited molecules. Fourier transformation of the modulated efficiency presents the frequency spectrum of the vibrations. Five bands are recognized at 534, 557, 593, 619, and 683 cm(-1). The pump-and-probe process induces a fourth-order optical response that is forbidden in a centrosymmetric media. The contribution of an undesired, cascaded optical process is quantitatively considered and excluded.

Alkanes↗
PubMed2006

Time-resolved infrared spectroscopy of K3Ta3B2O12 photocatalysts for water splitting.

Electrons photoexcited in K(3)Ta(3)B(2)O(12), an efficient photocatalyst for the water-splitting reaction driven by ultraviolet light, were observed using time-resolved IR absorption spectroscopy with microsecond resolution. When the catalyst was irradiated with 266 nm light pulses, a structureless absorption appeared at 3000-1500 cm(-1). The absorption was assigned to the optical transition of electrons that were band gap-excited and then trapped in mid-gap states. The absorbance decayed with a time delay because of the electron-hole recombination. The rate of recombination in an argon atmosphere was sensitive to the composition of the starting material used in the catalyst preparation. The electron decay was accelerated by exposing the catalyst to water vapor. The degree of acceleration was qualitatively correlated with the H(2) production rate observed during steady-state light irradiation.

Journal Article↗
PubMed2006

AFM observation of immobilized self-oscillating polymer.

Various types of nanocomponents have been developed to construct a nanodevice or nanomachine. Here, we add a new nanocomponent that has the function of self-oscillation. A thermoresponsive polymer carrying a Ru complex, a catalyst of the Belousov-Zhabotinsky reaction, was synthesized and immobilized on a glass plate. Periodic turbidity changes in the aqueous solution of the polymer were observed, and nanoscale self-oscillation of the immobilized polymer was observed by a scanning probe microscope.

Catalysis↗
PubMed2006

STM observation of a ruthenium dye adsorbed on a TiO2(110) surface.

Individual Ru(4,4'-dicarboxy-2,2'-bipyridine)2(NCS)2 molecules, commonly known as N3, adsorbed on a TiO2 surface were visualized with a scanning tunneling microscope (STM) operated in ultrahigh vacuum. A TiO2(110)-(1 x 1) crystal was taken out from the vacuum vessel and immersed into an acetonitrile solution of N3. A monolayer of pivalate ((CH3)3CCOO-) ions was used to protect the (1 x 1) surface from contamination during the wetting process of the N3 adsorption. The N3 molecules adsorbed on the flat terraces protruded by 0.65 nm from the pivalate monolayer. The image height difference of the admolecules could be understood with the assumption that the N3 molecules anchor to the TiO2 surface via two carboxyl groups. The number density of the N3 molecules on the steps was higher than that on the terraces. The poorly coordinated Ti atoms exposed at the step edges form preferential sites where the carboxyl groups can approach, due to a lower steric obstacle or because the structure of the adsorbed N3 molecules suffers less distortion.

Journal Article↗
PubMed2006

Radical external beam radiotherapy for prostate cancer in Japan: results of the 1999-2001 patterns of care process survey.

BACKGROUND: The Patterns of Care Study evaluated standards of practice for patients with clinically localized prostate cancer treated with radiotherapy in Japan. This study examined the influence of institutional stratification on care for patients receiving radical external beam radiotherapy. METHODS: A national survey of 66 institutions was conducted using two-stage cluster sampling, and detailed information was accumulated on 283 patients who received radiotherapy between 1999 and 2001. RESULTS: In A (academic) and B (non-academic) institutions, more than 80% of patients had intermediate or unfavorable risk disease. Although there were no significant differences in disease characteristics between A and B institutions, institutional stratification significantly affected radiotherapy practice patterns, such as the use of a CT-based treatment planning (A1: 91.5%, B: 77.1%; P = 0.0007) and the use of conformal therapy (A: 56.4%, B: 24.1%; P < 0.0001). CT-based treatment planning and conformal therapy significantly influenced total radiation dose (P < 0.0001 for each). Hormonal therapy was commonly used in both A and B institutions (A: 89.0%, B: 90.7%). Many patients with a favorable prognosis (A: 62.5%, B: 91.7%) received hormonal therapy, and most patients with unfavorable risk disease (A: 93.6%, B: 91.6%) also received hormonal therapy. CONCLUSION: During the period 1999-2001, the majority of prostate cancer patients treated in Japan with radical external beam radiotherapy had advanced diseases. Institutional stratification significantly affected radiotherapy practice patterns, with the notable exception that radiotherapy was commonly combined with hormonal therapy regardless of the institutional stratification and individual risk.

Aged↗
PubMed2005

Photochemical reaction of trimethyl acetate on Pt/TiO2(110).

Nanometer-sized Pt particles were prepared on an atomically flat surface of rutile TiO(2). Trimethyl acetate (TMA) adsorbed on the Pt-modified surface was photochemically decomposed under ultraviolet light irradiation in a vacuum. Residing TMA anions were imaged by a scanning tunneling microscope to deduce the local rate of decomposition. Increasing the number density of Pt particles led to an enhancement of the initial reaction rate. The degree of this enhancement did not depend on the distance from the Pt particles.

Journal Article↗
PubMed2005

Fourth-order Raman spectroscopy of wide-band gap materials.

Low-frequency surface vibrations were observed on a rutile TiO(2)(110) surface covered with trimethyl acetate (TMA) by using fourth-order Raman spectroscopy. The TMA-covered surface interfaced to air was irradiated with 18-fs light at a wavelength of 630 nm. A pump pulse excited vibrational coherence of Raman-active modes and a probe pulse interacts with the coherently excited surface to generate second harmonic light (315 nm), the intensity of which oscillated as a function of the pump-probe delay. Four bands were recognized at 180, 357, 444, and 826 cm(-1) in the Fourier transformation spectrum of the oscillation and assigned to bulk phonons modified by the presence of the surface boundary condition. The Raman transition for the pump was nonresonant to the band gap excitation of TiO(2), as evidenced by the oscillation phase relative to the pump irradiation and by the oscillation amplitude as a function of the pump power. The observable range of this surface-selective spectroscopy is extended to wide-band gap materials on which one-photon resonance enhancement of the Raman-pump efficiency cannot be expected.

Journal Article↗
PubMed2004

Stereotactic hypofractionated high-dose irradiation for stage I nonsmall cell lung carcinoma: clinical outcomes in 245 subjects in a Japanese multiinstitutional study.

BACKGROUND: Stereotactic irradiation (STI) has been actively performed using various methods to achieve better local control of Stage I nonsmall cell lung carcinoma (NSCLC) in Japan. The authors retrospectively evaluated results from a Japanese multiinstitutional study. METHODS: Patients with Stage I NSCLC (n = 245; median age, 76 years; T1N0M0, n = 155; T2N0M0, n = 90) were treated with hypofractionated high-dose STI in 13 institutions. Stereotactic three-dimensional treatment was performed using noncoplanar dynamic arcs or multiple static ports. A total dose of 18-75 gray (Gy) at the isocenter was administered in 1-22 fractions. The median calculated biologic effective dose (BED) was 108 Gy (range, 57-180 Gy). RESULTS: During follow-up (median, 24 months; range, 7-78 months), pulmonary complications of National Cancer Institute-Common Toxicity Criteria Grade > 2 were observed in only 6 patients (2.4%). Local progression occurred in 33 patients (14.5%), and the local recurrence rate was 8.1% for BED > or = 100 Gy compared with 26.4% for < 100 Gy (P < 0.05). The 3-year overall survival rate of medically operable patients was 88.4% for BED > or = 100 Gy compared with 69.4% for < 100 Gy (P < 0.05). CONCLUSIONS: Hypofractionated high-dose STI with BED < 150 Gy was feasible and beneficial for curative treatment of patients with Stage I NSCLC. For all treatment methods and schedules, local control and survival rates were better with BED > or = 100 Gy compared with < 100 Gy. Survival rates in selected patients (medically operable, BED > or = 100 Gy) were excellent, and were potentially comparable to those of surgery.

Adult↗
PubMed2004

Long-term results of radiotherapy for intracranial germinoma: a multi-institutional retrospective review of 126 patients.

PURPOSE: Optimal management of radiotherapy (RT) for intracranial germinoma remains controversial. This study was conducted to evaluate the long-term results of RT in patients with these tumors. METHODS AND MATERIALS: The study group consisted of 126 patients with intracranial germinoma (50 patients with pathologically verified germinoma and 76 clinically diagnosed with germinoma by clinical and neuroradiologic signs) who were treated by RT alone between 1980 and 2001. The median age at diagnosis was 17 years (range, 2-47), and various radiation doses and treatment fields were used. Serum human chorionic gonadotropin (hCG) levels were elevated in 18 patients. The median follow-up of the 114 surviving patients was 122 months (range, 13-263). RESULTS: The 10-year actuarial overall survival and cause-specific survival rate for all patients was 90% and 95%, respectively. The 10-year actuarial cause-specific survival rate for patients with and without elevated hCG levels was 94%. Relapses were noted in 10 patients, 7 of whom died of the disease. No in-field relapses at primary sites were observed in 72 patients treated with total doses of 40-50 Gy. The incidence of spinal relapses was 4% (2 of 56) for patients treated with spinal irradiation and 3% (2 of 70) for those without spinal irradiation. After a median 10-year follow-up, 54 (92%) of 59 patients with tumors not involving the neurohypophyseal region and 42 (76%) of 55 patients with tumors involving the neurohypophyseal region had Karnofsky performance status scores of 90-100%. With regard to school education and occupation, 54 (92%) of 59 patients with tumors not involving the neurohypophyseal region and 39 (71%) of 55 patients with tumors involving the neurohypophyseal region were attending school or undertaking occupations. Hormonal replacement therapy was required in 50 (44%) of 114 surviving patients before RT; only 4 patients (4%), all with neurohypophyseal tumors, required hormonal replacement therapy after RT. Clinically evident severe neurocognitive dysfunctions were documented in 10 patients before RT, and no patients treated with total doses of <55 Gy developed apparent neurocognitive dysfunctions or other complications after RT. CONCLUSION: RT was a curative treatment for intracranial germinoma, and elevated serum hCG levels did not affect the prognosis of patients treated by RT alone. A total dose of 40-50 Gy to adequate treatment fields was effective in preventing intracranial relapse, and the incidence of spinal relapses was too low to warrant routine spinal irradiation. Karnofsky performance status scores, educational achievement, and the ability to work were generally good, particularly in patients with tumors that did not involve the neurohypophyseal region. Because most complications, such as hormonal deficiency and neurocognitive dysfunction, were documented before RT and newly diagnosed complications after RT were infrequent, the treatment toxicity faced by germinoma patients appears to be less than anticipated.

Adolescent↗
PubMed2004

Clinical outcomes of stereotactic radiotherapy for stage I non-small cell lung cancer using a novel irradiation technique: patient self-controlled breath-hold and beam switching using a combination of linear accelerator and CT scanner.

We have developed a novel irradiation technique for lung cancer that combines a linear accelerator and CT scanner with patient-controlled breath-hold and radiation beam switching. We applied this technique to stereotactic three-dimensional (3D) conformal radiotherapy for stage I non-small cell lung cancer (NSCLC) and evaluated the primary therapeutic outcomes. A total of 35 patients with stage I (15 IA, 20 IB) primary NSCLC (20 adeno, 13 squamous cell, and 2 others) were treated with this technique. Patients ranged from 65 to 92 years old (median, 78 years). Twenty-three (66%) patients were medically inoperable due to mainly chronic pulmonary disease or high age. Three-dimensional treatment plans were made using 10 different non-coplanar dynamic arcs. The total dose of 60 Gy was delivered in 10 fractions (over 5-8 days) at the minimum dose point in the planning target volume (PTV) using a 6 MV X-ray. After adjusting the isocenter of the PTV to the planned position by a unit comprising CT and linear accelerator, irradiation was performed under patient-controlled breath-hold and radiation beam switching. All patients completed the treatment course without complaint. Complete response (CR) and partial response (PR) rates were 8/35 (23%) and 25/35 (71%), respectively. Pulmonary complications of National Cancer Institute-Common Toxicity Criteria grade >2 were noted in three (9%) patients. During follow-up (range, 6-30 months; median, 13 months), two (6%) patients developed local progression and five (14%) developed distant or regional lymph node metastases. Two-year overall survival rates for total patients and medically operable patients were 58 and 83%, respectively. In conclusion, this new irradiation technique, utilizing patient-controlled radiation beam switching under self-breath-hold after precise alignment of the isocenter, allows safe high-dose stereotactic radiotherapy with sufficient margins around the CTV and reduced treatment times. Based on the initial results, excellent local control with minimal complications is expected for stage I NSCLC.

Aged↗
PubMed2004

[Outcomes of radiation therapy for maxillary sinus carcinoma].

PURPOSE: We evaluated the outcome of radiation therapy for maxillary sinus carcinoma treated in our institution. MATERIALS AND METHODS: From 1984 to 2001, 48 patients with maxillary sinus carcinoma were irradiated with or without chemotherapy and surgery. Patients ranged from 20-89 years of age (median, 68 years) and included 29 men and 19 women. The clinical T factors for these patients, according to the UICC classification (1997), were T2(n = 2), T3(n = 13), and T4(n = 29). Lymph node involvement was observed in 13 patients. The follow-upperiod ranged from 2.5 to 150 months (median, 25 months). The total radiotherapy dose ranged from 40 Gy to 72.8 Gy. Forty-three patients underwent surgery. Intra-arterial chemotherapy was delivered in 39 patients, and systemic chemotherapy was delivered in 7 patients. Fourteen patients were classified as "unresected" (radiation therapy with or without antrostomy), and 34 patients as "resected" (partial, total, or extended total maxillectomy with pre- or postoperativeirradiation). RESULTS: The 5-year overall survival rate(OS), cause-specific survival rate(CSS), and local control rate(LC) of all patients were 52%, 64%, and 75%, respectively. There was no significant difference between the "uaresected" and "resected" groups in OS, CSS, or LC. Local recurrence was observed in 12 patients. In the "resected" group, for local control, it was important to reduce viable tumor before maxillectomy. Preoperative > or = 60 Gy irradiation was considered to be effective to reduce tumor viability. CONCLUSION: There was no significant difference between the "unresected" and "resected" groups in OS, CSS, or LC. In the "resected" group, preoperative irradiation > or = 60 Gy was considered to be effective for local control. In radical treatment of maxillary sinus carcinoma, maxillectomy is not always necessary. Concurrent chemoradiation therapy with or without antrostomy is a reasonable treatment strategy.

Adult↗
PubMed2003

Photochemical charge transfer and trapping at the interface between an organic adlayer and an oxide semiconductor.

Identification of charge transfer and trapping sites on semiconducting oxide surfaces is of fundamental importance in furthering the field of heterogeneous photocatalysts. Using scanning tunneling microscopy, electron energy loss spectroscopy, and photodesorption, we observed both electron trapping and hole transfer events on the (110) surface of TiO2 rutile. UV irradiation of a saturated monolayer of trimethyl acetate (TMA) on TiO2(110) at room temperature resulted in hole transfer to the carboxylate group, followed by (CH3)3C-COO bond cleavage and desorption of CO2 and isobutene/isobutane. Hole transfer to TMA proceeded in the absence of a gas-phase electron scavenger (which is typically O2) because the accompanying photogenerated electrons could be trapped at the surface as Ti3+ cations bound to bridging OH groups. The extent of electron trapping, gauged by electron spectroscopy, correlated directly with the yields of photodesorption fragments resulting from the hole transfer channel. Charge at the Ti3+ sites was titrated in the dark via a reaction between O2 and the Ti3+-OH groups.

Journal Article↗