Control of optical absorption of silica glass by Ag ion implantation and subsequent heavy ion irradiation.

Silica glass samples were implanted with 50-380 keV Ag ions. After ion implantation, some samples were subsequently irradiated with 16 MeV Au ions. The effects of the implantation and the subsequent Au ion irradiation on the optical absorption spectra and morphologies of the Ag nanoparticles produced in the samples were studied by using an ultraviolet-visible scanning spectrophotometer and a transmission electron microscope, respectively. For the samples implanted with 200 keV or 380 keV Ag ions to high fluence, optical absorption peaks appeared around 600 nm, as well as the well-known surface plasmon resonance peaks around 400 nm, and Ag spherical nanoparticles with a high spatial density were observed. The absorption peaks around 600 nm are explained as being due to interactions between the Ag nanoparticles (inter-particle interaction). Under the subsequent irradiation with 16 MeV Au ions, the optical absorption around 400 and 600 nm showed a blue shift and the peak intensity markedly decreased. Transmission electron microscopy observation revealed an elongation of the Ag nanoparticles along the direction of the 16 MeV Au irradiation, and a resulting enlargement of the distances between the nanoparticles. The change in the peak wavelength and peak intensity of the optical absorption by the 16 MeV Au irradiation can, therefore, be explained as originating from a decrease in inter-particle interaction.

A liquid-helium-free superconducting coil system forming a flat minimum-magnetic-field distribution of an electron cyclotron resonance ion source.

A flat distribution of the minimum magnetic field (flat-Bmin) of an electron cyclotron resonance ion source (ECRIS) is expected to perform better in highly charged ion production than classical Bmin. To form a flat-Bmin structure with a liquid helium-free superconducting device, a coil system of seven coils with four current leads has been designed. The lead number was reduced by connecting the plural coils in series to maintain the flat-Bmin structure even when the coil currents are changed for adjustment. This coil system can be operated with a helium-free cryostat, since the estimation of heat from the leads to the coils is nearly equivalent to the existing superconducting ECRIS of a similar type.

Uncertainty in patient set-up margin analysis in radiation therapy.

We investigated the uncertainty in patient set-up margin analysis with a small dataset consisting of a limited number of clinical cases over a short time period, and propose a method for determining the optimum set-up margin. Patient set-up errors from 555 registration images of 15 patients with prostate cancer were tested for normality using a quantile-quantile (Q-Q) plot and a Kolmogorov-Smirnov test with the hypothesis that the data were not normally distributed. The ranges of set-up errors include the set-up errors within the 95% interval of the entire patient data histogram, and their equivalent normal distributions were compared. The patient set-up error was not normally distributed. When the patient set-up error distribution was assumed to have a normal distribution, an underestimate of the actual set-up error occurred in some patients but an overestimate occurred in others. When using a limited dataset for patient set-up errors, which consists of only a small number of the cases over a short period of time in a clinical practice, the 2.5% and 97.5% intervals of the actual patient data histogram from the percentile method should be used for estimating the set-up margin. Since set-up error data is usually not normally distributed, these intervals should provide a more accurate estimate of set-up margin. In this way, the uncertainty in patient set-up margin analysis in radiation therapy can be reduced.

Analysis of post-exposure density growth in radiochromic film with respect to the radiation dose.

The post-exposure density growth (PEDG) is one of the characteristics of radiochromic film (RCF). In film dosimetry using RCF and a flatbed scanner, pixel values read out from the RCF are converted to dose (hereafter, film dose) by using a calibration curve. The aim of this study is to analyze the relationship between the pixel value read out from the RCF and the PEDG, and that between the film dose converted from the RCF and the PEDG. The film (GAFCHROMIC EBT) was irradiated with 10-MV X-rays in an ascending 11-dose-step arrangement. The pixel values of the irradiated EBT film were measured at arbitrary hours using an Epson flatbed scanner. In this study, the reference time was 24 h after irradiation, and all dose conversions from the pixel values read out from the EBT film were made using a calibration curve for 24 h after irradiation. For delivered doses of 33 and 348 cGy, the measured pixel values at 0.1 and 16 h after irradiation represented ranges of -9.6% to -0.7% and -3.9% to -0.3%, respectively, of the reference value. The relative changes between the pixel values read out from the EBT film at each elapsed time and that at the reference time decreased with increasing delivered dose. However, the difference range for all the film doses had a width of approximately -10% of the reference value at elapsed times from 0.1 to 16 h, and it showed no dependence on the delivered dose.

Transmission of cluster ions through a tandem accelerator of several stripper gases.

The transmissions of carbon cluster ion beams through a tandem accelerator using several stripper gases (He, N2, CO2, and SF6) with a terminal voltage of 2.5 MV were measured as a function of the gas pressure in investigating the most suitable gas for cluster ion acceleration. This resulted in it being demonstrated that the highest transmission could be obtained using the smaller size gas, i.e., helium displayed the best performance of the four gases used. In addition, the ratio of transmissions of C(n) with helium and nitrogen increased with increases in the n, thus revealing that helium gas should prove the most effective in larger cluster ion acceleration using the same energy.

The prognostic value of carcinoembryonic antigen in T1N1M0 and T2N1M0 non-small cell carcinoma of the lung.

OBJECTIVE: To evaluate the significance of preoperative clinicopathological factors, including serum carcinoembryonic antigen (CEA), as well as postoperative clinicopathological factors in T1-2N1M0 patients with non-small cell lung cancer who underwent curative pulmonary resection. METHODS: Twenty T1N1M0 disease patients and 25 T2N1M0 patients underwent standard surgical procedures between September 1996 and December 2005, and were found to have non-small lung cancer. As prognostic factors, we retrospectively investigated age, sex, Brinkman index, histologic type, primary site, tumor diameter, clinical T factor, clinical N factor, pathological T factor, preoperative serum CEA levels, surgical procedure, visceral pleural involvement, and the status of lymph node involvement (level and number). RESULTS: The overall 5-year survival rate of all patients was 59.6%. In univariate analysis, survival was related to age (<70/>or=70 years, p=0.0079), site (peripheral/central, p=0.043), and CEA level (<5.0/>or=5.0 ng/ml, p=0.0015). However, in multivariate analysis, CEA (<5.0/>or=5.0 ng/ml) was the only independent prognostic factor; the 5-year survival of the patients with an elevated serum CEA level (>or=5.0 ng/ml) was only 33.2% compared to 79.9% in patients with a lower serum CEA level (<5.0 ng/ml). CONCLUSIONS: An elevated serum CEA level (>or=5.0 ng/ml) was an independent predictor of survival in pN1 patients except for T3 and T4 cases. Therefore, even in completely resected pN1 non-small cell lung cancer, patients with a high CEA level might be candidates for multimodal therapy.