The phase-matching characteristic of a quasi-phase-matched second-harmonic generation in a periodic-lens sequence waveguide on z -face KTiOPO 4 (potassium titanyl phosphate) crystal was obtained by measuring, as a function of input optical wavelength, the intensity of frequency-doubled radiation. The fabricated waveguide is a kind of segmented domain-inverted waveguide of which grating pitch is 4 µ m. The phase-matching was observed in the fundamental wavelength region of 850-860 nm. The half-width of the peak around 854 nm is about 0.3 nm. The broadening of phase-matching in wavelength was explained using geometrical optics.
To obtain three kinds of tomograms at three different X-ray energy ranges simultaneously, we have constructed a triple-energy (TE) X-ray photon counter with a cooled cadmium telluride (CdTe) detector and three sets of comparators and microcomputers. X-ray photons are detected using the CdTe detector, and the event pulses produced using amplifiers are sent to three comparators simultaneously to regulate three threshold energies of 15, 33 and 50 keV. Using this counter, the energy ranges are 15-33, 33-50 and 50-100 keV; the maximum energy corresponds to the tube voltage. We performed TE computed tomography (TE-CT) at a tube voltage of 100 kV. Using four lead pinholes, three tomograms were obtained simultaneously. Iodine-K-edge CT was carried out utilizing an energy range of 33-50 keV. At a tube voltage of 100 kV and a current of 0.11 mA, the count rate was 21 kilocounts per second (kcps).
In an x-ray diagnosis, it is important to evaluate the entrance dose rate, as the dose rate of exposure becomes highest in that position. To investigate the effect of the entrance dose rate of x-ray CT scanners, a dose-rate dosimeter comprising a silicon x-ray diode (Si-XD), a CMOS dual operational amplifier, resistors, capacitors, and a mini-substrate measuring 20 × 17 mm2 were developed. The Si-XD is desirable for measuring the changing entrance dose rate, as it enables the reduction of the response time, dimensions, and cost of the dosimeter. The dosimeter was connected to a microcomputer (mbed), and the output voltages from the dosimeter were measured using an analog–digital converter in the mbed. The output voltages were proportional to the tube currents at a constant tube voltage of 100 kV using an industrial x-ray tube, and the calibrated dose rates corresponded well to those obtained using a commercially available semiconductor dosimeter. However, owing to the energy dependence of the dosimeter, the calibrated dose rate was ∼10% higher than that of a commercially available semiconductor dosimeter at the lower tube voltage. In the angular dependence of the dosimeter, the flatness measured from 60° to 120° was ∼103% in this study. A fundamental study for measuring the dose-rate variations with rotation was performed. The results showed a different profile than the angular dependence due to the distance from the source and the complex factors of the scattered radiation.
To monitor patient-surface dose in intensity-modulated radiation therapy (IMRT), developed a novel capacitor dosimeter with a disposable USB-A mini-substrate consisting of a 0.22 μF capacitor and a silicon X-ray diode (Si-XD). The capacitor dosimeter consisted of a USB-A mini-substrate and a microcomputer dock. The capacitor in the substrate was charged to 3.30 V using the dock before 4 MV X-ray irradiation. The charging voltage was reduced by photocurrents flowing through the Si-XD during irradiation. After which the substrate was re-inserted into the dock, and the discharging voltage was measured. A Farmer-type ionization chamber (N30013, PTW) was used to convert the discharging voltages into absorbed dose (Gy). The IMRT study was performed using a custom-made head-neck phantom. The decrease in the charging voltage was found to be proportional to the X-ray dose, and the calibrated dose corresponded well to those obtained using the ionization chamber. The surface dose measured on the head-neck phantom were equivalent to those obtained from a treatment planning system. An inexpensive dosimeter with Si-XDs was developed, as a promising too. The results suggest for monitoring patient-surface dose during radiation therapy.
The Hospital for Special Surgery Pediatric Functional Activity Brief Scale (HSS Pedi-FABS) is a specifically designed scoring system for children and has been translated into several languages. However, to date, no validated Japanese version of this scoring system is available.To translate the HSS Pedi-FABS into Japanese and assess its reliability and validity.Cohort study (diagnosis); Level of evidence, 2.The HSS Pedi-FABS was translated into Japanese and back-translated into English to confirm the appropriateness of the translation. A total of 764 children aged 9 to 15 years participated in the validation study. The participants answered the Japanese version of the HSS Pedi-FABS along with 2 other questionnaires in Japanese (the Physical Activity Questionnaire for Older Children [PAQ-C] and the physical activity questionnaire of the World Health Organization's Health Behavior in School-aged Children [HBSC PAQ]). At 1 month after the first assessment, the children answered the Japanese version of the HSS Pedi-FABS again. We evaluated reliability using the Cronbach alpha and the intraclass correlation coefficient. Validity was evaluated by quantifying floor and ceiling effects, correlations between the HSS Pedi-FABS and the PAQ-C, the HSS Pedi-FABS discrepancy between active and inactive groups divided by the HBSC PAQ, and correlation between the HSS Pedi-FABS and body mass index.HSS Pedi-FABS scores were slightly but significantly higher in male participants (mean = 16.7) than in female participants (mean = 13.2). The Cronbach alpha coefficient was .90, and the intraclass correlation coefficient value was 0.90, indicating excellent internal consistency and test-retest reliability, respectively. No floor (2.6%) or ceiling effect (1.0%) was observed. The HSS Pedi-FABS was significantly correlated with the PAQ-C (r = 0.70). The active group demonstrated a significantly higher score on the HSS Pedi-FABS (mean = 18.9) than did the inactive group (mean = 11.2). In terms of discriminative validity, the HSS Pedi-FABS was not correlated with body mass index (r = -0.15).The Japanese version of the HSS Pedi-FABS demonstrated appropriate reliability and validity, indicating that it is a useful tool to assess physical activity levels in Japanese children.
