Commissioning of a respiratory gating system involving a pressure sensor in carbon-ion scanning radiotherapy.

This study reports the commissioning methodology and results of a respiratory gating system [AZ - 733 V/733 VI (Anzai Medical Co., Japan)] using a pressure sensor in carbon-ion scanning radiotherapy. Commissioning includes choosing a location and method for pressure sensor installation, delay time measurement of the system, and the final flow test. Additionally, we proposed a methodology for the determination of a threshold level of generating an on/off gate for the beam to the respiratory waveform, which is important for clinical application. Regarding the location and method for installation of the pressure sensor, the actual person's abdomen, back of the body position, and supine/prone positioning were checked. By comparing the motion between the pressure sensor output and the reference LED sensor motion, the chest rear surface was shown to be unsuitable for the sensor installation, due to noise in the signal caused by the cardiac beat. Regarding delay time measurement of the system, measurements were performed for the following four steps: (a). Actual motion to wave signal generation; (b). Wave signal to gate signal generation; (c). Gate signal to beam on/off signal generation; (d). Beam on/off signal to the beam irradiation. The total delay time measured was 46 ms (beam on)/33 ms (beam off); these were within the prescribed tolerance time (<100 ms). Regarding the final flow test, an end-to-end test was performed with a patient verification system using an actual carbon-ion beam; the respiratory gating irradiation was successfully performed, in accordance with the intended timing. Finally, regarding the method for determining the threshold level of the gate generation of the respiration waveform, the target motion obtained from 4D-CT was assumed to be correlated with the waveform obtained from the pressure sensor; it was used to determine the threshold value in amplitude direction.

Late rectal complications evaluated by computed tomography-based dose calculations in patients with cervical carcinoma undergoing high-dose-rate brachytherapy.

PURPOSE: To investigate the efficacy of dose calculations at the computed tomography (CT)-based rectal point (CTRP) as a predictive factor for late rectal complications in patients with cervical carcinoma who were treated with a combination of high-dose-rate intracavitary brachytherapy and external beam radiotherapy. METHODS AND MATERIALS: Ninety-two patients with uterine cervical carcinoma undergoing definitive radiotherapy alone were retrospectively analyzed. The median follow-up time for all patients was 32 months (range, 13-60 months). The cumulative biologically effective dose (BED) was calculated at the rectal reference point as defined by the International Commission on Radiation Units and Measurements Report 38 (BED(RP)) and at the CTRP (BED(CTRP)). Late rectal complications were recorded according to the Radiation Therapy Oncology Group grading system. RESULTS: The late rectal complications were distributed as follows: Grade 0, 68 patients (74%); Grade 1, 20 patients (22%); Grade 2, 4 patients (4%). Univariate analysis showed that BED(RP), BED(CTRP), RP dose/point A dose ratio, and CTRP dose/point A dose ratio were significantly correlated with late rectal complications (p < 0.05). On multivariate analysis, patients with a rectal BED(CTRP) >/=140 Gy(3) presented with significantly greater frequency of rectal complications (p = 0.031). CONCLUSIONS: The present results suggest that BED(CTRP) is a useful predictive factor for late rectal complications.

Measurement and analysis of reflex Responses to perturbation during walking-towards the realization of artificial reflex.

Reflex responses play an important role in gravity resistance, balance maintenance and the reaction to perturbation during human walking and standing upright. In this study, aiming at the realization of artificial reflex for paralyzed people, whose reflexive system was also impaired to a certain degree because of the weakened afferent neural pathway, the reflex responses of normal subjects were measured and analyzed. Not only the sensors for measuring muscle activation, but also the sensors for measuring body motion were employed. The spatiotemporal relation between muscle activity and body motion was qualitatively analyzed. Moreover, the candidates for artificial reflex triggering signal were identified for further investigation.

Fundamental study of an electric power transmission system for implanted medical devices using magnetic and ultrasonic energy.

In this paper, the authors propose a novel electric power supply system for implanted medical devices. The system is noninvasive and uses two kinds of energy, magnetic and ultrasonic. The system can provide high power levels harmlessly. The energies are obtained by two types of vibrator, i.e., piezo and magnetostriction devices. A prototype was built and it was verified experimentally that the system is basically able to provide power. At high frequencies, such as 100 kHz, the output power was higher than the conventional system using a transformer. The normalized output power per unit volume also exceeded the transformer system.