Search results for "Dose rate"
showing 10 items of 65 documents
High-dose-rate brachytherapy boost for prostate cancer: Analysis of dose-volume histogram parameters for predicting late, rectal toxicity
2017
PURPOSE: To determine the significance of dose-volume histogram parameters for predicting late rectal toxicity (LRT) after single-fraction high-dose-rate brachytherapy (HDRBT) boost and external beam radiotherapy (EBRT) in prostate cancer. MATERIALS AND METHODS: Three hundred patients with intermediate- or high-risk prostate cancer were included between August 2010 and March 2015. Treatment comprised a single-fraction HDRBT boost of 15.0 Gy plus EBRT (46.0 Gy delivered in 23 fractions) or an HDRBT boost of 9.5 Gy plus EBRT (60.0 Gy delivered in 30 fractions) if the seminal vesicles were infiltrated using real-time transrectal ultrasound-based planning. LRT was evaluated every 3 months after…
Focal or whole-gland salvage prostate brachytherapy with iodine seeds with or without a rectal spacer for postradiotherapy local failure: How best to…
2016
International audience; PURPOSE: Salvage prostate permanent implant (sPPI) for postradiation local failure provides high rates of biochemical control. The cumulative dose delivered to the prostate and the rectum is still unknown. METHODS AND MATERIALS: We reviewed the postimplant CT-based dosimetry of 18 selected patients who underwent sPPI with I-125 seeds for isolated biopsy-proven local failure several years after external beam radiation therapy. Ten patients had whole-prostate sPPI, and 8 patients had multiparametric MRI-based focal sPPI. In 8 patients, hyaluronic acid (HA) gel was injected into the prostate rectum space. RESULTS: The median cumulative biological effective dose after EB…
Interobserver variability in rectum contouring in high-dose-rate brachytherapy for prostate cancer: A multi-institutional prospective analysis
2017
PURPOSE: The aim of this study was to evaluate the interobserver variability (KW) of rectum contouring, and its dosimetric consequences, for high-dose-rate brachytherapy in patients with prostate cancer across multiple institutions. METHODS AND MATERIALS: Five radiation oncologists contoured rectums in 10 patients on transperineal ultrasound image sets after establishing a delineation consensus. The D-0.1cc, D-1cc, and D-2cc rectum volume parameters were determined. The mean, standard deviation, and range of each dose-volume histogram parameter were evaluated for each patient. The JOY was determined using the coefficient of variation, and the dosimetric impacts on the total dose were analyz…
Is high dose rate brachytherapy reliable and effective treatment for prostate cancer patients? A review of the literature.
2014
The intrinsic physical and radiobiological characteristics of High Dose Rate Brachytherapy (HDR-BT) are well suited to the treatment of prostate cancer. HDR-BT was initially used as a boost to external beam brachytherapy, but has subsequently been employed as the sole treatment, which is termed HDR monotherapy. This review summarizes the clinical outcomes and toxicity results of the principal studies and discusses the radiobiological basis supporting its use.
Ru-Based Thin Film Temperature Sensor for Space Environments: Microfabrication and Characterization under Total Ionizing Dose
2016
The paper shows the microfabrication processes of a Ruthenium-based resistance temperature detector and its behavior in response to irradiation at ambient temperature. The radiation test was done in a public hospital facility and followed the procedures based on the ESA specification ESCC 22900. The instrumentation system used for the test is detailed in the work describing the sensors resistance evolution before, during, and after the exposure. A total irradiation dose of 43 krad with 36 krad/h dose rate was applied and a subsequent characterization was performed once the Ru sensors were submitted to an 80°C annealing process during a period of 168 h. The experimental measurements have sho…
Limitations of the TG-43 formalism for skin high-dose-rate brachytherapy dose calculations
2014
Purpose: In skin high-dose-rate (HDR) brachytherapy, sources are located outside, in contact with, or implanted at some depth below the skin surface. Most treatment planning systems use the TG-43 formalism, which is based on single-source dose superposition within an infinite water medium without accounting for the true geometry in which conditions for scattered radiation are altered by the presence of air. The purpose of this study is to evaluate the dosimetric limitations of the TG-43 formalism in HDR skin brachytherapy and the potential clinical impact. Methods: Dose rate distributions of typical configurations used in skin brachytherapy were obtained: a 5 cm × 5 cm superficial mould; a …
Monte Carlo calculation of dose rate distributions around 0.5 and 0.6 mm in diameter 192Ir wires
1999
Monte Carlo simulations of absolute dose rate in liquid water are presented in the form of away-along tables for 1 and 5 cm 192 Ir wires of 0.5 and 0.6 mm diameter. Simulated absolute dose rate values can be used as benchmark data to verify the calculation results of treatment planning systems or directly as input data for treatment planning. Best fit value of an attenuation coefficient suitable for use in Sievert integral-type calculations has been derived based on Monte Carlo simulation results. For the treatment planning systems that are based on the TG43 formalism we have also computed the required dosimetry parameters.
A Monte Carlo study of intersource effects in dome-type applicators loaded with LDR Cs-137 sources
2005
In this study, the dose rate distributions produced by low dose rate Cs-137 sources loaded in afterloadable dome applicators are studied using the Monte Carlo method. Dose differences between Monte Carlo results and calculations done using the superposition principle are within 1-3% in front of the applicator and between 3 and 10% near and along the longitudinal source axis. Consequently, the real doses to lateral vaginal wall, rectum and bladder are very close to the doses estimated applying the superposition principle, while the dose to the vaginal cuff has been overestimated by up to 10%.
A monte carlo study of dose rate distribution around the specially asymmetric CSM3-a 137Cs source.
2001
The CSM3 137Cs type stainless-steel encapsulated source is widely used in manually afterloaded low dose rate brachytherapy. A specially asymmetric source, CSM3-a, has been designed by CIS Bio International (France) substituting the eyelet side seed with an inactive material in the CSM3 source. This modification has been done in order to allow a uniform dose level over the upper vaginal surface when this `linear' source is inserted at the top of the dome vaginal applicators. In this study the Monte Carlo GEANT3 simulation code, incorporating the source geometry in detail, was used to investigate the dosimetric characteristics of this special CSM3-a 137Cs brachytherapy source. The absolute do…
SU-F-T-63: Dosimetric Relevance of the Valencia and Leipzig HDR Applicators Plastic Cap
2016
Purpose: Utilization of HDR brachytherapy treatment of skin lesions using collimated applicators, such as the Valencia or Leipzig is increasing. These applicators are made of cup-shaped tungsten material in order to focalize the radiation into the lesion and to protect nearby tissues. These applicators have an attachable plastic cap that removes secondary electrons generated in the applicator and flattens the treatment surface. The purpose of this study is to examine the dosimetric impact of this cap, and the effect if the cap is not placed during the HDR fraction delivery. Methods: Monte Carlo simulations have been done using the code Geant4 for the Valencia and Leipzig applicators. Dose r…