The design of a new insert for calibration of LDR and HDR  sources in a well‐type ionization chamber

Pineda, A. E. C.; Alcón, Elmer P.Q.; deAlmeida, C. E.

doi:10.1118/1.1578773

Cited by 3 publications

(2 citation statements)

References 8 publications

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“…Aspects related to both condensed and mixed simulation schemes and reduction in computing time have been described by Salvat et al 21 This MC has been used extensively for simulation of brachytherapy sources. [22][23][24][25][26][27] Photons were simulated until their energy fell below 10 keV. At the energy used in this study, it has been verified previously 13 and in our own calculation that it is not necessary to follow the electrons.…”

Section: Iie the Monte Carlo "Mc… Modelsupporting

confidence: 59%

Determination of absorbed dose in water at the reference point for an HDR brachytherapy source using a Fricke system

Austerlitz¹,

Mota²,

Sempau³

et al. 2008

Medical Physics

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A ring-shaped Fricke device was developed to measure the absolute dose on the transverse bisector of a 192Ir high dose rate (HDR) source at 1 cm from its center in water, D(r0, theta0). It consists of a polymethylmethacrylate (PMMA) rod (axial axis) with a cylindrical cavity at its center to insert the 192Ir radioactive source. A ring cavity around the source with 1.5 mm thickness and 5 mm height is centered at 1 cm from the central axis of the source. This ring cavity is etched in a disk shaped base with 2.65 cm diameter and 0.90 cm thickness. The cavity has a wall around it 0.25 cm thick. This ring is filled with Fricke solution, sealed, and the whole assembly is immersed in water during irradiations. The device takes advantage of the cylindrical geometry to measure D(r0, theta0). Irradiations were performed with a Nucletron microselectron HDR unit loaded with an 192Ir Alpha Omega radioactive source. A Spectronic 1001 spectrophotometer was used to measure the optical absorbance using a 1 mL quartz cuvette with 1.00 cm light pathlength. The PENELOPE Monte Carlo code (MC) was utilized to simulate the Fricke device and the 192Ir Alpha Omega source in detail to calculate the perturbation introduced by the PMMA material. A NIST traceable calibrated well type ionization chamber was used to determine the air-kerma strength, and a published dose-rate constant was used to determine the dose rate at the reference point. The time to deliver 30.00 Gy to the reference point was calculated. This absorbed dose was then compared to the absorbed dose measured by the Fricke solution. Based on MC simulation, the PMMA of the Fricke device increases the D(r0, theta0) by 2.0%. Applying the corresponding correction factor, the D(r0, theta0) value assessed with the Fricke device agrees within 2.0% with the expected value with a total combined uncertainty of 3.43% (k=1). The Fricke device provides a promising method towards calibration of brachytherapy radiation sources in terms of D(r0, theta0) and audit HDR source calibrations.

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Section: Iie the Monte Carlo "Mc… Modelsupporting

confidence: 59%

Determination of absorbed dose in water at the reference point for an HDR brachytherapy source using a Fricke system

Austerlitz¹,

Mota²,

Sempau³

et al. 2008

Medical Physics

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“…As is apparent from its acronym, the code was first applied to the transport and dosimetry of high-energy electron beams (DesRosiers et al 2001. More recently, its applications have been broadened to include dosimetric problems related to high-energy photon beams (Mazurier et al 2001), 60 Co γ -beams (Moskvin et al 2002) and 192 Ir-HDR (high dose rate) brachytherapy (Pineda et al 2003). To our knowledge, however, no attempt has yet been made to benchmark PENELOPE for dosimetry of low-energy photons (a few keV to a few hundred keV).…”

Section: Penelopementioning

confidence: 99%

Benchmark of PENELOPE code for low-energy photon transport: dose comparisons with MCNP4 and EGS4

Brezovich

Pareek

et al. 2004

Phys. Med. Biol.

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The expanding clinical use of low-energy photon emitting 125I and 103Pd seeds in recent years has led to renewed interest in their dosimetric properties. Numerous papers pointed out that higher accuracy could be obtained in Monte Carlo simulations by utilizing newer libraries for the low-energy photon cross-sections, such as XCOM and EPDL97. The recently developed PENELOPE 2001 Monte Carlo code is user friendly and incorporates photon cross-section data from the EPDL97. The code has been verified for clinical dosimetry of high-energy electron and photon beams, but has not yet been tested at low energies. In the present work, we have benchmarked the PENELOPE code for 10-150 keV photons. We computed radial dose distributions from 0 to 10 cm in water at photon energies of 10-150 keV using both PENELOPE and MCNP4C with either DLC-146 or DLC-200 cross-section libraries, assuming a point source located at the centre of a 30 cm diameter and 20 cm length cylinder. Throughout the energy range of simulated photons (except for 10 keV), PENELOPE agreed within statistical uncertainties (at worst +/- 5%) with MCNP/DLC-146 in the entire region of 1-10 cm and with published EGS4 data up to 5 cm. The dose at 1 cm (or dose rate constant) of PENELOPE agreed with MCNP/DLC-146 and EGS4 data within approximately +/- 2% in the range of 20-150 keV, while MCNP/DLC-200 produced values up to 9% lower in the range of 20-100 keV than PENELOPE or the other codes. However, the differences among the four datasets became negligible above 100 keV.

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The effect of ambient pressure on well chamber response: Monte Carlo calculated results for the HDR 1000 Plus

et al. 2005

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The determination of the air kerma strength of a brachytherapy seed is necessary for effective treatment planning. Well ionization chambers are used on site at therapy clinics to determine the air kerma strength of seeds. In this work, the response of the Standard Imaging HDR 1000 Plus well chamber to ambient pressure is examined using Monte Carlo calculations. The experimental work examining the response of this chamber as well as other chambers is presented in a companion paper. The Monte Carlo results show that for low-energy photon sources, the application of the standard temperature pressure PTP correction factor produces an over-response at the reduced air densities/pressures corresponding to high elevations. With photon sources of 20 to 40 keV, the normalized PTP corrected chamber response is as much as 10% to 20% over unity for air densities/pressures corresponding to an elevation of 3048 m (10000 ft) above sea level. At air densities corresponding to an elevation of 1524 m (5000 ft), the normalized PTP-corrected chamber response is 5% to 10% over unity for these photon sources. With higher-energy photon sources (>100 keV), the normalized PTP corrected chamber response is near unity. For low-energy beta sources of 0.25 to 0.50 MeV, the normalized PTP-corrected chamber response is as much as 4% to 12% over unity for air densities/pressures corresponding to an elevation of 3048 m (10000 ft) above sea level. Higher-energy beta sources (>0.75 MeV) have a normalized PTP corrected chamber response near unity. Comparing calculated and measured chamber responses for common 103Pd- and 125I-based brachytherapy seeds show agreement to within 2.7% and 1.9%, respectively. Comparing MCNP calculated chamber responses with EGSnrc calculated chamber responses show agreement to within 3.1% at photon energies of 20 to 40 keV. We conclude that Monte Carlo transport calculations accurately model the response of this well chamber. Further, applying the standard PTP correction factor for this well chamber is insufficient in accounting for the change in chamber response with air pressure for low-energy (<100 keV) photon and low-energy (<0.75 MeV)beta sources.

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The design of a new insert for calibration of LDR and HDR sources in a well‐type ionization chamber

Cited by 3 publications

References 8 publications

Determination of absorbed dose in water at the reference point for an HDR brachytherapy source using a Fricke system

Determination of absorbed dose in water at the reference point for an HDR brachytherapy source using a Fricke system

Benchmark of PENELOPE code for low-energy photon transport: dose comparisons with MCNP4 and EGS4

The effect of ambient pressure on well chamber response: Monte Carlo calculated results for the HDR 1000 Plus

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