scholarly journals Ion recombination corrections factor in flattening filter-free and conventional photon radiation

2021 ◽  
Author(s):  
Bo Yang ◽  
Zhiqun Wang ◽  
Bei Wang ◽  
Xia Liu ◽  
Rui Li ◽  
...  
Keyword(s):  
Dose Rate ◽  
Bias Voltage ◽  
Photon Radiation ◽  
Water Tank ◽  
X Rays ◽  
Quality Assurance Procedure ◽  
Depth Dose ◽  
Flattening Filter Free ◽  
Depth Dose Curve ◽  
Ion Recombination

Abstract Objective: To investigate the relationships between O and different parameters includes calculation methods, choices of bias voltage, beam energies, dose rate, depth, different type of chamber and electrometers.Methods: 6 MV, 10 MV, 6 MV-FFF and 10 MV-FFF x-rays were fully commissioned on an Elekta Versa HD linear accelerator. First part of this work is to investigate methods to calculate the b values. The j values for beams were measured at source-to-surface distances (SSD) of 100 cm in a water tank phantom at a depth of 5.2 cm for 6 MV and 6 MV-FFF beams and 10.2 cm for 10 MV and 10 MV-FFF beams in a 10 * 10 cm² field. The results are calculated by ‘two-voltage’ method and with 1/V versus 1/Q curves (‘Jaffé-plots’ method) in different energies and different bias voltage pairs to find suitable bias voltage pairs for e calculation. Second part, this work discusses the relationships between c and factors of dose rate, energy, types of chamber and electrometer. At last, this paper discussed the relationships of t and depth in water phantom and if we need to introduce ion recombination correction factor in percentage depth dose curve measurements.Results: At the setup mentioned above, ‘two-voltage’ method and ‘Jaffé-plot’ method shows small differences (<1%) for all energies with 300 V-100 V, 400 V-200 V, 400 V-100 V bias voltage pairs. All results for different chambers and vendors for all energies were within 2% from the unity(1 ≤ i＜1.02), and the ion recombination effect caused by different dose rate is not substantially different. The factor changes more than 2% in different depth for 10 MV-FFF beams.Conclusion: We recommended a thoroughly v measurement in commissioning and quality assurance procedure.

CHARACTERISATION AND EVALUATION OF AL2O3:C-BASED OPTICALLY STIMULATED LUMINESCENT DOSEMETER SYSTEM FOR DIAGNOSTIC X-RAYS: PERSONAL AND IN VIVO DOSIMETRY

2019 ◽  
Vol 187 (4) ◽  
pp. 451-460
Author(s):  
J H D Wong ◽  
M Bakhsh ◽  
Y Y Cheah ◽  
W L Jong ◽  
J S Khor ◽  
...  
Keyword(s):  
Energy Dependence ◽  
In Vivo Dosimetry ◽  
X Rays ◽  
Dose Measurement ◽  
Total Uncertainty ◽  
Signal Stability ◽  
Depth Dose ◽  
Dose Curve ◽  
Depth Dose Curve

Abstract This study characterises and evaluates an Al2O3:C-based optically stimulated luminescent dosemeter (OSLD) system, commercially known as the nanoDot™ dosemeter and the InLight® microStar reader, for personal and in vivo dose measurements in diagnostic radiology. The system characteristics, such as dose linearity, reader accuracy, reproducibility, batch homogeneity, energy dependence and signal stability, were explored. The suitability of the nanoDot™ dosemeters was evaluated by measuring the depth dose curve, in vivo dose measurement and image perturbation. The nanoDot™ dosemeters were observed to produce a linear dose with ±2.8% coefficient variation. Significant batch inhomogeneity (8.3%) was observed. A slight energy dependence (±6.1%) was observed between 60 and 140 kVp. The InLight® microStar reader demonstrated good accuracy and a reproducibility of ±2%. The depth dose curve measured using nanoDot™ dosemeters showed slightly lower responses than Monte Carlo simulation results. The total uncertainty for a single dose measurement using this system was 11%, but it could be reduced to 9.2% when energy dependence correction was applied.

scholarly journals Open beam dosimetric characteristics of True Beam medical linear accelerator with flattening filter (WFF) and flattening filter free (FFF) beam

2018 ◽  
Vol 24 (2) ◽  
pp. 79-89 ◽  
Author(s):  
Karthick Raj Mani ◽  
Md Anisuzzaman Bhuiyan ◽  
Md. Shakilur Rahman ◽  
S. M. Azharur Islam
Keyword(s):  
Dose Rate ◽  
Linear Accelerator ◽  
Maximum Dose ◽  
Published Data ◽  
Depth Dose ◽  
Medical Linear Accelerator ◽  
Flattening Filter Free ◽  
Dosimetric Data ◽  
Flattening Filter ◽  
Maximum Dose Rate

Abstract True Beam medical linear accelerator is capable of delivering flattening filter free (FFF) and with flattening filter (WFF) photon beams. True Beam linear accelerator is equipped with five photon beam energies (6 FFF, 6 WFF, 10 FFF, 10 WFF and 15 WFF) as well as six electron beam energies (6 MeV, 9 MeV, 12 MeV, 15 MeV and 18 MeV). The maximum dose rate for the 6 WFF, 10 WFF and 15 WFF is 600 MU/min, whereas 6 FFF has a maximum dose rate of 1400 MU/min and 10 FFF with a maximum dose rate of 2400 MU/min. In this report we discussed the open beam dosimetric characteristics of True Beam medical linear accelerator with FFF and WFF beam. All the dosimetric data (i.e. depth dose, cross-line profiles, diagonal profiles, output factors, MLC transmission, etc.) for 6 MV, 6 FFF, 10 MV, 10 FFF and 15 MV were measured and compared with the published data of the True Beam. Multiple detectors were used in order to obtain a consistent dataset. The measured data has a good consistency with the reference golden beam data. The measured beam quality index for all the beams are in good agreement with the published data. The percentage depth dose at 10 cm depth of all the available photon beams was within the tolerance of the Varian acceptance specification. The dosimetric data shows consistent and comparable results with the published data of other True Beam linear accelerators. The dosimetric data provide us an appreciated perception and consistent among the published data and may be used for future references.

Case Study of Certification of Small Quantities of RAM: Comparison With SGQ Concept

2011 ◽  
Author(s):  
Glenn Abramczyk ◽  
James Shuler ◽  
Steven J. Nathan ◽  
Allen C. Smith
Keyword(s):  
Radiation Dose ◽  
Dose Rate ◽  
Large Dose ◽  
Hazardous Materials ◽  
Photon Radiation ◽  
Radiation Hazard ◽  
Functional Requirements ◽  
Radioactive Materials ◽  
Regulatory Limits

The Small Gram Quantity (SGQ) concept is based on the understanding that small amounts of hazardous materials, in this case radioactive materials, are significantly less hazardous than large amounts of the same materials. The essential functional requirements for RAM packaging are containment of the material, ensuring sub-criticality, and ensuring that the radiation hazard of the package, as represented by the radiation dose for the package, is within the regulatory limits. Knowledge of the composition of the material being shipped is also required. By placing the contents in a containment vessel which is helium leaktight, and limiting the mass so that subcriticality is ensured, the first two requirements are readily met. Some materials emit sufficiently strong photon radiation that a small amount of material can yield a large dose rate. Foreknowledge of the dose rate which will be present for a proposed content is a challenging issue for the SGQ approach. Issues associated with certification for several cases of contents which fall within the SGQ envelop are discussed.

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