A dosimetric study on the  high dose rate Flexisource

High‐dose‐rate (HDR) brachytherapy is a popular modality for treating cancers of the prostate, cervix, endometrium, breast, skin, bronchus, esophagus, and head and neck as well as soft‐tissue sarcomas. Because of different source designs and licensing issues, there is a need for specific dosimetry dataset for each HDR source model. The main objective of the present work is to measure 2D relative dose distribution around a new prototype 192Ir source, referred to as IRAsource‐HDR, in PMMA phantom in the framework of AAPM TG‐43 and TG‐55 recommendations for radial distances of 0.5 cm to 4 cm. Radiochromic films (RCFs) Gafchromic EBT and HD‐810 were used for measurements. The dose rate constant, Λ, of the source was determined to be 1.084±4.6%,1.129±4.4%, and 1.112±0.8% cGyh−1normalU−1 using EBTRCF, HD‐810 RCF, and Monte Carlo (MC) simulation, respectively. The results obtained in this study are in good agreement with previously published data for HDR interstitial 192Ir‐HDR sources with a maximum discrepancy of ±4.5%. An acceptable agreement (within ±2%) between MC calculations and RCFs measurements showed that HD‐810 RCF dosimetry is as good as EBTRCF, within HDR brachytherapy, and justifies the use of specific data for this new source. These data could be used as a benchmark for dose calculations in the conventional brachytherapy treatment planning systems.PACS number(s): 87.56.bg

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“…In Fig. 7 the calculated 2D anisotropy function was compared with the reference data 13 , 14 , 15 , 16 …”

Section: Resultsmentioning

confidence: 99%

“…Difference between IRAsource model and other similar

^{192} Ir

‐HDR sources in common use 13 , 14 , 15 , 16 , 17 is listed in Table 1. All HDR sources have similar active length and active core diameter and are all encapsulated in stainless steel tubes.…”

Section: Methodsmentioning

confidence: 99%

Gafchromic film dosimetry of a new HDR brachytherapy source

Ayoobian

Asl

Poorbaygi³

et al. 2016

J Applied Clin Med Phys

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“…11, left and middle). We can note this test is performed by assuming a symmetrical source with respect to it transverse axis; however, that condition is not a realistic assumption and, of course, is not supported by the Monte Carlo simulations 10 , 42 , 43 . The last effect is produced by the cable perturbation of the water medium (9) .…”

Section: Discussionmentioning

confidence: 99%

“…In that case, if the vendors use the same angular resolution for both sides, they could obtain different results in the interpolation compared with the reference data. In this situation, the Lozano approach (42) could help the physicist in the choice of appropriate angles and radii to minimize the discrepancies.…”

Section: Discussionmentioning

confidence: 99%

Brachytherapy treatment planning commissioning: effect of the election of proper bibliography and finite size of TG‐43 input data on standard treatments

Valdés

Piriz

Lozano

2015

J Applied Clin Med Phys

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The aim of this work is to evaluate the performance of a commercial brachytherapy treatment planning system (TPS) with TG‐43 Vendors Input Data (VID), analyze possible discrepancies with respect to a proper reference source and its implications for standard treatments, and judge the effectiveness of certain widespread recommended quality controls to find potential errors related with the interpolations of TG‐43 VID tables. The TPS evaluated was a BrachyVision 8.6 loaded with TG‐43 VID for a VariSource high‐dose‐rate 192Ir source (Vs2000). The reference data chosen were the TG‐43 data published in the literature. In the first step, we compared TG‐43 VID with respect to the chosen reference data. Next, we used percent dose‐rate differences in a point array matrix to compare the outcomes of the TPS on standard treatment setup with respect to an in‐house developed program (MATLAB R2009a‐based) loaded with the chosen full TG‐43 reference data. The cases with major discrepancies were evaluated using the gamma‐index analysis. The comparison with the reference data indicated a lack of sample in the angles between near to the tip (between 165<θ<180) and cable (0<θ<15) of the F(r,θ)VID, which causes a dose underestimation of approximately 17% in the investigated points due to inaccurate interpolations. The differences over 2% encompassed approximately 17% of the surrounding source volume. These results have special relevance in treatment using one applicator with a few dwell steps or in Fletcher treatments where 10% dose underestimates were identified within the tumor or in organs at risk, respectively. Our results suggest that the differences found in the TPS under study are created by a lack of information on the angles in high‐gradient zones in the F(r,θ)VID, which generates important differences in dosimetric results. In contrast, the gamma analysis shows very good results (between 90% and 100% of passed points) in the analyzed treatments (one dwell and Fletcher). Further studies are required to exclude the possibility of finding noticeable effects in the DVH of treatment plans caused by the discrepancies here described. To achieve more strict control over the TPS dose‐rate calculation, we recommend using QA test thinking in a source with nonaxial symmetry, adding a control point on the angles of the high‐dose gradient zones (e.g., between 0° and 15° and between 165° and 180°). More studies are required to achieve full understanding of the clinical implication of such discrepancies.PACS number: 87.55.Qr

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“…It is important to state that in the past, many authors have applied the MC method to model HDR-brachytherapy seeds with several degrees of approximation and to calculate Kerma in a water-phantom: microSelectron microSelectron-v2r [12] (slightly different from Flexisource [2,11]. According to the literature on this subject, to calculate AD even closer to the seeds, authors frequently have resorted to data extrapolation [1].…”

Section: Introductionmentioning

confidence: 99%

Kerma and Photons Absorbed-Dose from Ir-192 HDR Seeds

Chesta

Poma

Donnell³

2014

EJB

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Precise calculations of absorbed dose (AD) are a difficult task involving physical phenomena such as emission, transport, and absorption of radiation. We used the Monte Carlo method to calculate Kerma as well as AD in water imparted by two different Ir-192 HDR brachytherapy seeds (Flexisource and microSelectron-v2) taking into account the AAPM TG-43 formalism and AAPM & ESTRO most recent reports recommendations. The aim of this work is to evaluate when can Kerma be used as a measurement of AD for this type of seeds. Thus, we analyse the behaviour of both quantities in whole space, putting special emphasis near the source surface. We carried out calculations using microvoxels to obtain high spatial resolution of data close to the source. We observed differences of up to 6 % between AD and Kerma within 1 mm around the seed, and less than 1 % in any other region of the phantom. This allows us to analyse build-up region for Ir-192 HDR brachytherapy seeds. As it will be further discussed in this paper, our results can be explained in terms of partial electronic equilibrium reached on different regions of the phantom. Both seeds showed common overall behaviour, providing generality to the conclusions drawn. The complete bearing of the radial dose function (defined in the TG43 formalism) as it traverses the surface of the seed is reported. Whenever comparisons are possible, our results are in agreement with those reported by other authors. Tables of radial dose function, including new data computed from AD rate (instead of Kerma rate), are presented.

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A dosimetric study on the high dose rate Flexisource

Cited by 61 publications

References 19 publications

Gafchromic film dosimetry of a new HDR brachytherapy source

Gafchromic film dosimetry of a new HDR brachytherapy source

Brachytherapy treatment planning commissioning: effect of the election of proper bibliography and finite size of TG‐43 input data on standard treatments

Kerma and Photons Absorbed-Dose from Ir-192 HDR Seeds

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