Dose verification of intensity modulated radiotherapy in head and neck tumors

Elawady, Rasha A.; Attalla, Ehab M.; Elshemey, Wael M.; Shouman, Tarek; Alsayed, Anwar A

doi:10.14319/ijcto.0203.7

Cited by 6 publications

(4 citation statements)

References 22 publications

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“…In the dose fluence map comparison of TPS and film, results were found between 87.7% and 95.5%. Elawady et al [18] reported, the agreement between measured with 2D-array and calculated doses for head and neck tumors using gamma criteria of 3% DD, 3 mm DTA and suppressing dose below 10%, the average and standard deviation for local dose of gamma index are 81.70 ± 6.28, while those for maximum dose of gamma index are 92.48 ± 4.60.…”

Section: Resultsmentioning

confidence: 91%

Pre-Treatment Dose Verification of Imrt Using Gafchromic Ebt3 Film and 2DArray

Nalbant¹,

N²,

Bilge³

2014

J Nucl Med Radiat Ther

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The present work deals with pre-treatment dosimetric verification of 10 prostate intensity-modulated radiotherapy (IMRT) plans obtained by Gafchromic EBT3 film and 2D-Array seven29 to establish quality control protocol for the delivery of prostate IMRT in our clinic. Methods: 10 prostate patients were irradiated according to IMRT techniques with 6 MV photon beams produced by a Varian DHX linear accelerator. Dose plans were computed using Eclipse 8.9 (version8.9, Varian, Palo Alto, CA, United States) treatment planning system (TPS). Pre-treatment dosimetric verification was carried out on field-perfield and total IMRT plan basis measuring 2D dose distributions in RW3 solid water phantom (PTW-Freiburg, Germany). For 10 patient plans, the dose distribution was re-calculated with the phantom CT scan and delivered to the phantom with the original and 0 degrees gantry, collimator and table angles. Thus IMRT quality control (QC) plans were generated. Dose distribution measurements were measured with Gafchromic EBT3 film and 2D-Array seven29 (PTW-Freiburg, Germany) two dimensional ionization chamber system. Verification measurements of total IMRT plans and each individual beams were compared with expected dose maps, and differences were evaluated by Verisoft program (PTW-Freiburg, Germany). To provide comparisons of multidimensional dose distributions, dose comparison tools such as gamma dose distribution, distance-to-agreement (DTA) and dose difference (DD) have been developed. The gamma dose distribution tool was used in our study. Three different gamma criteria of dose difference (DD) and distance to agreement (DTA) (3%/3 mm, 4%/4 mm and 5%/5 mm DD / DTA) are selected. These criteria are evaluated while suppressing the dose of 5% from dose distribution. Criterion validity accepted as section with gamma value less than or equal to 1 (γ ≤ 1) to be 90%. Results:In the comparison of dose distributions obtained from TPS and the results of PTW 2D-Array seven29 and Gafchromic EBT3 film dosimetry systems, it was showed that the compatibility of both methods were above 90% with respect to 3% DD and 3mm DTA criteria. PTW 2D-Array seven29 results compared to the results of the film was closer to the TPS data and this difference was statistically meaningful (p<0.05). If the range of criteria is increased, the compatibility increases and it reaches to 100%. It was observed that analyzing by measuring all fields which are composing IMRT plans and analyzing by measuring each individual fields at the same time, made no statistically meaningful difference (p>0.05). Conclusions:The measurements performed with PTW 2D-Array seven29 were closer to the TPS data than film measurements and it takes less time during clinical use, so it could be preferred for routine use. The present results suggest the gamma criteria of 3%/3 mm as the most suitable criteria for prostate IMRT quality assurance.

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Section: Resultsmentioning

confidence: 91%

Pre-Treatment Dose Verification of Imrt Using Gafchromic Ebt3 Film and 2DArray

Nalbant¹,

N²,

Bilge³

2014

J Nucl Med Radiat Ther

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“…In addition, a dose < x% was not considered, where x% was the small amount of dose in order to eliminate the influence from the low-dose regions. [35][36][37][38] For all brain IMRT plans delivered by the 6 and 15 MV photon beams, the DD calculated between the TPS and Gafchromic EBT3 film was measured at the isocentre and the 30, 60 and 90% area extended after isocentre, in the selected regions of interest (ROI). We made a condition as accepting criteria for the DD as < 1, <3, <5 and <10% at the isocentre, and 30, 60 and 90% area extended from the isocentre, respectively, for all IMRT plans.…”

Section: Absorbed Ddmentioning

confidence: 99%

Selection of gamma analysis acceptance criteria in IMRT QA using Gafchromic EBT3 film dosimetry

et al. 2018

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Background and purposeThis study reported the justification and selection of acceptable γ criteria with respect to low (6 MV) and high (15 MV) photon beams for intensity-modulated radiation therapy quality assurance (IMRT QA) using the Gafchromic external beam therapy 3 (EBT3) film.Materials and methodsFive-field step-and-shoot IMRT was used to treat 16 brain IMRT patients using the dual-energy DHX-S linear accelerator (Varian Medical System, Palo Alto, CA, USA). Dose comparisons between computed values of the treatment planning system (TPS) and Gafchromic EBT3 film were evaluated based on γ analysis using the Film QA Pro software. The dose distribution was analysed with gamma area histograms (GAHs) generated using different γ criteria (3%/2 mm, 3%/3 mm and 5%/3 mm) for the 6 and 15 MV photon beams, to optimise the best distance-to-agreement (DTA) criteria with respect to the beam energy.ResultsFrom the comparison between the dose distributions acquired from the TPS and EBT3 film, a DTA criterion of 3%/2 mm showed less dose differences (DDs) with passing rates up to 93% for the 6 MV photon beams, while for the 15 MV a relaxed DTA criterion of 5%/3 mm was consistent with the DD acceptability criteria with a 95% passing rate.ConclusionsOur results suggested that high-energy photon beams required relaxed DTA criteria for the brain IMRT QA, while low-energy photon beams showed better results even with tight DTA criteria.

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“…The detector spacing (center to center) is 1 cm. The dimensions of each detector are 0.5 × 0.5 × 0.5 cm 3 [8].…”

Section: Treatment Planningmentioning

confidence: 99%

Dosimetric Study on Variations of Gamma Index (GI) in Pre-Treatment Verification Procedure in Intensity Modulated Radiotherapy (IMRT) Plans with Varying Grid Sizes Using 2D Array Detectors

Pathak¹,

Mishra²,

Birbiya³

2015

J Cancer Sci Ther

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Aim:The main aim of our study was to compare the variation of Gamma Index (GI) in Pre-treatment Verification Procedure in Intensity Modulated Radiotherapy (IMRT) Plans with Varying Grid Sizes Using 2D Array Detectors.Choosing an optimum grid size plays a vital role for planning in radiotherapy cases especially while treating with IMRT. A minimal change of even 1 mm of grid size can result in large variation in treatment planning and is reflected in quality assurance results also. Methods and Material:We compared IMRT plans for a total of 12 patients. Out of these 12 patients 4 were head and neck, 4 were pelvic and 4 were brain patients respectively. For each patient three plans were generated with three different grid sizes. The plan acceptance criteria were 95% of PTV to receive at least 95% of prescribed dose and dose to 1% of PTV not to exceed 107% of prescribed dose. Dose for the organs at risk were respected as per the QUANTEC guidelines. After plan acceptance corresponding Pre-treatment Verification Procedure for IMRT was executed by PTW 729 array detector. The Gamma index (GI) results of each plan were recorded for the three different grid sizes. The passing criteria were kept to be 3% Dose Difference (DD) and 3 mm Distance to Agreement (DTA) for all cases. Results:We estimated the variations in GI quality assurance results for patients undergoing IMRT planning with varying grid sizes of 3 mm, 5 mm and 10 mm respectively. We also evaluated 2% DD and 2 mm DTA, 3% DD, 3 mm DTA and 5% DD, 5 mm DTA criteria for passing result. Stastical analysis:We have calculated the average and standard Deviations (Std. Dev.) for each passing criteria for 2% DD, 2 mm DTA, 3% DD, 3 mm DTA and 5% DD, 5 mm DTA for each IMRT plans with varying grid sizes. Conclusions:Though the present results suggest the gamma criteria of 5% DD and 5 mm DTA as the most suitable criteria for IMRT quality assurance. This gamma criterion of 5% DD and 5 mm DTA favourably exceeds 95% in each case and grid sizes but it is not recommended for strict verification procedure in Intensity Modulated Radiotherapy (IMRT). The criteria of 2% DD and 2 mm DTA, and 3% DD and 3 mm DTA gamma values show below 90% for 5 mm and 10 mm grid sizes but exceeds 95% for the 3 mm grid sizes.Hence 3 mm or less grid sizes should be routinely used in pre-treatment verification procedure IMRT plans using 2D Array Detectors.

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Dose verification of intensity modulated radiotherapy in head and neck tumors

Cited by 6 publications

References 22 publications

Pre-Treatment Dose Verification of Imrt Using Gafchromic Ebt3 Film and 2DArray

Pre-Treatment Dose Verification of Imrt Using Gafchromic Ebt3 Film and 2DArray

Selection of gamma analysis acceptance criteria in IMRT QA using Gafchromic EBT3 film dosimetry

Dosimetric Study on Variations of Gamma Index (GI) in Pre-Treatment Verification Procedure in Intensity Modulated Radiotherapy (IMRT) Plans with Varying Grid Sizes Using 2D Array Detectors

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