On the dosimetric behaviour of photon dose calculation algorithms in the presence of simple geometric heterogeneities: comparison with Monte Carlo calculations

Fogliata, Antonella; Vanetti, Eugenio; Albers, D.; Brink, Carsten; Clivio, Alessandro; Knöös, Tommy; Nicolini, G.; Cozzi, Luca

doi:10.1088/0031-9155/52/5/011

Cited by 215 publications

(164 citation statements)

References 36 publications

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“…2 A number of studies have shown the limitation of photon dose calculation algorithms such as analytical anisotropic algorithm (AAA), collapsed cone convolution (CCC) algorithm, and pencil beam convolution (PBC) algorithm when complex geometry with inhomogeneity is involved along the photon beam path. [3][4][5][6][7][8][9][10][11][12] Both the AAA and CCC are based on the superposition/convolution method, which calculates the dose by superposition of dose kernels of primary and scatter components that are derived from the Monte Carlo (MC). The tissue inhomogeneity correction in superposition/convolution method such as in the AAA is done both in the beamlet direction and lateral directions.…”

Section: Introductionmentioning

confidence: 99%

Clinical dosimetric impact of Acuros XB and analytical anisotropic algorithm (AAA) on real lung cancer treatment plans : review

Rana

2014

Int J Cancer Ther Oncol

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Photon dose calculation algorithms in treatment planning system could affect the accuracy of dose delivery when tissue heterogeneity is involved along the beam path. Treatment planning for lung cancer is challenging, especially in the case of treatment plan involving small fields. The combination of low-density (air) medium and small fields cause charge particle disequilibrium nears the air/tissue interface. Beam modeling within the dose calculation algorithms must also employ an accurate method of accounting tissue heterogeneity corrections in order to avoid dose overestimation or underestimation. Analytical anisotropic algorithm (AAA) is one of the widely tested and validated dose calculation algorithms in external beam photon radiation therapy. Recently, Acuros XB (AXB) was made available for photon dose calculations, and several studies have demonstrated better dose prediction accuracy of the AXB over AAA. This article reviews the results from the treatment planning studies, which have investigated the clinical dosimetric impact of the AXB and AAA on real lung cancer treatment plans.

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Section: Introductionmentioning

confidence: 99%

Clinical dosimetric impact of Acuros XB and analytical anisotropic algorithm (AAA) on real lung cancer treatment plans : review

Rana

2014

Int J Cancer Ther Oncol

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“…( 6 ) Another challenge comes from the dose calculation in a heterogeneous medium. ( 7 ) Currently, dose calculation algorithms with heterogeneity correction are not consistent among different treatment planning systems, ( 8 – 12 ) depending on how the changes in lateral electron transport are taken into account. ( 13 ) For this reason, dose calculations without heterogeneity correction were required in RTOG 0236, ( 14 ) which was a phase II trial of SBRT in the early stages of medically inoperable NSCLC.…”

Section: Introductionmentioning

confidence: 99%

“…One such dose calculation algorithm is the collapsed cone convolution algorithm implemented in the Pinnacle treatment planning system (Philips Healthcare, Andover, MA), which has demonstrated accurate dose calculations in the heterogeneous medium. ( 11 , 12 ) Using the Pinnacle treatment planning system (TPS), Xiao et al ( 15 ) have retrospectively analyzed treatment plans submitted to RTOG 0236 from multiple institutions. Significant dose differences were found when heterogeneity correction was applied.…”

Section: Introductionmentioning

confidence: 99%

Dose calculation differences between Monte Carlo and pencil beam depend on the tumor locations and volumes for lung stereotactic body radiation therapy

Zhuang

Djemil

Pan

et al. 2013

J Applied Clin Med Phys

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Stereotactic body radiation therapy (SBRT) has been increasingly used as an efficacious treatment modality for early‐stage non‐small cell lung cancer. The accuracy of dose calculations is compromised due to the presence of inhomogeneity. For the purpose of a consistent prescription, radiation doses were calculated without heterogeneity correction in several RTOG trials. For patients participating in these trials, recalculations of the planned doses with more accurate dose methods could provide better correlations between the treatment outcomes and the planned doses. Using a Monte Carlo (MC) dose calculation algorithm as a gold standard, we compared the recalculated doses with the MC algorithm to the original pencil beam (PB) calculations for our institutional clinical lung SBRT plans. The focus of this comparison is to investigate the volume and location dependence on the differences between the two dose calculations. Thirty‐one clinical plans that followed RTOG and other protocol guidelines were retrospectively investigated in this study. Dosimetric parameters, such as D1, D95, and D99 for the PTV and D1 for organs at risk, were compared between two calculations. Correlations of mean lung dose and V20 of lungs between two calculations were investigated. Significant dependence on tumor size and location was observed from the comparisons between the two dose calculation methods. When comparing the PB calculations without heterogeneity correction to the MC calculations with heterogeneity correction, we found that in terms of D95 of PTV: (1) the two calculations resulted in similar D95 for edge tumors with volumes greater than 25.1 cc; (2) an average overestimation of 5% in PB calculations for edge tumors with volumes less than 25.1 cc; and (3) an average overestimation of 9% or underestimation of 3% in PB calculations for island tumors with volumes smaller or greater than 22.6 cc, respectively. With heterogeneity correction, the PB calculations resulted in an average reduction of 23.8% and 15.3% in the D95 for the PTV for island and edge lesions, respectively, when compared to the MC calculations. For organs at risks, very small differences were found among all the comparisons. Excellent correlations for mean dose and V20 of lungs were observed between the two calculations. This study demonstrated that using a single scaling factor may be overly simplified when accounting for the effects of heterogeneity correction. Accurate dose calculations, such as the Monte Carlo algorithms, are highly recommended to understand dose responses in lung SBRT.PACS number: 87.53.Ly

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“…The improved accuracy of the AAA in phantom situations and 3D conformal radiotherapy (3D-CRT) treatment plans compared to Eclipse's Pencil Beam Convolution (PBC) algorithm (the Eclipse implementation of the Single Pencil Beam algorithm of the same manufacturer's CadPlan TPS) has been reported by several authors [8][9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Clinical implications of the anisotropic analytical algorithm for IMRT treatment planning and verification

Bragg

Wingate

Conway

2008

Radiotherapy and Oncology

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Published paper AbstractPurpose: To determine the implications of the use of the Anisotropic Analytical Algorithm (AAA) for the production and dosimetric verification of IMRT plans for treatments of the prostate, parotid, nasopharynx and lung. Methods: 72 IMRT treatment plans produced using the Pencil Beam Convolution (PBC) algorithm were recalculated using the AAA and the dose distributions compared. 24 of the plans were delivered to inhomogeneous phantoms and verification measurements made using a pinpoint ionisation chamber. The agreement between the AAA and measurement was determined.Results: Small differences were seen in the prostate plans, with the AAA predicting slightly lower minimum PTV doses. In the parotid plans, there were small increases in the lens and contralateral parotid doses while the nasopharyngeal plans revealed a reduction in the volume of the PTV covered by the 95% isodose (the V 95% ) when the AAA was used. Large changes were seen in the lung plans, the AAA predicting reductions in the minimum PTV dose and large reductions in the V 95% . The AAA also predicted small increases in the mean dose to the normal lung and the V 20 . In the verification measurements, all AAA calculations were within 3% or 3.5mm distance to agreement of the measured doses. Conclusions:The AAA should be used in preference to the PBC algorithm for treatments involving low density tissue but this may necessitate re-evaluation of plan acceptability criteria. Improvements to the Multi-Resolution Dose Calculation algorithm used in the inverse planning are required to reduce the convergence error in the presence of lung tissue. There was excellent agreement between the AAA and verification measurements for all sites.3

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On the dosimetric behaviour of photon dose calculation algorithms in the presence of simple geometric heterogeneities: comparison with Monte Carlo calculations

Cited by 215 publications

References 36 publications

Clinical dosimetric impact of Acuros XB and analytical anisotropic algorithm (AAA) on real lung cancer treatment plans : review

Clinical dosimetric impact of Acuros XB and analytical anisotropic algorithm (AAA) on real lung cancer treatment plans : review

Dose calculation differences between Monte Carlo and pencil beam depend on the tumor locations and volumes for lung stereotactic body radiation therapy

Clinical implications of the anisotropic analytical algorithm for IMRT treatment planning and verification

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