Dosimetric verification of the anisotropic analytical algorithm for radiotherapy treatment planning

Bragg, C.; Conway, J.

doi:10.1016/j.radonc.2006.10.020

Cited by 68 publications

(48 citation statements)

References 25 publications

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“…All calculated doses agreed with measurement to within 3% or 3.3mm distance to agreement and all but one to within 3% or 3mm, confirming the accuracy of the AAA calculations of these IMRT plans. The magnitudes of the mean discrepancies were of the same order as were found in a previous study for conventional radiotherapy treatment fields measured on the thorax phantom [9] and as those reported for IMRT fields by Khodri et al [28].…”

Section: Discussionsupporting

confidence: 85%

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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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Section: Discussionsupporting

confidence: 85%

“…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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“…This large hollow structure could pose a challenge for the model‐based dose calculation algorithm implemented in the treatment planning system (TPS). ( 14 – 17 ) To evaluate this issue, we perform an open field dose validation for both the ArcCHECK system and the TPS. Considering the uncertainties of the diode dose measurement and the TPS dose calculation, Monte Carlo (MC) simulation, which has been recognized as the gold standard for estimating the radiotherapy dose measurements/calculations, ( 18 ) is utilized as an independent reference in this study.…”

Section: Introductionmentioning

confidence: 99%

Measurement comparison and Monte Carlo analysis for volumetric‐modulated arc therapy (VMAT) delivery verification using the ArcCHECK dosimetry system

Lin

Koren

Veltchev

et al. 2013

J Applied Clin Med Phys

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The objective of this study is to validate the capabilities of a cylindrical diode array system for volumetric‐modulated arc therapy (VMAT) treatment quality assurance (QA). The VMAT plans were generated by the Eclipse treatment planning system (TPS) with the analytical anisotropic algorithm (AAA) for dose calculation. An in‐house Monte Carlo (MC) code was utilized as a validation tool for the TPS calculations and the ArcCHECK measurements. The megavoltage computed tomography (MVCT) of the ArcCHECK system was adopted for the geometry reconstruction in the TPS and for MC simulations. A 10×10 cm2 open field validation was performed for both the 6 and 10 MV photon beams to validate the absolute dose calibration of the ArcCHECK system and also the TPS dose calculations for this system. The impact of the angular dependency on noncoplanar deliveries was investigated with a series of 10×10 cm2 fields delivered with couch rotation 0° to 40°. The sensitivity of detecting the translational (1 to 10 mm) and the rotational (1° to 3°) misalignments was tested with a breast VMAT case. Ten VMAT plans (six prostate, H&N, pelvis, liver, and breast) were investigated to evaluate the agreement of the target dose and the peripheral dose among ArcCHECK measurements, and TPS and MC dose calculations. A customized acrylic plug holding an ion chamber was used to measure the dose at the center of the ArcCHECK phantom. Both the entrance and the exit doses measured by the ArcCHECK system with and without the plug agreed with the MC simulation to 1.0%. The TPS dose calculation with a 2.5 mm grid overestimated the exit dose by up to 7.2% when the plug was removed. The agreement between the MC and TPS calculations for the ArcCHECK without the plug improved significantly when a 1 mm dose calculation grid was used in the TPS. The noncoplanar delivery test demonstrated that the angular dependency has limited impact on the gamma passing rate (<1.2% drop) for the 2%–3% dose and 2 mm–3 mm DTA criteria. A 1° rotational misalignment introduces 11.3% (3%/3 mm) to 21.3% (1%/1 mm) and 0.2% (3%/3 mm) to 0.8% (1%/1 mm) Gamma passing rate drop for ArcCHECK system and MatriXX system, respectively. Both systems have comparable sensitivity to the AP misalignments. However, a 2 mm RL misalignment introduces gamma passing rate drop ranging from 0.9% (3%/3 mm) to 4.0% (1%/1 mm) and 5.0% (3%/3 mm) to 12.0% (1%/1 mm) for ArcCHECK and MatriXX measurements, respectively. For VMAT plan QA, the gamma analysis passing rates ranged from 96.1% (H&N case) to 99.9% (prostate case), when using the 3%/3 mm DTA criteria for the peripheral dose validation between the TPS and ArcCHCEK measurements. The peripheral dose validation between the MC simulation and ArcCHECK measurements showed at least 97.9% gamma passing rates. The central dose validation also showed an agreement within 2.2% between TPS/MC calculations and ArcCHECK measurements. The worst discrepancy was found in the H&N case, which is the most complex VMAT case. The ArcCHECK system is suitable for VMAT QA evaluation...

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“…( 8 – 14 ) For dose distribution calculations in heterogeneous media, and especially at interfaces, the AAA algorithm has been shown to be consistently more accurate than the pencil beam convolution (PBC) algorithm. ( 9 , 10 , 14 – 16 ) …”

Section: Introductionmentioning

confidence: 99%

Validation of the Eclipse AAA algorithm at extended SSD

Hussain

Villarreal-Barajas

Brown

et al. 2010

J Applied Clin Med Phys

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The accuracy of dose calculations at extended SSD is of significant importance in the dosimetric planning of total body irradiation (TBI). In a first step toward the implementation of electronic, multi‐leaf collimator compensation for dose inhomogeneities and surface contour in TBI, we have evaluated the ability of the Eclipse AAA to accurately predict dose distributions in water at extended SSD. For this purpose, we use the Eclipse AAA algorithm, commissioned with machine‐specific beam data for a 6 MV photon beam, at standard SSD (100 cm). The model was then used for dose distribution calculations at extended SSD (179.5 cm). Two sets of measurements were acquired for a 6 MV beam (from a Varian linear accelerator) in a water tank at extended SSD: i) open beam for 5 × 5, 10 × 10, 20 × 20 and 40×40 cm2 field sizes (defined at 179.5 cm SSD), and ii) identical field sizes but with a 1.3 cm thick acrylic spoiler placed 10 cm above the water surface. Dose profiles were acquired at 5 cm, 10 cm and 20 cm depths. Dose distributions for the two setups were calculated using the AAA algorithm in Eclipse. Confidence limits for comparisons between measured and calculated absolute depth dose curves and normalized dose profiles were determined as suggested by Venselaar et al. The confidence limits were within 2% and 2 mm for both setups. Extended SSD calculations were also performed using Eclipse AAA, commissioned with Varian Golden beam data at standard SSD. No significant difference between the custom commissioned and Golden Eclipse AAA was observed. In conclusion, Eclipse AAA commissioned at standard SSD can be used to accurately predict dose distributions in water at extended SSD for 6 MV open beams.PACS numbers: 87.53.Kn, 87.55.D‐, 87.55.de, 87.56.ng

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Dosimetric verification of the anisotropic analytical algorithm for radiotherapy treatment planning

Abstract: Published paper

Cited by 68 publications

References 25 publications

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

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

Measurement comparison and Monte Carlo analysis for volumetric‐modulated arc therapy (VMAT) delivery verification using the ArcCHECK dosimetry system

Validation of the Eclipse AAA algorithm at extended SSD

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