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Basic dosimetric verification in water of the anisotropic analytical algorithm for Varian, Elekta and Siemens linacs

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ZEITSCHRIFT FUR MEDIZINISCHE PHYSIK 2008年第2期18卷 128-135页

作者： Cozzi, Luca Nicolini, Giorgia Vanetti, Eugenio Clivio, Alessandro Glashoerster, Marco Schiefer, Hans Fogliata, Antonella Oncol Inst So Switzerland Dept Radiat Oncol Med Phys Unit CH-6504 Bellinzona Switzerland Univ Munster Dept Radiat Oncol Munster Germany Kantonsspital St Gallen Klin Radioonkol St Gallen Switzerland Univ Lausanne Fac Med Lausanne Switzerland

Since early 2007 a new version of the anisotropic analytical algorithm (AAA) for photon dose calculations was released by Varian Medical Systems for clinical usage on Elekta linacs and also, with some restrictions, for Siemens linaes. Basic validation studies were peformed and reported for three beams: 4,6 and 15 MV for an Elekta Synergy, 6 and 15 MV for a Siemens Primus and, as a reference, for 6 and 15 MV from a Varian Clinac 2100C/D. Generally AAA calculations reproduced well measured data and small deviations were observed for open and wedged fields. PDD curves showed in average differences between calculation and measurement smaller than 1% or 1.2 mm for Elekta beams, 1% or 1.8 mm for Siemens beams and 1% or I mm for Varian beams. Profiles in the flattened region matched measurements with deviations smaller than 1% for Elekta and Varian beams, 2% for Siemens. Percentage differences in Output Factors were observed as small as 1% in average.

关键词： convolution algorithms anisotropic analytical algorithm treatment planning systems

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Clinical implications in the use of the PBC algorithm versus the AAA by comparison of different NTCP models/parameters

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RADIATION ONCOLOGY 2013年第1期8卷 1-13页

作者： Bufacchi, Antonella Nardiello, Barbara Capparella, Roberto Begnozzi, Luisa S Giovanni Calibita Fatebenefratelli Hosp Clin Pio11 Rome Italy S Giovanni Calibita Fatebenefratelli Hosp UOC Med Phys Rome Italy UPMC San Pietro FBF Adv Radiotherapy Ctr Rome Italy

Purpose: Retrospective analysis of 3D clinical treatment plans to investigate qualitative, possible, clinical consequences of the use of PBC versus AAA. Methods: The 3D dose distributions of 80 treatment plans at four different tumour sites, produced using PBC algorithm, were recalculated using AAA and the same number of monitor units provided by PBC and clinically delivered to each patient;the consequences of the difference on the dose-effect relations for normal tissue injury were studied by comparing different NTCP model/parameters extracted from a review of published studies. In this study the AAA dose calculation is considered as benchmark data. The paired Student t-test was used for statistical comparison of all results obtained from the use of the two algorithms. Results: In the prostate plans, the AAA predicted lower NTCP value (NTCPAAA) for the risk of late rectal bleeding for each of the seven combinations of NTCP parameters, the maximum mean decrease was 2.2%. In the head-and-neck treatments, each combination of parameters used for the risk of xerostemia from irradiation of the parotid glands involved lower NTCPAAA, that varied from 12.8% (sd=3.0%) to 57.5% (sd=4.0%), while when the PBC algorithm was used the NTCPPBC's ranging was from 15.2% (sd=2.7%) to 63.8% (sd=3.8%), according the combination of parameters used;the differences were statistically significant. Also NTCPAAA regarding the risk of radiation pneumonitis in the lung treatments was found to be lower than NTCPPBC for each of the eight sets of NTCP parameters;the maximum mean decrease was 4.5%. A mean increase of 4.3% was found when the NTCPAAA was calculated by the parameters evaluated from dose distribution calculated by a convolution-superposition (CS) algorithm. A markedly different pattern was observed for the risk relating to the development of pneumonitis following breast treatments: the AAA predicted higher NTCP value. The mean NTCPAAA varied from 0.2% (sd = 0.1%) to 2.1% (sd = 0.3%), w

关键词： Dose volume histogram Normal tissue complication probability Pencil beam convolution algorithm anisotropic analytical algorithm

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Critical Appraisal of Acuros XB and anisotropic Analytic algorithm Dose Calculation in Advanced Non-Small-Cell Lung Cancer Treatments

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INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS 2012年第5期83卷 1587-1595页

作者： Fogliata, Antonella Nicolini, Giorgia Clivio, Alessandro Vanetti, Eugenio Cozzi, Luca Oncol Inst So Switzerland Med Phys Unit CH-6504 Bellinzona Switzerland

Purpose: To assess the clinical impact of the Acuros XB algorithm (implemented in the Varian Eclipse treatment-planning system) in non-small-cell lung cancer (NSCLC) cases. Methods and Materials: A CT dataset of 10 patients presenting with advanced NSCLC was selected and contoured for planning target volume, lungs, heart, and spinal cord. Plans were created for 6-MV and 15-MV beams using three-dimensional conformal therapy, intensity-modulated therapy, and volumetric modulated arc therapy with RapidArc. Calculations were performed with Acuros XB and the anisotropic analytical algorithm. To distinguish between differences coming from the different heterogeneity management and those coming from the algorithm and its implementation, all the plans were recalculated assigning Hounsfield Unit (HU) = 0 (Water) to the CT dataset. Results: Differences in dose distributions between the two algorithms calculated in Water were < 0.5%. This suggests that the differences in the real CT dataset can be ascribed mainly to the different heterogeneity management, which is proven to be more accurate in the Acuros XB calculations. The planning target dose difference was stratified between the target in soft tissue, where the mean dose was found to be lower for Acuros XB, with a range of 0.4% +/- 0.6% (intensity-modulated therapy, 6 MV) to 1.7% +/- 0.2% (three-dimensional conformal therapy, 6 MV), and the target in lung tissue, where the mean dose was higher for 6 MV (from 0.2% +/- 0.2% to 1.2% +/- 0.5%) and lower for 15 MV (from 0.5% +/- 0.5% to 2.0% +/- 0.9%). Mean doses to organs at risk presented differences up to 3% of the mean structure dose in the worst case. No particular or systematic differences were found related to the various modalities. Calculation time ratios between calculation time for Acuros XB and the anisotropic analytical algorithm were 7 for three-dimensional conformal therapy, 5 for intensity-modulated therapy, and 0.2 for volumetric modulated arc therapy with Rapi

关键词： Acuros anisotropic analytical algorithm NSCLC Inhomogeneity dose calculation

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Dosimetric comparison of Acuros XB deterministic radiation transport method with Monte Carlo and model-based convolution methods in heterogeneous media

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MEDICAL PHYSICS 2011年第5期38卷 2651-2664页

作者： Han, Tao Mikell, Justin K. Salehpour, Mohammad Mourtada, Firas Univ Texas MD Anderson Canc Ctr Dept Radiat Phys Houston TX 77030 USA Univ Texas Grad Sch Biomed Sci Houston TX 77030 USA Univ Texas MD Anderson Canc Ctr Dept Expt Diagnost Imaging Houston TX 77030 USA

Purpose: The deterministic Acuros XB (AXB) algorithm was recently implemented in the Eclipse treatment planning system. The goal of this study was to compare AXB performance to Monte Carlo (MC) and two standard clinical convolution methods: the anisotropic analytical algorithm (AAA) and the collapsed-cone convolution (CCC) method. Methods: Homogeneous water and multilayer slab virtual phantoms were used for this study. The multilayer slab phantom had three different materials, representing soft tissue, bone, and lung. Depth dose and lateral dose profiles from AXB v10 in Eclipse were compared to AAA v10 in Eclipse, CCC in Pinnacle(3), and EGSnrc MC simulations for 6 and 18 MV photon beams with open fields for both phantoms. In order to further reveal the dosimetric differences between AXB and AAA or CCC, three-dimensional (3D) gamma index analyses were conducted in slab regions and subregions defined by AAPM Task Group 53. Results: The AXB calculations were found to be closer to MC than both AAA and CCC for all the investigated plans, especially in bone and lung regions. The average differences of depth dose profiles between MC and AXB, AAA, or CCC was within 1.1, 4.4, and 2.2%, respectively, for all fields and energies. More specifically, those differences in bone region were up to 1.1, 6.4, and 1.6%;in lung region were up to 0.9, 11.6, and 4.5% for AXB, AAA, and CCC, respectively. AXB was also found to have better dose predictions than AAA and CCC at the tissue interfaces where backscatter occurs. 3D gamma index analyses (percent of dose voxels passing a 2%/2 mm criterion) showed that the dose differences between AAA and AXB are significant (under 60% passed) in the bone region for all field sizes of 6 MV and in the lung region for most of field sizes of both energies. The difference between AXB and CCC was generally small (over 90% passed) except in the lung region for 18 MV 10 x 10 cm(2) fields (over 26% passed) and in the bone region for 5 x 5 and 10 x 10 cm(2)

关键词： deterministic dose calculation Acuros XB Monte Carlo anisotropic analytical algorithm collapsed-cone convolution

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Dosimetry of oblique tangential photon beams calculated by superposition/convolution algorithms: a Monte Carlo evaluation

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JOURNAL OF APPLIED CLINICAL MEDICAL PHYSICS 2011年第1期12卷 108-121页

作者： Chow, James C. L. Jiang, Runqing Leung, Michael K. K. Princess Margaret Hosp Dept Radiat Phys Radiat Med Program Univ Hlth Network Toronto ON M5G 2M9 Canada Univ Toronto Dept Radiat Oncol Toronto ON Canada Ryerson Univ Dept Phys Toronto ON Canada Grand River Reg Canc Ctr Dept Med Phys Kitchener ON Canada Univ Toronto Dept Med Biophys Toronto ON M5S 1A1 Canada

Although there are many works on evaluating dose calculations of the anisotropic analytical algorithm (AAA) using various homogeneous and heterogeneous phantoms, related work concerning dosimetry due to tangential photon beam is lacking. In this study, dosimetry predicted by the AAA and collapsed cone convolution (CCC) algorithm was evaluated using the tangential photon beam and phantom geometry. The photon beams of 6 and 15 MV with field sizes of 4 x 4 (or 7 x 7), 10 x 10 and 20 x 20 cm(2), produced by a Varian 21 EX linear accelerator, were used to test performances of the AAA and CCC using Monte Carlo (MC) simulation (EGSnrc-based code) as a benchmark. Horizontal dose profiles at different depths, phantom skin profiles (i.e., vertical dose profiles at a distance of 2 mm from the phantom lateral surface), gamma dose distributions, and dose-volume histograms (DVHs) of skin slab were determined. For dose profiles at different depths, the CCC agreed better with doses in the air-phantom region, while both the AAA and CCC agreed well with doses in the penumbra region, when compared to the MC. Gamma evaluations between the AAA/CCC and MC showed that deviations of 2D dose distribution occurred in both beam edges in the phantom and air-phantom interface. Moreover, the gamma dose deviation is less significant in the air-phantom interface than the penumbra. DVHs of skin slab showed that both the AAA and CCC underestimated the width of the dose drop-off region for both the 6 and 15 MV photon beams. When the gantry angle was 0 degrees, it was found that both the AAA and CCC overestimated doses in the phantom skin profiles compared to the MC, with various photon beam energies and field sizes. The mean dose differences with doses normalized to the prescription point for the AAA and CCC were respectively: 7.6% +/- 2.6% and 2.1% +/- 1.3% for a 10 x 10 cm(2) field, 6 MV;16.3% +/- 2.1% and 6.7% +/- 2.1% for a 20 x 20 cm(2) field, 6 MV;5.5% +/- 1.2% and 1.7% +/- 1.4% for a 10 x 10 c

关键词： anisotropic analytical algorithm collapsed cone convolution MC simulation dosimetry inhomogeneity correction surface dose

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Early clinical experience of radiotherapy of prostate cancer with volumetric modulated arc therapy

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RADIATION ONCOLOGY 2010年第1期5卷 54-54页

作者： Pesce, Gianfranco A. Clivio, Alessandro Cozzi, Luca Nicolini, Giorgia Richetti, Antonella Salati, Emanuela Valli, Mariacarla Vanetti, Eugenio Fogliata, Antonella Oncol Inst So Switzerland Med Phys Unit Bellinzona Switzerland Oncol Inst So Switzerland Dept Radiat Oncol Bellinzona Switzerland

Background: To report about initial clinical experience in radiation treatment of carcinoma of prostate with volumetric modulated arcs with the RapidArc (RA) technology. Methods: Forty-five patients with a median age of 72 +/- 3, affected by prostate carcinoma (T1c: 22 patients, T2a-b: 17 patients, T3a-b: 6 patients. N0: 43 patients, N1-Nx: 2 patients, all M0), with initial PSA of 10.0 +/- 3.0 ng/mL, were treated with RapidArc in a feasibility study. All patients were treated with single arc using 6MV photons. Dose prescription ranged between 76 (7 patients) and 78 Gy (38 patients) in 2Gy/fraction. Plan quality was assessed by means of Dose Volume Histogram (DVH) analysis. Technical parameters of arcs and pre-treatment quality assurance results (Gamma Agreement Index, GAI) are reported to describe delivery features. Early toxicity was scored (according to the Common Terminology Criteria of Adverse Effects scale, CTCAE, scale) at the end of treatment together with biochemical outcome (PSA). Results: From DVH data, target coverage was fulfilling planning objectives: V-95% was in average higher than 98% and V-107%similar to 0.0% (D-2%similar to 104.0% in average). Homogeneity D-5%-D-95% ranged between 6.2 +/- 1.0% to 6.7 +/- 1.3%. For rectum, all planning objectives were largely met (e. g. V-70Gy = 10.7 +/- 5.5% against an objective of < 25%) similarly for bladder (e. g. D-2% = 79.4 +/- 1.2Gy against an objective of 80.0Gy). Maximum dose to femurs was D-2% = 36.7 +/- 5.4Gy against an objective of 47Gy. Monitor Units resulted: MU/Gy = 239 +/- 37. Average beam on time was 1.24 +/- 0.0 minutes. Pretreatment GAI resulted in 98.1 +/- 1.1%. Clinical data were recorded as PSA at 6 weeks after RT, with median values of 0.4 +/- 0.4 ng/mL. Concerning acute toxicity, no patient showed grade 2-3 rectal toxicity;5/42 (12%) patients experienced grade 2 dysuria;18/41 (44%) patients preserved complete or partial erectile function. Conclusion: RapidArc proved to be a safe, qualitative

关键词： Seminal Vesicle Planning Target Volume Clinical Target Volume Dose Volume Histogram anisotropic analytical algorithm

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Implications of a high-definition multileaf collimator (HD-MLC) on treatment planning techniques for stereotactic body radiation therapy (SBRT): a planning study

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RADIATION ONCOLOGY 2009年第1期4卷 22-22页

作者： Tanyi, James A. Summers, Paige A. McCracken, Charles L. Chen, Yiyi Ku, Li-Chung Fuss, Martin Oregon Hlth & Sci Univ Dept Radiat Med Portland OR 97239 USA Oregon State Univ Dept Nucl Engn & Radiat Hlth Phys Corvallis OR 97331 USA Santa Clara Univ Dept Phys Santa Clara CA 95053 USA Oregon Hlth & Sci Univ Dept Publ Hlth & Prevent Med Portland OR 97239 USA

Purpose: To assess the impact of two multileaf collimator (MLC) systems (2.5 and 5 mm leaf widths) on three-dimensional conformal radiotherapy, intensity-modulated radiotherapy, and dynamic conformal arc techniques for stereotactic body radiation therapy (SBRT) of liver and lung lesions. Methods: Twenty-nine SBRT plans of primary liver (n = 11) and lung ( n = 18) tumors were the basis of this study. Five-millimeter leaf width 120-leaf Varian Millennium (M120) MLC-based plans served as reference, and were designed using static conformal beams (3DCRT), sliding-window intensity-modulated beams (IMRT), or dynamic conformal arcs (DCA). Reference plans were either re-optimized or recomputed, with identical planning parameters, for a 2.5-mm width 120-leaf BrainLAB/Varian high-definition (HD120) MLC system. Dose computation was based on the anisotropic analytical algorithm (AAA, Varian Medical Systems) with tissue heterogeneity taken into account. Each plan was normalized such that 100% of the prescription dose covered 95% of the planning target volume (PTV). Isodose distributions and dose-volume histograms (DVHs) were computed and plans were evaluated with respect to target coverage criteria, normal tissue sparing criteria, as well as treatment efficiency. Results: Dosimetric differences achieved using M120 and the HD120 MLC planning were generally small. Dose conformality improved in 51.7%, 62.1% and 55.2% of the IMRT, 3DCRT and DCA cases, respectively, with use of the HD120 MLC system. Dose heterogeneity increased in 75.9%, 51.7%, and 55.2% of the IMRT, 3DCRT and DCA cases, respectively, with use of the HD120 MLC system. DVH curves demonstrated a decreased volume of normal tissue irradiated to the lower (90%, 50% and 25%) isodose levels with the HD120 MLC. Conclusion: Data derived from the present comparative assessment suggest dosimetric merit of the high definition MLC system over the millennium MLC system. However, the clinical significance of these results warrants f

关键词： Planning Target Volume Stereotactic Body Radiation Therapy Conformity Index Heterogeneity Index anisotropic analytical algorithm

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