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Dosimetric evaluation of the acuros xb algorithm for a 4MV photon beam in head and neck intensity-modulated radiation therapy

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JOURNAL OF APPLIED CLINICAL MEDICAL PHYSICS 2015年第4期16卷 52-64页

作者： Hirata, Kimiko Nakamura, Mitsuhiro Yoshimura, Michio Mukumoto, Nobutaka Nakata, Manabu Ito, Hitoshi Inokuchi, Haruo Matsuo, Yukinori Mizowaki, Takashi Hiraoka, Masahiro Kyoto Univ Grad Sch Med Dept Radiat Oncol & Image Appl Therapy Kyoto 6068507 Japan Kyoto Univ Hosp Clin Radiol Serv Div Kyoto 606 Japan

In this study, we assessed the differences in the dose distribution of a 4 MV photon beam among different calculation algorithms: the acuros xb (Axb) algorithm, the analytic anisotropic algorithm (AAA), and the pencil beam convolution (PBC) algorithm (ver. 11.0.31), in phantoms and in clinical intensity-modulated radiation therapy (IMRT) plans. Homogeneous and heterogeneous, including middle-, low-, and high-density, phantoms were combined to assess the percentage depth dose and lateral dose profiles among Axb, AAA, and PBC. For the phantom containing the low-density area, Axb was in agreement with measurement within 0.5%, while the greatest differences between the AAA and PBC calculations and measurement were 2.7% and 3.6%, respectively. Axb showed agreement with measurement within 2.5% at the high-density area, while AAA and PBC overestimated the dose by more than 4.5% and 4.0%, respectively. Furthermore, 15 IMRT plans, calculated using Axb, for oropharyngeal, hypopharyngeal, and laryngeal carcinomas were analyzed. The dose prescription was 70 Gy to 50% of the planning target volume (PTV70). Subsequently, each plan was recalculated using AAA and PBC while maintaining the Axb-calculated monitor units, leaf motion, and beam arrangement. Additionally, nine hypopharyngeal and laryngeal cancer patients were analyzed in terms of PTV70 for cartilaginous structures (PTV70 cartilage)(.) The doses covering 50% to PTV70 calculated by AAA and PBC were 2.1% +/- 1.0% and 3.7% +/- 0.8% significantly higher than those using Axb, respectively (p < 0.01). The increases in doses to PTV70_cartilage calculated by AAA and PBC relative to Axb were 3.9% and 5.3% on average, respectively, and were relatively greater than those in the entire PTV70. Axb was found to be in better agreement with measurement in phantoms in heterogeneous areas for the 4 MV photon beam. Considering Axb as the standard, AAA and PBC overestimated the IMRT dose for head and neck cancer. The dosimetric differences s

关键词： acuros xb algorithm intensity-modulated radiation therapy head and neck cancer low-energy photon beam heterogeneous media

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Verification and dosimetric impact of acuros xb algorithm on intensity modulated stereotactic radiotherapy for locally persistent nasopharyngeal carcinoma

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MEDICAL PHYSICS 2012年第8期39卷 4705-4714页

作者： Kan, Monica W. K. Leung, Lucullus H. T. Yu, Peter K. N. Princess Margaret Hosp Dept Oncol Hong Kong Hong Kong Peoples R China City Univ Hong Kong Dept Phys & Mat Sci Kowloon Tong Hong Kong Peoples R China

Purpose: The main aim of the current study was to assess the dosimetric impact on intensity modulated stereotactic radiotherapy (IMSRT) for locally persistent nasopharyngeal carcinoma (NPC) due to the recalculation from the Anisotropic Analytical algorithm (AAA) to the recently released acuros xb (Axb) algorithm. The dosimetric accuracy of using Axb in predicting air/tissue interface doses from an open single small field in a simple geometric phantom and intensity modulated small fields in an anthropomorphic phantom was also investigated. Methods: The central axis percentage depth doses (PDD) of a rectangular phantom containing an air cavity were calculated by both AAA and Axb from 6 MV beam with small field sizes (2 x 2 to 5 x 5 cm(2)). These data were compared to PDD measured by thin thermoluminescent dosimeters (TLDs) and Monte Carlo simulations. The doses predicted by AAA and Axb near air/tissue interfaces from five different IMSRT plans were compared to the TLD measured doses in an anthropomorphic phantom. The PTV coverage, conformity and doses to organs at risk (OARs) calculated by AAA and Axb were compared for 12 patients, using identical beam setup, leaves movement and monitor units. Results: Testing using the simple rectangular phantom demonstrated that AAA and Axb overestimated the PDD at the air/tissue interfaces by up to 41% and 6%, respectively, from a 2 x 2 cm(2) field. The secondary build-up curves predicted by Axb caught up well with the measured data at around 2 mm beyond the air cavity. Testing using the anthropomorphic phantom showed that AAA overestimated the doses by up to 10%, while the measured doses matched those of the Axb to within 3%. Using AAA, the planning target coverage represented by 100% of the reference dose was estimated to be 4% higher than using Axb. The averaged minimum dose to the PTV predicted by AAA was about 4% higher and OARs doses 3% to 6% higher compared to Axb. Conclusions: Axb should be used whenever possible as the sta

关键词： acuros xb algorithm stereotactic intensity modulated radiotherapy nasopharyngeal carcinoma target coverage verification

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Volumetric-modulated arc therapy in craniospinal irradiation: a dosimetric analysis of acuros xb and analytical anisotropic algorithm comparing flattened and flattening filter-free beams with different energies

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JOURNAL OF RADIOTHERAPY IN PRACTICE 2021年第2期20卷 196-202页

作者： Tamilarasu, Suresh Saminathan, Madeswaran Rajiv Gandhi Canc Inst & Res Ctr Sect 5 Rohini New Delhi 110085 India VIT Univ Vellore Tamil Nadu India

Aim: To compare the dosimetric performance of flattening filter-free (FFF) beam and flattened beams (FBs) utilising volumetric-modulated arc therapy (VMAT) for craniospinal irradiation (CSI) planning. Materials and Methods: Five medulloblastoma patients were randomly selected retrospectively and 40 plans were generated. The dose prescription to the planning target volume (PTV) was 36 Gy in 20 fractions. VMAT plans were created using 6 MV and 10 MV FB and FFF beam. Final dose calculations were performed using acuros xb (Axb) and analytical anisotropic algorithm (AAA). Dosimetric parameters such as D-98%, D-95%, D-50%, V-110%, conformity index (CI), homogeneity index (HI), low-grade dose index, high-grade dose index, dose to the organ at risks (OARs) and normal tissue mean dose were noted. The effect of low-dose volume on normal tissue was also analysed. Results: The 6 MV and 10 MV flattened and FFF beam plan generates similar target coverage, and a significant difference was observed in the HI and CI. FFF beam plan produces lower doses in some of the OARs as compared to FB. Significant differences were also noted in monitor unit (MU), body-PTV mean dose and low-dose spillage regions (1-10 Gy) outside the PTV. In our study, 6 MV and 10 MV FFF beam beams need 23-25% more MUs to achieve planning goals when compared to FBs. The increased MUs in FFF plan decreases the body-PTV mean dose (0.07-0.09 Gy in 6 MV FFF and 0.31 Gy in 10 MV FFF in both algorithms) when compared to FB plans. Conclusion: FFF beams generate a highly conformal and homogenous plan in CSI cases. FFF beam plan reduced the non-tumour dose and will aid in reducing the probability of second malignancies.

关键词： acuros xb algorithm analytical anisotropic algorithm craniospinal irradiation flattened and flattening filter-free beam

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Clinical implication in the use of the AAA algorithm versus the Axb in nasopharyngeal carcinomas by comparison of TCP and NTCP values

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RADIATION ONCOLOGY 2020年第1期15卷 150-150页

作者： Bufacchi, Antonella Caspiani, Orietta Rambaldi, Giulia Marmiroli, Luca Giovinazzo, Giuseppe Polsoni, Mattia Amethyst Radioterapia Italia S Giovanni Calibita Fatebenefratelli Hosp Med Phys Dept Rome Italy PIOXI Clin Rome Italy Amethyst Radioterapia Italia S Giovanni Calibita Fatebenefratelli Hosp UOC Radiotherapy Rome Italy Amethyst Radioterapia Italia Rome Italy

Purpose Retrospective analysis of volumetric modulated arc therapy treatment plans to investigate qualitative, possible, clinical consequences of the use of AAA versus Axb in nasopharyngeal cancer (NPC) cases. Methods The dose distribution of 26 treatment plans, produced using RapidArc technique and AAA algorithm, were recalculated using Axb and the same number of monitor units provided by AAA and clinically delivered to each patient. The potential clinical effect of dosimetric differences in the planning target volume (PTV) and in organs at risk (OAR) were evaluated by comparing TCP and NTCP values. The Wilcoxon Signed Rank test was used for statistical comparison of all results obtained from the use of the two algorithms. Results The poorer coverage of the PTV, with higher prescribed dose, was reflected in the TCP, which was significantly lower when Axb was used, the median value was 81.55% (range: 74.90, 88.60%) and 84.10% (range: 77.70, 89.90%) for AAA (p < 0.001). OAR mean dose was lower in the Axb recalculated plan than the AAA plan and the difference was statistically significant for all the structures. The NTCP for developing mandible necrosis showed the largest median percentage difference between AAA and Axb (56.6%), the NTCP of risk for larynx edema of Grade >= 2 followed with 12.2%. Conclusions Differences in dose distribution of NPC treatment plans recalculated with Axb are of clinical significance in those situations where the PTV and OAR involve air or bone, media in which Axb has been shown to more accurately represent the true dose distribution. The availability of Axb algorithm could improve patient dose estimation, increasing the data consistency of clinical trials.

关键词： Dose volume histogram Tumor control probability Normal tissue complication probability Anisotropic analytical algorithm acuros xb algorithm

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Experimental verification of the acuros xb and AAA dose calculation adjacent to heterogeneous media for IMRT and RapidArc of nasopharygeal carcinoma

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MEDICAL PHYSICS 2013年第3期40卷 031714-031714页

作者： Kan, Monica W. K. Leung, Lucullus H. T. So, Ronald W. K. Yu, Peter K. N. Princess Margaret Hosp Dept Oncol Kwai Chung Hong Kong Peoples R China City Univ Hong Kong Dept Phys & Mat Sci Kowloon Tong Hong Kong Peoples R China

Purpose: To compare the doses calculated by the acuros xb (Axb) algorithm and analytical anisotropic algorithm (AAA) with experimentally measured data adjacent to and within heterogeneous medium using intensity modulated radiation therapy (IMRT) and RapidArc (R) (RA) volumetric arc therapy plans for nasopharygeal carcinoma (NPC). Methods: Two-dimensional dose distribution immediately adjacent to both air and bone inserts of a rectangular tissue equivalent phantom irradiated using IMRT and RA plans for NPC cases were measured with GafChromic (R) EBT3 films Doses near and within the nasopharygeal (NP) region of an anthropomorphic phantom containing heterogeneous medium were also measured with thermo-luminescent dosimeters (TLD) and EBT3 films. The measured data were then compared with the data calculated by AAA and Axb. For Axb, dose calculations were performed using both dose-to-medium (Axb_D-m) and dose-to-water (Axb_D-w) options. Furthermore, target dose differences between AAA and Axb were analyzed for the corresponding real patients. The comparison of real patient plans was performed by stratifying the targets into components of different densities, including tissue, bone, and air. Results: For the verification of planar dose distribution adjacent to air and bone using the rectangular phantom, the percentages of pixels that passed the gamma analysis with the +/- 3%/3mm criteria were 98.7%, 99.5%, and 97.7% on the axial plane for AAA, Axb_D-m, and Axb_D-w, respectively, averaged over all IMRT and RA plans, while they were 97.6%, 98.2%, and 97.7%, respectively, on the coronal plane. For the verification of planar dose distribution within the NP region of the anthropomorphic phantom, the percentages of pixels that passed the gamma analysis with the +/- 3%/3mm criteria were 95.1%, 91.3%, and 99.0% for AAA, Axb_D-m, and Axb_D-w, respectively, averaged over all IMRT and RA plans. Within the NP region where air and bone were present, the film measurements represented th

关键词： acuros xb algorithm intensity modulated radiotherapy RapidArc heterogeneous media GafChromic EBT3 film anthropomorphic phantom

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The effect of material assignment in nasal cavity on dose calculation for nasopharyngeal carcinoma (NPC) using acuros xb

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JOURNAL OF APPLIED CLINICAL MEDICAL PHYSICS 2022年第8期23卷 e13698页

作者： Cheung, Michael L. M. Chow, Vivian U. Y. Kan, Monica W. K. Chan, Anthony T. C. Prince Wales Hosp Dept Clin Oncol Hong Kong Peoples R China Chinese Univ Hong Kong Dept Clin Oncol Hong Kong Peoples R China

Purpose To evaluate the effect of material assignment in nasal cavity on dose calculation for the volumetric modulated arc therapy (VMAT) of nasopharyngeal carcinoma (NPC) using acuros xb (Axb) algorithm. Methods The VMAT plans of 30 patients with NPC were calculated using Axb with material auto-assignment of nasal cavity to lung and reassignment to air respectively. The doses to the planning target volumes (PTVs) overlapping with nasal cavity with material auto-assignment of lung (Axb_Lung) were compared to the values obtained when nasal cavity was reassigned to air (Axb_Air) under the dose-to-medium (D-m) reporting mode of Axb. Results For dose calculated under Axb_Lung, the D-98%, D-2%, and D-mean of the PTV69.96_Air Cavity (PTV of prescription dose 69.96 Gy overlapping with nasal cavity) were on average 16.1%, 1.6%, and 8.6% larger than that calculated under Axb_Air, respectively. Up to 19.5% difference in D-98%, 3% difference in D-2%, and 11.2% difference in D-mean were observed in the worst cases for PTV69.96. Similar trend was observed for the PTV5940_Air Cavity, in which the D-98%, D-2%, and D-mean calculated under Axb_Lung were on average 14.7%, 2.5%, and 10.2% larger than that calculated under Axb_Air, respectively. In the worst cases, the difference observed in D-98%, D-2%, and D-mean could be up to 17.7%, 4.5%, and 12.7%, respectively. Conclusions Significant dose difference calculated by Axb between the material assignment of lung and air in nasal cavity for NPC cases might imply the possibility of underdosage to the PTVs that overlap with inhomogeneity. Therefore, attention should be put to ensure that accurate material assignment for dose calculation under Axb such that optimal dosage was given for tumor control.

关键词： acuros xb algorithm dose calculation inhomogeneity material assignment nasopharyngeal carcinoma

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Accuracy of dose calculation algorithms for virtual heterogeneous phantoms and intensity-modulated radiation therapy in the head and neck

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RADIOLOGICAL PHYSICS AND TECHNOLOGY 2016年第1期9卷 77-87页

作者： Onizuka, Ryota Araki, Fujio Ohno, Takeshi Nakaguchi, Yuji Kai, Yudai Tomiyama, Yuuki Hioki, Kazunari Kumamoto Univ Grad Sch Hlth Sci 4-24-1 Kuhonji Kumamoto Japan

This study verified the dose calculation accuracy of the analytical anisotropic algorithm (AAA), acuros xb version 10 (Axb10), and version 11 (Axb11) installed in an Eclipse treatment planning system, by comparing with Monte Carlo (MC) simulations. First, the algorithms were compared in terms of dose distributions using four types of virtual heterogeneous multi-layer phantom for 6 and 15 MV photons. Next, the clinical head and neck intensity-modulated radiation therapy (IMRT) dose distributions for 6 MV photons were evaluated using dose volume histograms (DVHs) and three-dimensional gamma analysis. In percentage depth doses (PDDs) for virtual heterogeneous phantoms, AAA overestimated absorbed doses in the air cavity, bone, and aluminum in comparison with MC, Axb10, and Axb11. The PDDs of Axb10 almost agreed with those of MC and Axb11, except for the air cavity. The dose in the air cavity was higher for Axb10 than for Axb11, because their electron cutoff energies are set at 500 and 200 keV, respectively. For head and neck IMRT dose distributions, the D95 in the clinical target volume (CTV) for AAA was almost the same as that for Axb10 and was approximately 7 % larger than that for MC. Comparing each approach with MC using a criterion of 3 %/ 3 mm, the pass rates for Axb10, Axb11, and AAA were 92.4, 94.7, and 90.4 % in the CTV, respectively. In conclusion, AAA produces dose errors in heterogeneous regions, while Axb11 provides calculation accuracy comparable to MC. Axb10 overestimates the dose in regions that include an air cavity.

关键词： Head and neck IMRT acuros xb algorithm Monte Carlo simulation Three-dimensional gamma analysis Dose verification

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The performance of the progressive resolution optimizer (PRO) for RapidArc planning in targets with low-density media

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JOURNAL OF APPLIED CLINICAL MEDICAL PHYSICS 2013年第6期14卷 205-221页

A new version of progressive resolution optimizer (PRO) with an option of air cavity correction has been implemented for RapidArc volumetric-modulated arc therapy (RA). The purpose of this study was to compare the performance of this new PRO with the use of air cavity correction option (PRO10_air) against the one without the use of the air cavity correction option (PRO10_no-air) for RapidArc planning in targets with low-density media of different sizes and complexities. The performance of PRO10_no-air and PRO10_air was initially compared using single-arc plans created for four different simple heterogeneous phantoms with virtual targets and organs at risk. Multiple-arc planning of 12 real patients having nasopharyngeal carcinomas (NPC) and ten patients having non-small cell lung cancer (NSCLC) were then performed using the above two options for further comparison. Dose calculations were performed using both the acuros xb (Axb) algorithm with the dose to medium option and the analytical anisotropic algorithm (AAA). The effect of using intermediate dose option after the first optimization cycle in PRO10_air and PRO10_no-air was also investigated and compared. Plans were evaluated and compared using target dose coverage, critical organ sparing, conformity index, and dose homogeneity index. For NSCLC cases or cases for which large volumes of low-density media were present in or adjacent to the target volume, the use of the air cavity correction option in PRO10 was shown to be beneficial. For NPC cases or cases for which small volumes of both low-and high-density media existed in the target volume, the use of air cavity correction in PRO10 did not improve the plan quality. Based on the Axb dose calculation results, the use of PRO10_air could produce up to 18% less coverage to the bony structures of the planning target volumes for NPC cases. When the intermediate dose option in PRO10 was used, there was negligible difference observed in plan quality between optimizations

关键词： RapidArc optimization algorithm acuros xb algorithm low-density media air cavity correction

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