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GTV-based prescription in SBRT for lung lesions using advanced dose calculation algorithms

RADIATION ONCOLOGY 2014年第1期9卷 1-10页

作者： Lacornerie, Thomas Lisbona, Albert Mirabel, Xavier Lartigau, Eric Reynaert, Nick Ctr Oscar Lambret Serv Phys Med F-59020 Lille France Inst Cancerol Ouest Serv Phys Med Nantes France Ctr Oscar Lambret Dept Univ Radiotherapie F-59020 Lille France

Background: The aim of current study was to investigate the way dose is prescribed to lung lesions during SBRT using advanced dose calculation algorithms that take into account electron transport (type B algorithms). As type A algorithms do not take into account secondary electron transport, they overestimate the dose to lung lesions. Type B algorithms are more accurate but still no consensus is reached regarding dose prescription. The positive clinical results obtained using type A algorithms should be used as a starting point. Methods: In current work a dose-calculation experiment is performed, presenting different prescription methods. Three cases with three different sizes of peripheral lung lesions were planned using three different treatment platforms. For each individual case 60 Gy to the PTV was prescribed using a type A algorithm and the dose distribution was recalculated using a type B algorithm in order to evaluate the impact of the secondary electron transport. Secondly, for each case a type B algorithm was used to prescribe 48 Gy to the PTV, and the resulting doses to the GTV were analyzed. Finally, prescriptions based on specific GTV dose volumes were evaluated. Results: When using a type A algorithm to prescribe the same dose to the PTV, the differences regarding median GTV doses among platforms and cases were always less than 10% of the prescription dose. The prescription to the PTV based on type B algorithms, leads to a more important variability of the median GTV dose among cases and among platforms, (respectively 24%, and 28%). However, when 54 Gy was prescribed as median GTV dose, using a type B algorithm, the variability observed was minimal. Conclusion: Normalizing the prescription dose to the median GTV dose for lung lesions avoids variability among different cases and treatment platforms of SBRT when type B algorithms are used to calculate the dose. The combination of using a type A algorithm to optimize a homogeneous dose in the PTV and usin

关键词： Prescription dose dose calculation Lung Lesion Electronic Equilibrium dose calculation algorithm

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A comparison between anisotropic analytical and multigrid superposition dose calculation algorithms in radiotherapy treatment planning

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MEDICAL DOSIMETRY 2013年第2期38卷 209-214页

作者： Wu, Vincent W. C. Tse, Teddy K. H. Ho, Cola L. M. Yeung, Eric C. Y. Hong Kong Polytech Univ Dept Hlth Technol & Informat Kowloon Hong Kong Peoples R China

Monte Carlo (MC) simulation is currently the most accurate dose calculation algorithm in radiotherapy planning but requires relatively long processing time. Faster model-based algorithms such as the anisotropic analytical algorithm (AAA) by the Eclipse treatment planning system and multigrid superposition (MGS) by the XiO treatment planning system are 2 commonly used algorithms. This study compared AAA and MGS against MC, as the gold standard, on brain, nasopharynx, lung, and prostate cancer patients. Computed tomography of 6 patients of each cancer type was used. The same hypothetical treatment plan using the same machine and treatment prescription was computed for each case by each planning system using their respective dose calculation algorithm. The doses at reference points including (1) soft tissues only, (2) bones only, (3) air cavities only, (4) soft tissue-bone boundary (Soft/Bone), (5) soft tissue-air boundary (Soft/Air), and (6) bone-air boundary (Bone/Air), were measured and compared using the mean absolute percentage error (MAPE), which was a function of the percentage dose deviations from MC. Besides, the computation time of each treatment plan was recorded and compared. The MAPEs of MGS were significantly lower than AAA in all types of cancers (p < 0.001). With regards to body density combinations, the MAPE of AAA ranged from 1.8% (soft tissue) to 4.9% (Bone/Air), whereas that of MGS from 1.6% (air cavities) to 2.9% (Soft/Bone). The MAPEs of MGS (2.6% +/- 2.1) were significantly lower than that of AAA (3.7% +/- 2.5) in all tissue density combinations (p < 0.001). The mean computation time of AAA for all treatment plans was significantly lower than that of the MGS (p < 0.001). Both AAA and MGS algorithms demonstrated dose deviations of less than 4.0% in most clinical cases and their performance was better in homogeneous tissues than at tissue boundaries. In general, MGS demonstrated relatively smaller dose deviations than AAA but required longer comput

关键词： dose calculation algorithm Anisotropic analytical algorithm (AAA) Multigrid superposition (MGS) algorithm Radiotherapy treatment planning

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Dependence of volume dose indices on dose calculation algorithms for VMAT-SBRT plans for peripheral lung tumor

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MEDICAL DOSIMETRY 2019年第3期44卷 284-290页

作者： Matsuoka, Takanori Araki, Fujio Ohno, Takeshi Sakata, Junichi Tominaga, Hirofumi Kumamoto Univ Grad Sch Hlth Sci Kumamoto Japan Kumamoto Univ Fac Life Sci Dept Hlth Sci Kumamoto Japan Kumamoto Radiosurg Clin Kumamoto Japan Varian Med Syst Tokyo 1030026 Japan

The purpose of this study was to investigate the dependence of volume dose indices on dose calculation algorithms for volumetric modulated arc therapy (VMAT) for stereotactic body radiotherapy (SBRT) plans to treat peripheral lung tumors by comparing them with those of Monte Carlo (MC) calculations. VMAT-SBRT plans for peripheral lung tumors were created using the Eclipse treatment planning system (TPS) for 24 patients with nonsmall cell lung cancer. VMAT dose distributions for gross tumor volume (GTV), internal target volume (ITV), and planning target volume (PTV) were calculated using the analytical anisotropic algorithm (AAA), the Acuros XB (AXB) algorithm, and a MC algorithm. VMAT dose distributions of the 3 algorithms were compared using their volume dose indices from dose volume histograms (DVHs), a dose difference map, and 3-dimensional gamma analysis. The DVHs for GTV and ITV from AAA, AXB, and MC were in good agreement. The difference between the ITV and PTV volume dose indices from AAA and MC increased as D-98, D-95, D-80, D-50, and D-2. In particular, the difference between D-98 for PTV from AAA and MC was up to 48%. A >5% difference between D-95 for PTV from AAA and MC was 11 patients, but only 2 patients for ITV. The volume dose indices for AXB were near those of MC. AAA tended to overestimate the PTV volume dose indices compared to AXB and MC. Thus, we propose that the volume dose indices for the ITV be used because they are independent of dose calculation algorithms. (C) 2018 American Association of Medical Dosimetrists. Published by Elsevier Inc. All rights reserved.

关键词： Monte Carlo (MC) dose calculation algorithm Volume prescription Peripheral lung tumor Stereotactic body radiotherapy

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Comparison of CCC and ETAR dose calculation algorithms in pituitary adenoma radiation treatment planning;Monte Carlo evaluation

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JOURNAL OF RADIOTHERAPY IN PRACTICE 2014年第4期13卷 447-455页

作者： Tanha, K. Mahdavi, S. R. Geraily, G. Univ Tehran Med Sci Dept Med Phys Tehran Iran Iran Univ Med Sci Dept Med Phys Tehran Iran

Aims: To verify the accuracy of two common absorbed dose calculation algorithms in comparison to Monte Carlo (MC) simulation for the planning of the pituitary adenoma radiation treatment. Materials and methods: After validation of Linac's head modelling by MC in water phantom, it was verified in Rando phantom as a heterogeneous medium for pituitary gland irradiation. Then, equivalent tissue- air ratio (ETAR) and collapsed cone convolution (CCC) algorithms were compared for a conventional three small non- coplanar field technique. This technique uses 30 degree physical wedge and 18 MV photon beams. Results: dose distribution findings showed significant difference between ETAR and CCC of delivered dose in pituitary irradiation. The differences between MC and dose calculation algorithms were 6.40 +/- 3.44% for CCC and 10.36 +/- 4.37% for ETAR. None of the algorithms could predict actual dose in air cavity areas in comparison to the MC method. Conclusions: Difference between calculation and true dose value affects radiation treatment outcome and normal tissue complication probability. It is of prime concern to select appropriate treatment planning system according to our clinical situation. It is further emphasised that MC can be the method of choice for clinical dose calculation algorithms verification.

关键词： CCC dose calculation algorithm ETAR Monte Carlo simulation treatment planning system

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Quantitative evaluation of dosimetric uncertainties in electron therapy by measurement and calculation using the electron Monte Carlo dose algorithm in the Eclipse treatment planning system

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JOURNAL OF APPLIED CLINICAL MEDICAL PHYSICS 2022年第1期23卷 e13478页

作者： Ali, Imad Alsbou, Nesreen Ahmad, Salahuddin Univ Oklahoma Hlth Sci Ctr Dept Radiat Oncol Oklahoma City OK USA Univ Cent Oklahoma Dept Engn & Phys Edmond OK USA

In the electron beam radiation therapy, customized blocks are mostly used to shape treatment fields to generate conformal doses. The goal of this study is to investigate quantitatively dosimetric uncertainties associated with heterogeneities, detectors used in the measurement of the beam data commissioning, and modeling of the interactions of high energy electrons with tissue. These uncertainties were investigated both by measurements with different detectors and calculations using electron Monte Carlo algorithm (eMC) in the Eclipse treatment planning system. dose distributions for different field sizes were calculated using eMC and measured with a multiple-diode-array detector (MapCheck2) for cone sizes ranging from 6 to 25 cm. The dose distributions were calculated using the CT images of the MapCheck2 and water-equivalent phantoms. In the umbra region (<20% isodose line), the eMC underestimated dose by a factor of 3 for high energy electron beams due to lack of consideration of bremsstrahlung emitted laterally that was not accounted by eMC in the low dose region outside the field. In the penumbra (20%-80% isodose line), the eMC overestimated dose (40%) for high energy 20 MeV electrons compared to the measured dose with small diodes in the high gradient dose region. This was mainly due to lack of consideration of volume averaging of the ion chamber used in beam data commissioning which was input to the eMC dose calculation algorithm. Large uncertainties in the CT numbers (25%) resulted from the image artifacts in the CT images of the MapCheck2 phantom due to metal artifacts. The eMC algorithm used the electron and material densities extracted from the CT numbers which resulted large dosimetric uncertainties (10%) in the material densities and corresponding stopping power ratios. The dose calculations with eMC are associated with large uncertainties particularly in penumbra and umbra regions and around heterogeneities which affect the low dose level that cover nearb

关键词： bremsstrahlung commissioning data dose calculation algorithm dosimetric uncertainties heterogeneity correction image artifacts

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Dosimetric verification of four dose calculation algorithms for spine stereotactic body radiotherapy

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JOURNAL OF RADIATION RESEARCH 2024年第1期65卷 109-118页

作者： Hirashima, Hideaki Nakamura, Mitsuhiro Nakamura, Kiyonao Matsuo, Yukinori Mizowaki, Takashi Kyoto Univ Grad Sch Med Dept Radiat Oncol & Image Appl Therapy 54 Kawahara ChoSakyo Ku Kyoto 6068507 Japan Kyoto Univ Grad Sch Med Dept Adv Med Phys 53 Kawahara ChoSakyo Ku Kyoto 6068507 Japan

The applications of Type B [anisotropic analytical algorithm (AAA) and collapsed cone (CC)] and Type C [Acuros XB (AXB) and photon Monte Carlo (PMC)] dose calculation algorithms in spine stereotactic body radiotherapy (SBRT) were evaluated. Water- and bone-equivalent phantoms were combined to evaluate the percentage depth dose and dose profile. Subsequently, 48 consecutive patients with clinical spine SBRT plans were evaluated. All treatment plans were created using AXB in Eclipse. The prescription dose was 24 Gy in two fractions at a 10 MV FFF on TrueBeam. The doses were then recalculated with AAA, CC and PMC while maintaining the AXB-calculated monitor units and beam arrangement. The dose index values obtained using the four dose calculation algorithms were then compared. The AXB and PMC dose distributions agreed with the bone-equivalent phantom measurements (within +/- 2.0%);the AAA and CC values were higher than those in the bone-equivalent phantom region. For the spine SBRT plans, PMC, AAA and CC were overestimated compared with AXB in terms of the near minimum and maximum doses of the target and organ at risk, respectively;the mean dose difference was within 4.2%, which is equivalent with within 1 Gy. The phantom study showed that the results from AXB and PMC agreed with the measurements within +/- 2.0%. However, the mean dose difference ranged from 0.5 to 1 Gy in the spine SBRT planning study when the dose calculation algorithms changed. Users should incorporate a clinical introduction that includes an awareness of these differences.

关键词： dosimetric verification dose calculation algorithm spine SBRT

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Impact of dose calculation accuracy during optimization on lung IMRT plan quality

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JOURNAL OF APPLIED CLINICAL MEDICAL PHYSICS 2015年第1期16卷 219-228页

作者： Li, Ying Rodrigues, Anna Li, Taoran Yuan, Lulin Yin, Fang-Fang Wu, Q. Jackie Duke Univ Med Ctr Dept Radiat Oncol Durham NC 27710 USA Chongqing Med Univ Affiliated Hosp 1 Dept Oncol Chongqing Peoples R China Duke Univ Med Ctr Med Phys Grad Program Durham NC 27710 USA

The purpose of this study was to evaluate the effect of dose calculation accuracy and the use of an intermediate dose calculation step during the optimization of intensity-modulated radiation therapy (IMRT) planning on the final plan quality for lung cancer patients. This study included replanning for 11 randomly selected free-breathing lung IMRT plans. The original plans were optimized using a fast pencil beam convolution algorithm. After optimization, the final dose calculation was performed using the analytical anisotropic algorithm (AAA). The Varian Treatment Planning System (TPS) Eclipse v11, includes an option to perform intermediate dose calculation during optimization using the AAA. The new plans were created using this intermediate dose calculation during optimization with the same planning objectives and dose constraints as in the original plan. Differences in dosimetric parameters for the planning target volume (PTV) dose coverage, organs-at-risk (OARs) dose sparing, and the number of monitor units (MU) between the original and new plans were analyzed. Statistical significance was determined with a p-value of less than 0.05. All plans were normalized to cover 95% of the PTV with the prescription dose. Compared with the original plans, the PTV in the new plans had on average a lower maximum dose (69.45 vs. 71.96Gy, p = 0.005), a better homogeneity index (HI) (0.08 vs. 0.12, p = 0.002), and a better conformity index (CI) (0.69 vs. 0.59, p = 0.003). In the new plans, lung sparing was increased as the volumes receiving 5, 10, and 30 Gy were reduced when compared to the original plans (40.39% vs. 42.73%, p = 0.005;28.93% vs. 30.40%, p = 0.001;14.11% vs. 14.84%, p = 0.031). The volume receiving 20 Gy was not significantly lower (19.60% vs. 20.38%, p = 0.052). Further, the mean dose to the lung was reduced in the new plans (11.55 vs. 12.12 Gy, p = 0.024). For the esophagus, the mean dose, the maximum dose, and the volumes receiving 20 and 60 Gy were lower in the

关键词： lung cancer intensity-modulated radiation therapy dose calculation algorithm optimization treatment planning

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dose calculation accuracies in whole breast radiotherapy treatment planning: a multi-institutional study

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RADIOLOGICAL PHYSICS AND TECHNOLOGY 2015年第2期8卷 200-208页

作者： Hatanaka, Shogo Miyabe, Yuki Tohyama, Naoki Kumazaki, Yu Kurooka, Masahiko Okamoto, Hiroyuki Tachibana, Hidenobu Kito, Satoshi Wakita, Akihisa Ohotomo, Yuko Ikagawa, Hiroyuki Ishikura, Satoshi Nozaki, Miwako Kagami, Yoshikazu Hiraoka, Masahiro Nishio, Teiji Saitama Med Univ Saitama Med Ctr Dept Radiat Oncol Kawagoe Saitama 3508550 Japan Kyoto Univ Grad Sch Med Dept Radiat Oncol & Image Appl Therapy Sakyo Ku Kyoto Kyoto 6068507 Japan Tokyo Bay Adv Imaging & Radiat Oncol Clin Dept Radiat Oncol Mihama Ku Chiba Chiba 2610024 Japan Saitama Med Univ Int Med Ctr Dept Radiat Oncol Hidaka City Saitama 3501298 Japan Kanagawa Canc Ctr Dept Radiat Oncol Asahi Ku Yokohama Kanagawa 2418515 Japan Natl Canc Ctr Dept Radiat Oncol Chuo Ku Tokyo 1040045 Japan Japanese Fdn Canc Res Canc Inst Hosp Dept Radiat Oncol Koto Ku Tokyo 1358550 Japan Komagome Hosp Tokyo Metropolitan Canc & Infect Dis Ctr Dept Radiotherapy Bunkyo Ku Tokyo 1138677 Japan Shiga Med Ctr Adults Dept Radiol Moriyama Shiga 5248524 Japan Koshigaya Municipal Hosp Dept Radiol Koshigaya Saitama 3438577 Japan

Our objective in this study was to evaluate the variation in the doses delivered among institutions due to dose calculation inaccuracies in whole breast radiotherapy. We have developed practical procedures for quality assurance (QA) of radiation treatment planning systems. These QA procedures are designed to be performed easily at any institution and to permit comparisons of results across institutions. The dose calculation accuracy was evaluated across seven institutions using various irradiation conditions. In some conditions, there was a >3 difference between the calculated dose and the measured dose. The dose calculation accuracy differs among institutions because it is dependent on both the dose calculation algorithm and beam modeling. The QA procedures in this study are useful for verifying the accuracy of the dose calculation algorithm and of the beam model before clinical use for whole breast radiotherapy.

关键词： Radiation treatment planning system Whole breast radiotherapy Quality assurance dose calculation algorithm Multi-institutional study

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Impact of TPS calculation algorithms on dose delivered to the patient in proton therapy treatments

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PHYSICS IN MEDICINE AND BIOLOGY 2019年第7期64卷 075016-075016页

作者： Molinelli, Silvia Russo, Stefania Magro, Giuseppe Maestri, Davide Mairani, Andrea Mastella, Edoardo Mirandola, Alfredo Vai, Alessandro Vischioni, Barbara Valvo, Francesca Ciocca, Mario Fdn CNAO Str Campeggi 53 I-27100 Pavia Italy Univ Milan I-20133 Milan Italy Heidelberg Ion Beam Therapy Ctr Neuenheimer Feld 450 D-69120 Heidelberg Germany

To estimate the impact of dose calculation approaches adopted in different treatment planning systems (TPSs) on proton therapy dose delivered with pencil beam scanning (PBS). Treatment plans for six regular volumes in water and 15 clinical cases were optimized with Syngo-VC13 and exported for forward recalculation with Raystation-V7.0 pencil beam (RS-PBA) and Monte Carlo (RS-MC) algorithms and with the independent Fluka-MC engine. To verify clinical consistency between the two TPS dosimetric outcomes, the average percentage variations of clinical target volume (CTV) D-98%, D(50)(% )and D-2(%), adopted for plan prescription and evaluation, were considered. Ionization chamber measurements served as a further reference for comparison in homogeneous conditions. CTV dose volume histogram (DVH) analysis and gamma evaluation with 3 mm-3% agreement criteria quantified the dose deviation of TPS calculation algorithms, in heterogeneous conditions, against the Fluka-MC code. CTV D-50%, representing the plan dose prescription goal, was higher on average over H&N cases of (3.9 +/- 0.9)% and (2.3 +/- 0.6)% as calculated with RS-PBA and RS-MC, respectively, compared to Syngo. For tumors located in the pelvis district, average D-50% variations of (1.6 +/- 0.7)% and (1.2 +/- 0.7)% were found. Syngo underestimated target near maximum doses with respect to all computation systems. calculation accuracy in heterogeneous conditions of RS-PBA H&N plans resulted poor when a range shifter was required. Target DVH and gamma-analysis showed excellent agreement between RS-MC and Fluka-MC, with gamma-pass rates >98% for all patient groups. Different TPS dose calculation approaches mainly affected dose delivered in H&N proton treatments, while minor deviations were found for pelvic tumors. RS-MC proved to be the most accurate TPS dose calculation algorithm when compared to an independent MC simulation code.

关键词： proton therapy dose calculation algorithm treatment planning

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A polar-coordinate-based pencil beam algorithm for VMAT dose computation with high-resolution gantry angle sampling

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MEDICAL PHYSICS 2022年第6期49卷 4026-4042页

作者： Tseng, Wenchih Yan, Guanghua Liu, Hongcheng Kahler, Darren Li, Jonathan Liu, Chihray Lu, Bo Univ Florida Dept Radiat Oncol Gainesville FL 32610 USA Univ Florida Dept Ind & Syst Engn Gainesville FL 32610 USA

Purpose Most commercially available treatment planning systems (TPSs) approximate the continuous delivery of volumetric modulated arc therapy (VMAT) plans with a series of discretized static beams for treatment planning, which can make VMAT dose computation extremely inefficient. In this study, we developed a polar-coordinate-based pencil beam (PB) algorithm for efficient VMAT dose computation with high-resolution gantry angle sampling that can improve the computational efficiency and reduce the dose discrepancy due to the angular under-sampling effect. Methods and Materials 6 MV 1x1mm(2) pencil beams were simulated on a uniform cylindrical phantom under an EGSnrc Monte Carlo (MC) environment. The MC-generated PB kernels were collected in the polar coordinate system for each bixel on a 40x40cm(2) fluence map and subsequently fitted via a series of Gaussians. The fluence was calculated using a detectors' eye view with off-axis and MLC transmission factors corrected. doses of VMAT arc on the phantom were computed by summing the convolution results between the corresponding PB kernels and fluence for each bixel in the polar coordinate system. The convolution was performed using fast Fourier transform to expedite the computing speed. The calculated doses were converted to the Cartesian coordinate system and compared with the reference dose computed by a collapsed cone convolution (CCC) algorithm of the TPS. A heterogeneous phantom was created to study the heterogeneity corrections using the proposed algorithm. Ten VMAT arcs were included to evaluate the algorithm performance. Gamma analysis and computation complexity theory were used to measure the dosimetric accuracy and computational efficiency, respectively. Results The dosimetric comparisons on the homogeneous phantom between the proposed PB algorithm and the CCC algorithm for 10 VMAT arcs demonstrate that the proposed algorithm can achieve a dosimetric accuracy comparable to that of the CCC algorithm with average g

关键词： dose calculation algorithm fast Fourier transform pencil beam model polar coordinate system VMAT

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