scholarly journals Impact of delivery characteristics on dose delivery accuracy of volumetric modulated arc therapy for different treatment sites

2019 ◽  
Vol 60 (5) ◽  
pp. 603-611 ◽  
Author(s):  
Jiaqi Li ◽  
Xile Zhang ◽  
Jun Li ◽  
Rongtao Jiang ◽  
Jing Sui ◽  
...  
Keyword(s):  
Volumetric Modulated Arc Therapy ◽  
Dose Delivery ◽  
Small Aperture ◽  
Passing Rates ◽  
Pearson's R ◽  
Arc Therapy ◽  
Key Factor ◽  
Delivery Accuracy ◽  
The Impact ◽  
Pearson’S R

Abstract This study aimed to investigate the impact of delivery characteristics on the dose delivery accuracy of volumetric modulated arc therapy (VMAT) for different treatment sites. The pretreatment quality assurance (QA) results of 344 VMAT patients diagnosed with gynecological (GYN), head and neck (H&N), rectal or prostate cancer were randomly chosen in this study. Ten metrics reflecting VMAT delivery characteristics were extracted from the QA plans. Compared with GYN and rectal plans, H&N and prostate plans had higher aperture complexity and monitor units (MU), and smaller aperture area. Prostate plans had the smallest aperture area and lowest leaf speed compared with other plans (P < 0.001). No differences in gantry speed were found among the four sites. The gamma passing rates (GPRs) of GYN, rectal and H&N plans were inversely associated with union aperture area (UAA) and leaf speed (Pearson’s r: −0.39 to −0.68). GPRs of prostate plans were inversely correlated with aperture complexity, MU and small aperture score (SAS) (absolute Pearson’s r: 0.34 to 0.49). Significant differences in GPR between high SAS and low SAS subgroups were found only when leaf speed was <0.42 cm s–1 (P < 0.001). No association of GPR with gantry speed was found in four sites. Leaf speed was more strongly associated with UAA. Aperture complexity and MU were more strongly associated with SAS. VMAT plans from different sites have distinct delivery characteristics. Affecting dose delivery accuracy, leaf speed is the key factor for GYN, rectal and H&N plans, while aperture complexity, MU and small apertures have a higher influence on prostate plans.

scholarly journals Impact of Dynamic Parameters on Dose Delivery Accuracy in Volumetric Modulated Arc Therapy

2014 ◽  
Vol 70 (8) ◽  
pp. 768-772
Author(s):  
Fumiyasu Matsubayashi ◽  
Ryo Takahashi ◽  
Yasushi Ito ◽  
Takeo Hashimoto ◽  
Satoko Saotome ◽  
...  
Keyword(s):  
Volumetric Modulated Arc Therapy ◽  
Dynamic Parameters ◽  
Dose Delivery ◽  
Arc Therapy ◽  
Delivery Accuracy

Gamma-index method sensitivity for gauging plan delivery accuracy of volumetric modulated arc therapy

2015 ◽  
Vol 31 (8) ◽  
pp. 1118-1122 ◽  
Author(s):  
Jong In Park ◽  
Jong Min Park ◽  
Jung-in Kim ◽  
So-Yeon Park ◽  
Sung-Joon Ye
Keyword(s):  
Volumetric Modulated Arc Therapy ◽  
Index Method ◽  
Gamma Index ◽  
Arc Therapy ◽  
Delivery Accuracy

scholarly journals HETEROFOR 1.0: a spatially explicit model for exploring the response of structurally complex forests to uncertain future conditions. II. Phenology and water cycle

2019 ◽  
Author(s):  
Louis de Wergifosse ◽  
Frédéric André ◽  
Nicolas Beudez ◽  
François de Coligny ◽  
Hugues Goosse ◽  
...  
Keyword(s):  
Climate Change ◽  
Water Balance ◽  
Tree Growth ◽  
Leaf Development ◽  
Forest Growth ◽  
Spatially Explicit ◽  
Model Assessment ◽  
Pearson's R ◽  
The Impact ◽  
Pearson’S R

Abstract. Climate change affects forest growth in numerous and sometimes opposite ways and the resulting trend is often difficult to predict for a given site. Integrating and structuring the knowledge gained from the monitoring and experimental studies into process-based models is an interesting approach to predict the response of forest ecosystems to climate change. While the first generation of such models operates at stand level, we need now individual-based and spatially-explicit approaches in order to account for structurally complex stands whose importance is increasingly recognized in the changing environment context. Among the climate-sensitive drivers of forest growth, phenology and water availability are often cited as crucial elements. They influence, for example, the length of the vegetation period during which photosynthesis takes place and the stomata opening, which determines the photosynthesis rate. In this paper, we describe the phenology and water balance modules integrated in the tree growth model HETEROFOR and evaluate them on six Belgian sites. More precisely, we assess the ability of the model to reproduce key phenological processes (budburst, leaf development, yellowing and fall) as well as water fluxes. Three variants are used to predict budburst (Uniforc, Unichill and Sequential), which differ regarding the inclusion of chilling and/or forcing periods and the calculation of the coldness or heat accumulation. Among the three, the Sequential approach is the least biased (overestimation of 2.46 days) while Uniforc (chilling not considered) best accounts for the interannual variability (Pearson’s R = 0.68). For the leaf development, yellowing and fall, predictions and observation are in accordance. Regarding the water balance module, the predicted throughfall is also in close agreement with the measurements (Pearson’s R = 0.856, bias = −1.3 %) and the soil water dynamics across the year is well-reproduced for all the study sites (Pearson’s R comprised between 0.893 and 0.950, and bias between −1.81 and −9.33 %). The positive results from the model assessment will allow us to use it reliably in projection studies to evaluate the impact of climate change on tree growth and test how diverse forestry practices can adapt forests to these changes.

Evaluation of the Impact of the Linac MLC and Gantry Sag in volumetric modulated arc therapy

2019 ◽  
Vol 46 (5) ◽  
pp. 1984-1994
Author(s):  
Thomas Milan ◽  
Garry Grogan ◽  
Martin A. Ebert ◽  
Pejman Rowshanfarzad
Keyword(s):  
Volumetric Modulated Arc Therapy ◽  
Arc Therapy ◽  
The Impact

Choice of appropriate beam model and gantry rotational angle for low-dose gradient-based craniospinal irradiation using volumetric-modulated arc therapy

2016 ◽  
Vol 16 (1) ◽  
pp. 53-64 ◽  
Author(s):  
Biplab Sarkar ◽  
Anirudh Pradhan
Keyword(s):  
Low Dose ◽  
Volumetric Modulated Arc Therapy ◽  
Craniospinal Irradiation ◽  
Leaf Width ◽  
Beam Model ◽  
Significant Difference ◽  
Arc Therapy ◽  
Prescription Dose ◽  
Flat Beam ◽  
The Impact

AbstractObjectivesWe aimed to assess the impact of advanced multileaf collimator (MLC) models and flattening filter-free (3F) beam in volumetric-modulated arc therapy (VMAT)-based craniospinal irradiation (CSI).MethodsCT scans of five medulloblastoma patients who previously received CSI at our hospital were used for the present study. Patients were planned for a prescription dose of 35 Gy to craniospinal axis. A three-dimensional conformal radiotherapy (3DCRT) plan and a VMAT plan using 1 cm MLC leaf width were generated as the gold standard (reference arm). Test VMAT plans were generated using Agility MLC model (MLC leaf width 5 mm) for various combinations of flattened beam (F) and 3F beam for treating the brain and spine planning target volume (PTV). Organs at risks (OARs) were analysed for dose 5, 50, 75 and 90% volumes, mean dose and maximum dose.ResultsAll 3DCRT plans and VMAT plans were aimed to cover 95% of PTV by at least 95% prescription dose. VMAT demonstrated lesser dose spillage than 3DCRT to body volume minus PTV (NTID: non tumor integral dose) for a dose threshold above 7·5 Gy. For the low-dose range (1–7 Gy), variation between the dose coverage between all VMAT plans (for either spine or brain PTV) was <1%. Intra-VMAT plan dose variation for all OAR’s for all tested parameters was <1 Gy. Average monitor unit (MU) difference among different VMAT plans ranged between 1·52 and 2·13 when normalised to 3DCRT MU. For VMAT plans, flat beam with 1 cm MLC showed the highest MU, whereas Agility MLC with 3F beam had the least MU values for intra-VMAT plans. No statistical significance variation (p) was observed in between reference arm and test arm plans except for mean dose and V107% for PTV spine. When compared between reference arm 3DCRT and test arm VMAT plans. For OAR’s, no statistical difference was observed between reference and test arm VMAT plans.ConclusionsReference arm plans and test arm plans exhibit no statistically significant difference. However, as compared with 3DCRT, VMAT plans are more conformal and produce lesser dose to OAR at the cost of higher delivered MU. 3F beams or finer width MLC’s (width <5 mm) have no advantage over the conventional 1 cm MLC and flat beam except that 3F beams have a shorter beam delivery time. This study demonstrate a significantly lesser spillage dose to NTID/body that of the reported literature, which is attributed to limited rotational arc length used for VMAT plans.

scholarly journals Improving Delivery Accuracy of Stereotactic Body Radiotherapy to a Moving Tumor Using Simplified Volumetric Modulated Arc Therapy

PLoS ONE ◽  
2016 ◽  
Vol 11 (6) ◽  
pp. e0158053 ◽  
Author(s):  
Young Eun Ko ◽  
Byungchul Cho ◽  
Su Ssan Kim ◽  
Si Yeol Song ◽  
Eun Kyung Choi ◽  
...  
Keyword(s):  
Stereotactic Body Radiotherapy ◽  
Volumetric Modulated Arc Therapy ◽  
Arc Therapy ◽  
Delivery Accuracy

scholarly journals Adjuvant volumetric modulated arc therapy compared to 3D conformal radiation therapy for newly diagnosed soft tissue sarcoma of the extremities: outcome and toxicity evaluation

2019 ◽  
Vol 92 (1102) ◽  
pp. 20190252 ◽  
Author(s):  
Lucia Di Brina ◽  
Antonella Fogliata ◽  
Pierina Navarria ◽  
Giuseppe D'Agostino ◽  
Ciro Franzese ◽  
...  
Keyword(s):  
Radiation Therapy ◽  
Soft Tissue ◽  
Soft Tissue Sarcoma ◽  
Total Dose ◽  
Surgical Resection ◽  
Local Control ◽  
Volumetric Modulated Arc Therapy ◽  
Conformal Radiation Therapy ◽  
Arc Therapy ◽  
The Impact

Objective: To assess the impact of adjuvant volumetric modulated arc therapy (VMAT) compared with three-dimensional conformal radiation therapy (3DCRT) in terms of toxicity and local control (LC) in patients with soft tissue sarcoma of the extremities. Methods: From 2004 to 2016, 109 patients were treated, initially using 3DCRT and subsequently with VMAT. Clinical outcome was evaluated by contrast-enhanced MRI, thoracic and abdominal CT 3 months after treatments and then every 6 months. Toxicity was evaluated with Common Terminology Criteria for Adverse Events scale v. 4.3. Results: Patients presented Stage III soft tissue sarcoma disease (77%), localized tumor (95%) at the lower extremity (87%), adipocytic histotype (46%). Surgical resection was performed in all patients, followed by adjuvant 3DCRT in 38, and VMAT in 71. The median total dose was 66 Gy/33 fractions (range 60–70 Gy;25–35 fractions). More successful bone sparing was recorded using VMAT (p < 0.001). Median follow-up was 61 months, 93 and 58 months for 3DCRT and VMAT group, respectively. The 2- and 5 year LC were 95.3±2.1%, and 87.4±3.4% for the whole cohort, 92.0±4.5%, 82.9±6.4% for 3DCRT, 97.1±2.0%, 89.6±4.1% for VMAT (p = 0.150). On univariate and multivariate analysis the factors recorded as conditioning LC were the status of the surgical resection margins (p = 0.028) and the total dose delivered (p = 0.013). Conclusion: The availability of modern radiotherapy technique permit a better conformity on the target with maximum sparing of normal tissue and acceptable side-effects. VMAT is a safe and feasible treatment with limited rate of toxicity, compared to 3DCRT. Results on LC of VMAT are encouraging. Advances in knowledge: Soft tissue sarcoma of the extremities can benefit from the use of VMAT, with a reduction of the high dose to bones to avoid radiation osteonecrosis. An adequate total dose of at least 66 Gy and a radical surgical margin allow a good local control.

Plan Complexity and Delivery Accuracy of Knowledge-based Volumetric Modulated Arc Therapy Plans with Single Optimization for Oropharyngeal Cancer

2021 ◽  
Vol 41 (6) ◽  
pp. 2925-2931
Author(s):  
KATSUYA OKUHATA ◽  
HAJIME MONZEN ◽  
MIKOTO TAMURA ◽  
KENJI MATSUMOTO ◽  
MASAKAZU OTSUKA ◽  
...  
Keyword(s):  
Oropharyngeal Cancer ◽  
Volumetric Modulated Arc Therapy ◽  
Knowledge Based ◽  
Arc Therapy ◽  
Delivery Accuracy
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