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Aim

This work aims to achieve the highest possible monitor units (MU) reduction using the MU Objective tool included in the Eclipse treatment planning system, while preserving the plan quality.

Background

The treatment planning system Eclipse (Varian Medical Systems, Palo Alto, CA) includes a control mechanism for the number of monitor units of volumetric modulated arc therapy (VMAT) plans, named the MU Objective tool.

Material and methods

Forty prostate plans, 20 gynecological plans and 20 head and neck plans designed with VMAT were retrospectively studied. Each plan (base plan) was optimized without using the MU Objective tool, and it was re-optimized with different values of the Maximum MU (MaxMU) parameter of the MU Objective tool. MU differences were analyzed with a paired samples t-test and changes in plan quality were assessed with a set of parameters for OARs and PTVs.

Results

The average relative MU difference (ΔMU¯) considering all treatment sites, was the highest when MaxMU = 400 (?4.2%, p < 0.001). For prostate plans, the lowest ΔMU¯ was obtained (?3.7%, p < 0.001). For head and neck plans ΔMU¯ was ?7.3% (p < 0.001) and for gynecological plans ΔMU¯ was 7.0% (p = 0.002). Although similar MU reductions were observed for both sites, for some gynecological plans maximum differences were greater than 10%. All the assessed parameters for PTVs and OARs sparing showed average differences below 2%.

Conclusion

For the three studied clinical sites, establishing MaxMU = 400 led to the optimum MU reduction, maintaining the original dose distribution and dosimetric parameters practically unaltered.  相似文献   

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A. Szwed  M. Kosińska 《HOMO》2012,63(4):292-300
The main aim of the study was to assess the influence of biological maturity at birth on growth processes in the subsequent years and during puberty in girls. The material of this study comes from the outpatient clinic cards and cross-sectional research on girls from the province of Wielkopolska in Poland. It includes data of 527 girls. The influence of perinatal maturity on body weight in the later stages of ontogeny was determined with the use of the Kruskal–Wallis test and the Mann–Whitney U test. In order to determine the relationship between perinatal maturity and age at menarche, the survival analysis module was used.The results show a diverse influence of perinatal maturity on the values of body weight achieved in later years of life. The indicated predictive factors included both birth weight and gestational age. In the examined girls menarche occurred between the 10th year and the 17th year of life (X¯=12.87, s = 1.26; Me = 13 years). The comparison showed a significant variation in age at menarche depending on the length of pregnancy (log-rank χ22=27.068, p < 0.0001) and birth weight (log-rank χ22=23.241, p < 0.0001). There was no variation in maturation of the examined girls conditioned by the occurrence of intra-uterine growth retardation (log-rank χ22=2.046, p > 0.05). Remote prognoses as to the postnatal development of preterm-born children and/or children with low birth weight indicate adverse influence of these variables on age at menarche. Perinatal biological maturity of a newborn conditions the course of postnatal development.  相似文献   

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B. Floyd  L. Jayasinghe  C. Dey 《HOMO》2017,68(3):236-241
This study evaluates height loss during the day in light of variables assessable through participant self-report. Participants were 19 female and 15 male staff and students who met with us twice with a mean interval between measurement sessions of 6.96 h (SD = 0.86). Hypotheses were evaluated using two-stage least squares regression analysis (SYSTAT 10). Males and females lost similar amounts of height between sessions (male,x¯=6.9mm;female,x¯=7.4mm). Among factors considered to impact overall height loss, sleep duration (Adj. R2 = 0.181, p = 0.022) and height (Adj. R2 = 0.121, p = 0.048) were useful in univariate analyses, though they were not significant in any models that included variables other than sex. Judging from log-transformed BMI variation, heavier males and females lost more height (F(2, 31) = 4.59, Adj. R2 = 0.179, p = 0.018). Among factors anticipated to reduce height loss by acting prior to morning measurements, only time spent walking was significantly associated (β = 2.6 ± 0.8 mm, t = 3.16, p = 0.004) when included as a predictor along with sex (p = 0.17) and log-BMI (p = 0.003). This model explained about 38% of height loss variance. None of the factors considered as potentially acting between measurement sessions showed statistically significant influences when included in the model just described, though predictor coefficients were in the anticipated direction. Results suggest that self-reported activities may be an important supplement to anthropometric studies, both for planning and later evaluation, particularly in large studies.  相似文献   

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The branched structure properties of hyperbranched polysaccharides (TM3a and TM3b), extracted from sclerotia of Pleurotus tuber-regium, were studied by using laser light scattering and viscometry. The configurational shrinking factor (g) and viscometric shrinking factor (g′) of TM3a and TM3b were discussed, where curdlan and pullulan were taken as the linear references for derivation of g and g′. The dependences of g factor, g′ factor, and Flory factor (Φbranched) on weight average molecular weight (Mw) were established to be g = 1.07 × 102Mw-0.48±0.09, g′ = 3.63 × 101Mw-0.43±0.01, and Φbranched = 7.08 × 1020Mw0.39±0.1 for TM3a in 0.25 M LiCl/DMSO at 25 °C, when curdlan acted as the linear reference. A power law relationship g = 2.71 × 10?1g?0.61±0.1 for TM3a was found, and the exponent was approximately same to 0.60 established by Kurata et al. for polystyrene star molecules. The dependence of g factor on Mw for TM3b was found to be g = 1.99 × 102Mw-0.53±0.02, when pullulan was used as the linear reference. On the basis of Zimm–Stockmayer equation for tetrafunctional units, molecular weight of branching unit (M0) deduced from nonlinear curve fitting of g versus Mw was 8739 ± 564 g/mol and 3961 ± 1245 g/mol for TM3a and TM3b, respectively. The effect of different linear reference curves and polydispersity was discussed. This work gave valuable information on branched structure characterization and insights into the biosynthetic pathways of the hyperbranched polysaccharide from fungus.  相似文献   

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