电子束输出剂量随射野大小变化规律的探讨

目的 探讨电子柬射野面积对其输出剂量的影响.方法 利用Matrixx平面探测器对西门子Primus直线加速器不同能量、不同电子束限光筒、不同面积射野的输出剂量进行测量,得出数据后用Matlab软件绘制变化规律曲线,并拟合出数学公式.结果 当挡块所形成射野大于6cm×6cm时,其输出剂量与10cm×10cm野相比小于3%.而挡块所形成的方野在2cm×2cm-5cm×5cm之间时,输出量随射野大小变化显著变化,最高可达30%.结论 各种不同能量电子束的输出因子与挡块所形成的方野边长的关系可满足拟合公式:y=a k1·emx k2·e-mx.     

光野与X线照射野检测尺的设计与应用

光野与X线照射野一致性检测尺是一种射线的照射野检测装置,包括传感器单元、处理单元、显示单元。其原理是采用线阵X线传感器检测,经单片机处理后由对称线阵LED发光组件显示的方法进行测量。检测装置可实时检测与显示提高了检测效率,且提高了检测的准确性。     

电子束全身皮肤照射剂量测定和分析

目的 对电子束全身皮肤照射进行剂量学参数的测量。方法 在Varian23EX加速器上采用双机架六野照射技术,使用平行板电离室、胶片、热释光元件等对源皮距400cm处6MeV电子束的剂量学参数进行测量。结果 治疗平面的剂量场均匀性到达±5%。单照射野体表剂量80%以上,最大深度0.6cm,80%和50%剂量深度分别为1.10cm和1.42cm。双机架六野最大剂量深度接近皮肤表面,80%和50%剂量深度分别为0.40cm和1.00cm处。X射线污染为2.2%。累积因子平均值3.05。结论 全身电子束照射条件下电子束剂量特性与常规条件下特性有很大不同,必须通过实际测量来为临床照射提供依据。     

鼻咽癌颈部前后切线野的半束照射

<正>颈部淋巴结照射对于提高鼻咽癌的疗效及减少局部复发率有着十分重要的意义,但如何设野照射,却一直是放疗专家讨论较多的地方,目前国内多数单位只用前切线野照射,而不用后切线野[1],虽然摆位方便,但却造成颈深上淋     

楔形因子对照射野大小和射线深度的影响分析

目的照射野大小和测量深度不同,将导致楔形因子发生改变,继而使楔形照射野下的剂量计算发生偏差。方法利用德国WELLHOFER公司DOSE-1剂量仪和FC65-G指型电离室、水模(40 cm×40 cm×30 cm)分别测量6MV条件下不同深度、不同面积的平野和楔形野的剂量率,计算其楔形因子。结果深度对楔形因子的影响较明显,随着测量深度的增加楔形因子也增加,楔形板角度越大,深度对楔形因子的影响越明显,从1.5cm到10cm时楔形因子最大有2.5%的偏差。照射野大小对楔形因子也有一定的影响,随着照射野的增加,楔形因子也增加,只是程度有所不同。射野较小而深度较浅时,实测的楔形因子比标准值要小,射野较大且深度较深时,实测的楔形因子比标准值要大。结论用传统方法计算楔形野剂量存在误差,根据质量控制要求,楔形因子的精确度不能超过2%,为保证剂量计算的准确,消除计算误差,应测量并使用不同楔形野的楔形因子,同时对楔形因子做深度修正,采用相对深度的楔形因子,以达到放射治疗质量保证和质量控制规定的标准。     

放射治疗照射野验证方法的初步研究

放射治疗照射野的验证对于肿瘤治疗至关重要.错误的照射野形状和照射位置可能使肿瘤漏照射以及正常器官的误照.作者根据本单位的具体情况,比较5种验证放射治疗照射野的方法,总结各个方法的优缺点,以供临床应用时选择最优化的方法.     

数字摄影有效照射野控制与影像切割

目的:应用DR图像切割技术,探讨降低患者吸收剂量、节省存储空间、提高影像质量的途径。方法:选用不同大小的FPD照射野进行曝光,对诊断区外的影像切割后进行存储,在患者剂量、存储空间、影像质量等方面比较其与最大射野时的差异。结果:FPD受照面积分别为8×10英寸、10×12英寸、14×17英寸时,对应的与射野等大的存储文件大小分别为3.96MB、8.58MB、15MB,切割后存储文件最小分别可达2.1MB、5.2MB、7.5MB;与板等大照射野吸收剂量分别是2.16 dGy、10.61 dGy、2.78 dGy,与诊断区等大照射野吸收剂量分别为1.64 dGy、6.71 dGy、1.61 dGy。结论:在应用DR进行摄影时,缩小照射野至诊断区大小,并对图像进行切割,可以降低患者吸收剂量,节省存储空间,并提高影像质量。     

探讨旋转阳极在照射野面短轴方向的线量分布

目的探讨旋转阳极在照射野面的短轴方向的线量分布。方法将14×17inch的胶片置于摄影床上,以照射野的中心点为中心,利用三角函数分别计算出数个中心线外倾角所对应的短轴两侧的距离,采用相同的曝光条件,在旋转阳极为高、低两种转速的机器上,进行曝光,冲洗并采用密度计测量。结果高、低两种转速的旋转阳极X线机,在照射野面的短轴方向,比较对称点密度值,外侧缘大于内侧缘,峰值在中心点偏外侧缘。结论在旋转阳极照射野面的短轴方向,X线照射量的分布发生偏离,最大线量位于中心点偏外侧缘。     

医用电子直线加速器照射野的日常质量保证

目的通过分析照射野特性相关参数的日检数据的变化趋势．探讨医用电子直线加速器照射野的日常质量保证方法的可行性和必要性。方法每天放射治疗前．用二维电离室矩阵Daily QA3测量加速器照射野特性相关参数与预设标定值的偏差．辅以IBA公司的剂量仪DOSl进行绝对剂量验证和用慢感光胶片进行光野一致性的二次验证．并对以上各项日常检测数据（2009年11月28日-2011年4月8日）进行回顾性分析。结果X线和电子线输出剂量均随着时间的增加逐渐增大．光野一致性、射野平坦度及对称性基本保持不变。结论一年多的实践表明．本文论述的照射野日常质量保证方法是有效和可行的．它在保证每日放疗精确执行的同时,也为加速器的长期校准提供了依据。     

浅议全中枢神经系统放疗照射野的设置及技术要点

目的 探讨髓母细胞瘤及分化差的室管膜细胞瘤的全中枢系统照射时照射野的设置及技术要点。方法 患者取俯卧位,利用大小合适的真空负压垫固定患者体位,头部垫船型枕,用面罩固定。通过CT模拟定位定全颅野和全脊髓野。采用X线全脑照射和电子线全脊髓照射。结果 用此种方法在全脑和脊髓内得到比较理想的剂量分布,用电子线照射脊髓可以根据患者脊髓深度选择适当能量的电子线来满足脊髓所需剂量,而脊髓前方的正常组织所受剂量相对较少,患者的放射反应较轻,初步临床观察结果满意。结论 X线全脑及电子线全脊髓照射是目前综合治疗髓母细胞瘤及分化差室管膜细胞瘤的的主要方法之一,而放疗摆位及照射技术应予重视。     

Variety of factors to determine potential nursing home market

As the nation ages, how will hospitals and other providers determine how to care for a growing patient population--those requiring nursing home beds? In the following article, the authors discuss nursing home demand projection methodologies that could be useful for administrators who want to pursue this patient population as a market area. The plausible solution, they note, is a composite approach that focuses on historical trends and both clinical and referral sources.     

Using the theory of planned behavior to determine factors influencing processed foods consumption behavior

BACKGROUND/OBJECTIVES

The purpose of this study is to identify how level of information affected intention, using the Theory of Planned Behavior.

SUBJECTS/METHODS

The study was conducted survey in diverse community centers and shopping malls in Seoul, which yielded N = 209 datasets. To compare processed foods consumption behavior, we divided samples into two groups based on level of information about food additives (whether respondents felt that information on food additives was sufficient or not). We analyzed differences in attitudes toward food additives and toward purchasing processed foods, subjective norms, perceived behavioral control, and behavioral intentions to processed foods between sufficient information group and lack information group.

RESULTS

The results confirmed that more than 78% of respondents thought information on food additives was insufficient. However, the group who felt information was sufficient had more positive attitudes about consuming processed foods and behavioral intentions than the group who thought information was inadequate. This study found people who consider that they have sufficient information on food additives tend to have more positive attitudes toward processed foods and intention to consume processed foods.

CONCLUSIONS

This study suggests increasing needs for nutrition education on the appropriate use of processed foods. Designing useful nutrition education requires a good understanding of factors which influence on processed foods consumption.     

Population survey to determine risk factors for Mycobacterium leprae transmission and infection

BACKGROUND: Not every leprosy patient is equally effective in transmitting Mycobacterium leprae. We studied the spatial distribution of infection (using seropositivity as a marker) in the population to identify which disease characteristics of leprosy patients are important in transmission. METHODS: Clinical data and blood samples for anti-M. leprae ELISA were collected during a cross-sectional survey on five Indonesian islands highly endemic for leprosy. A geographic information system (GIS) was used to define contacts of patients. We investigated spatial clustering of patients and seropositive people and used logistic regression to determine risk factors for seropositivity. RESULTS: Of the 3986 people examined for leprosy, 3271 gave blood. Seroprevalence varied between islands (1.7-8.7%) and correlated significantly with leprosy prevalence. Five clusters of patients and two clusters of seropositives were detected. In multivariate analysis, seropositivity significantly differed by leprosy status, age, sex, and island. Serological status of patients appeared to be the best discriminator of contact groups with higher seroprevalence: contacts of seropositive patients had an adjusted odds ratio (aOR) of 1.75 (95% CI 0.922-3.31). This increased seroprevalence was strongest for contact groups living < or =75 m of two seropositive patients (aOR = 3.07; 95% CI 1.74-5.42). CONCLUSIONS: In this highly endemic area for leprosy, not only household contacts of seropositive patients, but also people living in the vicinity of a seropositive patient were more likely to harbour antibodies against M. leprae. Through measuring the serological status of patients and using a broader definition of contacts, higher risk groups can be more specifically identified.     

A literature review to identify factors that determine policies for influenza vaccination

ObjectivesTo conduct a literature review of influenza vaccination policy, describing roles and interactions between stakeholders and the factors influencing policy-making.MethodsMajor databases were searched using keywords related to influenza vaccination, decision-making and healthpolicy. Titles and abstracts were screened according to defined criteria using independent reviewers. Selected articles were analysed and compared against a checklist.Results342 papers were identified, but only 111 included. A wide range of countries was represented in articles published in 1994–2012. We identified numerous stakeholders at the national and international level and found a variety of interactions between them. Using these data, we suggest a scheme for the most important stakeholders and their interactions. Determinants of policy-making were mainly related to the vaccine/disease, political-economic context, and stakeholders communication. The most relevant evidence was clinical/epidemiological studies. After the 2009 pandemic: the importance of mathematical modelling and ethical issues was greater; and the need for better communication between stakeholders was emphasised.ConclusionsThe relevance of evidence and factors influencing policy-making varied between countries, according to complex interactions between the stakeholders involved at different levels of decision-making process. These interactions remain unclear, especially at national level, where the most important influenza policy decisions are made. To better define and understand the exact interactions and use of evidence, we recommend undertaking future qualitative studies at national level using small number of countries.     

How to determine life expectancy change of air pollution mortality: a time series study

Background  

Information on life expectancy (LE) change is of great concern for policy makers, as evidenced by discussions of the "harvesting" (or "mortality displacement") issue, i.e. how large an LE loss corresponds to the mortality results of time series (TS) studies. Whereas loss of LE attributable to chronic air pollution exposure can be determined from cohort studies, using life table methods, conventional TS studies have identified only deaths due to acute exposure, during the immediate past (typically the preceding one to five days), and they provide no information about the LE loss per death.     

Use of the regression analysis technique to determine the true phosphorus digestibility and the endogenous phosphorus output associated with corn in growing pigs

The objectives of this study were to determine true phosphorus (P) digestibility and the endogenous P output associated with corn for growing pigs using the regression analysis technique. Four barrows, average initial body weight of 25 kg, were fitted with a T-cannula and fed four diets according to a 4 x 4 Latin square design. Four cornstarch-based diets, containing four levels of P at 0.7, 1.5, 2.2 and 2.8 g/kg dry matter intake (DMI), were formulated from corn. Each experimental period comprised 8 d with 4-d adaptation and 4-d collection of ileal digesta and fecal samples. The apparent ileal and fecal P digestibility values in corn were affected (P < 0.05) by P contents in the assay diets. The apparent ileal and fecal P digestibility values increased from -51.0 to 33.3% and from -41.4 to 39.1%, respectively, as P content increased from 0.7 to 2.8 g/kg DMI. Linear relationships (P < 0.05), expressed as g/kg DMI, between the apparent ileal and fecal digestible P and the total intake of dietary P, suggested that true P digestibility and the endogenous P outputs associated with corn can be determined by the regression analysis technique. There were no differences (P > 0.05) in true P digestibility values (54.0 +/- 6.5 vs. 59.8 +/- 8.5%) and the endogenous P outputs (0.693 +/- 0.128 vs. 0.670 +/- 0.160 g/kg DMI) between the ileal and the fecal determinations. The endogenous fecal P output represented 12.3% and 25.8% of the daily total and available P requirements in growing pigs recommended by the National Research Council in 1998. The present literature data of apparent digestibility and availability underestimate the true digestive utilization of P in corn for growing pigs by approximately 35%. Current diet formulation on the bases of total, apparent P digestibility and availability values in corn inevitably leads to P overfeeding and excessive P excretion in pigs.