An institutional experience of quality assurance of a treatment planning system on photon beam

Aim

The purpose of the present study is to show the application of the IAEA TRS-430 QA procedures of Eclipse™v7.5 TPS for photon energies. In addition, the trends of the deviations found in the conducted tests were determined.

Background

In the past, the lack of complete TPS QA procedures led to some serious accidents. So, QA in the radiotherapy treatment planning process is essential for determination of accuracy in the radiotherapy process and avoidance of treatment errors.

Materials and methods

The calculations of TPS and measurements of irradiations of the treatment device were compared in the study. As a result, the local dose deviation values (δ₁: central beam axis, δ₂: penumbra and build up region, δ₃: inside field, δ₄: outside beam edges, δ_50–90: beam fringe, RW₅₀: radiological width) and their confidence limit values (including systematic and random errors) were obtained.

Results

The confidence limit values of δ₄ were detected to increase with expanding field size. The values of δ₁ and δ₃ of hard wedge were larger than open fields. The values of δ₂ and δ_50–90 of the inhomogeneity effect test were larger, especially than other tests of this study. The average deviation was showed to increase with the rise of the wedge angle. The values of δ₃ and δ₄ of lung irradiation were outside tolerance.

Conclusions

The QA of TPS was done and it was found that there were no reservations in its use in patient treatment. The trend of the deviations is shown.     

Comparative evaluation of photoionization and flame ionization detectors for ethylene analysis

Abstract. This paper compares the use of photoionization and flame ionization detectors (PID and FID. respectively) for the analysis of ethylene in plant physiological studies. It is shown that PID has the capability to analyse ethylene levels in the order of 1 mm³ m⁻³. This represents an increase in sensitivity over FID of several-fold. Evidence is presented that this enhanced sensitivity allows for measurement of the rate of ethylene production from plants in continuous-flow systems by taking air samples directly from the air stream, thus eliminating the need for selective collection and concentration of ethylene.     

ERIC-PCR在人工混合菌体系中的检出灵敏度

提取大肠杆菌DHSα和阴沟肠杆菌(E-26R)的基因组DNA,进行ERIC-PCR,可以分别得到稳定而独特的DNA指纹图谱;模板量的变动范围从10～100ng都不会影响其图谱的稳定性;在图谱中DHSa和E-26R各自均有一条含量最大的特征带,其不易受实验环境和实验条件的干扰而发生变化。把DHSa和E-26R按比例混合,提取混合菌基因组DNA,进行ERIC-PCR,结果表明：混合菌的DNA指纹图谱为各纯菌图谱的叠加,亦具有稳定性;通过对凝胶电泳图谱中特征带的分析,可以看出：当DHSα的菌含量达到总菌量的0．5％时,可被ERIC-PCR方法清楚地检测出来。为ERIC-PCR用于土壤微生物和环境微生物的研究,特别是用于发酵工业中杂菌污染的检测与鉴定提供了一定的依据。     

浙江省热原检查用兔敏感性状况调查

目的调查浙江省热原检查用兔对细菌内毒素的敏感性情况,为提高热原检查结果的准确性和可靠性提供参考。方法对全省所有取得生产许可证单位的家兔,用国家颁发的细菌内毒素标准品,＂热原检查法＂进行检查,剂量分别为5EU/Kg和10EU/Kg,记录并比较各单位家兔的平均升温值和升温率。结果对细菌内毒素,各兔场家兔的敏感性有一定的差异。静脉注射5EU/kg,平均升温值为0.40℃～0.87℃,升温率为35%～83%;静脉注射10EU/kg,平均升温值为0.74℃～1.16℃,升温率为70%～94%。结论不同生产单位的家兔对细菌内毒素的敏感性不同,有必要对热原检查用家兔进行细菌内毒素敏感性检查。     

Body temperature measurements in the clinic; evaluation of practice in a Norwegian hospital

(1) The aim of this study was to determine the degree of agreement between the requirements of medical staff for body temperature measurements for clinical use, as defined in a previous study, and current practice in two departments in a Norwegian university hospital.

(2) The results showed that few of the highest-ranked requirements for body temperature measurements were regarded by health personnel as having been fulfilled.

(3) It will be necessary to change current practice in order to obtain agreements between these requirements and the performance of temperature measurements. This will help to improve the basis for diagnosis and treatment and provide more efficient body temperature measurement.

支原体对抗生素的体外敏感性研究

目的研究非淋菌性尿道(宫颈)炎(NGU)患者支原体对12种抗生素敏感性,指导临床治疗。方法男性标本取尿道拭子．女性标本取宫颈拭子,采用支原体培养鉴定及药敏试剂盒进行体外药敏测定。结果126株解脲支原体(Uu)对12种抗生素敏感性从高至低依次为交沙霉素、强力霉素、美满霉素、克拉霉素、四环素、阿奇霉素、罗红霉素、司帕沙星、甲砜霉素、红霉素、可乐必妥和壮观霉素。12株人型支原体(Mh)对12种抗生素敏感性从高至低依次为交沙霉素、强力霉素、美满霉素、司帕沙星、四环素、壮观霉素、可乐必妥、甲砜霉素、红霉素、阿奇霉素、克拉霉素和罗红霉素。结论支原体耐药情况相当普遍。Uu、Mh对相同抗生素具有不同的敏感性。治疗时可依据药敏结果选择用药。     

An Evaluation of Methods for the Estimation of Sensitivity and Specificity of Site-Specific Diagnostic Tests

The performance of diagnostic tests is often evaluated by estimating their sensitivity and specificity with respect to a traditionally accepted standard test regarded as a “gold standard” in making the diagnosis. Correlated samples of binary data arise in many fields of application. The fundamental unit for analysis is occasionally the site rather than the subject in site-specific studies. Statistical methods that take into account the within-subject corelation should be employed to estimate the sensitivity and the specificity of diagnostic tests since site-specific results within a subject can be highly correlated. I introduce several statistical methods for the estimation of the sensitivity and the specificity of sitespecific diagnostic tests. I apply these techniques to the data from a study involving an enzymatic diagnostic test to motivate and illustrate the estimation of the sensitivity and the specificity of periodontal diagnostic tests. I present results from a simulation study for the estimation of diagnostic sensitivity when the data are correlated within subjects. Through a simulation study, I compare the performance of the binomial estimator pCBE, the ratio estimator pCBE, the weighted estimator pCWE, the intracluster correlation estimator pCIC, and the generalized estimating equation (GEE) estimator PCGEE in terms of biases, observed variances, mean squared errors (MSE), relative efficiencies of their variances and 95 per cent coverage proportions. I recommend using PCBE when σ == 0. I recommend use of the weighted estimator PCWE when σ = 0.6. When σ == 0.2 or σ == 0.4, and the number of subjects is at least 30, PCGEE performs well.     

Sensitivity Analysis of Variable-Size Group Testing and its Related Continuous Models

Parallels between the discrete group-testing model and some closely-related continuous models are elucidated. It is shown that in both the discrete and continuous cases, the maximum likelihood estimators may suffer from similar lack of robustness. Isotonic regression and maximum likelihood estimation were therefore compared for a modified group testing model.     

Assessment and evaluation of MV image guidance system performance in radiotherapy

Background and aim

The clinical use of imaging system in image guided radiotherapy (IGRT) necessitates performing periodic quality assurance of the system to be confident in applying corrections for patient set-up errors. We aim to develop and implement a quality assurance (QA) programme for megavoltage (MV) based image guidance system and assess its long term performance for a period of 3 years.

Materials and methods

Periodic QA tests were performed for the MV planar and cone beam computed tomography (CBCT) imaging system to assess the system safety, mechanical and geometrical accuracy, image quality and dose. The tests were performed using the equipment supplied by the manufacturer along with the image guidance system and using simple methods developed in-house. The test results were compared with expected or baseline values established during commissioning.

Results

The safety system was found to be functional. The results of mechanical and geometrical tests were in good agreement with the expected results. The system mechanical positioning was stable and reproducible within ±2 mm accuracy. The image quality and the imaging dose of the planar and CBCT imaging were found to agree with the baseline values and the manufacturer specifications.

Discussion

Throughout the three-year period, all the QA tests were within the specification. The mechanical and geometrical tests are most crucial as they directly affect the patient positioning accuracy.

Conclusion

We conclude that the MV image guidance system is efficient to perform IGRT and insist to perform periodic QA tests and calibration for the system.     

Energy dependence of radiochromic dosimetry films for use in radiotherapy verification

Aim

The purpose of the study was to examine the energy dependence of Gafchromic EBT radiochromic dosimetry films, in order to assess their potential use in intensity-modulated radiotherapy (IMRT) verifications.

Materials and methods

The film samples were irradiated with doses from 0.1 to 12 Gy using photon beams from the energy range 1.25 MeV to 25 MV and the film response was measured using a flat-bed scanner. The samples were scanned and the film responses for different beam energies were compared.

Results

A high uncertainty in readout of the film response was observed for samples irradiated with doses lower than 1 Gy. The relative difference exceeds 20% for doses lower than 1 Gy while for doses over 1 Gy the measured film response differs by less than 5% for the whole examined energy range. The achieved uncertainty of the experimental procedure does not reveal any energy dependence of Gafchromic EBT film response in the investigated energy range.

Conclusions

Gafchromic EBT film does not show any energy dependence in the conditions typical for IMRT but the doses measured for pre-treatment plan verifications should exceed 1 Gy.     

Speed encoding in correlation motion detectors as a consequence of spatial structure

For animals to carry out a wide range of detection, recognition and navigation tasks, visual motion signals are crucial. The encoding of motion information has therefore, attracted much attention in the experimental and computational study of brain function. Two main alternative mechanisms have been proposed on the basis of behavioural and physiological experiments. On one hand, correlation-type and motion energy detectors are simple and efficient in the design of their basic mechanism but are tuned to temporal frequency rather than to speed. On other hand, gradient-type motion detectors directly represent an estimate of speed, but may require more demanding processing mechanisms. We demonstrate here how the temporal frequency dependence observed for sine-wave gratings can disappear for less constrained stimuli, to be replaced by responses reflecting speed for stimuli like square waves when a phase-sensitive detection mechanism is employed. We conclude from these observations that temporal frequency tuning is not necessarily a limitation for motion vision based on correlation detectors, and more generally demonstrate in view of the typical Fourier composition of natural scenes, that correlation detectors operating in such environments can encode image speed. In the context of our results, we discuss the implications of the loss of phase sensitivity inherent in using a linear system approach to describe neural processing.     

Sensitivity analysis for trend tests: application to the risk of radiation exposure

Trend tests are used to assess the relationship between multiple level treatment X and binary response R. In observational studies, however, there may be a confounder U that is associated with treatment X and causally related to response R. When the data for the confounder U are not observed, an approach for assessing the sensitivity of test results to U is provided. Its use is illustrated by examining data from a study of mutation rate after the Chernobyl accident.     

Development and Challenge of HIV/AIDS Testing Laboratory Network and Quality Assurance System in China

This paper describes the development and challenge of HIV/AIDS testing laboratory network and quality assurance system in China. At present,the HIV/AIDS testing laboratories includes three classes,the National AIDS Reference Laboratory,HIV/AIDS confirmatory laboratories and HIV/AIDS screening laboratories. All of them are accredited by the health authorities,and each class of laboratories take charge of their function strictly according to the "National Management of HIV/AIDS Detection (2006)". A complete quality assurance and quality control system for HIV/AIDS testing has been developed,which includes technical training,strict laboratory monitoring and approval,examination or proficiency testing on HIV/AIDS detection,and quality evaluation and supervision of HIV/AIDS diagnostic kits. Besides conduct the routine anti-HIV antibody test,more and more laboratories began to conduct other tests,such as CD4 T lymphocyte cell counting,HIV viral load,HIV DNA PCR,genotyping,drug resistance,and HIV-1 recent infection test. The primary challenges faced by the HIV/AIDS testing laboratory network are in the areas of laboratory management and quality control. For example,the provincial PT program is inefficient,the internal quality control is conducted perfunctorily,personnel training can not met the needs of the workplace,which need to be improved.     

Role of non-linear optics and multiple photon absorbance in enhancing sensitivity of enzyme-based chemical agent detectors

Real-time chemical sensors have been developed based on the binding of the analyte to monolayers of either porphyrin alone or porphyrins incorporated into the active site of enzymes. Binding of an analyte to porphyrin alone causes a redistribution of electrons in the porphyrin, altering the energy levels of the electrons which manifests as a change in the absorbance spectrum of the porphyrin. Porphyrins incorporated into the active site of enzymes such as cholinesterases are displaced when a competitive inhibitor such as nerve agents binds to the active site; this results in the porphyrin experiencing a different microenvironment than in the protein, resulting in a change in absorbance spectrum. Based on the Beer-Lambert relationship of concentration and absorbance, the limit of detection (LOD) for porphyrin-based sensors should be approximately 2 nM although LODs several orders of magnitude lower have been published. This increased sensitivity is explained as the result of multiple photon absorbance by the porphyrin and limiting self-quenching energy transfer reactions in the evanescent monolayer.     

Multi-institutional evaluation using the end-to-end test for implementation of dynamic techniques of radiation therapy in Thailand

AimIn this study, an accuracy survey of intensity-modulated radiation therapy (IMRT) and volumetric arc radiation therapy (VMAT) implementation in radiotherapy centers in Thailand was conducted.BackgroundIt is well recognized that there is a need for radiotherapy centers to evaluate the accuracy levels of their current practices, and use the related information to identify opportunities for future development.Materials and methodsAn end-to-end test using a CIRS thorax phantom was carried out at 8 participating centers. Based on each center's protocol for simulation and planning, linac-based IMRT or VMAT plans were generated following the IAEA (CRP E24017) guidelines. Point doses in the region of PTVs and OARs were obtained from 5 ionization chamber readings and the dose distribution from the radiochromic films. The global gamma indices of the measurement doses and the treatment planning system calculation doses were compared.ResultsThe large majority of the RT centers (6/8) fulfilled the dosimetric goals, with the measured and calculated doses at the specification points agreeing within ±3% for PTV and ±5% for OARS. At 2 centers, TPS underestimated the lung doses by about 6% and spinal cord doses by 8%. The mean percentage gamma pass rates for the 8 centers were 98.29 ± 0.67% (for the 3%/3 mm criterion) and 96.72 ± 0.84% (for the 2%/2 mm criterion).ConclusionsThe 8 participating RT centers achieved a satisfactory quality level of IMRT/VMAT clinical implementation.     

Determining Important Parameters in the Spread of Malaria Through the Sensitivity Analysis of a Mathematical Model

We perform sensitivity analyses on a mathematical model of malaria transmission to determine the relative importance of model parameters to disease transmission and prevalence. We compile two sets of baseline parameter values: one for areas of high transmission and one for low transmission. We compute sensitivity indices of the reproductive number (which measures initial disease transmission) and the endemic equilibrium point (which measures disease prevalence) to the parameters at the baseline values. We find that in areas of low transmission, the reproductive number and the equilibrium proportion of infectious humans are most sensitive to the mosquito biting rate. In areas of high transmission, the reproductive number is again most sensitive to the mosquito biting rate, but the equilibrium proportion of infectious humans is most sensitive to the human recovery rate. This suggests strategies that target the mosquito biting rate (such as the use of insecticide-treated bed nets and indoor residual spraying) and those that target the human recovery rate (such as the prompt diagnosis and treatment of infectious individuals) can be successful in controlling malaria.