Background: This study aims to perform quality control (QC) practices for Setup reproducibility during radiotherapy for nasopharyngeal carcinoma (NPC) using statistical process control (SPC) tools. Materials and Methods: A total of 480 fractional images from 48 NPC patients with the first 10 fractions of the treatment were collected. In QC practices, Setup errors were described using the histogram and normal curve, cumulative frequencies of absolute Setup errors and 3D Euclidean Distance (Eu) were analyzed,the X ̅,-S chart and process capability index (Cpk) with the variable Eu were utilized to identify whether the outlier occurred and to evaluate the QC process. Results: The translational Setup error distributions were almost normal in Lateral, Longitudinal and Vertical directions and were narrower in Lateral and Vertical directions. Vertical translational errors and Eu with a larger magnitude sag appeared the most frequently. Between the couch sag and no sag, the Eu mean of 7 to 7 NPC patients with the same 3 patients was out of control and the standard deviation of Eu of nil to 2 patients was outlier based on the X ̅,-S chart, and the Cpk was 1. 05 and 1. 36 respectively, when the specification limit of translational errors was ±, 3 mm. Conclusion: Daily imaging is necessary to increase Setup reproducibility for NPC patients and more measures should be taken to facilitate quality assurance procedures. SPC is better applied to QC practices depending on the reliable data and the acceptable tolerance levels in further studies.

In this paper, we consider the estimation of the stress-strength reliability of a coherent system. The distributions of stress and strength random variables are the members of a general class of distributions. For a series-parallel system, the reliability of the stress-strength model is estimated using the maximum likelihood estimation, asymptotic confidence interval, uniformly minimum variance unbiased estimation, and Bayes estimation. Also, simulation studies are performed, and two real data sets are analyzed.

Introduction: Radiation therapy involves a multistep procedure; therefore, the error in patient set up is an inherent part of the treatment. Main purpose of this study was to determine the clinical target volume (CTV) to planning target volume (PTV) in head and neck cancer patients. Material and Methods: A total of 15 patients who had daily portal images during the treatment courses were randomly selected in the present study. Systematic (Σ ) and random (σ ) errors were evaluated in three directions. The Isogray treatment planning system and Elekta linear accelerator were used in this study. Moreover, we had used MOSIAQ software as a record and Verify system. Setup margins were calculated using three published margin recipes, including the International Commission on Radiation Units and Measurements (ICRU) report 62, as well as Stroom’ s and van Herk’ s formulae. Results: Average magnitude of the translational errors was reported between 0. 7 and 10 mm. The systematic and random errors for head and neck cancer patients were 3. 55 (2. 58-4. 52) and 1. 83 (1. 56-2. 10) mm, respectively. According to the ICRU report 62, as well as Stoorm’ s and van Herk’ s formulas, the required margins to cover the target were obtained within the ranges of 3. 1-4. 9, 6. 4-10. 5, and 7. 7-12. 7 mm, respectively. Conclusion: According to the results of the present study, 6. 5-10. 5 mm extension in CTV to PTV margin can ensure that 90% of the head and neck cancer patients will receive a minimum cumulative CTV dose higher than or equal to 95% of the prescribed dose.

Background: The assessment of dietary intake in epidemiological studies is often by means of validated food frequency questionnaires because of ease of administration and low burden on the subject.Method: Study Participants were chosen from five major cities of Iran and 156 subjects, aged 20-69 years old, from both gender were recruited for the study.For validation study, dietary intake was assessed by a semi-quantitative FFQ, which consisted of 160 Iranian food items. Participants were asked to complete two FFQs (at the first and fourth month of the study) and 3- day food records every month. Two blood and 24-h urine samples were collected at fifth and sixth months for comparison serum and urine concentrations of biomarkers with nutrient intakes estimated by the FFQ.Results: Forty nine persons (32.1 percent) of the subjects were men and 104 persons (67.9 percent) were women The highest correlation coefficient in all FFQs was for fiber (r=0.677; p<0.001) and the lowest one was for fat (r=0.331; p=0.001).The highest correlation coefficient was for potassium Conclusion: The results showed reasonable validity just for carbohydrate intake evaluation and good reproducibility of the FFQ over a 6- month period.