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Background and Objective: Several organization such as AAPM (American Association of Physicist in Medicine), ACR (American College of Radiology), ACMP (American College of Medical Physics) and ESTRO (European Society for Therapeutic Radiology and Oncology) recommended the need for periodic quality control procedure in radiation oncology. One of the best methods for quality control is in vivo dosimetry, while radiotherapy is performed. The aim of this study was to design and optimiz a protocol for the quality control of radiation treatment of patients with head and neck malignancy. Materials and Methods: In this case series study midle line dose was measured in vivo in conjunction with portal imaging in 19 patients that were treated using a Co-60 unit, in August and December 2007. Distribution of entrance and exit dose was determined using two diodes, off axis ratios and portal imaging together with a user code written in MATLAB. User code was applied to convert optical intensity of portal film to optical density. Midline dose was calculated in one centimeter intervals using entrance and exit dose with the Huyskens algorithm method. Results: The midline dose was calculated in 165 points. The mean and standard deviation between measured and prescribed dose was about 4.27±3.61%. In 110 points (66.66%), the deviation was less than 5% (2.27±1.37), in 41 points (24.84%) the mean deviation was between 5 and 10% (6.51±1.2) and in 14 points (8.48%) mean deviation was more than 10% (13.37±2.34). The maximum and minimum deviations were found in center of the field (2.6±1.63) and 5cm away from center of the field (7.24±4.86) respectively. Maximum and minimum deviations correspond to the equivalent field of 14cm2 (5.08±3.53) and 8cm2 (2.95±2.13) respectively. Conclusion: This study showed that using a portal detector in conjunction with two diodes is a simple and accurate method for daily quality control in radiotherapy. The data is acquired in this way can be used for evaluating the accuracy of treatment steps including determination of output of a treatment machine, quality control of a treatment planning system and precision of calculations and patient setup.

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Background and Objective: Irreversible electroporation is a new treatment modality for skin tumors ablation. In order to successful treatment, all of tumoral tissues must be exposed to intense electric field. In addition, the heat that produced during the surgery has adverse effect on recovery procedure. This study was done to evaluate the thermal distribution in ablation of squamous cell carcinoma skin tumors using irreversible electroporation. Materials and Methods: In this study numerical modeling by finite element was used for determination of electrical and thermal distribution in healthy and tumoral tissues. Three-Dimensional Model was done using MR imaging of patient with squamous cell carcinoma in FEMLAB v3.5a software. Electric field distribution determined using Laplace equation and distribution of thermal damage calculated using bioheat equation and Arrhenius equation. This calculation was done for different geometry parameters of needle and plate electrodes. Results: Thermal damage of first-degree burn was not observed in any cases. However in high voltage, volume with temperature above 43˚C reach to 10% of tumoral tissue and 3% of healthy tissue. The study show that the voltage applied to the electrodes and the distance between the electrodes can have the greatest impact on the thermal and electrical distributions. Although needle electrode showed better electric coverage in tumoral area. Conclusion: This study showed that it can be possible to select optimized electric and geometric parameter to select electrode for complete tumor ablation, control of thermal damage in tumoral and healthy tissues.