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Introduction: In this study, Radiomic features analysis of CT scan images of the irradiated breast compared to the contralateral breast after a 12 Gy boost radiation dose in IOERT was conducted to obtain radiation-sensitive indicators (parameters) biological markers or biological dosimeters.Material and Methods: 35 contrast chest CT scans (with unilateral ductal carcinoma in situ (DCIS) who had undergone boost IOERT) were used in this study. The total number of 259 CT radiomic features (first-order, textural, gradient, and autoregressive model-based features) were extracted using Mazda software. The features that were significantly different in the two breasts were selected. A score was assigned to each of the features and the highest scores were characterized (according to the level of significant differences). The feature selection process was performed using the hybrid feature selection method.Results: CT Texture analysis indicated that radiation dose causes significant changes in some radiomic features of the breast tissue. Conclusion: With more research in the future, we can fit the Delta-Radiomics values with the received radiation dose and achieve a biological dosimeter to detect low-dose radiation.

Introduction: Environmental and occupational human exposure from neutron source can lead to the serious biologic effects. The aim of this study is to evaluate the cancer incidence risk for various human organs at different neutron dose levels due to exposure from an Americium-241/Beryllium (Am-241/Be), a standard neutron source for calibration purposes. Material and Methods: We measured ambient dose equivalent H*(10) at different distances from Am-241/Be mixed neutron source by Berthold LB 6411 detector and determined cancer incidence risk for different organs of both male and female subjects at different neutron exposure levels by BEIR VII model. Results: Exposure age had a reverse impact on cancer incidence risk of different organs. We found that as H*(10) increases, cancer incidence risk increments as well. Colon (for men) and bladder (for women) had the highest sensitivity to neutron exposure, while prostate and uterus showed the lowest risk of cancer incidence among male and female subjects, respectively. Conclusion: Older exposed persons are at a lower risk of cancer incidence. The risk of cancer incidence for various organs is considerably associated with gender, such that radiation sensitivity of female organs was higher at all the measured neutron dose levels.

Introduction Interaluminal brachytherapy is one of the important methods of esophageal cancer treatment. The effect of applicator attenuation is not considered in dose calculation method released by AAPM-TG43. In this study, the effect of High-Dose Rate (HDR) brachytherapy esophageal applicator on dose distribution was surveyed in HDR brachytherapy. Materials and Methods A cylindrical PMMA phantom was built in order to be inserted by various sizes of esophageal applicators. EDR2 films were placed at 33 mm from Ir-192 source and irradiated with 1.5 Gy after planning using treatment planning system for all applicators. Results The results of film dosimetry in reference point for 6, 8, 10, and 20 mm applicators were 1.54, 1.53, 1.48, and 1.50 Gy, respectively. The difference between practical and treatment planning system results was 0.023 Gy (

Introduction Dosimetric accuracy is a major issue in the quality assurance (QA) program for treatment planning systems (TPS). An important contribution to this process has been a proper dosimetry method to guarantee the accuracy of delivered dose to the tumor. In brachytherapy (BT) of gynecological (Gyn) cancer it is usual to insert a combination of tandem and ovoid applicators with a complicated geometry which makes their dosimetry verification difficult and important. Therefore, evaluation and verification of dose distribution is necessary for accurate dose delivery to the patients. Materials and Methods The solid phantom was made from Perspex slabs as a tool for intracavitary brachytherapy dosimetric QA. Film dosimetry (EDR2) was done for a combination of ovoid and tandem applicators introduced by Flexitron brachytherapy system. Treatment planning was also done with Flexiplan 3D-TPS to irradiate films sandwiched between phantom slabs. Isodose curves obtained from treatment planning system and the films were compared with each other in 2D and 3D manners. Results The brachytherapy solid phantom was constructed with slabs. It was possible to insert tandems and ovoids loaded with radioactive source of Ir-192 subsequently. Relative error was 3-8.6% and average relative error was 5.08% in comparison with the films and TPS isodose curves. Conclusion Our results showed that the difference between TPS and the measurements is well within the acceptable boundaries and below the action level according to AAPM TG.45. Our findings showed that this phantom after minor corrections can be used as a method of choice for inter-comparison analysis of TPS and to fill the existing gap for accurate QA program in intracavitary brachytherapy. The constructed phantom also showed that it can be a valuable tool for verification of accurate dose delivery to the patients as well as training for brachytherapy residents and physics students.

Introduction Bolus is a soft and resilient material which is used for increasing skin dose or to even out the irregular patient contour. The main property of various materials used presently as bolus is the water-equivalent electron density. Ethyl methacrylate is used as a soft-liner in dentistry and its physical and chemical properties are proved to be nontoxic for human body. The goal of this study was to assess the feasibility of using this material as bolus in radiotherapy and also evaluating some parameters such as mass, electron densities, and transmission factors. Materials and Methods Computed tomography data from the sample material were acquired to assess mass and electron densities with various techniques (mA and kVp). Circular ROIs were delineated on CT DICOM images and densities were calculated using CT numbers. Transmission factors were calculated for 6 and 18 MV. Results Evaluation of our results are evident that showed that mass and electron densities of ethyl methacrylate are similar to those of water and soft tissue. Furthermore, transmission factors are close to those of water. Conclusion According to the results of this study and other properties such as flexibility and harmlessness, it seems that ethyl methacrylate is a suitable material to be used as bolus in radiotherapy.