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OBJECTIVE This study aims to contribute to the literature the broadened demonstration of energy-related and field size-related responses of three different cylindrical ionization chambers, commonly used for clinical applications of the therapeutic photon beams, using GEANT4 code. METHODS GEANT4 simulation of Varian TrueBeam STx was compared with the real-time measurements. The variations in the output factor (OF) measurements depending on field sizes ranging from 0.6×0.6 cm2 to 30×30 cm2 and photon energies of 6MV, 6MV-FFF, 10MV, 10MV-FFF, and 15MV were recorded for each chamber and compared with the GEANT4 simulations. Response of the chambers was analyzed depending on those OFs. RESULTS The GEANT4 simulation model was validated. All the chambers were in a good agreement within 1.5% for field sizes between 4×4 cm2 and 30×30 cm2. The farmer chamber presented a major deviation up to 22% for the field sizes smaller than 4×4 cm2. Semiflex and pinpoint chambers have an agreement within 2% and 5.5% for 3×3cm2 and 2×2 cm2, respectively. CONCLUSION The chambers evaluated in this study can be used reliably for all photon energies and field sizes between 4×4 cm2 and 30×30 cm2. To obtain accurate measurements for field sizes smaller than 3×3 cm2, it is recommended to use detectors with a smaller sensitive volume instead of the detectors used in this study. [ABSTRACT FROM AUTHOR]

Purpose: It's postulated that hybrid techniques (HT) with lower weighting of IMRT/VMAT component would improve lung dose-volume parameters despite some disadvantage in PTV homogeneity index (HI) and target coverage (TC). Material and Methods: Conformal plans were prepared using 6-10-15 MV-X photon energies while IMRT/VMAT plans of HTs were prepared using 6MV-X. Four HTs were developed having two different ratios (10% and 50%) of IMRT/VMAT component (h-IMRT1, h-IMRT2 and h-VMAT1, h-VMAT2, respectively). HTs were compared with 3D-CRT in terms of HI and TC for PTV, and total lung (TL) and contralateral lung (CL) V5Gy, V10Gy, V20Gy and mean lung dose (MLD). Results: All HTs were advantageous for HI and TC, while disadvantageous for TL and CL-V5Gy. H-IMRT2 provided better TC than h-IMRT1, and so did h-VMAT2 compared to h-VMAT1. Lower weighting of IMRT/VMAT decreased TL and CL-V5Gy in HTs. In addition, h-IMRT1 decreased TL and CL-MLD and CLV20Gy compared to h-IMRT2, while h-VMAT2 decreased TL-V20Gy and CL-MLD compared to h-VMAT2. Conclusion: In the RT of lung tumors close to vertebra, it may be appropriate to suggest a ratio of IMRT/VMAT component approximately 10% in order to decrease the low and intermediate dose-wash lung volume, if HI and TC values are acceptable. [ABSTRACT FROM AUTHOR]

Radiation is important in dental science as it is used in both diagnostic and also in treatment issues. The teeth are every single day exposed to a significant amount of wear due to remaining hard particles from food and tooth brushing or even due to the contact with the other teeth. Dental restorations are widely used to correct the damage caused by this wear. In this study, it is aimed to determine the radiation shielding properties of the dosimetric materials which are namely hydroxyapatite (HAP) and urethane di(meth)acrylates (UDMAs). The linear attenuation coefficients of dosimetric materials were calculated using GAMOS (Geant4-based Architecture for Medicine-Oriented Simulations) Monte Carlo simulation code. The obtained results were also compared with the calculation done using XCOM. The mean free path (mfp), half value length (HVL), and tenth value length (TVL) have also been obtained. The highest LAC value was obtained for S2 sample for 511, 662, 835, 1173, 1275, and 1332 keV energies (0.170, 0.149, 0.133, 0.112, 0.108, and 0.105 cm−1, respectively) and the lowest LAC values were obtained for S3 sample for 511, 662, 835, 1173, 1275, and 1332 keV gamma energies (0.102, 0.091, 0.082, 0.069, 0.066, and 0.065 cm−1, respectively). [ABSTRACT FROM AUTHOR]

Copyright of Dokuz Eylul University Muhendislik Faculty of Engineering Journal of Science & Engineering / Dokuz Eylül Üniversitesi Mühendislik Fakültesi Fen ve Mühendislik Dergisi is the property of Dokuz Eylul Universitesi Muhendislik Fakultesi Fen ve Muhendislik Dergisi and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Turkish Journal of Oncology / Türk Onkoloji Dergisi is the property of KARE Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Turkish Journal of Oncology / Türk Onkoloji Dergisi is the property of KARE Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Purpose: Size-specific dose estimates (SSDEs) are the latest focus of interest among medical physicists studying radiation dose to the patient in computed tomography (CT). This study aims to make conversions from CTDIvol to SSDE and investigate the relationship between mean SSDE (SSDE) and central SSDE (SSDEcenter) values for pediatric patients of different age groups undergoing chest, abdomen, and pelvis scans.Methods: In this retrospective study, we examined 105 consecutive pediatric CT exams of chest, abdomen, and pelvis (CAP) classified in 3 separate groups according to age: 0-5 years, 6-10 years, and 11-16 years. A MATLAB program was developed to determine SSDE values for each patient along 6 subregions: chest, abdomen, pelvis, chest and abdomen, abdomen and pelvis, and CAP. SSDE values derived over the slice at the center of each scan range (SSDEcenter) were also recorded. SSDE and corresponding SSDEcenter results were compared for each age group.Results: Root mean square differences (RMSD) between SSDE and SSDEcenter values ranged between 0.13 mGy and 2.1 mGy through all groups and subregions, corresponding to 1.2% and 11%, respectively.Conclusion: In pediatric CT exams involving CAP region, CTDIvol and the water equivalent diameter at the middle of the scan range can be used to provide a reasonable estimate of mean SSDE with an RMSD of 11% at most. [ABSTRACT FROM AUTHOR]

Copyright of Molecular Imaging & Radionuclide Therapy is the property of Galenos Yayinevi Tic. LTD. STI and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)