Background: In intensity modulated radiation therapy, cone beam computed tomography (CT) has been used to evaluate patients prior to treatment. This study conducted a comparative evaluation of the image reconstruction ability of the clinically used half-fan Bowtie filter and the full-fan Bowtie filter. Materals and Methods: A CT simulation marker was inserted inside a human phantom, and the pelvic region, a large field-of-view region, was scanned by moving the isocenter along the x-axis ± 1– 5 cm with the full-fan mode. Furthermore, image verification was conducted based on the planning CT image and bone to confirm the setup correction value. The obtained value was then compared with that from the clinically used half-fan scan. Results: The evaluation of the reconstructed image (from the isocenter to the marker) after setting the median line did not show a significant difference with respect to the image obtained using the half-fan scan. Planning CT images and setup errors were compared in three directions, and the results showed that each mean value was within the margin of error (± 3 mm). The 3D vector value was determined to be within 0– 2. 45 mm, and the comparison of the value obtained from the half-fan scan showed no statistically significant result. Conclusion: The application of a phantom study to actual patients in the future will reduce the error caused by movement during the treatment due to the short scan time and will reduce the imaging dose for patients during setup error confirmation and correction.

Background: In CT systems, the machine u lizes a bow e filter to shape the X-ray beam and remove lower energy photons. The shape of this bow e filter is complicated and its geometry is o! en not available in detail. These renders the CT dose index (CTDI) to have different values in measurement versus Monte Carlo simula on studies and other analy cal calcula ons especially in dosimetry of internal organs. In exis ng literature, the bow e filter shape is extracted by using expensive sensors Materials and Methods: In the present work, the shape of the bow e filter of the Biograph 6 PET/CT was derived by using Thermolumenecence dosimeters (TLDs). Subsequently, to evaluate the accuracy of the body bow e filter shape as generated by TLDs, Monte Carlo simula on of CT was performed. 16 X-ray sources in various angles were used within the Monte Carlo code (MCNP-4C) to simulate the CT sec on of the PET-CT Biograph 6 system and to calculate dose. Results: The rela ve difference between simulated and measured CTDI value for the PET/CT Siemens Biograph 6 at 80, 110 and 130 kVp were 4. 2, 2. 9 and 2. 3%, respec vely. Conclusion: In this study, we demonstrate that it is possible to calculate the bow e filter shape by using an inexpensive TLD method. The results showed that it is possible to determine the shape of the bow e filter in PET/CT using TLDs with acceptable accuracy.

Background: Computed tomography (CT) scans have become an essential diagnostic tool, but they carry significant risks due to the exposure of patients to ionizing radiation. Therefore, healthcare professionals have a responsibility to optimize radiation dose and image quality simultaneously. One factor that significantly affects the quality of images and radiation dose is the Bowtie filter used in CT systems, which homogenizes and shapes the X-ray spectrum. However, its characteristic shape, specific to each manufacturer makes it impossible to model it from only the information in the technical note alone. Materials and Methods: This study presents a novel methodology using optically stimulated luminescence (OSLD) nanodots to determine the body Bowtie filter shape in a Siemens SOMATOM EMOTION 16-slice CT. The accuracy of the body Bowtie filter shape generated by OSLD was validated by performing Monte Carlo simulations of CT scans. Results: The difference between simulated and measured CTDIw values for the PET/CT Siemens at 80, 110 and 130 kVp were 4. 02%, 7. 74%, and 4. 81%, respectively. Conclusion: In this work, it has been demonstrated that the use of OSLD nanodots allows for the determination of the shape of Bowtie filters in CT scans with acceptable accuracy. This work has the potential to address a significant gap in the modeling of Bowtie filters, which could significantly improve the optimization of radiation dose and image quality in CT scans.

Background: Using cone-beam computed tomography (CBCT) in radiotherapy, the thorax or pelvis, which are both large areas, can be scanned by rotating the gantry 360° using a half-fan (HF) Bowtie filter (BF). The HF mode has a longer scan time than that of the full-fan (FF) mode, thus exposing the patient to an increased imaging dose. Materials and Methods: To determine the applicability of FF to anatomically large areas, positioning error values and absorbed dose of organs at risk (OARs) were measured when HF and FF were employed in 22 patients who underwent pelvic intensity-modulated radiation therapy. Results: In a clinical experiment applying FFBF scan mode to anatomically large areas of a patient’s body during CBCT, the positioning error values were measured for all target areas within the mean ± 3 mm in all three directions. The scanning time in the FF scan mode was reduced by 20 s, while the absorption dose was reduced by 7–52 times in the OARs. Conclusion: The appropriate application of FF for treating large-size targets can reduce the CBCT scanning time, which, in turn, would markedly decrease the radiation exposure in patients by reducing random errors during procedures.

In this research, we studied isolation of the cellulolitic fungi from the persimmon tree, grapevine, pomegranate tree and walnut soils. Among of them, persimmon soil was selected because of maximum cellulolitic fungi. Seven fungi werw isolated from persimmon soil, which three of them had suitable cellulose activity and they were identificated by 18S rRNA and named: Aspergillus niger MZM 89-a2, Penicillium decumbens ZHE 89-p3, Penicillium decumbens MMH 89-p1. Cellulase activities of these fungi were respectively (U/d): FPA 3.1671, 3.5740, 3.1812 and Avicelase 1.6605, 0.3869, 1.1451 and CMCase 2.950, 0.2644, 0.4604. Response surface activity (RSM) was studied to evaluate the effects of temperature, moisture content and particle size for FPA by Aspergillus niger MZM 89-a2. The optimum FPA was in temperature, moisture content and particle size respectively: 28.49oC, 66.62٪ and 1.5-2 (mm). The maximum predicted FPA was 4.35 (U/g) and obtained FPA under this condition was 4.42 (U/g), which indicates the efficacy of the model for prediction of FPA activity under different conditions of the medium.