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Intensity-modulated brachytherapy for vaginal cancer
This study aimed to evaluate the dose modulation potential of static and dynamic steel-shielded applicators using the Geant4 Application for Emission Tomography (GATE) Monte Carlo code for the treatment of vaginal cancer. The GATE TOOLKIT (version 9.0) was used to simulate vaginal cancer intensity-modulated brachytherapy (IMBT) in a pelvic water-equivalent phantom. IMBT performance of a multichannel static and single-channel dynamic steel-shielded applicator was compared to that of a conventional multichannel Plexiglas applicator. DoseActors were defined to calculate the absorbed dose and attached to the voxelized target a...
Source: Radiological Physics and Technology - September 7, 2022 Category: Physics Source Type: research

Photon-specific absorbed fraction estimates in stylized ORNL and voxelized ICRP adult male phantoms using a new developed Geant4-based code “DoseCalcs”: a validation study
In this study, we present a newly developed Geant4-based code for internal dosimetry calculations, namely “DoseCalcs”. To assess the performance of the geometrical methods and computational capabilities of our developed tool, we used the GDML, TEXT, STL, and C++ methods to model the ORNL adult phantom, and a voxel-based structure to construct the ICRP adult male. SAFs in the ORNL and ICRP adult male phantoms for eight discrete mono-energetic photons with energies ranging from 0.01 to 2 MeV are calculated with DoseCalcs and compared to ORNL and OpenDose reference data. The two phantoms showed good agreement with both re...
Source: Radiological Physics and Technology - September 6, 2022 Category: Physics Source Type: research

Variability in contrast and apparent diffusion coefficient of kiwifruit used as prostate MRI phantom: 1-week validation
This study evaluated the variability in contrasts and apparent diffusion coefficients (ADCs) via repeated scans of kiwifruits for 1 week. All scans were performed using a 3T MRI system. Six kiwifruits were prepared as phantoms. Each kiwifruit was scanned consecutively for 1 week, and T2-weighted and diffusion-weighted images were acquired. Contrasts between the peripheral placenta (PP) and central placenta (CP), and between the outer pericarp (OP) and CP were calculated. The ADCs of the PP, OP, and CP were also determined. The Friedman test with Scheff é’s post hoc comparison was used to assess contrast and ADC variabil...
Source: Radiological Physics and Technology - September 5, 2022 Category: Physics Source Type: research

Assessment of organ and effective doses received by adult patients undergoing computed tomography in three hospitals in Brazzaville, Congo Republic
This study demonstrates that urgent steps should be taken to reduce doses administered to patients to optimal levels. Such optimal levels may be achieved by adopting local diagnostic reference levels, together with the implementation of dose reduction strategies. (Source: Radiological Physics and Technology)
Source: Radiological Physics and Technology - September 3, 2022 Category: Physics Source Type: research

A novel myocardial T1 analysis method robust to fluctuations in longitudinal magnetization recovery due to heart rate variability in polarity-corrected inversion time preparation
AbstractMyocardial T1 mapping is useful for characterizing the myocardial tissues. Polarity-corrected inversion time preparation (PCTIP), one of the T1 mapping techniques, was expected to reduce measurement underestimation versus the MOLLI method. However, measurement accuracy is reportedly reduced, especially at high heart rates (HR), owing to the shorter time interval of inversion recovery (IR) pulses. This phantom-based experiment aimed to evaluate the dependence of T1 mapping with PCTIP on HR. Here we proposed and evaluated the effectiveness of a novel HR-independent analysis method for T1 mapping. A PCTIP scan using a...
Source: Radiological Physics and Technology - September 1, 2022 Category: Physics Source Type: research

Accuracy of virtual non-contrast images with different algorithms in dual-energy computed tomography
AbstractWe investigated the accuracy of the computed tomography (CT) numbers of virtual non-contrast (VNC) images for two different material decomposition algorithms using the same image data for different diluted contrast agent concentrations. A container filled with contrast agents was inserted into a cylindrical phantom and scanned with dual-energy protocols (80/Sn140 kV, 100/Sn140 kV) using a dual-source CT. VNC images were generated by the 2-material decomposition (MD) algorithm using the energy of each tube voltage and the linear attenuation coefficient, calculated from the theoretical spectral curve of the agent and...
Source: Radiological Physics and Technology - September 1, 2022 Category: Physics Source Type: research

Development of a quantitative analysis method for assessing patient body surface deformation using an optical surface tracking system
This study aimed to develop a new method to quantitatively analyze body shape changes in patients during radiotherapy without additional radiation exposure using an optical surface tracking system. This method ’s accuracy was evaluated using a cubic phantom with a known shift. Surface images of three-dimensionally printed phantoms, which simulated the head and neck shapes of real patients before and after treatment, were used to create a deformation surface area histogram. The near-maximum deformation v alue covering an area of 2 cm2 in the surface image (Def-2cm2) was calculated. A volumetric modulated arc therapy (VMAT...
Source: Radiological Physics and Technology - August 30, 2022 Category: Physics Source Type: research

Utilization of upper and lower limits of exposure index in clinical digital radiography
In this study, physical image characteristics of detectors, visual detectability by charts, and observer experiments using a chest phantom were examined to determine upper (DImax) and lower (DImin) limits of the EIT and DI to achieve a reliable dose reduction in chest examinations. As the result, the tolerance ranges indicated by DImax and DImin, which were set based on the results of physical and visual evaluations, proved to be almost consistent with the distribution of EI values in 735 clinical images taken with a photo-timer control in real clinical practices. (Source: Radiological Physics and Technology)
Source: Radiological Physics and Technology - August 29, 2022 Category: Physics Source Type: research