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Development and practical evaluation of a saturation effect learning simulator for inflow magnetic resonance angiography
AbstractThe quality of visualization in inflow magnetic resonance angiography (MRA) depends highly on the excitation state of the longitudinal magnetization obtained using specified imaging parameters. In addition, signal intensity changes controlled by the preparation pulse —such as inversion recovery (IR) and saturation recovery (SR)—can potentially be used as quantitative physiological values. Although having practitioners understand these relationships both qualitatively and quantitatively is important, handling clinical equipment in practical learning or experi ments involves limited opportunities. The simulator c...
Source: Radiological Physics and Technology - August 25, 2022 Category: Physics Source Type: research

Development of a computer-aided quality assurance support system for identifying hand X-ray image direction using deep convolutional neural network
This study developed a method to identify hand image direction, which is an elementary technology of a computer-aided quality assurance support system. In total, 14,236 hand X-ray images were used to classify hand directions (upward, downward, rightward, and leftward) commonly evaluated in clinical settings. The accuracy of the conventional classification method using original images, classification method with histogram equation images, and a novel classification method using binarization images for background removal via U-Net segmentation was evaluated. The following classification accuracy rates were achieved: 89.20% i...
Source: Radiological Physics and Technology - August 24, 2022 Category: Physics Source Type: research

Classifying presence or absence of calcifications on mammography using generative contribution mapping
In conclusion, GCM could accurately classify the presence or absence of calcific ations on mammograms and explain intuitively reasonable grounds for their classification with visualization maps highlighting regions of interest. (Source: Radiological Physics and Technology)
Source: Radiological Physics and Technology - August 21, 2022 Category: Physics Source Type: research

Reproducibility of functional connectivity metrics estimated from resting-state functional MRI with differences in days, coils, and global signal regression
This study examined the reproducibility of functional connectivity (FC) metrics estimated from rs-fMRI data acquired using scanner receiver coils with different numbers of channels. This study involved 80 rs-fMRI datasets from 20 healthy volunteers scanned in two independent imaging sessions using both 12- and 32-channel coils for each session. We used independent component analysis (ICA) to evaluate the FC of canonical resting-state networks (RSNs) and graph theory to calculate several whole-brain network metrics. The effect of global signal regression (GSR) as a preprocessing step was also considered. Comparisons within ...
Source: Radiological Physics and Technology - August 12, 2022 Category: Physics Source Type: research

Experimental determination of the effective point of measurement for cylindrical ionization chambers in megavoltage photon beams
The objective of this study was to experimentally evaluate the EPOM shifts in photon beams for cylindrical ionization chambers, which are widely used in clinical practice, and thus determine the appropriate EPOM shift. A microdiamond detector, which is a semiconductor detector with a small sensitive volume, was used as a reference detector, and the EPOM shifts of 11 types of cylindrical ionization chambers were evaluated at 6  MV and 10 MV. The depth shift from the percent depth dose (PDD) of the reference detector to that of the evaluated chamber was calculated using the least-squares method and was defined as the EPOM ...
Source: Radiological Physics and Technology - August 6, 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 - August 4, 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 - August 2, 2022 Category: Physics Source Type: research

Compton imaging for medical applications
AbstractCompton imaging exploits inelastic scattering, known as Compton scattering, using a Compton camera consisting of a scatterer detector in the front layer and an absorber detector in the back layer. This method was developed for astronomy, and in recent years, research and development for environmental and medical applications has been actively conducted. Compton imaging can discriminate gamma rays over a wide energy range from several hundred keV to several MeV. Therefore, it is expected to be applied to the simultaneous imaging of multiple nuclides in nuclear medicine and prompt gamma ray imaging for range verifica...
Source: Radiological Physics and Technology - July 22, 2022 Category: Physics Source Type: research

Practical dosimetry procedure of air kerma for kilovoltage X-ray imaging in radiation oncology using a 0.6-cc cylindrical ionization chamber with a cobalt absorbed dose-to-water calibration coefficient
In this study, we implemented a practical dosimetry procedure of air kerma for kilovoltage X-ray beams using a 0.6-cc cylindrical ionization chamber, and validated the procedure with the accuracy of the measurements using the 0.6-cc chamber compared to the measurements using a 6-cc chamber and a semiconductor device. In addition, the kerma area products (KAPs) were compared with the dose reference levels of radiology. A modified air kerma formalism using a 0.6-cc cylindrical ionization chamber air kerma formalism with a cobalt absorbed dose-to-water calibration coefficient was implemented. Validation of the formalism showe...
Source: Radiological Physics and Technology - July 12, 2022 Category: Physics Source Type: research