The method presented by Liu et al. in 1998 has generally been used in Japan to calculate the wedge factor of the enhanced dynamic wedge (EDW). When the points used to evaluate the dose exist outside the central beam axis in the half field (HF), however, a difference of about 3% can occur between the values calculated by this method and the measured values. In 2003, Liu et al. presented a new general formula for calculating MU using the EDW. We modified the formula for calculating the wedge factor by combining the conventional calculation formula and the formula of Liu et al., presented in 2003, and compared the calculated values of the wedge factor of the EDW in the HF with the measured values. Our formula employs a very simple method in which only the normalized golden segmented treatment table (NGSTT) on the center of the radiation field and the central beam axis are added to the existing formula. The values calculated by our formula and the measured values were consistent within 1% in most combinations of energy, wedge angle, and size of radiation field. When the EDW was used for irradiation to the tangent line of the HF breast, in particular, the values calculated by our formula and the measured values were consistent within 0.5%, and it was possible to calculate the wedge factor with a higher degree of accuracy than that calculated with the existing formula.
This study used functional magnetic resonance imaging (fMRI) to evaluate brain function. fMRI data were collected by a block paradigm, and brain function was evaluated. However, irrelevant artifacts caused by the BOLD effect frequently occur in analytical processing. Therefore, there is a limit to obtaining an adequate activating reaction in the analytical system, which is normally equipped with MRI. However, there is a limit to obtaining a sufficient activating reaction in the analytical system, which is normally equipped with MRI. It has become standard practice to use an analytical system such as statistical parametric mapping (SPM). The response of movement of cerebrospinal fluid (CSF) artifact is high. Therefore, disappearance of the CSF artifact was done by statistical analysis. Then, the response of the signal from the beginning of stimulation was examined. As a result, the activating signal and the artifact signal could be identified.
The physical characteristics of a direct amorphous Selenium (a-Se) digital fluoroscopy and radiography system were investigated. Pre-sampled modulation transfer functions (MTF) were measured using a slit method. Noise power spectra were determined for different input exposures by fast Fourier transform of uniformly exposed samples. The MTFs of direct digital radiography systems showed significantly higher values than those of indirect digital radiography and screen-film systems. The direct digital radiography systems showed higher noise levels compared with those of indirect systems under roughly the same exposure conditions. Contrast-detail analysis was performed to compare detection by direct digital radiography systems with that of the screen-film (FUJI HG-M2/UR2) systems. The average contrast-detail curves of digital and film images were obtained from the results of observation. Image quality figures (IQF) were also calculated from the individual observer performance tests. The results indicated that digital contrast-detail curves and IQF are, on average, are equal those of the screen-film system.
In interventional radiology (IVR) of cerebral aneurysms, it is important to understand the form and physical relationships between the cerebral aneurysm and the surrounding vessels. However, because the vessels in the head area are highly complex, it can be difficult to comprehend the structure using conventional angiography. Therefore, three-dimensional rotational angiography (3D-RA) has been used in recent years. This article discusses studies of the spatial resolution of 3D-RA. We reconstructed 3D-RA of an acrylic slit phantom (slit widths: 0.5, 0.75, 1.0, 1.5 mm) and examined spatial resolution by visual evaluation and profile curves. When the slit phantom was arranged to avoid the effect of beam hardening, the spatial resolution of 3D-RA was found to be as high as 0.75 mm. When the slit phantom was placed orthogonal to the rotational axis of the C-arm, the spatial resolution of 3D-RA was decreased because of the cone angle effect of X-rays. However, it was considered within the allowable range for clinical study. Consequently, 3D-RA is valuable in IVR.
In axial zygomatic arch roentgenography, the radiographic angle is determined by taking account of the light field-projected image. However, this method is technically difficult and has poor reproducibility because the body target surface is uncertain at the time of positioning. Therefore, we obtained 3D-CT images from CT examinations of the facial or paranasal sinus, and we assessed the X-ray beam angle where the zygomatic arch is most clearly delineated in terms of sex and age by taking the acanthion-meatal line (France horizon) as the reference. The zygomatic arch was most clearly seen when the X-ray beam angle was perpendicular to the acanthion-meatal line. Excellent images were obtained, and reproducibility of the images was improved using the radiographic technique based on this result.