A short length scatterer is adopted to measure the X-ray spectrum of computed tomography (CT) equipment with a wide irradiation field in the body axis direction. The purpose of this study is to compare X-ray spectra measured using different length scatterers and determine the most appropriate length for the scatterer. 320-slice CT equipment (Aquilion ONE) was used in this study. Circular carbonrods (3 cm diameter) with five different lengths (1–16 cm) were used as scatterers. The effect of the beam hardening phenomenon from different length carbon rods was evaluated according to the effective energy. The measurement accuracy for photon information was also evaluated based on the photon count corresponding to the characteristic X-ray. As a result, the beam hardening effect was scarcely observed when the 1 cm long scatterer was used, and the number of the photons measured for the characteristic X-ray was the most. Therefore, it was concluded that the 1 cm long circular carbon rod scatterer was the most suitable.
Computed tomographic angiography (CTA) has been used recently for the evaluation of intracerebral aneurysms, but it is difficult to use this technique to visualize aneurysms near the base of the skull because of the presence of bone. So, subtracted CTA has been used to separate vessels from bony structures. However, we see some misregistration when using subtraction method because of the patient moving, the disaccord of the X-ray tube orbit between the mask image and the live image, the expanding focus, and the bed bending. So, attentioning the difference of bone CT number in any tube voltages, we examined to make the image containing less misregistration by changing the tube voltage of mask image. Making a sham blood vessel, we examined the bone misregistration, the blood vessel volume, and the smoothness when changing the tube voltages of mask images. Comparing with 120 kV, as the tube voltage of the mask image was 80 kV, the bone misregistration decreased significantly, however the blood vessel volume decreased. As for the tube voltage of 100 kV, the bone misregistration decreased significantly, and the blood vessel volume and the smoothness were not significantly different so we could get coordinative image of 120 kV. When the tube voltage of the mask image becomes lower than that of the live image and the effective energy becomes different, the effect of misregistration is less. This method deals with changing the tube voltage only. So, it may be easy to make volume rendering (VR) image and this method may be used in every facility.
To evaluate whether electrocardiography-gated is useful in non-contrast-enhanced MRA with time-spatial labeling inversion pulse (Time-SLIP) in renal transplantation patients compared with respiration-triggered free-breathing. Simulation-based analyses of black blood time interval (BBTI) values for spatial selective inversion-recovery pulse and electrocardiography rates were performed, and confirmed on human subjects using a three-dimensional (3D) coherent steady-state free precession (SSFP) sequence on a 1.5 tesla Toshiba MRI scanner. Signal acquisition interval and BBTI values in which signal of a water tissue becomes the null point showed a strong correlation, and successfully suppressed signals from the background and provided better contrast between the arteries and the background. Because electrocardiography-gated non-contrast MRA does not depend on the respiration interval, providing a contrast stable, it was suggested to be an effective screening tool for evaluation of pelvic arteries.