RESUMO
The aim of this study was to optimise the vessel angle as well as the stack number from the profiles of carbon dioxide digital subtraction angiography (CO2-DSA) images of a water phantom containing an artificial vessel tilted at different angles which imitate arteries in the body. The artificial vessel was tilted at 0°, 15°, and 30° relative to the horizontal axis with its centre as the pivot point, and CO2-DSA images were acquired at each vessel tilt angle. The maximum opacity method was used to stack up to four images of the next frame one by one. The signal-to-noise ratio (SNR) was determined from the profile curves. The Wilcoxon rank sum test was used to evaluate whether the profile curve and SNR differed depending on the vessel tilt angle or stack number, and a p-value of less than 0.05 was considered statistically significant. Images acquired at 0° had a significantly lower SNR than images acquired at 15° (p = 0.10). When the vessel angle was 30°, the profile curves were significantly improved (p < 0.05) when two or more images were stacked over the original image. Images with a good SNR were acquired at the vessel tilt angle of 15°, and the shape of the profile curve was improved when two or more images were stacked on the original image. This study demonstrates that the quality of images acquired using CO2-DSA can be significantly improved through parameter optimisation for image acquisition and post-processing.
RESUMO
The purpose was to investigate air-kerma area product (PKA) and entrance surface air-kerma rate ([Formula: see text]a,e) on the effect of the shape of automatic dose rate control (ADRC) in the presence of a wedge compensation filter. We compared and evaluated the variability of the X-ray output using a combination of wedge compensation filters and the ADRC. Two ADRC shapes (round and square) and three poly-methyl-methacrylate thicknesses (15, 20, and 25 cm) were used. A wedge compensation filter was inserted 2 cm at a time, up to 6 cm. When the wedge compensation filter was inserted to 6 cm for 20 cm of poly-methyl-methacrylate, the X-ray output fluctuated significantly. The PKA was reduced by 39% when the wedge compensation filter was inserted to 6 cm and by 59% when it was inserted to 4 cm under round-type for 20 cm poly-methyl-methacrylate. The shape of the ADRC affects [Formula: see text]a,e and PKA.