[Examination of scan parameters that influence image quality in three-dimensional rotational angiography(3D-RA)].
Because the imaging qualities of three-dimensional rotational angiography(3D-RA)are influenced by various imaging parameters, it is difficult to obtain high-quality images from 3D-RA. In this study, we compared two methods of 3D-RA, the propeller rotation technique(PRT)and the roll rotation technique(RRT)by changing image intensifier(I.I.)sizes(5, 7 and 9 inches)using a test chart and handmade phantom. The results of this study demonstrated that one of the factors determining the image quality of 3D-RA was spatial resolution. Therefore, it was important to choose an optimum I.I. size that was similar in size to collimating the region of interest(ROI)in clinical use. Another factor influencing image quality was radiographic condition, especially the setting of tube voltage. This factor was indispensable in obtaining good image contrast, but the use of high-voltage exposure was one of the reasons for lower image contrast. Therefore, if image contrast was insufficient, the image qualities of 3D-RA became worse with increasing tube voltage because the tube voltage in this study was automatically changed according to scanning method and I.I. size. In addition, because the spatial resolution of PRT was similar to that of RRT, we thought it better to use PRT because the data acquisition time(scan time)of this technique was 4 seconds shorter than that of RRT, whereas, if PRT was used, it was necessary to set a suitable rate of injection of contrast medium because the setting of the tube voltage of PRT was 10 kV higher than that of RRT. In conclusion, to improve the image qualities of 3D-RA, we considered it necessary to obtain sufficient image contrast not influenced by high tube voltage and to choose an optimum I.I. size suitable for the spatial resolution of ROI.
Naramidate
Naoko
N
Department of Radiology, Sapporo Azabu Neurosurgical Hospital.
Kodera
Shuichi
S
D000792:Angiography / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D019047:Phantoms, Imaging; D012399:Rotation