Digital subtraction angiography: a comparison of 512(2) and 1024(2) imaging

A commercial DSA unit was modified by the manufacturer to permit 1024 X 1024 8-bit imaging. System upgrade includes a high-resolution 1049-line TV camera that operates with variable aperture to minimize x-ray exposure during 1024(2) imaging. To compare the change in resolution and radiation exposure between 512(2) and 1024(2) imaging with this system, a two-phase phantom study was performed using a high-contrast converging lead line phantom and a specially designed high-resolution low-contrast Lucite phantom. The two-phase phantom study tested general system resolution performance and resolution under simulated and actual clinical conditions for each field size (15, 25, and 36 cm). The 512(2) imaging was performed with the aperture reduced to the 512 setting; 1024(2) imaging was performed with the aperture at the 512 and 1024 values. The 1024(2) imaging resulted in only modest improvement in resolution compared to 512(2). While Nyquist limits were approached with 512(2) imaging, this was not the case with 1024(2) imaging. This suggests other factors such as system noise are playing a significant role in 1024(2) image degradation.