CCD camera for dual-energy digital subtraction angiography.
A motion immune dual-energy subtraction technique in which X-ray tube voltage and beam filtration were switched at 30 Hz between 60 kVp (2.0 mm Al filter) and 120 kVp (2.00 mm Al+2.5 mm Cu filter) was previously reported. In this study the effects of camera lag on the dual-energy iodine signal is investigated. The temporal lag of the lead oxide vidicon tested reduced the dual-energy iodine signal by a factor of 2.3, as compared to a mode that included 4 scrub frames between low- and high-energy images, for an iodine phantom with thicknesses of 0-86.0 mg/cm(2), imaged over a 15 cm thick Lucite phantom. On the other hand, the Charge-Coupled Device (CCD) camera has inherently no temporal lag and its versatile scanning characteristics make it near ideal for dual-energy DSA. The CCD camera eliminates the reduction of dual-energy iodine signal, since it does not mix low- and high-energy image data. Another benefit of the CCD camera is that the separation time between low and high-energy images is not limited to the frame period, as is the lead oxide vidicon; and as small as a 5-msec time difference is possible. The short time interval between low and high-energy images minimizes motion misregistration artifacts. Due to these advantages, the CCD camera significantly improves the utility of dual-energy DSA.
Molloi
S
S
Dept. of Radiol. Sci., California Univ., Irvine, CA.
Ersahin
A
A
Qian
Y J
YJ