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 previous ly reported. In this study the effects of camera lag on the dual energ y iodine signal is investigated. The temporal lag of the lead oxide vi dicon 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 h igh-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, t he Charge-Coupled Device (CCD) camera has inherently no temporal lag a nd its versatile scanning characteristics make it near ideal for dual- energy DSA. The CCD camera eliminates the reduction of dual-energy iod ine signal, since it does not mix low- and high-energy image data. Ano ther 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 possib le. The short time interval between low and high-energy images minimiz es motion misregistration artifacts. Due to these advantages, the CCD camera significantly improves the utility of dual-energy DSA.