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.