[Report on the 89th Scientific Assembly and Annual Meeting of the Radiological Society of North America--cone beam artifact and helical artifact on the MDCT helical scan].

Because MDCT use narrow cone beam x-ray, to quantitatively evaluate cone beam artifact and helical artifact is very important with different x-ray beam width (detector configuration) . The both effect (helical artifact and cone beam artifact) was confirmed on the MDCT helical scan. It does not have cone beam artifact in the Isocenter or using center detector row for conventional scan, but helical artifact basically does not depend position of x-y plane. From quantitative evaluation of cone beam artifact, helical scan has fewer cone beam artifact than conventional scan on the 200 mm position of x-y plane: the cone beam artifact index is 11.76 (8 x 2.5mm conventional scan with most edge detector row) , 6.86 (8 x 2.5mm helical pitch 0.625) and 4.9 (8 x 2.5mm helical pitch 1.675). From phantom experiment, it was concluded that cone beam angle more contribute cone beam artifact than increasing slice numbers. And it was concluded that helical scan has fewer cone beam artifact than conventional scan, because helical scan use multi detector row information and special recon algorithm with cone beam correction on the GE LightSpeed MDCT scanner.