Figure 4a. Pulsation artifacts. (a) Left anterior oblique coronary catheter angiogram demonstrates no significant stenosis at the RCA. Image reformation was performed to optimize coronary CT angiography. (b, c) Thin-slab MIP images created from data obtained in different cardiac cycles show different findings. In data sets with the reformation window starting 400 msec prior to the next R wave, apparent section gaps are observed (arrowheads in b), whereas mild stenosis seems to exist in data sets with the reformation window starting 200 msec prior to the next R wave (arrowhead in c).