is passed to a function block 226 to perform appropriate actions consistent with poor quality images as shown in fig3 the heart position detection at block 212 of fig2 is indicated generally by the flowchart 300 a function block 310 receives an input image sequence and leads to a function block 312 to perform heart region of interest u201c roi u201d generation by 1 dimensional u201c 1 d u201d pseudo motion analysis block 312 leads to a function block 314 to perform heart center localization by a training based method block 314 in turn leads to a function block 316 to fit a sine curve to the heart centers of the images block 316 leads to a function block 318 to refine the heart center positions block 318 leads to a function block 320 to determine the heart bounding circle in operation heart detection includes the step 312 for roi determination by using 1 d pseudo motion analysis see xu chou and qian u201c determining the position range of the heart from a sequence of projection images using 1 d pseudo motion analysis u201d u s pat no 5 682 887 1997 thus a roi containing the heart can be determined this roi gives an upper limit and a lower limit in the vertical direction of the images see e g fig6 the training based heart detection of block 314 is based on two steps off line training and on line.