FIGURE 4. Scheme of algorithm of original method (A) and modified method (B). (A) R(t) and LV(t) correspond to measured time–activity curves in regional myocardial ROI and in left ventricle, respectively. Input function Ca(t), tissue time–activity curve Ct(t), and rMBF are derived from R(t) and LV(t). (B) W(t) corresponds to measured time–activity curve in whole myocardial ROI. Uniform input function Ca^whole(t) is derived from W(t) and LV(t). Then, each rMBF is estimated using a known input function Ca^whole(t) and R(t).