FIGURE 2. Example of time–activity curves from arterial blood sampler (dashed lines) and from both large and small LV and AA ROIs (solid lines). (A) AA; 5-mm ROI. (B) LV; 5-mm ROI. (C) AA; 15-mm ROI. (D) LV; 15-mm ROI. These examples show close relationship of AA time–activity curves with those of blood sampler, overestimation of FDG activity with LV time–activity curves, higher noise levels in time–activity curves from small ROIs, and higher noise levels in time–activity curves from LV compared with those from AA.