Fig. 4.

Two of the three clinical scans in this series. In the first scan, the curves with (a) and without (b) motion correction were virtually identical. This scan also had the highest recorded movement. In this patient the peak was perfectly estimated, which is not typically the norm. For another patient, there was only a minor underestimation of the peak in the motion-corrected scan, and the V_T error for this scan was 0.1% (c). However, in the scan without motion correction (d), the peak was poorly underestimated and appears as about one-third of the reference peak. Nevertheless, the V_T error was only 8.2%. Typically, errors in peak estimation are not very important when using graphical analyses, such as Patlak or Logan, because they mainly rely on the area under the curve of the input function. In contrast, compartmental modeling is less reliable when used with IDIF, because the individual rate constants are more sensitive to the shape of the input function and would be poorly estimated [1].