Image Derived Input Functions: Effects of Motion on Tracer Kinetic Analyses

PURPOSE: To quantify the effects of motion affected image-derived input functions (IDIF) on the outcome of tracer kinetic analyses. PROCEDURES: Two simulation studies, one based on high and the other on low cortical uptake, were performed. Different degrees of rotational and axial translational motion were added to the final frames of simulated dynamic positron emission tomography scans. Extracted IDIFs from motion affected simulated scans were compared to original IDIFs and to outcome of tracer kinetic analysis (volume of distribution, V (T)). RESULTS: Differences in IDIF values of up to 239% were found for the last frames. Patient motion of more than 6° or 5 mm resulted in at least 10% higher or lower V (T) values for the high cortical tracer. CONCLUSION: The degrees of motion studied are commonly observed in clinical studies and hamper the extraction of accurate IDIFs. Therefore, it is essential to ensure that patient motion is minimal and corrected for.