title: Image-derived input function in PET brain studies:  blood-based methods are resistant to motion artifacts.
abstract: BACKGROUND
  Image-derived input function (IDIF) from carotid arteries is an elegant alternative to full arterial blood sampling for brain PET studies. However, a recent study using blood-free IDIFs found that this method is particularly vulnerable to patient motion. The present study used both simulated and clinical [11C](R)-rolipram data to assess the robustness of a blood-based IDIF method (a method that is ultimately normalized with blood samples) with regard to motion artifacts.
  
  
  METHODS
  The impact of motion on the accuracy of IDIF was first assessed with an analytical simulation of a high-resolution research tomograph using a numerical phantom of the human brain, equipped with internal carotids. Different degrees of translational (from 1 to 20 mm) and rotational (from 1 to 15°) motions were tested. The impact of motion was then tested on the high-resolution research tomograph dynamic scans of three healthy volunteers, reconstructed with and without an online motion correction system. IDIFs and Logan-distribution volume (VT) values derived from simulated and clinical scans with motion were compared with those obtained from the scans with motion correction.
  
  
  RESULTS
  In the phantom scans, the difference in the area under the curve (AUC) for the carotid time-activity curves was up to 19% for rotations and up to 66% for translations compared with the motionless simulation. However, for the final IDIFs, which were fitted to blood samples, the AUC difference was 11% for rotations and 8% for translations. Logan-VT errors were always less than 10%, except for the maximum translation of 20 mm, in which the error was 18%. Errors in the clinical scans without motion correction appeared to be minor, with differences in AUC and Logan-VT always less than 10% compared with scans with motion correction.
  
  
  CONCLUSIONS
  When a blood-based IDIF method is used for neurological PET studies, the motion of the patient affects IDIF estimation and kinetic modeling only minimally.
authors: Molecular Imaging Branch, National Institute of Mental Health, NIH, Bethesda, Maryland 20892-2035, USA.
authors: Paolo
authors: P
authors: Zanotti-Fregonara
authors: Jeih-San
authors: JS
authors: Liow
authors: Claude
authors: C
authors: Comtat
authors: Sami S
authors: SS
authors: Zoghbi
authors: Yi
authors: Y
authors: Zhang
authors: Victor W
authors: VW
authors: Pike
authors: Masahiro
authors: M
authors: Fujita
authors: Robert B
authors: RB
authors: Innis
mesh_terms: D019540:Area Under Curve; D016477:Artifacts; D001921:Brain / Q000098:blood supply* / Q000000981:diagnostic imaging* / Q000502:physiology; D002339:Carotid Arteries / Q000000981:diagnostic imaging / Q000502:physiology; D006801:Humans; D007700:Kinetics; D008954:Models, Biological; D009068:Movement; D019047:Phantoms, Imaging; D049268:Positron-Emission Tomography / Q000379:methods*; D020889:Rolipram
chemical_list: D020889:Rolipram