title: OS-EM and FBP reconstructions at low count rates: effect on 3D PET studies of [11C] WAY-100635.
abstract: 11C-labeled neuroreceptor ligands frequently require long scan durations to quantify ligand-receptor binding. In this paper, we compare the accuracy of two three-dimensional (3D) positron emission tomography (PET) reconstructions: ordered-subset expectation-maximization (OS-EM) versus filtered backprojection (FBP) under low count rate conditions exhibited by 11C neuroreceptor studies. Data were obtained from a dynamic 11C phantom acquisition as well as six dynamic human [11C] WAY-100635 studies, all acquired in 3D mode using the EXACT HR+ PET scanner. Model-based scatter correction of the phantom datum was found to overcorrect in low count rate situations producing a negative bias in FBP reconstruction and a positive bias in OS-EM reconstruction, the OS-EM bias attributed to the non-negativity constraint of sinogram values. In the phantom OS-EM and FBP, reconstruction bias occurred at activities less than 25 Bq/cm3. In the human cerebellum, OS-EM deviated from FBP at activities less than 50 Bq/cm3. The total volume of distribution (VT), as determined from the metabolite corrected arterial input function and a two-tissue compartment kinetic model, was more sensitive to the positive bias of OS-EM than the negative bias of FBP at low count rates. To avoid reconstruction bias with 3D PET studies using the HR+, the scan duration should be limited so as to yield a final non-decay-corrected activity concentration of no less than 50 Bq/cm3. In neuroreceptor studies, if such a low count rate cannot be avoided, FBP reconstruction is preferable to OS-EM to estimate VT.
authors.affiliation: Division of Neuroscience, New York State Psychiatric Institute, New York, NY, USA. belanger@neuron.cpmc.columbia.edu
authors.forename: Marie José
authors.initials: MJ
authors.lastname: Bélanger
authors.forename: J John
authors.initials: JJ
authors.lastname: Mann
authors.forename: Ramin V
authors.initials: RV
authors.lastname: Parsey
mesh_terms: D000465:Algorithms; D016477:Artifacts; D001921:Brain / Q000000981:diagnostic imaging*; D002250:Carbon Radioisotopes; D002531:Cerebellum / Q000000981:diagnostic imaging; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging; D019047:Phantoms, Imaging; D010879:Piperazines / Q000493:pharmacokinetics; D017397:Prefrontal Cortex / Q000000981:diagnostic imaging; D011725:Pyridines / Q000493:pharmacokinetics; D011903:Raphe Nuclei / Q000000981:diagnostic imaging; D044282:Receptor, Serotonin, 5-HT1A / Q000378:metabolism*; D012680:Sensitivity and Specificity; D012702:Serotonin Antagonists / Q000493:pharmacokinetics; D014055:Tomography, Emission-Computed / Q000379:methods*
chemical_list: D002250:Carbon Radioisotopes; D010879:Piperazines; D011725:Pyridines; D012702:Serotonin Antagonists; D044282:Receptor, Serotonin, 5-HT1A; C090413:N-(2-(4-(2-methoxyphenyl)-1-piperazinyl)ethyl)-N-(2-pyridinyl)cyclohexanecarboxamide