title: Optimization of methods for quantification of rCBF using high-resolution [¹⁵O]H₂O PET images.
abstract: This study aimed to derive accurate estimates of regional cerebral blood flow (rCBF) from noisy dynamic [¹⁵O]H₂O PET images acquired on the high-resolution research tomograph, while retaining as much as possible the high spatial resolution of this brain scanner (2-3 mm) in parametric maps of rCBF. The PET autoradiographic method and generalized linear least-squares (GLLS), with fixed or extended to include spatially variable estimates of the dispersion of the measured input function, were compared to nonlinear least-squares (NLLS) for rCBF estimation. Six healthy volunteers underwent two [¹⁵O]H₂O PET scans with continuous arterial blood sampling. rCBF estimates were obtained from three image reconstruction methods (one analytic and two iterative, of which one includes a resolution model) to which a range of post-reconstruction filters (3D Gaussian: 2, 4 and 6 mm FWHM) were applied. The optimal injected activity was estimated to be around 11 MBq kg⁻¹ (800 MBq) by extrapolation of patient-specific noise equivalent count rates. Whole-brain rCBF values were found to be relatively insensitive to the method of reconstruction and rCBF quantification. The grey and white matter rCBF for analytic reconstruction and NLLS were 0.44 ± 0.03 and 0.15 ± 0.03 mL min⁻¹ cm⁻³, respectively, in agreement with literature values. Similar values were obtained from the other methods. For generation of parametric images using GLLS or the autoradiographic method, a filter of ≥ 4 mm was required in order to suppress noise in the PET images which otherwise produced large biases in the rCBF estimates.
authors.affiliation: Institute of Neurology, University College London, WC1N 3BG, UK. mwalker@physics.ubc.ca
authors.forename: M D
authors.initials: MD
authors.lastname: Walker
authors.forename: M
authors.initials: M
authors.lastname: Feldmann
authors.forename: J C
authors.initials: JC
authors.lastname: Matthews
authors.forename: J M
authors.initials: JM
authors.lastname: Anton-Rodriguez
authors.forename: S
authors.initials: S
authors.lastname: Wang
authors.forename: M J
authors.initials: MJ
authors.lastname: Koepp
authors.forename: M-C
authors.initials: MC
authors.lastname: Asselin
mesh_terms: D000328:Adult; D001345:Autoradiography; D002560:Cerebrovascular Circulation; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D016018:Least-Squares Analysis; D008297:Male; D008875:Middle Aged; D010104:Oxygen Radioisotopes; D049268:Positron-Emission Tomography / Q000379:methods*; D014867:Water
chemical_list: D010104:Oxygen Radioisotopes; D014867:Water