title: Quantitative myocardial blood flow imaging with integrated time-of-flight PET-MR.
abstract: BACKGROUND
  The use of integrated PET-MR offers new opportunities for comprehensive assessment of cardiac morphology and function. However, little is known on the quantitative accuracy of cardiac PET imaging with integrated time-of-flight PET-MR. The aim of the present work was to validate the GE Signa PET-MR scanner for quantitative cardiac PET perfusion imaging. Eleven patients (nine male; mean age 59 years; range 46-74 years) with known or suspected coronary artery disease underwent15O-water PET scans at rest and during adenosine-induced hyperaemia on a GE Discovery ST PET-CT and a GE Signa PET-MR scanner. PET-MR images were reconstructed using settings recommended by the manufacturer, including time-of-flight (TOF). Data were analysed semi-automatically using Cardiac VUer software, resulting in both parametric myocardial blood flow (MBF) images and segment-based MBF values. Correlation and agreement between PET-CT-based and PET-MR-based MBF values for all three coronary artery territories were assessed using regression analysis and intra-class correlation coefficients (ICC). In addition to the cardiac PET-MR reconstruction protocol as recommended by the manufacturer, comparisons were made using a PET-CT resolution-matched reconstruction protocol both without and with TOF to assess the effect of time-of-flight and reconstruction parameters on quantitative MBF values.
  
  
  RESULTS
  Stress MBF data from one patient was excluded due to movement during the PET-CT scanning. Mean MBF values at rest and stress were (0.92 ± 0.12) and (2.74 ± 1.37) mL/g/min for PET-CT and (0.90 ± 0.23) and (2.65 ± 1.15) mL/g/min for PET-MR (p = 0.33 and p = 0.74). ICC between PET-CT-based and PET-MR-based regional MBF was 0.98. Image quality was improved with PET-MR as compared to PET-CT. ICC between PET-MR-based regional MBF with and without TOF and using different filter and reconstruction settings was 1.00.
  
  
  CONCLUSIONS
  PET-MR-based MBF values correlated well with PET-CT-based MBF values and the parametric PET-MR images were excellent. TOF and reconstruction settings had little impact on MBF values.
authors.affiliation: Nuclear Medicine & PET, Uppsala University, Uppsala, Sweden. tanja.kero@radiol.uu.se.|PET Center/Medical Imaging Center, Uppsala University Hospital, 75185, Uppsala, Sweden. tanja.kero@radiol.uu.se.
authors.forename: Tanja
authors.initials: T
authors.lastname: Kero
authors.affiliation: Nuclear Medicine & PET, Uppsala University, Uppsala, Sweden.|Center for Research and Development, Uppsala/Gävleborg County, Gävle, Sweden.
authors.forename: Jonny
authors.initials: J
authors.lastname: Nordström
authors.affiliation: Department of Nuclear Medicine and PET, Århus University Hospitals, Århus, Denmark.
authors.forename: Hendrik J
authors.initials: HJ
authors.lastname: Harms
authors.affiliation: Nuclear Medicine & PET, Uppsala University, Uppsala, Sweden.
authors.forename: Jens
authors.initials: J
authors.lastname: Sörensen
authors.affiliation: Radiology, Department of Surgical Sciences, Uppsala University, Uppsala, Sweden.
authors.forename: Håkan
authors.initials: H
authors.lastname: Ahlström
authors.affiliation: Nuclear Medicine & PET, Uppsala University, Uppsala, Sweden.
authors.forename: Mark
authors.initials: M
authors.lastname: Lubberink
keywords: 15O-water; Myocardial blood flow (MBF); PET-MR; Quantification; Time-of-flight (TOF)