title: Optimization of brain PET imaging for a multicentre trial: the French CATI experience.
abstract: BACKGROUND
  CATI is a French initiative launched in 2010 to handle the neuroimaging of a large cohort of subjects recruited for an Alzheimer's research program called MEMENTO. This paper presents our test protocol and results obtained for the 22 PET centres (overall 13 different scanners) involved in the MEMENTO cohort. We determined acquisition parameters using phantom experiments prior to patient studies, with the aim of optimizing PET quantitative values to the highest possible per site, while reducing, if possible, variability across centres.
  
  
  METHODS
  Jaszczak's and 3D-Hoffman's phantom measurements were used to assess image spatial resolution (ISR), recovery coefficients (RC) in hot and cold spheres, and signal-to-noise ratio (SNR). For each centre, the optimal reconstruction parameters were chosen as those maximizing ISR and RC without a noticeable decrease in SNR. Point-spread-function (PSF) modelling reconstructions were discarded. The three figures of merit extracted from the images reconstructed with optimized parameters and routine schemes were compared, as were volumes of interest ratios extracted from Hoffman acquisitions. The net effect of the 3D-OSEM reconstruction parameter optimization was investigated on a subset of 18 scanners without PSF modelling reconstruction.
  
  
  RESULTS
  Compared to the routine parameters of the 22 PET centres, average RC in the two smallest hot and cold spheres and average ISR remained stable or were improved with the optimized reconstruction, at the expense of slight SNR degradation, while the dispersion of values was reduced. For the subset of scanners without PSF modelling, the mean RC of the smallest hot sphere obtained with the optimized reconstruction was significantly higher than with routine reconstruction. The putamen and caudate-to-white matter ratios measured on 3D-Hoffman acquisitions of all centres were also significantly improved by the optimization, while the variance was reduced.
  
  
  CONCLUSIONS
  This study provides guidelines for optimizing quantitative results for multicentric PET neuroimaging trials.
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, CNRS, INSERM, Laboratoire d'Imagerie Biomédicale, F-75013, Paris, France. habert@upmc.fr.|Centre pour l'Acquisition et le Traitement des Images (www.cati-neuroimaging.com), Paris, France. habert@upmc.fr.|AP-HP, Hôpital Pitié-Salpêtrière, Département de Médecine Nucléaire, F-75013, Paris, France. habert@upmc.fr.|Faculté de Médecine - Laboratoire d'Imagerie Biomédicale, 91 Boulevard de l'Hôpital, F-75013, Paris, France. habert@upmc.fr.
authors.forename: Marie-Odile
authors.initials: MO
authors.lastname: Habert
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, CNRS, INSERM, Laboratoire d'Imagerie Biomédicale, F-75013, Paris, France.|Centre pour l'Acquisition et le Traitement des Images (www.cati-neuroimaging.com), Paris, France.
authors.forename: Sullivan
authors.initials: S
authors.lastname: Marie
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, CNRS, INSERM, Laboratoire d'Imagerie Biomédicale, F-75013, Paris, France.|Centre pour l'Acquisition et le Traitement des Images (www.cati-neuroimaging.com), Paris, France.
authors.forename: Hugo
authors.initials: H
authors.lastname: Bertin
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, CNRS, INSERM, Laboratoire d'Imagerie Biomédicale, F-75013, Paris, France.|Centre pour l'Acquisition et le Traitement des Images (www.cati-neuroimaging.com), Paris, France.
authors.forename: Moana
authors.initials: M
authors.lastname: Reynal
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, CNRS, INSERM, Laboratoire d'Imagerie Biomédicale, F-75013, Paris, France.|Centre pour l'Acquisition et le Traitement des Images (www.cati-neuroimaging.com), Paris, France.
authors.forename: Jean-Baptiste
authors.initials: JB
authors.lastname: Martini
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, CNRS, INSERM, Laboratoire d'Imagerie Biomédicale, F-75013, Paris, France.|Centre pour l'Acquisition et le Traitement des Images (www.cati-neuroimaging.com), Paris, France.
authors.forename: Mamadou
authors.initials: M
authors.lastname: Diallo
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, CNRS, INSERM, Laboratoire d'Imagerie Biomédicale, F-75013, Paris, France.|Centre pour l'Acquisition et le Traitement des Images (www.cati-neuroimaging.com), Paris, France.|AP-HP, Hôpital Pitié-Salpêtrière, Département de Médecine Nucléaire, F-75013, Paris, France.
authors.forename: Aurélie
authors.initials: A
authors.lastname: Kas
authors.affiliation: CEA-Service Hospitalier Frédéric Joliot, F-91401, Orsay, France.
authors.forename: Régine
authors.initials: R
authors.lastname: Trébossen
keywords: Multicentre trials; Neurology; PET/CT; Quality assurance; Standardization