title: Multi-contrast attenuation map synthesis for PET/MR scanners: assessment on FDG and Florbetapir PET tracers.
abstract: Positron Emission Tomography/Magnetic Resonance Imaging (PET/MR) scanners are expected to offer a new range of clinical applications. Attenuation correction is an essential requirement for quantification of PET data but MRI images do not directly provide a patient-specific attenuation map. Methods We further validate and extend a Computed Tomography (CT) and attenuation map (μ-map) synthesis method based on pre-acquired MRI-CT image pairs. The validation consists of comparing the CT images synthesised with the proposed method to the original CT images. PET images were acquired using two different tracers ((18)F-FDG and (18)F-florbetapir). They were then reconstructed and corrected for attenuation using the synthetic μ-maps and compared to the reference PET images corrected with the CT-based μ-maps. During the validation, we observed that the CT synthesis was inaccurate in areas such as the neck and the cerebellum, and propose a refinement to mitigate these problems, as well as an extension of the method to multi-contrast MRI data. Results With the improvements proposed, a significant enhancement in CT synthesis, which results in a reduced absolute error and a decrease in the bias when reconstructing PET images, was observed. For both tracers, on average, the absolute difference between the reference PET images and the PET images corrected with the proposed method was less than 2%, with a bias inferior to 1%. Conclusion With the proposed method, attenuation information can be accurately derived from MRI images by synthesising CT using routine anatomical sequences. MRI sequences, or combination of sequences, can be used to synthesise CT images, as long as they provide sufficient anatomical information.
authors.affiliation: Translational Imaging Group, Centre for Medical Image Computing, University College London, NW1 2HE, London, UK, n.burgos.12@ucl.ac.uk.
authors.forename: Ninon
authors.initials: N
authors.lastname: Burgos
authors.forename: M Jorge
authors.initials: MJ
authors.lastname: Cardoso
authors.forename: Kris
authors.initials: K
authors.lastname: Thielemans
authors.forename: Marc
authors.initials: M
authors.lastname: Modat
authors.forename: John
authors.initials: J
authors.lastname: Dickson
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Schott
authors.forename: David
authors.initials: D
authors.lastname: Atkinson
authors.forename: Simon R
authors.initials: SR
authors.lastname: Arridge
authors.forename: Brian F
authors.initials: BF
authors.lastname: Hutton
authors.forename: Sébastien
authors.initials: S
authors.lastname: Ourselin
mesh_terms: D000814:Aniline Compounds; D001921:Brain / Q000000981:diagnostic imaging; D005026:Ethylene Glycols; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging; D064847:Multimodal Imaging; D049268:Positron-Emission Tomography; D011849:Radioactive Tracers; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed
chemical_list: D000814:Aniline Compounds; D005026:Ethylene Glycols; D011849:Radioactive Tracers; D019788:Fluorodeoxyglucose F18; C545186:florbetapir