title: Probabilistic atlas-based segmentation of combined T1-weighted and DUTE MRI for calculation of head attenuation maps in integrated PET/MRI scanners.
abstract: We present a new MRI-based attenuation correction (AC) approach for integrated PET/MRI systems that combines both segmentation- and atlas-based methods by incorporating dual-echo ultra-short echo-time (DUTE) and T1-weighted (T1w) MRI data and a probabilistic atlas. Segmented atlases were constructed from CT training data using a leave-one-out framework and combined with T1w, DUTE, and CT data to train a classifier that computes the probability of air/soft tissue/bone at each voxel. This classifier was applied to segment the MRI of the subject of interest and attenuation maps (μ-maps) were generated by assigning specific linear attenuation coefficients (LACs) to each tissue class. The μ-maps generated with this "Atlas-T1w-DUTE" approach were compared to those obtained from DUTE data using a previously proposed method. For validation of the segmentation results, segmented CT μ-maps were considered to the "silver standard"; the segmentation accuracy was assessed qualitatively and quantitatively through calculation of the Dice similarity coefficient (DSC). Relative change (RC) maps between the CT and MRI-based attenuation corrected PET volumes were also calculated for a global voxel-wise assessment of the reconstruction results. The μ-maps obtained using the Atlas-T1w-DUTE classifier agreed well with those derived from CT; the mean DSCs for the Atlas-T1w-DUTE-based μ-maps across all subjects were higher than those for DUTE-based μ-maps; the atlas-based μ-maps also showed a lower percentage of misclassified voxels across all subjects. RC maps from the atlas-based technique also demonstrated improvement in the PET data compared to the DUTE method, both globally as well as regionally.
authors.affiliation: Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School Charlestown, MA, USA ; Department of Psychiatry, Massachusetts General Hospital Boston, MA, USA.
authors.forename: Clare B
authors.initials: CB
authors.lastname: Poynton
authors.affiliation: Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School Charlestown, MA, USA ; Department of Health Sciences and Technology, Massachusetts Institute of Technology Cambridge, MA, USA.
authors.forename: Kevin T
authors.initials: KT
authors.lastname: Chen
authors.affiliation: Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School Charlestown, MA, USA ; Program in Biophysics, Harvard University Cambridge, MA, USA.
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Chonde
authors.affiliation: Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School Charlestown, MA, USA.
authors.forename: David
authors.initials: D
authors.lastname: Izquierdo-Garcia
authors.affiliation: Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School Charlestown, MA, USA ; Department of Psychiatry, Massachusetts General Hospital Boston, MA, USA.
authors.forename: Randy L
authors.initials: RL
authors.lastname: Gollub
authors.affiliation: Department of Neurology, Massachusetts General Hospital Cancer Center Boston, MA, USA.
authors.forename: Elizabeth R
authors.initials: ER
authors.lastname: Gerstner
authors.affiliation: Department of Neurology, Massachusetts General Hospital Cancer Center Boston, MA, USA.
authors.forename: Tracy T
authors.initials: TT
authors.lastname: Batchelor
authors.affiliation: Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School Charlestown, MA, USA.
authors.forename: Ciprian
authors.initials: C
authors.lastname: Catana
keywords: MRI; PET; atlas; attenuation correction; segmentation
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