title: Comparison of an alternative and existing binning methods to reduce the acquisition duration of 4D PET/CT.
abstract: OBJECTIVE
  Respiratory motion is a source of artifacts that reduce image quality in PET. Four dimensional (4D) PET/CT is one approach to overcome this problem. Existing techniques to limiting the effects of respiratory motions are based on prospective phase binning which requires a long acquisition duration (15-25 min). This time is uncomfortable for the patients and limits the clinical exploitation of 4D PET/CT. In this work, the authors evaluated an existing method and an alternative retrospective binning method to reduce the acquisition duration of 4D PET/CT.
  
  
  METHODS
  The authors studied an existing mixed-amplitude binning (MAB) method and an alternative binning method by mixed-phases (MPhB). Before implementing MPhB, they analyzed the regularity of the breathing patterns in patients. They studied the breathing signal drift and missing CT slices that could be challenging for implementing MAB. They compared the performance of MAB and MPhB with current binning methods to measure the maximum uptake, internal volume, and maximal range of tumor motion.
  
  
  RESULTS
  MPhB can be implemented depending on an optimal phase (in average, the exhalation peak phase -4.1% of the entire breathing cycle duration). Signal drift of patients was in average 35% relative to the breathing amplitude. Even after correcting this drift, MAB was feasible in 4D CT for only 64% of patients. No significant differences appeared between the different binning methods to measure the maximum uptake, internal volume, and maximal range of tumor motion. The authors also determined the inaccuracies of MAB and MPhB to measure the maximum amplitude of tumor motion with three bins (less than 3 mm for movement inferior to 12 mm, up to 6.4 mm for a 21 mm movement).
  
  
  CONCLUSIONS
  The authors proposed an alternative binning method by mixed-phase binning that halves the acquisition duration of 4D PET/CT. Mixed-amplitude binning was challenging because of signal drift and missing CT slices. They showed that more than three bins were necessary for a more accurate measurement of the maximum amplitude of the tumor motion. However, the current 4D-CT technology limits the increase of the number of bins in 4D PET/CT because of missing CT slices. One can reconstruct 4D PET images with more bins but without attenuation/scatter correction.
authors.affiliation: SIMAD, LU 50, Université Toulouse III Paul Sabatier, Toulouse 31062, France.
authors.forename: David
authors.initials: D
authors.lastname: Didierlaurent
authors.affiliation: Institut Claudius Regaud, 20-24 Rue du Pont Saint-Pierre, Toulouse 31052, France.
authors.forename: Cyril
authors.initials: C
authors.lastname: Jaudet
authors.affiliation: SIMAD, LU 50, Université Toulouse III Paul Sabatier, Toulouse 31062, France.
authors.forename: Sophie
authors.initials: S
authors.lastname: Ribes
authors.affiliation: IRIT-INPT, Université Toulouse III Paul Sabatier, Toulouse 31071, France.
authors.forename: Hadj
authors.initials: H
authors.lastname: Batatia
authors.affiliation: Institut Claudius Regaud, 20-24 Rue du Pont Saint-Pierre, Toulouse 31052, France.
authors.forename: Lawrence O
authors.initials: LO
authors.lastname: Dierickx
authors.affiliation: Institut Claudius Regaud, 20-24 Rue du Pont Saint-Pierre, Toulouse 31052, France.
authors.forename: Slimane
authors.initials: S
authors.lastname: Zerdoud
authors.affiliation: Institut Claudius Regaud, 20-24 Rue du Pont Saint-Pierre, Toulouse 31052, France.
authors.forename: Severine
authors.initials: S
authors.lastname: Brillouet
authors.affiliation: Institut Claudius Regaud, 20-24 Rue du Pont Saint-Pierre, Toulouse 31052, France.
authors.forename: Kathleen
authors.initials: K
authors.lastname: Weyts
authors.affiliation: GCS CHU-CLCC, Université Toulouse III Paul Sabatier, Toulouse 31052, France.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Courbon
authors.affiliation: SIMAD, LU 50, Université Toulouse III Paul Sabatier, Toulouse 31062, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Caselles
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D005260:Female; D056973:Four-Dimensional Computed Tomography / Q000379:methods*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008297:Male; D008875:Middle Aged; D009068:Movement; D049268:Positron-Emission Tomography / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted; D012119:Respiration; D012984:Software; D014057:Tomography, X-Ray Computed / Q000379:methods*