title: Clinical evaluation of a block sequential regularized expectation maximization reconstruction algorithm in 18F-FDG PET/CT studies.
abstract: OBJECTIVE
  To investigate the clinical performance of a block sequential regularized expectation maximization (BSREM) penalized likelihood reconstruction algorithm in oncologic PET/computed tomography (CT) studies.
  
  
  METHODS
  A total of 410 reconstructions of 41 fluorine-18 fluorodeoxyglucose-PET/CT studies of 41 patients with a total of 2010 lesions were analyzed by two experienced nuclear medicine physicians. Images were reconstructed with BSREM (with four different β values) or ordered subset expectation maximization (OSEM) algorithm with/without time-of-flight (TOF/non-TOF) corrections. OSEM reconstruction postfiltering was 4.0 mm full-width at half-maximum; BSREM did not use postfiltering. Evaluation of general image quality was performed with a five-point scale using maximum intensity projections. Artifacts (category 1), image sharpness (category 2), noise (category 3), and lesion detectability (category 4) were analyzed using a four-point scale. Size and maximum standardized uptake value (SUVmax) of lesions were measured by a third reader not involved in the image evaluation.
  
  
  RESULTS
  BSREM-TOF reconstructions showed the best results in all categories, independent of different body compartments. In all categories, BSREM non-TOF reconstructions were significantly better than OSEM non-TOF reconstructions (P<0.001). In almost all categories, BSREM non-TOF reconstruction was comparable to or better than the OSEM-TOF algorithm (P<0.001 for general image quality, image sharpness, noise, and P=1.0 for artifact). Only in lesion detectability was OSEM-TOF significantly better than BSREM non-TOF (P<0.001). Both BSREM-TOF and BSREM non-TOF showed a decreasing SUVmax with increasing β values (P<0.001) and TOF reconstructions showed a significantly higher SUVmax than non-TOF reconstructions (P<0.001).
  
  
  CONCLUSIONS
  The BSREM reconstruction algorithm showed a relevant improvement compared with OSEM reconstruction in PET/CT studies in all evaluated categories. BSREM might be used in clinical routine in conjunction with TOF to achieve better/higher image quality and lesion detectability or in PET/CT-systems without TOF-capability for enhancement of overall image quality as well.
authors.affiliation: Departments of aNuclear Medicine bDiagnostic and Interventional Radiology cNeuroradiology, University Hospital Zurich dUniversity of Zurich, Zurich, Switzerland ePET Clinical Science, GE Healthcare, Waukesha, Wisconsin, USA.
authors.forename: Bert-Ram
authors.initials: BR
authors.lastname: Sah
authors.forename: Paul
authors.initials: P
authors.lastname: Stolzmann
authors.forename: Gaspar
authors.initials: G
authors.lastname: Delso
authors.forename: Scott D
authors.initials: SD
authors.lastname: Wollenweber
authors.forename: Martin
authors.initials: M
authors.lastname: Hüllner
authors.forename: Yahya A
authors.initials: YA
authors.lastname: Hakami
authors.forename: Marcelo A
authors.initials: MA
authors.lastname: Queiroz
authors.forename: Felipe de Galiza
authors.initials: FG
authors.lastname: Barbosa
authors.forename: Gustav K
authors.initials: GK
authors.lastname: von Schulthess
authors.forename: Carsten
authors.initials: C
authors.lastname: Pietsch
authors.forename: Patrick
authors.initials: P
authors.lastname: Veit-Haibach
mesh_terms: D000465:Algorithms; D016477:Artifacts; D015331:Cohort Studies; D005462:Fluorine Radioisotopes; D019788:Fluorodeoxyglucose F18; D006801:Humans; D016013:Likelihood Functions; D015999:Multivariate Analysis; D009369:Neoplasms / Q000000981:diagnostic imaging; D015588:Observer Variation; D000072078:Positron Emission Tomography Computed Tomography / Q000379:methods / Q000706:statistics & numerical data*; D019275:Radiopharmaceuticals; D059629:Signal-To-Noise Ratio
chemical_list: D005462:Fluorine Radioisotopes; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18