title: Automated quality control of emission-transmission misalignment for attenuation correction in myocardial perfusion imaging with SPECT-CT systems.
abstract: BACKGROUND
  Emission-transmission misalignment with single-photon emission computed tomography (SPECT)-computed tomography (CT) systems can impair attenuation correction (AC) in myocardial perfusion imaging. This study was performed to develop automated quality control (Auto-QC) to detect critical misalignment that can significantly impact AC.
  
  
  RESULTS
  Auto-QC was developed to segment myocardium and mediastinum from emission and transmission reconstructions, respectively. Myocardium-mediastinum mismatch was used as the quality-control index (QCI). The QCI threshold for acceptable AC was determined with NCAT (NURBS [nonuniform rational B-spline]-based cardiac torso phantom) simulation and verified with 2 patients with minimal misalignment. Compromised data sets, generated by shifting the attenuation maps by 0.5, 1.0, 1.5, and 2.0 pixels along left-right, up-down, and head-foot directions, respectively, were qualitatively and quantitatively compared with the unshifted data sets. Auto-QC was tested with the 2 verification patients and 41 additional patients. Shifts by more than 1 pixel along any direction compromised AC. Auto-QC with the QCI threshold (3%) had highly concordant results with manual quality control in the detection of critical misalignment (sensitivity of 88% and 90% and specificity of 93% and 95% for the tests by use of the 2 verification patients and 41 additional patients, respectively).
  
  
  CONCLUSIONS
  QCI quantitatively represented the severity of misalignment. Auto-QC can help clinicians be aware of critical misalignment and can assist in realignment of SPECT and CT images.
authors.affiliation: Emory University School of Medicine, Atlanta, GA 30322, USA, and Zhongshan Hospital, Fudan University, Shanghai, China. jchen22@emory.edu
authors.forename: Ji
authors.initials: J
authors.lastname: Chen
authors.forename: Serpil F
authors.initials: SF
authors.lastname: Caputlu-Wilson
authors.forename: Hongcheng
authors.initials: H
authors.lastname: Shi
authors.forename: James R
authors.initials: JR
authors.lastname: Galt
authors.forename: Tracy L
authors.initials: TL
authors.lastname: Faber
authors.forename: Ernest V
authors.initials: EV
authors.lastname: Garcia
mesh_terms: D000465:Algorithms; D016477:Artifacts; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D019047:Phantoms, Imaging; D011785:Quality Assurance, Health Care / Q000379:methods; D011786:Quality Control; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D013382:Subtraction Technique; D015899:Tomography, Emission-Computed, Single-Photon / Q000295:instrumentation / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*; D018487:Ventricular Dysfunction, Left / Q000175:diagnosis*