title: Characterization of cardiac quiescence from retrospective cardiac computed tomography using a correlation-based phase-to-phase deviation measure.
abstract: OBJECTIVE
  Accurate knowledge of cardiac quiescence is crucial to the performance of many cardiac imaging modalities, including computed tomography coronary angiography (CTCA). To accurately quantify quiescence, a method for detecting the quiescent periods of the heart from retrospective cardiac computed tomography (CT) using a correlation-based, phase-to-phase deviation measure was developed.
  
  
  METHODS
  Retrospective cardiac CT data were obtained from 20 patients (11 male, 9 female, 33-74 yr) and the left main, left anterior descending, left circumflex, right coronary artery (RCA), and interventricular septum (IVS) were segmented for each phase using a semiautomated technique. Cardiac motion of individual coronary vessels as well as the IVS was calculated using phase-to-phase deviation. As an easily identifiable feature, the IVS was analyzed to assess how well it predicts vessel quiescence. Finally, the diagnostic quality of the reconstructed volumes from the quiescent phases determined using the deviation measure from the vessels in aggregate and the IVS was compared to that from quiescent phases calculated by the CT scanner. Three board-certified radiologists, fellowship-trained in cardiothoracic imaging, graded the diagnostic quality of the reconstructions using a Likert response format: 1 = excellent, 2 = good, 3 = adequate, 4 = nondiagnostic.
  
  
  RESULTS
  Systolic and diastolic quiescent periods were identified for each subject from the vessel motion calculated using the phase-to-phase deviation measure. The motion of the IVS was found to be similar to the aggregate vessel (AGG) motion. The diagnostic quality of the coronary vessels for the quiescent phases calculated from the aggregate vessel (PAGG) and IVS (PIV S) deviation signal using the proposed methods was comparable to the quiescent phases calculated by the CT scanner (PCT). The one exception was the RCA, which improved for PAGG for 18 of the 20 subjects when compared to PCT (PCT = 2.48; PAGG = 2.07, p = 0.001).
  
  
  CONCLUSIONS
  A method for quantifying the motion of specific coronary vessels using a correlation-based, phase-to-phase deviation measure was developed and tested on 20 patients receiving cardiac CT exams. The IVS was found to be a suitable predictor of vessel quiescence. The diagnostic quality of the quiescent phases detected by the proposed methods was comparable to those calculated by the CT scanner. The ability to quantify coronary vessel quiescence from the motion of the IVS can be used to develop new CTCA gating techniques and quantify the resulting potential improvement in CTCA image quality.
authors: School of Electrical and Computer Engineering, Georgia Institute of Technology, 777 Atlantic Drive Northwest, Atlanta, Georgia 30332.
authors: Carson A
authors: CA
authors: Wick
authors: School of Electrical and Computer Engineering, Georgia Institute of Technology, 777 Atlantic Drive Northwest, Atlanta, Georgia 30332.
authors: James H
authors: JH
authors: McClellan
authors: Department of Radiology, University of British Columbia, 3350-950 West 10th Avenue, Vancouver, British Columbia V5Z 4E3, Canada.
authors: Chesnal D
authors: CD
authors: Arepalli
authors: Department of Radiology and Imaging Sciences, Emory University, Division of Cardiothoracic Imaging, 1364 Clifton Road Northeast, Suite 309, Atlanta, Georgia 30322.
authors: William F
authors: WF
authors: Auffermann
authors: Department of Radiology and Imaging Sciences, Emory University, Division of Cardiothoracic Imaging, 1364 Clifton Road Northeast, Suite 309, Atlanta, Georgia 30322.
authors: Travis S
authors: TS
authors: Henry
authors: Department of Radiology and Imaging Sciences, Emory University, Division of Emergency Radiology, 550 Peachtree Street Northeast, Atlanta, Georgia 30308.
authors: Faisal
authors: F
authors: Khosa
authors: School of Medicine, Emory University, 100 Woodruff Circle, Atlanta, Georgia 30322.
authors: Adam M
authors: AM
authors: Coy
authors: Department of Radiology and Imaging Sciences, Emory University, Winship Cancer Institute, 1701 Uppergate Drive Northeast, Suite 5018, Atlanta, Georgia 30322 and School of Electrical and Computer Engineering, Georgia Institute of Technology, 777 Atlantic Drive Northwest, Atlanta, Georgia 30332.
authors: Srini
authors: S
authors: Tridandapani
mesh_terms: D000328:Adult; D000368:Aged; D017023:Coronary Angiography; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging* / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed; D054088:Ventricular Septum / Q000000981:diagnostic imaging
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