title: Novel phase-based noise reduction strategy for quantification of left ventricular function and mass assessment by cardiac CT: comparison with cardiac magnetic resonance.
abstract: BACKGROUND
  Tube current modulation in retrospective ECG gated cardiac computed tomography (CT) results in increased image noise and may reduce the accuracy of left ventricular (LV) ejection fraction (EF) and mass assessment.
  
  
  OBJECTIVE
  To examine the effects of a novel CT phase-based noise reduction (NR) algorithm on LV EF and mass quantification as compared to cardiac magnetic resonance (CMR).
  
  
  METHODS
  In 40 subjects, we compared the LV EF and mass between CT and CMR. In a subset of 24 subjects with tube current modulated CT, the effect of phase-based noise reduction strategies on contrast-to-noise ratio (CNR) and the assessment of LV EF and mass was compared to CMR.
  
  
  RESULTS
  There was excellent correlation between CT and CMR for EF (r=0.94) and mass (r=0.97). As compared to CMR, the limits of agreement improved with increasing strength of NR strategy. There was a systematic underestimation of LV mass by CT compared to CMR with no NR (-10.3±10.1g) and low NR (-10.3±12.5g), but was attenuated with high NR (-0.5±8.3g). Studies without NR had lower CNR compared to low and high NR at both the ES phase and ED phase (all p<0.01).
  
  
  CONCLUSIONS
  A high NR strategy on tube current modulated functional cardiac CT improves correlation of EF compared to CMR and reduces variability of EF and mass evaluation by increasing the CNR. In an effort to reduce radiation dose with tube current modulation, this strategy provides better image quality when LV function and mass quantification is needed.
authors.affiliation: Cardiac MR PET CT Program, Division of Cardiology and Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA. bwai@partners.org
authors.forename: Bryan
authors.initials: B
authors.lastname: Wai
authors.forename: Wai-Ee
authors.initials: WE
authors.lastname: Thai
authors.forename: Heather
authors.initials: H
authors.lastname: Brown
authors.forename: Quynh A
authors.initials: QA
authors.lastname: Truong
mesh_terms: D000328:Adult; D055424:Cardiac-Gated Imaging Techniques / Q000379:methods*; D003324:Coronary Artery Disease / Q000150:complications / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D008297:Male; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D059629:Signal-To-Noise Ratio; D013318:Stroke Volume; D014057:Tomography, X-Ray Computed / Q000379:methods*; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging* / Q000209:etiology