title: Fast and fully automatic calibration of frequency offset for balanced steady-state free precession cardiovascular magnetic resonance at 3.0 Tesla.
abstract: BACKGROUND
  This study proposed a fast and fully automatic calibration system to suppress the dark banding artifacts in balanced steady-state free precession (bSSFP) cardiovascular magnetic resonance (CMR) at 3.0 T.
  
  
  METHODS
  Twenty-one healthy volunteers (18 men, 3 women; mean age 24.9 years) participated in this study after providing institutionally approved consent. The optimal frequency was obtained using sweep scans of transition-band low flip-angle bSSFP (bSSFP-L), performed with three conditions: breath-hold plus electrocardiography (ECG) triggering (BH + ECG), breath-hold only (BH), and free breathing (FB). A real-time feedback system was implemented to allow the performing of bSSFP-L calibration scanning and conventional cine bSSFP within one breath-hold. For each scan condition, the optimal phase was estimated using 20-point and 10-point spline fitting.
  
  
  RESULTS
  Linear regression analysis indicated high correlation between the optimal phases obtained using BH and FB and those obtained using BH + ECG (R2 = 0.91 to 0.98, n = 21). The optimal phases obtained using 10-point datasets showed high correlation with the 20-point BH + ECG datasets (R2 = 0.92 to 0.99, n = 21); although the within-subject coefficient of variation (wsCV) was larger using 10-point fitting. The variation of repeated measurements was largest with FB acquisition and smallest with BH + ECG acquisition. The optimal frequency obtained by offline calculation and by real-time feedback calibration significantly reduced dark-band artifacts in cine bSSFP images (both p < .01).
  
  
  CONCLUSIONS
  The proposed real-time feedback calibration method for bSSFP imaging is rapid and fully automatic. This method could greatly reduce dark-band artifacts in bSSFP images and facilitate clinical CMR at 3.0 T.
authors.forename: Yu-Wei
authors.initials: YW
authors.lastname: Tang
authors.forename: Teng-Yi
authors.initials: TY
authors.lastname: Huang
authors.forename: Wen-Chau
authors.initials: WC
authors.lastname: Wu
mesh_terms: D000328:Adult; D016477:Artifacts; D001331:Automation / Q000592:standards; D062485:Breath Holding; D002138:Calibration; D055424:Cardiac-Gated Imaging Techniques; D004562:Electrocardiography; D005246:Feedback; D005260:Female; D064368:Healthy Volunteers; D006321:Heart / Q000033:anatomy & histology* / Q000502:physiology*; D006339:Heart Rate; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000592:standards*; D019028:Magnetic Resonance Imaging, Cine / Q000592:standards*; D008297:Male; D011237:Predictive Value of Tests; D012016:Reference Values; D015203:Reproducibility of Results; D013997:Time Factors; D055815:Young Adult