title: Free breathing contrast-enhanced time-resolved magnetic resonance angiography in pediatric and adult congenital heart disease.
abstract: BACKGROUND
  Contrast enhanced magnetic resonance angiography (MRA) is generally performed during a long breath-hold (BH), limiting its utility in infants and small children. This study proposes a free-breathing (FB) time resolved MRA (TRA) technique for use in pediatric and adult congenital heart disease (CHD).
  
  
  METHODS
  A TRA sequence was developed by combining spiral trajectories with sensitivity encoding (SENSE, x4 kx-ky and x2 kz) and partial Fourier (75% in kz). As no temporal data sharing is used, an independent 3D data set was acquired every ~1.3s, with acceptable spatial resolution (~2.3x2.3x2.3 mm). The technique was tested during FB over 50 consecutive volumes. Conventional BH-MRA and FB-TRA data was acquired in 45 adults and children with CHD. We calculated quantitative image quality for both sequences. Diagnostic accuracy was assessed in all patients from both sequences. Additionally, vessel measurements were made at the sinotubular junction (N = 43), proximal descending aorta (N = 43), descending aorta at the level of the diaphragm (N = 43), main pulmonary artery (N = 35), left pulmonary artery (N = 35) and the right pulmonary artery (N = 35). Intra and inter observer variability was assessed in a subset of 10 patients.
  
  
  RESULTS
  BH-MRA had significantly higher homogeneity in non-contrast enhancing tissue (coefficient of variance, P <0.0001), signal-to-noise ratio (P <0.0001), contrast-to-noise ratio (P <0.0001) and relative contrast (P = 0.02) compared to the FB-TRA images. However, homogeneity in the vessels was similar in both techniques (P = 0.52) and edge sharpness was significantly (P <0.0001) higher in FB-TRA compared to BH-MRA. BH-MRA provided overall diagnostic accuracy of 82%, and FB-TRA of 87%, with no statistical difference between the two sequences (P = 0.77). Vessel diameter measurements showed excellent agreement between the two techniques (r = 0.98, P <0.05), with no bias (0.0 mm, P = 0.71), and clinically acceptable limits of agreement (-2.7 to +2.8 mm). Inter and intra observer reproducibility showed good agreement of vessel diameters (r>0.988, P<0.0001), with negligible biases (between -0.2 and +0.1mm) and small limits of agreement (between -2.4 and +2.5mm).
  
  
  CONCLUSIONS
  We have described a FB-TRA technique that is shown to enable accurate diagnosis and vessel measures compared to conventional BH-MRA. This simplifies the MRA technique and will enable angiography to be performed in children and adults whom find breath-holding difficult.
authors.affiliation: UCL Centre for Cardiovascular Imaging, University College London, 30 Guildford Street, London, WC1N 1EH, UK. jennifer.steeden@ucl.ac.uk.
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Steeden
authors.affiliation: UCL Centre for Cardiovascular Imaging, University College London, 30 Guildford Street, London, WC1N 1EH, UK. b.pandya@ucl.ac.uk.|The Heart Hospital, University College London Hospital Foundation Trust, London, W1G 8PH, UK. b.pandya@ucl.ac.uk.
authors.forename: Bejal
authors.initials: B
authors.lastname: Pandya
authors.affiliation: Cardiorespiratory Unit, Great Ormond Street Hospital for Children, London, WC1N 3JH, UK. Oliver.Tann@gosh.nhs.uk.
authors.forename: Oliver
authors.initials: O
authors.lastname: Tann
authors.affiliation: UCL Centre for Cardiovascular Imaging, University College London, 30 Guildford Street, London, WC1N 1EH, UK. v.muthurangu@ucl.ac.uk.|Cardiorespiratory Unit, Great Ormond Street Hospital for Children, London, WC1N 3JH, UK. v.muthurangu@ucl.ac.uk.
authors.forename: Vivek
authors.initials: V
authors.lastname: Muthurangu
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D009202:Cardiomyopathies / Q000473:pathology*; D002648:Child; D003287:Contrast Media; D003331:Coronary Vessels / Q000473:pathology*; D005260:Female; D006330:Heart Defects, Congenital / Q000473:pathology*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D021621:Imaging, Three-Dimensional; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D008536:Meglumine; D008875:Middle Aged; D009206:Myocardium / Q000473:pathology*; D015588:Observer Variation; D009942:Organometallic Compounds; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012119:Respiration; D055815:Young Adult
chemical_list: D003287:Contrast Media; D009942:Organometallic Compounds; D008536:Meglumine; C072417:gadoterate meglumine