title: Left-to-right cardiac shunts: comparison of measurements obtained with MR velocity mapping and with radionuclide angiography.
abstract: OBJECTIVE
  To investigate the agreement between two noninvasive methods, magnetic resonance (MR) velocity mapping and first-pass radionuclide angiography, to quantify the pulmonary-to-systemic blood flow ratio (QP/QS) in adults, adolescents, and children with left-to-right cardiac shunts.
  
  
  METHODS
  The accuracy and precision of MR velocity mapping were studied in 12 control subjects (six men, six women) and in a phantom. MR velocity mapping and radionuclide angiography were performed on the same day in 24 patients (16 adults, two adolescents, six children; five male patients, 19 female patients).
  
  
  RESULTS
  The mean error in QP/QS at MR velocity mapping in phantom experiments was -1% +/- 1 (mean +/- SD). In control subjects, QP/QS at MR velocity mapping was 1.03 +/- 0.03, and the cardiac index was 3.1 L/min/m2 +/- 0.2 and 3.2 L/min/m2 +/- 0.3 for women and men, respectively. In patients, QP/QS at radionuclide angiography was 14% +/- 13, higher than at MR velocity mapping. Interobserver variability was four times higher for radionuclide angiography compared with MR velocity mapping, 0% + 16 versus 0% +/- 4 (n = 12). The difference between repeated MR flow measurements in the same vessel was -1% +/- 5 (n = 36).
  
  
  CONCLUSIONS
  The data suggest that MR velocity mapping is accurate and precise for measurements of shunt size over the whole range of possible QP/QS values.
authors.affiliation: Department of Clinical Physiology, Lund University Hospital, Sweden.
authors.forename: H
authors.initials: H
authors.lastname: Arheden
authors.forename: C
authors.initials: C
authors.lastname: Holmqvist
authors.forename: U
authors.initials: U
authors.lastname: Thilen
authors.forename: K
authors.initials: K
authors.lastname: Hanséus
authors.forename: G
authors.initials: G
authors.lastname: Björkhem
authors.forename: O
authors.initials: O
authors.lastname: Pahlm
authors.forename: S
authors.initials: S
authors.lastname: Laurin
authors.forename: F
authors.initials: F
authors.lastname: Ståhlberg
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D005260:Female; D006330:Heart Defects, Congenital / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011652:Pulmonary Circulation; D015646:Ventriculography, First-Pass