title: A pitfall of radioisotope quantification of the ratio of pulmonary blood flow to systemic blood flow (Qp/Qs) in a patient with severe postoperative pulmonary venous obstruction.
abstract: OBJECTIVE
  We report a case with initial misinterpretation of the radionuclide angiocardiographic study that was obtained in a child with persistent tachypnea and concern for residual left to right shunt after prior repair of total anomalous pulmonary veins and an atrial septal defect.
  
  
  METHODS
  Ultrasound, radionuclide angiocardiogram, and magnetic resonance imaging studies were obtained.
  
  
  RESULTS
  The radionuclide study was ordered after an unremarkable ultrasound. Unsuspected severely reduced left pulmonary arterial flow associated with high-grade ipsilateral pulmonary venous obstruction led to misinterpretation of the radionuclide study as a large residual shunt. Later replotting of the graphic data using each lung separately corrected the error. Magnetic resonance played a key role in making the correct diagnosis.
  
  
  CONCLUSIONS
  Significant asymmetric pulmonary flow due to vascular obstruction is an important additional potential pitfall to recognize in interpreting radionuclide angiocardiographic studies.
authors.affiliation: Hospital for Sick Children, Toronto, Ontario, Canada. bev.newman@stanford.edu
authors.forename: Beverley
authors.initials: B
authors.lastname: Newman
authors.forename: L
authors.initials: L
authors.lastname: Grosse-Wortmann
authors.forename: M
authors.initials: M
authors.lastname: Charron
authors.forename: S J
authors.initials: SJ
authors.lastname: Yoo
mesh_terms: D016477:Artifacts; D001783:Blood Flow Velocity; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D007223:Infant; D008168:Lung / Q000098:blood supply / Q000000981:diagnostic imaging*; D011182:Postoperative Care / Q000379:methods; D011183:Postoperative Complications / Q000000981:diagnostic imaging*; D011651:Pulmonary Artery / Q000000981:diagnostic imaging*; D011652:Pulmonary Circulation; D011668:Pulmonary Veno-Occlusive Disease / Q000000981:diagnostic imaging* / Q000209:etiology*; D011877:Radionuclide Imaging