title: Automated axial right ventricle to left ventricle diameter ratio computation in computed tomography pulmonary angiography.
abstract: OBJECTIVE
  Right Ventricular to Left Ventricular (RV/LV) diameter ratio has been shown to be a prognostic biomarker for patients suffering from acute Pulmonary Embolism (PE). While Computed Tomography Pulmonary Angiography (CTPA) images used to confirm a clinical suspicion of PE do include information of the heart, a numerical RV/LV diameter ratio is not universally reported, likely because of lack in training, inter-reader variability in the measurements, and additional effort by the radiologist. This study designs and validates a completely automated Computer Aided Detection (CAD) system to compute the axial RV/LV diameter ratio from CTPA images so that the RV/LV diameter ratio can be a more objective metric that is consistently reported in patients for whom CTPA diagnoses PE.
  
  
  METHODS
  The CAD system was designed specifically for RV/LV measurements. The system was tested in 198 consecutive CTPA patients with acute PE. Its accuracy was evaluated using reference standard RV/LV radiologist measurements and its prognostic value was established for 30-day PE-specific mortality and a composite outcome of 30-day PE-specific mortality or the need for intensive therapies. The study was Institutional Review Board (IRB) approved and HIPAA compliant.
  
  
  RESULTS
  The CAD system analyzed correctly 92.4% (183/198) of CTPA studies. The mean difference between automated and manually computed axial RV/LV ratios was 0.03±0.22. The correlation between the RV/LV diameter ratio obtained by the CAD system and that obtained by the radiologist was high (r=0.81). Compared to the radiologist, the CAD system equally achieved high accuracy for the composite outcome, with areas under the receiver operating characteristic curves of 0.75 vs. 0.78. Similar results were found for 30-days PE-specific mortality, with areas under the curve of 0.72 vs. 0.75.
  
  
  CONCLUSIONS
  An automated CAD system for determining the CT derived RV/LV diameter ratio in patients with acute PE has high accuracy when compared to manual measurements and similar prognostic significance for two clinical outcomes.
authors.affiliation: Madrid-MIT M+Visión Consortium, Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America; Surgical Planning Laboratory, Brigham and Women´s Hospital, Boston, Massachusetts, United States of America.
authors.forename: Germán
authors.initials: G
authors.lastname: González
authors.affiliation: Biomedical Image Technologies, Universidad Politécnica de Madrid & CIBER-BBN, Madrid, Spain.
authors.forename: Daniel
authors.initials: D
authors.lastname: Jiménez-Carretero
authors.affiliation: Biomedical Image Technologies, Universidad Politécnica de Madrid & CIBER-BBN, Madrid, Spain.
authors.forename: Sara
authors.initials: S
authors.lastname: Rodríguez-López
authors.affiliation: Applied Imaging Science Laboratory, Brigham and Women´s Hospital, Boston, Massachusetts, United States of America.
authors.forename: Kanako K
authors.initials: KK
authors.lastname: Kumamaru
authors.affiliation: Applied Imaging Science Laboratory, Brigham and Women´s Hospital, Boston, Massachusetts, United States of America.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: George
authors.affiliation: Surgical Planning Laboratory, Brigham and Women´s Hospital, Boston, Massachusetts, United States of America.
authors.forename: Raúl
authors.initials: R
authors.lastname: San José Estépar
authors.affiliation: Applied Imaging Science Laboratory, Brigham and Women´s Hospital, Boston, Massachusetts, United States of America.
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Rybicki
authors.affiliation: Biomedical Image Technologies, Universidad Politécnica de Madrid & CIBER-BBN, Madrid, Spain.
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Ledesma-Carbayo
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000792:Angiography / Q000379:methods; D005260:Female; D006352:Heart Ventricles / Q000000981:diagnostic imaging*; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011379:Prognosis; D011655:Pulmonary Embolism / Q000000981:diagnostic imaging*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods; D055815:Young Adult