Lisette van Dam

CTPP for short-term clinical outcome prediction in acute PE 10 157 Image acquisition and analysis Since June 2017, CTPP is part of the standard CT angiography protocol in adult patients with suspected PE at our hospital. CT examinations were performed on a 320-multislice detector row CT scan (Canon). CTPP images were acquired using subtraction technique, in which the pre-contrast image is subtracted from the contrast-enhanced image. The subtraction image is then colour coded and fused with the CTPA images; normal perfusion: yellow to orange, moderately decreased perfusion: red to pink, severely decreased or absent perfusion: purple to dark blue/black ( Figure 1 ). Figure 1 . A. Fused parametric perfusion map with CTPA, axial and B. coronal image in a patient with an acute thrombus in the right lower lobe pulmonary artery (encircled) with subsegmental reduced lung perfusion in the laterodorsal segment of the right lower lobe. For this analysis, CTPP and CTPA image reading was performed independently by two different readers, who were unaware of presenting symptoms and occurrence of adverse events. CTPP assessment was performed by a researcher (L.F.V.D.) trained by an expert thoracic radiologist (L.J.M.K.). Perfusion defects were quantified per segment using the score proposed by Chae et al and expressed as mean PDS in percentage. 10 To assess the interobserver agreement for PDS reading CTPP images of 25 consecutive patients were independently evaluated by a second reviewer (L.K.). RV/LV ratio, pulmonary artery trunk diameter and total thrombus load on CTPA were evaluated by one expert thoracic radiologist (L.J.M.K.) with over 20 years of experience in pulmonary CTPA-reading. The maximum diameters of both the right and left ventricle were measured in the standard axial view with measurement of the maximal distance between the ventricular endocardium and the interventricular septum. The pulmonary artery trunk was measured at its