DEPICTION OF PULMONARY EMBOLI WITH SPIRAL CT - OPTIMIZATION OF DISPLAY WINDOW SETTINGS IN A PORCINE MODEL

PURPOSE: To determine optimal spiral computed tomographic (CT) image d isplay for depiction of pulmonary emboli (PE). MATERIALS AND METHODS: Autologous PE detected in 10 pigs with contrast material-enhanced spir al CT were displayed with six display window settings (standard medias tinal window and five modified windows referenced to attenuation value s in pulmonary artery [PA] branches). The thrombus gray level and gray level contrast and separability of PE versus those of the local PA br anch were computed for each window setting; results were compared with repeated measured analysis of variance. RESULTS: Of 114 PE detected p athologically, 28 were visible with spiral CT. Two of the 28 PE were n ot detectable with standard mediastinal windows. Statistically signifi cantly improved gray level contrast and separability were noted with m odified windows referenced to the second-order PA branch and the local PA branch than with the standard mediastinal and other modified windo w settings (P < .05). However, thrombus gray level was statistically s ignificantly higher with the standard mediastinal window (P < .05). CO NCLUSION: PE are best depicted as filling defects when displayed with a modified window referenced to the right or left main PA attenuation. Standard mediastinal windows are useful for identifying vessels that are occluded completely with PE.