Contrast of Paddle wheel technique and standard axial CT displayed significantly high sensitivity and specificity in detecting central pulmonary embolism

Abstract

Paddle wheel technique is a reconstruction method of displaying images, which uses planar slabs pivot on the central horizontal axis at bifurcation of pulmonary artery trunk. With this method, each image depicts complete track of branching structures from central hilum to the periphery. Objective: The purpose of this study was to assess the role of paddle wheel reformation and compare it with standard axial multi detector CT images in cases of pulmonary embolism. Methods: CT scans of 50 patients presented for CT pulmonary angiography were selected and interpreted by two radiologists using reformatted paddle wheel technique besides standard axial CT scans. The scans were reviewed independently and randomly to reduce bias. Standard axial CT scan for pulmonary embolism was carried out with collimation of 1.25 mm, pitch of six and a reconstruction interval of 0.8 mm. Paddle wheel reconstruction was carried out by using inbuilt software, setting 5 mm slab thickness and 5 degree rotation. Reference standard was overall interpretation of axial CT scans by both the radiologists. Results: Sensitivity and specificity for axial images was between 90 to 100%; sensitivity for paddle wheel technique ranged from 65 to 72% while specificity turned out to be 80 to 100%. Final consensus agreement for standard axial imaging was higher than paddle wheel technique. Conclusion: No significant difference between two imaging methods was noted in cases of central pulmonary embolism, however standard axial imaging was better than paddle wheel technique in detecting peripheral pulmonary embolism.