Diagnosis of subsegmental pulmonary emboli: a multi-center study using a porcine model

We measured sensitivity, positive predictive value, and free-response receiver operating characteristic (FROC) of 20 radiologists detecting subsegmental-sized pulmonary emboli in a porcine model using either contrast-enhanced computed tomography (CT) or digital subtraction (DS) pulmonary angiography. Colored methacrylate beads (4.2 and 3.8 mm diameter) were injected into 9 anesthetized juvenile pigs. CT and DS pulmonary angiography images were obtained before and after a pulmonary infiltrate was introduced into the lower lobes. Following imaging, the pigs were euthanized, and the pulmonary arterial tree was cast using clear methacrylate allowing direct visualization of emboli. The 20 radiologists used a custom-made computer application to display the images on their personal computer and record their diagnoses. The results were mailed electronically to the coordinating center for comparison with the cast of the pulmonary vasculature. Twenty-three emboli were included in the statistical analysis. Overall sensitivity for spiral CT and angiography, respectively, was: 60 +/- 18% and 72 +/- 11% (P = 0.06). Positive predictive value for spiral CT and angiography, respectively, was: 49 +/- 24% and 58 +/- 23% (P = 0.25). There was a large variation in both sensitivity and positive predicted values between Readers. There was no difference in sensitivity or positive predictive value between radiologists from community or academic centers (P > 0.27). FROC analysis showed no significant difference between CT or DS (P = 0.27). In conclusion, in this porcine model, there is no overall diagnostic advantage to using DS pulmonary angiography rather than contrast-enhanced spiral CT for the diagnosis of PE when images are interpreted by radiologists located in either academic or community hospital settings.