Diagnosis of pulmonary embolism: Comparison of CT angiography and MR angiography in canines

PURPOSE: To compare the sensitivity and specificity of helical computed tom ographic angiography (CTA), CTA with multiplanar reconstructions (MPR)/thre e-dimensional-shaded surface display (3D-SSD), and gadolinium-enhanced magn etic resonance angiography (MRA) for pulmonary embolism (PE) detection, MATERIALS AND METHODS: Gelatin sponge emboli were introduced into the femor al veins of seven dogs and conventional digital subtraction angiography (CA ), CTA, and MRA performed. Images from CTA, CTA with MPR/3D-SSD, and MRA we re reviewed for the presence of PE in lobar and segmental arteries, and sub segmental zones, Postmortem angiography and CA were the gold standard, RESULTS: There were 50 emboli in the 294 vessels/zones analyzed. The sensit ivity of CTA for the two readers was 76% (95% confidence interval [CI]; 64% -88%) and 64% (95% CI; 50%-78%), and for the two MRA readers was 52% (95% C I; 38%-66%) and 48% (95% CI; 34%-62%), CTA was more sensitive than MRA when PE were subdivided by vessel caliber, Specificity was high for CTA and MRA among all readers (98.8%-99.6%). MPR/3D-SSD did not improve results of axi al CT. MRA perfusion defects were 46% and 47% sensitive and 100% specific. Interobserver agreement was high for CTA and MRA (kappa 0.92 and 0.93, resp ectively). The average diameter of vessels with emboli was 3.7 mm +/- 1.06, CONCLUSION: Helical CTA is more sensitive than three-dimensional gadolinlum -enhanced MRA for the detection of PE, Both CTA and MRA are highly specific for PE detection and demonstrate high interobserver agreement, MPR/3D-SSD did not increase CTA performance over axial images alone.