PROSPECTIVE COMPARISON OF HELICAL CT AND MR-IMAGING IN CLINICALLY SUSPECTED ACUTE PULMONARY-EMBOLISM

The purpose of this study is to compare sensitivity and specificity of helical CT and MR imaging for detecting acute pulmonary embolism [PE] . Patients who were suspected clinically of having PE were randomly as signed to undergo either helical contrast-enhanced CT or gradient-echo MR (if one modality was contraindicated, the patient was assigned to the other), Patients were considered to have PE if they had: 1) high-p robability V-Q scan and high clinical probability of PE; or 2) pulmona ry angiogram positive for PE. Patients were considered not to have PE if they had either: 1) normal V-Q scan: 2) low probability V-Q scan an d low clinical probability of PE; or 3) pulmonary angiogram negative f or PE. The CT and MR images were read randomly and independently by fi ve radiologists with varying levels of CT and MR experience. Twenty ei ght patients underwent CT and 25 MR, A total of 21 patients underwent pulmonary angiography (6 had PE, 15 did not have PE), Of the other 32 patients, 15 had high probability scan/high clinical probability and 1 7 had low probability scan/low clinical probability, For the five obse rvers, the average sensitivity of CT was 75% and of MR 46%; the averag e specificity of CT was 89% and I of MR 90%. Experience with vascular MR and enhanced CT influenced diagnostic accuracy. For the two vascula r MR experts, average sensitivity and specificity of MR were 71% and 9 7%, and of CT 73% and 97%. In this pilot study, when CT and MR were in terpreted with comparable expertise, they had similar accuracy for det ecting pulmonary embolism.