Electron beam CT (EBCT): clinical application in diagnosis of pulmonary embolism

Objective: To evaluate the effectiveness of EBCT in diagnosis of pulmonary embolism (PE). Methods: 20 patients aged from 28-78 years had PE demonstrated by EBCT. EBCT study was performed using Imatron C-150 scanner. Continuous volume scan (CVS) or single slice mode (SSM) were used with slice thickness of 3 mm or 6 mm. Scan time was 0.1 s. Nonionic contrast medium was administered by automatic injector with flow rate of 2.8-3.3 ml/s and total dosage of 45-90 ml. Delay time was 10-20 s. Results: Among 442 pulmonary arteries in 20 cases, 255 vessels were involved with PE(57.7%). 47.5% of pulmonary artery trunk, main pulmonary artery and inter-lobar artery, 63.3% of lobar artery and 59.7% of segmental artery had PE. EBCT features of PE: (1) Direct signs: 1) Intraluminal filling defect: including partial filling defect (76.9%), mural filling defect (9.2%), total occlusion (9.6%) and railway-track sign (4.3%). The first three signs indicate chronic PE and the last one (railway-track sign) indicate acute PE. It's very important to distinguish chronic from acute PE from the stand point of clinical treatment. 2) Smaller caliber of pulmonary artery, low and nonuniform density of contrast medium in arterial lumen (mediastinal window). 2) Secondary signs: Include 'mosaic sign' (lung window), focus of pulmonary infarction, local oligemia, enlargement and failure of right ventricle. Conclusions: EBCT is a noninvasive and effective method for examining PE. It can play a significant role in clinical diagnosis of PE