Discrimination of Types of Venous Emboli Using Doppler Ultrasound

Background

Many studies have identified features of the emboli traveling in the arterial system by Doppler ultrasound, and estimated their composition and size for anticipation of cerebral infarct. Another concern is features of the emboli in the venous system for anticipation of pulmonary embolism (PE). The objective is to prove that the emboli in the venous system can be discriminated by Doppler ultrasound in animal study and to assess whether PE can be predicted by using this technique in clinical case.

Methods

Animal study—lard oil, thrombus, or bone marrow was injected to the femoral veins in pigs. High intensity transient signals were transhepatically identified at the inferior vena cava using Doppler ultrasound. Intensity volume (dB) and frequency shift (Hz) of each signal were obtained. The cutoff values at which thrombi, fat emboli, and marrow emboli could be discriminated were calculated by receiver-operating characteristic curves analysis.

Human study—Subjects were 47 patients who underwent total knee arthroplasty. On postoperative day 0 and 1, High intensity transient signals were identified at the affected common femoral vein using Doppler ultrasound. Contrast computed tomography was done, and the patients were divided into two groups according to the presence of PE. The two groups were distinguished by intensity volume (dB) and frequency shift (Hz) of each signal and calculated the sensitivity and specificity. The statistics analysis was done as in animal study.

Results

Animal study—Thrombus and bone marrow could be discriminated from lard oil well at frequency shift of 208 Hz and 196 Hz (with sensitivity of 86.9, 85.7%, and specificity of 82.3%, 91.8%, respectively).

Human study—The sensitivity and specificity were 76.7 and 75.0% to discriminate patients with and without PE at frequency shift of 208 Hz.

Conclusions

Our animal study results indicated that emboli could be identified and discriminated in the venous system. Clinical study informed that the frequency shift (208 Hz) of the Doppler signal was the best parameter to discriminate PE with and without PE in patients with total knee arthroplasty.