The Doppler shift is an angle dependent function. Based on the relationship between frequency shift and angle, direction-finding method can be used directly to obtain the ranging solution based on frequency shift measurement. The Doppler ranging solution obtained by this method has excellent calculation accuracy and can keep the same accuracy as the ranging solution based on frequency shift difference processing.

Lemierre’s syndrome (LS) is a rare clinical condition characterized by septic thrombophlebitis of the internal or external jugular vein, usually following an oropharyngeal infection. Here, we present a 20-year-old male patient who developed diarrhea, nausea, and vomiting after receiving clarithromycin for an upper respiratory tract infection. On admission, he had fever, hypotension, and elevation in acute phase reactants (WBC: 20,410/µL, CRP: 197 mg/L). Empirical treatment with ceftriaxone and metronidazole was initiated. Stool and throat cultures were negative. On the second day, abdominal tenderness developed; direct abdominal radiograph showed dilated bowel loops, but toxic megacolon was excluded during follow-up. Thoracic CT revealed septic emboli in the lungs. Due to persistent fever despite ceftriaxone and metronidazole therapy, treatment was escalated to meropenem on the fifth day. On the same day, blood cultures grew Fusobacterium necrophorum, raising suspicion of LS. Doppler ultrasound detected a thrombus in the left external jugular vein. Anticoagulant therapy with low-molecular-weight heparin and clopidogrel was initiated. The fever resolved by the seventh day of full antibiotherapy After three weeks of intravenous therapy, follow-up imaging showed regression of the thrombus. The patient completed a four-week course of antibiotics and anticoagulants and was discharged with full recovery. This case highlights the diagnostic challenge of LS presenting with gastrointestinal symptoms and emphasizes the importance of early blood cultures and imaging. External jugular vein involvement due to F. necrophorum is rare and should be considered in patients presenting with septic emboli.

Aiming at the time complexity of singular value spectrum weighted Hankel SVD filtering algorithm, a clutter suppression algorithm for ultrasonic color Doppler imaging based on BP neural network model is proposed in this paper. Firstly, using the PRF data collected by portable ultrasound instrument, we verify the singular value weighted Hankel SVD filtering algorithm, and the results show that the algorithm has high accuracy; Then, the BP neural network model is established based on the input and output data of singular value weighted Hankel-SVD filtering algorithm; Finally, the clutter suppression algorithm of ultrasonic color Doppler imaging based on BP neural network model is established. The experimental results show that compared with Hankel SVD filtering algorithm, the clutter suppression algorithm proposed in this paper greatly shortens the operation time without reducing the accuracy, so as to improve the real-time performance of the filtering algorithm.