Detection of Benign Cervical Tracheal Stenosis with in Vitro High-frequency Ultrasound: a Preliminary Study

Background: High-frequency ultrasound (HFU) is non-invasive and non-radiative technique, which has high resolution and can be easily used in follow up. The aim of this paper is to investigate the imaging characteristics and application of high-frequency ultrasound in the detection of benign cervical tracheal stenosis. Methods: A total of 23 patients who underwent bronchoscopy which proved benign cervical tracheal stenosis were recruited and underwent to in vitro high frequency ultrasonography. The imaging characteristics were compared with those of healthy subjects. Variables related to tracheal stenosis were compared with those in bronchoscopy. Results: 1) In patients with tracheal stenosis, high-frequency ultrasonography showed irregular shape at the stenotic segment which presented intermittent, discontinued or disappeared continuity, uneven thickness of tracheal wall and abnormal echoes. These findings were significantly different from those in control group (P<0.05); 2) The diameter of trachea at the most stenotic segment or the diameter of endotracheal stent was 8.52±2.68 mm (range: 4~14 mm) in the high-frequency ultrasonography and 8.39±2.79 mm (range: 2~14 mm) in bronchoscopy showing no significant difference (t=0.514, P=0.613), but the diameter in high-frequency ultrasonography was relevant with that in bronchoscopy (r=0.89, 95%CI: 0.87, 0.91). Conclusion: For patients with cervical tracheal stenosis mainly at the anterior tracheal wall and those receiving tracheal stenting, high frequency ultrasound can identify the abnormal structure at the stenotic segment and be used to evaluate the diameter of stenotic trachea. The in vitro high frequency ultrasound can provide imaging characteristics to determine the therapeutic efficacy and the follow up of tracheal stenosis.