Extracorporeal high-frequency combined with contrast-enhanced ultrasound: a novel imaging method for detection and treatment evaluation of patients with cervical trachea-associated relapsing polychondritis

Background: This study aims to evaluate the clinical utility of extracorporeal high-frequency ultrasound (EHFU) combined with contrast-enhanced ultrasound (CEUS) for the diagnosis and treatment of cervical trachea-associated relapsing polychondritis (CT-RP). Methods: From January 2013 to January 2020, 24 patients with CT-RP diagnosed clinically and pathologically were retrospectively reviewed. We used EHFU to measure the thickness of trachea cartilage and the minimum internal transverse diameter of trachea and compared it with CT. The EHFU and CEUS imaging features were compared before and after treatment and used to evaluate the effects of therapy. Results: EHFU revealed the entire cervical tracheal cartilage (136 rings, of which 124 were abnormal). The average thickness of the 124 tracheal cartilage rings was 3.657 +/- 0.52 mm on EHFU and 3.32 +/- 0.76 mm on CT (t=1.482, P>0.05), while the diameter of the tracheal segment was 11.98 +/- 3.22 mm on EHFU and 10.8 +/- 2.92 mm on CT (t=1.005, P>0.05). After treatment, most patients (75%) showed no recurrence, and ultrasound revealed that the tracheal ring thickness was restored and the transverse diameter of the tracheal cavity was widened. Differences in EHFU measurements before and after treatment were statistically significant (both P<0.01). CEUS revealed that the tracheal cartilage layer was damaged in six cases (25%) and included structural destruction, deformation, and thinning. Follow-up evaluation revealed that the treatment outcomes of these cases were poor. The mean ultrasound examination time per patient was 10.0 +/- 2.3 min. Conclusions: EHFU combined with CEUS clearly and quickly revealed the CT-RP cervical tracheal wall, diameter of the trachea, and microstructural changes in tracheal cartilage. The effects of treatment can be reliably assessed by measuring reductions in tracheal cartilage thickening and echo changes before and after treatment. Dynamic monitoring of the condition provides timely and detailed information on cervical tracheal wall lesions and is valuable for clinical evaluation.