To explore the characteristics of high-frame-rate contrast-enhanced ultrasound (H-CEUS) in Chinese thyroid imaging reporting and data system (C-TIRADS) 4-5 thyroid nodules.

One hundred and two patients with C-TIRADS 4-5 thyroid nodules (n=109) diagnosed at the First Affiliated Hospital of the Air Force Military Medical University from September 2022 to May 2023 were prospectively collected. H-CEUS and conventional contrast-enhanced ultrasound (C-CEUS) were performed. The characteristics of H-CEUS imaging were analyzed with regard to whether there was tortuous blood vessels in the nodules, enhancement direction, enhancement uniformity, enhancement intensity, whether the boundary was clear, and the time-intensity curve (TIC) parameters [arrival time (AT), time to peak (TTP), peak intensity (PI), maximum slope of rise curve (AS), and maximum slope of decline curve (DS)]. These features were then compared with the C-CEUS imaging features. Based on fine-needle aspiration or surgical pathology, the nodules were divided into either a benign group or a malignant group. The χ² test or Fisher exact probability method was used to compare the differences in imaging features between H-CEUS and C-CEUS in the two groups. Nonparametric Mann-Whitney test was used to compare the differences between C-CEUS and H-CEUS TIC parameters in the two groups.

Of the 109 nodules included, there were 48 benign nodules and 61 malignant nodules. In malignant nodules, H-CEUS showed that 78.7% (48/61) of the nodules had tortuous blood vessels after enhancement (C-CEUS showed 31.1%, χ²=27.843, P<0.001). In benign nodules, H-CEUS showed that 91.7% (44/48) of the nodules had a clear boundary after enhancement (C-CEUS showed 38.9%, χ²=36.984, P<0.001). H-CEUS and C-CEUS showed that there was no significant difference in enhancement direction, enhancement uniformity, or enhancement intensity between thyroid benign and malignant nodules after enhancement (P>0.05). In H-CEUS, the PI of benign nodules and malignant nodules was 24.18 (19.09, 31.20) and 18.20 (16.66, 23.91), respectively, significantly lower than that of C-CEUS [35.42 (25.83, 39.77) and 27.79 (25.88, 29.98), respectively; Z=-3.467 and -3.922; P=0.001 and <0.001, respectively]. In H-CEUS, DS [-0.11 (-0.15, -0.09)] was signifciantly higher than that of C-CEUS [-0.15 (-0.18, -0.12); Z=-2.578, P=0.010]. There was no significant difference in AT, TTP, or AS between H-CEUS and C-CEUS in both benign and malignant nodules (P>0.05).

H-CEUS can reflect the different enhancement characteristics of C-TIRADS 4-5 thyroid nodules, and has appreciated advantages in showing tortuous blood vessels and nodule boundary.