To investigate the characteristics and clinical application of the time-intensity curve (TIC) of high-frame-rate contrast-enhanced ultrasound (H-CEUS) in clear cell renal cell carcinoma (CCRCC).

A total of 21 patients with CCRCC who underwent conventional contrast-enhanced ultrasound (C-CEUS) and H-CEUS examinations were selected at the First Affiliated Hospital of Nanchang University. TIC parameters of C-CEUS and H-CEUS were acquired and analyzed retrospectively, such as goodness of fit (GOF), base intensity (BI), arrival time (AT), time to peak (TTP), peak intensity (PI), ascending slope (AS), time to half peak intensity (DT/2), descending slope (DS), area under curve (AUC), and mean transit time (MTT). The paired t test was used to compare the TIC parameters of C-CEUS and H-CEUS between the lesions and the normal renal cortex. The equation ΔPI=(focal PI-normal renal cortex PI)/normal renal cortex PI was used for correction of BI, AT, TTP, AS, DT/2, DS, AUC, and MTT. Corrected TIC parameters of H-CEUS and C-CEUS were compared by the paired Wilcoxon signed-rank test.

The C-CEUS TIC parameters PI and DS of the lesions were significantly higher than those of the normal renal cortex [(49.93±6.02) dB vs (44.12±7.55) dB, t=5.300, P<0.001; 0.24±0.14 vs 0.22±0.12, t=-3.404, P=0.003], while DT/2 and MTT of the lesions were significantly smaller than those of the normal renal cortex [(140.38±26.51) s vs (150.98±29.27) s, t=-4.139, P=0.001; (130.95±26.54) s vs (142.03±29.72) s, t=-4.095, P=0.001]. There were no significant differences in GOF, BI, AT, TTP, AS, or AUC between the lesions and the normal renal cortex (P>0.05 for all). The H-CEUS TIC parameters AT, TTP, AS, and AUC of the lesions were significantly lower than those of the normal renal cortex [(9.41±2.73) s vs (10.40±3.03) s, t=-3.465, P=0.002; (27.17±6.17) s vs (30.13±6.66) s, t=-2.499, P=0.021; 0.94±0.36 vs 1.07±0.39, t=-2.688, P=0.014; 3064.47±844.52 vs 3378.62±993.54, t=-2.220, P=0.038], PI of the lesions was significantly greater than that of the normal renal cortex [(43.34±8.69) dB vs (40.30±7.05) dB, t=2.211, 0.039], while there was no statistically significant difference in GOF, BI, DT/2, DS, or MTT between the lesions and the normal renal cortex (P>0.05 for all). Comparing the corrected TIC parameters of H-CEUS with C-CEUS, ΔAT, ΔAS and ΔAUC of H-CEUS were significantly smaller than those of C-CEUS [-0.072 (-0.180, -0.022) vs -0.025 (-0.054, 0.053), Z=-2.242, P=0.025; -0.089 (-0.190, 0.083) vs 0.034 (-0.016, 0.074), Z=-2.520, P=0.012; -0.097 (-0.256, -0.004) vs -0.045 (-0.079, 0.266), Z=-2.033, P=0.042], while there were no significant differences in ΔBI, ΔTTP, ΔPI, ΔDT/2, ΔDS, or ΔMTT (P>0.05 for all). The TIC of H-CEUS of CCRCC was arching upward with a steep ascending branch and regressed slowly, and the distance between the TIC of the lesions and normal renal cortex was large.

The TIC of H-CEUS of CCRCC has certain characteristics. The perfusion period parameter ΔAT of H-CEUS is shorter than that of C-CEUS, but the absolute value of ΔAS is higher, which provides a basis for further analysis of contrast characteristics of the perfusion stage contrast features.