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目的探讨肝脏肿瘤射频消融前后的弹性变化以及实时剪切波弹性成像(SWE)对消融范围的显示能力。方法 2012年2月至2013年12月于中山大学附属第一医院行射频消融治疗并获得完全消融的肝脏肿瘤患者57例共57个病灶,平均直径(2.4±1.1)cm。分别于消融前及消融后30 min、1 d、1个月进行SWE,测量消融灶的杨氏模量最大值(SWE_max)、最小值(SWE_min)、平均值(SWE_mean)及离散度(SWE_SD)。比较肝脏肿瘤消融前后不同时间点的杨氏模量值。选择经Cool-tip射频消融系统持续消融12 min的消融灶,于消融后1个月分别在二维声像图、SWE图像上测量其长径和短径,根据公式V=π×X×Y×Z/6(V为体积,X为长径、Y=Z为短径)计算消融灶体积,与当天超声造影无增强区域范围进行比较。结果 (1)消融后30 min的SWE_max、SWE_min、SWE_mean及SWE_SD分别为(121.80±68.52)、(30.36±24.96)、(66.92±24.88)和(20.37±12.97)k Pa,消融后1 d上述指标分别为(108.20±46.99)、(31.87±18.08)、(67.12±23.53)和(19.41±12.05)k Pa,消融后1个月上述指标分别为(130.40±53.68)、(32.00±22.06)、(86.88±45.18)和(35.05±25.50)k Pa,各参数分别大于消融前的(50.85±30.61)、(15.30±8.78)、(30.50±11.56)和(7.37±4.26)k Pa,差异均有统计学意义(Z=118~561,P均<0.001,Wilcoxon符号秩和检验);消融后30 min、1 d及1个月同一参数杨氏模量值比较,差异均无统计学意义(χ2=3.088、0.821、5.202、3.786,P均>0.05,Friedman非参数秩和检验)。(2)SWE图像示消融灶长径为(3.0±0.6)cm,与二维超声[(2.9±0.5)cm]比较,差异无统计学意义(t=0.538,P>0.05);但小于超声造影的(3.4±0.4)cm,差异有统计学意义(t=3.644,P<0.01)。SWE图像示消融灶短径[(2.3±0.4)cm]及体积[(9.2±4.7)cm3]与二维超声[(2.4±0.5)cm、(9.3±5.0)cm3]及超声造影[(2.2±0.6)cm、(9.6±6.0)cm3]比较,三者间差异均无统计学意义(F=0.581、0.067,P均>0.05)。结论 SWE能够定量分析肝脏肿瘤射频消融前后的弹性变化,病灶消融后明显变硬,且硬度不随时间变化。此外,SWE对消融灶边界刻画清晰,且可近似估计消融范围,但是与实际消融范围仍存在一定偏差。
Objective To investigate the elastic changes before and after radiofrequency ablation of liver tumors and the ability of real-time shear wave elastography (SWE) to display the ablation range. Methods From February 2012 to December 2013, 57 patients with hepatic tumors undergoing RFA and complete ablation were treated in the First Affiliated Hospital of Sun Yat-sen University with a total of 57 lesions with an average diameter of (2.4 ± 1.1) cm. The SWE_max, SWE_min, SWE_mean and SWE_SD of the lesion were measured before and at 30 min, 1 d and 1 month after ablation respectively. . The Young’s modulus at different time points before and after liver tumor ablation were compared. Select the fusion ablation system with the Cool-tip radiofrequency ablation system for 12 min, and measure the long and short diameters on the two-dimensional sonogram and the SWE image one month after the ablation. According to the formula V = π × X × Y × Z / 6 (V is the volume, X is the long diameter, Y = Z is the short diameter) to calculate the volume of the lesion, compared with the day without contrast enhanced ultrasound contrast region. Results (1) SWE_max, SWE_min, SWE_mean and SWE_SD at 30 min after ablation were (121.80 ± 68.52), (30.36 ± 24.96), (66.92 ± 24.88) and (20.37 ± 12.97) kPa, respectively. (108.20 ± 46.99), (31.87 ± 18.08), (67.12 ± 23.53) and (19.41 ± 12.05) kPa respectively. The indexes at the first month after ablation were (130.40 ± 53.68), (32.00 ± 22.06) and (50.85 ± 30.61), (15.30 ± 8.78), (30.50 ± 11.56) and (7.37 ± 4.26) k Pa, respectively, all of the differences were statistically significant (P <0.001, Wilcoxon signed rank sum test). There was no significant difference in Young’s modulus between the same parameters at 30 min, 1 d and 1 month after ablation (χ2 = 3.088,0.821,5.202,3.786, P> 0.05, Friedman non-parametric rank sum test). (2) SWE images showed that the long axis of the lesion was (3.0 ± 0.6) cm, which was not significantly different from that of 2D ultrasound (2.9 ± 0.5 cm) (t = 0.538, P> 0.05) (3.4 ± 0.4) cm, the difference was statistically significant (t = 3.644, P <0.01). SWE images showed significant differences between the short axis of the lesion ([2.3 ± 0.4] cm] and the volume of [(9.2 ± 4.7) cm3] and the two-dimensional ultrasonography [(2.4 ± 0.5) cm, (9.3 ± 5.0) cm3] ± 0.6 cm, (9.6 ± 6.0) cm3]. There was no significant difference among the three groups (F = 0.581,0.067, P> 0.05). Conclusion SWE can quantitatively analyze the elastic changes before and after radiofrequency ablation of liver tumors. The lesions harden obviously after ablation, and the hardness does not change with time. In addition, the SWE depicts the boundary of the lesion clearly, and can approximate the ablation range, but there is still some deviation from the scope of the actual ablation.