Häcker Axel, Risse F, Peters Kristina, Fink Christian, Weiss Christel, Huber Peter E, Alken Peter, Michel Maurice Stephan, Jenne Jürgen W
Department of Urology, University Hospital Mannheim, Ruprecht-Karls University of Heidelberg, Heidelberg, Germany.
J Endourol. 2006 May;20(5):312-7. doi: 10.1089/end.2006.20.312.
Radiofrequency ablation (RFA) is an attractive minimally invasive treatment option for small renal masses. The purpose of this study was to investigate the morphologic imaging appearance of RF lesions immediately after the ablation of kidney tissue using standard clinical MR sequences, as well as to investigate the correlation between MR and gross lesion size.
Ablations were performed 17 times in a standardized model of ex-vivo perfused porcine kidneys using a resistance-controlled RF device (250 W, 470 kHz) and a nonexpandable bipolar applicator inserted into the center of healthy renal parenchyma. The RF current was applied for 9 minutes at 20 W. Imaging was performed after ablation using standard clinical MR sequences: morphologic T(1)/T(2)- weighted images and an isotropic post-contrast T(1) high-resolution measurement (VIBE). Maximum lesion diameters were measured in three directions and were compared with the measurements of the gross lesions. Histologic (hematoxylin + eosin and nicotinamide adenine dinucleotide staining) and statistical analyses were performed.
The gross pathologic examination showed a firm, white-yellow ablation zone sharply demarcated from the untreated tissue. The histologic examination confirmed cellular viability outside but not in the treatment zone. The RF lesions were hyperintense on T(1)-weighted images and hypointense on T(2)-weighted images. The lesion size measured in the VIBE images correlated best with the macroscopic lesion size (N = 16).
Morphologic MR T(1) and T(2) sequences of RF lesions immediately after ablation produce reliable and consistent imaging characteristics. The post-contrast, high-resolution sequence (VIBE) enables the extent of the lesion to be determined accurately. The potential uses of this imaging strategy in clinical practise warrant further investigation on human renal-cell carcinoma.
射频消融（RFA）是一种针对小肾肿块颇具吸引力的微创治疗选择。本研究旨在利用标准临床磁共振序列，探究肾脏组织消融后即刻射频消融病灶的形态学影像表现，并研究磁共振影像与大体病灶大小之间的相关性。
使用电阻控制射频设备（250W，470kHz）及插入健康肾实质中心的不可扩张双极电极，在离体灌注猪肾的标准化模型中进行17次消融。以20W施加射频电流9分钟。消融后使用标准临床磁共振序列进行成像：形态学T1/T2加权图像及各向同性对比增强后T1高分辨率测量（容积内插体部检查序列）。在三个方向测量最大病灶直径，并与大体病灶测量值进行比较。进行组织学（苏木精+伊红染色及烟酰胺腺嘌呤二核苷酸染色）和统计学分析。
大体病理检查显示，有一个坚实的黄白色消融区，与未处理组织界限清晰。组织学检查证实治疗区外细胞存活，但治疗区内细胞无存活。射频消融病灶在T1加权图像上呈高信号，在T加权图像上呈低信号。容积内插体部检查序列图像上测量的病灶大小与大体病灶大小相关性最佳（N=16）。
消融后即刻射频消融病灶的形态学磁共振T1和T2序列产生可靠且一致的影像特征。对比增强后高分辨率序列（容积内插体部检查序列）能够准确确定病灶范围。这种成像策略在临床实践中的潜在用途值得在人类肾细胞癌上进一步研究。
