自由呼吸扩散加权成像与屏气扩散加权成像在肾脏病变方面的对比研究

Free-Breathing Versus Breath-Hold Diffusion-Weighted MRI of Renal Lesions:Comparison of Image Quality and Apparent Diffusion Coefficient Values

目的比较肾脏病变自由呼吸扩散加权成像与屏气扩散加权成像在表观弥散系数(ADC)值及图像质量方面的异同。资料与方法本研究纳入41例经病理结果或临床随访证实患有肾脏疾病的患者。所有患者均在1.5T磁共振扫描仪上进行自由呼吸扩散加权成像及屏气扩散加权成像。两种成像序列方面的参数除激励次数(NEX)之外均相同。两组图像的信噪比(SNR)、对比噪声比(CNR)及相对病变对比度的比较通过Wilcoxon检验进行统计学分析。两组肾实质ADC值及病变ADC值的一致性通过Pearson相关分析及信度分析方法进行分析。结果自由呼吸扩散加权成像图像的SNR及CNR都显著高于屏气扩散加权成像图像(P<0.01)。但两组图像的病变相对对比度差异无统计学意义(P=0.459)。两种扩散加权成像方法计算出的肾脏病变ADC值表现出良好的一致性(Pearson相关系数为0.888;信度分析中校正的a系数为0.949,组内相关系数为0.901)。两组肾实质ADC值之间亦表现出良好的一致性(Pearson相关系数为0.871;信度分析中校正的a系数为0.931,组内相关系数为0.931)。结论自由呼吸扩散加权成像适用于肾脏病变的评价,特别适用于屏气困难的患者,而且ADC值与屏气扩散加权成像一致性良好。

Purpose To compare free-breathing and breath-hold diffusion-weighted MRI of renal lesions and to assess the coincidence of the apparent diffusion coefficient （ADC） values between the two sequences. Materials and Methods 41 patients were enrolled into this study with 41 renal masses （median diameter, 4.0cm） confirmed by pathology results or follow-up. All patients underwent both free-breathing and breath-hold diffusion-weighted MR imaging （DWI） at a 1.5 T MR system. Both sequences had identical imaging parameters except for signal averages, which were 8 in free-breathing and 2 in breath-hold sequences. Signal-to-noise ratio （SNR） of the kidney, contrast-to-noise ratio （CNR）, and relative contrast ratio of the lesions were measured in each DWI sequence and were statistically compared using the Wilcoxon test. The coincidence of ADC values of uninvolved renal parenchyma and renal lesions of the two sequences were compared using Pearson’s coefficient and reliability analysis scale. Results The SNR of the uninvolved renal parenchyma and the CNR of the renal lesions were both significantly better on free-breathing DWI than on breath-hold DWI （P0.01）. However, the relative contrast ratio did not show significant difference between these two sequences （P=0.459）. The ADC values of renal lesions measured by the two techniques showed good agreement （Pearson’s correlate coefficient, 0.888; standardized item α on the reliability analysis scale, 0.949; and intraclass correlation coefficient, 0.901） and so did ADC values of the uninvolved renal parenchyma （Pearson’s correlate coefficient, 0.871; standardized item α on the reliability analysis scale, 0.931; and intraclass correlation coefficient, 0.931）. Conclusion Free-breathing DWI can be an appropriate sequence for evaluation of renal lesions without any compromise in the calculated ADC values, especially for patients with breath-hold difficulty.