Shan Yan, Zeng Meng-su, Liu Kai, Miao Xi-Yin, Lin Jiang, Fu Cai xia, Xu Peng-ju
From the *Department of Radiology, Zhongshan Hospital, Fudan University, Shanghai Institute of Medical Imaging, Shanghai, China, and †MR Collaboration NEA, Siemens Ltd. China, Shanghai, China.
J Comput Assist Tomogr. 2015 Sep-Oct;39(5):709-15. doi: 10.1097/RCT.0000000000000278.
To evaluate the effect on image quality and intravoxel incoherent motion (IVIM) parameters of small hepatocellular carcinoma (HCC) from choice of either free-breathing (FB) or navigator-triggered (NT) diffusion-weighted (DW) imaging.
Thirty patients with 37 small HCCs underwent IVIM DW imaging using 12 b values (0-800 s/mm) with 2 sequences: NT, FB. A biexponential analysis with the Bayesian method yielded true diffusion coefficient (D), pseudodiffusion coefficient (D*), and perfusion fraction (f) in small HCCs and liver parenchyma. Apparent diffusion coefficient (ADC) was also calculated. The acquisition time and image quality scores were assessed for 2 sequences. Independent sample t test was used to compare image quality, signal intensity ratio, IVIM parameters, and ADC values between the 2 sequences; reproducibility of IVIM parameters, and ADC values between 2 sequences was assessed with the Bland-Altman method (BA-LA).
Image quality with NT sequence was superior to that with FB acquisition (P = 0.02). The mean acquisition time for FB scheme was shorter than that of NT sequence (6 minutes 14 seconds vs 10 minutes 21 seconds ± 10 seconds P < 0.01). The signal intensity ratio of small HCCs did not vary significantly between the 2 sequences. The ADC and IVIM parameters from the 2 sequences show no significant difference. Reproducibility of Dand f parameters in small HCC was poor (BA-LA: 95% confidence interval, -180.8% to 189.2% for D and -133.8% to 174.9% for f). A moderate reproducibility of D and ADC parameters was observed (BA-LA: 95% confidence interval, -83.5% to 76.8% for D and -74.4% to 88.2% for ADC) between the 2 sequences.
The NT DW imaging technique offers no advantage in IVIM parameters measurements of small HCC except better image quality, whereas FB technique offers greater confidence in fitted diffusion parameters for matched acquisition periods.
评估自由呼吸（FB）或导航触发（NT）扩散加权（DW）成像对小肝细胞癌（HCC）图像质量和体素内不相干运动（IVIM）参数的影响。
30例患有37个小HCC的患者使用12个b值（0 - 800 s/mm²）的2种序列进行IVIM DW成像：NT和FB。采用贝叶斯方法进行双指数分析，得出小HCC和肝实质中的真实扩散系数（D）、伪扩散系数（D*）和灌注分数（f）。还计算了表观扩散系数（ADC）。评估2种序列的采集时间和图像质量评分。采用独立样本t检验比较2种序列之间的图像质量、信号强度比、IVIM参数和ADC值；采用Bland - Altman方法（BA - LA）评估2种序列之间IVIM参数和ADC值的可重复性。
NT序列的图像质量优于FB采集（P = ⁰.⁰²）。FB方案的平均采集时间短于NT序列（6分14秒对10分21秒±10秒，P < ⁰.⁰¹）。2种序列之间小HCC的信号强度比无显著差异。2种序列的ADC和IVIM参数无显著差异。小HCC中D和f参数的可重复性较差（BA - LA：95%置信区间，D为 - 180.8%至189.2%，f为 - 133.8%至174.9%）。2种序列之间观察到D和ADC参数具有中等可重复性（BA - LA：95%置信区间，D为 - 83.5%至76.8%，ADC为 - 74.4%至88.2%）。
NT DW成像技术在小HCC的IVIM参数测量中除图像质量较好外无优势，而FB技术在匹配采集时间的拟合扩散参数方面具有更高的可信度。
