3.0T磁共振T1反转角对钆塞酸二钠增强MR肝胆特异期肝实质信号强度影响的研究

The research on the effects of flip angle to signal intensity of the liver parenchyma in liver specific period of Gd-EOB-DTPA MRC

目的:通过比较不同反转角(FA)在钆塞酸二钠(Gd-EOB-DTPA)增强MR肝胆特异期时肝实质与竖脊肌对比度,确定合理肝胆特异期延迟时间及扫描序列参数。方法:对15例肝脏结节性病变患者在Gd-EOB-DTPA磁共振肝胆造影术(MRC)中肝胆特异期注药后5 min、10 min、15min和20 min分别行FA值为9 °、25 °、30°和35°的扫描成像。测量FA值的每组图像肝实质、竖脊肌对比噪声比(CNR);并对图像的伪影、均匀度、对比度以及整体质量行双盲主观评分,采用两独立样本比较FA 25 °15 min与FA 9 °20 min的肝实质-竖脊肌CNR。结果:同一时间点下FA值为9 °、25 °、30 °和35°时,肝实质-竖脊肌CNR有显著差异(F=17.76,P<0.05);主观评分结果伪影和均匀度均无差异(x^2=20.87,x^2=29.63;P>0.05);肝实质-竖脊肌CNR和图像整体质量有差异(x^2=46.76,x^2=43.23;P<0.05)。FA值为25 °注药后15 min与FA值为9 °注药后20 min的肝实质-竖脊肌CNR之间无差异(t=1.89,P>0.05)。结论:在3.0T Gd-EOB-DTPA MRC肝胆特异期时,加大FA值能有效地提高肝实质信号强度,注药后15 min采用FA值25 °可缩短肝胆特异期延迟时间。

Objective： To study the effects of flip angle（FA） to signal intensity of the liver parenchyma in liver specific period of Gd-EOB-DTPA MRC, and to determine reasonable delay time of liver specific period and scan sequence parameters. Methods： 15 cases of patients took CT scan with FA value 9 degrees, 25 degrees, 30 degrees and 35 degrees in liver specific period of Gd-EOB-DTPA MRC after 5min,10 min,15min and 20 min. The resulting image of each FA value sum up as a group. The liver parenchyma, the erector spinae and the background signal intensity of each group were measured respectively. And the signal to noise ratio（SNR） and the contrast to noise ratio（CNR） of liver parenchyma, erector spinae about each group were calculated and analyzed by One-Way ANOVA among different groups. The subjective parameters including image artifacts, image uniformity, contrast ratio and whole image quality were analyzed by Kruskal-Wallis H test. According to the subjective evaluation results, we compared the CNR of liver parenchyma-erector spinae at 15 min FA（25degrees） and 20 min FA（9 degrees） which were calculated and analyzed by t test. There was significant difference（P〈0.05）. Results： For flip angle 9 degrees, 25 degrees, 30 degrees and 35 degrees, the SNR of liver parenchyma-erector were 150.33±9.06, 204.93±6.99, 210.76±11.87 and 219.98±8.31. There was significant difference（F=17.76, P=0.03）. The subjective scores of image artifacts were 4.90±0.31, 4.70±0.56, 4.80±0.73 and 4.80±0.69（x^2=20.87, P=0.07）. The image uniformity were 4.70±0.89, 4.60±0.41, 4.80±0.93 and 4.60±0.38（x^2=29.63, P=0.06）. The liver parenchyma-erector spinae contrast were 1.30±0.35, 2.60±0.44, 4.10±0.38 and 4.90±0.90（x^2=46.76, P=0.03）. The whole image quality were 1.80±0.90, 2.40±0.94, 4.90±0.29 and 5.00±0.00（x^2=43.23, P=0.02）. Conclusion： Increased FA can effectively improve the liver parenchyma signal intensity. After 15 min＇s injection, the 25 degree can shorten the delay time of the liver and gallbladder specific period.