不同翻转角和延迟时间对Gd-BOPTA增强肝胆期肝脏和胆道系统图像质量的影响

Effects of different flip angles and delay times on image quality of liver and biliary system in hepatobiliary phase images of Gd-BOPTA-enhanced magnetic resonance images

目的探讨不同翻转角(flip angle,FA)和延迟时间对钆贝葡胺(gadobenate dimeglumine,Gd-BOPTA)增强MRI肝胆期(hepatobiliary phase,HBP)肝脏和胆道系统图像质量的影响。材料与方法回顾性分析57例肝脏Gd-BOPTA增强3.0 T MRI扫描患者病例。所有患者在注射对比剂后延迟60 min及120 min分别行FA为10°、15°、20°、25°、30°HBP成像,FA与延迟时间任意两两组合为10组。测量各组肝脏及胆总管的信号强度(signal intensity,SI)和竖脊肌的SI及标准差(standard deviation,SD),计算信噪比(signaltonoiseratio,SNR)、对比噪声比(contrast to noise ratio,CNR)、胆道-竖脊肌比值(bile to paravertebral muscle ratio,BMR);采用5分法对胆道的可视性进行主观评价。分别使用组内相关系数(intra-class correlation coefficient,ICC)和加权Kappa检验评估两名观察者间所测数据及主观评分的一致性;采用非参数Friedman检验进行各组SNR、CNR、BMR及主观评分多组间比较,采用LSD-t检验进行各组SNR、CNR、BMR及主观评分的事后组内两两比较,对结果进行Bonferroni校正,根据统计结果选择FA与延迟时间的最优组合。结果两名观察者除120min/FA15°组的SNR肝测量值的一致性为尚可外(ICC值=0.75),余各组数据测量及主观评分的一致性均良好(ICC值均>0.75,Kappa值均>0.75)。各参数在延迟120 min组均高于延迟60 min组;120min/FA30°组的SNR_(肝脏)最高[63.91(49.44,77.15)],与60min/FA10°组和120min/FA10°组的组间差异具有统计学意义(P<0.05);120min/FA30°组的CNR_(肝脏)最高[44.21(31.58,53.64)],与60min/FA10°组、60min/FA15°组、60min/FA30°组和120min/FA10°组的组间差异具有统计学意义(P<0.05);120min/FA30°组的SNR_(胆总管)最高[305.27(193.97,377.53)],与60min/FA10°组、60min/FA15°组、60min/FA20°组、60min/FA25°组、120min/FA10°组和120min/FA15°组的组间差异具有统计学意义(P<0.05);120min/FA30°组的CNR_(胆总管)最高[278.66(180.80,357.20)],与60min/FA10°组、60min/FA15°组、60min/FA20°组、60min/FA25°组、60min/FA30°组、120min/FA10°组、120min/FA15°组的组间差异具有统计学意义(P<0.05);120min/FA30°组的BMR最高[14.75(11.55,17.87)],与60min/FA10°组、60min/FA15°组、60min/FA20°组、60min/FA25°组、120min/FA10°组、120min/FA15°组的组间差异具有统计学意义(P<0.05)。主观评分结果显示,60min/FA10°组胆道的可视性最差,显著低于60min/FA20°组、60min/FA25°组、60min/FA30°组、120min/FA15°组、120min/FA20°组、120min/FA25°组、120min/FA30°组(P<0.05)。结论通过比较不同FA与延迟时间的组合,120min/FA30°组对Gd-BOPTA增强HBP肝脏及胆道图像质量显示最佳,增大FA与延长延迟时间可以明显提高图像质量。

Objective:To investigate the effects of different flip angles(FA)and delay times on the image quality of liver and biliary system in hepatobiliary phase(HBP)images of gadobenate dimeglumine(Gd-BOPTA)-enhanced magnetic resonance images(MRI).Materials and Methods:Fifty-seven patients with abdominal discomfort,who had undergone a 3.0 T upper abdominal Gd-BOPTA-enhanced MRI scan at our hospital,were retrospectively included.HBP imaging was conducted with FA of 10°,15°,20°,25°,and 30°,at delays of 60 minutes and 120 minutes post-contrast agent injection.These combinations of FA and delay time were categorized into 10 groups.Signal intensity(SI)of the liver and common bile duct,SI and standard deviation(SD)of the erector spinae were measured.Additionally,signal-to-noise ratio(SNR),contrast-to-noise ratio(CNR)and bile to paravertebral muscle ratio(BMR)were calculated.The visibility of the biliary tract in the images was evaluated using the 5-point method.Intra-group correlation coefficient(ICC)and the weighted Kappa test were employed to assess the consistency of the measured data and subjective scores between the two observers.The nonparametric Friedman test was utilized to compare the SNR,CNR,BMR,and subjective scores among images with different combinations of delay time and FA.LSD-t test was used to compare SNR,CNR,BMR and subjective score in each group,and Bonferroni correction was carried out on the results.The optimal combination of FA and delay time was determined based on the statistical results.Results:The data and subjective from both observers exhibit strong agreement(ICC values are all>0.75,Kappa values are all>0.75)except the SNR_(liver) for the 120min/FA15°group(ICC=0.75).Across all parameters values at the group of 120-minute delay time are consistently higher than the group of 60-minute delay time.The SNR of the liver in the 120min/FA30°group ecorded the highest value[63.91(49.44,77.15)],which was significantly better than 60min/FA10°and 120min/FA10°groups(P<0.05).The CNR_(liver) in the 120min/FA30°group ecorded the highest value[44.21(31.58,53.64)],demonstrating a significant difference compared to the 60min/FA10°,60min/FA15°,60min/FA30°and 120min/FA10°groups(P<0.05).The SNR of the bile duct in the 120min/FA30°group ecorded the highest value[305.27(193.97,377.53)],which was significantly better than 60min/FA10°,60min/FA15°,60min/FA20°,60min/FA25°,120min/FA10°,and 120min/FA15°groups(P<0.05).The CNR_(common bile duct) in the 120min/FA30°group ecorded the highest value[278.66(180.80,357.20)],which was significantly different from the 60min/FA10°,60min/FA15°,60min/FA20°,60min/FA25°,60min/FA30°,120min/FA10°,and 120min/FA15°groups(P<0.05).The BMR in the 120min/FA30°group ecorded the highest value[14.75(11.55,17.87)],which was significantly different from the 60min/FA10°,60min/FA15°,60min/FA20°,60min/FA25°,120min/FA10°,and 120min/FA15°groups(P<0.05).According to the subjective scoring results,the visibility of biliary tract at 60min/FA10°was the worst,which was obviously lower than 60min/FA20°,60min/FA25°,60min/FA30°,120min/FA15°,120min/FA20°,120min/FA25°,and 120min/FA30°groups(P<0.05).Conclusions:By evaluating various combinations of different FA and delay times,it is evident that the 120min/FA30°group exhibits the highest image quality for enhanced liver and biliary tract in HBP of Gd-BOPTA-enhanced MRI.Increasing the FA and extending the delay time notably enhance image quality.