两种场强磁共振IDEAL-IQ序列对质子密度脂肪分数和铁含量定量分析的初步对比研究

A preliminary quantitative comparative study of proton density fat fraction and iron content on two different strength of magnetic resonance with IDEAL-IQ sequence

目的:比较3.0 T和1.5 T MR最小二乘法估计和不对称回波迭代分解水和脂肪成像(IDEAL-IQ)序列质子密度脂肪分数(PDFF)和铁含量(R2 *)测量值的异同。 方法:于2019年12月选取佛山市第一人民医院健康志愿者20名[其中男性13名、女性7名,年龄(23.7±2.5)岁]并用不同脂肪含量的塑料试管模型进行前瞻性研究,分别在3.0 T(A组)和1.5 T(B组)2台MRI设备上应用IDEAL-IQ序列进行扫描。在自动生成的FatFrac图和R2 *图上自动勾画感兴趣区(ROI),分别测量模型、健康志愿者的肝脏和皮下脂肪的PDFF、R2 *值。符合正态分布的计量资料采用配对样本 t检验(方差齐)和Mann-Whitney U检验(方差不齐)进行比较。 结果:模型A1组和B1组PDFF的测量平均值分别为(20.59±14.39)%和(21.89±14.95)%,差异无统计学意义( Z=-1.550, P=0.121);A1组和B1组R2 *的测量平均值分别为(84.86±116.43)Hz和(43.61±54.59)Hz,差异有统计学意义( Z=-3.448, P=0.001)。健康志愿者3.0 T和1.5 T MRI肝脏、皮下脂肪PDFF测量平均值分别为(3.33±2.95)%和(4.39±2.80)%、(81.78±6.33)%和(81.54±5.53)%,差异均无统计学意义( Z=-1.867、 t=-0.301,均 P>0.05);A组肝脏、皮下脂肪的R2 *测量平均值为(52.42±12.22)Hz、(50.88±10.32)Hz,分别高于对应的B组[(32.73±5.62)Hz、(39.41±9.11)Hz],且差异均有统计学意义( Z=-3.920、 t=4.372,均 P<0.001)。 结论:基于IDEAL-IQ序列的3.0 T和1.5 T MR模型、健康志愿者肝脏和皮下脂肪的PDFF测量值的差异无统计学意义,但3.0 T MRI的PDFF测量值可能比1.5 T MRI更接近临床实际情况;2种场强获得的R2 *值的差异有统计学意义,其影响因素需进一步研究。

Objective Aimed to compare similarities and differences of the quantitative measurements of liver proton density fat fraction(PDFF)and iron content(R2*)between 3.0 T and 1.5 T MRI with iterative decomposition of water and fat with asymmetry and least squares estimation quantitative fat imaging(IDEAL-IQ)sequences.Methods Twenty healthy volunteers[13 males and 7 females,aged(23.7±2.5)years]and plastic test tube models with different fat contents were scanned with IDEAL-IQ sequence for prospective research on two MRI equipment of 3.0 T(group A)and 1.5 T(group B)in December 2019 in First People's Hospital of Foshan.The FatFrac images and R2*images automatically generated were used to draw the region of interests(ROIs)automatically.The PDFF and R2*values of the models and the liver and subcutaneous fat of the healthy volunteers were measured and compared between groups A and B.Measurement data that conformed to normal distribution were compared using paired sample t test(equal variances assumed)and Mann-Whitney U test(equal variances not assumed).Results The measured mean PDFF values of the model of groups A1 and B1 were(20.59±14.39)%and(21.89±14.95)%,respectively,with no significant difference(Z=−1.550,P=0.121).The measured mean R2*values of the model of groups A1 and B1 were(84.86±116.43)Hz and(43.61±54.59)Hz,respectively,with a statistically significant difference(Z=−3.448,P=0.001).No significant difference was found in the mean PDFF values of liver and subcutaneous fat of healthy volunteers[(3.33±2.95)%vs.(4.39±2.80)%,(81.78±6.33)Hz vs.(81.54±5.53)Hz)(Z=−1.867,t=−0.301;both P>0.05]with 3.0 T and 1.5 T MRI,respectively.The average R2*measured values of group A of the liver and subcutaneous fat of the healthy volunteers were higher than those of group B,with statistical significantly differences[(52.42±12.22)Hz vs.(32.73±5.62)Hz,(50.88±10.32)Hz vs.(39.41±9.11)Hz)(Z=−3.920,t=4.372;both P<0.001].Conclusions Results showed no significant differences in the PDFF values of models and the liver and subcutaneous fat of the volunteers measured between 3.0 T MR and 1.5 T MR based on IDEAL-IQ sequences,but the PDFF values of 3.0 T MRI may be closer to the clinical actual situation than that of 1.5 T MRI.The R2*values obtained based on 3.0 T MRI field strength were significantly different from that of 1.5 T MRI,and its influencing factors need to be further studied.