钆剂对MR IDEAL-IQ骨髓脂肪定量影响的实验研究

Effect of gadolinium on vertebral fat fraction content using IDEAL-IQ technique

目的探讨3.0 T MR IDEAL-IQ序列定量评估的兔腰椎骨髓脂肪分数（FF）是否受到钆类对比剂增强扫描的影响。材料与方法对8只健康新西兰大白兔在静脉注射钆贝葡胺前及注射后各时间节点5 min、30 min分别行腰椎IDEAL-IQ序列扫描,将ROI分别置于第37腰椎,通过脂肪比像、R2*弛豫率像对兴趣区内的脂肪分数（FF）、R2*进行定量测量。取37腰椎体行HE染色和普鲁士蓝染色,计算骨髓脂肪含量（FCHIS）及观察骨髓铁沉积。对注射钆剂前后各时间点的脂肪分数FF(FF0 min、FF5 min、FF30 min)及R2*(R2*0 min、R2*5 min、R2*30 min)值分别采用单变量重复测量方差分析。对注射钆剂前脂肪分数(FF0 min)与HE染色计算的脂肪含量（FCHIS）进行Pearson相关分析。采用Bland-Altman分析对注射钆剂前(FF0 min)与注射钆剂后各时间点(FF5 min、FF30 min)分别进行一致性检验。结果注射钆对比剂前IDEAL-IQ骨髓脂肪分数值(FF0 min)与注射钆对比剂5 min后骨髓脂肪分数值(FF5 min)、30 min后骨髓脂肪分数值(FF30 min)无明显统计学差异（F=3.118,P>0.05,组间比较结果分别为P=0.835、0.916和0.754）。HE染色计算的脂肪含量（FCHIS）与注射钆剂前FF0 min（r=0.813）存在高度正相关性（P<0.05）。注射钆剂前FF0 min与注射钆剂5 min后FF5 min（0.90,1.10）及注射钆剂30 min后FF30 min（0.94,1.0 7）均具有良好的一致性（测量值比率9 5%置信区间）。注射钆剂前R2*0 min（121.64）、注射5 min后R2*5 min（125.70）（P=0.046）,及注射30 min后R2*30 min（125.21）（P=0.024）,差异均有统计学意义。结论在静脉注射钆剂引起的R2*值增高的情况下,IDEAL-IQ定量椎体骨髓脂肪分数的准确度高,且仍维持较高的稳定性和一致性。

Objective: This study evaluates the robustness of a magnetic resonance(MR) fat quantification method to changes in R2* caused by an intravenous infusion of gadolinium. Materials and Methods: The R2* and fat fraction content(FF) were measured in vertebral marrow in eight New Zealand white rabbits using an investigational sequence(IDEAL IQ) provided by the MR scanner vendor. Measurements were made once before and twice after Gd-BOPTA infusion(5 min, 30 min). Then HE stain was performed for calculating vertebral fat content(FC_(HIS)), Prussian blue stain was performed for showing iron in vertebral. Results: Vertebral marrow FF measurements revealed no significant systematic bias between the three measurements(P>0.05 for all). Good agreement(95% confidence interval) of FF measurements were demonstrated between FF_(0 min) and FF_(5 min)(0.90, 1.10) and FF_(0 min) and FF_(30 min)(0.94, 1.07). A significant positive correlation is found between FF_(0 min) and FCHIS(r=0.813, P<0.05). R2* increased after administration of gadolinium. Conclusion: Although under the impact of an increased R2* in vertebral marrow post-contrast, the investigational sequence can still obtain accurate and stable fat fraction content. the IDEAL IQ method of fat quantification is robust to changes in R2*.