衰老进程中脑氧代谢及灌注参数的变化规律研究

Trajectories of cerebral oxygen metabolism and cerebral perfusion changes in aging

目的:利用基于时间演变聚类分析(CAT)的定量磁化率成像(QSM)和定量血氧水平依赖成像(qBOLD)的脑氧代谢成像新技术“CAT-QQ”探讨健康人群衰老进程中脑氧代谢率(CMRO_(2))、氧摄取分数(OEF)和脑血流量(CBF)的变化规律。方法:前瞻性收集108例20~70岁健康志愿者,其中男42例,女66例。利用三维增强梯度回波T_(2)^(*)加权血管成像(ESWAN)及三维伪连续动脉自旋标记成像(3D-pCASL)重建静息状态下全脑体素水平CMRO_(2)、OEF及CBF参数图,并提取个体空间全脑灰质、全脑白质、不同脑叶和深部灰质核团的各参数值。分析比较各参数值在灰质与白质、男性与女性之间的差异,以及各参数值与年龄的相关性。结果:108例志愿者全脑灰质的CMRO_(2)和CBF高于白质,OEF低于白质(P<0.05)。女性全脑灰质与白质的CMRO_(2)及CBF均高于男性(P<0.05),OEF在不同性别间的差异无统计学意义。控制性别因素后,灰质CMRO_(2)和CBF与年龄呈负相关(P<0.05),灰质OEF及白质各参数值与年龄无显著相关性。岛叶的CBF、壳核的CMRO_(2)以及尾状核的CMRO_(2)、OEF和CBF在不同年龄段之间的差异有统计学意义(P<0.05)。结论:健康人群衰老进程中大脑CMRO_(2)及CBF逐渐减低且表现出性别差异,OEF则相对稳定。CAT-QQ脑氧代谢成像技术联合3D-pCASL可以对健康人群静息状态下的脑氧代谢及脑血流灌注进行精准测量,有望在临床疾病中展开应用以进一步探究脑氧代谢相关参数的病理变化机制。

Objective:To investigate the trajectories of resting-state cerebral metabolic rate of oxygen(CMRO_(2)),oxygen extraction fraction(OEF),and cerebral blood flow(CBF)in aging with cluster analysis of time evolution(CAT)for quantitative susceptibility mapping(QSM)and quantitative blood oxygen level dependent(qBOLD)imaging-based OEF and CMRO_(2) mapping(CAT-QQ).Methods:One hundred and eight healthy subjects were prospectively collected(age:20~70 years;42 males and 66 females).Enhanced gradient echo T_(2) star weighted angiography(ESWAN)and three-dimensional pseudo-continuous arterial spin labeling(3D-pCASL)were used to reconstruct resting-state CMRO_(2),OEF,and CBF maps.The difference of CMRO_(2),OEF,and CBF between global gray matter(GGM)and global white matter(GWM)and between genders were compared.Correlation of the three parameters from different lobes in GGM and GWM and deep gray matter regions with age were also analyzed.Results:CMRO_(2) and CBF were higher while OEF was lower in GGM compared to those in GWM(P<0.05).Females showed higher CMRO_(2) and CBF in the GGM and GWM than males(P<0.05).The OEF between genders was no significant difference.After adjusting the effect of gender as a confounding factor,there were negative correlations of the CMRO_(2) and CBF in the GGM with age(P<0.05),while no significant correlations were found between OEF in the GGM and age or between three parameters in the GWM and age.CBF in the insula,CMRO_(2) in the putamen and three parameters in the caudate were significantly different between age groups(P<0.05).Conclusion:CMRO_(2) and CBF gradually decrease with normal aging while OEF is relatively stable.CAT-QQ together with 3D-pCASL are of feasibility for accurate quantification of cerebral oxygen metabolism and cerebral perfusion,which may be useful for understanding pathological mechanism for diseases involving metabolism and perfusion impairment.