采用磁敏感加权成像技术研究年龄相关的脑铁沉积现象

Age-related deposition of brain iron in normal adults： an in vivo susceptibility weighted imaging study

目的采用磁敏感加权成像技术，探讨正常人大脑不同区域的铁含量随年龄变化的规律。方法78名成年健康志愿者按照年龄分为青年组（≤35岁）27名、中年组（36～55岁）35名和老年组（≥56岁）16名，所有受试者均进行磁敏感加权成像，在校正相位图上分别测量苍白球、壳核、尾状核、黑质、红核、丘脑和额叶白质的相位值。30岁以上受试者各脑区的平均相位值和文献报道的脑铁实际含量进行Pearson相关分析，采用单因素方差分析比较各脑区不同年龄组之间的校正相位值差异，用线性回归分析法进一步研究由方差分析法所揭示的年龄相关的铁含量变化，并计算其变化率。结果各脑区的平均相位值和文献报道的脑铁实际含量间存在负相关性（r=-0．796，P=0．032），铁含量多的脑区相位值的负值大。青年组、中年组和老年组壳核相位值的中位数分别是-0．0185、-0．0362和-0．0566，额叶白质相位值中位数分别是0．0034、-0．0031和-0．0021，各年龄组间的差异具有统计学意义（F值分别为20．115、3．536，P值分别〈0．01、〈0．05）。线性回归分析表明，壳核、红核和额叶白质的铁含量随着年龄的增加而增加（回归系数分别为-0．001、-0．001、〈-0．001，P值均〈0．05），苍白球、尾状核、黑质和丘脑的铁含量不随年龄而变化。结论研究结果证明并拓展了对年龄相关的脑铁沉积现象的认识，为全面、准确认识疾病相关的脑铁异常沉积现象提供了必要的基础。

Objective The purpose of this study was to investigate the effect of age on the iron concentration of the human brain. Methods The brain iron level was evaluated in vivo in 78 healthy adult volunteers using a noninvasive magnetic resonance method termed susceptibility weighted imaging. The subjects were divided into three groups due to different ages ： young （ 22-35 years old, n = 27 ）, middleaged （36-55 years old, n =35） , and aged （56-78 years old, n = 16）. The phase values were measured on the corrected phase images in the globus pallidus, putamen, caudate, substantia nigra, red nucleus, thalamus and frontal white matter. The phase values of those regions measured from the subjects over than 30 years old were correlated with published values of brain iron concentration in normal adults to check the validity of the data. Then, the phase values of the three groups were tested for significant age-related differences using one-way ANOVA, followed by post hoc testing using least significant difference （LSD） procedure. Regression analysis was used to further examine age-related effects revealed by group comparisons, and to estimate the rates of age-related changes. Results A strong negative correlation was found between the phase values and the published values of the brain iron concentration （ r = - 0. 796, P = 0. 032）, which indicated that the higher the iron deposition level, the greater the negative phase values. In the putamen （F = 20. 115,P 〈 0.01） and frontal white matter （F = 3.536,P = 0.034） , significant differences were detected in the phase values of the three age groups. Linear regression analysis showed that phase values of the putamen, frontal white matter, and red nucleus decreased with age （The regression coefficients were -0. 001, - 0. 001, and 〈 - 0. 001 respectively, and the P value were all 〈 0. 05 ）, which indicated that the iron concentration of those brain structures increased with age. No significant agerelated changes of the iron concentration were found in the globus pallidus, eaudate, substantia nigra, and thalamus. Conclusions These findings extended our knowledge of the patterns of the brain ironaccumulation in normal aging. Such information is necessary to understand disease-related changes that involve the brain iron deposition.