基于统计参数图的MRI海马结构体积测量

目的 研究经统计参数图(SPM)软件分割分析处理净灰质脑海马结构体积测量方法,并探讨这种基于体素的海马体积测量法在阿尔茨海默病(AD)诊断中的价值.方法 选取15例AD患者(AD组)和15名健康志愿者(正常对照组)行MR检查,利用SPM软件分割分析功能,将标准三维MR颅脑图像分离为独立的灰、白质和脑脊液图谱,在净灰质脑中分别勾画测量AD组和正常对照组左、右两侧海马结构体积,并与作为体积测量金标准的传统手工描绘ROI测量法比较,同时记录两种测量方法在每例海马边界描绘及体积计算的平均用时.采用独立样本配对t检验进行两种测量方法所得体积、平均用时的均数比较.另外,由7名影像医师对同一例正常对照者采用上述两种方法分别测量其左侧海马结构体积,采用变异系数比较两种测量方法所得数据的频数分布及离散程度.结果 (1)经SPM处理测量法测定AD组的左、右两侧海马平均体积分别为(1.88±0.07)和(1.93±0.08)cm~3,对照组分别为(2.99±0.07)和(3.02±0.06)cm~3;ROI测量法测定AD组分别为(1.87±0.06)和(1.91±0.09)cm~3,对照组则为(2.97±0.08)和(3.00±0.05)cm~3.经SPM处理测量法在AD组及正常对照组测定结果与传统ROI测量法之间差异均无统计学意义(t值分别为1.500、1.617、1.095、1.889,P值均>0.05).每例描绘边界、计算体积平均用时经SPM处理测量法为(38.1±2.0)min,ROI测量法为(55.4±2.4)min,两者之间差异有统计学意义(t=-25.918,P<0.01).(2)7名医师对同一例正常对照者采用经SPM处理测量法和ROI测量法测得左侧海马平均体积分别为(2.86±0.20)和(2.76±0.52)cm~3;变异系数分别是7%、19%,两种方法测定海马体积的频数分布存在差别.结论 利用SPM软件的图像分割分析功能,使海马结构在净灰质脑图谱中的边界划定变得简单便捷,进而提高测定数据精确性和重复能力;较短的测量计算用时使MRI海马结构体积测量在相关神经精神疾病诊断中的应用成为可能.

MRI volumetric measurement of hippocampal formation based on statistic parametric mapping

Objective To study MRI volumetric measurement of hippocampal formation using statistic parametric mapping(SPM) software and to discuss the value of the method applied to Alzheimer's disease (AD).Methods The SPM software was used to divide the three-dimensional MRI brain image into gray matter, white matter and CSF separately.The bilateral hippocampal formations in both AD group and normal control group were delineated and the volumes were measured.The SPM method was compared with conventional method based on region of interest (ROI), which was the gold standard of volume measurement The time used in measuring the volume by these two methods were respectively recorded and compared by two independent samples' t test.Moreover, 7 physicians measured the left hippocampal formation of one same control with both of the two methods.The frequency distribution and dispersion of data acquired with the two methods were evaluated using standard deviation coefficient Results (1)The volume of the bilateral hippocampal formations with SPM method was (1.88±0.07) cm~3 and (1.93±0.08) cm~3 respectively in the AD group, while was (2.99 ±0.07) cm~3 and (3.02 ±0.06) cm~3 in the control group .The volume of bilateral hippocampal formations measured by ROI method was (1.87 ±0.06) cm~3 and (1.91 ±0.09) cm~3 in the AD group, while was (2.97 ±0.08)cm~3 and (3.00 ±0.05) cm~3 in the control group.There was no significant difference between SPM method and conventional ROI method in the AD group and the control group(t=1.500, 1.617, 1.095, 1.889,P> 0.05) .However, the time used for delineation and volume measurement was significantly different.The time used in SPM measurement was (38.1 ±2.0) min, while that in ROI measurement was (55.4 ±2.4) min (t=-25.918, P<0.01).(2)The average volumes of the left hippocampal formation with the two methods measured by the 7 physicians were (2.86±0.20) and (2.76±0.52) cm~3 respectively.The frequency distribution of hippocampal formation volume measured by SPM method and ROI method was different.The CV_(SPM) was 7% and the CV_(ROI) was 19%.Conclusions The borders of hippocampus formation in brain gray matter could be conveniently delineated by SPM software.The accuracy and repetition of measurement was improved by SPM method.The shorter time used in measurement made it possible for MRI volumetric measurement of hippocampal formation to be applied in assessment of relevant neuropsychiatric diseases.