Brander Antti, Kataja Anneli, Saastamoinen Antti, Ryymin Pertti, Huhtala Heini, Ohman Juha, Soimakallio Seppo, Dastidar Prasun
Department of Radiology, Tampere University Hospital, Finland.
Acta Radiol. 2010 Sep;51(7):800-7. doi: 10.3109/02841851.2010.495351.
Diffusion tensor imaging (DTI) is an increasingly used method for investigation of brain white matter integrity in both research and clinical applications. Familiarity with normal variation of fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values and measurement reproducibility is essential when DTI measurements are interpreted in clinical patients.
To establish normal values for FA and ADC in a healthy adult population at 1.5 T and 3 T MRI based on region of interest (ROI) analysis, and to study the inter- and intra-observer reproducibility of the measurements.
Forty healthy volunteers (26 women, 14 men, mean age 38.3, SD 11.6 years) underwent conventional MRI and DTI of the brain, 30 with 3 T and 10 with 1.5 T clinical scanners. ROI-based measurements for FA and ADC values were performed in five different anatomic locations of each hemisphere and in three locations within the corpus callosum. Mean values for FA and ADC for each region were calculated. Inter-observer variation of ROI measurements was evaluated by comparing the results of the two observers, intra-observer variation by repeated measurement of 10 subjects by both observers.
The FA values varied considerably between different regions. The highest values were found in the genu and splenium of the corpus callosum and the lowest in the corona radiata, respectively. In general, ADC values showed less variation; the highest values were found in the body of the corpus callosum and the lowest in the corona radiata. The reproducibility of both inter- and intra-observer measurements also varied regionally. The highest agreement was found for the corpus callosum and the lowest for the corona radiata and centrum semiovale.
In a normal adult population FA and ADC values of the brain white matter show regional variation. The repeatability of the ROI measurements also varies regionally. This regional variability must be acknowledged when these measurements are interpreted in clinical patients.
扩散张量成像（DTI）在研究和临床应用中越来越多地用于研究脑白质完整性。在对临床患者的DTI测量结果进行解读时，熟悉分数各向异性（FA）和表观扩散系数（ADC）值的正常变异以及测量的可重复性至关重要。
基于感兴趣区域（ROI）分析，建立1.5T和3T MRI下健康成年人群FA和ADC的正常值，并研究测量的观察者间和观察者内可重复性。
40名健康志愿者（26名女性，14名男性，平均年龄38.3岁，标准差11.6岁）接受了脑部常规MRI和DTI检查，其中30人使用3T临床扫描仪，10人使用1.5T临床扫描仪。在每个半球的五个不同解剖位置以及胼胝体的三个位置进行基于ROI的FA和ADC值测量。计算每个区域的FA和ADC平均值。通过比较两名观察者的结果评估ROI测量的观察者间变异，通过两名观察者对10名受试者进行重复测量评估观察者内变异。
不同区域的FA值差异很大。最高值分别出现在胼胝体的膝部和压部，最低值出现在放射冠。一般来说，ADC值的变异较小；最高值出现在胼胝体体部，最低值出现在放射冠。观察者间和观察者内测量的可重复性也因区域而异。胼胝体的一致性最高，放射冠和半卵圆中心的一致性最低。
在正常成年人群中，脑白质的FA和ADC值存在区域差异。ROI测量的可重复性也因区域而异。在对临床患者的这些测量结果进行解读时，必须认识到这种区域变异性。
