Holmes C J, Hoge R, Collins L, Woods R, Toga A W, Evans A C
Laboratory of Neuroimaging, University of California School of Medicine, Los Angeles 90024, USA.
J Comput Assist Tomogr. 1998 Mar-Apr;22(2):324-33. doi: 10.1097/00004728-199803000-00032.
With the advent of noninvasive neuroimaging, a plethora of digital human neuroanatomical atlases has been developed. The accuracy of these atlases is constrained by the resolution and signal-gathering powers of available imaging equipment. In an attempt to circumvent these limitations and to produce a high resolution in vivo human neuroanatomy, we investigated the usefulness of intrasubject registration for post hoc MR signal averaging.
Twenty-seven high resolution (7 x 0.78 and 20 x 1.0 mm3) T1-weighted volumes were acquired from a single subject, along with 12 double echo T2/proton density-weighted volumes. These volumes were automatically registered to a common stereotaxic space in which they were subsampled and intensity averaged. The resulting images were examined for anatomical quality and usefulness for other analytical techniques.
The quality of the resulting image from the combination of as few as five T1 volumes was visibly enhanced. The signal-to-noise ratio was expected to increase as the root of the number of contributing scans to 5.2, n = 27. The improvement in the n = 27 average was great enough that fine anatomical details, such as thalamic subnuclei and the gray bridges between the caudate and putamen, became crisply defined. The gray/white matter boundaries were also enhanced, as was the visibility of any finer structure that was surrounded by tissue of varying T1 intensity. The T2 and proton density average images were also of higher quality than single scans, but the improvement was not as dramatic as that of the T1 volumes.
Overall, the enhanced signal in the averaged images resulted in higher quality anatomical images, and the data lent themselves to several postprocessing techniques. The high quality of the enhanced images permits novel uses of the data and extends the possibilities for in vivo human neuroanatomy.
随着无创神经成像技术的出现，已开发出大量数字人类神经解剖图谱。这些图谱的准确性受到现有成像设备分辨率和信号采集能力的限制。为了规避这些限制并生成高分辨率的活体人类神经解剖结构，我们研究了个体内配准用于事后磁共振信号平均的效用。
从一名受试者获取了27个高分辨率（7×0.78和20×1.0立方毫米）的T1加权容积，以及12个双回波T2/质子密度加权容积。这些容积被自动配准到一个共同的立体定向空间，在该空间中对它们进行二次采样并进行强度平均。检查所得图像的解剖质量以及对其他分析技术的效用。
仅由五个T1容积组合而成的所得图像质量明显提高。信噪比预计随着参与扫描次数的平方根增加至5.2，n = 27。n = 27时的平均值改善足够大，以至于精细的解剖细节，如丘脑亚核以及尾状核与壳核之间的灰质桥，变得清晰可辨。灰白质边界也得到了增强，被不同T1强度组织包围的任何更精细结构的可见性也得到了增强。T2和质子密度平均图像的质量也高于单次扫描，但改善程度不如T1容积显著。
总体而言，平均图像中增强的信号产生了更高质量的解剖图像，并且这些数据适用于多种后处理技术。增强图像的高质量允许对数据进行新的应用，并扩展了活体人类神经解剖学的可能性。
