The Commissures

What are they?

The commissures are fibre tracts connecting the two hemispheres. There is a posterior commissure, which connects midbrain and diencephalon structures, and lies just in front of and above the superior colliculi, below the pineal gland. The posterior commissure is not always easy to see on a high detailed structural scan, and it is very unlikely you will be able to discern it on functional images.The anterior commissure (AC) connects the middle and inferior temporal gyri of the two hemispheres, and runs across the midline just in front of the fornix. It is relatively easy to see on most structural scans.
連接兩個半球的是纖維束搜锰。有一個后連合耿战，連接中腦和間腦結構，位于上丘的前面和上面狈涮，松果體下面。后連合并不總是很容易在高細節(jié)的結構掃描中看到歌馍，你也不太可能在功能圖像上看到它。前連合(AC)連接兩個半球的中間和下顳回暴浦，并在穹窿前穿過中線晓锻。這是相對容易看到的大多數(shù)結構掃描。

Why the commissures?

The commissure have become key landmarks, because Talairach and Tournoux chose them to determine the standard alignment of the brain for their famous atlas. To align a scan to Talairach space, a brain has to be set so that the anterior and posterior commissures are on a horizonatal line.

Where are they?

Below is a little schematic (from Chris Rorden's MriCro tutorial) of a sagittal brain view. The anterior commissure is shown in red, and the posterior commissure in yellow.

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The image below shows the anterior commissure on an iconic brain from the MNI series (see the MNI space page for details). The AC is at the virtual intersection of the red lines.

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The AC is best seen on slice 91 in X, 131 in Y and 67 in Z of the iconic brain image.

Below is an image showing the PC on the same brain, again at the (truncated) intersection of the red lines. The PC can best be seen at slices X 91, Y 103 and Z 70. Note that this brain is not exactly oriented according to the Talairach system, as the two commissures are not on the same axial plane.

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SPM 做AC原點校正

coronal(冠狀面循狰，正視圖)
Axial(軸狀面，俯視圖)
sagittal(矢狀面灿里，左視圖)
1程腹、roll：調整roll值使得十字準線的垂直線粗略的通過coronal視圖的中間。roll調整使得圖像繞y-axis旋轉
2寸潦、yaw：調整yaw值使得十字準線的垂直線粗略的通過axial視圖的中間。yaw調整使得圖像繞z-axis旋轉
（1命雀、2一般微調或者不調整）
3斩箫、調整好roll和yaw后尋找最中間的sagittal視圖：胼胝體（中間白色部分）最長最厚最清晰（里面幾乎沒有黑色）盡量把十字準線的交點放在AC上（紅色的點）、黃色的點為PC（后連合）前面圖
4乘客、調整pitch（pitch調整使得圖像繞x-axis旋轉) 使得sagittal十字準線的橫線穿過前連合（AC：紅色的點）后連合（PC：黃色的點），如上圖

image.png

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原文鏈接：https://blog.csdn.net/QW_sunny/article/details/62052282