¥Transformation proceeds in
two stages:
1.Alignment of AC-PC and I-S axes (to +acpc coordinates)
2.Scaling to
Talairach-Tournoux Atlas brain size (to +tlrc
coordinates)
¥
¥Alignment to +acpc coordinates:
²Anterior commissure (AC) and posterior commissure (PC) are aligned to be the y-axis
²The longitudinal (inter-hemispheric or mid-sagittal) fissure is aligned
to be the yz-plane, thus defining the
z-axis
²The axis perpendicular to these is the x-axis (right-left)
²Five markers that you must place using the [Define Markers] control panel:
å AC superior edge = top middle of anterior
commissure
å AC posterior
margin = rear
middle of anterior commissure
å PC inferior edge = bottom middle of posterior
commissure
å First mid-sag
point = some
point in the mid-sagittal plane
å Another mid-sag
point = some other point in the
mid-sagittal plane
²This procedure tries to follow the Atlas as precisely as possible
åEven at the cost of confusion to the user (e.g., you)