Cut Plane of a 3D stack

Hi all,

I'm trying to get (coordinates) and count the 3D pixels belonging to a cut plane of a 3D cylindrical form (it's not a real regular cylinder. It's a brunch of a bifurcation). For this, I'm using the rule which stays that the equation of a cut plane perpendicular to a point A(xA,yA,zA) (belonging to the cylinder) can be defined if we have a normal vector vec_AB(xAB,yAB,zAB) with B a 3D pixel belonging to the cylinder and a point M(xM,yM,zM) (point belonging to the 3D stack) such as: vec_AB.dot(vec_AM)=0. Hence M is belonging to the cut plane. Is this the good approach ? I don't succeed to find 3D pixels that verify the equation of the cut plane obtained as: xAB*(xM - xA) + yAB*(yM-yA) + zAB*(zM-zA)=0