RAS Coordinate System & World Coordinate system

Development
1

Operating system: window 11
Slicer version: 4.13.0

Hi, everyone
I tried to mark a point on the 3d slicer through the markups tool and load the position data.

Here is the code I used.

node_mark = slicer.util.getNode(‘F’)
wcs_data = arrayFromMarkupsControlPoints(node_mark, True)

Comparing wcs_data and node_mark shows the same coordinates.

I thought node_mark would belong to the RAS coordinate system and
wcs_data to belong to the world coordinate system, but isn’t it like this?

2

3D Slicer’s world coordinate system is the RAS coordinate system.

3

Hi Lassoan,

Thx for answering !

But I’m still confused

Since the python module I made that I want to extend with 3D slicer follows w.c.s (general world coordinate system), do RAS coordinates of 3D slicer refer to normal w.c.s?

4

To display any node in a custom coordinate system, add a transform node, set its transform to parent matrix, and set this transform in the transformable node.

1 Like
5

hum…

Actually, the question was whether the 3D slicer’s RAS coordinate system is the (general - people think) world coordinate system. However, if you refer to the reference of lassoan, it seems to be roughly understood. I will try and come back if successful.

6

the question was whether the 3D slicer’s RAS coordinate system is the (general - people think) world coordinate system

Yes, the world coordinate system of the application is the RAS coordinate system. For example, when you load a medical image then the image is displayed so that the image origin is aligned with the world coordinate system origin; R, A, S axes of the image are the first, second, and third axis of the world coordinate system; and world coordinate system unit is millimeters.

1 Like