# NM multi-frame spatial spacing vector - DICOM

This is a discussion on NM multi-frame spatial spacing vector - DICOM ; In an NM multi-frame image we see the spacing between slices tag but there is no direction given. I would like to know if I can obtain the relative frame position from any standard tag, or should I assume that ...

# Thread: NM multi-frame spatial spacing vector

1. ## NM multi-frame spatial spacing vector

In an NM multi-frame image we see the spacing between slices tag but
there is no direction given.
I would like to know if I can obtain the relative frame position from
any standard tag, or should I assume that all frames advance only along
Z direction (have the same top left position X and Y coordinates).

Thanks,
Leon

2. ## Re: NM multi-frame spatial spacing vector

Hello Dicom Masters,

I have a problem in creating a 3D reconstruction out of a multiframe NM
image
My previous post on this issue didn't get any reference.
I would appreciate if you could share some insights.

Thanks,
Leon

leon wrote:
> In an NM multi-frame image we see the spacing between slices tag but
> there is no direction given.
> I would like to know if I can obtain the relative frame position from
> any standard tag, or should I assume that all frames advance only along
> Z direction (have the same top left position X and Y coordinates).

3. ## Re: NM multi-frame spatial spacing vector

Leon wrote:
> In an NM multi-frame image we see the spacing between slices tag but
> there is no direction given.
> I would like to know if I can obtain the relative frame position from
> any standard tag, or should I assume that all frames advance only along
> Z direction (have the same top left position X and Y coordinates).

Spacing Between Slices is defined in PS3.3 C.8.4.15, and it explicitly
describes the direction of the spatial step from one slice to the next:

Spacing between slices, in mm, measured from center-to-center of each
slice along the normal to the first image. The sign of the Spacing Between
Slices (0018,0088) determines the direction of stacking. The normal is
determined by the cross product of the direction cosines of the first row
and first column of the first frame, such that a positive spacing
indicates slices are stacked behind the first slice and a negative spacing
indicates slices are stacked in front of the first slice. See Image
Orientation (0020,0037) in the NM Detector module.
So Spacing Between Slices has direction and is along the normal to the
first slice. Do not assume all slices have the same X and Y coordinate.