[Rtk-users] Fwd: How to put the DRR in the middle of the Image?

[Simon Rit]

Hi,
Setting SDD to 0 means using a parallel beam. If SID and SDD are set to
specific values, the beam is divergent and you need to use the Thales
theorem to calculate the projections origin and spacing. For example, if
SID==1000 and SDD==2000, you need to double origin and spacing.
I hope it helps,
Simon

On Mon, Nov 6, 2023 at 6:14 AM qod rec <recqod at gmail.com> wrote:

> Hello!
> I'm using the RTK geometry and the JosephForwardProjectionImageFilter to
> generate a rotated DRR from a 3d CT.
> For geometry, I set the outOfPlaneAngle = 90. to rotate the DRR.
> I found that when I set sdd(source to detector distance) = 0, I can easily
> get the DRR filling up the Image by setting the Image origin and spacing
> being the same with the origin and spacing of the original CT.
> But when I want the DRR to be like a clinical X-ray which means I need to
> set the sid and sdd to a specific value, I found that the above Image
> setting strategy failed to set the DRR filling up the image and also there
> are some transitions that make the DRR not in the middle.
> Are there any ways to decide the Image origin and spacing using the
> specific sid and sdd？
> Thank you！
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