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<div class="moz-cite-prefix">On 19.07.22 18:23, Simon Rit wrote:<br>
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cite="mid:CAF0oig29nsUoSkYEZAcSKOhN+HrLiyeU4vAePqCE3cMMgNQuZw@mail.gmail.com">
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<div>Hi Vincent,</div>
<div>Thanks for the report. I don't believe that there is need
for a PR. It comes down to using a different parameterization
which I think you can always go around with one of the
different versions of AddProjection.</div>
<div>Did I mention that the out of plane angle has no effect
below 2°? If yes, I'm not sure you can trust this
information... as I don't know where it comes from.</div>
<div>Best regards,<br>
</div>
<div>Simon<br>
</div>
</div>
<br>
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<div dir="ltr" class="gmail_attr">On Tue, Jul 19, 2022 at 11:34
AM Vincent Libertiaux <<a href="mailto:vl@xris.eu"
moz-do-not-send="true" class="moz-txt-link-freetext">vl@xris.eu</a>>
wrote:<br>
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0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
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<div>On 11.05.22 15:20, Vincent Libertiaux wrote:<br>
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<div>On 11.05.22 15:15, Simon Rit wrote:<br>
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<div>Hi,</div>
<div>Yes, I think it's correct. To be sure you
correctly understand it, you can always do test
cases with the source and detector positions, u v
vectors in the coordinate system of your object.</div>
<div><a
href="http://www.openrtk.org/Doxygen/classrtk_1_1ThreeDCircularProjectionGeometry.html#a0fb1475ed76a28cde24fac85eae18e1e"
target="_blank" moz-do-not-send="true"
class="moz-txt-link-freetext">http://www.openrtk.org/Doxygen/classrtk_1_1ThreeDCircularProjectionGeometry.html#a0fb1475ed76a28cde24fac85eae18e1e</a></div>
<div>and then check the resulting angles and
distances.<br>
</div>
<div>Simon<br>
</div>
</div>
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<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Wed, May 11, 2022
at 2:15 PM Vincent Libertiaux <<a
href="mailto:vl@xris.eu" target="_blank"
moz-do-not-send="true"
class="moz-txt-link-freetext">vl@xris.eu</a>>
wrote:<br>
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<blockquote class="gmail_quote" style="margin:0px 0px
0px 0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">On 10.05.22
22:54, Simon Rit wrote:<br>
> Hi Vincent,<br>
> RTK can parametrize any orientation of the
detector with the three <br>
> angles GantryAngle, InPlaneAngle,
OutOfPlaneAngle. 0.025° seems very <br>
> small indeed! I don't know how much you know
about software B but the <br>
> easiest would be to have either the projection
matrix or the source <br>
> position, detector position, u axis and v axis
in patient/object <br>
> coordinates to derive the RTK parameters.<br>
> Good luck with this!<br>
> Simon<br>
<br>
Hi Simon !<br>
<br>
Unfortunately, I don't have access to B projection
matrices.<br>
<br>
As for the detector orientation in RTK, I have made
this picture to make <br>
sure I understand properly how to use the gantry
angle to achieve my <br>
desired geometry:<br>
<br>
<a href="https://ibb.co/J3H8z9M" rel="noreferrer"
target="_blank" moz-do-not-send="true"
class="moz-txt-link-freetext">https://ibb.co/J3H8z9M</a><br>
<br>
The cyan detector is the default configuration with
a 0° gantry angle. <br>
The blue detector is at a gantry angle of alpha
(largely exaggerated for <br>
the sake of clarity). So in order to simulate an
out-of-plane rotation <br>
of the detector around its vertical axis, I should
translate this blue <br>
detector so that its center matches the coordinates
of the cyan one, and <br>
translate the source accordingly (along the black
vectors on the <br>
picture) ? I assume that proj_iso_x/y and
source_x/y are expressed in <br>
the gantry system of coordinates (local) ?<br>
<br>
<br>
Thank you again for your feedback,<br>
<br>
kindest regards,<br>
<br>
V.<br>
<br>
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<p>Thanks Simon,</p>
<p>I'll investigate more and let you know. Hopefully, it
might be useful to someone else one day !</p>
<p>V.<br>
</p>
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<p>Hi Simon,</p>
<p>I finally got some time to investigate further this issue
this week. I managed to get sharp edges everywhere now
and it was indeed the detector out-of-plane angle colinear
with the gantry angle that was the cause. The value given
by the other software seems to have been in rad rather
than degrees; the angle I found was 1.15°. This makes me
wonder what were the assumptions under which no effect was
found for angles below 2°. If you know the title of the
seminal paper, I'd be interested to read it.</p>
<p><br>
</p>
<p>As for the mean to include this angle in the geometry, no
extra code was indeed needed. If we call this extra angle
"c", the following modifications have to be made in
rtksimulatedgeometry:</p>
<p>- first angle = c</p>
<p>- sdd = sdd_0 * cos(c)</p>
<p>- sid = sid_0 * cos(c)</p>
<p>- source_x = source_x0 - sid*sin(c)</p>
<p>- proj_iso_x = proj_iso_x0 + (sdd-sid)*sin(c)</p>
<p>I can't really promise I'll find time to do it, but if it
is the case, I'll submit a PR to include that in the
matrices computation.</p>
<p>Hopefully, it will help others on the list who
encountered a similar issue.<br>
</p>
<p>Best regards,</p>
<p>Vincent<br>
</p>
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<p>Hi Simon,</p>
<p>you didn't mention that the out of plane angle has no effect
below 2°. I have read that in several papers about CT geometric
calibration. To be honest, I am glad that no PR is needed, I have
a lot on my plate at work these days :).</p>
<p>Best regards,</p>
<p>V.<br>
</p>
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