Hello all, The question of neglecting out-of-plane offsets if less than 2 degrees is discussed in Yang et al, Med. Phys., 2006, section III.A. Regards, Jerome
Le mar. 19 juil. 2022 à 18:23, Simon Rit <simon....@creatis.insa-lyon.fr> a écrit : > Hi Vincent, > 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. > 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. > Best regards, > Simon > > On Tue, Jul 19, 2022 at 11:34 AM Vincent Libertiaux <v...@xris.eu> wrote: > >> On 11.05.22 15:20, Vincent Libertiaux wrote: >> >> On 11.05.22 15:15, Simon Rit wrote: >> >> Hi, >> 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. >> >> http://www.openrtk.org/Doxygen/classrtk_1_1ThreeDCircularProjectionGeometry.html#a0fb1475ed76a28cde24fac85eae18e1e >> and then check the resulting angles and distances. >> Simon >> >> On Wed, May 11, 2022 at 2:15 PM Vincent Libertiaux <v...@xris.eu> wrote: >> >>> On 10.05.22 22:54, Simon Rit wrote: >>> > Hi Vincent, >>> > RTK can parametrize any orientation of the detector with the three >>> > angles GantryAngle, InPlaneAngle, OutOfPlaneAngle. 0.025° seems very >>> > small indeed! I don't know how much you know about software B but the >>> > easiest would be to have either the projection matrix or the source >>> > position, detector position, u axis and v axis in patient/object >>> > coordinates to derive the RTK parameters. >>> > Good luck with this! >>> > Simon >>> >>> Hi Simon ! >>> >>> Unfortunately, I don't have access to B projection matrices. >>> >>> As for the detector orientation in RTK, I have made this picture to make >>> sure I understand properly how to use the gantry angle to achieve my >>> desired geometry: >>> >>> https://ibb.co/J3H8z9M >>> >>> The cyan detector is the default configuration with a 0° gantry angle. >>> The blue detector is at a gantry angle of alpha (largely exaggerated for >>> the sake of clarity). So in order to simulate an out-of-plane rotation >>> of the detector around its vertical axis, I should translate this blue >>> detector so that its center matches the coordinates of the cyan one, and >>> translate the source accordingly (along the black vectors on the >>> picture) ? I assume that proj_iso_x/y and source_x/y are expressed in >>> the gantry system of coordinates (local) ? >>> >>> >>> Thank you again for your feedback, >>> >>> kindest regards, >>> >>> V. >>> >>> Thanks Simon, >> >> I'll investigate more and let you know. Hopefully, it might be useful to >> someone else one day ! >> >> V. >> >> Hi Simon, >> >> 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. >> >> >> 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: >> >> - first angle = c >> >> - sdd = sdd_0 * cos(c) >> >> - sid = sid_0 * cos(c) >> >> - source_x = source_x0 - sid*sin(c) >> >> - proj_iso_x = proj_iso_x0 + (sdd-sid)*sin(c) >> >> 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. >> >> Hopefully, it will help others on the list who encountered a similar >> issue. >> >> Best regards, >> >> Vincent >> > _______________________________________________ > Rtk-users mailing list > Rtk-users@public.kitware.com > https://public.kitware.com/cgi-bin/mailman/listinfo/rtk-users >
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