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
On Tue, May 10, 2022 at 5:23 PM Vincent Libertiaux <v...@xris.eu> wrote: > On 25.04.22 09:07, Simon Rit wrote: > > Hi Vincent (and Jasper), > I agree with Jasper that this is most likely due to a difference in > geometric calibration between the two datasets. Do you have more > information on what does B use (projection matrices, detailed > parametrization, etc.)? I think that such a blur can be caused by a > difference in source to detector distance (or, equivalently, detector pixel > size). > Simon > > On Tue, Apr 19, 2022 at 11:08 AM Vincent Libertiaux <v...@xris.eu> wrote: > >> On 16.04.22 13:52, Jasper Albertus Nijkamp wrote: >> > Hi Vincent, >> > >> > From just these two images, it is a bit hard to help. However, I have >> seen similar challenges when the detector vertical offset is not properly >> set. If you could share a bit more data (fx projection data and the >> geometry), more people might be able to help. >> > >> > Jasper >> > >> > -----Original Message----- >> > From: Rtk-users <rtk-users-boun...@public.kitware.com> On Behalf Of >> Vincent Libertiaux >> > Sent: Friday, 15 April 2022 17:15 >> > To: rtk-users <rtk-users@public.kitware.com> >> > Cc: Damien Koch <d...@xris.eu> >> > Subject: [Rtk-users] Lateral blur in a FDK reconstructed volume >> > >> > Hello rtk users ! >> > >> > I am facing a problem for which I have exhausted all the possibilities >> except asking you. >> > I have performed a standard FDK reconstruction of a lego bricks >> assembly. I used a custom-made code to compute the detector horizontal >> offset and tilt angle, found to be 1.15 mm and 0.02° respectively. The >> result of the reconstruction is shown in the picture >> > https://ibb.co/LdMzJF2 . The volume looks mostly sharp, except on the >> lateral edges, let's say on the last half brick. >> > >> > We had the opportunity to have the same volume reconstructed with two >> commercial solutions. The first one, "A", produced the same results than >> rtk. The second, "B", produced the result shown in the picture >> https://ibb.co/VwXMmRH >> > >> > In this case, the edges are sharp too. The offset values found with >> this software were very close (1.13mm and 0.025° respectively) and feeding >> them to rtksimulatedgeometry didn't change my result. No other correction >> was allegedly applied. >> > >> > I thought that the edge blurring was due to a wobbling artefact but it >> can't be the case according to the result with the "B" software. >> > >> > Do you have any idea on what could cause this blurring on the edges ? >> > >> > I thank you very much for any clue. >> > >> > Best regards, >> > >> > Vincent >> > >> > _______________________________________________ >> > Rtk-users mailing list >> > Rtk-users@public.kitware.com >> > https://public.kitware.com/cgi-bin/mailman/listinfo/rtk-users >> >> Hi Jasper, >> >> thank you for your reply. I had already tried to play with the vertical >> offset but setting it to a value different than 0 progressively decrease >> the overall quality of the reconstruction. >> Following your advice, here are the projections: >> >> http://share.xris.eu/d91b09673bba >> >> word of warning, the set is very large (900 projections on a 3072x3072 >> pixels detector, approx. size = 16Go) I could try and make it smaller >> by downsampling it but I am afraid it would mask the problem. I can try >> and do it on request. >> The geometric parameters I used were: SDD = 810 mm, SID = 410 mm, >> proj_iso_x = 1.15mm and in_angle = 0.02°. >> >> >> Best regards, >> >> Vincent >> >> _______________________________________________ >> Rtk-users mailing list >> Rtk-users@public.kitware.com >> https://public.kitware.com/cgi-bin/mailman/listinfo/rtk-users >> >> Hi Simon, hi Jasper. > > I have investigated a bit more on that issue. I told you in my first > message that both software we used besides rtk found the same set of > parameters. After playing a bit more with the software "B" (the one that > gives the sharp edges), I found out that the tilt angle is found to be 0 > and it is the out-of-plane angle around the vertical axis of the detector > which is non zero (and very coincidentally is very close to the tilt angle > we computed). The value is quite low (0.025°). I am a bit puzzled as, if > I am not mistaken, the literature always assumes that both out of plane > angles are negligible as long as they don't come close 2°. We are two > order of magnitude below this value, hence my surprise. > > I am also wondering if this angle can be introduced in the rtk geometry. > From the doc (http://www.openrtk.org/Doxygen/DocGeo3D.html), it seems > that only the out-of-plane angle around the detector horizontal axis is > considered. Is that correct ? If yes, is there a way to model the other > one with the available parameters ? > > Once again, thank you for any help you can provide. > > Kindest regards, > > Vincent > > > > > >
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