Hi Fredrik, It is because the "halfDetectorWidth" here is the value for an untilted virtual detector at the isocenter which is equivalant to the real detector.
Regards, Chao 2017-09-25 14:01 GMT+02:00 Fredrik Hellman <fredrik.hell...@gmail.com>: > Hi, > > In rtkParkerShortScanFilter.hxx (line 113) and > rtkCudaParkerShortScanFilter.cxx (line 95), the overscan angle is checked > to be large enough for the used beam fan angle. (There is a difference > between how this check is performed in the two cases. It seems like the > CUDA-version assumes that the piercing point is in the middle of the > detector. That's not what this question is about though.) > > The beam fan angle seems to be computed as > > arctan( halfDetectorWidth / sourceToIsocenterDistance ) > > Why sourceToIsocenterDistance? Shouldn't it be sourceToDetectorDistance? > If the detector is far away from the isocenter, the beam fan angle should > also be small as far as I understand. This is not reflected in this > computation. > > Best regards, > Fredrik Hellman > > _______________________________________________ > Rtk-users mailing list > Rtk-users@public.kitware.com > http://public.kitware.com/mailman/listinfo/rtk-users > >
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