[Rtk-users] R: Trying to reconstruct with a 180 degrees circular projection geometry

[Clément Mirabel]

Alright, I will give it a try. Thank you for your guidance!

Le ven. 11 déc. 2020 à 11:44, Simon Rit <simon.rit at creatis.insa-lyon.fr> a
écrit :

> You can check https://doi.org/10.1088/0031-9155/47/14/311 which is not
> implemented in RTK (yet). But only one half of the field-of-view can be
> reconstructed exactly if you rate 180°. For the rest, there will be missing
> data.
> With RTK, iterative reconstruction should achieve a decent result but will
> necessarily be limited by the missing data. I recommend the conjugate
> gradient algorithm which will require adjusting the regularization
> parameter Gamma and the number of iterations.
>
> On Fri, Dec 11, 2020 at 11:26 AM Clément Mirabel <
> clement.mirabel at gmail.com> wrote:
>
>> Hi,
>>
>> Thank you both for your answer.
>> I managed to have a good reconstruction with 200° since my cone angle is
>> about 20°. I didn't mention in my original email that I was already using
>> Parker weightings, but as you mentioned I needed higher angles. Thank you
>> for your help.
>> As a more general question, the machine I am using to acquire data can
>> only rotate 180° around the patient but is still able to reconstruct (I
>> don't have access to the projections, it generates a 3d volume as output).
>> Are you aware of any algorithm that would be able to do so?
>>
>> Clément
>>
>> Le ven. 11 déc. 2020 à 10:03, Simon Rit <simon.rit at creatis.insa-lyon.fr>
>> a écrit :
>>
>>> Hi Clément,
>>> To complement Gabriele's response and explains what goes on. FDK
>>> requires a 360° acquisition. RTK will calculate the angular gap between the
>>> current projection and the two neighbors. With your configuration, two
>>> projections take an angular weight (the delta when discretising the
>>> backprojection integral) of about 90°.
>>> You can do a short scan with Parker weightings but, as stated by
>>> Gabriele, that necessitates at least 180° + the cone angle.
>>> Simon
>>>
>>> On Fri, Dec 11, 2020 at 9:23 AM <gabriele.belotti.bergamo at gmail.com>
>>> wrote:
>>>
>>>> Hi Clément,
>>>>
>>>> It seems likely that your geometry is not 180+fan-angle complete and
>>>> therefore cannot lead to a proper reconstruction. From your attached
>>>> geometry, you sweep from 0 to 178° (180-increment).
>>>>
>>>> My suggestion would be to try some intermediate angles, so to recreate
>>>> a complete ShortScan. I suggest you to try at least a 200/220 ° arc to
>>>> check on your simulation pipeline.
>>>>
>>>> I hope this is helpful,
>>>> Gabriele
>>>>
>>>>
>>>>
>>>> *Da:* Rtk-users <rtk-users-bounces at public.kitware.com> *Per conto di *Clément
>>>> Mirabel
>>>> *Inviato:* venerdì 11 dicembre 2020 09:11
>>>> *A:* rtk-users at public.kitware.com
>>>> *Oggetto:* [Rtk-users] Trying to reconstruct with a 180 degrees
>>>> circular projection geometry
>>>>
>>>>
>>>>
>>>> Hi,
>>>>
>>>>
>>>>
>>>> I have been trying to set the geometry in
>>>> ThreeDCircularProjectionGeometry with values between 0 and 180 degrees, to
>>>> reproduce the motion of some acquisition systems, but reconstruction is far
>>>> from the expected result when the gantry angle does not reach max value of
>>>> (360-increment). (Attached is the geometry file generated)
>>>>
>>>> My workflow is the following :
>>>>
>>>>    - Apply JosephForwardProjectionImageFilter on a 3D Volume
>>>>    - Try to reconstruct using FDKConeBeamReconstructionFilter
>>>>
>>>> Although, the result from JosephForwardProjectionImageFilter describes
>>>> a 180 degrees rotation, the output of the reconstruction seems to display
>>>> rays from opposite direction but not from rotated directions
>>>>
>>>>
>>>>
>>>> Here is a view of what is supposed to be an axial slice:
>>>>
>>>>
>>>>
>>>> Thanks for your help!
>>>>
>>>>
>>>>
>>>> Clément
>>>>
>>>>
>>>> _______________________________________________
>>>> Rtk-users mailing list
>>>> Rtk-users at public.kitware.com
>>>> https://public.kitware.com/mailman/listinfo/rtk-users
>>>>
>>>
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