Dear Castor users;
I tried to reconstruct using my Gate data, but the reconstructed image was not correct, as shown in the figure below, I reconstructed a line source, but there was nothing in the center of the image, there were bright spots around the image that looked like a line source. My .geom file is directly generated using Gate’s .mac file, and the castor format data is also generated directly from the root data output by Gate using the conversion tool provided by castor. Which step did I make a mistake at? I will thank you for any answers.
Hi,
There are two general rules that I try to follow when facing a problem:
1: before looking for help, when something is wrong at the final step, it is usual to look at intermediate steps,
2: when looking for help, it is usual to provide all information you have.
With respect to 1:
- do you have proof that your simulation went well ? Is there any data in your ROOT file ?
- do you have counts in the converted CASToR datafile ?
- if PET, did you look at the sensitivity image to check that the geometry seems ok ?
With respect to 2: - are you doing PET or SPECT ?
- what is the setup of your simulation, geometry of the system, acquisition duration and activity ?
Simon
Hi Simon,
Thanks for your reply！What I do is PET reconstruction，I checked my root file and converted castor data file, they all have data, root file can view the coordinate location of the data in ROOT and other information, part of the castor data information is shown in the figure below, can get the time information and crystal number information, but did not add normalization or scattering correction and other information. The calculated sensitivity image is indeed a cylindrical field of view as shown in the figure below, but I don’t know if such a sensitivity image is correct.
The main.mac file is also attached to the radioactive source, since the program was too long, only parts were pasted, and information about the scanner geometry and source construction was omitted, which is a wire source with a length of 80 mm, a radius of 0.125 mm, and an activity of 500,000 becquerels.
part of the main.mac.pdf (39.6 KB)
Thanks for the details.
The conversion of the geometry seems ok as the sensitivity image looks quite usual.
You have events in your datafile.
Are you able to verify in the ROOT file the positioning of the events you detect (sourcePosXYZ) just to see if there is no problem in the positioning of the source ?
Then, maybe the problem comes from the settings of the reconstruction.
Can you provide the command line for the reconstruction ?
Simon
Hi Simon,
Thanks for your reply！
The positioning of the events you detect (sourcePosXYZ) are shown in the images below,
and my command line of reconstruction is:
./castor-GATERootToCastor
-i /home/yuanh/castor/castor_v3.1.1/bin_debug/test4.root
-o /home/yuanh/castor/castor_v3.1.1/bin_debug/linesource
-m /home/yuanh/castor/castor_v3.1.1/bin_debug/main.mac
-s Gatewater_ihep
-t
-ist F-18
-geo
./castor-recon -df linesource_1_df.Cdh -opti MLEM -it 5:16 -proj joseph -conv gaussian,4.,4.,3.5::psf -conv gaussian,6.,6.,3.5::post -dim 236,236,95 -fov 128.,128.,95. -off 0.,0.,0. -dout my_images
Well it is hard to say, everything looks normal.
Maybe simplify the reconstruction: remove the PSF to avoid too strong deconvolution in the air then restrict the FOV to 1cm with coarser voxels “-fov 10.,10.,95. -dim 10.,10.,95”.
Hi Simon,
Thank you very much for your reply, I’ll try the suggestions.
Hi,
What are the values of the voxels in the center of your image (where the line source should be) ? Equal to 0 ? Very low ? NaN ?
Sometimes you don’t see the object because the edges of the image have extremely high values as the sensitivity is low in these areas (resulting in acute correction factors values). The visualization software may adapt the contrast from the (very high) edge values, consequently you only see the edges and not your object.
Thibaut
Hi,
Thanks for your reply. The line source should be in the center of the image, but the value in the center of the image is 0.