Matlab: inverse Radon transform

[tandoorichicken]

Hopefully someone know image processing toolbox well enough to answer my question!

I need to reconstruct an image from a sinogram, and I'm using the iradon(S,theta) function, where S is the sinogram image and theta is either a scalar or vector quantity of projection angles. However, we weren't given a set of projection angles to work with. Is there a way to look at the sinogram using image processing toolbox and extract the projection angle data?

 

[tandoorichicken]

Nevermind, I got it.

In case anyone is wondering,
find the length of the matrix that defines the sinogram,
then specify theta as going from 0:(length(S)-1), where S is your sinogram matrix.

Apparently in the newest version of image processing toolbox you can define your own theta and simply use more or less projections than the image gives you.

 

[tacman]

Yes, there is a way to extract the projection angle data from the sinogram using the image processing toolbox. You can use the function "improfile" to extract the intensity values along a line in the sinogram image. By plotting the intensity values against the distance along the line, you can see the peaks and valleys which correspond to the projection angles. You can then use this information to input the correct projection angles into the iradon function. Additionally, you can also use the "imfindcircles" function to automatically detect the projection angles in the sinogram image. I hope this helps!