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jmaces / aapm-ct-challenge

AAPM DL Sparse-View Computed Tomography Image Reconstruction Challenge - Team Robust-And-Stable
MIT License
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Question about inverse operator #1

Closed ceilingFan456 closed 3 weeks ago

ceilingFan456 commented 2 months ago

Hello, I have a question about the implementation of filtered back projection. After solving the integral, x is divided by the spacing between detectors. What is the reason for doing this? Thank you.

https://github.com/jmaces/aapm-ct-challenge/blob/81cdf946438ea2227eb4007f9e3ac4e546d4b0c4/aapm-ct/operators.py#L509C2-L509C39

jmaces commented 2 months ago

The code part you referenced is not the inverse operator but the adjoint. It is a numerical approximation of an integral that is summing along the discrete detector elements. Dividing by the spacing is a normalization factor for the integral to make this the proper adjoint.

ceilingFan456 commented 1 week ago

Thank you for the clarification. And Thank you for the awesome work too :D