In the FBP algorithm, the ramp filter |w| has the zero response for the 0-frequency, thus its output has zero for the DC component, i.e., the average value would be zero, then, there would be negative values to compensate the common positive values. Since the nagative values are introduced by the ramp filtering and the image is positive generally, how to perform the normalization before the quantitative evaluation against the reference image?
Thanks.
This question is related with my previous one:
https://www.researchgate.net/post/proper_image_normalization_for_quantitative_comparison
Thank you @Syed Amir Gilani. I will read the thesis carefully for my question.
@Aparna Sathya Murthy, thank you!
I think my question includes:
(1) The FBP algorithm is based on multiple summation of discrete backprojections, there are normalization factors.
(2) In the simulation, the sinogram may be from the Radon transform of digital image or directly sampling the analytical expression (my previous question: https://www.researchgate.net/post/are_there_tools_in_Matlab_to_create_the_phantom_sinogram_from_the_analytical_expression_directly), and the normalization factors in (1) may be different.
(3) Comparison and evaluation are actually for the reconstruction noise level but the noise may affect the normalization factors.
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