The noise power spectrum in CT with direct fan beam reconstruction.

Abstract:

:The noise power spectrum (NPS) is a useful metric for understanding the noise content in images. To examine some unique properties of the NPS of fan beam CT, the authors derived an analytical expression for the NPS of fan beam CT and validated it with computer simulations. The nonstationary noise behavior of fan beam CT was examined by analyzing local regions and the entire field-of-view (FOV). This was performed for cases with uniform as well as nonuniform noise across the detector cells and across views. The simulated NPS from the entire FOV and local regions showed good agreement with the analytically derived NPS. The analysis shows that whereas the NPS of a large FOV in parallel beam CT (using a ramp filter) is proportional to frequency, the NPS with direct fan beam FBP reconstruction shows a high frequency roll off. Even in small regions, the fan beam NPS can show a sharp transition (discontinuity) at high frequencies. These effects are due to the variable magnification and therefore are more pronounced as the fan angle increases. For cases with nonuniform noise, the NPS can show the directional dependence and additional effects.

journal_name

Med Phys

journal_title

Medical physics

authors

Baek J,Pelc NJ

doi

10.1118/1.3378673

subject

Has Abstract

pub_date

2010-05-01 00:00:00

pages

2074-81

issue

5

eissn

0094-2405

issn

2473-4209

journal_volume

37

pub_type

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