Geometric studies on variable radius spiral cone-beam scanning.

Abstract:

:The goal is to perform geometric studies on cone-beam CT scanning along a three-dimensional (3D) spiral of variable radius. First, the background for variable radius spiral cone-beam scanning is given in the context of electron-beam CT/micro-CT. Then, necessary and sufficient conditions are proved for existence and uniqueness of PI lines inside the variable radius 3D spiral. These results are necessary steps toward exact cone-beam reconstruction from a 3D spiral scan of variable radius, adapting Katsevich's formula for the standard helical cone-beam scanning. It is shown in the paper that when the longitudinally projected planar spiral is not always convex toward the origin, the PI line may not be unique in the envelope defined by the tangents of the spiral. This situation can be avoided by using planar spirals whose curvatures are always positive. Using such a spiral, a longitudinally homogeneous region inside the corresponding 3D spiral is constructed in which any point is passed by one and only one PI line, provided the angle omega between planar spiral's tangent and radius is bounded by [omega - 90 degrees] < or = < epsilon for some positive epsilon < or = 32.48 degrees. If the radius varies monotonically, this region is larger and one may allow epsilon < or = 51.85 degrees. Examples for 3D spirals based on logarithmic and Archimedean spirals are given. The corresponding generalized Tam-Danielsson detection windows are also formulated.

journal_name

Med Phys

journal_title

Medical physics

authors

Yea Y,Zhu J,Wang G

doi

10.1118/1.1751251

subject

Has Abstract

pub_date

2004-06-01 00:00:00

pages

1473-80

issue

6

eissn

0094-2405

issn

2473-4209

journal_volume

31

pub_type

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