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Scan Geometry

The following types and functions describe the creation of scan geometries for the simulation.

ComputedTomography.Beam — Type
Beam

A data structure representing a single X-ray beam direction.

Fields

  • source::Tuple{Float64, Float64}, the source position of an X-ray beam in 2D space specified by a pair (x, y) that assumes an (absolute) underlying Cartesian coordinate system.
  • direction::Tuple{Float64, Float64}, the direction of the beam in 2D space specified by a pair (x, y) that assuming an (absolute) underlying Cartesian coordinate system.
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ComputedTomography.FanBeam — Type
FanBeam <: ScanGeometry

A data structure specifying a 2-dimensional fan beam scan geometry. The scan geometry is assumed to generate a fan shape that is then rotated around the object being scanned.

Fields

  • angle::Float64, a value in [0, π] that specifies the angle (radians) of the fan beam.
  • num_sources::Int64`, the number of beams emanating from the source.
  • rotation_step::Float64, a value in (0, π) that specifies the amount the source is rotated in a single increment around the object being scanned in radians.
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ComputedTomography.ParallelBeam — Type
ParallelBeam <: ScanGeometry

A data structure specifying a 2-dimensional parallel beam scan geometry. The scan geometry is a parallel set of beams. These are then rotated around the object being scanned.

Fields

  • width_ratio::Float64, a value in [0, 1] that specifies the width of the distance between the two furtherest sources (along the secant) as a fraction of the width of the diameter of rotation.
  • num_sources::Int64, the number of sources spread out along the indicated width ratio.
  • rotation_step::Float64, a value in (0, π) that specifies the amount the source is rotated in a single increment around the object being scanned in radians.
Info

The width ratio must be zero if the number of sources is one.

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ComputedTomography.generate — Method
generate(geometry::G, radius::Float64) where G<:ScanGeometry

Determines the source positions and beam directions of the scan geometry specified by geometry and the radius of rotation specified by radius.

Arguments

  • geometry<:ScanGeometry, the scan geometry for which to generate the beams.
  • radius::Float64, the radius of rotation around the object being scanned. This value must be positive and cannot be zero.

Returns

  • ::Vector{Beam}, a vector of Beam objects representing the source positions and beam directions of the scan geometry.

Throws

  • DomainError, if the radius of rotation is not positive.
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ComputedTomography.generate_from_baseline — Method
generate_from_baseline(
    baseline_x_positions::Vector{Float64},
    baseline_y_positions::Vector{Float64},
    baseline_x_directions::Vector{Float64},
    baseline_y_directions::Vector{Float64},
    rotation_angles::Vector{Float64},
)

Generates a vector of Beam objects from the baseline positions and directions by rotating the baselines through the angles specified in rotation_angles.

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