toupy.simulation package

Submodules

toupy.simulation.phantom_creator module

Module to create the Shepp-Logan phantom for simulation Forked from https://jenda.hrach.eu/f2/cat-py/phantom.py

toupy.simulation.phantom_creator.phantom(N=256, phantom_type='Modified Shepp-Logan', ellipses=None)[source]

Create a Shepp-Logan 1 or modified Shepp-Logan phantom 2 . A phantom is a known object (either real or purely mathematical) that is used for testing image reconstruction algorithms. The Shepp-Logan phantom is a popular mathematical model of a cranial slice, made up of a set of ellipses. This allows rigorous testing of computed tomography (CT) algorithms as it can be analytically transformed with the radon transform.

Parameters

  • N (int) – The edge length of the square image to be produced

  • phantom_type (str, optional) – The type of phantom to produce. Either Modified Shepp-Logan or Shepp-Logan. The default value is Modified Shepp-Logan. This is overriden if ellipses is also specified.

  • ellipses (array like) – Custom set of ellipses to use.

Note

To use ellipses, these should be in the form [[I, a, b, x0, y0, phi], [I, a, b, x0, y0, phi], ...] where each row defines an ellipse and:

  • I : Additive intensity of the ellipse.

  • a : Length of the major axis.

  • b : Length of the minor axis.

  • x0 : Horizontal offset of the centre of the ellipse.

  • y0 : Vertical offset of the centre of the ellipse.

  • phi : Counterclockwise rotation of the ellipse in degrees, measured as the angle between the horizontal axis and the ellipse major axis.

The image bouding box in the algorithm is [-1, -1], [1, 1], so the values of a, b, x0 and y0 should all be specified with respect to this box.

Returns

P – A 2-dimensional array containing th Shepp-Logan phantom image.

Return type

ndarray

Examples

>>> import matplotlib.pyplot as plt
>>> P = phantom()
>>> # P = phantom(256, 'Modified Shepp-Logan', None)
>>> plt.imshow(P)

References

1

Shepp, L. A., Logan, B. F., “Reconstructing Interior Head Tissue from X-Ray Transmission”, IEEE Transactions on Nuclear Science, Feb. 1974, p. 232

2

Toft, P., “The Radon Transform - Theory and Implementation”, Ph.D. thesis, Department of Mathematical Modelling, Technical University of Denmark, June 1996