Image Processing Toolbox User's Guide |

**Reconstructing an Image from Fan-Beam Projection Data **

To reconstruct an image from fan-beam projection data, use the `ifanbeam`

function. With this function, you specify as arguments the projection data and the distance between the vertex of the fan-beam projections and the center of rotation when the projection data was created. For example, this code recreates the image `I`

from the projection data `P`

and distance `D`

.

By default, the `ifanbeam`

function assumes that the fan-beam projection data was created using the arc fan sensor geometry, with beams spaced at 1 degree angles and projections taken at 1 degree increments over a full 360 degree range. As with the `fanbeam`

function, you can use `ifanbeam`

parameters to specify other values for these characteristics of the projection data. Use the same values for these parameters that were used when the projection data was created. For more information about these parameters, see Computing Fan-Beam Projection Data.

The `ifanbeam`

function converts the fan-beam projection data to parallel-beam projection data with the `fan2para`

function, and then calls the `iradon`

function to perform the image reconstruction. For this reason, the `ifanfeam`

function supports certain `iradon`

parameters, which it passes to the `iradon`

function. See Inverse Radon Transform for more information about the `iradon`

function.

Computing Fan-Beam Projection Data | Working with Fan-Beam Projection Data |

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