BBTools

bbtomoemit

This function is not yet fully documented. This is a transcript of the text-formatted help.

bbtomoemit  Create a black-box model of an emission tomograph.
   [BB,DIM2]=bbtomoemit(DIM,THETA) extends bbradon with several effects
   found in physical emission tomographs.

   While the Radon transform posses a 180-degree symmetry around the
   center, this is not true when additional effects are included.
   Therefore, the default value for THETA is [0:5:355].

   Generally, the effects depends on the distance of the PLs to the
   center. This is not an issue for the Radon transform, where LORs
   never diverge. Together the distance and the angle of the PLs
   describe an orbit.

   Points falling outside a PL, or one that can not be projected because
   a PL is too short to contain it, is disregarded in the transform. By
   default, each projection line is located at a constant distance so the
   corners of the image touches a PL.

   In addition to the options in bbradon, the following are availabl:
     'dist': provides either a distance for all the planes, or a vector
             with a distance for each plane projection.
     'roi':  The ROI may be an image or one of the following strings:
               'all': use the largest possible ROI
               'sym': same, except the ROI is limited by symmetry
     'div':  Collimator divergence, in degrees. A point on a projection is
             sensitive to all points in the image whose angle to the LOR is
             less than DIV. Large angles implies resolution is lost quickly
             with depth.
     'att':  Attenuation factor. A point at depth D is multiplied by
             exp(-D*ATT) before the projection.
     'body': Body of attenuation, the shape of the attenuating solid.
             This can be specified as vertices of a polygon as a matrix
             with a X- and Y-coordinate per row. It may also be an image
             of dimension DIM, where non-zero pixels are inside the body
             (default: ROI).

   NOTE: Only constant attenuation for convex polygons are supported.
   The body is the convex hull of the specified point set.

   The struct OPT2 contains the above fields with the true values used,
   as well as the following informational fields:
     'body': As input, but guaranteed returned as points.

   Limitation: bbtomoemit assumes the projection planes are sampled
   equidistantly. Thus, it does not adequatedly model the geometric
   in a PET scanner.

   See also bbradon, bbfbp,  (image toolbox).

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