Phantom Laboratory Catphan 503 - Circular Symmetry and Spatial Linearity; Spherical Acrylic Contrast Targets

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Circular symmetry of display system
The circular phantom sections are used to test for circular symmetry of the CT image,
including calibration of the CT display system. If an elliptical image is produced, the x-y
balance of the image display system should be adjusted.
Measuring spatial linearity in x and y axes.
Spatial linearity of pixel size verication
This section has four holes (one with a Teon pin). These 3mm diameter holes are
positioned 50mm on center apart. By measuring from center to center the spatial
linearity of the CT scanner can be veried. Another use is to count the number of pixels
between the hole centers, and by knowing the distance (50mm) and number of pixels, the
pixel size can be veried.
The Teon pin is used for identication and orientation only. The ability to change the
Teon pin position enables organizations with more than one Catphan® phantom to
identify their phantoms by images of the rst section.
Spherical acrylic contrast targets
The section has ve acrylic spheres located in a 30mm diameter circular pattern. These
spheres are used to evaluate the scanner’s ability to image volume averaged spheres.
The sphere diameters are 2, 4, 6, 8, and 10mm.