This article covers the following topics:

• Introduction
• Spatial Linearity of Pixel Size Verification
• CTP401 Module Target Spacing
• CTP404 Module Target Spacing
• CTP682 Module Target Spacing

Introduction

Spatial Linearity information is given for the following Catphan® models: 500, 503, 504, 600, and 700.

The spatial linearity is the reported estimated pixel spacing. The distance between the spatial targets is measured (the small Teflon and air plugs) and from the known distance the real pixel spacing is calculated.

Spatial Linearity of Pixel Size Verification

The spatial linearity is the reported estimated pixel spacing. The distance between the spatial targets is measured (the small Teflon and air plugs) and from the known distance the real pixel spacing is calculated.

The centers of the 3mm diameter holes are positioned 50mm apart. By measuring from center to center and comparing the result to the known distance, the spatial linearity of the CT scanner can be verified. 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 verified.

CTP401 Module Target Spacing

Figure 7.1: Drawing of the cross-sectional view of the CTP401 Module. The uncertainty of the dimensions shown is ±0.1 mm. Spatial linearity is measured in x and y axes. This module is found in the Catphan® 500. 
 

CTP404 Module Target Spacing

Figure 7.2: Drawing of the cross-sectional view of the CTP404 Module. The uncertainty of the dimensions shown is ±0.1 mm. Spatial linearity is measured in x and y axes. This module is found in the Catphan® 503, 504, and 600.

CTP682 Module Target Spacing

Figure 7.3: Drawing of the CTP682 Geometry and Sensitometry Module. Spatial linearity and pixel size is measured in the x-y directions using the center to center distance between holes. The CTP682 is found in the Catphan® 700.

Please note: The Teflon pin is used for identification and orientation only. The ability to change the Teflon pin position enables organizations with more than one Catphan® phantom to identify their phantoms by images of the first section.