Polygonal Phantoms - xcist/documentation GitHub Wiki

Polygonal File Format

Body phantoms are described in the NCAT NURB syntax, while lesion phantoms are described as mesh, triangular polygons. Several lesion phantoms can be described in a single file.

The polygonal mesh syntax is described as follows:

  • The file name starts with "tmod_" to indicate a mesh phantom
  • For each lesion model described in the file:
    • The first line describes the phantom object
    • The second line denotes the material (see Table 2: NCAT Materials, below)
    • The third line is an integer describing the total number of triangles that make up the phantom
    • Each line that follows consists of three sets of x,y,z coordinates that describe the three vertices of a triangle in three-dimensional space.

Example: the file "tmod_lung_lesion_8mm.nrb" describes six different lesion phantoms made up of muscle material: 8 mm-, 7 mm-, 6 mm-, 11 mm-, another 11 mm-, and another 6 mm-long lesion. The first six lines for the 8 mm and 7 mm phantoms are excerpted from "tmod_lung_lesion_8mm.nrb" below: the 8 mm is made up of 80,636 triangles, the 7 mm is made of 49,938 triangles:

tmod_lung_lesion_8mm
1
80636
-11.842316,12.247543,122.757446 -11.817810,12.261429,122.778320 -11.836731,12.230606,122.772827 
-11.836731,12.230606,122.772827 -11.817810,12.261429,122.778320 -11.845520,12.235504,122.801025 
-11.817810,12.261429,122.778320 -11.842712,12.252777,122.817139 -11.845520,12.235504,122.801025 
...

tmod_lung_lesion_7mm
1
49938
-69.139404,8.895981,126.426636 -69.155350,8.924042,126.414673 -69.183807,8.918701,126.470337 
-69.183807,8.918701,126.470337 -69.205612,8.875168,126.515503 -69.139404,8.895981,126.426636 
-69.155350,8.924042,126.414673 -69.194672,8.933533,126.446289 -69.183807,8.918701,126.470337 
...