How the Software Computes the Conformity Index
The CI and GI are computed by evaluating the dose in the PTV ① plus a normal tissue expansion ring ②. The size of the expansion is 30 mm by default.
The software examines the dose at the border of the normal tissue ring. If the 50% or 100% isodose line is inside the normal tissue ring, the software can compute the respective conformity index ③. If the 50% and/or 100% isodose line is no longer inside the PTV volume and normal tissue ring, the software cannot compute the respective CI/GI ④. If the isodose is exceeded for at least one of the points on the border of the normal tissue ring, the software displays N/A. The volume averaged conformity indices will be n/a if the index of at least one of the PTVs is n/a.
If none of the PTV voxels reach the prescription dose, the software displays – – for the conformity indices.