Homogeneity Index: An objective tool for assessment of conformal radiation treatments

Retrospective study of 99 plans comparing five homogeneity index formulas. Its introduction summarizes the RTOG index (maximum isodose in the target ÷ reference isodose), D5%/D95%, and (D2% − D98%) ÷ prescribed dose, and explains that D2% and D98% are used because true point maximum and minimum doses are sensitive to calculation grid size and placement. Full text read in Europe PMC (PMC3532749).

A readable, open-access walk through the different homogeneity index formulas — RTOG, D5%/D95%, (D2% − D98%)/prescription — and why near-maximum and near-minimum doses replace point doses.