The conformity index (CI) was first proposed in 1993 by the Radiation Therapy Oncology Group (RTOG) and described in Report 62 of the International Commission on Radiation Units and Measurements (ICRU). The conformity index, together with other evaluation indices, is a tool for analysis of a treatment plan during radiation therapy. These indices should be seen as complementary tools that attribute a score to a treatment plan or that can compare several treatment plans for the same patient. Though, the future of conformal index in everyday practice therefore remains unclear (Feuvret et al. 2006). Probably, the main reason is the unavailability of tools for calculating such indices in an ordinary way. Deviation can be notably occurred due to uncertainties while reading parameter values from a DVH diagram.
Recently, I developed an application (with ESAPI – Varian Eclipse Scripting API) for calculating several indices.

References:

Feuvret, Loïc; Noël, Georges; Mazeron, Jean-Jacques; Bey, Pierre (2006): Conformity index: A review. In International Journal of Radiation Oncology*Biology*Physics 64 (2), pp. 333–342. DOI: 10.1016/j.ijrobp.2005.09.028.