Enter the volume of the target receiving the prescribed dose, the volume of the prescribed isodose, and the volume of the reference isodose into the calculator to determine the Conformity Index.

## Conformity Index Formula

The following formula is used to calculate the Conformity Index.

CI = Vt / (Vp * Vr)

Variables:

- CI is the Conformity Index
- Vt is the volume of the target receiving the prescribed dose (cm³)
- Vp is the volume of the prescribed isodose (cm³)
- Vr is the volume of the reference isodose (cm³)

To calculate the Conformity Index, divide the volume of the target receiving the prescribed dose by the product of the volume of the prescribed isodose and the volume of the reference isodose.

## What is a Conformity Index?

A Conformity Index is a quantitative measure used in radiation therapy to assess how well the radiation dose conforms to the target volume, such as a tumor, while sparing the surrounding healthy tissues. It is calculated by dividing the volume of the target receiving the prescribed dose by the volume of the prescribed dose itself. A perfect conformity index is 1, indicating that the radiation is precisely targeting the tumor with minimal exposure to healthy tissues.

## How to Calculate Conformity Index?

The following steps outline how to calculate the Conformity Index (CI).

- First, determine the volume of the target receiving the prescribed dose (Vt) in cm³.
- Next, determine the volume of the prescribed isodose (Vp) in cm³.
- Next, determine the volume of the reference isodose (Vr) in cm³.
- Finally, use the formula CI = Vt / (Vp * Vr) to calculate the Conformity Index.
- After inserting the values of Vt, Vp, and Vr into the formula, calculate the result.

**Example Problem:**

Use the following variables as an example problem to test your knowledge:

Volume of the target receiving the prescribed dose (Vt) = 50 cm³

Volume of the prescribed isodose (Vp) = 20 cm³

Volume of the reference isodose (Vr) = 10 cm³