Effective Dose: What It Is, and What It Isn’t

The concept of effective dose is widely used when addressing radiation dose in CT. Unfortunately, it is not always clearly understood, and it is often misused. Specifically, it is sometimes inappropriately applied to individual patient doses when in fact it is appropriate only for population-based dosimetry.

The concept was developed by the International Commission on Radiological Protection (ICRP 2007). The effective dose is estimated by first measuring the radiation dose, correcting the value to allow for differences in the types of radiation (x-rays, gamma rays, etc.), calculating the dose to individual organs, and then allowing for the different sensitivities of each organ to radiation. The result is usually expressed in millisieverts (mSv). The idea is that a dose of 1 mSv poses the same risk to...