Difference Between Roentgen and Sievert

The key difference between Roentgen and Sievert is that Roentgen is the unit of measurement of the exposure to ionizing radiation, whereas Sievert is the unit of the health effect of ionizing radiation.

Roentgen and Sievert are units of measurement of properties regarding ionizing radiation. The symbol for Roentgen unit is R, and it belongs to the Legacy unit system while the symbol for the Sievert unit is Sv, and it belongs to the SI derived unit system.

CONTENTS

1. Overview and Key Difference
2. What is Roentgen 
3. What is Sievert 
4. Side by Side Comparison – Roentgen vs Sievert in Tabular Form
5. Summary

What is Roentgen?

Roentgen is the unit of measurement of the exposure to ionizing radiation. The symbol for this unit is R. In this measurement, ionizing radiation mainly refers to X-rays and gamma rays. We can define it as the electric charge freed by such radiation in a specified volume of air divided by the mass of that air: coulomb per kilogram. The unit system to which this unit belongs to is the Legacy unit. The Roentgen unit was named after the scientist Wilhelm Roentgen. He was the scientist who discovered X-rays.

The development of the Roentgen unit was a major step forward in standardizing radiation measurement, but the main disadvantage of Roentgen is that it’s only a measure of air ionization. In other words, it is not a direct measure of radiation absorption in other materials such as different forms of human tissue.

What is Sievert?

Sievert is the unit of measurement of the health effect of ionizing radiation. The symbol for this unit is Sv. It is a derived unit of ionizing radiation dose in the SI unit system, and it measures the health effect of low levels of ionizing radiation on the human body. This unit was named after the scientist Rolf Maximillian Sievert.

We can use the unit Sievert for radiation dose quantities such as equivalent dose and effective dose. These doses represent the risk of external radiation from sources outside the body and the committed dose that represent the risk of internal irradiation due to inhaled or ingested radioactive substances. The unit Sievert is intended to represent the stochastic health risk, for radiation dose assessment, which is defined as the probability of radiation-induced cancer and genetic damage.

However, the unit Sievert is not used for dose rates of radiation that produce deterministic effects, which refer to the severity of acute tissue damage that is certain to happen. E.g. acute radiation syndrome. We can compare these effects to the physical quantity absorbed dose measured by the unit Gray (Gy).

What is the Difference Between Roentgen and Sievert?

Roentgen and Sievert are units of measurement of properties regarding ionizing radiation. The key difference between Roentgen and Sievert is that Roentgen is the unit of measurement of the exposure to ionizing radiation, whereas Sievert is the unit of the health effect of ionizing radiation. Moreover, the symbol for Roentgen unit is R, and it belongs to the Legacy unit system while the symbol for the Sievert unit is Sv, and it belongs to the SI derived unit system.

Below tabulation summarizes the difference between Roentgen and Sievert.

Summary – Roentgen vs Sievert

Roentgen and Sievert are units of measurement of properties regarding ionizing radiation. The key difference between Roentgen and Sievert is that Roentgen is the unit of measurement of the exposure to ionizing radiation whereas Sievert is the unit of the health effect of ionizing radiation.

Reference:

1. “Sievert.” Sievert – an Overview | ScienceDirect Topics, Available here.
2. “Roentgen.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 6 Feb. 2019, Available here.

Image Courtesy:

1. “Dosimeter ablesung” By Wusel007 – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “展望の宿 天神 2016 (26182596995)” By Haruhiko Okumura – 展望の宿 天神 (CC BY 2.0) via Commons Wikimedia