Question

The SI unit for measuring Equivalent Biologic Dose for radiation exposure is

• A. 'rem'
• B. 'gray'
• C. Roentgen
• D. Sievert

Hint:

- Absorbed Dose: Gray (SI) rad (traditional) [1 Gy = 100 rad].
- Biological Equivalent Dose: Sievert (SI) rem (traditional) [1 Sv = 100 rem].
- Radiation Exposure: Coulomb/kg (SI) Roentgen (traditional).

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
To assess radiation safety and dosimetry, different units are used to measure the physical, absorbed, and biological equivalent doses of ionizing radiation.

Step 2: Detailed Explanation:
Let us define and compare the units of radiation measurement listed in the options:
- Roentgen (C):
This is a traditional unit of radiation measurement that quantifies the exposure or ionization of air by X-rays or gamma rays.
- Gray (B):
This is the SI unit of absorbed dose, defined as the absorption of one joule of radiation energy per kilogram of matter ($1\text{ Gy} = 1\text{ J/kg}$).
It does not account for the varying biological damage caused by different types of radiation.
- rem (A):
This stands for "Roentgen Equivalent Man" and is the older, non-SI unit for measuring the Equivalent Biologic Dose.
It is calculated by multiplying the absorbed dose in rads by a quality factor ($QF$) specific to the type of radiation.
- Sievert (D):
This is the modern SI unit for measuring the Equivalent Biologic Dose (or Dose Equivalent).
It quantifies the biological effect of ionizing radiation on living tissues by multiplying the absorbed dose in Grays by a radiation weighting factor ($W_R$).
The relationship between the traditional and SI units is: $1\text{ Sv} = 100\text{ rem}$.

Step 3: Final Answer:
The SI unit for measuring the Equivalent Biologic Dose is the Sievert.