Question 1

What is the difference between absorbed and effective dose?

Accepted Answer

Absorbed dose (Gy/rad) measures raw energy deposited in tissue. Effective dose (Sv/rem) accounts for radiation type and organ sensitivity. Effective dose is used for radiation protection.

Question 2

What is a Sievert?

Accepted Answer

The Sievert is the SI unit of effective dose. 1 Sv = 100 rem. Annual background radiation is about 2.4 mSv. Occupational limit is 20 mSv/year in most countries.

Question 3

How dangerous is medical radiation?

Accepted Answer

A chest X-ray delivers about 0.1 mSv - similar to a few days of natural background radiation. CT scans deliver about 10 mSv. Medical doses are weighed against diagnostic benefits.

Question 4

What is the Gray (Gy)?

Accepted Answer

The Gray is the SI unit of absorbed dose: 1 Gy = 1 joule per kilogram. Used primarily in radiation therapy. 1 Gy = 100 rad. For photon radiation, 1 Gy approximately equals 1 Sv.

Question 5

What is background radiation?

Accepted Answer

Background radiation (~2.4 mSv/year global average) comes from cosmic rays, radon gas, and natural radioactive materials in food and water. This is not considered harmful.

Gy	1
mGy	1000
μGy	1.00000e+6
rad	100
erg/g	10000

Sv	0.001
mSv	1
μSv	1000
nSv	1.00000e+6
rem	0.1
mrem	10

Background radiation (annual avg)	2.4 mSv/year
Dental X-ray	0.005 mSv
Chest X-ray	0.1 mSv
Mammogram	0.4 mSv
Flight (transatlantic)	0.08 mSv
Abdominal CT scan	10 mSv
Radiation therapy (total)	20–80 Sv (to tumor)
Annual occupational limit	20 mSv/year

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