回复：背景资料：多大辐射会危害健康？

来源: 歌唱家 于 2011-03-15 07:54:06 [] [旧帖] [给我悄悄话] 阅读数 : (8528 bytes)
回答: 背景资料：多大辐射会危害健康？ 由 7.5 于 2011-03-15 07:29:59

Naturally-occurring "background" radiation exposure

We are exposed to radiation from natural sources all the time. The average person in the U.S. receives an effective dose of about 3 mSv per year from naturally occurring radioactive materials and cosmic radiation from outer space. These natural "background" doses vary throughout the country.

People living in the plateaus of Colorado or New Mexico receive about 1.5 mSv more per year than those living near sea level. The added dose from cosmic rays during a coast-to-coast round trip flight in a commercial airplane is about 0.03 mSv. Altitude plays a big role, but the largest source of background radiation comes from radon gas in our homes (about 2 mSv per year). Like other sources of background radiation, exposure to radon varies widely from one part of the country to another.

To explain it in simple terms, we can compare the radiation exposure from one chest x-ray as equivalent to the amount of radiation exposure one experiences from our natural surroundings in 10 days.

Following are comparisons of effective radiation dose with background radiation exposure for several radiological procedures described within this website:

For this procedure: * Your approximate effective radiation dose is: Comparable to natural background radiation for: ** Additional lifetime risk of fatal cancer from examination:
ABDOMINAL REGION:
Computed Tomography (CT)-Abdomen and Pelvis 15 mSv 5 years Low
Computed Tomography (CT)-Abdomen and Pelvis, repeated with and without contrast material 30 mSv 10 years Moderate
Computed Tomography (CT)-Colonography 10 mSv 3 years Low
Intravenous Pyelogram (IVP) 3 mSv 1 year Low
Radiography (X-ray)-Lower GI Tract 8 mSv 3 years Low
Radiography (X-ray)-Upper GI Tract 6 mSv 2 years Low
BONE:
Radiography (X-ray)-Spine 1.5 mSv 6 months Very Low
Radiography (X-ray)-Extremity 0.001 mSv 3 hours Negligible
CENTRAL NERVOUS SYSTEM:
Computed Tomography (CT)-Head 2 mSv 8 months Very Low
Computed Tomography (CT)-Head, repeated with and without contrast material 4 mSv 16 months Low
Computed Tomography (CT)-Spine 6 mSv 2 years Low
CHEST:
Computed Tomography (CT)-Chest 7 mSv 2 years Low
Computed Tomography (CT)-Chest Low Dose 1.5 mSv 6 months Very Low
Radiography-Chest 0.1 mSv 10 days Minimal
DENTAL:
Intraoral X-ray 0.005 mSv 1 day Negligible
HEART:
Coronary Computed Tomography Angiography (CTA) 16 mSv 5 years Low
Cardiac CT for Calcium Scoring 3 mSv 1 year Low
MEN'S IMAGING:
Bone Densitometry (DEXA) 0.001 mSv 3 hours Negligible
WOMEN'S IMAGING:
Bone Densitometry (DEXA) 0.001 mSv 3 hours Negligible
Mammography 0.4 mSv 7 weeks Very Low

Note for pediatric patients: Pediatric patients vary in size. Doses given to pediatric patients will vary significantly from those given to adults.

* The effective doses are typical values for an average-sized adult. The actual dose can vary substantially, depending on a person's size as well as on differences in imaging practices.

** Legend:

 Risk Level 
 Approximate additional risk of fatal cancer for an adult from examination:
Negligible:
 less than 1 in 1,000,000
Minimal:
 1 in 1,000,000 to 1 in 100,000
Very Low:
 1 in 100,000 to 1 in 10,000
Low:
 1 in 10,000 to 1 in 1000
Moderate:
 1 in 1000 to 1 in 500
Note: These risk levels represent very small additions to the 1 in 5 chance we all have of dying from cancer.
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