Are X-rays safe?

Are X-rays safe?

 

Prepared by Dr Alex Ching

Version: 20170618

 

 

RADIATION IS NATURAL

 

The small dose of diagnostic irradiation is just a very minor addition to the underlying risks of having cancer in our lifetime. For all of us as adults, our risk of getting cancer in our lifetime is 1 out of 3-4 anyway, even we have never undergone any X-ray checking. Therefore, the theoretical increased risk should not be of major concern to us.

 

We obey ALARA (As Low As Reasonably Achievable) principle and we have been well- trained to use the appropriate amount of radiation necessary for a proper medical imaging examination. As with other medical procedures, X-rays are safe when used with care.

 

CONCEPT OF BERT (Background Equivalent Radiation Time)

 

 

Examination / Event

Radiation dose (mSv*)

Time required for the same dose of radiation to be released from our normal living environment

No. of CXR with equivalent dosage

Radiation in our normal living environment

3

1 year

40

8 hours continental flight (e.g. HK to Shanghai)

0.08

1 week

1

Intercontinental flight (e.g. HK to NY)

1

4 months

15

Smoking

45** (one pack per day)

15 year

600

 

 

 

 

HEAD & NECK

Intraoral X-ray

0.005

1 day

<1

CT Brain

2

8 months

25

CT Brain plain & contrast

4

1.5 year

50

CT Neck

6

2 years

75

 

 

 

 

CHEST & HEART

 

 

 

Chest X-ray

0.08

1 week

1

CT Thorax (low dose)

1.5

6 months

20

CT Thorax

7

2.5 years

90

CT Calcium Score

3

1 year

40

CT Coronary Angiogram

12

4 years

150

 

 

 

 

ABDOMEN AND PELVIS

Pelvic X-ray

1

4 months

15

IVU

3

1 years

40

Upper GI series

4.5

1.5 year

60

Lower GI series

6

2 years

75

CT Colon

6

2 years

75

CT Urogram

5.2

2 years

75

CT Abdomen and pelvis (plain)

10

3.5 years

125

Abdomen CTA

20

7 years

250

 

 

 

 

PET AND NUCLEAR MEDICINE

PET / CT

25

8.5 years

310

Bone Scan (Tc-99m MDP, 25 mCi)

7.4

2.5 years

90

Thyroid Scan (Tc-99m Pertechnetate, 5 mCi)

2.4

10 months

30

Renal Scan (Tc-99m MAG3, 8 mCi)

1.2

5 months

15

Cardiac Perfusion (Tc-99m Sestamibi, 35 mCi)

11

4 years

150

Myocardial Viability (TL-201 Chloride, 3 mCi)

25.5

8.5 years

320

 

 

 

 

BONE

DEXA (Bone Densitometry)

0.001

3 hours

<1

X-ray Spine

1.5

6 months

20

X-ray Extremity

0.001

3 hours

<1

CT Spine

6

2 years

75

 

 

 

 

WOMEN IMAGING

Mammogram

0.4

7 weeks

7

 

 

 

 

OTHERS

Cardiac catherization

10

3.5 years

125

Coronary angioplasty / stenting

20

7 years

250

 

Remarks: * scientific unit of measurement for radiation dose; ** projected estimation

Notes: This chart simplifies a highly complex topic for patient’s informational use. The effective doses are typical values for an average-sized adult. Doses for Paediatric patients vary in accordance with their body sizes. They are significantly different from those given to adults.

 

ACTIVITIES WITH 1 CHANCE IN 1,000,000 FATAL CONSEQUENCE

 

Smoking 1.4 cigarettes (lung cancer)

Eating 40 tablespoons of peanut butter (aflatoxin poisoning)

Eating 100 charcoal boiled BBQ goose (carcinogenic substances produced by grilling)

Spending 2 days in the main streets in Causeway Bay (air pollution)

Driving 40 miles in a car (automobile accident)

Flying 2,500 miles in a commercial jet (crash)

Padding a canoe for 6 miles (drowning)

Receiving 0.1 mSv radiation dose (cancer)                                 

 

RADIATION DOSE AND GENERAL EFFECTS

 

Radiation Dose (mSv)

General Effects

10,000

Radiation sickness with death in several weeks

1,000

Intermediate radiation sickness; Unlikely to cause death

100-1,000

Dose-related risk of developing cancer

50

Increased cancer risk according to statistics (Highest dose allowed annually for occupational exposure)

20

Maximum dose allowed for radiation workers over a 5-years period

1.5-3

Annual radiation dose from our normal living environment

 

 

Further Reading:

  1. Lancet. 2004; 363; 345-351
  2. RadiologyInfo.org www.pedrad.org/associations/5364/ig/index.cfm.
  3. Society of Nuclear Medicine Procedure Guideline, USA.
  4. Radiation Dose to Adults from Common Imaging Examinations, The American College of Radiology, June 2017