Background Radiation (Rad Tech Guide)

To provide perspective on the radiation dose that is given during diagnostic imaging exams we will discuss the fact that everyone receives radiation throughout the course of their lives.

For the text version with tables and diagrams please see our post: https://howradiologyworks.com/x-ray-c...

This radiation source is often referred to as background radiation and everyone gets this background radiation.

Chapters:
00:00 Background radiation vs Imaging Dose
02:08. Cosmic Radiation Radiation Dose
04:55. Radon Radiation Dose
05:42. All Radiation Sources in United States
07:13 Radiation dose for adominal imaging
08:52. Radiation dose for Bone imaging and Extremity Imaging
09:52 Radiation dose for Head and Neck Imaging
10:20. Radiation dose for Chest and Lung Imaging
10:45. Radiation dose for Cardiac CT
11:45 Radiation dose for Mammography
12:00 Radiation dose for PET imaging (Positron Emisson Tomography)
12:30 Summary imaging radiation dose vs background radiation

In addition to background radiation the most common other sources of radiation exposure are: at work (i.e. occupational exposure), and radiation exposure from medical exams.

The average background radiation in the United States is 3 mSv.
Just as the background radiation dose varies throughout the US there is also significant variance in the radiation dose for different diagnostic exams.

Below are some examples of the representative radiation doses of different types of exams and a comparable time of background radiation.

These radiation doses are from the RSNA (Radiologic Society of North America). We first summarize the results with two infographics, one for x-ray and one for CT.

Abdominal Imaging
CT of abdomen and pelvis corresponds to about 10 mSv of radiation dose which corresponds to about three years of background radiation (10/3=3.333). If there is a need for a repeated scan with and without contrast, this received dose corresponds to about four years of background dose (20/3=6.667)

Procedure Approximate Effective Dose Comparable Time of Background Radiation
CT – Abdomen and Pelvis 10 mSv 3 years
CT – Abdomen and Pelvis (w/ and w/out contrast) 20 mSv 7 years
CT- Colonography 6 mSv 2 years
Intravenous Pyelogram (IVP) 3 mSv 1 year
Barium Enema (Lower GI X-ray) 8 mSv 3 years
Upper GI Study with Barium 6 mSv 2 years
On average CT colonography exposes patient to about 6 mSv of radiation, which is approximately two years of background radiation. In abdominal imaging, the representative averages dose of each procedure varies between one and three years of equivalent background radiation.

Bone Imaging
In standard x-ray radiography procedures of bone imaging, the dose is quite low, around 0.001 mSv. This corresponds to about three hours of background radiation in the United States.

Bone densitometry (which uses dual energy x-ray scanning) corresponds to about three hours of background radiation and spine x-rays correspond to about six months of background radiation.

Procedure Approximate Effective Dose Comparable Time of Background Radiation
Extremities X-ray (hand, foot, etc) 0.001 mSv 3 hours
Bone Densitometry (DEXA) 0.001 mSv 3 hours
Spine X-ray 1.5 mSv 6 months
Head and Neck
In case of a standard non-contrast head CT scan it is about 2 mSv or eight months of background radiation. A head CT, if you do it with and without a contrast is about 4 mSv. That’s about 16 months of background radiation

Procedure Approximate Effective Dose Comparable Time of Background Radiation
Head CT 2 mSv 8 months
Head CT (w/ and w/out contrast) 4 mSv 16 months
Spine CT 6 mSv 2 years
Chest
Then in the chest, for chest CT, about 7 mSv, so that’s a little bit more than two years. A lung CT for screening, 1.5 mSv or lower, which corresponds to about six months of background radiation.

Chest x-ray gives patients an equivalent of about ten days of background radiation dose.

Procedure Approximate Effective Dose Comparable Time of Background Radiation
Chest CT 7 mSv 2 years
Lung CT (Screening) 1.5 mSv 6 months
Chest X-ray 0.1 mSv 10 days
Cardiac CT Imaging Doses
The doses for cardiac CT depend strongly on the type of equipment which is used for imaging.


Coronary CTA 12 mSv 4 years
Ca Scoring CT 3 mSv 1 year
In modern scanners the achievable doses are much lower for cardiac CT.

Then a calcium scoring exam would be about 3 mSv. Again this can often be lower on a modern scanner. This corresponds to about one year of background radiation.

Mammography Imaging Doses
Mammography, has quite low radiation dose, about 0.01 mSv or about three hours of background radiation dose.

Mammography 0.01 mSv 3 hours
PET/CT Imaging Doses
Then finally, we list the approximate dose of a PET/CT scan (Positron Emission Tomography). The radiation dose there is a little bit higher than the other standard diagnostic scans, about 25 mSv,

Procedure Approximate Effective Dose Comparable Time of Background Radiation
PET/CT 25 mSv 8 years