In an adult, the radiation exposure from a typical abdominal CT examination is approximately the same as 400 posteroanterior chest radiographs.
Radiation Dose Comparisons
| Source of radiation exposure | Diagnostic Procedure | Typical Effective dose (mSv) |
|---|---|---|
| Radiography and fluoroscopy | Hand radiograph | <0.01 |
| Dental bitewing radiograph | <0.01 | |
| Chest radiograph (Posteroanterior) | 0.02 | |
| Mammogram | 0.4 | |
| Lumbar spine radiograph | 1.5 | |
| Barium enema | 8 | |
| Fluoroscopic coronary angiogram | 7 | |
| Computed tomography | Head CT | 2 |
| Chest CT | 7 | |
| Abdomen CT | 8 | |
| Pelvis CT | 6 | |
| Coronary artery calcification CT | 3 | |
| Coronary CT angiogram | 16 | |
| Radionuclide imaging | Lung scan | 2 |
| Bone scan | 4 | |
| Myocardial perfusion imaging | 14 | |
| Naturally occurring sources of ionizing radiation (eg, cosmic rays or radon gas) | 1.3-9.6 (US average=3.0) | |
| Maximum allowable annual occupational dose to radiation workers | 50 (US) |
Although exact exposures will vary according to patient size, type of equipment used, and operator expertise, typical radiation doses for common radiographic studies are shown above. As stated above, a CT of the abdomen provides a radiation dose 400 times that of the typical posteroanterior chest radiograph. That is 8 mSv for abdominal CT divided by 0.02 mSv for anteroposterior chest XR.
“The effective doses from diagnostic CT procedures are typically estimated to be in the range of 1 to 10 mSv. This range is not much less than the lowest doses of 5 to 20 mSv estimated to have been received by some of the Japanese survivors of the atomic bombs. These survivors, who are estimated to have experienced doses slightly larger than those encountered in CT, have demonstrated a small but increased radiation-related excess relative risk for cancer mortality.
The risk of developing cancer as a result of exposure to radiation depends on the part of the body exposed, the individual’s age at exposure, and the individual’s gender. For the purpose of radiation protection, a conservative approach that is generally used is to assume that the risk for adverse health effects from cancer is proportional to the amount of radiation dose absorbed and that there is no amount of radiation that is completely without risk. This conservative approach is called the “linear non-threshold” model” FDA.gov (see link below)
Reference
https://www.fda.gov/radiation-emittingproducts/radiationemittingproductsandprocedures/medicalimaging/medicalx-rays/ucm115329.htm
US Food and Drug Administration: What are the radiation risks from CT? 2017
https://www.ncbi.nlm.nih.gov/pubmed/26434964
Mayo Clin Proc. 2015;90(10):1380-92. http://www.mayoclinicproceedings.org/article/S0025-6196(15)00591-1/fulltext