Figure 1: A screenshot of "Dose Report" showing three series of a pelvic CT scan, scan range, CT dose index (mGy), dose linear product (DLP, mGy-cm). A total exam DLP is automatically calculated (in yellow circle). From the DLP, we can calculate an effective dose by multiplying it with an E/DLP conversion coefficient. The conversion coefficients vary from one area to another. Figure 2: A table showing E/DLP conversion coefficients of five body regions, and typical mean effective doses and dose ranges from an investigation performed in British Columbia, Canada in 2004.
In our example, the total DLP was 555.78, and it was a pelvic CT scan (conversion coefficient = 0.019).
Effective dose (mSv) = DLP x E/DLP conversion coefficient
= 555.78 x 0.019
Reminder: Natural effective dose of radiation received by general population = 3-4 mSv per year
Another option to calculate an effective dose and cancer risk is to do it online, for example, a website www.XrayRisk.com
1. Aldrich JE, Bilawich A, Mayo JR. Radiation doses to patients receiving computed tomography examinations in British Columbia. Can Assoc Radiol J 2005;57:79-85.
2. European Commission. European guidelines on quality criteria for computed tomography. EUR 16262 EN. Luxembourg: Office for Official Publication of the European Communities; 2000.