2020 Volume 58 Issue 4 Pages 331-341
The purpose of this study is to understand the radiation exposure per examination by incident air kerma (Ka, i) by employing the Numerical Dose Determination (NDD) method of population-based gastric cancer screening and examine whether it will be an appropriate index for the formulation of diagnostic reference levels (DRL).
First, we measured the reference air kerma rate and air kerma at the patient entrance reference point by using the X-ray television fluoroscope, which can calculate the dose by NDD method. Thereafter, we compared the obtained values with those of the calibrated dosimeter. The difference in values obtained by NND method and from the calibrated dosimeter were 1.5% and 10.5%, respectively, thereby confirming the accuracy.
Second, we recorded the fluoroscopy time and Ka, i of the 750 examinees, who underwent gastric opportunistic screening in our institution. The median value of Ka, i was 64.2 mGy, and the value of entrance surface dose for standard body size was 84.8 mGy. We found positive correlations between the fluoroscopy time and Ka, i (r = 0.6, P < 0.001), and between Ka, i and estimated incident air kerma of calculated reference air kerma rate (r = 0.66, P < 0.001).
We suggest that the standard patient exposure for gastrography can be inferred by measuring the reference air kerma rate and air kerma at the patient entrance reference point.
