[en] Skin injury in patients due to radiation exposure has been a complication in percutaneous coronary intervention (PCI) for a long time. To the best of our knowledge, there have been no reports comparing radiation dose by treatment area with diagnostic reference levels (DRLs) 2020, although the radiation dose varies by treatment area in PCI. In this study, the treatment areas were classified into four segments (i.e., AHA no. 1-3, AHA no. 4, AHA no. 5-10, and AHA no. 11-15), and each segment was compared with DRLs 2020. This retrospective study included 984 consecutive patients with single-vessel disease and non-chronic total occlusion. PCI was performed on a single device. The median radiation dose was 1640.8 mGy, and the radiation dose for AHA no. 4 was 2732.0 mGy, which was significantly higher than the other treatment areas (p<0.001). In AHA no. 4, the radiation dose increased due to the heavy use of the left cranial view, and the patient background contributed to the increased lesion complexity. Therefore, it was challenging to evaluate AHA no. 4 and the other treatment areas with a uniform DRL value. Establishing a subdivided index for each treatment area is crucial if DRLs are used as a reference during procedures and as a guide for dose optimization. (author)