Purpose: To verify the influence of the software version of the dose control system on the equivalent dose and effective dose calculation values. Methods: We performed chest CT and liver to pelvic CT imaging with a human phantom placed on a CT bed. After the imaging was completed, the radiation dose structured reports (RDSRs) generated by the equipment were transferred to several dose management systems with different software versions for equivalent dose and effective dose calculations. Results: The equivalent and effective doses calculated from the same RDSR differed depending on the software version of the dose management system with a difference of approximately 2 times for the effective dose and up to 50 times for the equivalent dose. Conclusion: It is considered that the voxel phantom geometry and dose calculation algorithm may differ depending on the software version of the dose management system. Careful attention should be paid in handling the dose calculation values because the exposure explanations and risk assessments using the equivalent doses, and effective dose calculated by the dose management systems may be overestimated.

To compare the computed tomography (CT) number and the radiation dose between the 64 (group A) and 80-detector row (group B) during lower extremity computed tomography angiography (LE-CTA). We enrolled 144 patients underwent LE-CTA and compared the CT number for the popliteal arteries, radiation dose and the rate of the optimal CT number during the LE-CTA exceeding 200 HU between the two groups. The CT number for the popliteal arteries and mean dose-length product was significantly higher in Group A than in Group B (P < 0.01). The rate of the optimal CT number for the popliteal arteries was 23.6% with Group B scanner and 56.9% with Group A (P < 0.05). The 64-detector row CT was significantly higher in the CT number for the popliteal arteries, radiation dose and rate of the optimal CT number during the LE-CTA than the 80-detector row. Depiction ability did not improve by using a high CT scanner with a wider detector during LE-CTA.

It is not easy to measure the half-value layer (HVL) of CT because it is necessary to place the X-ray tube position fixed. The aim of this study was to experiment the new methods of HVL measuring of CT using a custommade lead slit. The custom-made lead slit method allowed the HVL measuring of CT while the rotation of the X-ray tube. The error of HVL value using the custom-made lead slit method compared to the conventional method was within 6%. The custom-made lead slit method can enable to measure the HVL of CT easily without the X-ray tube position fixed.