Inaccurate table height setting affects the organ-specific radiation dose in computed tomography

Abstract

PurposeWe aimed to prove that the locally absorbed doses in tissues and organs are affected by inaccurate table height in computed tomography. Materials and MethodsWe compared the volume CT dose index (CTDIvol) and the absorbed doses using an anthropomorphic phantom combined with a breast phantom. The phantom was set at the gantry center, from which the table height was changed every 20 mm between–40 mm and 40 mm. Data acquisition was performed using auto table height correction (AHC) for each table height. The CTDIvol was obtained from the CT console and the tube current value for each image slice (DICOM tag: 0018, 1151). The absorbed dose was measured by a glass dosimeter that was implanted at various positions in the phantom. ResultsThe tube current values in the lung were lower at a table height of + 40 mm than those at other heights. The CTDIvol was slightly lower at + 40 mm than at the center (12.78 mGy vs. 13.42 mGy, p < 0.05). The CTDIvol values were almost the same at the other table heights (13.30–13.40 mGy). The absorbed doses at the lens and mammary gland were significantly different from those at the gantry center (−27.27%–17.77% and –24.31%–12.83%, respectively). Compared with the center, both the lens and mammary gland had higher absorbed doses at a table height of –40 mm. ConclusionThe absorbed dose was affected by the table height, but the CTDIvol was maintained by AHC. The operator should appropriately position patients even when using AHC.