Relationship between radiation dose indices and patient size in adult brain computed tomography

The relationship between radiation dose indices and patient size was investigated in adult brain CT scans to assess the significance of considering the patient size for radiation dose management. Two hundred patients who underwent brain CT using automatic exposure control were enrolled. The radiation dose indices (volume CT dose index, CTDIvol; size-specific dose estimate, SSDE; dose length product, DLP) were compared with the head size indices (effective diameter, ED; water-equivalent diameter, WED) and body weight. The CTDIvol and SSDE correlated positively with the ED and WED. The correlations were higher for the WED than the ED and for the CTDIvol than the SSDE. Although the DLP also correlated positively with the ED and the WED, the correlations were lower than those for the CTDIvol and the SSDE. The CTDIvol and SSDE showed significant positive correlations with body weight, but the correlations were lower than those for the ED. In conclusion, the radiation dose indices in adult brain CT correlate with the head size indices. Consideration of the head size indices is recommended for radiation dose management in brain CT. The relationship between the radiation dose indices and body weight may be of some significance when the head size indices are not readily available.