Zhen Xu, Hongrong Xu, Daisong Liu, Jiawen Zhao, Bo Liu, Jinhua Cai
For toddler chest CT, arms fully elevated is the optimal position. Arms alongside the body is an acceptable alternative when elevation is unfeasible. Humeral superimposition over the shoulders should be avoided whenever possible, as it increases radiation dose and degrades image quality.
PURPOSE: To investigate the effects of different arm positions on image quality and radiation dose in toddler chest computed tomography (CT).
METHODS: A phantom experiment and a retrospective clinical study were conducted. In the phantom study, an anthropomorphic phantom was scanned 10 times in three arm positions: arms fully elevated (Group A), arms incompletely elevated with humeri superimposed over shoulders (Group B), and arms alongside the body (Group C). In the clinical study, 120 patients aged 12-36 months were categorized into corresponding groups (Groups 1-3; n = 40 each). Objective image quality was assessed by CT attenuation and noise within predefined regions of interest (ROIs). Subjective quality was scored by two radiologists using a 5-point Likert scale. Radiation dose [volume computed tomography dose index and dose-length product (DLP)] was recorded.
RESULTS: Arm position significantly affected CT values and noise in the phantom study, though noise differences were modest. In patients, only one ROI showed a significant noise difference [4.30 HU, 95% confidence interval (95% CI): 0.91-7.69]. Subjective scores were highest for Group 1, lowest for Group 2, and intermediate for Group 3; all images remained diagnostically adequate. Group 2 exhibited the highest radiation dose. Although the DLP difference between Groups 1 and 3 did not reach statistical significance after correction for multiple comparisons (adjusted p = 0.063), the point estimate suggested a numerical trend toward lower DLP in Group 1 (Hodges-Lehmann median difference: 1.80 mGy·cm; unadjusted 95% CI: 0.53-3.63).
CONCLUSION: For toddler chest CT, arms fully elevated is the optimal position. Arms alongside the body is an acceptable alternative when elevation is unfeasible. Humeral superimposition over the shoulders should be avoided whenever possible, as it increases radiation dose and degrades image quality.