Whole-body CT in polytrauma patients: effect of arm positioning on thoracic and abdominal image quality

The purpose of this study is to assess the influence of different arm positioning techniques on thoracic and abdominal image quality and radiation dose of whole-body trauma CT (wbCT). One hundred and fifty polytrauma patients (104 male, mean age 47 ± 19) underwent wbCT with arms elevated above the head (group A, n=50), alongside the abdomen (group B, n=50), and on a pillow ventrally to the chest with both arms flexed (group C, n=50). Two blinded, independent observers measured image noise and rated image quality (scores 1-3) of the liver, aorta, spleen, spine, and lower lungs. Radiation dose parameters were noted, and the abdomens' anterior-posterior diameter and scan lengths were measured. Interreader agreements for image noise (r=0.86; p<0.001) and subjective image quality (k=0.71-0.84) were good. Noise was lower (p<0.05), image quality of the liver, aorta, spleen, and spine was higher, and radiation dose lower in group A than in groups B and C (p<0.001, each). Image quality of the spleen, liver, and aorta were higher in group C than in group B (p<0.05, each). No significant differences in scan length (p=0.61) were found among groups. Abdominal anterior-posterior diameter correlated significantly with noise (r=0.82; p<0.01) and dose (r=0.47; p<0.001). Estimated effective radiation doses were significantly (p<0.001) higher in groups B (21.2 mSv) and C (21.9 mSv) as compared to A (16.1 mSv). In wbCT for polytrauma patients, positioning of the arms above the head results in better image quality and lower radiation dose. Placing the flexed arms on a large pillow ventrally to the chest significantly improves image quality as compared to positioning alongside the abdomen.