Body composition evaluation with computed tomography: Contrast media and slice thickness cause methodological errors.

Abstract

OBJECTIVE\nAlthough computed tomography (CT) is frequently used to determine body composition, the effects of using different CT protocols is not well known. The aim of this study was to determine whether contrast media phase, radiation dose, and slice thickness in CT affect body composition segmentation.\n\n\nMETHODS\nClinically indicated perfusion CTs of the upper abdomen in 20 patients (seven women) between 40 and 87 y of age with high suspicion of hepatocellular carcinoma were analyzed retrospectively. Axial images from the L3 level with varying imaging delay were reconstructed after contrast media injection (18 images per patient), slice thickness (5 images, 2-10 mm), and radiation dose (4 images with one-third to four-thirds of standard dose). Muscle and fat areas were segmented semiautomatically by drawing regions of interests and using established cutoff thresholds. Skeletal muscle index (SMI), steatotic muscle area, and adipose tissue index, as well as muscle attenuation and fat attenuation, were evaluated.\n\n\nRESULTS\nAverage SMI increased by up to 2.8% after contrast media injection. Steatotic muscle area decreased by ≤13.8%, and adipose tissue index decreased by ≤6.5%. Muscle attenuation increased after contrast media injection, whereas fat attenuation decreased (all P < 0.001). SMI decreased by 1.9% on average when increasing slice thickness from 2 to 10 mm. Steatotic muscle area increased by ≤3.3%, and adipose tissue index increased by ≤1.5% (all P < 0.05). Muscle attenuation did not change significantly with reconstruction thickness. Radiation dose had no effect on estimated area of spinal muscle, fatty spinal muscle, or visceral fat.\n\n\nCONCLUSIONS\nContrast media have a strong effect on the evaluation of body composition, whereas the influence of slice thickness is less pronounced. Radiation dose can be reduced by ≥66% without significantly affecting segmentation.