Effects of contrast-medium and vertebral measurement level on computed tomography-based body composition parameters of skeletal muscle and adipose tissue

Objective To comprehensively evaluate the effects of contrast-medium administration and measurement level (L3 and L1) on computed tomography (CT) derived body composition parameters, promising prognostic factors for various diseases. Methods 203 dynamic contrast-enhanced CT examinations, including unenhanced (phase 0) and early arterial, late arterial, portal, and equilibrium phases (phases 1-4, respectively), were retrospectively enrolled in the study. Areas and mean densities of skeletal muscle (SMA and MSMD), subcutaneous adipose tissue (SATA and MSATD), and visceral adipose tissue (VATA and MVATD) were measured at L3 and L1 levels across five phases (phase 0–4). Measurement changes among phases and levels were assessed statistically. Results The rates of SMA, SATA, and VATA on phase 1/2/3/4 compared to those on phase 0 were as follows: L3 SMA +1.1%/+2.1%/+2.8%/+3.5%; L1 SMA, +2.0%/+2.7%/+3.0%/+3.7%; L3 SATA −0.4%/−1.9%/−2.9%/−4.7%; L1 SATA −0.3%/−2.2%/−3.5%/−6.1%; L3 VATA −7.5%/−17.8%/−20.0%/−22.2%; L1 VATA −8.5%/−20.1%/−22.6%/−23.7%. Differences of MSMD, MSATD, and MVATD on phase 1/2/3/4 between those on phase 0 were as follows (Hounsfield Units): L3 MSMD, +2.1/+5.8/+7.8/+9.6; L1 MSMD, +2.9/+7.7/+9.1/+9.8; L3 MSATD, +1.2/+3.7/+4.8/+6.2; L1 MSATD, +1.2/+3.8/+4.7/+5.6; L3 MVATD, +1.5/+4.1/+5.2/+6.1; L1 MVATD, +1.9/+4.9/+5.8/+6.3. The values between L3 and L1 showed a linear solid correlation (coefficient of determination, 0.950–0.999), suggesting interchangeability. Conclusion Changes in body composition parameters measured in various contrast phases and two dominant body levels were comprehensively elucidated, promoting the interchangeability of cohorts with mixed CT conditions.