Effect of Intravenous Contrast on CT Body Composition Measurements in Patients with Intraductal Papillary Mucinous Neoplasm

Abstract

Background: The effect of differing post-contrast phases on CT body composition measurements is not yet known.

Methods: A fully automated AI-based body composition analysis using DAFS was performed on a retrospective cohort of 278 subjects undergoing pre-treatment triple-phase CT for pancreatic intraductal papillary mucinous neoplasm. The CT contrast phases included noncontrast (NON), arterial (ART), and venous (VEN) phases. The software selected a single axial CT image at mid-L3 on each phase for body compartment segmentation. The areas (cm²) were calculated for skeletal muscle (SM), intermuscular adipose tissue (IMAT), visceral adipose tissue (VAT), and subcutaneous adipose tissue (SAT). The mean Hounsfield units of skeletal muscle (SMHU) within the segmented regions were calculated. Bland-Altman and Chi Square analyses were performed.

Results: SM-NON had a lower percentage of bias [LOA] than SM-ART, -0.7 [-7.6, 6.2], and SM-VEN, -0.3 [-7.6, 7.0]; VAT-NON had a higher percentage of bias than ART, 3.4 [-18.2, 25.0], and VEN, 5.8 [-15.0, 26.6]; and this value was lower for SAT-NON than ART, -0.4 [-14.9, 14.2], and VEN, -0.5 [-14.3, 13.4]; and higher for IMAT-NON than ART, 5.9 [-17.9, 29.7], and VEN, 9.5 [-17.0, 36.1]. The bias in SMHU NON [LOA] was lower than that in ART, -3.8 HU [-9.8, 2.1], and VEN, -7.8 HU [-14.8, -0.8].

Conclusions: IV contrast affects the voxel HU of fat and muscle, impacting CT analysis of body composition. We noted a relatively smaller bias in the SM, VAT, and SAT areas across the contrast phases. However, SMHU and IMAT experienced larger bias. During threshold risk stratification for CT-based measurements of SMHU and IMAT, the IV contrast phase should be taken into consideration.

Keywords: CT; body composition; deep learning; intraductal papillary mucinous neoplasm; pancreatic; skeletal muscle index.

Figure 1

(A) Noncontrast CT and (B) DAFS v3 segmented noncontrast CT at the axial mid-L3 level. In each segmented image, red segmentation represents the skeletal muscle (SM) area. Teal segmentation represents subcutaneous adipose tissue (SAT). Olive green represents visceral adipose tissue (VAT). Bright green represents intermuscular adipose tissue (IMAT; corresponds to tissue designated by the black arrows among skeletal muscle). (C) Arterial phase post-contrast CT and (D) segmented arterial CT at the same level. (E) Venous phase post-contrast CT and (F) segmented venous CT at the same level.

Figure 1

(A) Noncontrast CT and (B) DAFS v3 segmented noncontrast CT at the axial mid-L3 level. In each segmented image, red segmentation represents the skeletal muscle (SM) area. Teal segmentation represents subcutaneous adipose tissue (SAT). Olive green represents visceral adipose tissue (VAT). Bright green represents intermuscular adipose tissue (IMAT; corresponds to tissue designated by the black arrows among skeletal muscle). (C) Arterial phase post-contrast CT and (D) segmented arterial CT at the same level. (E) Venous phase post-contrast CT and (F) segmented venous CT at the same level.

Figure 2

Bland–Altman plots: noncontrast phase skeletal muscle area (SM) compared to (A) arterial phase SM and (B) venous phase SM. Noncontrast phase visceral adipose tissue area (VAT) compared to (C) arterial phase VAT and (D) venous phase VAT. Noncontrast phase subcutaneous adipose tissue area (SAT) compared to (E) arterial phase SAT and (F) venous phase SAT. Noncontrast phase intermuscular adipose tissue area (IMAT) compared to (G) arterial phase IMAT and (H) venous phase IMAT. Noncontrast phase Hounsfield units of skeletal muscle (SMHU) compared to (I) arterial phase SMHU and (J) venous phase SMHU. The horizontal lines represent reference lines with respect to the data distribution drawn at 1.96 standard deviations below the mean (lower line), the mean (middle line), and 1.96 standard deviations above the mean (top line).

Figure 2

Bland–Altman plots: noncontrast phase skeletal muscle area (SM) compared to (A) arterial phase SM and (B) venous phase SM. Noncontrast phase visceral adipose tissue area (VAT) compared to (C) arterial phase VAT and (D) venous phase VAT. Noncontrast phase subcutaneous adipose tissue area (SAT) compared to (E) arterial phase SAT and (F) venous phase SAT. Noncontrast phase intermuscular adipose tissue area (IMAT) compared to (G) arterial phase IMAT and (H) venous phase IMAT. Noncontrast phase Hounsfield units of skeletal muscle (SMHU) compared to (I) arterial phase SMHU and (J) venous phase SMHU. The horizontal lines represent reference lines with respect to the data distribution drawn at 1.96 standard deviations below the mean (lower line), the mean (middle line), and 1.96 standard deviations above the mean (top line).