Figure 1.
Example Water, Fat and Fat Signal Fraction Images.
Example images of water (left) and fat (middle) separation based on the opposed-phase imaging are shown. Fat signal fraction (right) is defined as the ratio of fat to the combined signal from fat and water. Moderate fat fraction values indicate BAT depots in the supraclavicular/axillary region (white arrows).
Figure 2.
Measured fat fraction in rodent demonstrates differentiation in fat fraction between white and brown adipose tissues. (A) In situ and ex vivo samples of BAT (brown adipose tissue) and WAT (white adipose tissue). (B) Single slice fat fraction map of ex vivo tissues in glass vials.
Figure 3.
Three-plane view of BAT (brown adipose tissue) in a participant with relatively large (bottom row) and small (top row) deposits. Arrows in the axial and coronal views indicate supraclavicular/axillary BAT. Arrows in the sagittal view indicate bilateral spinal BAT deposits. Underlay volume is the in-phase echo.
Figure 4.
BAT (brown adipose tissue) segmentations in the neonate. From left to right: sagittal view of semi-automatic segmentations of spine T1–T5 (green), coronal view of supraclavicular (magenta) and axillary (red) ROIs, the 3-dimensional render of ROIs used in this manuscript, a 3-dimensional render of all voxels that fit the BAT criteria used in this manuscript for visualization (rust color).
Figure 5.
Sagittal view of scan/rescan comparison of Dixon based fat fraction maps in a single neonate. (A) First scan followed by (B) re-shimming and an identical repeat scan, hotter color denotes a higher fat fraction. (C) In-phase image depicting underlying anatomy. (D) Difference map in calculated fat fraction, note highest intensities are found at edges due to mis-registration between scans and an inhomogeneity artifact present in the fingers anterior to the chest.
Figure 6.
Voxel by voxel fat fraction correlation between scans. Strong voxelwise correlations between scans were observed in BAT segmentations (blue, RBAT = 0.94), a WAT segmentation done in the nape of the neck (red, RWAT = 0.88) and all other voxels (gray, RALL = 0.99). Artifact voxels are those identified in the hand.
Figure 7.
Plot of inter- and intra-rater depot volume reliability. (A) Brown Adipose Tissue (BAT) segmentations repeated on 22 subjects by two different raters: supraclavicular/axillary union ROIs (blue, R = 0.86) and spinal ROIs (red, R = 0.89). (B) BAT segmentations repeated on 22 subjects by a single rater separated by two weeks time (1a and 1b): supraclavicular/axillary ROIs (blue, R = 0.94) and spinal ROIs (red, R = 0.94).
Table 1.
Summary of Brown Adipose Tissue Depot Volume and Fat Fraction.
Table 2.
Inter- and intra-rater reliability results.