Reproducibility of MRI Dixon-Based Attenuation Correction in Combined PET/MR with Applications for Lean Body Mass Estimation

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FIGURE 1.
Examples of typical image artifacts in Dixon-based attenuation maps: missing tissue artifact (A), air cavities (B), truncation artifacts (C), and tissue swap artifact (D) with inverted ST and fat distributions in central bed position.
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FIGURE 2.
CV of total-body volume (TB). CVs are given for all MR-AC maps and for MR-AC maps excluding missing tissue artifacts, before and after exclusion of lung compartment.
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FIGURE 3.
CV of subcompartment volumes. CVs are shown for all MR-AC maps and for MR-AC maps excluding tissue swap and missing tissue artifacts (i.e., artifact-free).
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FIGURE 4.
Comparison of scaled LBM_MR-AC and LBM_Formula with LBM_ADP: using all MR-AC acquisitions (left) and excluding tissue swap and missing tissue artifacts (right). LBM_{MR-AC corrected} values (*) are LBM_MR-AC for the 2 volunteers with tissue swaps in all acquisitions for a single acquisition in which tissue swaps have been manually corrected.

TABLE 1

Summary of Results for All Subjects

Subject	Sex	Height (cm)	Body weight (kg)	Fat_ADP (kg)	LBM_ADP (kg)	LBM_Formula (kg)	LBM_MR-AC (all MR-AC maps/excluding artifacts) (kg)	Scaled LBM_MR-AC (kg)
1	F	169	56.4	11.9	44.5	43.9	42.9/42.8	45.4
2	M	177	82.5	22.2	60.3	63.0	55.9/55.9	59.2
3	M	178	67.4	14.2	53.3	55.8	51.9/51.9	55.0
4	M	169	71.4	16.5	54.9	55.7	52.0/51.8	54.9
5	F	170	59.0	16.4	42.7	45.3	40.6/40.5	43.0
6	F	167	56.0	12.6	43.4	43.3	40.6/40.3	42.7
7	F	160	56.8	15.5	41.3	42.1	38.5/38.5	40.8
8	M	180	79.0	5.6	73.4	62.3	63.9/— (67.1^*)	— (71.1^*)
9	M	179	71.7	5.0	66.8	58.3	59.3/— (60.7^*)	— (64.4^*)
10	F	169	56.9	5.8	51.2	44.1	47.6/48.4	51.3

↵* For these subjects, tissue swaps occurred in all repeated scans. Values in parentheses are extracted from 1 scan each for which tissue swaps were corrected manually. This was done by inverting ST and fat values in MR-AC maps in respective regions. This is predictive for LBM with no tissue swaps but is not supposed to result in same LBM gained from artifact-free MR-AC image.
LBM_MR-AC column shows values of LBM gained for all acquisitions with and without tissue swap and missing tissue artifacts. Scaled LBM_MR-AC column shows values scaled by scaling factor gained from linear regression.