Table 2 Test/Retest variability of mean SUV of the selected key organs of interest.

From: Whole-Body [18F]FDG-PET/CT Imaging of Healthy Controls: Test/Retest Data for Systemic, Multi-Organ Analysis

Organ SUV

Test [SUV]

Retest [SUV]

Group

Subject

Δ%

t-test (paired)

ICC

t-value

p-value

(3,1)

CI95%

Δ%

Skeletal Muscle

0.6 ± 0.1

0.6 ± 0.1

3.6

3.63

0

0.71

0.54–0.83

5.5

Subcutaneous Fat

0.4 ± 0.1

0.4 ± 0.1

0.2

0.13

0.89

0.96

0.93–0.98

6

Visceral Fat

0.9 ± 0.2

0.8 ± 0.2

3.1

1.65

0.1

0.78

0.63–0.87

11.1

Heart Myocardium

3.8 ± 2.4

4 ± 3.1

6.1

−0.41

0.68

0.01

−0.27–0.29

64.1

Brain

6.8 ± 1.0

6.8 ± 0.9

0.4

0.27

0.79

0.71

0.54–0.83

7.8

Kidney (left)

2.9 ± 0.4

3.1 ± 0.6

6.5

−2.52

0.02

0.49

0.24–0.68

11.9

Kidney (right)

3.2 ± 0.7

3.4 ± 0.8

5.3

−1.48

0.14

0.39

0.12–0.6

13.1

Liver

2.3 ± 0.3

2.3 ± 0.3

0.8

0.83

0.41

0.82

0.7–0.89

5.2

Lung (lower left)

0.8 ± 0.2

0.8 ± 0.2

2

−1.44

0.16

0.88

0.8–0.93

7.1

Lung (lower right)

0.8 ± 0.2

0.8 ± 0.2

0.7

−0.47

0.64

0.88

0.79–0.93

7.1

Lung (middle right)

0.5 ± 0.1

0.5 ± 0.1

0.8

−0.63

0.53

0.92

0.85–0.95

6.3

Lung (upper left)

0.6 ± 0.1

0.6 ± 0.1

0.8

0.39

0.7

0.78

0.65–0.87

8.5

Lung (upper right)

0.5 ± 0.1

0.5 ± 0.1

0.8

−0.83

0.41

0.95

0.91–0.97

4.8

Pancreas

1.6 ± 0.2

1.6 ± 0.2

0.3

−0.15

0.88

0.43

0.17–0.63

8.9

Spleen

1.8 ± 0.2

1.7 ± 0.2

1

0.83

0.41

0.72

0.55–0.83

6.3

  1. Δ% (group level) reflects the relative difference between the mean Test and Retest intensities across all subjects. Δ% (subject level) represents the average of individual Test-Retest percentage differences computed per subject. Repeatability was considered good for: Δ% < 6.6% on the group level, Δ% < 41% on the subject level (thresholds were determined by: mean Δ% + 2 SD), and statistical significance of p > 0.05. Values not meeting these criteria are highlighted in bold text. Group-level analysis showed high consistency of SUV measurements (Δ% < 5%) for most organs, with the exception of the kidneys (Δ% = 5.3–6.5%) and heart (Δ% = 6.1%), which are known to exhibit high physiological variability. ICC(3,1) values confirmed excellent repeatability (ICC > 0.95) in most regions, but were notably lower in skeletal muscle (ICC = 0.71), pancreas (ICC = 0.43), and especially the heart (ICC = 0.01) and kidneys (ICC = 0.49 left, 0.39 right). Subject-level repeatability was similarly strong (Δ% < 9%) for most organs, except visceral fat (Δ% = 11.1%), likely reflecting weight-related changes.
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