Understanding Changes in Tumor Texture Indices in PET: A Comparison Between Visual Assessment and Index Values in Simulated and Patient Data

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FIGURE 1.
Process for creating sphere models. σ = SD.
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FIGURE 2.
Example of 10 sphere models with edge effects. σ = SD; R = radius of internal sphere.
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FIGURE 3.
Plots of homogeneity (A), entropy (B), HGZE (C), and LGZE (D) for 10 sphere models with edge effects (mean and SD over 20 replicates).
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FIGURE 4.
Box plots of homogeneity (A), entropy (B), HGZE (C), and LGZE (D) for 10 sphere models and 54 breast tumors without and with VOI erosion of 1 voxel. *P < 0.05, Wilcoxon test. **P < 0.01, Wilcoxon test.

TABLE 1

Summary of Texture Index Changes as Function of Type of Heterogeneity in Sphere Models

	First texture index family		Second texture index family		SUVs
Change	Homogeneity LRE	Entropy SRE	LGZE	HGZE	SUV_max	SUV_mean
Increasing average uptake (1 vs. 2)	—	+	—	+	+	+
Including hypersignal inserts (1 vs. 3, 4, 5)	—	+	—	+	+	+
Including hyposignal inserts (1 vs. 6, 7, 8)	—	+	+	—	Not sensitive	—
Making hyposignal insert larger (1 vs. 9, 10)	—	+	+	—	Not sensitive	—
Changing location of hyposignal (6 vs. 10)	Little to no sensitivity	Little to no sensitivity	Little to no sensitivity	Little to no sensitivity	Little to no sensitivity	Little to no sensitivity
Removing edge effect	+	—	—	+	Little to no sensitivity	+
Using smaller voxels	+	—	Little to no sensitivity	Little to no sensitivity	Little to no sensitivity	Little to no sensitivity

TABLE 2

Percentage of Breast Tumor Pairs with Less Than 5 mL of Volume Difference and Satisfying Various Conditions

Test	Percentage of pairs satisfying condition
Homogeneity (t1) > homogeneity (t2) and LRE (t1) > LRE (t2)	93.5
Entropy (t1) > entropy (t2) and SRE (t1) > SRE (t2)	91.5
Homogeneity (t1) > homogeneity (t2) and entropy (t1) < entropy (t2)	91.5
Homogeneity (t1) > homogeneity (t2) and SRE (t1) < SRE (t2)	95.0
Entropy (t1) > entropy (t2) and LRE (t1) < LRE (t2)	91.0
SRE (t1) > SRE (t2) and LRE (t1) < LRE (t2)	97.5
HGZE (t1) > HGZE (t2) and LGZE (t1) < LGZE (t2)	97.5