Reproducibility of tumor uptake heterogeneity characterization through textural feature analysis in 18F-FDG PET

Abstract

(18)F-FDG PET measurement of standardized uptake value (SUV) is increasingly used for monitoring therapy response and predicting outcome. Alternative parameters computed through textural analysis were recently proposed to quantify the heterogeneity of tracer uptake by tumors as a significant predictor of response. The primary objective of this study was to evaluate the reproducibility of these heterogeneity measurements.

Methods: Double baseline (18)F-FDG PET scans were acquired within 4 d of each other for 16 patients before any treatment was considered. A Bland-Altman analysis was performed on 8 parameters based on histogram measurements and 17 parameters based on textural heterogeneity features after discretization with values between 8 and 128.

Results: The reproducibility of maximum and mean SUV was similar to that in previously reported studies, with a mean percentage difference of 4.7% ± 19.5% and 5.5% ± 21.2%, respectively. By comparison, better reproducibility was measured for some textural features describing local heterogeneity of tracer uptake, such as entropy and homogeneity, with a mean percentage difference of -2% ± 5.4% and 1.8% ± 11.5%, respectively. Several regional heterogeneity parameters such as variability in the intensity and size of regions of homogeneous activity distribution had reproducibility similar to that of SUV measurements, with 95% confidence intervals of -22.5% to 3.1% and -1.1% to 23.5%, respectively. These parameters were largely insensitive to the discretization range.

Conclusion: Several parameters derived from textural analysis describing heterogeneity of tracer uptake by tumors on local and regional scales had reproducibility similar to or better than that of simple SUV measurements. These reproducibility results suggest that these (18)F-FDG PET-derived parameters, which have already been shown to have predictive and prognostic value in certain cancer models, may be used to monitor therapy response and predict patient outcome.

Figure 1

Illustration of one of the tumors considered in this study (sagittal slice) for varying discretization values (from 8 to 128 distinct values).

Figure 2

Bland-Altman plots of intensity histogram parameters: SUV_max (A) and kurtosis (B); as well as textural features heterogeneity parameters: entropy (C) and size-zone variability (D). Lines show combined mean, 95%CI, as well as upper and lower reproducibility limits

Figure 3

Plots showing the standard deviation of the mean percentage difference as a function of the discretization value for parameters derived from co-occurrences matrices (entropy, dissimilarity, contrast) (A) and intensity size-zone matrices (LISAE: Low-intensity small-area emphasis, SZV: Size-zone variability, ZP: zone percentage) (B).