The effect of SUV discretization in quantitative FDG-PET Radiomics: the need for standardized methodology in tumor texture analysis.

Ralph T.H Leijenaar,Philippe Lambin,Robert J Gillies,Sara Carvalho,Esther G.C Troost,Georgi Nalbantov,Wouter J.C Van Elmpt,Hugo J.W.L Aerts,Ronald Boellaard

doi:10.1038/srep11075

Abstract

FDG-PET-derived textural features describing intra-tumor heterogeneity are increasingly investigated as imaging biomarkers. As part of the process of quantifying heterogeneity, image intensities (SUVs) are typically resampled into a reduced number of discrete bins. We focused on the implications of the manner in which this discretization is implemented. Two methods were evaluated: (1) RD, dividing the SUV range into D equally spaced bins, where the intensity resolution (i.e. bin size) varies per image; and (2) RB, maintaining a constant intensity resolution B. Clinical feasibility was assessed on 35 lung cancer patients, imaged before and in the second week of radiotherapy. Forty-four textural features were determined for different D and B for both imaging time points. Feature values depended on the intensity resolution and out of both assessed methods, RB was shown to allow for a meaningful inter- and intra-patient comparison of feature values. Overall, patients ranked differently according to feature values–which was used as a surrogate for textural feature interpretation–between both discretization methods. Our study shows that the manner of SUV discretization has a crucial effect on the resulting textural features and the interpretation thereof, emphasizing the importance of standardized methodology in tumor texture analysis.

Highlights

In recent years, oncological research has increasingly focused on the prediction of treatment outcome based on individual patient and tumor characteristics[1], aiming to avoid the one-size-fits-all treatment approach that under- and over-treats a large number of patients
None of the observed pairwise intra-class correlation coefficient (ICC) was higher than 0.85, meaning that textural features and their ascribed value depend on the intensity resolution used for standardized uptake values (SUVs) discretization
When aiming to identify and validate imaging biomarkers with tumor texture analysis of FDG-Positron emission tomography (PET), it is important that the textural feature values be directly comparable, both inter- and intra-patient, in order to derive meaningful conclusions

Summary

Introduction

Oncological research has increasingly focused on the prediction of treatment outcome based on individual patient and tumor characteristics[1], aiming to avoid the one-size-fits-all treatment approach that under- and over-treats a large number of patients. Imaging can play a crucial role here, as it allows for a non-invasive identification and characterization of the tumor[2,3]. PET imaging has been increasingly used for decision support[5], treatment planning[6,7] and response monitoring during radiotherapy[8]. The most widely used PET tracer is [18F] fluoro-2-deoxy-D-glucose (FDG), commonly quantified by standardized uptake values (SUVs)[9]. Derived SUV measurements, such as the maximum www.nature.com/scientificreports/

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