Robustness of textural analysis features in quantitative 99 mTc and 177Lu SPECT-CT phantom acquisitions.

Background: Textural Analysis features in molecular imaging require to be robust under repeat measurement and to be independent of volume for optimum use in clinical studies. Recent EANM and SNMMI guidelines for radiomics provide advice on the potential use of phantoms to identify robust features (Hatt in EJNMMI, 2022). This study applies the suggested phantoms to use in SPECT quantification for two radionuclides, ^{99 m}Tc and ¹⁷⁷Lu.

Methods: Acquisitions were made with a uniform phantom to test volume dependency and with a customised 'Revolver' phantom, based on the PET phantom described in Hatt (EJNMMI, 2022) but with local adaptations for SPECT. Each phantom was filled separately with ^{99 m}Tc and ¹⁷⁷Lu. Sixty-seven Textural Analysis features were extracted and tested for robustness and volume dependency.

Results: Features showing high volume dependency or high Coefficient of Variation (indicating poor repeatability) were removed from the list of features that may be suitable for use in clinical studies. After feature reduction, there were 39 features for ^{99 m}Tc and 33 features for ¹⁷⁷Lu remaining.

Conclusion: The use of a uniform phantom to test volume dependency and a Revolver phantom to identify repeatable Textural Analysis features is possible for quantitative SPECT using ^{99 m}Tc or ¹⁷⁷Lu. Selection of such features is likely to be centre-dependent due to differences in camera performance as well as acquisition and reconstruction protocols.