## 4 Discussion
If available, such information would allow customizing the patient inclusion criteria, setting a threshold/range to the size of the regions that can be properly investigated with radiomics, and would guide the choice of the most suitable image filter and feature categories for each study, avoiding an unnecessary proliferation of the parameters calculated from the images. Conversely, in the absence of this information, noise could be introduced, which might ultimately mask the information radiomics is expected to quantify and prevent the possibility of identifying useful associations between radiomic features and clinically relevant information. Despite its relevance, this issue has not been extensively investigated in the case of MRI, probably due to the lack of suitable phantoms to perform systematic acquisitions under controlled settings. [PERSON] et al. [14] investigated the stability of radiomic features across different VOI sizes using a homogeneous phantom and evidenced the need to repeat the analysis with heterogeneous objects to allow clinical translation of the phantom results. [PERSON] et al. [12] developed a phantom with heterogeneous objects, but they considered one VOI volume only. To assess the volume dependency, instead, it is necessary not only to have objects with different textures, possibly simulating the texture of the tissues under investigation in the clinical application, but also that each object is homogeneous and large enough to incorporate different VOIs with different volumes but fixed texture. In this sense, the phantom developed by our group appears suitable for the purpose, even if the pattern within each insert is not obtained via replication of a texture kernel to increasingly larger volumes, as would be more appropriate, and even if until now only texture 1--small spheres--was demonstrated to be comparable to a real clinical scenario (gynecological diseases [8]). Nonetheless, despite these two limitations, this phantom incorporates three textures that are different by construction, a difference that radiomic features should theoretically be able to reflect. In addition, despite the random distribution of small, medium, and large spheres in each insert, it is still true that the textures within different VOIs of the same insert are far more similar among them than the textures within VOIs drawn on different inserts. For these reasons, important information can be obtained from this phantom prototype, laying the basis for further studies, possibly with improved phantom versions to match more closely specific clinical scenarios. The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app12115465/s1](https://www.mdpi.com/article/10.3390/app12115465/s1)]([https://www.mdpi.com/article/10.3390/app12115465/s1](https://www.mdpi.com/article/10.3390/app12115465/s1)). Conceptualization, F.B., D.O., M.C. and A.L. ; methodology, J.S., L.B., M.F., C.M., A.L., N.P. and F.B. ; software, J.S. and L.B. ; validation, J.S., L.B., M.F., A.L., N.P. and F.B. ; formal analysis, J.S. and L.B. ; investigation, J.S., L.B., F.B. and D.O. ; resources, J.S., L.B., A.L., C.M. and M.C. ; data curation, J.S. and L.B. ; writing--original draft preparation, J.S. and L.B. ; writing--review and editing, J.S., L.B., F.B., D.O. and M.C. ; visualization, J.S., L.B., F.B., D.O., A.L., M.F., C.M. and N.P. ; supervision, F.B. and D.O. ; project administration, F.B., D.O., A.L., M.C. and B.A.J.-F.; funding acquisition, M.C. and B.A.J.-F. All authors have read and agreed to the published version of the manuscript. The work was partially supported by the Italian Ministry of Health with Ricerca Corrente and 5x1000 funds. Part of the research leading to these results has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement No. 952159 (ProCAncer-I). Not applicable. The authors thank [PERSON], Philips' Clinical Scientist and Product Specialist MR for his insights used in the Discussion.