**4. Conclusions**

The present NDT CMOS-based detector exhibits excellent linearity across the examined exposure range and a higher gain factor compared to the older 22.5 μm CMOS. The MTF calculated according to the IEC 2003 standard is in close agreemen<sup>t</sup> with the CMOS manufacturer's MTF curve, whereas the MTF calculated with IEC 2015 is lower in the higher frequency range, due to the averaging method of IEC 2003 that leads to an overestimation of the MTF. MTF values are higher compared to other commercial CMOS detectors. However, the previous, discontinued, version of the detector under investigation performs slightly better in terms of the MTF, despite its coarser pixel pitch (22.5 μm instead of 20.0 μm). Regarding the detector's phosphor material, Gd2O2S:Tb, and based on its properties' pertinence to those of CdWO4, dual-energy application is discussed. Specifically, the present CMOS with its Gd2O2S:Tb scintillator, in conjunction with ZnSe: Te, appears as a promising candidate for a dual-energy flat imager aimed at the NDT and medical fields.

**Author Contributions:** Conceptualization, C.M. and G.F.; methodology, C.M., D.L., I.V., V.K., A.B., and N.M.; software, V.K., and N.M.; validation, C.M. and A.K.; formal analysis, C.M., D.L., and G.F.; investigation, C.M., G.F., D.L., A.K., and I.V.; resources, A.B.; data curation, C.M., D.L., N.M., and V.K.; writing—original draft preparation, D.L. and C.M.; writing—review and editing, D.L., C.M., A.K., and I.V.; visualization, I.V.; supervision, C.M.; project administration, C.M., and G.F.; funding acquisition, I.V. All authors have read and agreed to the published version of the manuscript.

**Funding:** The APC was funded by the Special Account for Research Grants, of the University of West Attica, Greece.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Data is contained within the article..

**Conflicts of Interest:** The authors declare no conflict of interest.
