**5. Conclusions**

A novel image-derived input function method for quantifying the TSPO binding with 18F-DPA-714 was developed in this work. We used two separate cohorts as an initial validation for this method and showed that it may serve as a promising alternative for an automatic and noninvasive way to extract the IDIF.

**Supplementary Materials:** The following supporting information can be downloaded at: https: //www.mdpi.com/article/10.3390/diagnostics12051161/s1, Figure S1: The comparison between AIF and IDIF for the other four subjects in the blood-sampling cohort.

**Author Contributions:** Conceptualization, Y.-H.D.F. and J.E.M.; Data curation, T.A.Y.; Formal analysis, Y.-H.D.F., Y.Z. and R.E.K.; Funding acquisition, D.G.S.; Investigation, Y.-H.D.F., J.E.M. and D.G.S.; Methodology, Y.-H.D.F.; Project administration, T.A.Y.; Software, Y.-H.D.F.; Supervision, D.G.S.; Writing–original draft, Y.-H.D.F.; Writing–review & editing, J.E.M., T.A.Y., Y.Z., R.E.K. and D.G.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** This study was supported by the Alabama Morris K. Udall Center of Excellence in Parkinson's Research (NS108675) and the Parkinson Association of Central Alabama.

**Institutional Review Board Statement:** The study was conducted according to the guidelines of the Declaration of Helsinki and approved by the Institutional Review Board of the University of Alabama at Birmingham (protocol code IRB-300001025 approved on 16 October 2017).

**Informed Consent Statement:** Informed consent was obtained from all subjects involved in the study.

**Data Availability Statement:** The data presented in this study are available on request from the corresponding author. The data are not publicly available due to the privacy of the enrolled subjects.

**Acknowledgments:** We thank all study participants and Jennifer Bartels, Allan Joop, and Lauren Ruffrage for research support.

**Conflicts of Interest:** This study was supported by the Alabama Morris K. Udall Center of Excellence in Parkinson's Research (NS108675) and the Parkinson Association of Central Alabama. Jonathan McConathy is an investigator in studies funded by NIH, Eli Lilly/Avid, Blue Earth Diagnostics, Cytosite Biopharma, and ImaginAb. He is a consultant for Eli Lilly/Avid, GE Healthcare, Blue Earth Diagnostics, ImaginAb, and Canon Medical. Talene Yacoubian has active grants from the American Parkinson Disease Association, Travere Therapeutics, and the NIH. She has received honoraria for presentations from the Movement Disorder Society and for gran<sup>t</sup> reviews from the NIH and the Michael J. Fox Foundation. David Standaert is an investigator in studies funded by AbbVie Inc., the American Parkinson Disease Association, the Michael J. Fox Foundation for Parkinson Research, Alabama Department of Commerce, the Department of Defense, and the NIH. He has served as a consultant for or received honoraria from AbbVie Inc., the Parkinson Study Group, Curium Pharma, the International Parkinson Disease and Movement Disorder Society, Theravance, McGraw Hill, Gray Matter Technologies, and Sanofi-Aventis. No potential conflict of interest relevant to this article exist.
