Medical imaging has changed how we study and treat brain degeneration. The best tool for imaging subtle changes to brain proteins is positron emission tomography (or PET). But that has limited availability. An equivalent tool, single-photon emission computed tomography (SPECT) is more available. But SPECT lacks radioactive probes that generate certain images. This situation limits access to best brain-study tools in rural areas and developing nations. This study will develop SPECT probes to improve access to imaging. Specifically, the team will create and evaluate molecules labeled with technetium-99m, as this is the most-used radionuclide in the world. The primary outcome of this research will be SPECT radioligands that can image proteins known to play a role in dementia. These can then be used as a diagnostic tool to screen people at risk for developing dementia, to track disease progress, or evaluate therapy effectiveness.