Figure 1.

Cerenkov Light and Characteristics. A) Cerenkov radiation (CR) is produced by a charged particle traveling through a dialectric medium faster than the speed of light (in a vacuum) divided by the refractive index of that medium. Relaxation of the molecules in the medium, polarized by the passage of the charged particle, produces visible light weighted towards the higher energy of the spectrum. The profile of the CR is centered at the blue, as shown with ⁶⁸Ga (18.5 MBq) in 0.1 M HCl diluted in water, using a Molecular Diagnostics M5 spectrophotometer. B) Equal activities of F-18 samples (3.952 MBq, 20μL) were diluted in 2 mL of water (H₂O, refractive index: n=1.3359), ethanol (C₂H₅OH, n=1.366), saltwater (H₂O and saturating NaCl, n=1.377) along with a control sample of water without radionuclide. Samples were read for 20 exposures of 12.5 seconds using Stanford Photonics XR Mega 10 intensified charge-coupled device camera system in a 24 well plate. C) Cerenkov luminescence imaging (CLI) and D) PET imaging of nude mice bearing C6-FLuc tumor injected via tail vein with ¹⁸F-FDG at 0.5, 1, 2 h post-injection.