They did not change color when they were exposed to longer UV light at 365 nm possible due to quenching effects.
The thin layer chromatography that is containing 18F-FDG using silica gel on aluminum was glowing. The addition of an empty slice of TLC to this set up causes a change in the glow intensity of the source. The difference in the brightness between the two set up is regarding intensity. Fluorescent radiation is responsible for the light in the spot source. The silica gel can reflect this radiation. The initial set up containing the spot of source 18 F- FDG glows with more intensity than the empty TLC slice that is introduced later on in the setup. The empty slice of TLC glows because of absorbance of the initial fluorescent, and its capability to reflect the light and the reflective index of the plastic. However, the intensity of its fluorescence is not as much as the original fluorescent in the first set up.
A series of Cerenkov luminescence images were taken at a different field of view by using sample containing 18F-FDG and the other was empty. The samples have a radioactive source that emits a large amount of visible light. The signal detected from the sampel varies depending on the camera settings. Therefore, the ROI measurement in count mode was decreased by increasing the field of view (FOV).
A plot of the total counts for the whole field of view against the number of spots on the plate showed the relation between the total count of FOV and numbers of spots is linear as we expect
The linear relation between the number of spots and the total count of FOV
Additionally, divided the total counts by the number of spots and again get a nice approximation of an exponential decay curve.
Linear relationship between total count and field of view
The combination of 18F-FDG and addition of three drops of 25 mL of tonic water, tap water and FDG sample is shown above. Large amount of visible light is emitted by the integrated dots due to the merging amount of activities. The tonic water and tap water were florescent (bright blue). The florescent properties of tonic water are due to quinine. The light absorbed by quinine excites it and it releases the blue light as it returns from excited state to a state of lower energy. After addition f a few other drops, the tonic water is unable to absorb light anymore hence it lost its fluorescent property; ability to emit blue light. The ROI of the three drops were quite equal.
Ideally the ROI reading should be linearly proportional to the time of exposure. This linear and non-linearity behavior is dependent on the dosimeter type, size and physical characteristics. Cerenkov excited luminescence appears more and more diffuse as the exposure time increase. The graph below show the relation between the ROI in count mode and the time of exposure for 5ouL of 18F-FDG.
The relationship between exposure time and total count
Using identical size of ROI, the background obtained from one to six of the drops was measured in count mode and subtracted from the acquired images. From the graph below it is obvious that almost all the spots are the same over time except the error in the third spot due to the different size of drop.
The flat linear over time between the number of spots and total count
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