(Sunday, 7/29/2018) 3:30 PM - 4:00 PM
Room: Exhibit Hall | Forum 9
Purpose: Bioluminescence has been used extensively as an in-vivo photon-emitting reporter imaging method. Although light absorption in tissue is well studied, it is generally ignored when quantifying signals produced by luciferase-tagged sources. This may be especially troublesome when accurate quantification is needed from low intensity sources, like migrating cells in tumor migration studies. The purpose of this study is to quantify the extent to which tissue geometry influences the sensitivity, reproducibility, and accuracy of quantification of bioluminescent signals.
Methods: A simulation was run using IDL to quantify photon emission and quantitation from sources embedded in a rectangular homogeneous medium of varying dimension. Signals generated at different depths were propagated to the phantom surface using the diffusion approximation to the radiative transfer equation and integrated. A model of migration of luciferase-expressing cells was created in which a mouse was inoculated with two separate tumors on the adjacent lower mammary fat pads, one expressing luciferase (donor) and one not (recipient). At 100mm3 volume the recipient tumors were irradiated (20Gy) to stimulate recruitment of migrating donor cells. 10 days post-irradiation mice were injected with D-luciferin prior to termination and recipient tumors were excised and imaged with a bioluminescence imaging system.
Results: The simulation results showed that when cubic block is cut in half (7.5mm) the estimated light increased by 1.8-fold relative to the intact block (15mm). This is consistent the in vivo results, in which cutting the excised tumors from thicknesses of 15mm to 7.5 increased measured bioluminescent intensity by 2.15-fold increase (±22%).
Conclusion: Bioluminescence is used extensively in pre-clinical imaging for strong/well illuminated sources, without considering the tissue absorption. However, for weak sources of illumination like migration of cells or small metastasis the attenuation of light through few mm of muscle can be very critical when assessing quantitative analysis across animals.
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