Theoretical and experimental study on the difference of the time-resolved fluorescence spectrum between the tumor and the adjacent normal tissue

Abstract

The objective of this paper is to study the difference of the time-resolved fluorescence spectrum between the tumor and the adjacent normal tissue. The time-resolved spectrum of the s-180 sarcoma tumor and adjacent normal tissue mediated by the Palladium-porphyrin photosensitizer (Pd-TCPP) is detected by a homemade instrumentation. An improved Monte Carlo algorithm, taking into account the depth of the upper layer tissue (z 1 ) and the delay of the fluorescence photon emission for the time (T) Pd-TCPP electrons spend in the excited state, is developed to study the reason of the spectrum difference formation. It is found from the experiment that the decay constant T decay of the time-resolved fluorescence spectrum of the tumor is obviously larger than that of the adjacent normal tissue. And T decay increased with the tumor growth, from 554μs in the first day to 634μs in the eighth day while it keeps steady for normal tissue. The simulated spectrum at different Z 1 and different T reveal that both the increase of Z 1 and τ can delay the spectrum decay. It is believed that Tdecay of the tumor tissue should be larger than that of adjacent normal tissue because of the hypoxia. The changes of tumor size and oxygen status cause the difference of the time-resolved fluorescence spectrum between the tumor and the adjacent normal tissue and this fact can be made use of in the tumor diagnoses.