Cellular autofluorescence imaging for early diagnosis of cancers

摘要

Urinary cytology is employed in diagnostic guidelines of bladder cancer in anatomo-pathological laboratories mostly for its ability to diagnose non detectable cancers using cystoscopy, but also because it is a non-invasive and non-constraining technique for a regular follow-up of the more exposed populations. The impossibility to detect such cancers is mainly due to their localization either in the bladder or in the upper urinary tract and the prostate. However, urinary cytology lacks sensitivity, especially for the detection of low grade low stage tumors due to inherent limitation of morphological criteria to distinguish low grade tumor cells from normal urothelial cells. For this purpose, we developed, in addition to urinary cytology, an original screening of these cytological slides by using spectrally-resolved and time-resolved fluorescence as a contrast factor, without changing any parameters in the cytological slide preparation. This method takes advantage of a femtosecond Ti:sapphire laser, continuously tunable in the spectral range 700-950 nm allowing the observation of most endogenous cellular chromophores by biphotonic excitation. A commercial confocal microscope was also used in the measurements allowing an excitation of the samples between 458 nm and 633 nm. We observed that the fluorescence emission is differentially distributed in normal and pathological urothelial cells. Spectral- and time-resolved measurements attested this difference over about one hundred cases which have been tested to confirm the high accuracy of this non-invasive technique.