title: Distance and angular dependence of intensity ratios in laser-induced autofluorescence techniques.
abstract: Laser-induced autofluorescence techniques have the potential to be used for the detection of preinvasive human cancer cells. For colorectal and gastrointestinal cancer cells, the light is introduced in vivo through endoscopic means and the probe tip is brought gently into contact with the tissue under investigation. However, it is often assumed that there is no distance or angular dependence in the intensity of the light collected from the probes. We performed an in vitro experiment in which we showed that there was indeed no angular dependence provided the angle of inclination of the probe to normal incidence is small. However, we find substantial fluctuation in the intensities of peaks for changing distances. These fluctuations can be eliminated by considering the ratio of the intensities from two spectral lines.
authors.affiliation: National Institute of Education, Nanyang Technological University, 1 Nanyang Walk, Singapore 639798.
authors.forename: L C
authors.initials: LC
authors.lastname: Kwek
authors.forename: Sheng
authors.initials: S
authors.lastname: Fu
authors.forename: T C
authors.initials: TC
authors.lastname: Chia
authors.forename: C L
authors.initials: CL
authors.lastname: Tang
mesh_terms: D015179:Colorectal Neoplasms / Q000145:classification* / Q000175:diagnosis*; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D007834:Lasers; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013050:Spectrometry, Fluorescence / Q000379:methods*