Search

Raminder Singh,1,2 Gokhan Dumlupinar,3,4 Stefan Andersson-Engels,3,4 Silvia Melgar1 1APC Microbiome Ireland, University College Cork, Cork, Ireland; 2School of Medicine, University College Cork, Cork, Ireland; 3Irish Photonics Integration Centre, Tyndall National Institute, Cork, Ireland; 4Department of Physics, University College Cork, Cork, Ireland Abstract: Colorectal cancer is the abnormal growth of cells in colon or rectum. Recent findings have acknowledged the role of bacterial infection and chronic inflammation in colorectal cancer initiation and progression. In order to detect and treat precancerous lesions, new tools are required, which may help to prevent or identify colorectal cancer at an early stage. To date, several different screening tests are available, including endoscopy, stool-based blood tests, and radiology-based tests. However, these analyses either lack sensitivity or are of an invasive nature. The use of fluorescently labeled probes can increase the detection sensitivity. However, autofluorescence, photobleaching, and photodamage are commonly encountered problems with fluorescence imaging. Upconverting nanoparticles (UCNPs) are recently developed lanthanide-doped nanocrystals that can be used as light-triggered luminescent probes and in drug delivery systems. In this review, we comprehensively summarize the recent developments and address future prospects of UCNP-based applications for diagnostics and therapeutic approaches associated with intestinal infection and colorectal cancer. Keywords: near infrared, imaging, bacteria, photodynamic therapy, anti-Stokes emission, inflammation

Absorption (mu(a)) and reduced scattering (mu(s)') spectra of turbid media were quantified with a noncontact imaging approach based on a Fourier-transform interferometric imaging system (FTIIS). The FTIIS was used to collect hyperspectral images of the steady-state diffuse reflectance from turbid media. Spatially resolved reflectance data from Monte Carlo simulations were fitted to the recorded hyperspectral images to quantify mu(a) and mu(s)' spectra in the 550-850-nm region. A simple and effective calibration approach was introduced to account for the instrument response. With reflectance data that were close to and far from the source (0.5-6.5 mm), mu(a) and mu(s)' of homogeneous, semi-infinite turbid phantoms with optical property ranges comparable with those of tissues were determined with an accuracy of +/-7% and +/-3%, respectively. Prediction accuracy for mu(a) and mu(s)' degraded to +/-12% and +/-4%, respectively, when only reflectance data close to the source (0.5-2.5 mm) were used. Results indicate that reflectance data close to and far from the source are necessary for optimal quantification of mu(a) and mu(s)'. The spectral properties of mu(a) and mu(s)' values were used to determine the concentrations of absorbers and scatterers, respectively. Absorber and scatterer concentrations of two-chromophore turbid media were determined with an accuracy of +/-5% and +/-3%, respectively.

A time-gated technique to enhance viewing through highly scattering media such as tissue is discussed. Experiments have been performed on tissuelike plastic phantoms to determine the possibilities and limitations of the technique. The effects of the time-gate width and the localization, size, and optical properties of hidden objects have been studied. A computer model to simulate light propagation in tissue is also presented. The predictions of the model are compared with experimental results. Key words: Medical diagnostics, time-gated viewing, tissue optics, transillumination, scattering media, diffusion equation, numerical modeling.