Oral cancer incidences have been increasing in recent years and late detection often leads to poor prognosis. Raman spectroscopy has been identified has a valuable diagnostic tool for cancer but its time consuming nature has prevented its clinical use. For Raman to become a realistic aid to histopathology, a rapid pre-screening technique is required to find small regions of interest on tissue sections [1]. The aim of this work is to investigate the feasibility of hyperspectral imaging in the visible spectral range as a fast imaging technique before Raman is performed. We have built a hyperspectral microscope which captures 300 focused and intensity corrected images with wavelength ranging from 450- 750 nm in around 30 minutes with sub-micron spatial resolution and around 10 nm spectral resolution. Hyperstacks of known absorbing samples, including fluorescent dyes and dried blood droplets, show excellent results with spectrally accurate transmission spectra and concentration-dependent intensity variations. We successfully showed the presence of different components from a non-absorbent saliva droplet sample. Data analysis is the greatest hurdle to the interpretation of more complex data such as unstained tissue sections.
Molar incisor hypomineralization (MIH) affects the permanent incisors and molars, whose undermineralized matrix is evidenced by lesions ranging from white to yellow/brown opacities to crumbling enamel lesions incapable of withstanding normal occlusal forces and function. Diagnosing the condition involves clinical and radiographic examination of these teeth, with known limitations in determining the depth extent of the enamel defects in particular. Optical coherence tomography (OCT) is an emerging hard and soft tissue imaging technique, which was investigated as a new potential diagnostic method in dentistry. A comparison between the diagnostic potential of the conventional methods and OCT was conducted. Compared to conventional imaging methods, OCT gave more information on the structure of the enamel defects as well as the depth extent of the defects into the enamel structure. Different types of enamel defects were compared, each type presenting a unique identifiable pattern when imaged using OCT. Additionally, advanced methods of OCT image analysis including backscattered light intensity profile analysis and enface reconstruction were performed. Both methods confirmed the potential of OCT in enamel defects diagnosis. In conclusion, OCT imaging enabled the identification of the type of enamel defect and the determination of the extent of the enamel defects in MIH with the advantage of being a radiation free diagnostic technique.
We have developed a new method for quantitative broadband CARS spectral imaging, which uses passive polarisation optics combined with spectrally-resolved balanced homodyne detection to remove the non-resonant background (NRB) in a single exposure. Independent measurement of the Stokes spectrum is not required for NRB removal, and the resulting spectra are amplified by the non-resonant response, vary linearly with concentration, and can be directly related to polarized spontaneous Raman spectra. The technique has relaxed requirements on spectral phase and instrument stability, is suitable for any laser system capable of generating CARS, and has been successfully applied to rapid hyperspectral Raman imaging.
Aim: The use of conventional mirror images does not adequately guide surgeons on the correction
of facial asymmetries. The purpose of this study was to evaluate the utility of an individualized atlas
as a template for corrective surgeries for patients suffering from mandibular asymmetry. The patientspecific
atlas is calculated from both the original asymmetric mandible and the mirror of the same
mandible registered on the cranial base. Material and Method: Three patients with history of
favorable clinical outcome of the correction of their mandibular asymmetry were chosen for this
pilot study. CBCT were taken before and 6 weeks after corrective surgery using NewTom 3G. Each
volume was mirrored and rigidly registered on the cranial base. Surface models for both the
mandible and its registered mirror were used to compute an atlas using deformable fluid registration.
Corrective surgery was simulated based of the resulting atlas. Differences between the virtual
simulated outcome and the actual surgical outcome were computed using UNC SPHARM-PDM
toolbox. Results: The detected differences between the virtual simulated outcome and the actual
surgical outcome, as characterized in 6 degrees of freedom, were smaller than 2 mm of translation
and 5 degrees of rotation. This indicates that the location of the synthesized template is similar to the
desired clinical outcome. Conclusions: The construction of patient-specific atlases using non-rigid
registration has the potential to optimize and increase the predictability of the outcome of
craniofacial corrective surgeries for asymmetric patients.
The Raman spectrum of a fluorescent chromophore typically has many spectral features, which differ markedly between
dyes even if their electronic spectra are similar. This high information content makes it possible to distinguish
biomarkers based on their Raman spectra. Coherent anti-Stokes Raman scattering may therefore allow for the
simultaneous measurement of more biomarkers than is possible with fluorescent imaging, while avoiding bleaching and
sample autofluorescence. We have built a broadband CARS microspectrometer to demonstrate the principle of CARS
multiplexing and investigate the potential to apply the system to studies of biological samples.
We investigate the mechanisms for fluorescence enhancement and energy transfer near a gold tip in apertureless
scanning near-field optical microscopy (ASNOM) and provide a demonstration of sub-diffraction tip-enhanced
fluorescence imaging. We have imaged the fluorescence from a single quantum dot cluster using ASNOM and find that
when a sharp gold tip is brought within a few nanometres from the sample surface, the resulting enhancement in
quantum dot fluorescence in the vicinity of the tip leads to a resolution of about 60 nm. We determine this enhancement
of the fluorescence to be about four-fold in magnitude, which is consistent with the value calculated with a simple
quasistatic model. Using this model we show that the observed enhancement of fluorescence results from a competition
between enhancement and quenching, dependent on a range of experimental parameters. We also demonstrate that
optical signals measured in ASNOM under ambient conditions are found to be affected significantly by the thin water
layer absorbed on the surface under investigation.
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