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Autofluorescence (AF) spectra of colonic normal and adenocarcinoma tissues are measured under excitation of 337 nm and analyzed by multivariate curve resolution alternating least squares (MCR-ALS) method using non-negativity constraint. Collagen, nicotinamide adenine dinucleotide hydrate (NADH) and elastin are identified as the main contributing biomedical components. Fisher's discrminant anlysis (FDA) on the concentration profiles of the principle components (PCs) shows acceptable sensitivity, specificty and accuracy for discrminanting the adenocarcinoma tissues from the normal tissues. MCR-ALS is a powerful tool for characterzing the spectra profiles of the main biochemical components in neoplasm transformation.

In the past two decades, two-photon microscopy (TPM) transforms biomedical research, allowing nondestructive high-resolution fluorescent molecular imaging and label-free imaging in vivo and in real time. Here we review the recent advances of TPM technology including novel laser sources, new image acquisition paradigms, and microendoscopic imaging systems. Then, we survey the capabilities of TPM imaging of biological relevant molecules such as nicotinamide adenine dinucleotide (NADH), flavin adenine dinucleotide (FAD), and reactive oxygen species (ROS). Biomedical applications of TPM in neuroscience and cancer detection are demonstrated.

We evaluate the ablation thresholds of Er:YAG and Er,Cr:YSGG laser for enamel and dentin. A total of 140 dental slices is evenly divided into two groups: the dentin group and the enamel group. Dental tissues are irradiated with either an Er:YAG laser or an Er,Cr:YSGG laser with pulse widths in the order of 100 μs. The laser fluence is increased gradually until the ablation crater is formed. The laser ablation threshold is calculated using probit analysis. The ablation thresholds of the Er:YAG laser for dentin and enamel range from 2.88 to 3.36 J/cm2 and from 2.94 to 3.8 J/cm2, respectively, and the ablation thresholds of the Er,Cr:YSGG laser for dentin and enamel range from 2.92 to 4.2 J/cm2 and from 4.93 to 5.66 J/cm2, respectively.

Determination of NO concentration in live cells is essential to evaluate its related cellular functions. In this letter, the concentration of NO in HeLa cells and rat dorsal root ganglion (DRG) neurons are studied by confocal laser scanning microscopy using DAF-2 DA as a fluorescence probe. The results show the fluorescence intensity of NO in HeLa cells is higher than that in DRG neurons, which indicats that the former exhibits higher NO concentration. Furthermore, the experimental conditions for low photobleaching and phototoxicity are optimized.

The influence of scanning speed on hard bone tissue ablation is studied with a 10.6-\mum laser. The groove morphology and the thermal damage created in bovine shank bone by pulsed CO2 laser are examined as a function of incident fluence by optical microscope following standard histological processing. The results show that ablation groove width, depth and ablation volume, as well as the zone of thermal injury, increase gradually with incident fluence. As compared to the result for high scanning speed, the lower scanning speed always produces larger ablation volume but thicker zone of thermal injury. It is evident that scanning speed plays an important role in the ablation process. In clinical applications, it is important to select appropriate scanning speed to obtain both high ablation rates and minimal thermal injury.

To confirm the existence and properties of human meridians, the optical transport properties along the pericardium meridian and tissues around the pericardium meridian are studied noninvasively on twenty healthy volunteers in vivo and then compared with each other. Our study shows that the light propagating along the meridian and non-meridian directions both conform to the Beer's exponential attenuation law. However, statistical analysis of the results suggests that the optical transport properties of human meridian differ from those of the surrounding tissues over a low modulated frequency range (Pl0.01), and light attenuation along the pericardium meridian is significantly less than that along the non-meridian direction. These findings not only indicate the existence of acupuncture meridian from the point of view of biomedical optics, but also shed new light on an approach to investigation of human meridians.

Light dose plays an important role in the non-ablative photorejuvenation based on the theory of selective photothermolysis. However, present techniques for determining the light dose in clinical practice are still not accurate enough. We present a new system which monitors the skin tissue response during the laser irradiation in photorejuvenation by measuring the change of the total attenuation coefficient. We also investigate the relationship between the total attenuation coefficient and the energy density, pulse duration, and pulse repetition. In this procedure, the total attenuation coefficient decreases when the light dose increases and the reduction dependes on the light dose. These experimental results indicate that the new system would be a potential tool for accurate light dose determination.

The feasibility of measuring crater geometries by use of optical coherence tomography (OCT) is examined. Bovine shank bone on a motorized translation stage with a motion velocity of 3 mm/s is ablated with a pulsed CO2 laser in vitro. The laser pulse repetition rate is 60 Hz and the spot size on the tissue surface is 0.5 mm. Crater geometries are evaluated immediately by both OCT and histology methods after laser irradiation. The results reveal that OCT is capable of measuring crater geometries rapidly and noninvasively as compared to histology. There are good correlation and agreement between crater depth estimates obtained by two techniques, whereas there exists distinct difference between crater width estimates when the carbonization at the sides of craters is not removed.

Singlet oxygen (1O2) is widely considered to play a major role in photodynamic therapy (PDT), and thus an increasing attention has been focused on the direct detection of 1O2 near-infrared luminescence around 1270 nm for PDT dosimetry. A new sensitive detection system is developed to directly measure the temporal and spectral resolved 1O2 luminescence spectra. The triplet state and 1O2 lifetimes of Rose Bengal as a model photosensitizer in different solvents are determined, and the obtained results agree well with the published data. Our detection system has the potential application in 1O2 luminescence-based PDT dosimetry.

The feasibility of fenestration operation in middle ear bone with pulsed infrared laser is evaluated. Healthy male New Zealand rabbits in vivo are used in the experiment. Middle ear mastoid bone of animal model is completely exposed with conventional methods, and then a pulsed COlsubg2l/subg laser (10.6 \mu m) and an Er:YAG laser (2.94 \mu m) are used to perform the fenestration operation. Diamond drill is also used as a control group. The total operation time and light irradiation time are recorded and the opening efficiency is assessed. The morphological changes and thermal damage around the opening window on the middle ear bone are examined. It is shown that both laser systems are suitable for the fenestration operation in middle ear bone, and this no-touch technique has a lot of benefits compared with traditional methods. The bleeding during operation has an important effect on operation time and thermal injury and needs to be controlled efficiently in further study.