Ching-Cheng Chuang

Dental optical coherence tomography.

This review paper describes the applications of dental optical coherence tomography (OCT) in oral tissue images, caries, periodontal disease and oral cancer. The background of OCT, including basic theory, system setup, light sources, spatial resolution and system limitations, is provided. The comparisons between OCT and other clinical oral diagnostic methods are also discussed.

Subgingival calculus imaging based on swept-source optical coherence tomography

We characterized and imaged dental calculus using swept-source optical coherence tomography (SS-OCT). The refractive indices of enamel, dentin, cementum, and calculus were measured as 1.625 ± 0.024, 1.534 ± 0.029, 1.570 ± 0.021, and 2.097 ± 0.094, respectively. Dental calculus leads strong scattering properties, and thus, the region can be identified from enamel with SS-OCT imaging. An extracted human tooth with calculus is covered with gingiva tissue as an in vitro sample for tomographic imaging.

Patient-oriented simulation based on Monte Carlo algorithm by using MRI data

BackgroundAlthough Monte Carlo simulations of light propagation in full segmented three-dimensional MRI based anatomical models of the human head have been reported in many articles. To our knowledge, there is no patient-oriented simulation for individualized calibration with NIRS measurement. Thus, we offer an approach for brain modeling based on image segmentation process with in vivo MRI T1 three-dimensional image to investigate the individualized calibration for NIRS measurement with Monte Carlo simulation.MethodsIn this study, an individualized brain is modeled based on in vivo MRI 3D image as five layers structure. The behavior of photon migration was studied for this individualized brain detections based on three-dimensional time-resolved Monte Carlo algorithm. During the Monte Carlo iteration, all photon paths were traced with various source-detector separations for characterization of brain structure to provide helpful information for individualized design of NIRS system.ResultsOur results indicate that the patient-oriented simulation can provide significant characteristics on the optimal choice of source-detector separation within 3.3 cm of individualized design in this case. Significant distortions were observed around the cerebral cortex folding. The spatial sensitivity profile penetrated deeper to the brain in the case of expanded CSF. This finding suggests that the optical method may provide not only functional signal from brain activation but also structural information of brain atrophy with the expanded CSF layer. The proposed modeling method also provides multi-wavelength for NIRS simulation to approach the practical NIRS measurement.ConclusionsIn this study, the three-dimensional time-resolved brain modeling method approaches the realistic human brain that provides useful information for NIRS systematic design and calibration for individualized case with prior MRI data.

Diffuse Optical Multipatch Technique for Tissue Oxygenation Monitoring: Clinical Study in Intensive Care Unit

Diffuse optical multipatch technique is used to assess spatial variations in absorption and scattering in biological tissue, by monitoring changes in the concentration of oxyhemoglobin and deoxyhemoglobin. In our preliminary study, the temporal tracings of tissue oxygenation are measured using diffuse optical multipatch measurement and a venous occlusion test, employing normal subjects and ICU patients suffering from sepsis and heart failure. In experiments, obvious differences in tissue oxygenation signals were observed among all three groups. This paper discusses the physiological relevance of tissue oxygenation with respect to disease.

Gender-related effects of prefrontal cortex connectivity: a resting-state functional optical tomography study

The prefrontal cortex (PFC) is thought to play an important role in “higher” brain functions such as personality and emotion that may associated with several gender-related mental disorders. In this study, the gender effects of functional connectivity, cortical lateralization and significantly differences in the PFC were investigated by using resting-state functional optical tomography (fOT) measurement. A total of forty subjects including twenty healthy male and twenty healthy female adults were recruited for this study. In the results, the hemoglobin responses are higher in the male group. Additionally, male group exhibited the stronger connectivity in the PFC regions. In the result of lateralization, leftward dominant was observed in the male group but bilateral dominance in the female group. Finally, the 11 channels of the inferior PFC regions (corresponding to the region of Brodmann area 45) are significant different with spectrum analysis. Our findings suggest that the resting-state fOT method can provide high potential to apply to clinical neuroscience for several gender-related mental disorders diagnosis.

Brain structure and spatial sensitivity profile assessing by near-infrared spectroscopy modeling based on 3D MRI data

The goal of this study is to prove that the light propagation in the head by used the 3-D optical model from in vivo MRI data set can also provide significant characteristics on the spatial sensitivity of cerebral cortex folding geometry based on Monte Carlo simulation. Thus, we proposed a MRI based approach for 3-D brain modeling of near-infrared spectroscopy (NIRS). In the results, the spatial sensitivity profile of the cerebral cortex folding geometry and the arrangement of source-detector separation have being necessarily considered for applications of functional NIRS. The optimal choice of source-detector separation is suggested within 3-3.5 cm by the received intensity with different source-detector separations and the ratio of received light from the gray and white matter layer is greater than 50%. Additionally, this study has demonstrated the capability of NIRS in not only assessing the functional but also detecting the structural change of the brain by taking advantage of the low scattering and absorption coefficients observed in CSF of sagittal view.

Comparison of ultrasound temperature imaging with infrared thermometry during radio frequency ablation

Radio frequency ablation (RFA) is a widely used alternative modality in the treatment of tumors. During RFA, temperature monitoring is essential to ensure accurate and appropriate thermal dosage. Ultrasound temperature imaging based on the detection of echo time-shift has been demonstrated to have good ability to monitor the temperature distribution. However, no study has proven that the region of ultrasound temperature imaging can correspond well to the practical temperature distribution in the tissue. In this study, we aim to combine ultrasound and infrared systems to clarify the correlation between ultrasound temperature imaging and the practical temperature distribution in a tissue. Five porcine livers (n = 5) were ablated using an RFA system and monitored with an ultrasound system to acquire raw backscattered data for temperature imaging. Meanwhile, an infrared imaging system was used to obtain the practical temperature map of the tissue. The results showed that the temperature distribution detected by ultrasound echo time-shift agreed with those obtained from the infrared image. When the tissue temperature was higher than 45°C, ultrasound temperature imaging is difficult to describe the behavior of the heat transfer in a homogeneous medium. In this study, we used the experimental setup based on combining ultrasound and infrared systems to confirm the reliability and limitations of ultrasound temperature imaging in RFA monitoring. Such an experimental design may be considered as an indispensable platform for the development and optimization of ultrasound temperature imaging techniques in RFA monitoring.

Discriminant analysis of functional optical topography for schizophrenia diagnosis

Abstract. Abnormal prefrontal function plays a central role in the cognition deficits of schizophrenic patients; however, the character of the relationship between discriminant analysis and prefrontal activation remains undetermined. Recently, evidence of low prefrontal cortex (PFC) activation in individuals with schizophrenia has also been found during verbal fluency tests (VFT) and other cognitive tests with several neuroimaging methods. The purpose of this study is to assess the hemodynamic changes of the PFC and discriminant analysis between schizophrenia patients and healthy controls during VFT task by utilizing functional optical topography. A total of 99 subjects including 53 schizophrenic patients and 46 age- and gender-matched healthy controls were studied. The results showed that the healthy group had larger activation in the right and left PFC than in the middle PFC. Besides, the schizophrenic group showed weaker task performance and lower activation in the whole PFC than the healthy group. The result of the discriminant analysis showed a significant difference with P value <0.001 in six channels (CH 23, 29, 31, 40, 42, 52) between the schizophrenic and healthy groups. Finally, 68.69% and 71.72% of subjects are correctly classified as being schizophrenic or healthy with all 52 channels and six significantly different channels, respectively. Our findings suggest that the left PFC can be a feature region for discriminant analysis of schizophrenic diagnosis.

The utility of far-infrared illumination in oxygenation dynamics as measured with near-infrared spectroscopy

Near-infrared spectroscopy (NIRS) is a noninvasive method for measuring the oxygenation in muscle and other tissues in vivo. For quantitative NIRS measurement of oxygenation dynamics, the vessel-occlusion test was usually applied as physiological intervention. There are several drawbacks of the vessel-occlusion method that include skin contact, uncomfortable and microcirculation block of patients. Thus, we propose the far-infrared (FIR) illumination as a new physiological intervention method in this paper. Our preliminary result shows a linear correlation of oxygenation dynamic signals between FIR illumination and arterial-occlusion test (AOT) that implies the FIR illumination could be applied for hemodynamic response measurement in clinical diagnosis.

Characterization of tooth structure and the dentin-enamel zone based on the Stokes–Mueller calculation

Abstract. This is the first study of dentin-enamel zone (DEZ) identification with tooth structure characterization based on the optical Stokes–Mueller measurement. Stokes vectors of a cross-sectional tooth slice were measured using various polarization inputs. The direction of the DEZ is different in enamel and dentin structures; therefore, the Stokes profiles can specifically characterize the structures based on the DEZ. This optical method, using polarimetry, provides a useful tool for characterizing tooth.