Huihua Kenny Chiang

Diagnosis of oral cancer by light-induced autofluorescence spectroscopy using double excitation wavelengths

A cancer diagnostic algorithm, light-induced autofluorescence spectroscopy using double excitations wavelengths, was employed for distinguishing between cancerous and normal oral mucosa. For emission spectra at the shorter excitation wavelengths (280, 290, and 300 nm), the ratio between the area under 325-335 nm and the area under 465-475 nm was calculated. In the same way, for emission spectra at the longer excitation wavelengths (320, 330, and 340 nm), the ratio between the area under 375-385 nm and the area under 465-475 nm was calculated. Receiver operating characteristic curves were used to evaluate the performance of algorithms using single and the double (by combining shorter and longer) excitation wavelengths. The results showed that better performance, up to sensitivity 81.25%, specificity 93.75%, and positive predictive value 92.86%, could be achieved by using the double excitation wavelengths. The present study can be useful as a basis for further investigation on in vivo autofluorescence measurement and analysis using double excitation wavelength.

A PROBABILITY-BASED MULTIVARIATE STATISTICAL ALGORITHM FOR AUTOFLUORESCENCE SPECTROSCOPIC IDENTIFICATION OF ORAL CARCINOGENESIS

Abstract— A probability‐based multivariate statistical algorithm combining partial least‐squares (PLS) and logistic regression was developed to identify the development stages of oral cancer through analysis of autofluorescence spectra of oral tissues. Tissues were taken from a 7, 12‐dimethyl‐benz[a]anthracene‐induced hamster buecal pouch carcinogenesis model. Analyses were conducted at various excitation wavelengths, ranging from 280 nm to 400 nm in 20 nm increments, to assess classification performance at different excitations. For each excitation the PLS analysis and logistic regression were combined, on the basis of cross validation, to calculate the posterior probabilities of samples belonging to four stages of cancer development: normal tissues, hyperplasia, dysplasia and early cancers and frankly invasive cancers. Results showed that the 320 nm excitation wavelength optimally classified the cancer development stages: the accuracy rates for identifying samples at that excitation were 91.7%, 83.3%, 66.7% and 83.3% for the four respective stages. The average accuracy rate was 81.3%. These results suggest that the algorithm described in this study might be useful for the detection of human oral cancers.

Imaging pulsatile retinal blood flow in human eye

A functional Fourier domain optical coherence tomography instrument offering spectral Doppler imaging of in vivo pulsatile human retinal blood flow was constructed. An improved phase-resolved algorithm was developed to correct bulk motion artifacts. Spectral Doppler imaging provides complementary temporal flow information to the spatially distributed flow information of the color Doppler image by providing direct visualization of the Doppler spectrum of the flow whose pattern can be further quantified with various velocity envelope curves and their corresponding flow indices. The coefficient of repeatability on resistance index measurement was assessed by analyzing 14 measurements on two vessels within two normal subjects.

Noncontact detection of dry eye using a custom designed infrared thermal image system

Dry eye syndrome is a common irritating eye disease. Current clinical diagnostic methods are invasive and uncomfortable for patients. This study developed a custom designed noncontact infrared (IR) thermal image system to measure the spatial and temporal variation of the ocular surface temperature over a 6-second eye-open period. This research defined two parameters: the temperature difference value and the compactness value to represent the temperature change and the irregularity of the temperature distribution on the tear film. Using these two parameters, this study achieved discrimination results for the dry eye and the normal eye groups; the sensitivity is 0.84, the specificity is 0.83, and the receiver operating characteristic area is 0.87. The results suggest that the custom designed IR thermal image system may be used as an effective tool for noncontact detection of dry eye.

Eyes in the needle: novel epidural needle with embedded high-frequency ultrasound transducer--epidural access in porcine model.

Background:Epidural needle insertion is usually a blind technique where the rate of adverse events depends on the experience of the operator. A novel ultrasound method to guide epidural catheter insertion is described. Methods:An ultrasound transducer (40 MHz, a −6 dB fractional bandwidth of 50%) was placed into the hollow chamber of an 18-gauge Tuohy needle. The single crystal was polished to a thickness of 50 &mgr;m, with a width of 0.5 mm. Tissue planes were identified from the reflected signals in an A-mode display. The device was inserted three times into both the lumbar and thoracic regions of five pigs (average weight, 20 kg) using a paramedian approach at an angle of 35–40°. The epidural space was identified using signals from the ligamentum flavum and dura mater. Epidural catheters were placed with each attempt and placement confirmed by contrast injection. Results:The ligamentum flavum was identified in 83.3% of insertions and the dura mater in all insertions. The dura mater signal was stronger than that of the ligamentum flavum and served as a landmark in all epidural catheter insertions. Contrast studies confirmed correct placement of the catheter in the epidural space of all study animals. Conclusions:This is the first study to introduce a new ultrasound probe embedded in a standard epidural needle. It is anticipated that this technique could reduce failed epidural blocks and complications caused by dural puncture.

Effect of orchiectomy on the alpha adrenergic contractile response of dog prostate.

PURPOSE To investigate the effect of androgen deprivation on the alpha-adrenergic contractile response of the dog prostate using both in vitro and in vivo methods. MATERIALS AND METHODS In vitro muscle bath study: One month after surgery, responses to KCl (120 mM.) and norepinephrine (10(-8) to 10(-3)M.) of prostatic tissue strips (of the same size) from castrated (n = 6) and sham-operated (n = 6) adult mongrel dogs were determined. In vivo study: Before and 1 month after surgery, the intraprostatic urethral pressure response to intravenous norepinephrine administration of 6 castrated and 5 sham-operated adult dogs was examined. RESULTS (1) Before castration the serum level of testosterone was 1.24 +/- 0.2 ng./ml.; 1 month after castration, it had dropped to an undetectable level. (2) Histological examination of the prostates from castrated animals revealed profound atrophy of glandular tissue with a relatively increased stromal tissue component in each section. (3) In vitro study: The contractile responses to KCl and norepinephrine of individual prostate strips (same size) from castrated animals were significantly higher than control. However, if the response to norepinephrine was normalized to the response to KCl, there was no significant difference in response to norepinephrine between the 2 groups. In addition, the ED50 of the norepinephrine-stimulated contractile response was not changed by castration. (4) In vivo study: There was no significant change in intraprostatic urethral pressure response to intravenous norepinephrine administration after orchiectomy. CONCLUSIONS The results of this study show that the sensitivity of the alpha-adrenergic contractile response of the dog prostate is not affected by androgen deprivation, nor is alpha-adrenergic contractile activity of the dog prostate regulated by androgen.

Mechatronic experiments course design: a myoelectric controlled partial-hand prosthesis project

This paper describes a proposed laboratory project involving the design of a myoelectric-controlled partial-hand prosthesis to reinforce mechatronic education. The proposal focuses mainly on extract electromyogram (EMG) signals generated during contraction of the biceps. The EMG signals are first amplified and filtered by a laboratory-designed electronic circuit and then reprocessed using a microcontroller to drive the servomotor so that the designed prosthesis can be properly controlled. The project introduces students to component-level and system-level design and exposes them to the integration of a microcontroller, electronic circuits, sensors, and prosthesis mechanisms. Moreover, since the project results in a working prosthesis, student enthusiasm for mechatronic education increases, and they see its relevance to the field in applied engineering. Implementation of the laboratory project within the curriculum has been demonstrated to be highly motivational and educational and has even helped to attract more students to study mechatronic applications.

Partial Least-Squares Discriminant Analysis on Autofluorescence Spectra of Oral Carcinogenesis

A partial least-squares (PLS) discriminant analysis on the autofluorescence spectra of oral squamous cell carcinoma based on the cross-validation technique was conducted to discriminate among oral tissues at different cancer development stages. These tissues were obtained from hamsters of DMBA-induced buccal pouch carcinogenesis. The study on the fluorescence spectra of the cancer tissues revealed that 320 nm might be the optimal excitation wavelength, and it was selected for the discriminating analysis. The PLS discriminant plot based on cross-validation showed that tissues of oral carcinogenesis belonging to four clinically important cancer development stages—normal tissues, hyperplasia, dysplasia and early cancers, and frankly invasive cancers—could be classified by using the first two PLS factors that emerged from the fluorescence spectra at 320 nm excitation. The PLS factor loading plots of the first PLS factor of 320 and 360 nm excitations showed that the first PLS factor was correlated to the fluorescent structure changes. This study indicates that further development of the PLS discriminant analysis on the autofluorescence spectra may be useful for developing a simple and efficient discriminating algorithm for the identification of different stages of human oral carcinogenesis.

Partial least-squares algorithm for weights initialization of backpropagation network

Abstract This paper proposes a hybrid scheme to set the weights initialization and the optimal number of hidden nodes of the backpropagation network (BPN) by applying the loading weights and factor numbers of the partial least-squares (PLS) algorithm. The joint PLS and BPN method (PLSBPN) starts with a small residual error, modifies the latent weight matrices, and obtains a near-global minimum in the calibration phase. Performances of the BPN, PLS, and PLSBPN were compared for the near infrared spectroscopic analysis of glucose concentrations in aqueous matrices. The results showed that the PLSBPN had the smallest root mean square error. The PLSBPN approach significantly solves some conventional problems of the BPN method by providing the good initial weights, reducing the calibration time, obtaining an optimal solution, and easily determining the number of hidden nodes.

Doppler angle and flow velocity estimations using the classic and transverse Doppler effects

Current clinical Doppler ultrasound systems could only measure the flow vector parallel to the ultrasound beam axis, and the knowledge of the Doppler angle (beam-to-flow angle) is needed to calculate the real flow velocity. Currently, the Doppler angle is determined visually by manually aligning a vessel axis marker along the blood vessel on the duplex scan image of the ultrasound. The application of this procedure is often limited by practical constraints; therefore, measurements are not reliable. In order to overcome this problem, the authors developed a simple Doppler angle and flow velocity estimation method using a combination of the classic and transverse Doppler effects. This method uses only a single focused annular array transducer to estimate the Doppler angle and the flow velocity. The authors have verified experimentally that this method is successful for measuring constant flow in a flow phantom between 45 degrees and 80 degrees Doppler angle. The standard deviation of the estimated Doppler angles is less than 4.5 degrees . This method could be implemented easily in medical Doppler ultrasound systems to automatically estimate the Doppler angle and the flow velocity.