Biomedical subjects

H K Chiang

Publications and source records attributed to H K Chiang.

6 recordsLinked to original sources

PubMed1999

Implementation of spectral width Doppler in pulsatile flow measurements.

In this paper, we present an automatic beam-vector (Doppler) angle and flow velocity measurement method and implement it in pulsatile flow measurements using a clinical Doppler ultrasound system. In current clinical Doppler ultrasound flow velocity measurements, the axis of the blood vessel needs to be set manually on the B-scan image to enable the estimation of the beam-vector angle and the beam-vector angle corrected flow velocity (the actual flow velocity). In this study, an annular array transducer was used to generate a conical-shaped and symmetrically focused ultrasound beam to measure the flow velocity vectors parallel and perpendicular to the ultrasound beam axis. The beam-vector angle and flow velocity is calculated from the mode frequency (f(d)) and the maximum Doppler frequency (f(max)) of the Doppler spectrum. We develop a spectrum normalization algorithm to enable the Doppler spectrum averaging using the spectra obtained within a single cardiac cycle. The Doppler spectrum averaging process reduces the noise level in the Doppler spectrum and also enables the calculation of the beam-vector angle and flow velocity for pulsatile flows to be measured. We have verified the measurement method in vivo over a wide range of angles, from 52 degrees to 80 degrees, and the standard deviations of the measured beam-vector angles and flow velocities in the carotid artery are lower than 2.2 degrees and 12 cm/s (about 13.3%), respectively.

Blood Flow Velocity↗

PubMed1999

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.

Algorithms↗

PubMed1999

A probability-based multivariate statistical algorithm for autofluorescence spectroscopic identification of oral carcinogenesis.

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-dimethylbenz[a]anthracene-induced hamster buccal 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.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed1999

Autofluorescence spectroscopic differentiation between normal and cancerous colorectal tissues by means of a two-peak ratio algorithm.

We conducted an ex vivo study with light-induced autofluorescence spectroscopy to distinguish between normal and cancerous colorectal tissues. A total of 20 normal and 20 cancerous tissue samples were obtained from 20 patients undergoing oncologic surgery of the colon and rectum. The tissue diagnosis was confirmed histologically. After excitation, the autofluorescence spectra of each sample were measured and recorded. To determine the most appropriate excitation wavelength, we analyzed the autofluorescence spectra at excitation wavelengths of 280 to 400 nm, in 10-nm increments. To distinguish between normal and cancerous tissues, we first calculated the "two-peak ratio" (the ratio of the integrated intensity of the first peak +/- 6 nm to the integrated intensity of the second peak +/- 6 nm) of the autofluorescence spectra. By applying receiver operating characteristic (ROC) curves and calculating the areas under the ROC curves (AUC), we found 330 and 340 nm to be the most appropriate excitation wavelengths to distinguish between cancerous and normal colorectal tissue. When approximate thresholds were selected, autofluorescence spectroscopy with 330 nm excitation yielded a sensitivity of 85%, a specificity of 90%, and a positive predictive value of 89% for detection of cancerous tissue. The ex vivo autofluorescence study and two-peak ratio algorithm developed herein may be very useful for developing an algorithm for in vivo diagnosis of colorectal cancer.

Colorectal Neoplasms↗

PubMed1998

Autofluorescence in normal and malignant human oral tissues and in DMBA-induced hamster buccal pouch carcinogenesis.

Light-induced fluorescence spectroscopy was conducted on human oral malignant and normal tissues. Under 330-nm excitation wavelength, significant differences in fluorescence intensity were observed around 380- and 460-nm emission. Furthermore, 7,12-dimethylbenz[a]anthracene (DMBA)-induced carcinogenesis in hamster buccal pouch was investigated to elucidate whether similar alterations of fluorescence spectroscopy occurred during the development of squamous cell carcinoma. Similar to the spectral profiles of human oral malignant and normal tissues, the most intense fluorescence peaks in the pouches occurred at 380 nm and 460 nm emission under 330 nm excitation wavelength. At 380 nm emission, the fluorescence intensity of normal pouch mucosa was stronger than those of DMBA-treated abnormal tissues at different stages of carcinogenesis. However, at 460 nm emission, the fluorescence intensity of DMBA-treated tissues was not only stronger than that of normal pouch mucosa but also shifted to 470 nm. These results suggest that under 330 nm excitation wavelength fluorescence spectroscopy may be useful for the detection of oral malignant lesions.

9,10-Dimethyl-1,2-benzanthracene↗

PubMedDate not supplied

New system for long-term monitoring of sperm motility: EDTA effect on semen.

Many drugs act as sperm stimulants and are of clinical value for male infertility. Current research deals with the physiological mechanisms of sperm motility/sperm stimulation and how long the effect lasts. For such a study, long-term monitoring of sperm motility becomes essential for traditional semen evaluation. A new system was designed to deal with the microscopic images of semen. Its performance was evaluated by studying the effect of EDTA on sperm motility. EDTA increased sperm curvilinear velocity (Vcl) and straight-line velocity (Vsl) by 31 and 20%. EDTA also prolonged the duration of motility by 68 and 61%, respectively. However, EDTA had less effect on the linearity of forward progression (Lin). The proposed system can analyze semen and does well at monitoring sperm motility for short term and long term. It may be valuable to test the possible role of sperm stimulation for male infertility and assisted reproduction.

Algorithms↗