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Biomedical subjects

K C Chu

Publications and source records attributed to K C Chu.

At least 91 records · Page 5Linked to original sources
PubMed1975

Pattern recognitiion and structure-activity relationship studies. Computer-assisted prediction of antitumor activity in structurally diverse drugs in an experimental mouse brain tumor system.

This paper reports the application of pattern recognition and substructural analysis to the problem of predicting the antineoplastic activity of 24 test compounds in an experimental mouse brain tumor system based on 138 structurally diverse compounds tested in this tumor system. The molecules were represented by three types of substructural fragments, the augmented atom, the heteropath, and the ring fragments. Of the two pattern recognition methods used to predict the activity of the test compounds the nearest neighbor method predicted 83% correctly while the learning machine method predicted 92% correctly. The test structures and the important substructural fragments used in this study are given and the implications of these results are discussed.

Animals↗
PubMedDate not supplied

Breast cancer trends of black women compared with white women.

OBJECTIVE: To investigate why breast cancer mortality rates have decreased in the 1990's for white women but not for black women. DESIGN: Racial differences in breast cancer incidence, survival, and mortality rates were examined using regression methods and age-period-cohort models. SETTING: United States breast cancer mortality rates from 1970 through 1995, breast cancer incidence rates from 1980 through 1995, and 3-year survival rates from 1980 through 1993. The incidence and survival data are from the Surveillance, Epidemiology, and End Results Program, representing 11% of the US population, of the National Cancer Institute, Bethesda, Md. RESULTS: For both white and black women aged 30 to 39 years, breast cancer mortality rates began decreasing in 1987. For white women aged 40 to 79 years, breast cancer mortality rates declined after 1989, and for black women aged 40 to 69 years, mortality rates ceased increasing in the middle to late 1980s. Birth cohort trends were similar by race, but calendar period trends and survival rates differed. CONCLUSIONS: Declines in mortality rates in women younger than 40 years reflect a favorable birth cohort trend for women born after 1948 and likely reflect changes in risk factors. The increased early detection of breast cancer by mammography and improvements in breast cancer treatment appear to be contributing to the improving mortality trends in older women, although black women appear to have benefited less than white women from early detection and treatment advances. In addition, substantial increases in survival rates for white women with regional disease have contributed to their declining mortality rates and likely reflect an increasing use of beneficial adjuvant therapy.

Adult↗
PubMedDate not supplied

An expandable intravenous RF coil for arterial wall imaging.

An intravenous (iv) radiofrequency (RF) coil is proposed as a means of obtaining high resolution images of artery wall. The anatomic positioning of peripheral artery/vein pairs was investigated and a phantom mimicking the iliac artery/vein pair was constructed. Imaging results, comparing iv coils with external coils, demonstrated a potential 15- to 20-fold increase in signal-to-noise ratio (SNR) with iv coils. The SNR benefit was measured over a cylindrical volume, adjacent to the coil, and typical of artery position. Prototype expandable iv coils were constructed of Cu-Be loops and introduced via an 8-Fr catheter. The effects of local and remote iv coil tuning were investigated and local tuning was found to provide significant SNR benefits. The in vivo performance of iv RF coils was demonstrated in a porcine animal model. The iv coils were found to be an excellent alternative to intraarterial coils.

Animals↗
PubMedDate not supplied

Staging patterns and early cancer detection.

There is a great deal of indirect, nonexperimental evidence that a pattern of earlier-stage disease at diagnosis has a better outcome. Increased early detection activities can change, these stage patterns while various biases and the question of generalizability need to be kept in mind in their interpretation. The indirect evidences of possible benefit from early detection activities includes an increase in the number of cases detected, a pattern of more early- and less advanced-stage cases, an increase in the overall site-specific survival rate, and a decrease in the case fatality rate. Unless these intermediate markers are favorable, it is unlikely that early detection will reduce mortality. In addition, one should also differentiate a reduced incidence or a change in treatment as a cause for reduced mortality.

Black People↗
PubMedDate not supplied

Factors in the evaluation of 200 National Cancer Institute carcinogen bioassays.

In determining the carcinogenicity of chemical tested in a National Cancer Institute (NCI) bioassay, the following criteria are considered: (1) the adequacy of the bioassay data, (2) the presence of significantly increased incidences of tumor, (3) the adequacy of the number of animals at risk of developing tumors, (4) the adequacy of the dose of chemical administered, (5) the etiology and pathogenesis of the lesions, and (6) other factors that may influence an evaluation, such as a shortened latency period for tumor formation in dosed animals or the stability of the chemical. A decision tree for evaluating these factors is presented. A summary of the results of 200 NCl carcinogen bioassays is also reported. These procedures are presented in the hope that they may serve as discussion points for future developments in the field.

Animals↗
PubMedDate not supplied

A geometrically accurate vascular phantom for comparative studies of x-ray, ultrasound, and magnetic resonance vascular imaging: construction and geometrical verification.

A technique for producing accurate models of vascular segments for use in experiments that assess vessel geometry and flow has been developed and evaluated. The models are compatible with x-ray, ultrasound, and magnetic resonance (MR) imaging systems. In this paper, a model of the human carotid artery bifurcation, is evaluated that has been built using this technique. The phantom consists of a thin-walled polyester-resin replica of the bifurcation through which a blood-mimicking fluid may be circulated. The phantom is surrounded by an agar tissue-mimicking material and a series of fiducial markers. The blood- and tissue-mimicking materials have x-ray, ultrasound, and MR properties similar to blood and tissue; fiducial markers provide a means of aligning images acquired by different modalities. The root-mean-square difference between the inner wall geometry of the constructed model and the desired dimensions was 0.33 mm. Static images were successfully acquired using x-ray, ultrasound, and MR imaging systems, and are free of significant artifacts. Flow images acquired with ultrasound and MR agree qualitatively with each other, and with previously published flow patterns. Volume-flow measurements obtained with ultrasound and MR were within 4.4% of the actual values.

Carotid Arteries↗