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Biomedical subjects

L G Keith

Publications and source records attributed to L G Keith.

At least 19 recordsLinked to original sources
PubMed2006

The potential role of dynamic thermal analysis in breast cancer detection.

BACKGROUND: It is presently well accepted that the breast exhibits a circadian rhythm reflective of its physiology. There is increasing evidence that rhythms associated with malignant cells proliferation are largely non-circadian. Cancer development appears to generate its own thermal signatures and the complexity of these signatures may be a reflection of its degree of development. The limitations of mammography as a screening modality especially in young women with dense breasts necessitated the development of novel and more effective screening strategies with a high sensitivity and specificity. The aim of this prospective study was to evaluate the feasibility of dynamic thermal analysis (DTA) as a potential breast cancer screening tool. METHODS: 173 women undergoing mammography as part of clinical assessment of their breast symptoms were recruited prior to having a biopsy. Thermal data from the breast surface were collected every five minutes for a period of 48 hours using eight thermal sensors placed on each breast surface [First Warning System (FWS), Lifeline Biotechnologies, Florida, USA]. Thermal data were recorded by microprocessors during the test period and analysed using specially developed statistical software. Temperature points from each contra-lateral sensor are plotted against each other to form a thermal motion picture of a lesion's physiological activity. DTA interpretations [positive (abnormal thermal signature) and negative (normal thermal signature)] were compared with mammography and final histology findings. RESULTS: 118 (68%) of participating patients, were found to have breast cancer on final histology. Mammography was diagnostic of malignancy (M5) in 55 (47%), indeterminate (M3, M4) in 54 (46%) and normal/benign (M1, M2) in 9 (8%) patients. DTA data was available on 160 (92.5%) participants. Using our initial algorithm, DTA was interpreted as positive in 113 patients and negative in 47 patients. Abnormal thermal signatures were found in 76 (72%) out of 105 breast cancer patients and 37 of the 55 benign cases. Then we developed a new algorithm using multiple-layer perception and SoftMax output artificial neural networks (ANN) on a subgroup (n = 38) of recorded files. The sensitivity improved to 76% (16/21) and false positives decreased to 26% (7/27) CONCLUSION: DTA of the breast is a feasible, non invasive approach that seems to be sensitive for the detection of breast cancer. However, the test has a limited specificity that can be improved further using ANN. Prospective multi-centre trials are required to validate this promising modality as an adjunct to screening mammography especially in young women with dense breasts.

Journal Article↗
PubMed2001

Maternal race/ethnicity and twinning rates in the United States, 1989-1991.

OBJECTIVE: To utilize United States birth certificate data (years 1989-1991) to examine the effects of race/ethnicity on twinning rates. STUDY DESIGN: We used a database of birth certificate data for the United States (years 1989-1991) available on CD-ROM from the United States National Center for Health Statistics. This linked birth/infant death data set included a total of 12,036,234 birth records, of which 279,073 were twins. Excluded from the analysis were 15,086 twin birth records (5.4%) based upon previously described exclusion criteria. Statistical analysis included a series of univariate analyses to determine the rates of twinning between different racial/ethnic groups correlated with maternal age, education, marital status and place of birth. Comparisons were analyzed using the chi 2 test, with significance at P < .05. RESULTS: The overall twinning rate was 2.26%, with the lowest rate observed in the group denoted non-Hispanic other (1.67%) and highest among non-Hispanic blacks (2.69%). Twinning rates within various groups representing Hispanics ranged from 1.76% to 2.08%. The twinning rate was significantly higher among U.S.-born as compared to non-U.S.-born women (2.34% vs. 1.88%, P < .005) except for Puerto Ricans, Cubans and Central/South Americans, for whom the reverse was true. Women aged 35-39 had the highest twinning rate (3.05%), whereas women aged 15-19 had the lowest; that trend persisted in all racial/ethnic groups. The study showed a nonsignificant relationship between marital status or education and twinning rate. CONCLUSION: Race/ethnicity studies can be useful in designing programs that may maximize health outcomes of twins in a racially diverse population.

Adult↗
PubMed2000

Conditions predisposing to maternal mortality in twins and singletons, US birth cohort 1989.

Twin pregnancy is one of the most important conditions associated with increased perinatal mortality and morbidity. The consequences of twin pregnancy on the mother have not been explored in great detail. The aim of this study was to analyze the population-based data from the United States and delineate the various conditions of twin pregnancies which predispose to maternal mortality. Results of this study show that multiple pregnancy is strongly associated with maternal mortality and requires further analysis in order to prepare appropriate therapeutic and prophylactic protocols.

Adolescent↗
PubMed2000

Zygosity of twins: is it time for a new terminology?

The term zygosity reflects the origin of twins--when twins are monozygotic, they are derived from a single fertilized ovum; when twins are dizygotic--the come from two fertilized ova. Zygosity assessment seemed straightforward 50 years ago. Currently, as more information and more technology becomes available, zygosity testing becomes a real problem. It is important to realize the importance of correct zygosity testing not only in the antepartum care of the pregnant mother, but more importantly--during the whole lifetime of twin individuals. This paper discusses revolving around zygosity, methods of assessment, their limitations and proposes new terminology which incorporates the recent knowledge about early human development.

Algorithms↗
PubMed2000

[Peculiarities of multiple pregnancy: epidemiology].

The epidemiology of multiple pregnancy is complex and depends on various factors including age, race, genetic and environmental factors, season of conception and, more recently, iatrogenic factors. In recent years, twinning rate increased dramatically especially in countries where ovulation induction and assisted reproductive technologies are widely used. Multiple pregnancies are most frequent in Nigeria where majority of them are dizygotic. The lowest frequency of twinning is observed in Japan where almost 70% of multiples are monozygotic. This paper discusses genetic, environmental and sociocultural factors which are related to the "epidemic" of multiples.

Age Distribution↗
PubMed2000

[Peculiarities of multiple pregnancy: embryology].

Multiple pregnancies are not physiologic in humans and the understanding of the pathogenesis of this phenomenon is not fully established. Embriology of multiple pregnancy has been extensively investigated and this paper presents the phases of embrional development of monozygotic and dizygotic twins.

Embryonic and Fetal Development↗
PubMed2000

[Peculiarities of multiple pregnancy: diagnosis].

Before ultrasound was aggressively introduced into everyday obstetrical practice, diagnosis, prophylaxis and active pre- and perinatal management were at best inadequate, but more often nonexistent. Twin pregnancies were complicated by high perinatal morbidity and mortality. The use of classical radiography was limited due to proven teratogenic and carcinogenic properties. Introduction of ultrasound dramatically changed the obstetrician's approach to twin pregnancy management. This paper discusses in detail the recent advances in ultrasound diagnosis of twin pregnancy.

Female↗
PubMed2000

[Peculiarities of multiple pregnancy: complications].

Multiple pregnancies are considered high risk. This qualification is associated with the multitude of conditions which are known to complicated these pregnancies. Early diagnosis of these complications is the fundamental element of clinical managements. In numerous cases therapeutic protocols are widely known and in many others intensive monitoring and appropriate management may save the fetus from early and late complications. This paper will discuss the most common prenatal and perinatal complications associated with multiple pregnancies as well as the most widely accepted therapeutic protocols.

Abnormalities, Multiple↗
PubMed1999

Projections of population-based twinning rates through the year 2100.

OBJECTIVE: To present the first compilation of population-based twinning rates published after the year 1990 and to project population-based twinning rates through the year 2100. STUDY DESIGN: We searched the Internet-based MEDLINE database for articles published after 1990 in which population-based twinning rates were described. We used population-based data from national statistical authorities from Australia, Austria, Canada, Finland, Hong Kong, Israel, Japan, Norway, Singapore and Sweden, published by Y. Imaizumi in a recent article. U.S. figures were based on data from the National Center for Health Statistics. Annual growth rates of twinning were calculated and graphed, making the assumption that these rates would remain constant throughout the next century. RESULTS: Our report presents the most recent population-based twinning rates. When projected through the year 2015, twinning rates reach figures that could best be described as derived from a Jules Verne novel: Sweden, in this model, would have four times more twin than singleton births. CONCLUSION: We strongly suggest that physicians reexamine their patterns of prescribing ovulation-inducing agents, which carry a greatly increased risk of multiple pregnancy.

Adult↗
PubMed1997

Perception of risk, choice of maternity site, and socio economic level of twin mothers.

The objective of this study was to determine if access to high level health facility (level 3 perinatal center) is related to socio-economic level of the mother and to her perception of risk for a twin birth. A retrospective questionnaire was administrated to the mothers of twins during the first post parum days in each of the 27 maternity sites within a defined geographical district near Paris (Hauts de Seine). The survey instrument was designed to precisely characterize the socioeconomic status of the parents, to measure the perceived risk for the twins expressed by the mother, to measure the relationship between the choice of a maternity site (level 1, 2 or 3) by socioeconomic level, and to measure the fetal and neonatal death rates by socioeconomic status. The opinion of mothers of twins about specific risk for her and for her children is very different by socioeconomic levels, as is the choice of level 3. This is discussed with the rates of fetal and neonatal death rates by socioeconomic level. In the absence of a policy of regionalization of perinatal care, the discriminant factor for access to high level care (level 3 maternity site) is the socioeconomic level.

Cohort Studies↗