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Biomedical subjects

D Thompson

Publications and source records attributed to D Thompson.

At least 91 records · Page 5Linked to original sources
PubMed1995

Management of uncertainty in breast cancer grading with Bayesian belief networks.

OBJECTIVE: To examine the potential of different constructs of Bayesian belief networks (BBN) to manage uncertainty in breast cancer grading. STUDY DESIGN: We developed four networks, two based on Bloom-Richardson's and two on Helpap's grading systems. The function of the networks was based either on an expert's experience or frequency counts derived from subjective grading of a large number of samples. The four BBNs were tested on 20 specimens, and the resulting final beliefs were compared with the subjective gradings. RESULTS: The BBNs showed agreement with the subjective gradings in 60-85% of cases. Different constructs of BBNs, however, differed in their performance. The mean beliefs in frequency-based networks were slightly higher than in experience-based networks. In addition, as compared with the Bloom-Richardson-based networks, the Helpap-based BBNs resulted in higher maximum beliefs but produced a larger fraction of discrepancies with the subjectively graded cases. Depending on the type of network, 65-90% of the BBN grades were associated with high beliefs. CONCLUSION: The results suggest that for reliable results, grading systems with more than three or four variables may be necessary. When based on relevant information, BBNs seem to have the potential to become a valuable method of assisting the pathologist in breast cancer grading.

Breast Neoplasms↗
PubMed1995

Image segmentation of cribriform gland tissue.

OBJECTIVE: To develop procedures for the segmentation of cribriform prostatic glands. STUDY DESIGN: A knowledge-guided procedure following a model-based reasoning process was developed in the context of a set of interacting expert systems for machine vision in histometry. RESULTS: With 78 entities in the knowledge file, fully automated, correct segmentation of approximately 70-80% of cribriform glands was attained--i.e., outlining of histologic components agreed with visual assessment. Measurement of gland size, shape, lumen area, number of lumina per gland, epithelial layer thickness, degree of cribriformity and determination of completeness of lining of a gland by a basal cell layer could be taken from the correctly segmented images. CONCLUSION: The automated procedure allows a histometric characterization of premalignant and malignant prostatic lesions. Extension of system capabilities to the utilization of spectral information is expected to allow an increase in the correct segmentation rate.

Humans↗
PubMed1995

Diagnostic and prognostic decision support systems.

Diagnostic decision support systems provide a quantitative evaluation of diagnostic evidence and the capability to combine diagnostic evidence in such a manner that a numeric measure of certainty in a final diagnostic recommendation results. Generally, expert systems serve to establish a diagnostic decision, inference networks allow a detailed analysis of the diagnostic value of diagnostic clues, case-based reasoning systems are designed to provide a prognostic assessment targeted to an individual patient. In all of these systems, symbolic information, i.e., traditional diagnostic, linguistic terms and concepts are processed and quantitatively evaluated.

Decision Support Techniques↗
PubMed1995

Clinical applications of Bayesian belief networks in pathology.

Bayesian belief networks (BBNs) are a novel tool for representing knowledge about diagnostic decision making and for obtaining a numerical measure of certainty in the final diagnosis. Belief networks have been applied to the pathological assessment of breast, prostate and skin lesions and have been shown to provide consistency in the grading of microscopic features and improve diagnosis. These applications are reviewed in the current paper. The application of BBNs has been further facilitated through the use of standardised imagery which is stored digitally and used to enter evidence into a BBN. It is predicted that the further development of BBNs with improved logical capabilities represent the key to improved decision making in pathology.

Bayes Theorem↗
PubMed1994

Carpal tunnel syndrome among grocery store workers.

The California Department of Health Services evaluated carpal tunnel syndrome (CTS), a median nerve entrapment condition associated with forceful and repetitive wrist motion, among grocery store workers at a large California supermarket where a CTS cluster had been reported. Forceful and repetitive wrist motion was measured, in three exposure levels, through a job classification scheme based upon type of work tasks and average time per week spent performing these tasks. A medical questionnaire and measurements of median sensory nerve conduction were used to measure CTS. CTS prevalence was 23% based upon a sample of 56 participants drawn from a workforce of 69 employees. A relative risk of 8.3 (95% confidence interval 2.6-26.4) for a history of CTS-like symptoms between the high and low exposure level groups held up after adjustment for the potential confounders of age, sex, alcohol consumption, and high-risk medical history. It was concluded that the basic principles of good ergonomic design should be used to prevent or diminish the risk of musculoskeletal injury in the workplace.

Adult↗
PubMed1994

Cholelithiasis and bile acid absorption after truncal vagotomy and gastroenterostomy.

Gallbladder disease in the form of gallstones demonstrated by ultrasonography or previous cholecystectomy was found in 15 of 26 women of median age 69 (range 52-82) years who had had truncal vagotomy and gastroenterostomy performed a median of 27 (range 11-30) years previously, compared with eight of 31 healthy age- and sex-matched controls drawn from the community (P < 0.02). Bile acid malabsorption identified by retention of 23-selena, 25-homotaurocholate (75SeHCAT) occurred in only two of the 26 patients after vagotomy and there was no relationship between retention and the presence or absence of gallbladder disease. The serum concentration of 7 alpha-hydroxycholestenone, an indicator of bile acid turnover, was significantly lower in patients with gallbladder disease after vagotomy than in controls (mean(s.e.m.) 19.1(3.7) versus 31.4(4.4) ng/ml, P < 0.05). Bile acid malabsorption does not play a significant role in the pathogenesis of gallstones after vagotomy but decreased bile acid synthesis may be important. There is no correlation between retention of 75SeHCAT and 7 alpha-hydroxycholestenone levels in patients after vagotomy, indicating that bile acid synthesis and absorption are uncoupled in this situation.

Absorption↗
PubMed1994

Effect of retinoic acid and interferon alpha on granulocyte-macrophage colony forming cells in chronic myeloid leukemia: increased inhibition by all-trans- and 13-cis-retinoic acids in advanced stage disease.

Granulocyte-macrophage colony forming units (CFU-GM) from patients with advanced stage chronic myelogenous leukemia (CML), i.e. in blastic crisis (BC) or accelerated phase (AP), were inhibited by all-trans-retinoic acid (tRA) approximately 1000-fold more potently than those from chronic phase (CP) CML patients (median IC50 = 10(-9) M tRA for six CML-AP/BC cases vs > 10(-6) M tRA for seven CML-CP cases). A similar activity pattern was observed for the stereoisomer 13-cis-RA (cRA). There was no apparent correlation of CFU-GM retinoid sensitivity with cloning efficiency or other colony characteristics. Interferon alpha-2a (INF alpha) alone strongly inhibited CFU-GM growth in all four CML-AP/BC cases (IC50 < or = 250 IU/ml) and three out of seven CML-CP cases (IC50 < or = 500 IU/ml), but there was little or no interactive effect between various concentrations of tRA and INF alpha (50 IU/ml) on CFU-GM from either CML-AP/BC or CML-CP cases. These results suggest that CML-AP/BC CFU-GM have some intrinsic molecular alteration(s) which markedly enhances their responsiveness to tRA and cRA, which may be clinically exploitable.

Adult↗
PubMed1994

Quantitative study of ductal breast cancer progression. Morphometric evaluation of phenotypical changes occurring in benign and preinvasive epithelial lesions.

Fifty-nine cases of Breast Epithelial Proliferative Lesions (BEPL) and Ductal Carcinoma in Situ (DCIS), were studied by image analysis, to evaluate the nuclear changes occurring in the conventional diagnostic categories of ductal hyperplasia, atypical ductal hyperplasia and DCIS with quantitative methods. Diagnosis reproducibility is the main practical problem of these breast lesions. In fact, with subjective methods, the reproducibility appears to be very low and precarious especially for clinical demands. The objective, quantitative evaluation of cell phenotypical changes should be the method for both practical diagnostic problems and study of ductal cancer progression. The distribution pattern of the data in the feature, obtained with quantitative analysis, strongly suggests a continuum of changes, indicating an evolutionary process of Breast Ductal Carcinoma (BDC) progression in its preinvasive stage. Each observed case may be characterised by its own cellular, objective alterations and a progressive trend toward BDC can be stated. Since the actual changes of the proliferative phenotypes can be measured, and the values are reproducible, karyometric measurement may allow an objective grading of individual cases.

Adult↗
PubMed1994

Expert system support using Bayesian belief networks in the diagnosis of fine needle aspiration biopsy specimens of the breast.

AIM: To develop an expert system model for the diagnosis of fine needle aspiration cytology (FNAC) of the breast. METHODS: Knowledge and uncertainty were represented in the form of a Bayesian belief network which permitted the combination of diagnostic evidence in a cumulative manner and provided a final probability for the possible diagnostic outcomes. The network comprised 10 cytological features (evidence nodes), each independently linked to the diagnosis (decision node) by a conditional probability matrix. The system was designed to be interactive in that the cytopathologist entered evidence into the network in the form of likelihood ratios for the outcomes at each evidence node. RESULTS: The efficiency of the network was tested on a series of 40 breast FNAC specimens. The highest diagnostic probability provided by the network agreed with the cytopathologists' diagnosis in 100% of cases for the assessment of discrete, benign, and malignant aspirates. Atypical probably benign cases were given probabilities in favour of a benign diagnosis. Suspicious cases tended to have similar probabilities for both diagnostic outcomes and so, correctly, could not be assigned as benign or malignant. A closer examination of cumulative belief graphs for the diagnostic sequence of each case provided insight into the diagnostic process, and quantitative data which improved the identification of suspicious cases. CONCLUSION: The further development of such a system will have three important roles in breast cytodiagnosis: (1) to aid the cytologist in making a more consistent and objective diagnosis; (2) to provide a teaching tool on breast cytological diagnosis for the non-expert; and (3) it is the first stage in the development of a system capable of automated diagnosis through the use of expert system machine vision.

Bayes Theorem↗
PubMed1994

Haemorrhage associated with silastic dural substitute.

Three cases of haemorrhage after the use of a silastic dural substitute are presented. In all cases the implant was removed and further haemorrhage has not occurred. Published work is reviewed and the implications for the continued use of silastic are discussed.

Adult↗
PubMed1994

Corticotrophin-releasing hormone and beta-endorphin in labour.

The objectives of this study were to determine whether the maternal plasma corticotrophin-releasing hormone (CRH) concentration influences the amount of uterine contractility induced by infused oxytocin during induction of labour, and secondly to assess changes in CRH and beta-endorphin in response to stress during labour. Serial plasma CRH and beta-endorphin measurements were made in 40 women undergoing induction of labour and correlated with uterine contractility, cervical dilatation, length of labour, analgesic usage and fetal distress. The plasma CRH concentration did not change throughout labour. In subjects receiving infused oxytocin there was a significant positive correlation between plasma CRH and the amount of uterine activity, and a high plasma CRH level was associated with shorter labour. The plasma beta-endorphin level rose with progressive cervical dilatation and fell after epidural anaesthesia. The plasma CRH level did not correlate with the plasma beta-endorphin level or rise with fetal distress. We conclude that high levels of maternal plasma CRH are associated with an increase in the uterine contractile response to infused oxytocin. The maternal plasma CRH level does not vary in response to maternal or fetal stress, but beta-endorphin secretion does rise in response to the stress of labour and is influenced by pain perception.

Adult↗
PubMed1994

Mothers of children with chronic conditions: supportive and stressful interactions with partners and professionals regarding caregiving burdens.

Ninety mothers appraised the specific sources and types of social support they received in relation to specific types of demands of caring for a child with a chronic condition. Qualitative data were collected during home interviews with the mothers of children with diabetes, spina bifida, or cystic fibrosis. Virtually all of the mothers described primary caregiver demands that were directly related to the child's condition, such as physical care, health care in illness situations, and the child's psychological and social development. Many mothers also reported secondary demands related to their own needs, family roles and relationships, and the mother's activities outside the home. Mothers experienced gaps in the support provided for specific caregiving burdens and encountered stressful interactions with their partners and health professionals in particular.

Adolescent↗