1,720,992 research outputs found
Subjective breast cancer grading - Analyses of reproducibility after application of Bayesian belief networks
No full textOBJECTIVE: To examine the influence of Bayesian belief networks (BBNs) on the reproducibility of subjective breast cancer grading.
STUDY DESIGN: Twenty samples were analyzed for intraobserver and 128 samples for interobserver reproducibility using the Bloom-Richardson and Helpap grading systems. The expression of diagnostic features was evaluated subjectively, and for each a decision it was determined to what extent it represented one of the different outcomes. Evidence was then entered, for each diagnostic feature, into four different BBNs, recently described for breast cancer grading, in the form of a relative likelihood ratio vector.
RESULTS: With all cases considered, the use of decision support based on the Bloom-Richardson and Helpap grading systems did not improve intraobserver reproducibility. This was found to be 68% and 80% in subjective gradings, respectively, and 60% and 70% in the BBN-supported method. Interobserver reproducibility was not improved (58% and 70% in subjective gradings and 51-59% based on assessment with decision support). However, when only cases associated with high beliefs were considered, both intraobserver reproducibility (agreement rose from 68% to 93%) and interobserver reproducibility (agreement rose from 60% to 87%) of BBN-supported gradings exceeded the results of subjective assessments.
CONCLUSION: The results showed that the observers did not reach the same diagnosis (or grade) and that their observational assessment of histologic features lacked agreement. Since BBNs reflected only the data entered, poor agreement existed in the contribution to the final diagnostic belief by the different features and, ultimately, in belief in the final decision
Management of Uncertainty In Breast-cancer Grading With Bayesian Belief Networks.
No full textOBJECTIVE: 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
Sources and nature of variation in DNA analysis of follicular thyroid adenoma.
No full textWe investigated the sources and nature of variation that may occur in the DNA analysis of thyroid adenomas from cytological and histological samples. Imprints and smears gave identical results. However, the nuclear area was higher in smears where the optical density of the nuclei was lower. In measuring imprints, the interactive selection of nuclei was preferred to the automatic, because the risk of measuring nuclear fragments or undesired objects was thus avoided. The reproducibility and the variation of the DNA measurements depended on the degree of observer training in quantitative pathology, the method of field selection, and the type of instrumentation. Biological variation in the spatial distribution of nuclei with different ploidy values in some adenomas seemed to hide the influence of section thickness on measurements. Our data seem to suggest that it is best to apply a constant section thickness and 5 micron sections seem acceptable
Multivariate classifications of transitional cell tumors of the bladder: nuclear abnormality index and pattern recognition analysis.
No full textThe authors report their experiences in applying two types of computer-aided multivariate classification systems in transitional cell tumors of the bladder. The systems are based on nuclear changes in urothelial papillary lesions. 19 out of 54 parameters, selected on the basis of the overlapping area between contiguous grades and the monotonic function, were combined mathematically to obtain the nuclear abnormality index. This index expresses the progressive nuclear abnormalities as a single number on a continuous scale from 0.5 to 2.6. The standard deviation (SD) of the 10 largest nuclear area values in the lower half of epithelial thickness (L), the mean perimeter (L), the SD of the roundness factor in the upper half of epithelial thickness (U), the SD of the logarithm of area (L) and the percentage of round nuclei (U) represent the smallest, the most discriminant and the least correlated set of features for the pattern recognition analysis. The latter shows an agreement of 92% between computer and histologic classifications-estimated by applying Bayes theorem. A good correlation exists between nuclear abnormality index and computer grading by pattern recognition analysis
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Quantitative-analysis of Quadriceps Muscle Biopsy In Systemic-sclerosis.
No full textThe lesser diameter of the fibers, separately of type 1 and type 2 fibers, and the capillary density evaluated as number of capillaries/area and number of capillaries/fiber were quantitatively estimated in muscle biopsies from 12 patients with systemic sclerosis. Nine patients with polymyositis or rheumatoid arthritis and six patients with muscle dystrophy and neurogenic atrophy served as controls. The results showed that patients with systemic sclerosis had low values of the lesser diameter of the fibers. This reduction was most obvious in type 2 fibers. The capillaries were also significantly reduced when compared with the control groups. When considering the capillaries/fiber ratio, seven out of eight patients with values lower than 0.7 belonged to the systemic sclerosis group. In systemic sclerosis the capillary density values were not significantly correlated with those of the lesser diameters of the fibers
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