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At least 433 records · Page 24Linked to original sources
PubMed1991

Problem area formation as an element of computer aided diagnosis: a comparison of two strategies within quick medical reference (QMR).

INTERNIST-I's use of "partitioning" to group related diagnoses into problem areas (for competitive consideration and elimination during case analysis) is felt to be the source of many of its strengths as well as some of its weaknesses. QMR, INTERNIST-I's successor program, embodies a homology function which can act as an alternative to the partitioner for problem area formation. This study undertakes a comparison of the problem areas generated by the INTERNIST-I partitioning algorithm, the QMR homology function, and expert clinicians; it finds the correlation to be poor. The authors then discuss another method of problem area formation which might better mimic a human clinician and provide an alternative approach in diagnostic computer-aided decision making.

Algorithms↗
PubMed1989

Computer system and software of POSITOLOGICA II: a whole body positron emission tomograph.

Since a whole body PET-scanner POSITOLOGICA II was installed at the National Institute of Radiological Sciences (NIRS) in 1982, improvements of the computer system and developments of new software have been continuously made to correspond to clinical requirements. As the result, POSITOLOGICA II possesses one of the most powerful systems and sophisticated software in Japan. This report describes the present status of the computer system and software of POSITOLOGICA II. It also discusses problems which still exist and proposes a future computer system for the PET study.

Brain↗
PubMed1989

Reliability of the Cobb angle index derived by traditional and computer assisted methods.

The reliability of the traditional Cobb angle index, which at present exhibits a wide range of reported values, was determined in this study and amounted to a within subject error of +/-4.3 degrees and a between subject error of +/-4.9 degrees. An attempt to pinpoint the source of this variability by investigating the influence of choice of end vertebrae proved inconclusive. The reliability of a computer assisted Cobb angle index, developed to improve measurement accuracy, was also examined and an estimated within subject error of +/-1.5 degrees and a between subject error of +/-1.6 degrees obtained. A comparison of the traditional and computer assisted methods indicates a high correlation between the Cobb angle derived using the two methods when measuring like curves and an improved reliability obtained by the computer method. Such an improvement is worth implementing clinically but of course the availability of a computer and digitizer and a little extra time for an operator to input the X-ray coordinates may be a barrier to its general use.

Diagnostic Errors↗
PubMed1996

Grading and prognosis of infiltrating ductal breast carcinoma by mean nuclear volume estimates.

OBJECTIVE: Quantitative evaluation of nuclear size in breast cancer is performed with the aim of investigating whether the data obtained are related to subjective grading and prognosis. STUDY DESIGN: Unbiased stereologic estimates of the volume-weighted mean nuclear volume (nuclear vv) in paraffin-embedded tissue from 44 specimens of infiltrating ductal breast carcinoma were obtained by the point-sampled intercepts method. RESULTS: Histologically graded cases showed an overlap in nuclear vv estimates, but significant differences were demonstrated in which averaged values increased from grade 1 to 3 breast carcinomas. Nuclear vv estimates in grade 3 breast carcinoma (mean, 495.4 microns 3; SD, 101.7 microns 3) were significantly larger than those in grades 1 (mean, 327.8 microns 3; SD, 90.9 microns 3) and 2 (mean, 409.9 microns 3; SD, 72.6 microns 3) (P < .01). Minor statistically significant differences (P < .05) were found between grades 1 and 2. Estimates of nuclear vv based on systematic sampling within the specimen showed high efficiency, with > 80% of the total observed variance contributing to biologic differences between individual specimens. Univariate prognostic study showed that clinical stage, and not histologic grade, was of prognostic value in the cases studied. Similarly, nuclear vv estimates were associated with disease recurrence and survival, with a cutoff point of 425 microns 3. CONCLUSION: Based on the cases investigated, shape-independent nuclear vv estimates may be an adjuvant tool in the grading and prognostic evaluation of infiltrating ductal breast carcinoma.

Breast Neoplasms↗
PubMed1996

Quantification of nuclear pleomorphism using an asymptotic fractal model.

OBJECTIVE: Nuclear pleomorphism (nuclear membrane irregularity) was investigated using transmission electron microscope (TEM) micrographs of 1,419 nuclei (32 oral carcinomas and normal cells from surgical margins). STUDY DESIGN: Nuclear profiles (1,400 x) were digitized (1 pixel = 35 nm) and fractal dimension estimated using the "yardstick" method. RESULTS: Log-log plots of yardstick length vs. perimeter showed a significant effect on length measurement typical of fractals at low resolutions (large yardsticks), but this effect disappeared at higher resolution (small yardsticks); that is compatible with Rigaut's asymptotic fractal model. Analysis of the asymptotic fractal parameters c, L and Bm showed that c was higher in normal nuclei, but log(L) and Bm were higher in malignant nuclei. A linear discriminant analysis using c, log(L) and Bm reclassified correctly 78.8% of the nuclei (normal 88.0%, tumor 70.2%). CONCLUSION: Asymptotic fractal analysis of nuclear profiles appears to show great potential for quantitative discrimination of oral cancer cell features.

Carcinoma, Squamous Cell↗
PubMed1997

Autowave tunneling through a non-excitable area of active media.

The mechanisms of autowaves propagation through local non-homogeneities in active media relevant to diverse class of physiological systems were studied by means of a computer simulation. The model proposed by Zel'dovich and Frank-Kamenetsky and that of FitzHugh-Nagumo were used for studying autowave tunneling, which in a broad sense implies underbarrier passing. It was shown that for every fixed parameter value corresponding to the degree of non-excitability of local area a critical value for non-excitable zone latitude exists. An autowave overcomes the barrier and continues to propagate when the value of zone latitude is less than critical. Critical conditions for origination of a source of periodical sequence of impulses in excitable medium were found. The source properties, as shown, can be modified by regulation of size of a non-excitable zone and a zone of higher excitability. In particular, the conditions when spatial irregularity behaves as a source of unidirectional and/or asynchronous sequence of impulses were explored.

Animals↗