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D L Ewert

Publications and source records attributed to D L Ewert.

74 records · Page 5Linked to original sources

Improvement in specificity of ultrasonography for diagnosis of breast tumors by means of artificial intelligence.

A set of ultrasonograms of lesions from 200 patients between the ages of 14 and 93 years who underwent mammography followed by ultrasonographic examination and excisional biopsy has been studied with computer vision techniques to improve the ultrasonographic specificity of the diagnosis. Selected features representing the texture of the lesion were calculated and then classified by an artificial neural network. This network was biased toward correctly classifying all the malignant cases at the expense of some misclassification of the benign cases. The network diagnosed the malignant cases with 100% sensitivity and 40% specificity (compared with 0% specificity for the radiologists diagnosing the same set of cases in the breast imaging setting), and tests performed with a leave-one-out technique indicate that the network will generalize well to new cases. This suggests that methods based on neural network classification of texture features show promise for potentially decreasing the number of unnecessary biopsies by a significant amount in patients with sonographically identifiable lesions.

Adolescent↗

An electronic circuit simulating T-type calcium-channel current from the sinoatrial node.

A circuit that simulates T-type calcium-channel current characteristics of the sinoatrial (SA) node was developed from discrete electronic components and tested at physiologic membrane voltage ranges. The circuit design was based on the T-type calcium-channel current dynamics obtained from a mathematical model of the SA node membrane, which, in turn, is based on physiologic data. The design was held at a resting membrane potential and then stepped to new voltages over the entire operating range of the T-type calcium channel. The circuit was validated by comparing its transient response current with the predicted current from the mathematical model. In addition, the peak currents of the circuit were compared with plots of peak current obtained from the mathematical model and physiologic data. By showing that the electronic circuit mimics the T-type calcium-channel current dynamics found within the SA node, the results may provide a foundation for developing a novel cardiac pacemaker that is based on the ion-channel characteristics of excitable tissue.

Action Potentials↗