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Biomedical subjects

P Meer

Publications and source records attributed to P Meer.

12 recordsLinked to original sources

Computer-assisted discrimination among malignant lymphomas and leukemia using immunophenotyping, intelligent image repositories, and telemicroscopy.

The process of discriminating among pathologies involving peripheral blood, bone marrow, and lymph node has traditionally begun with subjective morphological assessment of cellular materials viewed using light microscopy. The subtle visible differences exhibited by some malignant lymphomas and leukemia, however, give rise to a significant number of false negatives during microscopic evaluation by medical technologists. We have developed a distributed, clinical decision support prototype for distinguishing among hematologic malignancies. The system consists of two major components, a distributed telemicroscopy system and an intelligent image repository. The hybrid system enables individuals located at disparate clinical and research sites to engage in interactive consultation and to obtain computer-assisted decision support. Software, written in JAVA, allows primary users to control the specimen stage, objective lens, light levels, and focus of a robotic microscope remotely while a digital representation of the specimen is continuously broadcast to all session participants. Primary user status can be passed as a token. The system features shared graphical pointers, text messaging capability, and automated database management. Search engines for the database allow one to automatically identify and retrieve images, diagnoses, and correlated clinical data of cases from a "gold standard" database which exhibit spectral and spatial profiles which are most similar to a given query image. The system suggests the most likely diagnosis based on majority logic of the retrieved cases. The system was used to discriminate among three lymphoproliferative disorders and healthy cells. The system provided the correct classification in more than 83% of the cases studied. System performance was evaluated using rigorous statistical assessment and by comparison with human observers.

Decision Support Techniques↗

Robust retrieval of three-dimensional structures from image stacks.

Robust high-breakdown-point location estimators are employed to analyze image stacks under the piecewise constant image structure model. To reduce the effect of bias along the Z-axis, the class parameters are extracted using three consecutive slices, The segmentation algorithm first determines the most reliable seed regions, which are then used in a region-growing procedure supported by local evidence. The robustness and stability of the proposed technique is shown with both synthetic and real data, the latter consisting of one MRI and one confocal microscopy set. The performance of the algorithm is consistent with the ground truth obtained with manual segmentation by physicians.

Algorithms↗

The role of stimulus structure in spatial hyperacuity.

In spatial hyperacuity the subjects discriminate a stimulus feature relative to a reference, with an accuracy significantly better than the grain of the retinal mosaic. We show that the normalized thresholds have a dichotomous behavior; they are either insensitive to the spatial parameter in the experiment or increase very steeply with it. This behavior is explained by the involvement in the processing of pixel (receptor) accuracy information about the structure of the stimulus. A computational model employing optimal filtering reproduces the experimental data and suggests that processing of spatial hyperacuity tasks in the human visual system is optimal.

Computer Simulation↗

Importance of global information in vernier acuity.

Noisy vernier configurations were generated by normally distributing the lateral displacements of dot elements forming vertical dotted lines. Observations with noisy configurations were compared with thresholds obtained with noise-free lines. In configurations with gap, we have found, through independent perturbation of the end regions adjacent to the gap, that the entire length of the line was actively processed. In an experiment with noisy abutting lines, the threshold as a function of line length exhibited only a slight upward shift relative to the curve obtained with noise-free configurations. Since it is not possible to interpret all the results through a comparison of local positional information extracted from the stimulus configuration, we conclude that global information is also involved in the processing.

Discrimination, Psychological↗

Context dependent processing in spatial hyperacuity.

The importance of comparison processes in spatial hyperacuity tasks was investigated by means of a new relative nonalignment discrimination task. Vernier-type configuations nonaligned to either left or right, were presented in succession, and the subject had to decide which configuation exhibited a larger nonalignment. The relative nonalignment thresholds were found to be more strongly dependent on the spatial arrangement of the two lines than the thresholds corresponding to "ordinary" spatial hyperacuity performances. This context dependency is attributed to the active role played in the processing by comparison mechanisms.

Discrimination, Psychological↗