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At least 595 records · Page 33Linked to original sources
PubMed2004

Transmission latencies in a telemetry-linked brain-machine interface.

To be clinically viable, a brain-machine interface (BMI) requires transcutaneous telemetry. Spike-based compression algorithms can be used to reduce the amount of telemetered data, but this type of system is subject to queuing-based transmission delays. This paper examines the relationships between the ratio of output to average input bandwidth of an implanted device and transmission latency and required queue depth. The examination was performed with a computer model designed to simulate the telemetry link. The input to the model was presorted spike data taken from a macaque monkey performing a motor task. The model shows that when the output bandwidth/average input bandwidth is in unity, significant transmission latencies occur. For a 32-neuron system, transmitting 50 bytes of data per spike and with an average neuron firing rate of 8.93 spikes/s, the average maximum delay was approximately 3.2 s. It is not until the output bandwidth is four times the average input bandwidth that average maximum delays are reduced to less than 10 ms. A comparison of neuron firing rate and resulting latencies shows that high latencies result from neuron bursting. These results will impact the design of transcutaneous telemetry in a BMI.

Action Potentials↗
PubMed2005

The nearest subclass classifier: a compromise between the nearest mean and nearest neighbor classifier.

We present the Nearest Subclass Classifier (NSC), which is a classification algorithm that unifies the flexibility of the nearest neighbor classifier with the robustness of the nearest mean classifier. The algorithm is based on the Maximum Variance Cluster algorithm and, as such, it belongs to the class of prototype-based classifiers. The variance constraint parameter of the cluster algorithm serves to regularize the classifier, that is, to prevent overfitting. With a low variance constraint value, the classifier turns into the nearest neighbor classifier and, with a high variance parameter, it becomes the nearest mean classifier with the respective properties. In other words, the number of prototypes ranges from the whole training set to only one per class. In the experiments, we compared the NSC with regard to its performance and data set compression ratio to several other prototype-based methods. On several data sets, the NSC performed similarly to the k-nearest neighbor classifier, which is a well-established classifier in many domains. Also concerning storage requirements and classification speed, the NSC has favorable properties, so it gives a good compromise between classification performance and efficiency.

Algorithms↗
PubMed1986

Compression of nucleic acid and protein sequence data.

This paper describes the application of text compression methods to machine-readable files of nucleic acid and protein sequence data. Two main methods are used to reduce the storage requirements of such files, these being n-gram coding and run-length coding. A Pascal program combining both of these techniques resulted in a compression figure of 74.6% for the GenBank data-base and a program that used only n-gram coding gave a compression figure of 42.8% for the Protein Identification Resource database.

Algorithms↗
PubMed2007

Prior data for non-normal priors.

Data augmentation priors facilitate contextual evaluation of prior distributions and the generation of Bayesian outputs from frequentist software. Previous papers have presented approximate Bayesian methods using 2x2 tables of 'prior data' to represent lognormal relative-risk priors in stratified and regression analyses. The present paper describes extensions that use the tables to represent generalized-F prior distributions for relative risks, which subsume lognormal priors as a limiting case. The method provides a means to increase tail-weight or skew the prior distribution for the log relative risk away from normality, while retaining the simple 2x2 table form of the prior data. When prior normality is preferred, it also provides a more accurate lognormal relative-risk prior in for the 2x2 table format. For more compact representation in regression analyses, the prior data can be compressed into a single data record. The method is illustrated with historical data from a study of electronic foetal monitoring and neonatal death.

Bayes Theorem↗
PubMedDate not supplied

Vector quantization as a method for integer EMG signal compression.

Vector quantization (VQ) is a well-known lossy compression method, which has not often been applied to biosignals. In this paper, VQ and its mean residual variant for encoding and decoding electromyography (EMG) signals have been tested. The methods are selected in such a way that they can be later applied in a low-resource embedded system. A neural network approach is used for codebook generation. The preservation of medical parameters is a prominent sign of quality in medical compression systems. Both signal level fidelity factors and preserving medical parameters are tested. The results show that mean residual vector quantization with short segments is a workable approach for EMG signal compression.

Algorithms↗
PubMedDate not supplied

Effect of the Harrington compression system on the correction of the rib hump in spinal instrumentation for idiopathic scoliosis.

To analyze the effect of the Harrington compression system on the rib hump in thoracic idiopathic scoliosis, intraoperative measurements were made on 21 cases during correction with the distraction system and after addition of the compression system. The data show that the compression system makes a major contribution to the correction of total rib deformity in over two-thirds of the patients, and the correction of the rib valley is much more significant than correction of the rib hump. Analysis of postoperative spine roentgenograms seems to indicate that the extent of the rib correction does not correlate with spine derotation as measured by the system of Nash and Moe. The improvement in rib correction achieved by addition of the compression system appears to result from changes centered about the costovertebral joints.

Adolescent↗
PubMed2002

Mechanism of destructive pathologic changes in the spinal cord under chronic mechanical compression.

STUDY DESIGN: A histologic and histochemical study was performed both in the autopsy of a human patient with cervical spinal cord compression caused by ossification of the posterior longitudinal ligament and in a tiptoe-walking Yoshimura mouse model of progressive cervical cord compression. OBJECTIVES: To clarify the mechanism of destructive pathologic changes in the spinal cord under chronic mechanical compression. SUMMARY OF BACKGROUND DATA: Under chronic compression, the spinal cord exhibits destructive changes considered to be causes of profound and irreversible motor paresis. Recently, some investigators have found that apoptosis in acute spinal cord injury induces both secondary degeneration at the site of injury and chronic demyelination of tracts away from the site of injury. However, the mechanism responsible for these destructive spinal cord changes under chronic compression remains unclear. METHODS: The spinal cord was examined histologically, and an attempt was made to detect apoptotic cells using terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling in both the autopsy of a human patient and tiptoe-walking mice exhibiting spinal cord compression. RESULTS: Apoptotic cells were observed in the chronically compressed spinal cord in both the autopsy of a human patient and model mice. In tiptoe-walking mice exhibiting spinal cord compression, descending degeneration in the anterior and lateral columns and ascending degeneration in the posterior column were observed. The distribution of oligodendrocytes with positive results from terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling was similar to that for degeneration of the long tracts. CONCLUSIONS: Spinal cord cell apoptosis may produce destructive changes in the spinal cord under chronic compression, with a resulting irreversible neurologic deficit.

Aged↗
PubMed2004

Elastographic imaging of thermal lesions in liver in-vivo using diaphragmatic stimuli.

Radiofrequency or microwave ablations are interstitial focal ablative therapies that can be used in a percutaneous fashion for treating tumors in the liver, kidney, and prostate. These modalities provide in situ destruction of tumors. We present a method for in-vivo elastographic visualization of the ablated regions in the liver during and after thermal therapy. In-vivo elastographic imaging uses compressions of the liver due to movement of the diaphragm during the respiratory cycle. Elastography of the liver and other abdominal organs has not been attempted previously due to the difficulty in providing controlled compressions. Gating of the data acquisition to the respiratory waveform would provide access to data where the compression increments are similar in both magnitude and direction, thereby enabling reproducible imaging of the thermal lesion or tumor. Comparison of elastograms with gross-pathology of ablated tissue illustrates the correspondence between elastographic image features and pathology. Ultrasound is routinely used to guide the rf ablation procedure, so the same imaging system could be used for elastographic imaging. Since the technique utilizes physiological motion of the diaphragm due to respiration, it may also be employed in the visualization of cancerous tumors in the liver.

Animals↗
PubMed2006

Digital image compression should be limited in diabetic retinopathy screening.

Digital colour retinal photography is a useful modality for diabetic retinopathy screening. Unlike film photography, the size of the image depends on the resolution of the acquired image. With the availability of high-resolution digital cameras, larger images requiring greater storage-memory will inevitably be generated. Image compression may then be necessary so that these images can be viewed conveniently, archived and transmitted across computer networks. Unfortunately with the paucity of clinical studies on retinal image compression, more research is necessary to develop evaluation tools to identify optimum image compression ratios for diabetic retinopathy screening.

Data Compression↗