An optimal spatial filtering electrode for brain computer interface.

There are millions of people in the U.S. and many more worldwide who could benefit from a noninvasive-based electroencephalography (EEG) brain computer interface (BCI). A BCI is an alternative or augmentative communication method for people with severe motor disabilities. However, EEG suffers from poor spatial resolution and signal-to-noise ratio (SNR). To improve the spatial resolution and SNR many researchers have turned to implantable electrodes. We have previously reported on significant improvements in BCI recognition rates using tripolar concentric ring electrodes compared to disc electrodes. We now report on a optimal method for combining the outputs from the independent elements of the tripolar concentric ring electrodes to improve the spatial resolution further. We used minimum variance distortionless look (MVDL), a beamformer, on simulated data to compare the spatial sensitivity of the optimal combination to disc electrodes and the tripolar concentric ring electrode surface Laplacian. The optimal combination shows the highest spatial sensitivity with the Laplacian a close second and disc electrodes resulting in a distant third. Further analysis is necessary with a more realistic computer model and then real signals. however it appears that the optimal combination may improve the spatial resolution of EEG further which in turn can be utilized to improve noninvasive EEG-based BCIs.

Injection sclerotherapy in the treatment of rectal prolapse in infants and children.

PURPOSE: The aim of this study was to examine the efficacy of injection sclerotherapy as treatment for persistent rectal prolapse. METHODS: The records of 28 patients with rectal prolapse treated with injection sclerotherapy over a 16-year period were reviewed. Initial management included assessment and correction of predisposing factors. If rectal prolapse persisted or if the prolapse required repeat emergency or operating room reduction, injection sclerotherapy was performed. The sclerosing agent included D50W in 21 patients (sole agent in 15, combined with ethanolamine oleate in four, and with phenol 5% in two). Phenol 5% alone was used in six patients, and 25% saline was used in one patient. Number of injections, recurrences, and complications were reviewed. RESULTS: Two patients were lost to follow-up, and one patient was cured once a polyp was recognized and removed. Of the remaining 25 patients, 21 were cured. Sixteen required one injection, three required two injections, and two required three injections (64% cure rate after one injection, 84% cure rate after three injections). There were 4 of 25 failures: two went on to low anterior resection after having failed two injections each; one patient was treated with Thiersch cerclage and injection after two failed injections; and one patient did not respond after three injections but had less severe prolapses. Of those injected with D50W alone, 13 of 14 were cured with injection sclerotherapy. Nine received one injection, two received two injections, and two received three injections (64% cure rate after one injection, 93% cure rate after three injections). The only complication was excessive oozing at the injection site in one patient. He was simply observed in hospital overnight. Follow-up averaged 33 months. The only significant underlying abnormality in our patient population was spina bifida in one patient. This patient was cured with injection therapy. Cystic fibrosis was ruled out by clinical examination and sweat chloride test in all patients. Constipation was the most common condition identified with the onset of rectal prolapse (15 of 28). CONCLUSIONS: Injection sclerotherapy is simple and should be considered as the first line treatment of recurrent rectal prolapse after failure of conservative measures. D50W is effective, easily available, inexpensive, and associated with few complications.

A retinitis pigmentosa register for western Australia.

This paper describes the main elements of the Western Australian retinitis pigmentosa register including details of the data stored on the register, aspects of the coding systems used and some description of the tests employed in diagnosis of retinitis pigmentosa. The register is family based and contains data on affected individuals and on their unaffected relatives. As at November 1991, the register contained data for 391 individuals from 207 separate families. Of the 391 individuals, 240 had definite or probable retinitis pigmentosa and 26 were possibly affected. The remainder were unaffected family members. In many cases, both affected and unaffected family members are being studied serially and the register is designed to store and easily retrieve serial data to allow study of disease progression for individuals and within families.

Fractional brownian motion: a maximum likelihood estimator and its application to image texture.

Fractals have been shown to be useful in characterizing texture in a variety of contexts. Use of this methodology normally involves measurement of a parameter H, which is directly related to fractal dimension. In this work the basic theory of fractional Brownian motion is extended to the discrete case. It is shown that the power spectral density of such a discrete process is only approximately proportional to |f|a instead of in direct proportion as in the continuous case. An asymptotic Cramer-Rao bound is derived for the variance of an estimate of H. Subsequently, a maximum likelihood estimator (MLE) is developed to estimate H. It is shown that the variance of this estimator nearly achieves the minimum bound. A generation algorithm for discrete fractional motion is presented and used to demonstrate the capabilities of the MLE when the discrete fractional Brownian process is contaminated with additive Gaussian noise. The results show that even at signal-to-noise ratios of 30 dB, significant errors in estimation of H can result when noise is present. The MLE is then applied to X-ray images of the human calcaneus to demonstrate how the line-to-line formulation can be applied to the two-dimensional case. These results indicate that it has strong potential for quantifying texture.