Development of low entropy coding in a recurrent network.

In this paper we present an unsupervised neural network which exhibits competition between units via inhibitory feedback. The operation is such as to minimize reconstruction error, both for individual patterns, and over the entire training set. A key difference from networks which perform principal components analysis, or one of its variants, is the ability to converge to non-orthogonal weight values. We discuss the network's operation in relation to the twin goals of maximizing information transfer and minimizing code entropy, and show how the assignment of prior probabilities to network outputs can help to reduce entropy. We present results from two binary coding problems, and from experiments with image coding.

The value of endorectal ultrasonography in the follow-up of intracavitary radiation treated early rectal cancer.

In selected patients with early rectal cancer, intracavitary radiation is a successful treatment. Endorectal ultrasound has proved an accurate method for staging and selecting such cancers for treatment. The value of endorectal ultrasound in the follow-up of patients with intracavitary radiation has not been previously assessed. Between 1989 and 1991, 30 patients treated at the Hamilton Regional Cancer Centre with intracavitary radiation were assessed by endorectal ultrasound. The mean age was 65 +/- 12 years with a range of 37-78 years. There were 17 males and 13 females. All patients were treated with curative intent. The dose of radiation administered was 8963 +/- 1506 cGy over 3.5 +/- 0.7 fractions. No patient received supplemental iridium implantation. Thirty-seven endorectal ultrasounds were carried out in 30 of the intracavitary radiation treated patients. Clinical findings (digital, sigmoidoscopic, and histology) were compared with the radiologist's interpretation of the endorectal ultrasounds. Using a 2 x 2 table accepting the clinical findings as the 'Gold Standard', the sensitivity of endorectal ultrasound was 71%, the specificity 61%, the positive predictive value 53%, the negative predictive value 78% with an overall accuracy of 75%. We conclude that endorectal ultrasound in the routine follow-up of patients treated with intracavitary radiotherapy for carcinoma of the rectum is questionable.

Hyperbaric oxygen therapy in chronic stable multiple sclerosis: double-blind study.

We carried out a randomized, double-blind, placebo-controlled trial of hyperbaric oxygen therapy (HBO) in patients with chronic stable MS. Eighty-two patients were treated in a multiplace hyperbaric chamber with gas supplied by mask. Forty-one patients received 20 consecutive daily treatments of 100% O2 followed by 7 "booster" treatments in the next 6 months; 41 control patients received "air" (12.5% O2 at 1.75 atmospheres absolute). There was no significant difference in treatment and control groups in the Extended Kurtzke Disability scores, Kurtzke Functional scores, magnetic resonance imaging, or evoked potentials after the initial 20 treatments or after the boosters. HBO is not effective in treating chronic stable MS.

Medical screening of sports divers.

Sports divers encounter heavy physical exertion in a cold, stressful environment. They must also pass rapidly through large, ambient pressure changes. These stresses demand that the diver be emotionally and physically fit, and able to perform maneuvers to equalize internal and external pressures. Medical screening of sports diving candidates requires that the examiner has a knowledge of diving and the stresses encountered by the sports diver.