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Biomedical subjects

R Wendel

Publications and source records attributed to R Wendel.

6 recordsLinked to original sources
PubMed1998

Bilateral multifocal choroidal carcinoid: long-term follow-up without treatment.

PURPOSE: To report a minimally symptomatic patient with bilateral carcinoid tumors metastatic to the choroid who was followed up for 42 months without any treatment. METHOD: Case report. RESULTS: A 54-year-old white man with a history of bronchial carcinoid tumor had bilateral multiple carcinoid tumors metastatic to the choroid. Follow-up for 42 months without treatment demonstrated no growth of the choroidal tumors, and corrected visual acuity remained RE, 20/20 and LE, 20/25. Systemic status also remained stable. CONCLUSIONS: Carcinoid tumors metastatic to the choroid may remain stationary for an extended period. Treatment may be deferred until tumor growth, exudative retinal detachment, or substantial impairment of vision develops.

Bronchial Neoplasms↗
PubMed1996

Application of neural networks to quantitative nondestructive evaluation.

This paper concentrates on the quantitative analysis of reflection and transmission characteristics of structural waves in notched beams using neural networks. At one end of a rod a piezoelectric transducer excites a flexural guided wave, which propagates through the structure and is reflected from the notch as well as from the ends of the rod. At another point, a laser interferometer measures the resulting displacement versus time, which is recorded and serves as the digital fingerprint of the experiment. Our aim is to obtain quantitative information about the notch characteristics, i.e. its location and depth, on the basis of these digital recordings. This requires an inverse problem to be solved using neural networks. For the training of the network, synthetically produced wave patterns are used. The results of the corresponding wave experiment simulations compare well with experimental data. For fixed location, the calculated wave patterns could be quantitatively analysed to yield the depth of the notch if it is greater than a twentieth of the diameter. Another network could be trained for the localization with an accuracy of 2 cm for 93% of the training patterns. On the basis of these results a strategy is formulated on how neural networks could be trained to evaluate quantitatively both of the notch characteristics.

Algorithms↗
PubMed1994

Late re-opening of macular holes after initially successful treatment with vitreous surgery.

BACKGROUND: In more than 50% of eyes with idiopathic, full-thickness macular holes, vitrectomy results in clinical closure of the hole and improvement in visual acuity. Other than cataract formation, late complications of the procedure have not been reported. METHODS: Over a 4-year period, 167 eyes underwent successful vitreous surgery for idiopathic macular holes documented by clinical closure of the hole and an improvement in visual acuity of at least two Snellen lines. The authors retrospectively studied eight of these eyes. All initially had successful surgery; however, they subsequently had spontaneous late re-opening of the macular hole with acute diminution in vision. RESULTS: Late re-opening developed in these eyes between 2 and 22 months after initial surgery. The mean time for re-opening was 12.5 months. Three of eight eyes underwent a second vitrectomy, which was successful in improving visual acuity in two eyes. Another patient manifested the growth of an epiretinal membrane that apparently sealed the re-opened macular hole and improved vision. CONCLUSION: Late re-opening can complicate initially successful macular hole surgery and may occur in at least 4.8% (8 of 167) of initially successful operations. Re-opening has been documented as late as 22 months after initial surgery. Repeat vitrectomy with gas injection may result in reclosure of the hole and improvement in vision.

Aged↗