Correlation between Contrast Sensitivity and Modulation Transfer Functions.

Significance: Previous studies found no correlation between visual acuity and optical quality in a population of young subjects with good vision. Using sinusoidal gratings, we systematically investigate the correlation between contrast sensitivity and optical quality as a function of spatial frequency.

Purpose: This study describes the correlation between the contrast sensitivity function (CSF) and the modulation transfer function (MTF) in a sample of young and informed subjects.

[Decubitus ulcers ... again and always].

This article is the result of a comparative study during 1994 and 95 concerning escar prevalence in our Nephrology intensive care unit. Combined paramedical and medical activities concerning preventive and curative care, structured assessment (..

Measurements of an index of echogenicity in some thyroid diseases.

In the preceding article, the measurement of an index of echogenicity has been described. In this article, we present the mean value and standard deviation of this index in normal thyroid and pathological cases. It appears that the index is very significantly lowered in Hashimoto's disease compared to its value in normal thyroids and simple goiters.

Simple device for determining an index of echogenicity.

The technique reported here uses a simple electronic system adaptable to a standard manual echograph with the aim of obtaining a numerical index of echogenicity. The index is the ratio of the average echo amplitude within a gated portion of tissue at a given depth to the average echo amplitude within the same gated portion measured under the same conditions on a phantom filled with a "tissue-mimicking" material. A theoretical analysis shows that the index depends not only on the attenuation coefficient and the backscattering coefficient of the tissue but also on the depth of the measurement.