Transmission acoustic microscopy of tissue sections (1 GHz)
SummaryThe acoustic microstructure of mouse small intestine has been studied with a transmission acoustic microscope working at 1 GHz and the influence of the histologic processing on the microacoustic pattern has been tested. Unstained thin sections provide pictures rich in details and highly contrasted. Gelatin has been used as hydrosoluble embedding medium and has been compared to paraffin. The former embedding procedure retained the viscoelastic properties of the specimen far more and provided the most detailed pictures. Osmiun tetroxide has been used to demonstrate acoustic staining.
Local histogram information content of ultrasound B-mode echographic texture.
In the diagnostic ultrasound community, the echographic B-scan texture is an important area of investigation since it can be analyzed to characterize the histologic state of internal tissues. In the present paper, a minicomputer based system was used to digitize B-mode images and to develop a method to measure their textural information. This method is based on the concept of local information content of spatial image proposed by Lowitz (1983, 1984). It first measures the local gray-level histogram in a small square window centered on each picture element (pixel) of a digitized B-mode image. The information derived from the local histograms is then used to characterize the tissues, to partition the B-mode image into homogeneous zones of texture, to estimate to what extent a tissue is different from another, to delimit the contours of a tissue and to measure its surface. The method is illustrated on the thyroid gland but it can be applied to the study of other organs.
The relative effects of system parameters on texture in gray-scale ultrasonograms.
Texture in B-mode ultrasonography of the abdomen can, in many cases, serve as an important diagnostic tool. Unfortunately, because texture as it is now presented depends on many parameters which are independent of pathology, it is not always a reliable sign. Parameters such as transducer size, center frequency, and bandwidth; B-mode display and storage methods; near and far field wave effects; and the type of intervening tissue all influence the display of texture. We have investigated these parameters of texture through the analysis of computer simulated B-mode ultrasonograms based on in vitro A-line data collected under a variety of circumstances and conditions. A freshly excised bovine pancreas served as the target tissue. Computer generated textured B-mode images, produced with different gray-scale and scan converter storage algorithms, were evaluated by a panel of six radiologists who individually divided sixty images into groups of images with similar texture. These evaluations were mapped into a six feature hyperspace with each axis representing a particular parameter. By applying a variation of the principal components transformation, each parameter could be ranked according to its effect on texture. We found that the type of gray-level preprocessing map had the most effect on texture; intervening tissue and transducer variations had intermediate effects. So long as the target distance did not exceed the focal length of the transducer, the distance between the transducer and the target tissues had the least effect on texture.