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Biomedical subjects

J Heiserman

Publications and source records attributed to J Heiserman.

6 recordsLinked to original sources
PubMed1991

Effect of measurement errors on sonographic evaluation of ventriculomegaly.

Ventriculomegaly is a sensitive indicator of maldevelopment of the fetal brain and spinal cord. The fetal ventricular atrium is an optimal portion of the lateral ventricular system to measure in order to judge ventriculomegaly. We tested the susceptibility of this measurement to inaccuracies created by errors in cursor placement or improper selection of the plane of section for measurement in 52 normal fetuses. This measurement was shown to be reasonably insensitive to errors in cursor placement along the axis of the ventricular system. However, choice of an off-axis image plane of section, an angled measurement, or improper choice of ventricular boundary leads to a relatively large number of false-positive test results (approximately 10%). None of the simulated errors in atrial measurements underestimates the size of the ventricle, and thus, they are unlikely to result in a diminution of test sensitivity.

Central Nervous System↗
PubMed1984

An improved stochastic approach to rf amplitude analysis in ultrasonic cardiac tissue characterization.

We carried out a series of studies to improve the reproducibility of methods for ultrasonic myocardial tissue characterization using a stochastic approach to amplitude analysis of radiofrequency signals previously reported from our laboratory. Analysis of transducer scanner characteristics, data acquisition and processing, and data display from studies in tissue phantoms permit us to define some features of a parameter for expression of tissue character. The ratio of mean to standard deviation of the amplitude histogram from our system is explored as now implemented in our laboratory for reproducible measurements. The theoretical basis for understanding the utility of this method in defining tissue architecture and pathologic conditions requires further work.

Animals↗
PubMed1980

Acoustic microscopy of human metaphase chromosomes.

Acoustic micrographs of human metaphase chromosomes have been recorded with wavelengths as short as 470 nm using liquid argon near 85 K as the acoustic wave coupling medium. Chromosomes prepared by trypsin-Giemsa staining exhibit acoustic banding patterns similar to the G-bands seen in optical images. Unstained chromosomes exhibit acoustic markings that do not correspond to traditional banding patterns. The observed acoustic contrast may arise from spatial variations in chromosomal mechanical properties, or from thickness variations in the fixed chromosomes.

Azure Stains↗
PubMed1979

Acoustic microscopy: resolution of subcellular detail.

Recent advances now permit the use of scanning acoustic microscopy for the analysis of subcellular components. By sequential viewing of identified fixed cells with acoustic, light, and electron microscopy, we have established that the acoustic microscope can readily detect such features as nuclei and nucleoli, mitochondria, and actin cables. Under optimal conditions, images can even be obtained of filopodia, slender projections of the cell surface that are approximately 0.1-0.2 micron in diameter. Small objects separated by as little as 0.5-0.7 micron can successfully be resolved. Three aspects of the acoustic micrographs prepared in this preliminary survey seem especially prominent. These are, first, the extraordinary level of acoustic contrast that can differentiate the various cytoplasmic organelles, even in regions of very thin cytoplasm; second, the reversals in acoustic contrast that occur when altering the plane of focus; and third, the sensitivity of the acoustic response to overall cytoplasmic thickness. The acoustic microscope uses a novel source of contrast that is based on local mechanical properties. In addition, it can provide a degree of resolution that is comparable to that of the light microscope.

Acoustics↗