A technique for measuring the in vivo average velocity of ultrasound in the human female breast was developed and applied to determine the range of such values in the breast of normal subjects in the approximate age ranges 20 to 80 years and in subjects with selected breast pathologies. Reasonable correlation of the velocity values with breast tissue type, as determined by x ray (mammography), was obtained, indicating that ultrasonic velocity data provide useful information on the main tissue constituents in the breast and that this technique should allow safe, long-term study of changes that may occur in the composition of such tissues.

New methods for the ultrasonic visualization of tissue, achieved by employing a newly developed versatile instrumentation system, are outlined and their application to the examination of brain is illustrated. The complete system, whose operating characteristics are described in detail, incorporates an on-line mediumsized digital computer, implementing omnidirectional scanning, utilizing three translational and two rotational degrees of freedom; relief display, which combines intensity modulation and deflection of the oscillograph beam by the echo signals; and segmental construction of echograms, which incorporates wide dynamic range combined with high resolution via program control of receiver gain as a function of range and echo strength. Omnidirectional scanning permits the more complete viewing of tissue interfaces than is possible with the usual compound-scanning methods. Relief display provides an additional parameter as compared to the common flat format for the presentation of echo information in a two-dimensional picture, and the type of echo signal composition at individual positions on an echogram thus can be represented The relief format also facilitates detection of significant echo signals against the background. Comprehensive presentation eliminates the need for, and problems associated with, time-variable gain in receiver amplification and also provides for much greater flexibility in the choice of an amplifier gain characteristic as a function of signal amplitude. The illustrative results presented demonstrate that new ultrasonic visualization methods can be used to detect and localize (1) internal structural features of the cranial vault, (2) external features of the brain (ventricular, cisternal, and fissural surfaces); and (3) major blood vessels (midsagittal sinuses) in considerable detail, under the condition that acoustic energy does not traverse bone.

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The characterization of the female breast by ultrasonic visualization techniques presents unique problems in comparison to visualization of other body areas. Basic to this uniqueness is the fact that, not only does the breast contain a variety of types of tissues, but the amount of each type of tissue is a variable. Correct identification, from the echogram presentation, of abnormalities located within any of these tissue structures is partly dependent on the ability to correctly identify normal echogram patterns over the full range of this variability; such identification necessitates precise correlation of the normal echogram pattern with the specific tissues and with their orientation in the path of the sound beam. However, this type of correlation is difficult to obtain in the in vivo breast. This paper discusses possible source of errors in such attempts. The basic data required to prevent such errors of interpretation of breast echograms can be obtained by carrying out a detailed acoustic visualization study of excised whole breast tissue, followed by correlation of the echogram patterns with the gross and histological sections of the breast tissue. Data obtained to date, using this approach for both normal excised breast tissue and excised tissue containing malignant abnormalities, will be presented.

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