Joie Pierce Jones

Ultrasonic tissue characterization: A Review

Present medical ultrasound systems are based on envelope detection methods and therefore display only echo intensity information. However, phase information is also recorded by the transducer which is a pressure‐sensitive device, but is not utilized in commercial display or measurement schemes. This additional information may be of diagnostic significance since the interaction between sound and tissue acoustical properties can be correlated with specific pathological states. Thus, in principle, in vivo techniques could be devised which would extract and separate the medically significant features of the ultrasound interactions with tissue and would display ultrasonic tissue signatures appropriate for a differential diagnosis. The development of such quantitative techniques for the measurement of ultrasonic tissue parameters and/or the display of ultrasonic tissue signatures has become known as ultrasonic tissue characterization. In this paper we review the physical basis for ultrasonic tissue characteriza...

A New Broad‐Band Ultrasonic Technique with Biomedical Implications. II. Preliminary Experiments Involving Human Skull Bone

A broad‐band acoustic pulse, produced by a spark source operating in water, was used to illuminate several test objects. The reflected signal was analyzed using a deconvolution procedure and the specific acoustic impedance obtained as a function of time. In one particular experiment, a series of modest impedance differences were accurately resolved behind a section of human skull bone.

In Vitro Visualization of Liver Metastases Using Ultrasonic Impediography

A new technique suitable for medical diagnoses and nondestructive testing was recently introduced by the author [J. Acoust. Soc. Am. 52, 178–179(A) (1972); 53, 343(A) (1973)]. Termed impediography, this method employs time‐domain deconvolution of appropriately shaped acoustic impulses and their echoes to produce a temporal waveform that can be related to physical parameters such as impedance. Thus, proper analysis of reflected pulses yields the specific acoustic impedance as a function of acoustic travel time. This acoustic “picture” is termed an impedogram. In this paper several impedograms of a human liver, obtained at postmortem, are presented. A number of metastatic deposits were identified by impediography and confirmed by autopsy. Standard diagnostic procedures failed to find the lesions located by impediography.

Further Experiments with Impediography: A New Ultrasonic Technique with Biomedical Implications

A new technique suitable for medical diagnoses and nondestructive testing was recently introduced [Papers NN7 and NN8, 83rd Meeting, Acoust. Soc. Amer.]. Termed impediography, this method employs time‐domain deconvolution of appropriately shaped acoustic impulses and their echoes to produce a temporal waveform that can be related to physical parameters such as impedance. Thus, impediography allows us to measure accurately the specific acoustic impedance at an arbitrary position within a test object. In preliminary experiments using a spark source to illuminate the test object, analysis of the reflected signal gave the impedance as a function of the acoustic travel time. This acoustic “picture” is termed an impedogram. In this paper, two particular experiments will be discussed in detail. In the first, impedograms of a soft rubber test object were obtained under various degrees of tension. Changes in impedance were clearly observed as the sample was stretched. I n a second experiment, a two‐dimensional imp...

A New Broad‐Band Ultrasonic Technique with Biomedical Implications. I. Background and Theoretical Discussion

Ultrasonic techniques presently used for medical diagnosis make use of narrow‐band or single‐frequency pulse‐echo devices. Recent studies at BBN indicate that a new broad‐band technique should significantly improve present diagnostic capabilities. This new technique makes use of acoustic impulses, which are short in time but broad in frequency content, and a time domain deconvolution procedure. The result is a temporal waveform which can be related to physical parameters such as specific acoustic impedance and frequency‐dependent attenuation. Thus, the new technique allows us to measure quantitatively to a high degree of accuracy the specific acoustic impedance at an arbitrary position within a test object.

A short history of acoustical microscopy

Optical microscopy has a long and interesting history, going back thousands of years to discoveries made in both Assyrian and Mayan cultures. Acoustical microscopy, on the other hand, has had a much shorter but equally interesting history, going back only to the mid‐20th century. This presentation traces the development of acoustical microscopy from its very beginnings to the present. Comparisons with other microscopic techniques will point out the unique features offered by acoustical microscopy. A wide range of application areas will be reviewed and future prospects and potentials discussed.

Clinical applications of acoustical microscopy

Very high frequency ultrasonic imaging offers an important tool for biomedical research as well as for clinical practice. Using ultrasound systems operating between 20 and 200 MHz, morphological and functional images of the skin may be obtained. For example, ultrasound may be used to assess wound healing, determine the extent of skin tumors, measure skin thickness, and visualize skin vascularization. At higher frequencies (600 to 1000 MHz), ultrasonic imaging can be used for histological studies with far greater sensitivity than optical microscopy and with a spatial resolution equivalent to optical methods. For example, ultrasound may be used to evaluate biopsy specimens more quickly and more accurately than optical microscopy. Here we report our experiences with very high frequency ultrasound as a clinical tool and, using this technology, the development of new standards by which tissue changes and disease processes may be defined.

Noncontact ultrasonic imaging for the evaluation of thermal injury

Although conventional wisdom suggests that ultrasonic imaging of the body cannot be accomplished without direct contact (or at least via water coupling), we have shown that noncontact imaging through air is possible, certainly for superficial body regions, provided judicious choices of piezoelectric materials and matching layers are made. In preliminary experiments and clinical studies reported here, noncontact imaging is demonstrated for the evaluation of thermal injury (including the quantitative measurement of burn‐depth), for the assessment of wound healing, and for the examination of assorted skin lesions. Specifically, in the case of thermal injury, reflections from the dermal/fat interface in human skin is clearly seen using a noncontact 5‐MHz transducer. Such measurements are sufficient to determine burn‐depth which, in turn, are sufficient to provide, for the first time, a quantitative and noninvasive method for burn evaluation and treatment specification. Evaluating over 500 burn sites in some 100 patients, noncontact ultrasound showed a much greater accuracy and sensitivity than standard clinical assessment. Our method is applicable to a conventional clinical environment as well as a battlefield situation and should prove particularly effective for large‐scale medical triage.

Medical ultrasonic imaging: Present status and future prospects

For over 30 years, ultrasonic imaging, based on the same pulse‐echo principles as radar and sonar, has played an important role in diagnostic medicine. In many ways ultrasound is an ideal diagnostic tool—noninvasive, nontraumatic, capable of producing real‐time images, and as all available data indicate, apparently safe at the acoustical intensities and duty cycles encountered in existing diagnostic equipment. Here the objective is to provide a snapshot of the present state of medical ultrasound and to assess the future prospects of this technology from ongoing research activities. Innovations such as Doppler analysis and cross‐correlation techniques to measure flow, phased array transducers, contrast agents, tissue characterization, and, in particular, quantitative imaging methods based on unique reconstruction techniques will, it is believed, greatly increase the clinical utility of ultrasound as well as maintain a continued high rate of growth in the marketplace.

Transmission into a Basin Having a Bigradient Sound‐Speed Profile

A basin is idealized as a flat‐bottom region of deeper water surrounded by a gentle, constant‐slope transition to a flat‐bottom region of shallower water (“shelf”). The speed profile is taken to have a constant negative gradient above a fixed axis depth and a constant positive gradient below, both independent of horizontal position. Analytical estimates for averaged sound transmission loss between a point in the basin and a point at variable range have been formulated from ray theory with lossy specular reflection from the surface and bottom. The approach is an adaptation to the bigradient case of earlier work [P. W. Smith, Jr., J. Acoust. Soc. Amer. 49, 96(A) (1971)]. The loss estimate can be very sensitive to frequency, the depth of the point in the basin, and range, as the variable point moves up the slope and over the shelf. A physical interpretation of this behavior, the dominant parameters, and comparisons with data are discussed. [Study supported by Office of Naval Research.]