WE-G-211-03: Development of Ultrasound Imaging Equipment.

UNLABELLED

One of the earliest man-made ultrasound images of the human body was produced by Dussik in 1941, when he attempted to image the brain using a through transmission technique. These early images were later judged to be artifacts related to sound wave transmission through skull bone. Pulse-echo examination of the body started in the late 1940's following developments of sonar, radar, and ultrasound flaw detectors. Ludwig and colleagues measured speeds of sound in tissues, publishing the value 1540 m/s for many tissue paths, a figure still used today. Among the pioneering pulse- echo imaging teams in the USA were Wild and Reid who developed real time imaging of the breast in the early 1950's, and Howry and Bliss, who were able to generate detailed anatomical pictures of the neck by employing water bath scanners. Many other groups, including from Japan, Australia, and Europe were pursuing both A-scope and B-scope applications of ultrasound around this time. Notable achievements include work by Ian Donald in the UK, who in 1955 described a contact scanner and published B-scope images depicting a variety of anatomical regions. The systems of Donald and of Wild are said to have inspired engineers from Howry's water bath team in Colorado to develop their own contact scanner, and in 1963 a new company, Physionics produced the first commercial, single element transducer "articulated arm" scanner. It provided bi-stable B-mode images on a storage oscilloscope, marking the beginning of widespread acceptance of this modality. Gradual instrument improvements include analog then digital scan converters for gray scale in the 70's, and both auxiliary and stand alone mechanical scanning real time probes. Phased array technology also emerged for cardiac imaging, as did linear arrays for obstetrics and abdominal imaging. Perhaps the most revolutionary instrument ever was produced in the early 1980's, the Acuson 128, introducing high image quality linear and phased array beamformed images for radiology applications and helping to conclude the brief era of manual scanners. As beamformers became digital devices in the 1990's, unprecedented image quality, diagnostic features, two dimensional arrays, and even system miniaturization evolved, bringing ultrasound imaging to its present state. The ultrasound field is still characterized by novel instruments emerging from the laboratories of clever scientists, addressing diagnostic and therapeutic needs not provided by present day technology.

LEARNING OBJECTIVES

1. Describe features of the first commercially available ultrasound scanners. 2. Identify the relationship between technological developments in radar and emergence of ultrasound as a modality 3. Explain the significance of a high large channel count in beamforming 4. Contrast echo acquisition and processing in a modern scanner with first generation devices.