This invention relates to ultrasonic imaging method and apparatus and in particular to pulsed real-time B-scan, pulsed Doppler, and a combination pulsed B-scan and pulsed Doppler imaging and motion detecting means for use in the simultaneous display of a B-scan image and blood-flow profile.
The capacity of ultrasonics to differentiate tissues on the basis of their ability to propagate ultrasound, the lack of toxic effects at energy levels required for diagnostic use, and the fact that there is no requirement for invasive techniques with their attendant disadvantages and dangers make ultrasonic visualization a particularly effective and an attractive diagnostic tool. A variety of ultrasonic techniques have been demonstrated, including Doppler and B-scan methods.
The well known pulsed B-scan method employs a narrow beam transducer to project a short ultrasonic pulse into the tissue and to detect the reflected pulses. With B-scan, a two dimensional image is produced by moving the transducer past the area of interest and recording and/or displaying the reflected pulse train at closely spaced intervals. The well known pulsed Doppler method also employs a narrow beam transducer to project a short ultrasonic pulse into moving tissue or particles, such as blood cells, and to detect the frequency of the reflected signal, which frequency is related to the movement or flow of the tissue or particles. By sequentially sampling the reflected Doppler signal a velocity profile along the line of propagation of the transmitted pulse may be obtained. A combined B-scan and Doppler profile display greatly enhances the detection and visualization of the structure under investigation.
A discussion of various ultrasonic techniques, including the well known B-scan method, is found in the INTERNATIONAL JOURNAL OF NONDESTRUCTIVE TESTING, Vol. 1 (1969), pp 1-27, "Methods of Acoustic Visualization", Philip S. Green, one of the present inventors. Ultrasonic pulsed Doppler velocity detection means also are well known as disclosed, for example, in U.S. Pat. No. 3,777,740 by David E. Hokanson, issued Dec. 11, 1973, and in the article entitled, `Pulsed Ultrasonic Doppler Blood-flow Sensing` by Donald W. Baker in IEEE TRANSACTIONS ON SONICS AND ULTRASONICS, vol. SU-17, No. 3, July 1970. Additionally, a system for manually switching between B-mode and Doppler displays is contained in an article in IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING, vol. BME-21, No. 2, March 1974 entitled `Ultrasonic Duplex Echo -- Doppler Scanner` by Frank E. Barber et al. Similarly a combined B-scan and Doppler display is suggested in a report entitled `Development of High Resolution Ultrasonic Imaging Techniques for Detection and Clinical Assessment of Cardiovascular Disease` dated 9/5/74 by Titus C. Evans, Philip S. Green and James F. Greenleaf, Report No. NO1-HT-4-2904-1 available from National Technical Information Service, 5285 Port Royal Road, Springfield, Virginia, 22151.
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