Surgery – Truss – Pad
Patent
1995-12-08
1997-12-16
Lateef, Marvin M.
Surgery
Truss
Pad
12866007, A61B 800
Patent
active
056973721
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates generally to ultrasound scanning.
Images produced by transmission of ultrasonic pulses through tissue, and generated from reflected echoes can be directly displayed in real time. Ultrasonic scanning constitutes a valuable non-invasive diagnostic tool for gaining information concerning the interior structure of a body. In medical applications, where the "body" may be a living human or animal body, inhomogeneity of the tissue causes different degrees of attenuation and backscatter of the ultrasonic signal which result in a medically unsatisfactory displayed image.
Known ultrasonic scanners typically have a transducer (which may in practice comprise a plurality of individual transducer elements in a linear or annular array), operated to transmit and receive ultrasonic pulse signals. Ultrasonic pulses transmitted from an individual transducer element into the body, reflected at points therein and received by the same transducer element provide information on the interior structure of the body in a line extending into the body from the transducer element. Such a one-dimensional line of information is referred to as an A-scan. A two-dimensional image, referred to as a B-scan can be generated by scanning a transducer generating successive A-scan lines. Such scanning may be achieved by physical displacement of an individual transducer (that is a transducer comprising a single transducer element) or by electronic scanning in the case of a transducer comprising an array of individual transducer elements. A B-scan image therefore represents a section through the body passing through the line defined by the transducer (if it comprises an array of transducer elements) or by the path traversed by an individual transducer, which, upon display on for example a video monitor screen, can be used to visualise the interior structure of the body.
In order to normalize the display, and to take account of the fact that in a homogeneous body the echo signals from points deeper into the body will be more strongly attenuated due to the greater path length which they have travelled, it is normal to subject the received signals to an amplification with a time-dependent gain. The gain function of such known instruments, which effectively varies the gain as a function of depth, is based on average material properties. In a real life situation, however, where there are localized regions (such as cartilage or amniotic fluid) which may have greater or lesser attenuation than the assumed average, the time-dependent gain variation function is incorrect. Thus, although some compensation may be obtained by progressively increasing the receiver gain for signals from greater ranges it must be accepted that no simple compensation function may accommodate the possible variations in tissue structure and that the normal practice of applying the same gain function repeatedly is a compromise which, while it offers a degree of improvement over the uncorrected signal, is still far from perfect.
Although known scanners are provided with means for tuning or varying the gain function slightly in order to optimize the image, in other words to take account of the physical features within the actual body being examined, even when they are adjusted to obtain the best results the image includes image artifacts in the form of shadows, namely areas which are darker, in relation to the surrounding image, than the general level of the image, and "enhancements" or "inverse shadows", which are areas of greater brightness than the correct brightness for that area. It is observed that the "shadows" appear behind physical features which attenuate the energy in the transmitted ultrasonic pulse more strongly, such as cartilage tissue, whereas the "enhancements" appear behind (that is more deeply within the body in the direction of the section from the surface) physical features which attenuate the energy less strongly, such as cysts or amniotic fluid.
It will be appreciated that the image presented to the operato
REFERENCES:
patent: 4608868 (1986-09-01), Green
patent: 4788981 (1988-12-01), Nagasaki et al.
patent: 5361767 (1994-11-01), Yukov
Fields Derrick
Lateef Marvin M.
Systems Engineering & Assessment Limited
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