Echo Magnitude Research Articles

Principles and classification of soft tissues by grey scale echography.

Grey scale echography portrays the internal echoes originating from small impedance discontinuities formed by the structural organisation of soft tissue. These internal echoes are independent of inclination whilst their size and distribution is specific to the type of tissue examined. Thus normal and pathological tissues are portrayed with a differing appearance allowing their identification on the echograms. The principle of selecting a range of magnitudes of echoes for display on a restricted dynamic range of a display unit is described as well as methods used for compensating for the factors that effect the magnitude of echoes. Grey scale echography gives a new active role to simple scanning and a comparison of the features of simple and compound scanning is made. The simples and most reliable application of grey scale echography is the differentiation between cystic and solid structures and the criteria used in this application are discussed. The classification of soft tissue is more difficult, normal soft tissues being classified primarily by the appearance of the internal echoes, whilst the classification of localized pathological processes is based on the appearance of both the internal and the boundary echoes. The diagnosis of diffuse pathological conditions is the most difficult and is based on the change in the normal structural echo pattern.

Subjective quality of television pictures impaired by short-delay echo

Quality-grading tests have been made on the effect of an undistorted echo of positive or negative polarity and with delay in the range 200?1300 ns, in a 625-line monochrome television system. The results apply also to the effect on the luminance component of a colour signal. It was found simplest to express echo magnitude in terms of the magnitude of signal plus echo. A logistic relationship between mean picture-quality grading and logarithmic echo magnitude then applies, and the shape of the curve is independent of delay. A mathematical model is described to represent the complete relationships between picture quality, and echo delay and magnitude. Summarised results are given in terms of mark points of subjective impairment. The (signal + echo)/echo ratio at the 1-imp mark point, or midopinion condition, varies from 9 dB at 200 ns to 20 dB at 1300 ns for positive echo and 1 dB to 16 dB for negative echo. At the ?-imp mark point, the variation is from 14 dB to 25 dB for positive echo and 7 dB to 22 dB for negative echo.

DETECTING INTRACRANIAL PRESSURE WAVES WITH ULTRASOUND

Abstract Twenty-two patients who were undergoing continuous monitoring of intracranial pressure (I.C.P.) were subjected to one or more ultrasound recordings lasting 1-3 hours. The change in magnitude of the midline echo was compared with the wave-forms of the I.C.P. trace. In twelve patients I.C.P. waves were seen and distinctive patterns occurred simultaneously in the ultrasound tracing. These patterns were easy to reproduce and were never seen in the absence of I.C.P. waves. There was no difference in ultrasound tracings at normal I.C.P. compared with tracings at raised pressure in the absence of pressure waves.

Subjective quality of television pictures impaired by long-delayed echoes

Echoes are a well known form of impairment in television reception, but precise information on the subjective effect they cause has been scanty, and the limits for echo in specifications of television transmission systems have been set on a somewhat arbitrary basis. Using a previously proposed quality-grading method, tests have therefore been made of the effect of single undistorted echoes, having delays in the range 1–13μs, on still monochrome 625-line pictures typical of scenes in television broadcasting.The magnitude of echo corresponding to a given quality of picture decreases by about 5 dB as the delay is increased from 1 to 13μs. The effect of variation of delay over the range 5–13μs is less than 1dB; within this range, when echo-sensitive pictures are viewed under specified conditions, 50% favourable opinions are obtained with a signal/echo ratio of 23dB and 95% favourable opinions with a ratio of 28dB.

RADAR DETECTION OF THE SEA BREEZE

Abstract Radar and meteorological observations of four sea-breeze cases are presented. A clear-cut association between the echoes and the meteorological events is demonstrated. Where direct measurements are not available, the echo patterns are consistent with a rational physical picture of the sea breeze. Birds, insects, and other particulate matter are precluded by a combination of direct observation of the small pulse volume, by echo magnitude considerations, and by echo pattern. Scattering theory can account for the magnitude of the coherent layer echoes on the vertical beam, at the sea-breeze inversion with large but reasonable refractive-index gradients of 4 to 9 N units per cm or with vapor gradients of about 1 to 2 mb per cm. Incoherent echoes on the horizontal beam appear to come from vapor sheaths of large radius of curvature, with index gradients of similar magnitude, which are oriented parallel to the sea-breeze front. While this unusual result is supported by the streamer-form echo patterns an...

INTERPRETATION OF THE FLUCTUATING ECHO FROM RANDOMLY DISTRIBUTED SCATTERERS. II

The determination of the probability distribution for the magnitude of a radar echo from randomly distributed scatterers is a standard problem of the "random walk" type. We are concerned with the information to be gained about the scatterers from observation of the echoes, and the methods whereby this information may be extended. The method of averaging independent signals is investigated, and compared with the method of continuous averaging, which is found to be somewhat better. By appropriate variation of frequency of the radiation, it is found possible to obtain effectively independent determinations from a given region, and hence to derive more precise information about it. Finally, the continuous variation of signal with time is studied, and a simple picture of the development of the signal proposed. The Markoff method is used throughout.

On the Possibility of Obtaining Radar Echoes from the Sun and Planets

The sun is, after the moon, the simplest major astronomical body to reach by radar, and it is a more interesting object for study than the moon or the planets. In this paper, the process of reflection from the sun is investigated theoretically, together with the manner in which the echo intensity would be expected to depend on the various parameters of a radar system. It is shown that the detection of sun echoes appears technically possible, but a radio-engineering project of considerable magnitude is involved. Orders of magnitude of planetary echoes are also briefly discussed, and a reference is made to several astronomical studies which could be carried out with a very high-power radar.