Surgery – Truss – Pad
Patent
1996-09-24
1998-09-15
Jaworski, Francis
Surgery
Truss
Pad
12866103, A61B 800
Patent
active
058065202
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method for in vivo evaluation and characterization of the mechanical or architectural properties of bone, employing the ultrasound technique.
BACKGROUND OF THE INVENTION
During the past few years, ultrasound equipment has appeared on the market which makes it possible to measure attenuation and its dependence as a function of frequency (attenuation coefficient), or the propagation velocity of ultrasound in transmission through the calcaneus or the patella. These devices are essentially intended for detecting or for monitoring osteoporosis.
A number of devices providing in vivo evaluation of bone by employing ultrasound beams are already known.
Publications WO 90/01903 and WO 87/07494 describe devices which make it possible to measure the propagation velocity of ultrasound in bone by using two transducers which are placed on either side of the bone.
U.S. Pat. No. 4,774,959 describes a device which measures the transmission attenuation coefficient using a first pair of transducers, this device including a second pair of transducers which measure the thickness of the bone where the ultrasound beam has passed through the bone.
European publications 0,341,969 and 0,480,554 describe devices which make it possible to measure the transmission attenuation coefficient and the velocity of ultrasound with the aid of a pair of transducers placed face to face.
Finally, U.S. Pat. No. 4,941,474 describes an apparatus which makes it possible to analyze both signals transmitted through the bone and signals which are reflected or scattered by the internal architecture of the bone. Said apparatus comprises at least one transducer emitting an ultrasound beam through the bone, means for receiving and memorizing the signals which are transmitted through the bone or reflected by its surfaces and means for treating the stored signals in order to measure the propagation velocity of the ultrasound beam in the bone, its thickness, the transmission attenuation coefficient of the ultrasound beam and the scattering parameters. This apparatus cannot provide parametric images.
Experience derived from the use of the known apparatus mentioned above shows that the measurements which can be carried out with them remain rudimentary, and that the accuracy, sensitivity and reproducibility of these measurements need to be improved. Furthermore none of these known devices can provide parametric images.
BRIEF DESCRIPTION OF THE INVENTION
Starting from this prior art the present invention relates to a process as disclosed in U.S. Pat. No. 4,941,474 but providing parametric images, said process being characterized in that the ultrasound beam is obtained by using focused transducers and said beam is scanned along one or several directions different from the ultrasound propagation direction notably along orthogonal axes.
According to the present invention, for producing, in transmission mode, parametric images of attenuation as a function of frequency and propagation of velocity of the ultrasound, use is made of a pair of focused transducers, placed opposite one another and operating at low frequency, that is to say at a central frequency of between 100 kHz and 3 Mhz, and preferably between 100 kHz and 1 Mhz.
In its application to producing reflectivity images in echographic mode (reflection mode), the method of the present invention uses a focused transducer or a pair of focused transducers, placed opposite and capable of operating in a wider frequency range, that is to say at a central frequency of between 100 kHz and 10 MHz.
According to the present invention, for producing reflectivity images in echographic mode and for estimating the attenuation and/or back-scatter coefficients as a function of the frequency of the ultrasound beam, and also with a view to producing, in transmission, parametric images of attenuation as a function of frequency and of propagation velocity, use is made of a pair of transducers, placed opposite one another and operating at low frequency, that is to say at
REFERENCES:
patent: 3847141 (1974-11-01), Hoop
patent: 4774959 (1988-10-01), Palmer et al.
patent: 5343863 (1994-09-01), Wiener et al.
patent: 5348009 (1994-09-01), Ohtomo et al.
Berger Genevieve
Laugier Pascal
Centre National de la Recherche Scientifique (C.N.R.S.)
Jaworski Francis
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