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This paper deals with the estimation of the slope of attenuation in human breast tissue. The measurement is done in the reflection mode with a short time Fourier analysis. All important factors such as diffraction effect, tissue depth and specular reflectors are taken into account. A population of 49 normal women shows large inter-individual variations of the attenuation coefficient. A multiple linear regression allows correlation of this variation with the duration of the woman's genital life and pregnancies. A preliminary study is done on 10 benign diffuse breast diseases and shows a weak correlation with the type of the breast: normal or pathological. The utility of the quantification is discussed for one case of large fibrocystic disease.

After reviewing the usual models proposed for the echographic response of soft tissues, we discuss the interaction between the ultrasonic wave and large size obstacles. Structures of this size, specular reflectors, can be found in tissues. The influence of such reflectors on in vivo attenuation measurements is detailed. We point out the importance of the specular echo noise originating from two kinds of reflectors: plane-like and vessel-like reflectors. We present a complete study of their influence on two different algorithms for attenuation estimates: the spectral centroid shift and the narrow band methods. Results are presented on stimulated data, a tissue-mimicking phantom and in vivo muscle data. Different procedures for minimizing the specular echo noise are also discussed.

Duchenne muscular dystrophy (DMD) is a disease inherited in an X-linked recessive manner. Nothing is yet known about the gene defect involved. The problem of DMD carrier detection is very important and now without satisfactory solution. Presently the best method, for this detection, is the determination of the serum creatine-kinase (CK) level. However about 30% of DMD children's mothers have normal CK levels. In this study we associated CK determination and a new echographic method. This physical investigation is based on the muscle attenuation measurements through the evolution of the running spectral moments. The parameter expressed is the slope of the ultrasound attenuation signal (in decibels by centimetre and by megahertz; dB . cm-1 . MHz-1). We measured this parameter in vivo on the vastus medialis. The use of the chemical technique and of the physical one improves largely the detection of obligate carriers of Duchenne muscular dystrophy than when one of these methods is employed alone. One such combination recognizes 17 out of the 19 obligate carriers in our series. The difference of the results obtained by these two unrelated methods cannot be yet interpreted, but can reflect genetic heterogeneity in DMD and the inactivation of the X chromosomes.

This paper deals with the measurement of the attenuation of ultrasound in muscle and its application to the detection of Duchenne Muscular Dystrophy (DMD) carriers. The precision obtained when measuring the attenuation is an important parameter to be considered. A statistical approach is taken on simulated data and compared to in vivo results. The results allow discussion for the minimum tissue volume needed for the estimation. Variations in muscle attenuation between normals were obtained from studies on 27 volunteers. These attenuation values were compared to those obtained from 19 carriers of DMD. Attenuation appears to be a potential clinical indicator of DMD carriers.

Diffraction effects are a cause of error when estimating the frequency dependent attenuation of ultrasound in biological tissues in the reflection mode. Comparison of attenuation values estimated in vivo by different investigators using different types of transducers makes calibration and correction for diffraction necessary. In this paper, we present experimental results for in vivo calibration and correction for the diffraction effect for focused transducers. We also study numerically the diffraction filter in a time-frequency representation, and show that for a focused probe, there is a region in the time-frequency domain where the frequency slope of the diffraction filter does not vary with time. The main consequence for in vivo estimation is that for a given probe, it is possible to select both the distance between the region of interest and the probe, and the frequency limits, such that the attenuation thus estimated is unbiased by the diffraction effect. This result, obtained by numerical calculations, is confirmed by experimental calibration of a foam phantom and in vivo muscle.

So far, to account for ultrasonic attenuation in soft tissues molecular scale relaxation theory is retained. In addition to these mechanisms, the authors have obtained experimental evidence proving the role also plaid by cellular scale resonance mechanisms. Moreover, in addition to incoherent diffusion, it has been found that some tissues exhibit some coherent diffusion. All these experimental findings allows us to establish the feasability of non invasive ultrasonic biopsies.

Methods for "in vivo" tissue attenuation measurements, including a new method based on Short Time Fourier Analysis and discussion of their application to the clinical field.

The method discussed aims to characterize the ultrasonic absorption of liver tissues between 3 and 8.75 MHz by the slope of its linear variation with frequency. A transmission measuring device has been used and a data processing system has directly calculated this slope, which is reduced when the strength of intercellular links are lessened by mild treatment with trypsin, although the cells are left intact. This was performed on three batches of Wistar rats and the effect is explained mainly by reduction of the amplitude of relaxation processes dissipating energy in the cells.

The erythrocytes sedimentation can be monitored by an ultrasonic echographic method which is described. It is shown that this technique can give some information on the hematocrit profile in the sedimentation tube.