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Biomedical subjects

L Landini

Publications and source records attributed to L Landini.

At least 55 records · Page 3Linked to original sources
PubMed1986

Evaluation of frequency dependence of backscatter coefficient in normal and atherosclerotic aortic walls.

For five groups of aortic specimens (normals and with different degrees of atherosclerosis) the ultrasonic backscatter coefficient was measured as a function of frequency in the range 4-15 MHz. The results of the study are related to two classes of structure, connective and fatty tissue (whose relative amount in the arterial wall is related to the different stages of atherosclerosis), as the main determinants of the scattering from aorta. The structure of connective tissue in the aorta produces a power law frequency dependence of the backscatter coefficient typical of small scale structures (Ka much less than 1). Fatty tissue introduces a frequency dependence of the backscatter coefficient typical of structures of intermediate scale (Ka approximately equal to 1). Biochemical composition and structure of normal and atherosclerotic aorta therefore, specifically affect the employed acoustical parameter.

Aorta↗
PubMed1986

The use of frequency histograms of ultrasonic backscatter amplitudes for detection of atherosclerosis in vitro.

This study was designed to determine whether a quantitative analysis of integrated backscatter amplitude distribution is potentially useful in characterizing the atherosclerotic lesion. One hundred measurements (10 X 10 array) were made in fresh aortic regions (2 cm X 2 cm) of nine normal and 19 atherosclerotic arterial walls. A 10 MHz transducer was used. The integrated backscatter distinguished normal from atherosclerotic specimens (-56.7 +/- 4.3 vs -42.5 +/- 8.9 dB, p less than .01). The shape of the integrated backscatter amplitude distribution was analyzed by calculation of skewness and kurtosis of each arterial region. Both skewness values (0.134 +/- 0.325 vs -0.193 +/- 0.491 in normal and atherosclerotic segments, respectively, p = NS) and kurtosis values (0.055 +/- 0.765 vs -0.610 +/- 0.379, p less than .01) discriminated between the two groups. When only the six atherosclerotic specimens with mostly fatty and fibrofatty sites were considered, skewness and kurtosis still distinguished normal from atherosclerotic regions (0.134 +/- 0.325 vs -0.404 +/- 0.232, p less than .05 and 0.055 +/- 0.765 vs -0.558 +/- 0.337, p less than .05, respectively), while integrated backscatter values did not (-56.7 +/- 4.5 vs -52.3 +/- 6.1 dB, p = NS). In conclusion, atherosclerosis may be detected in vitro by the quantitative analysis of integrated backscatter distribution. This variable could also be of help in the identification of less obvious forms of atherosclerotic disease that are not distinguishable on the basis of integrated backscatter amplitude.

Aorta↗
PubMed1986

Atherosclerosis detection by ultrasounds. A comparative histologic study on aortic specimens.

The aim of the study was to establish whether ultrasonic tissue characterization may be an useful tool in atherosclerosis detection. Ultrasonic measurements were performed on fresh aortic specimens taken from autopsy. Four hundred aortic regions were studied in vitro and histologically classified in four groups of 100 samples each: normal walls, fibrous, fibro-fatty and calcified plaques. Two different indices were measured, one derived from the Fourier transform of the echo produced by a specular reflector placed behind the specimen under study and named integrated attenuation index (IAI); the other derived from the Fourier transform of the echo reflected from the specimen under study and named integrated backscatter index (IBI). Results obtained from ultrasonic and histologic analyses showed that both attenuation and backscatter indices increase in atherosclerotic specimens where a deposition of biochemical components such as collagen and calcium salts takes place. This is not true for fatty tissue that reduces the echogenicity of the atherosclerotic profile of the arterial wall.

Aorta↗
PubMed1986

Comparative ultrasonic-histologic study in breast lesions detection.

The aim of this study is to establish whether a comparative morphologic-ultrasonic analysis is able to identify acoustical parameters for mammary lesions characterization. Breast specimens from radical mastectomy have been selected by frozen sections and then analyzed by nonconventional techniques based on ultrasonic attenuation measurements. After histologic examination of the fixed specimens, both ultrasonic and morphologic appearances have been compared. Our results suggest that the slope index is able to differentiate breast lesions on the basis of the amount of cells and collagen fibers they contain. The slope increases with increasing collagen fibers content while necrosis reduces the overall attenuation of the specimen. On the basis of the above results, it appears possible to differentiate both malignant breast tumors characterized by productive fibrosis and breast dysplasia. Malignant breast tumors without productive fibrosis cannot be distinguished from benign tumors.

Breast↗
PubMed1985

Ultrasonic energy-based technique for characterizing atherosclerosis.

For the characterization of atherosclerotic disease in human aortic specimens two indices of ultrasonic signal loss have been developed. They are based on an energy evaluation of broadband pulsed ultrasound and have been introduced in order to minimize phase cancellation artifacts caused by phase sensitive transducers. Both indices are derived from the transfer function H(f) of the specimen, they are: the slope of ln H(f) for the evaluation of signal loss due to absorption and scattering inside the specimen thickness, and s ln H(f) df, which reflects changes in both the internal and the intimal surface properties of the aorta. The results indicate that methods based on the evaluation of signal loss inside the aortic thickness are insensitive to surface irregularities and to the angle of the incident ultrasound. The complete progression of atherosclerosis may be followed by indices reflecting changes in both the thickness and the surface acoustic properties of the specimen.

Aorta↗
PubMed1985

On-line evaluation of ultrasonic integrated backscatter.

Although it is already known that reflected ultrasonic signals (backscatter) are changed by the structure of the tissue through which they pass, clinicians are still awaiting a practical instrument in which information from backscatter reflections will serve as a diagnostic aid additional to that provided by conventional ultrasonic scans. The equipment described here is both small and fast, and is integrated into a normal ultrasound installation. No new operating procedures have to be learned. The integrated backscatter is calculated on-line and presented on an LED as tissue characterization parameters. In order to minimize noise due to physical movement of the heart during an investigation of the myocardium, the analysis is synchronized with the ECG; and as an aid to the user, the normal system VDU displays both the ECG and the activating trigger pulse derived from the R-wave peak. An A-scan display has been used but this could readily be adapted for B-scan operation and single line analysis. Tests with backscattering models and standard instrumentation have shown no significant difference between results using time domain or frequency domain analysis.

Biomedical Engineering↗
PubMed1985

Angle dependence of ultrasonic backscatter in arterial tissues: a study in vitro.

The object of this study was to obtain quantitative data on the angle dependence of reflected ultrasound signals in freshly excised normal human arterial walls and those with different degrees of atherosclerotic involvement (fatty, fibrofatty, fibrous, or calcified). Fifteen specimens were evaluated in each pathologic subset. The backscatter coefficient (BS, expressed as cm-1 X steradians -1), measured at the single frequency of 10 MHz, was evaluated at a normal angle of incidence of the interrogating beam to the tissue sample and over an angular span of 60 degrees (+/- 30 degrees around normal incidence, 2 degree steps). BS measured at normal incidence separated normal (10(-2) X 0.155 +/- 0.018; mean +/- SE) from fibrofatty (10(-1) X 0.0103 +/- 0.008), fibrous (10(-1) X 0.182 +/- 0.016), and calcified (0.202 +/- 0.016) specimens; normal and fatty (10(-3) X 0.759 +/- 0.142) and fibrofatty and fibrous samples could not be distinguished from each other in a statistically significant way. Angular scattering measurements identified two patterns: A "directive" pattern, characterized by a strongly angle-dependent BS that falls abruptly when the beam is moved slightly away from normal incidence. This pattern was typical of calcified, fibrous, and less markedly, fibrofatty and normal samples. A "nondirective" pattern, characterized by a BS that is not significantly angle dependent and fluctuates throughout the entire angular range. This was typical of fatty samples.

Aorta↗
PubMed1985

Fibrosis, lipids, and calcium in human atherosclerotic plaque. In vitro differentiation from normal aortic walls by ultrasonic attenuation.

This study was designed to determine whether attenuation of ultrasound by the aortic wall is potentially useful in characterizing the atherosclerotic lesion. Measurements were made on fresh specimens taken from a human aorta at autopsy. Four hundred different sites, 4 mm in diameter each, corresponding to the dimension of the ultrasonic beam at the focal zone, were ultrasonically analyzed and histologically studied. Attenuation of ultrasound in each site was assessed by Fourier analysis of the echo produced by a specular reflector placed behind the specimen. Two parameters were measured over the range 7-11 MHz: the integrated attenuation index (per cm), and slope (per cm per MHz) of the best fit straight line relating attenuation and frequency. Histological examination--performed for each of the 400 sites where attenuation had been measured--identified four subsets (100 samples each): normal aortic walls, fibrous plaques, fibrofatty plaques, and calcified plaques. Results obtained from ultrasonic and histological analyses showed that the integrated attenuation index was lowest in normal walls (24 +/- 2.1, mean +/- SE) and progressively increased in fibrous (32 +/- 3.1), fibrofatty (82 +/- 6.5), and calcific (185 +/- 8.7) subsets (all intergroup differences were significant, except for the normal vs. fibrous comparison). The slope value was significantly lower in the fibrous than in the normal subsets: (10(-3)) 31.9 +/- 4.5 vs. (10(-3)) 99.5 +/- 9.1, respectively. Values of fibrofatty and calcific plaques overlapped: (10(-3)) 383 +/- 21 vs. (10(-3)) 320 +/- 23, respectively. Both were significantly different from normal and fibrous groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Aorta↗
PubMed1983

Different degrees of atherosclerosis detected by backscattered ultrasound: an in vitro study on fixed human aortic walls.

The aim of the study was to establish whether ultrasonic backscattered signals may characterize the atherosclerotic process, providing a quantitative assessment of severity. Measurements on aortic specimens were made in vitro by a transducer acting as transmitter and receiver. Two different indices were measured, one based on peak amplitude value (Vmax) and the other on fast Fourier transform (FFT) analysis of ultrasonic reflected signal (IBI). Two hundred fixed aortic wall specimens (50 normal, 50 fatty streaks, 50 fibrofatty, and 50 calcific) were first characterized ultrasonically and then pathologically, both macroscopically (before ultrasonic study) and histologically (after it). Differentiation of normal, fibrofatty and calcific specimens was achieved using Vmax. Values obtained in fatty streaks overlapped with normal wall but significantly differed from values of fibrofatty and calcific subsets. The results with IBI were similar except that the difference between normal and fibrofatty specimens was not statistically significant. Such changes in acoustic behavior of atherosclerotic walls could be due to increased deposition of highly echogenic biological materials, such as collagen, cholesterol crystals (in fibrofatty specimens), and calcium salts (in calcific ones). Therefore, backscattered signals appear to provide in vitro simple parameters indicative of changes in the arterial wall structure due to the atherosclerotic process.

Aorta↗
PubMedDate not supplied

In vivo radiofrequency ultrasound analysis of normal human heart structures.

Twenty young subjects were studied with a microprocessor system for quantitative analysis of backscattered radiofrequency (RF) signals from normal heart structures. This system allows an "on line" quantitative evaluation of the amplitude of the RF "native" signal, before the chain of processing and display, with the acquisition gate displayed on a conventional M-mode machine. Septum, posterior wall, and anterior mitral leaflet were analyzed. The gate length was kept at 3 microseconds (2.35 mm) for the ventricular walls (excluding endo- and epicardial reflections), and at 1 microsecond (0.8 mm) for the mitral valve. Integrated backscatter index (IBI) was calculated as the time integral of [u(t)[, where u(t) = i(t) X s(t); is the time sequence of backscattered echoes and s(t) is the time gate delimiting the thickness of the insonated tissue. The IBI was expressed in percent, normalized for the pericardial interface (the strongest reflection was assumed to be 100%). The percent IBI for the septum was found to be 22 +/- 4%; for the posterior wall it was 17 +/- 3%; for the anterior mitral leaflet it was 5 +/- 2%. A second reading of the same structures was performed by the previous observer and by a new one. Good intraobserver (r = 0.92) and interobserver (r = 0.88) correlations were obtained. In conclusion, a regional variation in echo amplitude from different heart structures can be observed in man. This set of values can be used as normal values for future studies in pathologic conditions.

Adult↗
PubMedDate not supplied

Frequency-dependent attenuation in breast tissue characterization.

The aim of this study is to establish whether an index derived from the slope of the frequency-dependent ultrasonic attenuation can provide quantitative information on normal and pathological breast tissue. Ultrasonic measurements were performed by using pulsed transmitted ultrasound in the frequency range 2-8 MHz. Thirty-three specimens were selected for their probable pathologic classification, by macroscopic observation, before ultrasonic study, and subsequently histologically classified. Ultrasonic results suggest the possibility that the examined specimens fall into four groups: (1) fat, fibroadenoma, giant fibroadenoma, infiltrating ductal carcinoma, medullary carcinoma; (2) infiltrating lobular carcinoma, tubular carcinoma, scirrhous carcinoma; (3) fibrosis; (4) fibrofatty tissue, fibrocystic disease. Correlative morphological studies indicate that the employed index can classify breast tissues on the basis of their cellular and fibrous composition and the inhomogeneity of their structure.

Adenocarcinoma↗
PubMedDate not supplied

Non-linear prediction for oesophageal voice analysis.

Herein, non-linear prediction methods are applied to oesophageal voice analysis. The research aims to investigate normal and pathological subjects, in order to improve knowledge of the oesophageal voice behaviour. Analysis is performed in the reconstructed phase space, using both non-linear prediction with local linear approximation and the S-Map method. Preliminary results seem to confirm that in normal subjects a non-linear stable deterministic behaviour takes place, while in pathological subjects the non-linear contribution reduces while the time series becomes unstable.

Adult↗