Mean Echo Intensity Research Articles

Pennation Angle Does Not Influence the Age-Related Differences in Echo Intensity of the Medial Gastrocnemius

The reflection of an ultrasound (US) wave is strongest when the propagation direction of the wave is perpendicular to muscle fascicles. Thus, it is possible that muscle echo intensity (EI), a gray-scale US measure of muscle quality, may be influenced by the angulation of muscle fascicles. Therefore, the purpose of this study was to determine if age-related differences in muscle EI values are influenced by differences in pennation angle (PA). Medial gastrocnemius EI and PA were examined using panoramic US imaging in 24 young (19.8 ± 1.7 y) and 21 older (69.3 ± 3.3 y) men. The young men had lower EI values (young = 74.1 ± 6.3 a.u., older = 89.1 ± 8.8 a.u.) and a greater PA (young = 20.0 ± 2.9°; older = 17.2 ± 2.5°) compared with the older men (p < 0.01). In addition, there was a negative relationship (r = –0.473, p < 0.01) between PA and EI with both groups combined, but no significant relationship when the young (r = –0.334, p = 0.111) and older (r = –0.147, p = 0.525) men were examined separately. An analysis of covariance revealed that muscle EI values remained different (p < 0.01) between age groups after adjustment for differences in PA. Thus, after statistically adjusting the mean EI values for the differences in PA, there were still significant age-related differences in EI. These findings may provide further support that the age-related changes in muscle EI values reflect changes in tissue composition (i.e., increase in intramuscular fat and/or connective tissue) commonly reported in older adults.

Quantification of Skeletal Muscle Fibrosis at Different Healing Stages Using Sonography

This study attempted to quantify the degree of muscle fibrosis on sonograms of injured gastrocnemius muscles at different healing stages in a rat model. Correlations between the quantifications and histologic assessments of the injured muscles were also determined. Sonograms and histologic findings of gastrocnemius muscle fibrosis were obtained during the second, third, and fourth weeks after surgically induced lesions in the right gastrocnemius muscles of 15 Wistar rats. The echo intensity, reflecting the degree of brightness on a sonogram, was divided into 256 gray levels instead of decibels. The mean echo intensity of each pixel in the region of interest was calculated as a summation of the echo intensities in all pixels divided by the pixel numbers in the region. To control individual variations among the rats, we calculated a K value, defined as the difference in the mean echo intensity between normal and affected muscles. Significant correlations (r > 0.7; P < .05) between mean echo intensity and K values and the fibrous tissue percentage were identified. The mean echo intensity in the injured gastrocnemius muscles was significantly (P = .029) greater than that in the normal muscles 3 weeks after injury. In histologic assessments, muscle fibrosis was most prominent 3 weeks after injury. However, the differences in fibrosis at different healing stages were not significant. Mean echo intensity and K values can reflect the extent of fibrosis in affected muscles and may be valuable for quantifying muscle fibrosis in clinical practice.

Quantitative gray‐scale analysis in skeletal muscle ultrasound: A comparison study of two ultrasound devices

Muscle ultrasound is a useful technique to detect neuromuscular disorders. Quantification of muscle echo intensity (EI) using gray-scale analysis is more reliable and more sensitive compared with visual evaluation of the images. We devised a method to reliably use EI normal values established with one ultrasound device for use with another device. Based on measurements in a dedicated phantom and in 7 healthy subjects, a conversion equation was calculated to convert the mean EI. The reliability of this equation was next evaluated in a follow-up study of 22 healthy children. Mean muscle EI could be reliably converted from one ultrasound device to another. This allows for normal values obtained with one device to be used with other devices, which is an important step forward toward the use of quantitative muscle ultrasound in daily clinical care.

Evaluation of colon cancer vascularity by flash echo imaging

Objective. Tumor vascularity is strongly related to the prognoses of patients with various malignant primary tumors, including colorectal cancer. The aim of this study was to confirm the usefulness of harmonic flash echo imaging (H-FEI) for the preoperative evaluation of tumor vascularity in colorectal cancer by comparison with CD34 staining of resected specimens. Material andmethods. Seventeen patients undergoing surgical resection for advanced colorectal cancer (9 M, 8 F) were enrolled in this study. An ultrasound system transmitting ultrasound pulses at 2.3 MHz and receiving them at 4.6 MHz (second harmonic) was used for H-FEI. After intravenous injection of ultrasonic contrast medium (SHU 508A), intermittent harmonic scanning was carried out for 120 s at intervals of 4 s. On the tumor image of the strongest enhancement in each patient, 5 regions of interest were taken to decide the mean echo intensity of the tumor. Immunohistochemistry using antibodies against CD34 was carried out on resected specimens. The mean microvessel density was decided by counting microvessels on 5 fields (×400) of CD34-stained specimens. Results. The mean value of H-FEI intensity was 5.44±1.10, and the mean microvessel count with CD34 staining was 35.0±7.95. A significant positive linear correlation was observed between the intensity of H-FEI determined preoperatively and the microvessel count in CD34-stained specimens (r=0.741, p=0.0006). Conclusion. Vascularity of colon cancer can be evaluated non-invasively using H-FEI.

Predicting the need for surgery in Crohn's disease with contrast harmonic ultrasound

Objective. Harmonic flash echo imaging (H-FEI), an intermittent scanning method using injection of Levovist, enables the evaluation of microperfusion of the gastrointestinal wall. The aim of this study was prospectively to investigate the relationship between bowel blood flow and the likelihood of the need for surgery in 70 patients with active Crohn's disease (CD), using conventional ultrasonography (US) and H-FEI. Material and methods. For H-FEI, Levovist injection was followed by scanning of the bowel segment of interest with intermittent harmonic imaging for 2 min (interval, 4 s; transmission pulse at 2.3 MHz; reception at 4.6 MHz). We calculated the mean echo-intensity for the bowel wall showing strongest opacity in the FEI series for each patient. Maximum bowel-wall thickness, wall stratification, maximum echo-intensity obtained by H-FEI, CD activity index, and C-reactive protein concentration were compared between patients treated successfully with medication after H-FEI (group M) and those who proved to need surgery (group S). Results. No significant differences in clinical variables were evident between groups M (n=45) and S (n=25). The subsequent need for surgery was significantly indicated by multivariate analysis, showing loss of stratification in the bowel wall (odds ratio (OR)=5.98, 95% confidence interval (CI)=1.4–25.1, p=0.015) and high echo-intensity according to H-FEI (OR=1.02, CI=1.005–1.034, p =0.007). Conclusion. In active CD, patients with bowel segments showing a loss of stratification and rich perfusion by H-FEI are likely to need surgical treatment.

Attenuation estimations using envelope echo data: Analysis and simulations

Previously we described a video signal analysis (VSA) method for measuring backscatter and attenuation from B-Mode image data. VSA computes depth-dependent ratios of the mean echo intensity from a sample to the mean echo intensity from a reference phantom imaged using identical scanner settings. The slope of a line-fit of this ratio (expressed in dB) versus depth is related to the attenuation of the sample. This paper investigates conditions for which the echo intensity ratio versus depth is independent of transducer pulsing characteristics and instrument settings, and depends only on the properties of the sample and the reference. A theoretical model is described for the echo signal power versus depth from a uniform medium containing scatterers. The model incorporates bandwidth, frequency and media attenuation. Results show that the sample-to-reference echo intensity ratio versus depth is a curve, the departure of which from a straight line is a function of the relative attenuation of the two media, the imaging system bandwidth and the initial frequency. The model also leads to a depth-dependent “effective frequency” determination in the VSA method. Model predictions are verified using RF signals computed by an acoustic pulse-echo simulation program. (E-mail: jazagzeb@wisc.edu)

A New Technique for Endobronchial Ultrasonography and Comparison of Two Ultrasonic Probes: Analysis With a Plot Profile of the Image Analysis Software NIH Image

Endobronchial ultrasonography (EBUS) is currently the sole clinical method available for delineating the bronchial wall structure; however, the image resolution is inadequate. Thus, an improved image analysis system is needed for both a more accurate and more readily interpretable endobronchial ultrasonogram. A total of 10 patients underwent pulmonary resection for lung cancer. EBUS was performed on the bronchi of the resected lungs, which had been immersed in physiologic saline solution. The same bronchial lesion in each specimen was imaged with two probes: 20 MHz and 30 MHz. The images were analyzed using the plot profile derived from freeware image analysis software: NIH Image (National Institutes of Health; Bethesda, MD). The measured echo intensity of the bronchial wall was statistically analyzed. A normal bronchial wall image consists of five layers, and the plot profile shows a W-shaped curve. The mean value of the echo intensity of each peak or trough of the W-shaped curve was calculated and compared for both probes. The differences in the mean echo intensity between both the third and fourth layer and the second and fourth layer were found to be significantly greater with the 30-MHz probe than with the 20-MHz probe. The echo intensity curve of a central-type lung cancer was not W shaped, indicating that the bronchial wall was not composed of the normal five layers. We employed image analysis software and drew a plot to obtain a W-shaped curve from the EBUS image data. This enabled us to make an objective assessment of the laminar structure of the bronchial wall. In order to clearly recognize the laminar structure of the bronchial wall, the 30-MHz probe was found to be more useful than the 20-MHz probe.

Quantitative ultrasonography of skeletal muscles in children: normal values.

The purpose of this study was to establish normal values of muscle thickness, ratio of muscle thickness to subcutaneous fat thickness, and muscle echo intensity in children between 11 weeks and 16 years of age. Transverse scans of four muscles were made by standardized real-time ultrasound examination. The scans were digitized, and mean echo intensity was measured using gray-scale analysis. A multiple regression equation was used to study which independent parameter (age, height, weight, or sex) influenced the variables for each muscle. Muscle thickness depended on the child's weight. The other parameters did not significantly influence muscle thickness after correction for weight. The ratio of muscle thickness to subcutaneous fat thickness depended on age. Echo intensity showed no correlation with either of the variables. As a result, all normal values, including the equation to calculate them, are described. These normal data may help to determine the diagnostic value of muscle ultrasound in children with suspected neuromuscular disease.

Preoperative Assessment of Gastric Cancer Vascularity by Flash Echo Imaging

Background: Tumor vascularity as indicated by immunohistochemical staining is a significant prognostic factor in gastric and other cancers. Non-invasive preoperative assessment of the vascularity of gastric cancers has not been possible. We aim to determine the reliability of harmonic flash echo imaging (FEI) for assessment of vascularity of gastric cancers by comparison with CD34 staining of resected specimens. Methods: Twelve patients undergoing surgical resection of advanced gastric cancer were studied. An ultrasound system transmitting ultrasound pulses at 2.3 MHz and receiving them at 4.6 MHz (second harmonic image) was used for harmonic FEI. Approximately 30 s after intravenous injection of ultrasonic contrast medium (SHU 508A, Levovist), second harmonics (4.6 MHz) emitted from microbubbles were obtained to enhance the B-mode images. Using the tumor image showing strongest enhancement in each FEI series, regions of interest were determined to measure mean echo intensity in the tumor. Immunohistochemistry using antibodies against CD34 was carried out in resected specimens. Tumor vascularity was determined by counting stained microvessels. Results: A significant positive correlation was noted between sonographic amplitude determined preoperatively by FEI analysis and number of CD34-stained microvessels in tumor specimens ( r = 0.869, P = 0.004). Conclusion: Vascularity of gastric cancers now can be evaluated non-invasively by harmonic FEI.

Evaluation of cardiac tissue from two-dimensional echocardiogram: analysis of gray level and its distribution.

Two-dimensional echocardiograms of parasternal long-axis view were recorded and the mean echo intensity and its distribution in the interventricular septum were examined for the purpose of inferring myocardial tissue. Six healthy subjects (N), 29 with left ventricular hypertrophy (LVH), and 12 with old anteroseptal myocardial infarctions (MI) were used in the study. Settings for gain control were adjusted in the constant manner. Data were recorded on a Video tape recorder, with analog data converted to digital signals, subjected to a low-pass filtering, and then analyzed by a Computer tomography image processor. The region of interest was set within the interventricular septum, and a mean relative echo intensity and its histogram (number of pixels showing different echo intensity) was evaluated. The histogram patterns were examined and the parameter for skewness, which shows asymmetrical characteristics, and the parameter for kurtosis, which shows degree of peakedness of distribution, were calculated. Relative echo intensity was found to increase in the order MI greater than LVH greater than N. Histograms showed the majority of pixels were concentrated at the low echo intensity level in the normal group, while pixels were distributed in a relatively gentle slope around the mean value in the LVH group. Many pixels were in the high intensity levels in the MI group, although the rest were dispersed throughout various intensities including low level. The differences are thought to be related to the extent and density of fibrosis. Analysis of two-dimensional echocardiographic echo intensity and distribution may be useful in characterizing myocardial tissues.

A Weather Radar Video Integrator and Processor

This paper describes the design and operation of a new weather radar intensity contouring device. This device accepts raw video information and averages these data in range and azimuth to obtain improved estimates of the mean echo intensity. The averaged video signal is then level sensed and encoded to produce a radar display with seven categories of precipitation intensity.