Quantitative sonographic feature analysis of clinical infant hypoxia: a pilot study.

PURPOSE: To determine whether textural features derived from sonographic pixel intensities differ significantly between healthy infants and infants who have had acute clinical hypoxic episodes. METHODS: Neurosonographic and calibration phantom-processed image data were evaluated prospectively from 9 infants (age range, 1 to 163 days) with at least 1 episode of hypoxia and compared with image data from a control population of 16 healthy infants (age range, 1 to 191 days). Custom software was used to make 45 textural feature measurements on 40 x 40-pixel regions of interest within brain parenchyma in the distribution of each major cerebral artery, the thalami, and the cerebellum and in a tissue-mimicking calibration phantom. Means comparison testing was followed by logistic regression to assess statistical variation between the patients and the control group. RESULTS: Nine of 45 textural features showed statistically significant differences between mean values comparing the two groups. Mean gray level was the most sensitive predictor of differences between the two populations (mean gray level for healthy subjects was 46.8; mean gray level for patients was 56.3). An average of mean gray values in areas supplied by the posterior cerebral arteries and the cerebellum was even more sensitive for differentiating healthy subjects from patients. CONCLUSIONS: Quantitative sonographic textural feature analysis showed differences between the brains of healthy infants and those of infants with clinical hypoxia.

US tissue characterization workstation: applications and design.

This article discusses the purpose, design, and uses of an ultrasonographic tissue characterization workstation. The distinguishing characteristic of a tissue characterization workstation is its ability to analyze and classify image textures. Texture is defined as regularly or randomly repeating patterns. Small texture differences in an image are difficult to observe in the presence of noise. Therefore, it is necessary to analyze the image quantitatively. Quantitative measurements include run-length statistics, fractal dimension, and correlation statistics. The workstation is designed so that a radiologist can analyze the patient's images through an easy-to-use graphical user interface. The workstation software is based on standards, so that it can be run on a variety of different hardware platforms. The workstation can be used in a research environment to distinguish between images of malignant and benign breast lesions, which are difficult to diagnose visually. Further work is being done to make the workstation software into a useful clinical tool.

Understanding the process of quantitative ultrasonic tissue characterization.

Because the human vision system cannot distinguish the broad range of gray values that a computer visual system can, computerized image analysis may be used to obtain quantitative information from ultrasonographic (US) real-time B-mode scans. Most quantitative US involves programming an off-line computer to accept, analyze, and display US image data in a way that enhances the detection of changes in small-scale structures and blood flow that occur with disease. Common image textural features used in quantitative US tissue characterization consist of first-order gray-level statistics (eg, occurrence frequency of gray levels independent of location or spatial relationship) and second-order gray-level statistics dependent on location and spatial relationship, including statistical analysis of gradient distribution, co-occurrence matrix, covariance matrix, run-length histogram, and fractal features. A customized tissue signature software has been developed to analyze image data obtained from clinical US scanners. Means comparison testing and multivariate analysis techniques are used to compare the numbers generated for a particular region of interest. By integrating these techniques into the radiologist's interpretation of the sonogram, the quantitative information gained may lead to earlier detection of lesions difficult to see with the human eye.

Improving the distinction between benign and malignant breast lesions: the value of sonographic texture analysis.

To improve the ability of ultrasound to distinguish benign from malignant breast lesions, we used quantitative analysis of ultrasound image texture. Eight cancers, 22 cysts, 28 fibroadenomata, and 22 fibrocystic nodules were studied. The true nature of each lesion was determined by aspiration (for some cysts) or by open biopsy. Analysis of image texture was performed on digitized video output from the ultrasound scanner using fractal analysis and statistical texture analysis methods. The most useful features were those derived from co-occurrence matrices of the images. Using two features together (contrast of a co-occurrence matrix taken in an oblique direction, and correlation of a co-occurrence matrix taken in the horizontal direction), it was possible to exclude 78% of fibroadenomata, 73% of cysts, and 91% of fibrocystic nodules while maintaining 100% sensitivity for cancer. These findings suggest that ultrasonic image texture analysis is a simple way to markedly reduce the number of benign lesion biopsies without missing additional cancers.

Contrast information of digital imaging in laser film digitizer and display monitor.

A 10-bit or 12-bit gray scale is provided in commercial laser film digitizers. The true contrast resolution on the digitized image within a laser spot area of 200 microns in diameter is limited by both the quantum mottle and instrumentation noise. In this report, we investigated the mean value, standard deviation, and adjacent pixel correlation coefficient on a calibrated step wedge film with two laser digitizers. The results were disappointing, because we found that the evaluated contrast information is inferior to the manufacturers' specifications. On the output side, the brightnesses of different gray levels from a clinical monitor were measured with a narrow angle luminance probe and evaluated by a brief human perception study. In addition, the implications for teleradiology applications are discussed.

Tension and ATPase rate in steady-state contractions of rabbit soleus fiber segments.

Steady-state isometric tension and ATPase were studied in hyperpermeable segments of single muscle fibers from rabbit soleus muscle at 22 degrees C. The ATPase activity was due to actomyosin. The ratio of fiber ATPase to tension was used as an index of steady-state cross-bridge kinetics. Increasing the calcium ion concentration from pCa 8 to pCa 5 activated both tension and ATPase. The maximal tension was 1.35 +/- 0.07 kg/cm2. The maximal ATPase was 1.05 +/- 0.13 mumol X g-1. s-1 at pCa 5.2. ATPase activity increased with tension, such that the ratio of ATPase to tension remained constant at all calcium concentrations. In the absence of calcium, increasing the concentration of MgATP from 1 to 7 X 10(-7) M increased tension from zero to a maximum of 0.46 +/- 0.03 kg/cm2. Increasing MgATP concentration further to 1 X 10(-6) M inhibited tension. In the phase of rising tension, ATPase increased proportionally to tension, to 0.11 +/- 0.01 mumol X g-1 X s-1 at maximum tension. However, the ratio of ATPase to tension on the rising phase had a value only one-third of that seen with calcium-activated tension. Thus, low substrate concentrations, but not low calcium ion concentrations, influence cross-bridge kinetics under steady-state isometric conditions, possibly by an increase in the tension-time product during a cross-bridge cycle.