Computer-Aided Diagnosis of Solid Breast Lesions Using an Ultrasonic Multi-Feature Analysis Procedure

We have developed a family of quantitative descriptors in order to provide noninvasive, reliable means of distinguishing benign from malignant breast lesions. These include acoustic descriptors (“echogenicity,” “heterogeneity,” “shadowing”) and morphometric descriptors (“area,” “aspect ratio,” “border irregularity,” “margin definition”). These quantitative descriptors are designed to be independent of instrument properties and physician expertise. Our analysis included manual tracing of lesion boundaries and adjacent areas on grayscale images generated from RF data. To derive quantitative acoustic features, we computed spectral-parameter maps of radio-frequency (RF) echo signals (using a sliding-window Fourier analysis) of the lesion and adjacent areas. We quantified morphometric features by geometric and fractal analysis of traced lesion boundaries. Although no single parameter can reliably discriminate cancerous from non-cancerous breast lesions, multi-feature analysis provides excellent discrimination of cancerous and non-cancerous lesions. Our analysis of data acquired during routine ultrasonic examination of 130 biopsy-scheduled patients produced a receiver-operating characteristic (ROC) area under the curve (AUC) of 0.947±0.045. Lesion-margin definition, spiculation, and border irregularity were the most useful among the quantitative descriptors; some morphometric features (such as border irregularity) also were particularly effective in lesion classification. Our results are consistent with many of the Breast Imaging Reporting and Data System (BI-RADS) breast-lesion-classification criteria in use today. DOI: http://dx.doi.org/10.3329/bjmp.v4i1.14672 Bangladesh Journal of Medical Physics Vol.4 No.1 2011 1-10

Computer simulations of ultrasonic heating for ocular therapy

Computer simulations are being performed to model the temperature patterns produced during ultrasonically induced hyperthermia of ocular tumours. The software package for these simulations incorporates operator interaction and uses tissue geometry obtained from B-mode data. Previous studies used geometric approximations for the incident beams used for hyperthermia. In the current study, these beams were computed using diffraction analysis to obtain more realistic simulations of clinical exposures.

[Gender related prognostic factors in the first admission of DSM-III schizophrenic patients]

In the group of the 80--DSM-III--first schizophrenic out patients we evaluated differences between men and women in predictive factors. First symptoms of illness were manifested later in women than in man. What's more women achieved better results in social functioning as well in global assessment, as in partial criteria. Work was the only domain in which there wasn't any differences in favour of women. Women had a lower rate of personality disorders. There were no differences in psychiatric symptoms severity.

Spectrum-analysis and neural networks for imaging to detect and treat prostate cancer

Conventional B-mode ultrasound currently is the standard means of imaging the prostate for guiding prostate biopsies and planning brachytherapy to treat prostate cancer. Yet B-mode images do not adequately display cancerous lesions of the prostate. Ultrasonic tissue-type imaging based on spectrum analysis of radiofrequency (rf) echo signals has shown promise for overcoming the limitations of B-mode imaging for visualizing prostate tumors. This method of tissue-type imaging utilizes nonlinear classifiers, such as neural networks, to classify tissue based on values of spectral parameter and clinical variables. Two- and three-dimensional images based on these methods demonstrate potential for guiding prostate biopsies and targeting radiotherapy of prostate cancer. Two-dimensional images are being generated in real time in ultrasound scanners used for real-time biopsy guidance and have been incorporated into commercial dosimetry software used for brachytherapy planning. Three-dimensional renderings show promise for depicting locations and volumes of cancer foci for disease evaluation to assist staging and treatment planning, and potentially for registration or fusion with CT images for targeting external-beam radiotherapy.

Three-dimensional ultrasound analyses of the prostate

Although conventional ultrasonography has proven to be clinically useful for depicting many types of cancerous lesions, it cannot distinguish reliably between cancerous and noncancerous tissue of the prostate. Therefore, conventional transrectal ultrasonography (TRUS) is used primarily for general evaluations of the gland and for guiding biopsies based on clearly imaged anatomic features such as the capsule, seminal vesicles, and urethra. Spectrum analysis extracts ultrasound signal parameters associated with biopsy-proven tissue types, and these parameters are then classified using neural network tools such as learning vector quantization, radial basis, and multilayer perceptron algorithms. Classification of cancerous and noncancerous prostate tissue using neural networks produces receiver operating characteristic (ROC) curves of 0.87 +/- 0.04 compared with 0.64 +/- 0.04 for conventional ultrasonography. To image the prostate using these methods, parameter values are computed at each pixel location, then translated into a score for the likelihood of cancer using a look-up table generated using the best classification algorithm. The score for cancer likelihood is expressed as a gray-scale or color value, and the resulting image may be useful to guide biopsies or therapy. Changes in parameter or score values over time potentially can be used to assess progression of disease or efficacy of therapy.

Study of ultrasonic contrast agents using a dual-frequency band technique

We have developed a dual-frequency band technique to study frequency-dependent phenomena associated with ultrasonic contrast agents. Our technique uses a superimposed high-frequency (10 MHz) broad-band ultrasound (US) pulse to investigate contrast agent interaction with a low-frequency (e.g., 0.5 MHz) ultrasonic field. Our digitally controlled system has the ability to produce two colinear, confocal US pulses at different center frequencies, to adjust the relative phasing and pulse repetition frequency of each pulse, and to acquire digital backscatter data. A series of experimental studies demonstrated that the high-frequency backscatter signal responded to several phenomena induced in contrast agent particles by the low-frequency beam. These phenomena included radial pulsations, nonlinear oscillations and depletion. Initial results also demonstrated a relative phase shift between the high- and low-frequency signals; this shift is due to a difference in sound velocity at these frequencies, and it may convey information about the contrast agent concentration.

Statistical framework for ultrasonic spectral parameter imaging

This study examines the statistics of ultrasonic spectral parameter images that are being used to evaluate tissue microstructure in several organs. The parameters are derived from sliding-window spectrum analysis of radiofrequency echo signals. Calibrated spectra are expressed in dB and analyzed with linear regression procedures to compute spectral slope, intercept and midband fit, which is directly related to integrated backscatter. Local values of each parameter are quantitatively depicted in gray-scale cross-sectional images to determine tissue type, response to therapy and physical scatterer properties. In this report, we treat the statistics of each type of parameter image for statistically homogeneous scatterers. Probability density functions are derived for each parameter, and theoretical results are compared with corresponding histograms clinically measured in homogeneous tissue segments in the liver and prostate. Excellent agreement was found between theoretical density functions and data histograms for homogeneous tissue segments. Departures from theory are observed in heterogeneous tissue segments. The results demonstrate how the statistics of each spectral parameter and integrated backscatter are related to system and analysis parameters. These results are now being used to guide the design of system and analysis parameters, to improve assays of tissue heterogeneity and to evaluate the precision of estimating features associated with effective scatterer sizes and concentrations.

Roles of hematocrit and fibrinogen in red cell aggregation determined by ultrasonic scattering properties

Parameters of the power spectrum of backscattered echoes were applied to quantitatively evaluate red cell aggregation in vitro. Human red cell suspensions were circulated in a closed loop of tubing, and ultrasonic, radiofrequency, echo-signal data were obtained using a 10-MHz transducer. Data acquisition was performed at 30-s to 1-min intervals for 5 min after flow stoppage. Two parameters of the normalized power spectrum of the echo signals, spectral slope and Y-intercept, were computed, and estimates of two scattering properties, the scatterer size and acoustic concentration were calculated from these parameters using equations based on scattering theory. Size and acoustic concentration were observed as they changed over time after the stoppage of flow. The key findings were that hematocrit affected the rate of cell aggregation while fibrinogen controlled aggregate size and acoustic concentration.

Ultrasonic tissue characterization of experimental venous intimal hyperplasia

Ultrasonic tissue characterization (UTC) employing slope and Y-intercept parameters from the normalized power spectrum of backscattered echoes was employed in vivo to study compositional changes in the walls of pig jugular veins in which thrombi were experimentally induced. Light microscopy revealed these changes to be intimal hyperplasia with an early predominance of smooth muscle cells and a later mixture of smooth muscle cells and collagen deposits. UTC distinguished intimal hyperplasia from previously reported data from luminal thrombosis UTC. Furthermore, UTC was able to discriminate between early (predominantly smooth muscle cells) and older (smooth muscle cells plus collagen deposits) intimal hyperplasia. The study suggests that intimal hyperplasia in the experimental model used may be organized thrombus and that UTC may be able to follow both the development of wall changes as well as luminal changes occurring in venous thrombosis.

Simulation studies of ultrasonic backscattering and B-mode images of liver using acoustic microscopy data

Data obtained from a scanning laser acoustic microscope (SLAM) were used to examine several aspects of ultrasonic backscattering from the liver. Phase interferograms from normal and abnormal human-liver specimens were digitized, and a series of algorithms was used to compute images of propagation velocity within the specimens. The propagation velocity images were then employed to simulate A- and B-mode results. These initial simulations were used to investigate how ultrasonic echo signals are related to tissue microstructure. Among the topics examined were B-mode speckling, frequency and beamwidth effects, and angulation dependencies.

Computer model of ultrasonic hyperthermia and ablation for ocular tumors using B-mode data

Computer simulations have been conducted to examine hyperthermia and ablation for treating ocular tumors. An interactive software package has been implemented that permits relevant tissue dimensions to be determined from B-mode data. This package also permits interactive beam positioning, and it provides image displays depicting computed absorbed doses and temperature rises. Results are presented showing how hyperthermia temperature patterns are influenced by beam position, beam geometry and frequency. Images showing ablative temperature rises at various time intervals are also presented. For hyperthermia, geometric models of beam profiles showed that a non-uniform beam pattern (with a central low-intensity region) can produce more uniform heating of small ocular tumors than a beam with a uniform intensity profile. For a given tumor, the uniformity of hyperthermia temperatures was found to be a function of frequency, with 4.75 MHz providing reasonably uniform results for typical tumor heights (near 7 mm). For ablation, diffraction computations were employed to calculate beam intensity profiles; results show an initially rapid rise in temperature levels with subsequent, slower heating beyond the -3-dB limits of the focal volume. The model is now being refined, and additional phenomena, including nonlinear propagation, will be incorporated.

Temporal changes of acid phosphatase, arylsulphatase, beta-galactosidase and beta-N-acetyl-D-glucosaminidase activities in subcellular fractions of rat liver

In this paper circadian changes in the liver enzyme activities of rat housed under highly standardized conditions with 12: 12 hour light-dark cycle are shown. Activities of acid phosphatase, arylsulphatase, beta-galactosidase and beta-N-acetyl-D-glucosaminidase in microsomal and lysosomal fractions and crude homogenate were estimated every 4 hr during one 24-hr period. The enzyme activities were related to 1 mg of protein, 1 mg of DNA and 1 g fresh tissue. Daily changes of enzyme activities were found. In case of activity calculated per 1 mg DNA two maxima at 0500 and at 2100 hr were observed, while activity calculated per 1 mg protein showed one maximum at 0500 hr. Activity calculated per 1 g fresh tissue showed the maximum at 0500 hr for each enzyme only in microsomal fraction. As far as acrophase table is concerned for all enzymes and fractions the acrophase occurred during the night. The obtained results are discussed in relation to lysosomal enzymes synthesis process as well as different reference values.