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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 288 out of 330
| Title |
Ultrasonic characterization of myocardium. |
| Author |
Miller JG, Perez JE, Sobel BE. |
| Journal |
Prog Cardiovasc Dis |
| Volume |
|
| Year |
1985 |
| Abstract |
Ultrasonic characterization of myocardium is a promising application of ultrasound to cardiac diagnosis. Its foundations rest on novel algorithms that have improved ultrasonic signal analysis, progress in the understanding of tissue determinants of the received ultrasonic energy, and sophisticated instrumentation. We shall review some approaches designed to characterize myocardium in terms of its interaction with ultrasound (as opposed to ultrasonic imaging per se) and consider the role that ultrasonic characterization may ultimately play in clinical cardiology. The material is organized in four sections. The first addresses features that distinguish conventional clinical echocardiography from ultrasonic tissue characterization and early attempts at tissue characterization and approaches undergoing development in several laboratories. Section 2 focuses on an approach to employing quantitative estimates of ultrasonic backscatter and attenuation. Section 3 reviews and compares diverse approaches for tissue characterization from several laboratories. Section 4 addresses prospects of ultrasonic tissue characterization for clinical cardiology. |
| Title |
Ultrasonic Characterization of Porosity: Theory. |
| Author |
Rose JH. |
| Journal |
Ames Lab |
| Volume |
|
| Year |
1985 |
| Abstract |
The volume fraction of pores in cast materials is often used as a quality control and product acceptance criterion. In this task-oriented paper, the use of backscattered ultrasound to characterize the volume fraction of pores in A357 cast aluminum is analyzed. Important constraints on possible measurement methods are: (1) single sided access, (2) rapid scan rates, and (3) high sensitivity (i.e., the ability to measure volume fractions on the order of .1%). The structure of this article is as follows. First, general aspects of ultrasonic scattering from porous media are discussed. These general results focus attention on the frequency dependent attentuation which is reviewed next. Then, following a proposal of Gubernatis and Domany (2), a method of determining the volume fraction and pore size is given. This method is then characterized by a figure-of-merit. Finally, the paper is concluded by a summary. |
| Title |
Ultrasonic characterization of selected renal tisuues. |
| Author |
Turnbull DH, Wilson SR, Hine AL, Foster FS. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1989 |
| Abstract |
Velocity, attenuation, and backscatter of ultrasound were measured in human renal tissues over a frequency range relevant to clinical imaging (3.5-7 MHz). Normal renal tissues, as well as three types of mass (angiomyolipoma, renal cell carcinoma, and oncocytoma) were studied, and.comparisons made of the appearance of the tissues in clinical images to their ultrasonic and pathological properties. The results showed angiomyolipoma had high attenuation and backscatter coefficients due to acoustic impedance differences between fat and smooth muscle.components of the tumour. The renal cell carcinomas were indistinguishable from normal kidney tissue, except in one case where infiltration by fatlike macrophages led to high attenuation and backscatter coefficients. This finding also supports the conclusion that fat/nonfat interfaces are a.dominant scatter mechanism in renal tissues. . |
| Title |
Ultrasonic characterization of three animal mammary tumors from three-dimensional acoustic tissue models. |
| Author |
Mamou J. |
| Journal |
Thesis(MS): Univ of Illinois |
| Volume |
|
| Year |
2005 |
| Abstract |
This dissertation investigated how three-dimensional (3D) tissue models can be
used to improve ultrasonic tissue characterization (UTC) techniques. Anatomic sites in tissue responsible for ultrasonic scattering are unknown, which limits the potential applications of ultrasound for tumor diagnosis. Accurate 3D models of tumor tissues may help identify the scattering sites. Three mammary tumors were investigated:a rat fibroadenoma, a mouse carcinoma, and a mouse sarcoma. A 3D acoustic tissue model, termed 3D impedance map (3DZM), was carefully constructed from consecutive histologic sections for each tumor. Spectral estimates (scatterer size and acoustic concentration) were obtained from the 3DZMs and compared to the same estimates obtained with ultrasound. Scatterer size estimates for three tumors were found to be similar (within 10%). The 3DZMs were also used to extract tissue-specific scattering models. The scattering models were found to allow clear distinction between the three tumors. This distinction demonstrated that UTC techniques may be helpful for noninvasive clinical tumor diagnosis. |
| Title |
Ultrasonic characterization of three animal mammary tumors from three-dimensional acoustic tissue models. |
| Author |
Mamou JM. |
| Journal |
Thesis(PhD): Univ of Illinois |
| Volume |
|
| Year |
2005 |
| Abstract |
This dissertation investigated how three-dimensional (3D) tissue models can be used to improve ultrasonic tissue characterization (UTC) techniques. Anatomic sites in tissue responsible for ultrasonic scattering are unknown, which limits the potential applications of ultrasound for tumor diagnosis. Accurate 3D models of tumor tissues may help identify the scattering sites. Three mammary tumors were investigated: a rat fibroadenoma, a mouse carcinoma, and a mouse sarcoma. A 3D acoustic tissue model, termed 3D impedance map (3DZM), was carefully constructed from consecutive histologic sections for each tumor. Spectral estimates (scatterer size and acoustic concentration) were obtained from the 3DZMs and compared to the same estimates obtained with ultrasound. Scatterer size estimates from three tumors specific scattering models. The scattering models were found to allow clear distinction between the three tumors. This distinction demonstrated that UTC techniques may be helpful for noninvasive clinical tumor diagnosis. |
| Title |
Ultrasonic characterization of whole cells and isolated nuclei. |
| Author |
Taggart LR, Baddour RE, Giles A, Czarnota GJ, Kolios MC. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
2007 |
| Abstract |
High frequency ultrasound imaging (20 to 60 MHz) is increasingly being used in small animal imaging, molecular imaging and for the detection of structural changes during cell and tissue death. Ultrasonic tissue characterization techniques were used to measure the speed of sound, attenuation coefficient and integrated backscatter coefficient for (a) acute myeloid leukemia cells and corresponding isolated nuclei, (b) human epithelial kidney cells and corresponding isolated nuclei, (c) multinucleated human epithelial kidney cells and d) human breast cancer cells. The speed of sound for cells varied from 1522 to 1535 m/s, while values for nuclei were lower, ranging from 1493 to 1514 m/s. The attenuation coefficient slopes ranged from 0.0798 to 0.1073 dB mm(-1) MHz(-1) for cells and 0.0408 to 0.0530 dB mm(-1) MHz(-1) for nuclei. Integrated backscatter coefficient values for cells and isolated nuclei showed much greater variation and increased from 1.71 x 10(-4) Sr(-1) mm(-1) for the smallest nuclei to 26.47 x 10(-4) Sr(-1) mm(-1) for the cells with the largest nuclei. The findings suggest that integrated backscatter coefficient values, but not attenuation or speed of sound, are correlated with the size of the nuclei. |
| Title |
Ultrasonic contrast agent shell rupture detected by inertial cavitation and rebound signals. |
| Author |
Ammi AY, Cleveland RO, Mamou J, Wang GI, Bridal SL, O'Brien WD Jr. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
2006 |
| Abstract |
Determining the rupture pressure threshold of ultrasound contrast agent microbubbles has significant applications for contrast imaging, development of therapeutic agents, and evaluation of potential bioeffects. Using a passive cavitation detector, this work evaluates rupture based on acoustic emissions from single, encapsulated, gas-filled microbubbles. Sinusoidal ultrasound pulses were transmitted into weak solutions of Optison/spl trade/ at different center frequencies (0.9, 2.8, and 4.6 MHz), pulse durations (three, five, and seven cycles of the center frequencies), and peak rarefactional pressures (0.07 to 5.39 MPa). Pulse repetition frequency was 10 Hz. Signals detected with a 13-MHz, center-frequency transducer revealed postexcitation acoustic emissions (between 1 and 5 /spl mu/s after excitation) with broadband spectral content. The observed acoustic emissions were consistent with the acoustic signature that would be anticipated from inertial collapse followed by "rebounds" when a microbubble ruptures and thus generates daughter/free bubbles that grow and collapse. The peak rarefactional pressure threshold for detection of these emissions increased with frequency (e.g., 0.53, 0.87, and 0.99 MPa for 0.9, 2.8, and 4.6 MHz, respectively; five-cycle pulse duration) and decreased with pulse duration. The emissions identified in this work were separated from the excitation in time and spectral content, and provide a novel determination of microbubble shell rupture |
| Title |
Ultrasonic diagnosis of breast cancer. |
| Author |
Kobayashi T. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1975 |
| Abstract |
Present status of differential diagnosis of breast cancer by ultrasound was reviewed in the light of historical development of the field, including the evaluation of the types of equipment together with the consequent clinical improvement in diagnostic accuracy rate. Differential diagnostic criteria proposed by various investigators for breast cancer were summarized and diagnostic accuracy rates for differential diagnosis of breast tumors reported by various investigators recently were tabulated and the overall accuracy rates obtained were an average of 87 and 80% for malignant lesions and benign lesions respectively. The rates were 97, 78, and 87% for scirrhous carcinoma, papillary carcinoma and medullary carcinoma respectively, and 81, 93 and 100% for T1, T2 and T3 in TNM classifications respectively. |
| Title |
Ultrasonic diagnostic methods in cardiology. |
| Author |
Reid JM. |
| Journal |
Thesis(PhD): Univ of Pennsylvania |
| Volume |
|
| Year |
1965 |
| Abstract |
This investigation of the use of the ultrasound in the diagnosis of cardiac disease includes the design, use, and evaluation of suitable equipment. Chapter I reviews the history of ultrasound in diagnosis. Chapter II describes the equipment which was designed, based on information in published work, to record the distance from the chest wall to reflecting structures within the chest. The clinical work described in Chapter III includes the use of the apparatus to verify the previous findings, and to extend the usefulness of this technique. (partial abstract) |
| Title |
Ultrasonic diagnostic system for interactive interrogation of adult brain through intact skull. |
| Author |
Fry FJ, Sanghvi NT, Morris RF, Clendenon JL, Dines KA, Patrick JT, Goss SA. |
| Journal |
Invest Radiol |
| Volume |
|
| Year |
1982 |
| Abstract |
An integrated ultrasonic system has been developed employing static gray scale imaging, digital image processing, and analyses of quantitative ultrasonic backscatter for interactive interrogation of brain through the adult human skull. Operating at 750 kHz, to avoid severe spatial and temporal pulse distortion which accompany ultrasonic transkull transmission at higher frequencies, storage and image processing of successive images taken at selected gain settings in the same image plane allow the reconstruction of a composite cross-section of the brain and skull and enable visualization of internal brain structure. Analyses of digitized backscatter data obtained with the visualization transducer over selectable interrogation paths referenced to the cross-sectional image permit quantitative classification of tissue type independent of qualitative visual image analysis, such that enhanced diagnostic potential is provided. A previous paper described in detail the modifications of the commercial ultrasound diagnostic unit which serves as the core of this system. The present paper presents the rationale for the integrated system design approach, as well as a description of graphics display and tissue classification features which have been incorporated into the instrumentation configuration and are deemed necessary for successful transkull ultrasonic imaging and diagnosis. |
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