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BRL Abstracts Database |
Your search for ultrasound produced 3296 results. Page 32 out of 330
Title |
Advanced ultrasonic imaging techniques for breast cancer research. |
Author |
Insana MF, Oelze ML. |
Journal |
Book Chapter |
Volume |
|
Year |
2006 |
Abstract |
Introduction - The goal of cancer imaging is to exploit disease-specific object contrast mechanisms
that provide very specific information about cellular structure and function to help diagnose
and manage diseases and to develop tools for scientific investigation. This chapter
reviews several ultrasonic methods for obtaining detailed histological descriptions of
mammary tissue noninvasively that are related directly to tumor growth.
Ultrasonic imaging (sonography) is now routinely applied in a clinical setting as an
adjunct to mammography and the physical examination. Its role is primarily to differentiate
solid tumors from cysts and to guide needle and surgical excision biopsies. Tumors
larger than 8 mm are readily detected as hypoechoic (lower echo strength) regions.
Unfortunately sonographic features are frequency nonspecific; the appearance of benign
masses, such as fibrocystic lesions and fibroademomas, is often similar to that of malignant
lesions, such as infiltrating ductal carcinoma (IDC) and infiltrating lobular carcinoma
(ILC). Sonography is very useful for locating lesions and ruling out cysts, although
the definitive differential diagnosis requires pathological analysis of biopsy samples. A
needle biopsy is minimally invasive but suffers from sampling errors; small lesions can
be easily missed. Surgical biopsies remove more tissue, reducing sampling errors, but
introduce the risks and expenses associated with any surgical procedure. Surgical biopsy
is a hybrid diagnostic-therapeutic procedure, so we would like to use it only when we’re
reasonably confident that cancer is present. Our goal is to increase the diagnostic information
provided by ultrasound scans safely and at low cost, so that frequent serial
imaging of patients at risk can be applied to reduce the number of questionable biopsies
without sacrificing diagnostic performance. Such methods can be used periodically for
the initial diagnosis and regularly for monitoring a patient’s response to treatment.
Working against our proposed expanded use of ultrasound is the complexity and
diversity of breast cancer and natural inter-patient variability. Since histopathology is
how cancer is defined, it is completely accurate at one instant of time except for human
error. Radiological procedures are strong at detecting and localizing lesions but are rarely
used to classify disease since images only describe a small subset of the total histological
feature space. Thus it is unlikely that any one diagnostic test can reliably detect and
classify breast cancers in all patients.
Identifying diverse disease processes is improved by increasing the feature space for
classification. The best strategy is to provide decision makers with several independent
features related uniquely to tissue properties that span the range of disease phenotypes. A
simple example is the current combination of mammography and palpation. Mammography
is most accurate for detecting early tumors that produce microcalcifications. Manual
palpation exposes tumors that become mechanically stiff. Insofar as the effects are
uncorrelated, their combination more effectively aids diagnosis than each applied individually.
Even recent molecular imaging methods that seek to reveal and treat suspicious
regions based on high angiogenic activity can fail when used alone [45]. Promising new
approaches strive to recognize tumors that express a broad range of angiogenic factors
and related molecular signals. Like other researchers, we have turned to the molecular
biology of cancer to find hallmark features for imaging.
From the literature of the past two decades, a richly detailed picture of the biology
of breast cancer is emerging [16,61,78]. It is clear that the initiation, rate of progression,
and occurrence of malignant transformation are determined by a combination of genetic
and epigenetic factors; the later encompassed by the term “cellular microenvironment”.
Many of these discoveries suggest new opportunities for combined cancer imaging and
treatment that promise increased sensitivity and specificity. One manifestation is the new
field of molecular imaging [4, 60, 79]. Most molecular imaging approaches include development
of blood-born particles, known as probes or beacons, with biologically active
surfaces. These particles target disease-specific molecular sites in the body and emit or
reflect energy that can be sensed by current imaging modalities [1, 13, 50]. The development
of targeted contrast agents is largely a chemical synthesis problem; one of being
able to functionalize particle surfaces so they remain stably active while circulating in
the blood stream seeking their targets.
Our approach is to image histological features of breast tissues that influence the
cellular microenvironment (defined below) without contrast enhancement through the
unique capabilities of ultrasound. Ultrasound is highly sensitive to subtle variations in
the mechanical properties of tissues at many scales that often change as the composition
and distribution of cells is modified by disease. To model sound tissue interactions, tissues
are viewed from the materials science viewpoint as a viscoelastic continuum (think
of gelatin) in which compressional sound waves travel. Within glandular tissues, cells,
connective tissues and the microvasculature reflect a small amount of the sound energy
back to the detector. Because the wavelength of diagnostic ultrasound (150 ¹m) is about
300 times longer than the wavelength of visible light (500 nm), the spatial resolution
possible for ultrasound is far below optical microscopy. Nevertheless, lower attenuation
allows ultrasound to penetrate deeper into the body than light and therefore it is unnecessary
to extract tissue samples for analysis. Rather than resolving individual structures,
a statistical ultrasonic analysis examines the statistical properties of echo signals to estimate
average properties of tissue structures at the scale of the cell. For example, we
can create parametric ultrasound images where the image pixels represent the average
size of scatterers. Using pre-image echo signals from clinical instruments and advanced
signal processing methods, parametric ultrasound images quantify structural features of
fibrotic tissues and regions of cellular hypertrophy and hyperplasia with the spatial resolution
of sonography. In this application, ultrasound is applied to describe microscopic
mechanical properties of tissues.
We can also use ultrasound to track tissue motion and thereby observe the macroscopic
mechanical properties of tissues using the techniques of elasticity imaging. As we show below, cancer modifies how cells are connected to one another over a long distance,
a feature of the disease that is often missed by histopathology. Ultrasound can detect
the spatial distribution of tiny local movements caused when tissues are gently squeezed
to estimate viscoelastic properties with the spatial resolution of sonography. Elasticity
imaging can describe desmoplasia, edema, and other processes that stiffen tissue. It also
describes ultrastructural changes to the intra- and inter-lobular stroma that alter how water
is attracted to the extracellular matrix and how collagen fibers are cross linked. Combining
the microscopic and macroscopic ultrasonic features, we gain new perspectives
on cancer progression and can track the course of disease safely and with low cost.
To be successful at this research requires a truly interdisciplinary effort, where the
rapid advances in cancer biology are integrated with a precise understanding of how ultrasound
interacts with tissues to view these processes. Consequently, our chapter begins
with a review of modern theories of breast cancer formation and the interactions between
ultrasonic energy and biological tissues. |
Title |
Advances in the application of utlrasound in food analysis and processing. |
Author |
McClements DJ. |
Journal |
Trends Food Sci Technol |
Volume |
|
Year |
1995 |
Abstract |
Ultrasonic techniques are finding increasing use in the food industry for both the analysis and modification of foods. Low-intensity ultrasound is a non-destructive technique that provides information about physicochemical properties, such as composition, structure, physical state and flow rate. High-intensity ultrasound is used to alter, either physically or chemically, the properties of foods, for example to generate emulsions, disrupt cells, promote chemical reactions, inhibit enzymes, tenderize meat and modify crystallization processes. |
Title |
Age dependence of ultrasonically induced lung hemorrhage in mice. |
Author |
Dalecki D, Child SZ, Raeman CH, Cox C, Penney DP, Carstensen EL. |
Journal |
Ultrasound Med Biol |
Volume |
|
Year |
1997 |
Abstract |
Thresholds for ultrasonically induced lung hemorrhage were determined in.neonatal mice (24-36 h old), juvenile mice (14 d old) and adult mice (8-10 weeks.old) to assess whether or not the threshold for lung hemorrhage is dependent.upon age. Ultrasonic exposures were at 1.15 MHz with a pulse length of 10.microseconds, pulse repetition frequency of 100 Hz and a total exposure duration.of 3 min. The threshold for lung hemorrhage occurred at a peak positive acoustic.pressure of approximately 1 MPa for mice in all three age groups. Although the.thresholds were similar for neonatal, juvenile and adult mice, the sizes of the.suprathreshold hemorrhages were significantly larger in adult mice than in.neonatal or juvenile mice. . |
Title |
Age-dependent threshold and superthreshold behavior of ultrasound-induced lung hemorrhage in pigs. |
Author |
O'Brien WD Jr, Simpson DG, Frizzell LA, Zachary JF. |
Journal |
Proc Ultrason Symp IEEE |
Volume |
|
Year |
2001 |
Abstract |
Age-dependent threshold and superthreshold behavior of ultrasound-induced lung hemorrhage was investigated with 116 4.9?1.6-day-old neonate crossbred pigs, 103 39?5-day-old crossbred pigs, and 104 58?5-day-old crossbred pigs. Exposure conditions were: 3.1 MHz, 10-s exposure duration, 1-kHz PRF, and 1.4-?s pulse duration. The in situ (at the pleural surface) peak rarefactional pressure ranged between 2.2 and 10.4 MPa with either 8 or 9 acoustic pressure groups for each of the three pig ages (12 pigs/exposure group) plus sham exposed pigs; there were no lesions in the shams. Pigs were exposed bilaterally with the order of exposure (left and right lung) and acoustic pressure both randomized. Logistic regression analysis was used to examine the dependence of the lesion incidence rates on in situ peak rarefactional pressure, left versus right lung, order of exposure (first versus second) and age in three categories. Likewise, lesion depth and root surface area were analyzed using Gaussian to bit regression analysis. A significant threshold effect on lesion occurrence was observed as a function of age; younger pigs were less susceptible to lung damage given equivalent in situ exposure. Oldest pigs had significantly lower thresholds (2.63?0.27 MPa) than middle-aged pigs (4.84?0.49 MPa). The oldest pigs also had lower thresholds than neonate pigs (3.62?0.44 MPa). Overall the oldest pigs were most sensitive to lung damage, and neonates were more susceptible than middle-aged pigs. Also, an unexpected result was observed. The ultrasound exposures were bilateral and the threshold results reported above were based on the lung that was first exposed. After the first lung was exposed, the pig was turned over and the other lung was exposed to the same acoustic pressure. There was a significant decrease (greater than the confidence limits) in threshold occurances: 3.62 to 2.67, 4.84 to 2.23 and 2.63 to 1.04 MPa, for neonates, middle-aged, and oldest pigs, respectively, in the second lung exposed. Thus, a subtle effect in lung physiology resulted in a major effect in the thresholds. |
Title |
Age-related mechanical properties of human skin: An in vivo study. |
Author |
Escoffier C, Rigal JD, Rochefort A, Vasselet R, Leveque JL, Agache PG. |
Journal |
J Invest Dermatol |
Volume |
|
Year |
1989 |
Abstract |
We have investigated in vivo how various viscoelastic parameters that describe the mechanical properties of the human skin may vary with age. Accordingly, we have used a mechanical device that records the torsional extensibility of the skin. When submitted to a low torque, the time-response curve of the skin affords the determination of the immediate extensibility (UE), the immediate recovery (UR), the viscoelastic part of the deformation (UV), the elastic recovery (UR/UE), and the creep relaxation time (tau). Because the skin thickness varies with age and primarily governs the mechanical properties, it was measured through an ultrasound technique at the same sites (forearm) where the torque was applied. The results show that the skin maintains its thickness and extensibility up to the seventh decade as opposed to its elasticity or recovery capacities, which decrease from an early age. The viscous part of the deformation is constant through life, whereas the creep relaxation time decreases linearily with age. Except for skin thickness, no differences in these parameters between men and women were detected. The significance of these results are discussed in terms of structure alterations. The determination of the elastic recovery (UR/UE) appears to be a parameter of choice for illustrating skin aging. .. |
Title |
Agglomerated nuclei in ultrasonicated Vicia faba roots: A partial elucidation of their derivation. |
Author |
Cataldo FL, Miller MW, Kaufman GE. |
Journal |
Environ Exp Bot |
Volume |
|
Year |
1976 |
Abstract |
An experiment was performed to determine whether ?Agglomerated Mitotic? cells, anomalies induced in Vicia faba root meristems by 2.0 MHz ultrasound, are in fact mitotic cells. Cells were synchronized at the G1/S border by hydroxyurea, ultrasonicated, the roots then transferred to fresh growth medium containing [3H]-thymidine, and examined at various times thereafter by autoradiography. Bridged Prophases, Bridged Metaphases, ?Agglomerated Mitotics?, and normal mitotics were scored for the presence or absence of radioactive label. Bridged Prophases, Bridged Metaphases, and normal mitotics appeared in the population at 22 hr following release from the G1/S block and were 3H-labelled, indicating transit through S-phase. ?Agglomerated Mitotics? appeared in the population much earlier (6 hr) and were unlabelled. Therefore, these ?Agglomerations? are no longer considered to be mitotic cells, and are instead thought to represent a morphological nuclear change induced in interphase cells by ultrasound. |
Title |
Aggressive region growing for speckle reduction in ultrasound images. |
Author |
Chen Y, Yin R, Flynn P, Broschat S. |
Journal |
Pattern Rec Lett |
Volume |
|
Year |
2003 |
Abstract |
Speckle appears in all conventional medical B-mode ultrasonic images and can be an undesirable property since it may mask small but diagnostically significant features. In this paper, an adaptive filtering algorithm is proposed for speckle reduction. It selects a filtering region size using an appropriately estimated homogeneity value for region growth. Homogeneous regions are processed with an arithmetic mean filter. Edge pixels are filtered using a nonlinear median filter. The performance of the proposed technique is compared to two other methods--the adaptive weighted median filter and the homogeneous region growing mean filter. Results of processed images show that the method proposed reduces speckle noise and preserves edge details effectively. |
Title |
Airborne ultrasound: Measurement and possible adverse effects. |
Author |
Herman BA, Powell D. |
Journal |
Rep U S Dept HEW |
Volume |
|
Year |
1981 |
Abstract |
A literature study was undertaken to investigate research efforts concerning possible adverse effects of airborne ultrasound on humans. Findings of this research, as well as proposed exposure-limiting criteria are presented. Measurement techniques for airborne ultrasound are reviewed and the results of output measurements of devices producing this acoustic radiation are discussed. |
Title |
AIUM's position on reporting parameters of bioeffects experiments. |
Author |
Edmonds PD. |
Journal |
Ultrasound Med Biol |
Volume |
|
Year |
1989 |
Abstract |
Abstract not available. |
Title |
Albunex Does Not Increase the Sensitivity of the Lung to Pulsed Ultrasound. |
Author |
Raeman CH, Dalecki D, Child SZ, Meltzer RS, Carstensen EL. |
Journal |
Echocardiography |
Volume |
|
Year |
1997 |
Abstract |
If cavitation in the vasculature of the lung is the physical mechanism responsible for lung hemorrhage, then addition of cavitation nuclei to the blood should enhance the bioeffect. To test the cavitation hypothesis, the extent of lung hemorrhage in mice injected with the echocontrast agent, Albunex(R), was compared to lung hemorrhage in animals injected with saline. Animals were exposed for 5 minutes to 1.1-MHz pulsed ultrasound (10 µs pulse length, 100-Hz pulse repetition frequency) at a peak positive pressure at the surface of the animal of 2 MPa. This exposure is approximately twice the threshold pressure amplitude for lung hemorrhage. Lesion areas did not differ significantly in the two groups of animals and were approximately equal to the lesion area in uninjected mice from an earlier study where acoustic exposures were the same. Neither this study nor a related study of hemolysis in vivo suggests that use of Albunex in echocardiographic procedures increases the risk of bioeffects. |
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