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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 117 out of 330
| Title |
Evaluation of the bioeffects of prenatal ultrasound exposure in the cynomolgus macaque (Macaca fascicularis): III Developmental and hematologic studies. |
| Author |
Tarantal AF, O'Brien WD Jr, Hendrickx AG. |
| Journal |
Teratology |
| Volume |
|
| Year |
1993 |
| Abstract |
The multiple applications of diagnostic ultrasound in obstetrics have resulted in a continued rise in the prenatal population exposed each year. Although human epidemiologic and experimental studies with various animal models have not consistently documented any significant, reproducible findings related to clinically relevant exposures, technologic changes in scanning equipment and gaps in our knowledge regarding the interaction(s) of ultrasound with tissues emphasize the need to pursue safety issues. Studies with nonhuman primates have provided information on the potential for pre and postnatal effects on offspring exposed repeatedly during gestation (ATL MK 600, 7.5 MHz, ISPTA = 27 mW/cm2; ISPPA = 85 W/cm2; Estimated power = 12 mW--scanned for 10 min 5 times weekly gestational day [GD] 20-35; 3 times weekly GD 36-60; once weekly for 20 min.GD 60-150). These studies have indicated transient effects on body weight, white blood cell counts (WBCs), and muscle tone postnatally. In an effort to confirm these findings and focus on hematologic changes, a second series of studies was initiated using the same exposure conditions (N = 22; 11 exposed, 11 sham controls). Data derived from both studies were combined and confirmed transient reductions in body weights for infants up through 4 months of age (P < or = 0.03); no statistically significant differences in muscle tone were noted. Similar to the original findings, WBCs were transiently reduced on days 3 (P < or = 0.02) and 21 (P < or = 0.05); prenatal sampling indicated a significant difference between the groups on GD 140 (P < or = 0.04). No direct effects were evident in bone marrow aspirates collected on postnatal days 3, 9, and 21 +/- 1. Although animals were able to compensate for these observed changes and remained unaffected by their occurrence, additional studies will be required to further our understanding of this phenomenon. |
| Title |
Evaluation of the bioeffects of prenatal ultrasound.exposure in the cynomolgus macaque (Macaca.fascicularis): I. Neonatal/infant observations. |
| Author |
Tarantal AF, Hendrickx AG. |
| Journal |
Teratology |
| Volume |
|
| Year |
1989 |
| Abstract |
The frequency of use of ultrasonography for evaluating the developing embryo/fetus has continued to rise although the possible risks from exposure still remain uncertain. The cynomolgus macaque (Macaca fascicularis) is currently being used in our laboratory as a model to assess these risks. In utero exposure was performed utilizing a commercial real-time mechanical sector scanner with a 7.5 MHz scanhead (ATL, MK 600). Maximum acoustic power output for this unit is as follows: I(SPTA) = 12.0 mW/cm2, I(SPPA) = 98 W/cm2, and Im = 137 W/cm2. Animals exposed to ultrasound (N = 16) were scanned five times weekly on gestational days (GD) 21-35 +/- 2 for 10 minutes/exam (m/e), three times weekly on GD 36-60 +/- 2 for 10 m/e, and once weekly on GD 61-150 +/- 2 for 20 m/e. Controls (N = 14) were "scanned" with the unit placed on standby. Assessment of simian Apgar scores at 1, 5, and 10 minutes of life revealed higher scores for treated animals at 10 minutes (P less than or equal to 0.045); greater scores in muscle tone (P less than or equal to 0.013) and color (P less than or equal to 0.016) were observed. Evaluation of morphometrics at birth including weight, biparietal diameter, occipitofrontal diameter, head circumference, hand and foot lengths, humerus and femur lengths, arm circumference, chest circumference, tail length, skinfold thickness, and crown-rump length (CRL) indicated a significant reduction in only two parameters,.birth weight (P less than or equal to 0.027) and CRL (P less than or equal to 0.033)..Hematologic analysis at 2 +/- 1, 9 +/- 1, and 16 +/- 1 days of life revealed a significant difference in white blood cell counts (WBCs). Treated animals displayed lower WBCs with reductions in numbers of segmented neutrophils and monocytes at all ages observed. Hematologic differences were not significant by 5-6 months of age. No abortions, gross malformations, or stillbirths were observed in the exposed animals. |
| Title |
Evaluation of the bioeffects of prenatal ultrasound.exposure in the cynomolgus macaque (Macaca.fascicularis): II. Growth and behavior during the.first year. |
| Author |
Tarantal AF, Hendrickx AG. |
| Journal |
Teratology |
| Volume |
|
| Year |
1989 |
| Abstract |
The extensive use of ultrasonography for the prenatal assessment of growth and.development continues to present questions regarding biological effects. We are currently evaluating a nonhuman primate model (Macaca fascicularis) exposed to ultrasound from gestational day (GD) 21 to 152 +/- 2. Exposures were performed with a commercial real-time sector scanner (ATL, MK 600); animals were scanned five times weekly on GD 21-35 +/- 2, three times weekly on GD 36-60 +/- 2, and once weekly on GD 61-150 +/- 2. The length of exposure was approximately the same as human exposure (GD 21-60 +/- 2 = 10 min/exam and GD 61-150 +/- 2 = 20 min/exam) although the frequency of the examinations was considerably greater. Initial reports indicated differences between control and treated animals including lower birth weight, higher simian Apgar scores, and changes in select hematologic parameters. Follow-up evaluations of growth during the first year included measurements of body weight, hand and foot lengths, humerus and femur lengths, biparietal and occipitofrontal diameters, head circumference, arm circumference,.chest circumference, skinfold thickness, and crown-rump length. Results indicated a.significant reduction in body weight in treated animals during the first three months, with nonsignificant differences during the following nine months. Hematologic analysis including complete blood counts (CBC) and clinical biochemistry at 6, 9, and 12 months of age were not significantly different. A series of behavioral evaluations including a neurobehavioral test battery (NBT) and tests assessing motor and cognitive skills were included. The NBT revealed increased muscle tone in treated animals at one, two, and four days. In an observation cage (week 1-14) more quiet activities were displayed by treated animals. Group differences in performance of motor and cognitive tasks were observed and may be attributable to agitation and difficulties in adjusting to test environments. There were no group differences observed in discrimination learning. When considering the possible implications to the human population, it is important to consider the amount of exposure these animals received, and the fact that most of the effects observed appeared to be transitory. Although human epidemiological studies have not.revealed any significant bioeffects, the "prudent use" of diagnostic ultrasound should still be kept in mind. This is especially significant with the current rise in the use of endovaginal scanning and pulsed Doppler. |
| Title |
Evaluation of the temporal stability of Definity using double passive cavitation detection |
| Author |
Gauthier M, King DA, O'Brien WD Jr. |
| Journal |
J Ultrasound Med |
| Volume |
|
| Year |
2013 |
| Abstract |
|
| Title |
Evaluation of the threshold for lung hemorrhage by diagnostic ultrasound and a proposed new safety index. |
| Author |
Church CC, O'Brien WD Jr. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
2007 |
| Abstract |
In a recent report (O?Brien et al. (2006b), it was suggested that the current expression for the mechanical index (MI) was not well suited to its function of quantifying the likelihood of an adverse biological effect after exposure of the gas-filled lung to diagnostic ultrasound. The purpose of this study was to analyze the relatively large database of experimental thresholds for the induction of lung hemorrhage to: (i) determine which variable(s) best describe the data and (ii) use the resulting equation to obtain a new formulation for the MI for lung exposures. Data from 14 studies of lung hemorrhage in four common laboratory animals (mouse, rat, rabbit and pig) were tabulated with regard to five common acoustic variables: center frequency (fc), pulse repetition frequency (PRF), pulse duration (PD), exposure duration (ED) and the threshold in situ peak rarefactional pressure (pr). The 34 threshold data points were fit by linear regression to: (i) a multiplicative model of the other variables, pr = AfcBPRFCPDDEDE, where A is a constant; (ii) 14 ?reduced? models in which one or more variables were not included in the analysis; (iii) four models in which a multiplicative combination of variables has a common name e.g., duty factor; and (iv) the general form of the current expression for the MI. The MI was shown to provide a poor fit to the threshold data (r2 = 0.382), as were three of the four named models. The best fits were found for the complete model and for three reduced models, all of which contain the exposure duration. Because the implementation of a time-dependent safety parameter would present significant practical difficulties, a different model, pr = AfcBPRFCPDD, was chosen as the basis for the new MI. Thus, the expression for the lung-specific mechanical index, MILung, includes several, rather than only one, of the relevant acoustic variables. This is the first potential safety index developed as a direct result of experimental measurements rather than theoretical analysis. |
| Title |
Evaluation of the unscanned soft-tissue thermal index. |
| Author |
O'Brien WD Jr, Ellis DS. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
1999 |
| Abstract |
The monopole-source solution was used to calculate the three-dimensional complex acoustic pressure field for focused circular apertures in a medium having homogeneous acoustic and thermal properties. The three source diameters were 1, 2, and 4 cm and the eight transmit f-numbers (ratio of the radius of curvature/source diameter) were 0.7, 1.0, 1.3, 1.6, 2.0, 3.0, 4.0, and 5.0. For these focused field geometries, eight ultrasonic frequencies were evaluated (1, 2, 3, 4, 5, 7, 9, and 12 MHz) from which the three-dimensional temperature distribution was calculated using the bio-heat transfer equation in homogeneous, perfused media (attenuation=absorption=0.3 dB/cm-MHz; perfusion length: 1.0 cm). For each of the 192 cases, the acoustic field was normalized to the derated spatial peak, temporal average intensity (ISPTA.3) of 720 mW/cm2, the maximum value allowed by the FDA 510(k) diagnostic ultrasound equipment approval process. Using the normalized acoustic field, the axial temperature increase profiles and the maximum temperature increases (ΔTmax) were determined for each case. Also, from the normalized acoustic field, the unscanned soft-tissue thermal index (TIS) was determined. In general, ΔTmax, TIS, and source power increase with increasing transmit f-number, source diameter, or frequency. The TIS generally underestimates (is less than) ΔTmax for f-numbers ⩽2, conditions for which ΔTmax⩽0.30°C and TIS⩽0.40. This suggests that, for transmit f-numbers ⩽2, TIS would not need to be displayed according to the ODS display requirements. With the exception of the longer-focus, larger-diameter, higher-frequency sources, TIS generally tracks ΔTmax for f-numbers ⩾3. These exceptions suggest a breakdown of the ODS procedures far calculating TIS. |
| Title |
Evaluation of tumor cell death response in locally-advanced breast cancer patients to chemotherapy treatment by scattering property estimates using ultrasound backscatter. |
| Author |
Sannachi L, Tadayyon H, Sadeghi-naini A, Falou O, Jahedmotlagh Z, Oelze ML, Czarnota GJ. |
| Journal |
POMA-ICA 2013 Montreal |
| Volume |
|
| Year |
2013 |
| Abstract |
Breast cancer tumor response to chemotherapy in twenty nine patients was examined using quantitative ultrasound techniques. Backscatter parameters, such as the average scatterer diameter (ASD) and average acoustic concentration (AAC), were estimated from regions-of-interest in tumors prior to treatment onset and at four times during neoadjuvant chemotherapy treatment (weeks 1, 4, 8 and prior to surgery). Gaussian and Anderson form factor models were used over an analysis bandwidth of 4.5 to 9 MHz to obtain ASD and AAC estimates. The Gaussian model
did not fit with the measured data as well as Anderson model. The AAC estimates yielded significant differences with therapy times in clinically treatment responded patients. Data indicated increases of 6.6 dB/cm in acoustic concentration obtained maximum at week 8 in treatment responding tumors. Non-responding tumors didn't show any significant difference in the parameters during treatment. This study demonstrates that the scattering parameters have the potential to being used in quantifying the changes in tumors during treatment noninvasively and distinguishing treatment responders and non-responders early after of treatment initiation. |
| Title |
Evaluation of unscanned-mode soft-tissue thermal index for rectangular sources and proposed new indices. |
| Author |
O'Brien WD Jr, Yang Y, Simpson DG. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
2004 |
| Abstract |
The monopole-source solution was used to calculate the three-dimensional complex acoustic pressure field for one-dimensional focused rectangular apertures in a medium having homogeneous acoustic and thermal properties. For each of six frequencies (1, 3, 5, 7, 9 and 12 MHz) and three focuses (f/1, f/2 and f/4), 33 rectangular aperture cases were investigated, for a total of 594 cases. For these focused field geometries, the three-dimensional temperature distribution was calculated using the bioheat transfer equation in homogeneous perfused media (attenuation = absorption: 0.3 dB/cm-MHz; perfusion length: 1.0 cm). For each of the 594 cases, the acoustic field was normalized to the derated spatial-peak temporal-average intensity (ISPTA.3) of 720 mW/cm2, the maximum value condition allowed based on the U.S. Food and Drug Administration (FDA) regulatory limit for most diagnostic ultrasound (US) equipment. Using the normalized acoustic field, the axial temperature increase profiles and the maximum temperature increases (ΔTmax) were determined for each case. Also, from the normalized acoustic field, the unscanned-mode soft-tissue thermal index (TIS) for the rectangular sources was determined according to the procedures of the Standard for Real-Time Display of Thermal and Mechanical Indices on Diagnostic Ultrasound Equipment, commonly called the output display standard, ODS. The ΔTmax:TIS ratio of the 594 cases yielded a mean value of 0.22, a median value of 0.16, a maximum value of 1.04 and a minimum value of 0.039. For all but one of the cases, TIS was greater than ΔTmax. Also, two new unscanned-mode soft-tissue thermal indices (denoted TISnew(1) and TISnew(2)) were proposed. For new model 1, the ΔTmax: TISnew(1) ratio yielded a mean value of 1.02, a median value of 1.01, a maximum value of 1.83 and a minimum value of 0.44. For new model 2, the ΔTmax: TISnew(2) ratio yielded a mean value of 1.04, a median value of 0.99, a maximum value of 2.31 and a minimum value of 0.34. Further, both new models fit more closely to ΔTmax than does the ODS-determined TIS and have the potential of being easier for manufacturers to implement because only the source power and frequency need to be measured. |
| Title |
Evidence for a non-thermal effect of ultrasound. |
| Author |
ter Haar GR, Stratford IJ. |
| Journal |
Br J Cancer Suppl |
| Volume |
|
| Year |
1982 |
| Abstract |
No abstract available. |
| Title |
Evidence for free radical production by ultrasonic cavitation in biological media. |
| Author |
Edmonds PD, Sancier KM. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1983 |
| Abstract |
The statement is often made that free radicals will be produced during the violent collapse of transient cavities in liquids, that may result from the passage of ultrasonic waves in the low megahertz frequency range. Evidence for such free radicals is mostly indirect. We have insonated some argon-saturated aqueous solutions of biological molecules (trypsin, Dulbecco's Minimum Essential Medium, fetal bovine serum, and human blood plasma) and whole human blood, all containing a spin trapping compound, at 1 MHz, continuous wave, 6.6 W/cm(^2) (SPTA) for 15 min at 4-8 degrees C. Electron spin resonance spectra of the samples were recorded 10 and 30 min. after cessation of insonation. The spectra included those of spin adducts formed with .OH and .H radicals, which were absent in the cases of the sham treated controls. Thus, we have demonstrated the formation of the highly reactive .OH and .H radicals in the insonated media, even in the presence of natural radical scavengers in the mammalian derived products. |
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