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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 226 out of 330
| Title |
Sensitive detection of the effects of reperfusion on myocardium by ultrasonic tissue characterization with integrated backscatter. |
| Author |
Wickline SA, Thomas LJ III, Miller JG, Sobel BE, Perez JE. |
| Journal |
Circulation |
| Volume |
|
| Year |
1986 |
| Abstract |
We have shown recently that tissue characterization of myocardium with ultrasound reflects changes associated with contractile function throughout the cardiac cycle. To determine whether ultrasonic tissue characterization can sensitively detect the impact of ischemic injury and reperfusion on contractile properties of the heart, we studied the time course of change of backscatter after 5, 20, and 60 min of coronary occlusion followed by reperfusion in 15 dogs. The time-averaged integrated backscatter (IB) and the amplitude and phase of cyclic variation of IB (phase relative to the left ventricular pressure waveform) were measured. A novel ultrasonic index of acute injury was identified, the phase-weighted amplitude of cyclic variation, and calculated by weighting the amplitude of cyclic variation of IB with respect to the phase. We hypothesized that backscatter variables would change dramatically after occlusion and that their restitution after reperfusion would sensitively reflect the extent and time course of reversibility of ischemic injury. After coronary occlusion, segmental wall thickening decreased from approximately 55% to 5% regardless of the duration of ischemia. Changes in backscatter associated with this decrease included an increase in time-averaged IB of approximately 5 dB, a 5 dB decrease in cyclic variation, an 80 degree phase shift, and a 7 dB decrease in phase-weighted amplitude. Wall thickening after reperfusion immediately after the 5, 20, or 60 min occlusions recovered to 45%, 27%, and 12% of baseline values, respectively. Within 3 hr it recovered to 53%, 44%, and 22%. Time-averaged IB recovered initially by 89%, 61%, and 44% (all p less than .05) and continued to recover subsequently although more slowly. Ultimate recovery was virtually complete. In contrast to the rapid recovery of time-averaged IB, phase-weighted amplitude recovered initially to only 72%, 41%, and -7% of baseline (all p less than .05) and manifested slower and incomplete recovery when ischemia had been present for 20 or 60 min. After reperfusion, the time course of both cyclic variation and phase were reflected by changes in the phase-weighted amplitude. The backscatter variables assessed appear to sensitively delineate the duration, time course of recovery, and reversibility of ischemic injury in response to reperfusion. The results suggest that early recovery of time-averaged IB corresponds in part to the restoration of tissue ultrastructural integrity. |
| Title |
Sensitive tests for bio-effects of ultrasound. |
| Author |
Nyborg Wl, Miller DL, Whitcomb CC. |
| Journal |
Reflections |
| Volume |
|
| Year |
1978 |
| Abstract |
No abstract available. |
| Title |
Sensitivity and specificity of multimodal and ultrasound screening for ovarian cancer, and stage distribution of detected cancers. |
| Author |
Menon U, Gentry-Maharaj A, Hallett R, Ryan A, Burnell M, Sharma A, Lewis S, Davies S, Philpott S, Lopes A, Godfrey K, Oram D, Herod J, Williamson K, Seif MW, Scott I, Mould T, Woolas R, Murdoch J. |
| Journal |
Lancet Oncol |
| Volume |
|
| Year |
2009 |
| Abstract |
BACKGROUND:
Ovarian cancer has a high case-fatality ratio, with most women not diagnosed until the disease is in its advanced stages. The United Kingdom Collaborative Trial of Ovarian Cancer Screening (UKCTOCS) is a randomised controlled trial designed to assess the effect of screening on mortality. This report summarises the outcome of the prevalence (initial) screen in UKCTOCS.
METHODS:
Between 2001 and 2005, a total of 202 638 post-menopausal women aged 50-74 years were randomly assigned to no treatment (control; n=101 359); annual CA125 screening (interpreted using a risk of ovarian cancer algorithm) with transvaginal ultrasound scan as a second-line test (multimodal screening [MMS]; n=50 640); or annual screening with transvaginal ultrasound (USS; n=50 639) alone in a 2:1:1 ratio using a computer-generated random number algorithm. All women provided a blood sample at recruitment. Women randomised to the MMS group had their blood tested for CA125 and those randomised to the USS group were sent an appointment to attend for a transvaginal scan. Women with abnormal screens had repeat tests. Women with persistent abnormality on repeat screens underwent clinical evaluation and, where appropriate, surgery. This trial is registered as ISRCTN22488978 and with ClinicalTrials.gov, number NCT00058032.
FINDINGS:
In the prevalence screen, 50 078 (98.9%) women underwent MMS, and 48 230 (95.2%) underwent USS. The main reasons for withdrawal were death (two MMS, 28 USS), non-ovarian cancer or other disease (none MMS, 66 USS), removal of ovaries (five MMS, 29 USS), relocation (none MMS, 39 USS), failure to attend three appointments for the screen (72 MMS, 757 USS), and participant changing their mind (483 MMS, 1490 USS). Overall, 4355 of 50 078 (8.7%) women in the MMS group and 5779 of 48 230 (12.0%) women in the USS group required a repeat test, and 167 (0.3%) women in the MMS group and 1894 (3.9%) women in the USS group required clinical evaluation. 97 of 50 078 (0.2%) women from the MMS group and 845 of 48 230 (1.8%) from the USS group underwent surgery. 42 (MMS) and 45 (USS) primary ovarian and tubal cancers were detected, including 28 borderline tumours (eight MMS, 20 USS). 28 (16 MMS, 12 USS) of 58 (48.3%; 95% CI 35.0-61.8) of the invasive cancers were stage I/II, with no difference (p=0.396) in stage distribution between the groups. A further 13 (five MMS, eight USS) women developed primary ovarian cancer during the year after the screen. The sensitivity, specificity, and positive-predictive values for all primary ovarian and tubal cancers were 89.4%, 99.8%, and 43.3% for MMS, and 84.9%, 98.2%, and 5.3% for USS, respectively. For primary invasive epithelial ovarian and tubal cancers, the sensitivity, specificity, and positive-predictive values were 89.5%, 99.8%, and 35.1% for MMS, and 75.0%, 98.2%, and 2.8% for USS, respectively. There was a significant difference in specificity (p<0.0001) but not sensitivity between the two screening groups for both primary ovarian and tubal cancers as well as primary epithelial invasive ovarian and tubal cancers.
INTERPRETATION:
The sensitivity of the MMS and USS screening strategies is encouraging. Specificity was higher in the MMS than in the USS group, resulting in lower rates of repeat testing and surgery. This in part reflects the high prevalence of benign adnexal abnormalities and the more frequent detection of borderline tumours in the USS group. The prevalence screen has established that the screening strategies are feasible. The results of ongoing screening are awaited so that the effect of screening on mortality can be determined. |
| Title |
Sensitivity and specificity of multimodal and ultrasound screening for ovarian cancer, and stage distribution of detected cancers. |
| Author |
Menon U, Gentry-Maharaj A, Hallett R, Ryan A, Burnell M, Sharma A, Lewis S, Davies S, Philpott S, Lopes A, Godfrey K, Oram D, Herod J, Williamson K, Seif MW, Scott I, Mould T, Woolas R, Murdoch J. |
| Journal |
Lancet Oncol |
| Volume |
|
| Year |
2009 |
| Abstract |
BACKGROUND:
Ovarian cancer has a high case-fatality ratio, with most women not diagnosed until the disease is in its advanced stages. The United Kingdom Collaborative Trial of Ovarian Cancer Screening (UKCTOCS) is a randomised controlled trial designed to assess the effect of screening on mortality. This report summarises the outcome of the prevalence (initial) screen in UKCTOCS.
METHODS:
Between 2001 and 2005, a total of 202 638 post-menopausal women aged 50-74 years were randomly assigned to no treatment (control; n=101 359); annual CA125 screening (interpreted using a risk of ovarian cancer algorithm) with transvaginal ultrasound scan as a second-line test (multimodal screening [MMS]; n=50 640); or annual screening with transvaginal ultrasound (USS; n=50 639) alone in a 2:1:1 ratio using a computer-generated random number algorithm. All women provided a blood sample at recruitment. Women randomised to the MMS group had their blood tested for CA125 and those randomised to the USS group were sent an appointment to attend for a transvaginal scan. Women with abnormal screens had repeat tests. Women with persistent abnormality on repeat screens underwent clinical evaluation and, where appropriate, surgery. This trial is registered as ISRCTN22488978 and with ClinicalTrials.gov, number NCT00058032.
FINDINGS:
In the prevalence screen, 50 078 (98.9%) women underwent MMS, and 48 230 (95.2%) underwent USS. The main reasons for withdrawal were death (two MMS, 28 USS), non-ovarian cancer or other disease (none MMS, 66 USS), removal of ovaries (five MMS, 29 USS), relocation (none MMS, 39 USS), failure to attend three appointments for the screen (72 MMS, 757 USS), and participant changing their mind (483 MMS, 1490 USS). Overall, 4355 of 50 078 (8.7%) women in the MMS group and 5779 of 48 230 (12.0%) women in the USS group required a repeat test, and 167 (0.3%) women in the MMS group and 1894 (3.9%) women in the USS group required clinical evaluation. 97 of 50 078 (0.2%) women from the MMS group and 845 of 48 230 (1.8%) from the USS group underwent surgery. 42 (MMS) and 45 (USS) primary ovarian and tubal cancers were detected, including 28 borderline tumours (eight MMS, 20 USS). 28 (16 MMS, 12 USS) of 58 (48.3%; 95% CI 35.0-61.8) of the invasive cancers were stage I/II, with no difference (p=0.396) in stage distribution between the groups. A further 13 (five MMS, eight USS) women developed primary ovarian cancer during the year after the screen. The sensitivity, specificity, and positive-predictive values for all primary ovarian and tubal cancers were 89.4%, 99.8%, and 43.3% for MMS, and 84.9%, 98.2%, and 5.3% for USS, respectively. For primary invasive epithelial ovarian and tubal cancers, the sensitivity, specificity, and positive-predictive values were 89.5%, 99.8%, and 35.1% for MMS, and 75.0%, 98.2%, and 2.8% for USS, respectively. There was a significant difference in specificity (p<0.0001) but not sensitivity between the two screening groups for both primary ovarian and tubal cancers as well as primary epithelial invasive ovarian and tubal cancers.
INTERPRETATION:
The sensitivity of the MMS and USS screening strategies is encouraging. Specificity was higher in the MMS than in the USS group, resulting in lower rates of repeat testing and surgery. This in part reflects the high prevalence of benign adnexal abnormalities and the more frequent detection of borderline tumours in the USS group. The prevalence screen has established that the screening strategies are feasible. The results of ongoing screening are awaited so that the effect of screening on mortality can be determined. |
| Title |
Sensitivity considerations for PVDF hydrophones using the spot-poled membrane design. |
| Author |
Harris GR. |
| Journal |
IEEE Trans Sonics Ultrason |
| Volume |
|
| Year |
1982 |
| Abstract |
The receiving sensitivities of piezoelectric polymer polyvinylidene fluoride (PVDF) hydrophones constructed using the spot-poled membrane design are studied. Formation of deposited leads and the effect of different lead geometries on sensitivity are discussed, and a comparison between voltage and charge amplification techniques is made. Sensitivity variations of within +/- 1 dB from 1-10 MHz were achievable for hydrophones having active element diameters of from 0.3-1.0 mm. Depending on the element size and amplifier type and configuration, the sensitivities ranged from approximately -234 to -268 dB re IV/microPa. In addition, equivalent noise pressure levels (1-Hz band) of from 109-131 dB re 1 microPa were measured. The resulting signal-to-noise (S/N) ratios for these probes were found to be within the limits specified by the American Institute of Ultrasound in Medicine and National Electrical Manufacturers Association for hydrophone measurements of pulse-echo diagnostic devices. |
| Title |
Sensitivity measurements of piezoelectric polymer hydrophones from 0.2-2 MHz using a broadband-pulse technique. |
| Author |
Harris GR, Gammell PM. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1999 |
| Abstract |
It is widely recognized that the sensitivity of hydrophones used to measure medical diagnostic ultrasound fields should be uniform over several octaves above the center frequency (i.e., above the mean of the upper and lower -3 dB frequencies in the transmitted acoustic-pressure spectrum). However, a bandwidth extending to at least ten times below the diagnostic pulse-center frequency is needed for accurate (error = 5%) measurements of the peak rarefactional pressure. Since at present it is not common for manufacturers of medical-use hydrophones to provide sensitivity information below 1-2 MHz, a study was undertaken to determine these low-frequency sensitivities. The technique uses broadband, plane-wave pressure pulses generated by electrical short-pulse excitation of a thick piezoelectric ceramic disk. The hydrophone response is calculated from measurements of the source transducer and hydrophone-voltage waveforms. The frequency responses of both needle-type and spot-poled membrane polymer hydrophones were measured using this technique. The spot-poled membrane hydrophones had -3-dB bandwidths extending below 0.2 MHz, the lower limit for the calibration technique. The needle-type hydrophones studied, however, all exhibited a response roll-off of greater than 3 dB in the frequency range studied. Therefore, given the above bandwidth criterion as a function of diagnostic pulse-center frequency, the sensitivity to at least 0.2 MHz should be established for diagnostic-use hydrophones, because a uniform response below 1 MHz cannot be assumed. |
| Title |
Sequential changes in rat femoral artery blood flow and tissue degeneration after exposure to high-intensity focused ultrasound. |
| Author |
Ishikawa T,Okai T,Sasaki K,Umemura S,Miyazaki N,Kushima M,Aoki H,Ichihara M,Ichizuka K. |
| Journal |
J Med Ultrasonics |
| Volume |
|
| Year |
2008 |
| Abstract |
Purpose. The purpose of this study was to investigate the sequential changes in rat artery blood flow and tissue degeneration after exposure to high-intensity focused ultrasound (HIFU) in vivo.
Methods. HIFU was applied through the skin to the femoral artery of Sprague-Dawley rats. The peak intensities used were 530, 1080, 2750, and 4300 W/cm2. After exposure, we measured the peak systolic velocity (PSV) in the artery every 1 min until the velocity stabilized. The vessel was resected and examined histologically 7 days after exposure.
Results. PSV was not significantly affected by HIFU exposure at 530 W/cm2. PSV increased immediately after HIFU exposure at intensities of 1080 and 2750 W/cm2. PSV after HIFU exposure at 1080 W/cm2 fell to the control level within minutes; however, PSV increased immediately after HIFU exposure at 2750 W/cm2 and then decreased slowly but remained at a higher level than the control for 15 min. On HIFU exposure at 4300 W/cm2, the target artery was completely occluded. Histological studies 7 days after HIFU exposure demonstrated that exposure at 530 and 1080 W/cm2 induced vacuolar degeneration in the tunica media of the femoral artery in rats; exposure to HIFU at 2750 and 4300 W/cm2 resulted in strong necrotic degeneration in the tunica media. These histological changes were more marked than those found immediately after HIFU exposure. Organized thrombus formation was observed only for HIFU exposure at 4300 W/cm2.
Conclusion. Sequential changes in arterial blood flow after HIFU exposure vary with the intensity, and the histological changes in arterial tissue progress over time. These phenomena should be considered when HIFU is clinically applied to achieve arterial occlusion.
Keywords high-intensity focused ultrasound (HIFU) - sequential changes in blood flow - functional vascular contraction - flow occlusion - histological change |
| Title |
Session 5: Parameters for bioeffects experiments. |
| Author |
Barnett SB. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1989 |
| Abstract |
No abstract available. |
| Title |
Severing the corpus callosum in rats using ultrasound: Theoretical and experimental correlations. |
| Author |
Lee AJ, Taberner PV. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1979 |
| Abstract |
A single, focused, ultrasound beam of 3.5 W total acoustic output for 2 s at 3.3 MHz was used to create a series of overlapping lesions to sever the corpus callosum of the rat on the midline. A theoretical and experimental determination of the ultrasound field is described and histological evidence of the lesions is provided. Good correlation occurred between the theoretical and experimental results only for the intensity contour lines examined. The experimentally derived focal intensity of 162 W cm–2 (at 25 °C) was 24% of the intensity predicted from theoretical calculations. A difference of 2 mm was found for the axial position of maximal intensity, thermocouple plotting showing the focal region to be nearer the transducer than expected from the theory. Histological results indicated that, under certain conditions, from a single dose of ultrasound two lesions could be obtained corresponding to both the theoretically and experimentally derived locations. At lower intensities it was possible to ulitize the upper location to sever the corpus callosum, the lower intensity site then being subthreshold for the rat brain. The trackless localized damage caused by ultrasound makes this method of obtaining split-brain rats suitable for behavioral and biochemical studies, where any nonspecific damage may have undesirable effects. |
| Title |
Shadowing and enhancement in ultrasonic echograms by reflection and refraction. |
| Author |
Robinson DE, Wilson LS, Kossoff G. |
| Journal |
J Clin Ultrasound |
| Volume |
|
| Year |
1981 |
| Abstract |
The action of reflection and refraction in producing shadows and enhancement in ultrasonic echograms behind cystic structures is well known, but the physical explanations usually used are incomplete. In this paper the emergent beam patterns for a number of cases are plotted and this data used to explain the shadows and enhancement observed. Cases are also illustrated of echoes displayed incorrectly within the shadow region and of reflectors within the shadow region displayed elsewhere. The use of the echographic appearances to assess the velocity of propagation in cystic structures is described. |
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