|
|
|
BRL Abstracts Database |
|
Your search for ultrasound produced 3296 results. Page 175 out of 330
| Title |
Medical uses of ultrasound. |
| Author |
Brockelsby CF. |
| Journal |
New Sci |
| Volume |
|
| Year |
1962 |
| Abstract |
After many years of research, ultrasound is now being successfully employed as a tool complementary to X-rays, in diagnosis and in brain surgery. Thus pregnant women can be examined more safely than with X-rays and, because of a special blocking effect of ultrsound, nerves can be singled out for treatment. |
| Title |
Method for estimating total attenuation from a spatial map of attenuation slope for quantitative ultrasound imaging. |
| Author |
Pawlicki AD, O'Brien WD Jr. |
| Journal |
Ultrason Imaging |
| Volume |
|
| Year |
2013 |
| Abstract |
Estimating total ultrasound attenuation from backscatter data is essential in the field of quantitative ultrasound (QUS) because of the need to compensate for attenuation when estimating the backscatter coefficient and QUS parameters. This work uses a reference phantom method of attenuation estimation to create a spatial map of attenuation slope (AS) from backscatter radio-frequency (RF) data of three phantoms and a rat mammary adenocarcinoma tumor (MAT). The attenuation maps show changes in attenuation between different regions of the phantoms and the MAT tumor. Analyses of the attenuation maps of the phantoms suggest that
the AS estimates are in good quantitative agreement with the known values for the phantoms. Furthermore, estimates of total attenuation from the attenuation maps are likewise in good quantitative agreement with known values. |
| Title |
Method for microbubble characterization using primary radiation force. |
| Author |
Vos HJ, Guidi F, Boni E. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
2007 |
| Abstract |
Medical ultrasound contrast agents (UCA) have evolved from straight image enhancers to pathophysiological markers and drug delivery vehicles. However, the exact dynamic behavior of the encapsulated bubbles composing UCA is still not entirely known. In this article, we propose to characterize full populations of UCA, by looking at the translational effects of ultrasound radiation force on each bubble in a diluted population. The setup involves a sensitive, fully programmable transmitter/receiver and two unconventional, real-time display modes. Such display modes are used to measure the displacements produced by irradiation at frequencies in the range 2-8 MHz and pressures between 150 kPa and 1.5 MPa. The behavior of individual bubbles freely moving in a water tank is clearly observed, and it is shown that it depends on the bubble physical dimensions as well as on the viscoelastic properties of the encapsulation. A new method also is distilled that estimates the viscoelastic properties of bubble encapsulation by fitting the experimental bubble velocities to values simulated by a numerical model based on the modified Herring equation and the Bjerknes force. The fit results are a shear modulus of 18 MPa and a viscosity of 0.23 Pas for a thermoplastic PVC-AN shell. Phospholipid shell elasticity and friction parameter of the experimental contrast agent are estimated as 0.8 N/m and 1 10-7 kg/s, respectively (shear modulus of 32 MPa and viscosity of 0.19 Pas, assuming 4- nm shell thickness). |
| Title |
Method of cavitation-suppressed exposure of cells and explant mouse embryos to clinical real-time and pulsed doppler ultrasound. |
| Author |
Madsen EL, Frank GR, Macdonald MC, Martin AO, Bouck NP, Iannaccone PM. |
| Journal |
J Ultrasound Med |
| Volume |
|
| Year |
1991 |
| Abstract |
An apparatus and procedure for well-controlled exposure of cells or explant mouse embryos to clinical real-time ultrasound are described. Cells or embryos to be exposed are suspended in media made sufficiently viscous through inclusion of methylcellulose that cavitation is suppressed but thermal effects remain negligible. During exposure, the scanning beam is precisely centered in a 2 mm x 20 mm slot in a 20 cm diameter agar disc containing the suspension. The high viscosity causes the cells to remain distributed uniformly throughout the exposure; this fact, along with precision beam alignment, ensures that exposure is well defined. Exposure data are acquired with a 0.6 mm diameter hydrophone. |
| Title |
Method of improved scatterer size estimation and application to parametric imaging using ultrasound. |
| Author |
Oelze ML, O'Brien WD Jr. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
2002 |
| Abstract |
The frequency dependence of RF signals backscattered from random media (tissues) has been used to describe the microstructure of the media. The frequency dependence of the backscattered RF signal is seen in the power spectrum. Estimates of scatterer properties (average scatterer size) from an interrogated medium are made by minimizing the average squared deviation (MASD) between the measured power spectrum and a theoretical power spectrum over an analysis bandwidth. Estimates of the scatterer properties become increasingly inaccurate as the average signal to noise ratio (SNR) over the analysis bandwidth becomes smaller. Some frequency components in the analysis bandwidth of the measured power spectrum will have smaller SNR than other frequency components. The accuracy of estimates can be improved by weighting the frequency components that have the smallest SNR less than the frequencies with the largest SNR in the MASD. A weighting function is devised that minimizes the noise effects on the estimates of the average scatterer sizes. Simulations and phantom experiments are conducted that show the weighting function gives improved estimates in an attenuating medium. The weighting function is applied to parametric images using scatterer size estimates of a rat that had developed a spontaneous mammary tumor. |
| Title |
Methods for estimation of statistical properties of envelopes of ultrasonic echoes from myocardium. |
| Author |
Wear KA, Popp RL. |
| Journal |
IEEE Trans Med Imaging |
| Volume |
|
| Year |
1987 |
| Abstract |
Several investigators have characterized various forms of heart disease from the statistical properties of envelopes of ultrasonic echoes from myocardium. In particular, the mean-to-standard deviation ratio (MSR), skewness, and kurtosis of the envelope probability density function have been used for the detection of myocardial ischemia, infarction, reperfusion, and hypertrophy. In this paper, the effects of phenomena other than tissue acoustic properties upon estimates of statistical parameters are investigated. These include system characteristics (center frequency, bandwidth, beam width, etc.), sample volume dimensions, and tissue velocity. In myocardium, relatively small amounts of tissue are available for interrogation. It is shown that, under these limited data acquisition conditions, substantial systemic biases in the estimates of statistical parameters may occur. Analytic forms for errors in the envelope variance estimate are derived. Estimation of the envelope mean, variance, MSR, skewness, and kurtosis is investigated experimentally, using a commercial medical ultrasound scanner and a tissue-mimicking phantom. |
| Title |
Methods for measuring ultrasonic backscatter and attenuation coefficients for tissues and tissue-like media. |
| Author |
Insana MF. |
| Journal |
Thesis(PhD): Univ of Wisconsin-Madison |
| Volume |
|
| Year |
1983 |
| Abstract |
Measurements of fundamental acoustic properties of biological tissues, in vivo, may provide information useful for improving the diagnostic value and image quality of ultrasound scanning. Also, in the clinical environment, such measurements may be useful for characterizing the pathological state of many soft tissues.
In this dissertation, a new method for measuring ultrasonic backscatter coefficients is described. An important aspect of this method is that an exact representation of the transducer pressure field has been included in the analysis of echo signal data. Measurements employing this analysis for a sample consisting of a well defined system of scatterers were found to agree with theoretical values calculated from first principles. The influence on measurement accuracy of parameters such as sample gate duration, incident pulse bandwidth, and attenuation of the transducer beam along the transmission path have been investigated using ultrasonically tissue-mimicking (TM ) materials. TM phantoms were constructed to simulate various aspects of in vivo measurements, particularly the effects of fat-to-nonfat interfaces, for assessing the feasibility of applying this analysis, in vivo. Uncertainties in attenuation estimates were found to significantly reduce the accuracy for measuring backscatter coefficients.
The interdependence between attenuation and backscatter values has led to the investigation of a method for estimating attenuation coefficients, in vivo. A spectral technique for measuring attenuation, which includes diffraction effects, was tested for accuracy using tissue-mimicking phantoms having known acoustic properties. Results of attenuation measured for normal human liver, in vivo, are presented.
|
| Title |
Methods of measuring the absolute intensity of ultrasonic waves in liquids and solids. |
| Author |
Mikhailov IG. |
| Journal |
Ultrasonics |
| Volume |
|
| Year |
1964 |
| Abstract |
Methods of comparing the intensities of sources of ultrasound in liquids are liable to large errors: methods of absolute measurement are rare. The method given here is an absolute calorimetric one in which the calorimeter is calibrated electrically. It is followed by a detailed description of a method of measuring ultrasonic intensity in solids. Calibration curves for both methods are given and the importance of confining the experiment in the solid to the region of even field distribution is stressed. The results are supported by theory. |
| Title |
Micelles and nanoparticles for ultrasonic drug and gene delivery. |
| Author |
Husseini GA, Pitt WG. |
| Journal |
Adv Drug Deliv Rev |
| Volume |
|
| Year |
2008 |
| Abstract |
Drug delivery research employing micelles and nanoparticles has expanded in recent years. Of particular interest is the use of these nanovehicles that deliver high concentrations of cytotoxic drugs to diseased tissues selectively, thus reducing the agent's side effects on the rest of the body. Ultrasound, traditionally used in diagnostic medicine, is finding a place in drug delivery in connection with these nanoparticles. In addition to their non-invasive nature and the fact that they can be focused on targeted tissues, acoustic waves have been credited with releasing pharmacological agents from nanocarriers, as well as rendering cell membranes more permeable. In this article, we summarize new technologies that combine the use of nanoparticles with acoustic power both in drug and gene delivery. Ultrasonic drug delivery from micelles usually employs polyether block copolymers and has been found effective in vivo for treating tumors. Ultrasound releases drug from micelles, most probably via shear stress and shock waves from the collapse of cavitation bubbles. Liquid emulsions and solid nanoparticles are used with ultrasound to deliver genes in vitro and in vivo. The small packaging allows nanoparticles to extravasate into tumor tissues. Ultrasonic drug and gene delivery from nanocarriers has tremendous potential because of the wide variety of drugs and genes that could be delivered to targeted tissues by fairly non-invasive means. |
| Title |
Microbubble administration accelerates clot lysis during continuous 2-MHz ultrasound monitoring in stroke patients treated with intravenous tissue plasminogen activator. |
| Author |
Molina CA, Ribo M, Rubiera M, Montaner J, Santamarina E, Delgado-Mederos R, Arenillas JF, Huertas R, Purroy F, Delgado P, Alvarez-Sabin J. |
| Journal |
Stroke |
| Volume |
|
| Year |
2006 |
| Abstract |
BACKGROUND AND PURPOSE: We sought to evaluate the effects of administration of microbubbles (MBs) on the beginning, speed, and degree of middle cerebral artery (MCA) recanalization during systemic thrombolysis and continuous 2-MHz pulsed-wave transcranial Doppler (TCD) monitoring. METHODS: We evaluated 111 patients with acute stroke attributable to MCA occlusion treated with intravenous tissue plasminogen activator (tPA). Thirty-eight patients were treated with tPA plus continuous 2-hour TCD monitoring plus 3 doses of 2.5 g (400 mg/mL) of galactose-based MBs given at 2, 20, and 40 minutes after tPA bolus (MB group). These patients were compared with 73 patients who were allocated to receive tPA plus continuous 2-hour TCD ultrasound (US) monitoring (tPA/US group) or tPA plus placebo monitoring (tPA group), most of whom were enrolled in a previous study of US-enhanced thrombolysis. The beginning, degree, and time to maximum completeness of recanalization during the first 2 hours of tPA bolus were recorded. RESULTS: Median prebolus National Institutes of Health Stroke Scale (NIHSS) score was 18. Eighty patients (72%) had a proximal and 31 (28%) a distal MCA occlusion on TCD. Thirty-seven patients (33%) received tPA/US, 38 (34%) received tPA/US/MB, and 36 (32%) were treated with tPA alone. Stroke severity, time to treatment, location of MCA occlusion, and presence of carotid artery disease were similar among groups. Two-hour recanalization was seen in 14 (39%), 25 (68%), and 27 patients (71%) in the tPA, tPA/US, and tPA/US/MB groups, respectively (P=0.004). Two-hour complete recanalization rate was significantly (P=0.038) higher in the tPA/US/MB group (54.5%) compared with tPA/US (40.8%) and tPA (23.9%) groups. The time to beginning of recanalization after tPA bolus was 26+/-18 minutes in the tPA/US group and 19+/-12 minutes in the tPA/US/MB group (P=0.12). Four patients (3.6%) experienced symptomatic intracranial hemorrhage: 2 (5.5%), 1 (2.7%), and 1 patient (2.6%) who received tPA only, tPA/US, and tPA/US/MB, respectively, experienced symptomatic intracranial hemorrhage. At 24 hours, 31%, 41%, and 55% of tPA, tPA/US, and tPA/US/MB improved >4 points in the NIHSS score. CONCLUSIONS: Administration of MBs induces further acceleration of US-enhanced thrombolysis in acute stroke, leading to a more complete recanalization and to a trend toward better short- and long-term outcome.
|
Page 1
| 2
| 3
| 4
| 5
| 6
| 7
| 8
| 9
| 10
| 11
| 12
| 13
| 14
| 15
| 16
| 17
| 18
| 19
| 20
| 21
| 22
| 23
| 24
| 25
| 26
| 27
| 28
| 29
| 30
| 31
| 32
| 33
| 34
| 35
| 36
| 37
| 38
| 39
| 40
| 41
| 42
| 43
| 44
| 45
| 46
| 47
| 48
| 49
| 50
| 51
| 52
| 53
| 54
| 55
| 56
| 57
| 58
| 59
| 60
| 61
| 62
| 63
| 64
| 65
| 66
| 67
| 68
| 69
| 70
| 71
| 72
| 73
| 74
| 75
| 76
| 77
| 78
| 79
| 80
| 81
| 82
| 83
| 84
| 85
| 86
| 87
| 88
| 89
| 90
| 91
| 92
| 93
| 94
| 95
| 96
| 97
| 98
| 99
| 100
| 101
| 102
| 103
| 104
| 105
| 106
| 107
| 108
| 109
| 110
| 111
| 112
| 113
| 114
| 115
| 116
| 117
| 118
| 119
| 120
| 121
| 122
| 123
| 124
| 125
| 126
| 127
| 128
| 129
| 130
| 131
| 132
| 133
| 134
| 135
| 136
| 137
| 138
| 139
| 140
| 141
| 142
| 143
| 144
| 145
| 146
| 147
| 148
| 149
| 150
| 151
| 152
| 153
| 154
| 155
| 156
| 157
| 158
| 159
| 160
| 161
| 162
| 163
| 164
| 165
| 166
| 167
| 168
| 169
| 170
| 171
| 172
| 173
| 174
| 175
| 176
| 177
| 178
| 179
| 180
| 181
| 182
| 183
| 184
| 185
| 186
| 187
| 188
| 189
| 190
| 191
| 192
| 193
| 194
| 195
| 196
| 197
| 198
| 199
| 200
| 201
| 202
| 203
| 204
| 205
| 206
| 207
| 208
| 209
| 210
| 211
| 212
| 213
| 214
| 215
| 216
| 217
| 218
| 219
| 220
| 221
| 222
| 223
| 224
| 225
| 226
| 227
| 228
| 229
| 230
| 231
| 232
| 233
| 234
| 235
| 236
| 237
| 238
| 239
| 240
| 241
| 242
| 243
| 244
| 245
| 246
| 247
| 248
| 249
| 250
| 251
| 252
| 253
| 254
| 255
| 256
| 257
| 258
| 259
| 260
| 261
| 262
| 263
| 264
| 265
| 266
| 267
| 268
| 269
| 270
| 271
| 272
| 273
| 274
| 275
| 276
| 277
| 278
| 279
| 280
| 281
| 282
| 283
| 284
| 285
| 286
| 287
| 288
| 289
| 290
| 291
| 292
| 293
| 294
| 295
| 296
| 297
| 298
| 299
| 300
| 301
| 302
| 303
| 304
| 305
| 306
| 307
| 308
| 309
| 310
| 311
| 312
| 313
| 314
| 315
| 316
| 317
| 318
| 319
| 320
| 321
| 322
| 323
| 324
| 325
| 326
| 327
| 328
| 329
| 330
|
|
|
|
