|
|
|
BRL Abstracts Database |
|
Your search for ultrasound produced 3296 results. Page 290 out of 330
| Title |
Ultrasonic equipment for application of ultrasound with high effect to animals used for experiments. |
| Author |
Bang J, Northeved A. |
| Journal |
Acta Pathol Microbiol Scand |
| Volume |
|
| Year |
1970 |
| Abstract |
In the light of the increasing application of ultrasonics for diagnostic purposes, it seems reasonable, in order to obtain a qualitative and quantitative evaluation, to investigate the teratogenic effects, if any, of ultrasound with frequencies equalling those applied for diagnostic purposes in comprehensive animal experiments. The object of the present study is to define the construction of an apparatus and the development of a methodology by which to demonstrate harmful effect, if any, involved in the application of continuous 2.25 MHz ultrasound to experimental animals and their products of conception. Furthermore the present study is to define a method for determination of level of action in the uterus of experimental animals. |
| Title |
Ultrasonic estimation of tissue perfusion: A stochastic approach. |
| Author |
Adler RS, Rubin JM, Fowlkes JB, Carson PL, Pallister JE. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1995 |
| Abstract |
Imaging of blood flow perfusion is an area of significant medical interest. Recently, the advantages of using the total integrated Doppler power spectrum as the parameter that is encoded in color has been shown to result in an approximately threefold increase in flow sensitivity, a relative insensitivity to acquisition angle and lack of aliasing. We have taken this mode a step further and demonstrated the potential for quantifying blood flow using correlation-based algorithms applied to the power signal. We show that phi(tau) = phi(0)e-(^VT), where phi(tau) is the two-time correlation of the fluctuation in the power signal, and v is the specific flow (reciprocal of mean transit time). Scans of a dog's blood, pumped at a constant rate through gum rubber tubing, were obtained using a Diasonics Spectra 10-MHz linear array transducer at standard range-gated spectral mode (PRF = 1400 Hz, wall filter = 50 Hz, sample gate = 1.5 mm). A fixed Doppler angle of 68 degrees was used. Five different flow rates were tested, and the velocities determined by power decorrelation were compared to the mean velocities calculated from the Doppler shifts by linear regression (R(^2) = 0.987). We believe the results are very encouraging for using power decorrelation in perfusion evaluation. |
| Title |
Ultrasonic examination of proton-transfer reactions in aqueous solutions of glycine. |
| Author |
Hussey M, Edmonds PD. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1971 |
| Abstract |
Proton transfer at side-chain groups has been proposed as a possible molecular mechanism for the absorption of ultrasound in aqueous protein and polypeptide solutions. This study constitutes part of an evaluation of this mechanism. It is possible to begin the evaluation because this reaction also occurs in simple model compounds which can be analyzed ultrasonically. Glycine is a model compound which provides an instance of each of the two most relevant protontransfer mechanisms-addition of the hydroxl ion to the positively charged amino group and addition of the hydrogen ion to the negatively charged carboxyl group. Each of these reactions is examined in detail in this work. |
| Title |
Ultrasonic exposure in static and real time echography. |
| Author |
Barnett SB, Kossoff G. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1982 |
| Abstract |
Measurement of ultrasonic output from static and real time devices has shown both types of equipment to emit approximately the same amount of energy per pulse and the same peak instantaneous intensity. The major differences in exposure were related to the amount of energy used to produce an image, the total amount of energy used to perform an examination, and the amount of energy passing through a single point in tissue. the highest single point exposure occurred during static M-mode examinations when an energy exposure of 120 mJ per minute was measured. By comparison a real time B-mode examination resulted in a single point exposure of 0.018 mJ/echogram or 27 mJ/min. The single point exposure per echogram in a static examination was 0.12 mJ for a simple scan and 1.15 mJ for a compound scan with contact equipment, and 0.01 and 0.08 mJ for simple and compound scans using water path equipment. |
| Title |
Ultrasonic exposure modifies platelet morphology and function in vitro. |
| Author |
Williams AR, Sykes SM, O'Brien WD Jr. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1977 |
| Abstract |
Samples of human platelet rich plasma (PRP) exposed to 1 MHz ultrasonic irradiation contained more cellular debris than their controls, indicating that a small population of the cells had been disrupted, possibly by some form of cavitation-like activity. The surviving cells appeared undamaged under the electron microscope and functioned as well as their controls in forming a platelet thrombus when tested immediately after the ultrasonic exposure but not after a 30 min incubation at 22 C. Parallel studies showed that incubation of control platelets with substances released from damaged or disrupted platelets could mimic the changes seen in incubated samples which had previously been exposed to ultrasound. |
| Title |
Ultrasonic exposure thresholds for changes in cells and tissues. |
| Author |
Hill CR. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1972 |
| Abstract |
The first part of this paper reports an experimental investigation of some parameters that control the occurrence of biologically effective cavitation‐type phenomena in the frequency region 0.25 4 MHz. The experimental criterion by which “cavitation” is recognized here is the simultaneous occurrence of degradation of DNA in aqueous solution, liberation of free I2 from KI solution, and generation of half‐order subharmonic. The intensity threshold for cavitation rises with frequency from 0.14 to 17.5 W cm−2 (spatial peak) in the above frequency range. Pulse duration and duty factor are also found to be determining parameters, with cavitation activity reducing to zero when values of both parameters are sufficiently low. A strong positive correlation between ambient pressure and intensity threshold has also been determined. On the basis of observations of the levels of scattered half‐order subharmonic signals from various media, no evidence could be found for cavitation activity in sonicated mammalian tissues, although such activity could be detected in a wide range of liquids. The second part of the paper consists of a review, conducted in the light of the above results, of published experimental data relating to the existence and values of exposure thresholds for possible nonthermal, noncavitational mechanisms of action of ultrasound in living cells and tissues. |
| Title |
Ultrasonic flaw detection of transient inhomogeneities induced by intense focused ultrasound in a plastic block. |
| Author |
Okuyama D, Fry WJ, Fry FJ, Leichner GH, Kelly E. |
| Journal |
Jpn Soc Med Ultrason |
| Volume |
|
| Year |
1967 |
| Abstract |
W. J. Fry, one of the present authors previously proposed the application of an ultrasonic pulse of appropriate energy content (at a level that would not injure tissue) to a region of soft tissue during in vivo ultrasonic visualization in order to provide a sharp gradient in the acousitic impedance at tissue boundaries where ordinarily ultrasonic echoes are produced that are too weak to detect so that it is temporarily easy to detect echoes from such an interface when examining pulses are incident on it. He also experimentally demonstrated this effect. This was demonstrated by producing inhomogeneities in the focal region of an irradiator by an ultrasonic pulse of appropriate energy content in material with "heat reversible" characteristics. In such experiments it was observed that the inhomogeneity produced distinct acoustic reflections when detected by another ultrasonic beam, but the phenomenon disappears in a specific time interval following cessation of the heating beam. |
| Title |
Ultrasonic gas body activation in Elodea leaves and the mechanical index. |
| Author |
Miller DL, Thomas RM. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1993 |
| Abstract |
Membrane damage resulting from ultrasonic gas body activation was investigated in leaves of the aquatic plant Elodea using pulse-mode exposures from 0.745-15 MHz. The frequency response was similar to that previously observed for continuous exposures. Cell death thresholds were higher for the pulse modes; for example, at 6 MHz the threshold was 166 W/cm2 spatial-peak, pulse-average (SPPA) intensity for 1 microsecond pulses and 1 kHz pulse repetition frequency (PRF) for 60 s exposures, compared to 12 W/cm2 for 60 ms continuous exposure. Increasing the PRF for 2.5 MHz, 3 microseconds pulses from 10 Hz to 5 kHz resulted in a gradual decrease in the threshold. Increasing the pulse duration from 1 microsecond to 30 microseconds and PRF from 33 Hz to 1 kHz only weakly influenced the threshold, for the constant 60 ms total on-time. Decreasing the pulse duration for single 6 MHz pulses increased the threshold up to 1,540 W/cm2 at 30 microseconds. The gas body activity was modeled with linear theory for oscillation of the gas channel walls, and intracellular shear stress, which causes lethal damage to the plasma membranes, was modeled with theory for acoustic microstreaming. Theory and observation indicate that the minimum shear stress threshold as a function of resonance frequency has essentially the same form as the Mechanical Index (MI) in the 0.5 to 20 MHz range. Specifically, for 3 microseconds pulses with 0.2-2 kHz PRF and 60 ms total on-time, the pressure-amplitude threshold divided by the square root of the frequency was approximately constant at 0.95 MPa/MHz1/2. |
| Title |
Ultrasonic gas-body activation in Drosophila. |
| Author |
Carstensen EL, Child SZ, Lam S, Miller DL, Nyborg WL. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1983 |
| Abstract |
The role of gas bodies in the interaction of Drosophila eggs and larvae with ultrasonic fields has been studied (1) by direct microscopic examination, (2) by observation of gas body activation during sonation with a special microscope, (3) by direct measurement of the volume fraction of gas in eggs and (4) through.the absorption of ultrasound. All approaches provide support for the postulate that these organisms contain a rich distribution of gas bodies which play a dominant role in the acoustic properties of eggs and are the most probable site of action for ultrasonic biological effects on these organisms. |
| Title |
Ultrasonic gene and drug delivery to the cardiovascular system. |
| Author |
Mayer CR, Bekeredjian R. |
| Journal |
Adv Drug Deliv Rev |
| Volume |
|
| Year |
2008 |
| Abstract |
Ultrasound targeted microbubble destruction has evolved as a promising tool for organ specific gene and drug delivery. This technique has initially been developed as a method in myocardial contrast echocardiography, destroying intramyocardial microbubbles to characterize refill kinetics. When loading similar microbubbles with a bioactive substance, ultrasonic destruction of microbubbles may release the transported substance in the targeted organ. Furthermore, high amplitude oscillations of microbubbles lead to increased capillary and cell membrane permeability, thus facilitating tissue and cell penetration of the released substance. While this technique has been successfully used in many organs, its application in the cardiovascular system has dominated so far. Drug delivery using microbubbles has played a minor role in the cardiovascular system. In contrast, gene transfer has been successfully achieved in many studies. Both viral and non-viral vectors were used for loading on microbubbles. This review article will give an overview on studies that have applied ultrasound targeted microbubble destruction to deliver substances in the heart and blood vessels. It will show potential therapeutic targets, especially for gene therapy, describe feasible substances that can be loaded on microbubbles, and critically discuss prospects and limitations of this technique. |
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
|
|
|
|
