|
|
|
BRL Abstracts Database |
|
Your search for ultrasound produced 3296 results. Page 274 out of 330
| Title |
Thermodynamic method of B/A analysis of liposome suspensions: Prediction via single relaxation theory. |
| Author |
Tata DB, Dunn F. |
| Journal |
J Ultrasound Med |
| Volume |
|
| Year |
1992 |
| Abstract |
The enhanced ultrasonic nonlinear B/A measurements (via thermodynamic method) from liposome systems first reported by Zhang and coworkers are analyzed through relaxation theory. The enhanced ultrasonic absorption and sound velocity dispersion due to lipid structural relaxation are theoretically shown to accurately predict the enhanced B/A findings reported by Zhang and coworkers. |
| Title |
Thermographic investigation of ultrasonically induced temperature distribution in tissues and tissue equivalent phantoms. |
| Author |
Pashovkin T, Khiznyak E, Sarvazyan A. |
| Journal |
Arch Acoust |
| Volume |
|
| Year |
1984 |
| Abstract |
The purpose of the paper was to develop a computerized thermographic method for the investigation of the temperature fields in tissue phantoms irradiated by ultrasound and to study heating patterns in separated heterogeneous and homogenous phantoms. The developed thermographic system provided the possibility of obtaining threedimensional images of the temperature distributions in the irradiated samples. it is shown that he temperature patterns in the heterogeneous tissue phantoms irradiated by ultrasound can be dependent not only on the differences in bulk acoustic properties of the adjacent tissue but also on the difference in their shear properties. |
| Title |
Thickness-extensional trapped-energy mode transducers with no inharmonic spurious modes for any size of vibration area. |
| Author |
Yamada K, Shimizu H. |
| Journal |
Proc Ultrason Symp IEEE |
| Volume |
|
| Year |
1984 |
| Abstract |
In most of the thickness-extensional mode ultrasound transducers composed of a fully-electroded piezoelectric plate, a number of spurious vibrations appear near the main resonance because of mode coupling with higher-order radial vibrations. So, it is generally difficult to obtain a single-mode thickness-extensional vibrator. Trapped-energy mode transducers composed of a partially-electroded piezoelectric plate are free from spurious vibrations of inharmonic overtone modes is inevitable for the case of a large vibration area. This paper presents a new ultrasound transducer constructed by applying the authors? original technique of energy-trapping for a backward-wave mode thickness-extensional vibration in a PbTiO, ceramic plate. The backward-wave energy-trapping has a remarkable advantage over a usual forward-wave energy trapping in producing no inharmonic spurious modes for any size of the vibration area. Therefore, the transducer presented here operates in a pure thickness-extensional mode accompanied with no spurious modes irrespectively of the size of the vibration area. The transducer structure and the mechanism of the energy-trapping are described and experimental results are shown. |
| Title |
Third harmonic transmit phasing for SNR improvement in tissue harmonic imaging with Golay-encoded excitation. |
| Author |
Shen CC, Shi TY. |
| Journal |
Ultrasonics |
| Volume |
|
| Year |
2008 |
| Abstract |
BACKGROUND:
Ultrasound tissue harmonic signal generally provides superior image quality as compared to the linear signal. However, since the generation of the tissue harmonic signal is based on finite amplitude distortion of the propagating waveform, the penetration and the sensitivity in tissue harmonic imaging are markedly limited because of the low signal-to-noise ratio (SNR).
METHODS:
The method of third harmonic (3f(0)) transmit phasing can improve the tissue harmonic SNR by transmitting at both the fundamental (2.25MHz) and the 3f(0) (6.75MHz) frequencies to achieve mutual enhancement between the frequency-sum and the frequency-difference components of the second harmonic signal. To further increase the SNR without excessive transmit pressure, coded excitation can be incorporated in 3f(0) transmit phasing to boost the tissue harmonic generation.
RESULTS:
Our analyses indicate that the phase-encoded Golay excitation is suitable in 3f(0) transmit phasing due to its superior transmit bandwidth efficiency. The resultant frequency-sum and frequency-difference components of tissue harmonic signal can be simultaneously Golay-encoded for SNR improvement. The increase of the main-lobe signal with the Golay excitation in 3f(0) transmit phasing are consistent between the tissue harmonic measurements and the simulations. B-mode images of the speckle generating phantom also demonstrate the increases of tissue harmonic SNR for about 11dB without noticeable compression artifacts.
CONCLUSION:
For tissue harmonic imaging in combination with the 3f(0) transmit phasing method, the Golay excitation can provide further SNR improvement. Meanwhile, the axial resolution can be effectively restored by pulse compression while the lateral resolution remains unchanged. |
| Title |
Three dimensional impedance map analysis of rabbit liver. |
| Author |
Pawlicki AD, Dapore AJ, Sarwate S, O'Brien W Jr. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
2011 |
| Abstract |
One challenge of quantitative ultrasound is the identification of the scattering sites in tissue. Three dimensional (3‐D) impedance maps (3DZMs) created from a series of histological tissue slide images are a useful tool to identify the scattering structures. 3DZMs are virtual (computational) data sets of real tissue that can be used to study fundamental ultrasonic properties. In this work fatty rabbit liver was chemically fixed and thinly sliced (3 μm) to create a series of H&E histology images. These images were realigned to one another using a registration scheme and pixels were assigned an impedance value to create a 3‐D map of acoustic impedance. Through a power spectral analysis of the reconstructed 3‐D volume, the effective scatterer diameter was estimated for the tissue using the fluid filled sphere form factor model. The results showed that when weighting the estimation toward smaller scatterer sizes, the effective scatterer diameter was 7.04 ± 1.30 μm. In the actual tissue this diameter corresponds closely to the size of the liver cell nucleus. These results provide encouragement that the reconstructed 3‐D volume is an accurate acoustic representation of the tissue, and suggest that the nucleus could be a primary source of scattering in fatty liver. |
| Title |
Three-dimensional beam directivity of phase-steered ultrasound. |
| Author |
Wood SC, Shi Y. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1999 |
| Abstract |
A model is developed to compute the three-dimensional far-field acoustic pressure distribution of the waves radiated from an ultrasonic linear phased array with finite elemental dimensions. Based on the model, the three-dimensional beam directivity function is introduced and analyzed to investigate the effects of geometric parameters on the steering performance. It is confirmed that the elevation dimension does not influence the beam directivity in the azimuthal plane. This is not true, however, in nonazimuthal planes. In general, increasing the elevation dimension reduces the energy leaking into nonazimuthal directions. The influences of other transducer parameters, including the number of elements, interelement spacing, and aperture length, are also investigated. It is found that they have only trivial effects on the sideleaking, although they are the important factors that influence the directivity in the azimuthal plane. |
| Title |
Three-dimensional high-frequency spectral and envelope quantification of excised human lymph nodes. |
| Author |
Mamou JM, Coron A, Oelze ML, Beecroft ES, Hata M, Machi J, Laugier EY, Feleppa EJ. |
| Journal |
IEEE Int Ultrasonics Symp Proc |
| Volume |
|
| Year |
2010 |
| Abstract |
Quantitative imaging methods using high-frequency ultrasound (HFU, >20 MHz) offer a means of characterizing biological tissue at the microscopic level. In this study, threedimensional(3D) quantitative-ultrasound (QUS) methods were
developed to detect metastases in freshly-dissected lymph nodes of cancer patients. 3D ultrasound radio-frequency data were acquired using a 26-MHz center-frequency transducer, and each node was inked prior to tissue fixation to recover orientation after sectioning for 3D histological evaluation. Backscattered
echo signals were processed using 3D cylindrical regions-ofinterest (ROIs) to yield eight QUS estimates associated with tissue microstructure. The first four QUS estimates (i.e., effective scatterer size, acoustic concentration, intercept, and slope) were estimated from a normalized backscattered spectrum, and the
other four QUS estimates were obtained by parameterizing the envelope statistics of the ROIs using Nakagami and homodyned- K models. These QUS methods were applied to 145 lymph nodes from 95 colorectal and gastric cancer patients. The ability of these eight QUS estimates to classify lymph nodes and detect
cancer was evaluated using ROC curves. An area under the ROC curve of 0.971 with specificity and sensitivity of 91%(using a leave-one-out procedure) were obtained by combining effective scatterer size and one envelope parameter based on the
homodyned-K distribution. Therefore, these advanced 3D QUS methods potentially can be valuable for detecting small metastatic foci in dissected lymph nodes.
Index Terms—high-frequency ultrasound, quantitative ultrasound, lymph node. |
| Title |
Three-dimensional high-frequency ultrasonic parameter imaging of anterior segment pathology. |
| Author |
Silverman RH, Rondeau MJ, Lizzi FL, Coleman DJ. |
| Journal |
Ophthalmology |
| Volume |
|
| Year |
1995 |
| Abstract |
PURPOSE: High-frequency ultrasound allows high-resolution imaging of anterior segment anatomy and pathology. Acoustic echo data, however, contain information relating to the microanatomic structure of the interrogated tissue which is not evident in B-mode images. The aim of this study is to develop imaging techniques to demonstrate and quantify the distribution of acoustic scattering properties in ocular tissues in three dimensions.
METHODS: A tumor of the iris and a hyphema were scanned using a 50-MHz ultrasound probe mounted on a computer-controlled two-axis positioning system. Scan data from sequential parallel planes were used to make three-dimensional reconstructions. Digital signal processing and a mathematical model of acoustic backscatter then were used to represent the effective size and acoustic concentration of scattering elements using a false color representation superimposed on B-mode images. RESULTS: Three-dimensional reconstructions improved appreciation of the size and extent of pathology and allowed computation of tissue volumes. Parameter images demonstrated distinctive differences between diffuse and organized blood and allowed quantification of tumor scattering properties. CONCLUSIONS: Three-dimensional imaging of the anterior segment with high-frequency ultrasound allows construction of perspective images, which adds to the already significant clinical use of individual high-resolution B-mode images. Acoustic backscatter properties determined by tissue microstructure can be computed from echo data and represented in false color in three-dimensional reconstructions. |
| Title |
Three-dimensional high-frequency ultrasound imaging for longitudinal evaluation of liver metastases in preclinical models. |
| Author |
Graham KC, Wirtzfeld LA, MacKenzie LT, Postenka CO, Groom AC, MacDonald IC, Fenster A, Lacefield JC, Chambers AF. |
| Journal |
Cancer Res |
| Volume |
|
| Year |
2005 |
| Abstract |
Liver metastasis is a clinically significant contributor to the mortality associated with melanoma, colon, and breast cancer. Preclinical mouse models are essential to the study of liver metastasis, yet their utility has been limited by the inability to study this dynamic process in a noninvasive and longitudinal manner. This study shows that three-dimensional high-frequency ultrasound can be used to noninvasively track the growth of liver metastases and evaluate potential chemotherapeutics in experimental liver metastasis models. Liver metastases produced by mesenteric vein injection of B16F1 (murine melanoma), PAP2 (murine H-ras–transformed fibroblast), HT-29 (human colon carcinoma), and MDA-MB-435/HAL (human breast carcinoma) cells were identified and tracked longitudinally. Tumor size and location were verified by histologic evaluation. Tumor volumes were calculated from the three-dimensional volumetric data, with individual liver metastases showing exponential growth. The importance of volumetric imaging to reduce uncertainty in tumor volume measurement was shown by comparing three-dimensional segmented volumes with volumes estimated from diameter measurements and the assumption of an ellipsoid shape. The utility of high-frequency ultrasound imaging in the evaluation of therapeutic interventions was established with a doxorubicin treatment trial. These results show that three-dimensional high-frequency ultrasound imaging may be particularly well suited for the quantitative assessment of metastatic progression and the evaluation of chemotherapeutics in preclinical liver metastasis models. |
| Title |
Three-dimensional quantitative ultrasound for detecting lymph node metasteses |
| Author |
Saegusa-Beecroft E, Machi J, Mamou J, Hata M, Coron A, Yanagihara ET, Yamaguchi T, Oelze ML, Laugier P, Feleppa EJ |
| Journal |
J Surg Res |
| Volume |
|
| Year |
2013 |
| Abstract |
Purpose: Detection of metastases in lymph nodes (LNs) is critical for cancer management. Conventional histological methods may miss metastatic foci. To date, no practical means of evaluating the entire LN volume exists. The aim of this study was to develop fast, reliable, operator-independent, high-frequency, quantitative ultrasound (QUS) methods for evaluating LNs over their entire volume to effectively detect LN metastases. Methods: We scanned freshly excised LNs at 26 MHz and digitally acquired echo-signal data over the entire three-dimensional (3D) volume. A total of 146 LNs of colorectal, 26 LNs of gastric, and 118 LNs of breast cancer patients were enrolled. We step-sectioned LNs at 50-mm intervals and later compared them with 13 QUS estimates associated with tissue microstructure. Linear-discriminant analysis classified LNs as metastatic or nonmetastatic, and we computed areas (Az) under receiver-operator characteristic curves to assess classification performance. The QUS estimates and cancer probability values derived from discriminant analysis were depicted in 3D images for comparison with 3D histology. Results: Of 146 LNs of colorectal cancer patients, 23 were metastatic; Az = 0.9520 +/-0.021 (95% confidence interval [CI]: 0.911-0.993); sensitivity = 91.3% (specificity = 87.0%); and sensitivity = 100% (specificity = 67.5%). Of 26 LNs of gastric cancer patients, five were metastatic; Az = 0.962 +/- 0.039 (95% CI: 0.807-1.000); sensitivity
= 100% (specificity = 95.3%). A total of 17 of 118 LNs of breast cancer patients were metastatic; Az = 0.833 +/- 0.047 (95% CI: 0.741-0.926); sensitivity = 88.2% (specificity = 62.5%); sensitivity = 100% (specificity = 50.5%). 3D cancer probability images showed good correlation with 3D histology. Conclusions:
These results suggest that operator- and system-independent QUS methods allow reliable entire-volume LN evaluation for detecting metastases. 3D cancer probability. |
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
|
|
|
|
