An international review of laser Doppler vibrometry: Making light work of vibration measurement

Transcranial ultrasound therapy is an increasing area of research for noninvasive treatments in the brain including targeted drug delivery Measurements of ultrasound transmission through rat parietal bone at five frequencies (0268 MHz, 0841 MHz, 1409 MHz, 1972 MHz and 253 MHz) were performed at 88 locations in 22 ex vivo rat skullcaps (Wistar) using a fiber-optic hydrophone system At submegahertz frequencies, the skull insertion loss was found to be proportional to animal mass, while at higher frequencies this trend was lost Maps of the transverse pressure profile of the transducer before and after skull insertion showed increased distortion effects at higher frequencies Parietal bone thickness was measured and was found to increase with increasing body mass Additional measurements were made through mouse and rabbit skulls at 253 MHz At this frequency, aberration effects through mouse skull were negligible, while large distortions were observed through rat and rabbit skull Preclinical transcranial ultrasound studies in rats may be improved by scaling applied powers according to body mass to produce more consistent in situ pressures

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Ultrasound Insertion Loss of Rat Parietal Bone Appears to Be Proportional to Animal Mass at Submegahertz Frequencies

Sound-field imaging, the visualization of spatial and temporal distribution of acoustical properties such as sound pressure, is useful for understanding acoustical phenomena This study investigated the use of parallel phase-shifting interferometry (PPSI) with a high-speed polarization camera for imaging a sound field, particularly high-speed imaging of propagating sound waves The experimental results showed that the instantaneous sound field, which was generated by ultrasonic transducers driven by a pure tone of 40 kHz, was quantitatively imaged Hence, PPSI can be used in acoustical applications requiring spatial information of sound pressure

High-speed imaging of sound using parallel phase-shifting interferometry

Focused ultrasound (FUS) shows great promise for use in the area of transcranial therapy. Currently dependent on MRI for monitoring, transcranial FUS would benefit from a real-time technique to monitor acoustic emissions during therapy. A polyvinylidene fluoride receiver with an active area of 17.8 mm2 and a film thickness of 110 μm was constructed. A compact preamplifier was designed to fit within the receiver to improve the receiver SNR and allow the long transmission line needed to remove the receiver electronics outside of the MRI room. The receiver was compared with a 0.5 mm commercial needle hydrophone and focused and unfocused piezoceramics. The receiver was found to have a higher sensitivity than the needle hydrophone, a more wideband response than the piezoceramic, and sufficient threshold for detection of microbubble emissions. Sonication of microbubbles directly and through a fragment of human skull demonstrated the ability of the receiver to detect harmonic bubble emissions, and showed potential for use in a larger scale array. Monitoring of disruption of the blood-brain barrier in rats showed functionality in vivo and the ability to detect subharmonic, harmonic, and wideband emissions during therapy. The receiver shows potential for monitoring acoustic emissions during treatments and providing additional parameters to assist treatment planning. Future work will focus on developing a multi-element array for transcranial treatment monitoring.

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A PVDF Receiver for Ultrasound Monitoring of Transcranial Focused Ultrasound Therapy

Acoustic levitation provides potential to characterize and manipulate material such as solid particles and fluid in a wall-less environment. While attempts to levitate small animals have been made, the biological effects of such levitation have been scarcely documented. Here, our goal was to explore if zebrafish embryos can be levitated (peak pressures at the pressure node and anti-node: 135 dB and 144 dB, respectively) with no effects on early development. We levitated the embryos (n = 94) at 2-14 hours post fertilization (hpf) for 1000 (n = 47) or 2000 seconds (n = 47). We compared the size and number of trunk neuromasts and otoliths in sonicated samples to controls (n = 94), and found no statistically significant differences (p > 0.05). While mortality rate was lower in the control group (22.3%) compared to that in the 1000 s (34.0%) and 2000 s (42.6%) levitation groups, the differences were statistically insignificant (p > 0.05). The results suggest that acoustic levitation for less than 2000 sec does not interfere with the development of zebrafish embryos, but may affect mortality rate. Acoustic levitation could potentially be used as a non-contacting wall-less platform for characterizing and manipulating vertebrae embryos without causing major adverse effects to their development.

/pdf/effects-of-acoustic-levitation-on-the-development-of-53x9vpoyz2.pdf

R.C Preston

Papers

Application and assessment of laser Doppler velocimetry for underwater acoustic measurements.