Ultrasound-induced Gas Release from Contrast Agent Microbubbles

We investigated gas release from two hard-shelled ultrasound contrast agents by subjecting them to high-mechanical index (MI) ultrasound and simultaneously capturing high-speed photographs. At an insonifying frequency of 1.7 MHz, a larger percentage of contrast bubbles is seen to crack than at 0.5 MHz. Most of the released gas bubbles have equilibrium diameters between 1.25 and 1.75 /spl mu/m. Their disappearance was observed optically. Free gas bubbles have equilibrium diameters smaller than the bubbles from which they have been released. Coalescence may account for the long dissolution times acoustically observed and published in previous studies. After sonic cracking, the cracked bubbles stay acoustically active

Discrimination between quarry blasts and micro-earthquakes using spectral analysis, applied to local Israeli events

This study presents the concept of spectral modulation and a time-frequency analysis, applied to broadband local ($5<\Delta<200$\,km) seismic data from quarry blasts and micro-earthquakes, kindly supplied by the Institute for Petroleum Research and Geophysics (IPRG), Holon, Israel, from the so-called GIF-array. The aim of this research is verification of ripple-firing by recognition of scalloping trends in amplitude-spectra and hence discriminating quarry blasts from other events. Most quarry blasts are ripple-fired, in northern Israel open pit blasts; consequently the event discrimination method based on the recognition of ripple-firing patterns in the signal was chosen. The methods presented in this dissertation might also be applicable for deconvolution and dereverberation purposes in exploration seismology.Comment: MSc dissertation, Utrecht Universit

Predictions of angle dependent tortuosity and elasticity effects on sound propagation in cancellous bone

The anisotropic pore structure and elasticity of cancellous bone cause wave speeds and attenuation in cancellous bone to vary with angle. Previously published predictions of the variation in wave speed with angle are reviewed. Predictions that allow tortuosity to be angle dependent but assume isotropic elasticity compare well with available data on wave speeds at large angles but less well for small angles near the normal to the trabeculae. Claims for predictions that only include angle-dependence in elasticity are found to be misleading. Audio-frequency data obtained at audio-frequencies in air-filled bone replicas are used to derive an empirical expression for the angle-and porosity-dependence of tortuosity. Predictions that allow for either angle dependent tortuosity or angle dependent elasticity or both are compared with existing data for all angles and porosities

Noninvasive microbubble-based pressure measurements: a simulation study

This paper describes a noninvasive method to measure local hydrostatic pressures in fluid filled cavities. The method is based on the disappearance time of a gas bubble, as the disappearance time is related to the hydrostatic pressure. When a bubble shrinks, its response to ultrasound changes. From this response, the disappearance time, and with it the hydrostatic pressure, can be determined. We investigated the applicability of the gases Ar, C3F8, Kr, N2, Ne, and SF6, based on their diffusive properties. For pressure measurements with a limited duration, e.g. 150 ms, Kr and Ar bubbles are most suitable, since they are most sensitive to pressure change. If there is also a limitation to bubble size, e.g. a maximum diameter of 6 lm, SF6 is most suitable. We present improvements of a method that correlates the duration of the decay of the fundamental ultrasound response to the hydrostatic overpressure. We propose to correlate the duration until subharmonic occurrence in combination with its decay, to hydrostatic overpressure, since the subharmonic decays more rapidly than the fundamental response. For a dissolving Ar gas bubble with an initial diameter of 14 lm, the overpressure can be determined 4 times as precise from the decay of the subharmonic response as from the decay of the fundamental response. Overpressures as small as 11 mmHg may be discriminated with this method

Use and usability of custom-made orthopedic shoes

The goal of this study was to investigate the use of custom-made orthopedic shoes (OS) and the association between the use of OS and the most relevant aspects of their usability. Over a 6-month period, patients meeting the inclusion criteria were recruited by 12 orthopedic shoe companies scattered throughout the Netherlands and asked to complete a questionnaire composed of a pre- and post-OS section. Patients with different pathologies were included in the study (n = 339; response 67%). Mean age of the patients was 63 +/- 15 years, and 38% were male. Three months after delivery, 81% of the patients used their OS frequently (4-7 days/week), 13% occasionally (1-3 days/week), and 6% did not use their OS. Associations were found between use and all measured aspects of usability (p-values varied from <0.001 to 0.028). Patients who used their OS more often had a more positive opinion regarding all the aspects of usability. We conclude that all aspects of the usability of OS are relevant in relation to their use and should be taken into account when prescribing and evaluating OS

Periodic shock-emission from acoustically driven cavitation clouds:a source of the subharmonic signal

Single clouds of cavitation bubbles, driven by 254 kHz focused ultrasound at pressure amplitudes in the range of 0.48–1.22 MPa, have been observed via high-speed shadowgraphic imaging at 1 × 10⁶ frames per second. Clouds underwent repetitive growth, oscillation and collapse (GOC) cycles, with shock-waves emitted periodically at the instant of collapse during each cycle. The frequency of cloud collapse, and coincident shock-emission, was primarily dependent on the intensity of the focused ultrasound driving the activity. The lowest peak-to-peak pressure amplitude of 0.48 MPa generated shock-waves with an average period of 7.9 ± 0.5 μs, corresponding to a frequency of f₀/2, half-harmonic to the fundamental driving. Increasing the intensity gave rise to GOC cycles and shock-emission periods of 11.8 ± 0.3, 15.8 ± 0.3, 19.8 ± 0.2 μs, at pressure amplitudes of 0.64, 0.92 and 1.22 MPa, corresponding to the higher-order subharmonics of f₀/3, f₀/4 and f₀/5, respectively. Parallel passive acoustic detection, filtered for the fundamental driving, revealed features that correlated temporally to the shock-emissions observed via high-speed imaging, p(two-tailed) 200 μm diameter, at maximum inflation), that developed under insonations of peak-to-peak pressure amplitudes >1.0 MPa, emitted shock-waves with two or more fronts suggesting non-uniform collapse of the cloud. The observations indicate that periodic shock-emissions from acoustically driven cavitation clouds provide a source for the cavitation subharmonic signal, and that shock structure may be used to study intra-cloud dynamics at sub-microsecond timescales

A pocket-sized recipe for cooking up a scientific manuscript

This booklet is intended to be read from cover to cover, in the order of writing. It is not so much a general guideline as a proven recipe to get your scientific manuscript accepted by a peer-reviewed journal. We do not differentiate between high-impact peer-reviewed journals and low-impact national conference proceedings. The principle of writing is the same. The recipe works for both. When using any other recipe for cooking, you are going to use it only a couple of times. After that, you are going to adjust the recipe to match your flavour. This recipe is intended for the same purpose. Follow it get get your first papers and your thesis accepted. After that, start changing it so that you can produce manuscripts about which you feel more comfortable

Ultrasound homogenises suspensions of hydrophobic particles

Hydrophobic particles inherently resist being suspended. Hydrophobic particles might be regarded as tiny solid particles surrounded by a thin gaseous shell. It has been hypothesised that hydrophobic particles act as cavitation nuclei. This cavitation behaviour would explain the translation speeds observed when hydrophobic polystyrene microspheres were driven through a liquid medium by means of ultrasound.5 These translation speeds corresponded to those observed with gas microbubbles of similar sizes. If hydrophobic particles do have a thin gaseous layer surrounding the solid cores, a sound field of sufficient pressure amplitude might force the gas layer to form and inertial cavity and subsequently fragment during the collapse phase. In this study, we investigated whether hydrophobic particles can be forced to suspend by using ultrasound. Hydrophobic particles of the materials C65 and ZnO can be forced to be suspended in water using ultrasound. The high-speed observations confirm that hydrophobic particles can act as cavitation nuclei. The lack of cavitation after the first pulse indicates that the gas layer surrounding the hydrophobic particle dissolves after inertial cavitation.Comment: 6 pages, 3 figures (7 frames), Submitted to the 39th Symposium on UltraSonic Electronics (USE2019

Micro-computed tomography and brightness-mode ultrasound show air entrapments inside tablets

publishedVersionPeer reviewe

Development and reproducibility of a short questionnaire to measure use and usability of custom-made orthopaedic shoes

Objective: To develop a short and easy to use questionnaire to measure use and usability of custom-made orthopaedic shoes, and to investigate its reproducibility.\ud Design: Development of the questionnaire (Monitor Orthopaedic Shoes) was based on a literature search, expert interviews, 2 expert meetings, and exploration and testing of reproducibility. The questionnaire comprises 2 parts: a pre part, measuring expectations; and a post part, measuring experiences.\ud Patients: The pre part of the final version was completed twice by 37 first-time users before delivery of their orthopaedic shoes. The post part of the final version was completed twice by 39 first-time users who had worn their orthopaedic shoes for 2–4 months.\ud Results: High reproducibility scores (Cohen’s kappa > 0.60 or intra class correlation > 0.70) were found in all but one question of both parts of the final version of the Monitor Orthopaedic Shoes questionnaire. The smallest real difference on a visual analogue scale (100 mm) ranged from 21 to 50 mm. It took patients approximately 15 minutes to complete one part.\ud Conclusion: Monitor Orthopaedic Shoes is a practical and reproducible questionnaire that can measure relevant aspects of use and usability of orthopaedic shoes from a patient’s perspective