Factors Associated with Energy Efficiency of Focused Ultrasound Through the Skull: A Study of 3D-Printed Skull Phantoms and Its Comparison with Clinical Experiences

While focused ultrasound (FUS) is non-invasive, the ultrasound energy is attenuated by the skull which results in differences in energy efficiency among patients. In this study, we investigated the effect of skull variables on the energy efficiency of FUS. The thickness and density of the skull and proportion of the trabecular bone were selected as factors that could affect ultrasound energy transmittance. Sixteen 3D-printed skull models were designed and fabricated to reflect the three factors. The energy of each phantom was measured using an ultrasonic sound field energy measurement system. The thickness and proportion of trabecular bone affected the attenuation of transmitted energy. There was no difference in the density of the trabecular bone. In clinical data, the trabecular bone ratio showed a significantly greater correlation with dose/delivered energy than that of thickness and the skull density ratio. Currently, for clinical non-thermal FUS, the data are not sufficient, but we believe that the results of this study will be helpful in selecting patients and appropriate parameters for FUS treatment.

On dissection of the uterine wall during laparoscopic myomectomy

BACKGROUND: Laparoscopic myomectomy is becoming the leading method of surgical treatment of uterine fibroids while preserving reproductive and menstrual functions. Increasingly, ultrasound energy is used to dissect the myometrium. Meanwhile, the mode and direction of the ultrasound energy supply to minimize damage to the underlying tissues have not been specified. AIM: The aim of this study was to perform a comparative analysis of the myometrium and the fibroid pseudocapsule in the projection of the myoma nodule after dissection using ultrasound energy with different initial characteristics of the surgical instrument. MATERIALS AND METHODS: For comparison, we selected two instruments with a longitudinal ultrasound energy supply with an output frequency of 80 MHz ... 2.5 GHz and 47 kHz at intermittent operating mode of 5/10 sec and one torsion instrument with a transverse ultrasound energy supply with an output frequency of 36 kHz at intermittent operating mode of 3/30 sec. RESULTS: Our study has shown that the smallest zone of irreversible changes is formed when using ultrasound energy with an output frequency of 36 kHz at intermittent operating mode of 3/30 sec with its transverse feed at 90 degrees to the blade, and the largest zone of irreversible changes is formed when using ultrasound energy with an output frequency of 47 kHz at intermittent operating mode of 5/10 sec with its longitudinal feed. CONCLUSIONS: Morphometric studies with an analysis of the depth of necrotic and necrobiotic changes in the myometrial tissue showed that from the standpoint of reproductive surgery, it is preferable to use USE with an output frequency of 36 kHz at intermittent operating mode of 3/30 sec with its transverse feed.

Effect of ultrasonication on the size distribution and stability of cellulose nanocrystals in suspension: an asymmetrical flow field-flow fractionation study

Cellulose nanocrystals (CNCs) are bio-based building blocks for sustainable advanced materials with prospective applications in polymer composites, emulsions, electronics, sensors, and biomedical devices. However, their high surface area-to-volume ratio promotes agglomeration, which restrains their performance in size-driven applications, thereby hindering commercial CNC utilization. In this regard, ultrasonication is commonly applied to disperse CNCs in colloidal suspensions; however, ultrasonication methodology is not yet standardized and knowledge of the effects of ultrasound treatments on CNC size distribution is scarce. The major goals of this study were attributed to targeted breakage of CNC agglomerates and clusters by ultrasound. The evolution of particle size distribution and potential de-sulfation by ultrasonication as well as the long-term stability of ultrasonicated CNC suspensions were investigated. Colloidal suspensions of sulfated CNCs were isolated from cotton α-cellulose. Effects of ultrasonication on particle size distribution were determined by asymmetrical flow field-flow fractionation (AF4) coupled with on-line multi-angle light scattering and ultraviolet spectroscopy. These results were complemented with off-line dynamic light scattering. High ultrasound energy densities facilitated cumulative dispersion of CNC clusters. Consequently, the mean rod length decreased logarithmically from 178.1 nm at an ultrasound energy input of 2 kJ g−1 CNC to 141.7 nm (− 20%) at 40 kJ g−1 CNC. Likewise, the hydrodynamic diameter of the particle collective decreased logarithmically from 94.5 to 73.5 nm (− 22%) in the same processing window. While the rod length, below which 95 wt% of the CNCs were found, decreased from 306.5 to 231.8 nm (− 24%) from 2 to 40 kJ g−1 CNC, the shape factor of the main particle fraction ranged from 1.0 to 1.1, which indicated a decreasing number of dimers and clusters in the particle collective. In summary, progressing ultrasonication caused a shift of the particle length distribution to shorter particle lengths and simultaneously induced narrowing of the distribution. The suspension’s electrical conductivity concurrently increased, which has been attributed to faster diffusion of smaller particles and exposure of previously obscured surface charges. Colloidal stability, investigated through electrical AF4 and electrophoretic light scattering, was not affected by ultrasonication and, therefore, indicates no de-sulfation by the applied ultrasound treatment. Occurrence of minor CNC agglomeration at low ultrasound energy densities over the course of 6 months suggest the effect was not unmitigatedly permanent.

Efficacy Estimation of Microbubble-Assisted Local Sonothrombolysis Using a Catheter with a Series of Miniature Transducers

Intravascular ultrasound has good prospects for clinical applications in sonothrombolysis. The catheter-based side-looking intravascular ultrasound thrombolysis (e.g., Ekosonic catheters) used in clinical studies has a high frequency (2 MHz). The lower-frequency ultrasound requires a larger-diameter transducer. In our study, we designed and manufactured a small ultrasound-based prototype catheter that can emit a lower frequency ultrasound (1.1 MHz). In order to evaluate the safety and efficacy of local low-frequency ultrasound-enhanced thrombolysis, a microbubble (MB) was introduced to augment thrombolysis effect of locally delivered low-intensity ultrasound. The results demonstrated that combination of ultrasound and MB realized higher clot lysis than urokinase-only treatment (17.0% ± 1.2% vs. 14.9% ± 2.7%) under optimal ultrasound settings of 1.1 MHz, 0.414 MPa, 4.89 W/cm2, 5% duty cycle and MB concentration of 60 μg/mL. When urokinase was added, the fibrinolysis accelerated by MB and ultrasound resulted in a further increased thrombolysis rate that was more than two times than that of urokinase alone (36.7% ± 5.5% vs. 14.9% ± 2.7%). However, a great quantity of ultrasound energy was required to achieve substantial clot lysis without MB, leading to the situation that temperature accumulated inside the clot became harmful. We suggest that MB-assisted local sonothrombolysis be considered as adjuvant therapy of thrombolytic agents.

Effect of Ultrasonication on the Size Distribution and Stability of Cellulose Nanocrystals in Suspension: an Asymmetrical Flow Field-flow Fractionation Study

Cellulose nanocrystals (CNCs) are bio-based building blocks for sustainable advanced materials with prospective applications in polymer composites, emulsions, electronics, sensors, and biomedical devices. However, their high surface area-to-volume ratio promotes agglomeration, which restrains their performance in size-driven applications, thereby hindering commercial CNC utilization. In this regard, ultrasonication is commonly applied to disperse CNCs in colloidal suspensions; however, ultrasonication methodology is not yet standardized and knowledge of the effects of ultrasound treatments on CNC size distribution is scarce. This limits the ability to tailor CNC performance in advanced materials. Herein, colloidal suspensions of sulfated CNCs were treated with different ultrasound energy densities up to 40 kJ g−1 CNC and then size-fractionated with asymmetrical flow field-flow fractionation (AF4). On-line multi-angle light scattering and ultraviolet spectroscopy along with off-line dynamic light scattering were used to determine the effect of ultrasonication on particle size distribution. High energy densities facilitated cumulative dispersion of CNC clusters and mean particle length decreased logarithmically with increasing energy density. The suspension’s electrical conductivity concurrently increased, which has been attributed to faster diffusion of smaller particles and exposure of previously obscured surface charges. Colloidal stability, investigated through electrical AF4 (EAF4) and electrophoretic light scattering, was not affected by ultrasonication. Occurrence of minor CNC agglomeration at low ultrasound energy densities over the course of six months suggest the effect was not unmitigatedly permanent.

Application of Augmented Water Flooding Using Ultrasound Energy to Improve Oil Recovery

The application of ultrasound energy in improving oil recovery is an emerging technique, it has been tested in laboratories and some field applications in different parts of the world. In this study, Nigerian crude oil of 4.21 cSt viscosity and sandstone rock samples were tested using a designed and constructed experimental rig. The rig is an analogue of a standard core flooding set up and works on the principle of fluid flow in porous media. Furthermore, a modeled equation was developed to better understand the effects of power and time on the volume of oil recovered at a constant ultrasound frequency. Results obtained show a positive impact in the recovery of residual oil during waterflooding with the assisted ultrasound energy. About 2-fold increase in the recovery of oil was observed when the ultrasound energy was applied to augment the waterflooding process. Model equations developed were found to be adequate because the adjusted and predicted R-squared values show reasonable agreement (R-adjusted = 0.9993, R-Predicted = 0.9974).