Rapid short-pulse sequences enhance the spatiotemporal uniformity of acoustically driven microbubble activity during flow conditions

Despite the promise of microbubble-mediated focused ultrasound therapies, in vivo findings have revealed over-treated and under-treated regions distributed throughout the focal volume. This poor distribution cannot be improved by conventional pulse shapes and sequences, due to their limited ability to control acoustic cavitation dynamics within the ultrasonic focus. This paper describes the design of a rapid short-pulse (RaSP) sequence which is comprised of short pulses separated by μs off-time intervals. Improved acoustic cavitation distribution was based on the hypothesis that microbubbles can freely move during the pulse off-times. Flowing SonoVue® microbubbles (flow velocity: 10 mm/s) were sonicated with a 0.5 MHz focused ultrasound transducer using RaSP sequences (peak-rarefactional pressures: 146–900 kPa, pulse repetition frequency: 1.25 kHz, and pulse lengths: 5–50 cycles). The distribution of cavitation activity was evaluated using passive acoustic mapping. RaSP sequences generated uniform distributions within the focus in contrast to long pulses (50 000 cycles) that produced non-uniform distributions. Fast microbubble destruction occurred for long pulses, whereas microbubble activity was sustained for longer durations for shorter pulses. High-speed microscopy revealed increased mobility in the direction of flow during RaSP sonication. In conclusion, RaSP sequences produced spatiotemporally uniform cavitation distributions and could result in efficient therapies by spreading cavitation throughout the treatment area

First in-vivo Demonstration of Bilateral Blood-Brain Barrier Opening Using Acoustic Holograms in Mice

[EN] Focused ultrasound (FUS) with microbubbles allows for non-invasive targeted drug delivery into the central nervous system (CNS) by temporally and locally disrupting the bloodbrain barrier (BBB). However, current FUS technologies are not able to simultaneously target several brain structures. In this work, we open the BBB in two regions in a murine brain using a single-element transducer with a coupled 3D-printed holographic lens, which is designed to simultaneously create two symmetric foci in anesthetized mice in vivo. The proposed approach shows many advantages: (1) simple and low-cost; (2) correction of aberrations due to skull and water cone; and (3) multiple BBB opening (BBBO) locations with only one sonication, becoming a time- and cost-effective therapeutic system for neurological diseases. For the in-vivo experiment, contrast-enhanced, T1- weighted MRI scan was conducted following BBBO, showing gadolinium extravasation at two symmetric focal spots. The two BBBO regions were separated by 3.0 +- 0.7 mm (n=5 mice) compared to 5.3 mm in full-wave simulations. This work shows the capability of bifocal ultrasound generation in separate animals using a unique uCT scan. A bilateral BBBO was achieved with a single sonication using a holographic lens in mice, thus improving the efficiency and defining a new approach for several neurodegenerative diseases targeting symmetric brain structures, e.g. hippocampus, putamen or caudate. This study demonstrates the feasibility of hologram-assisted BBBO for targeted drug delivery in the CNS in symmetric regions in separate hemispheres.This research has been supported by the Spanish Ministry of Science, Innovation and Universities through grants Juan de la Cierva - Incorporacion (IJC2018-037897-I) and PID2019-111436RB-C22, by the Agencia Valenciana de la Innovación through grant INNVAL10/19/016, by Generalitat Valenciana through grants No. ACIF/2017/045 and BEFPI/2019/075, and by the National Institutes of Health through grants 5R01EB009041 and 5R01AG038961. Action co-financed by the European Union through the Programa Operativo del Fondo Europeo de Desarrollo Regional (FEDER) of the Comunitat Valenciana 2014-2020 (IDIFEDER/2018/022).Jiménez-Gambín, S.; Jimenez, N.; Benlloch Baviera, JM.; Camarena Femenia, F.; Pouliopoulos, AN.; Konofagou, EE. (2020). First in-vivo Demonstration of Bilateral Blood-Brain Barrier Opening Using Acoustic Holograms in Mice. IEEE. 1-4. https://doi.org/10.1109/IUS46767.2020.9251487S1

Acoustic Holograms for Bilateral Blood-Brain Barrier Opening in a Mouse Model

[EN] Transcranial focused ultrasound (FUS) in conjunction with circulating microbubbles injection is the sole non-invasive technique that temporally and locally opens the blood-brain barrier (BBB), allowing targeted drug delivery into the central nervous system (CNS). However, single-element FUS technologies do not allow the simultaneous targeting of several brain structures with high-resolution, and multi-element devices are required to compensate the aberrations introduced by the skull. In this work, we present the first preclinical application of acoustic holograms to perform a bilateral BBB opening in two mirrored regions in mice. The system consisted of a single-element focused transducer working at 1.68 MHz, coupled to a 3D-printed acoustic hologram designed to produce two symmetric foci in anesthetized mice in vivo and, simultaneously, compensate the aberrations of the wavefront caused by the skull bones. T1-weighed MR images showed gadolinium extravasation at two symmetric quasi-spherical focal spots. By encoding time-reversed fields, holograms are capable of focusing acoustic energy with a resolution near the diffraction limit at multiple spots inside the skull of small preclinical animals. This work demonstrates the feasibility of hologram-assisted BBB opening for low-cost and highly-localized targeted drug delivery in the CNS in symmetric regions of separate hemispheres.This work was supported in part by the Spanish Ministry of Science, Innovation, and Universities (MICINN) through Grants "Juan de la Cierva -Incorporacion" IJC2018-037897-I, and PID2019-111436RB-C22, in part by the Agencia Valenciana de la Innovacio through Grants INNVAL10/19/016, INNCON/2021/8, and INNVA1/2020/92, in part by Generalitat Valenciana through Grants ACIF/2017/045, AICO/2020/268, and BEFPI/2019/075, and in part by the National Institutes of Health through Grants 5R01EB009041 and 5R01AG038961. Action co-financed by the European Union through the Programa Operativo del Fondo Europeo de Desarrollo Regional (FEDER) of the Comunitat Valenciana (IDIFEDER/2018/022 and IDIFEDER/2021/004)Jiménez-Gambín, S.; Jimenez, N.; Pouliopoulos, AN.; Benlloch Baviera, JM.; Konofagou, EE.; Camarena Femenia, F. (2022). Acoustic Holograms for Bilateral Blood-Brain Barrier Opening in a Mouse Model. IEEE Transactions on Biomedical Engineering. 69(4):1359-1368. https://doi.org/10.1109/TBME.2021.31155531359136869

Focused ultrasound mitigates pathology and improves spatial memory in Alzheimer's mice and patients

Rationale: Bilateral sonication with focused ultrasound (FUS) in conjunction with microbubbles has been shown to separately reduce amyloid plaques and hyperphosphorylated tau protein in the hippocampal formation and the entorhinal cortex in different mouse models of Alzheimer's disease (AD) without any therapeutic agents. However, the two pathologies are expressed concurrently in human disease. Therefore, the objective of this study is to investigate the effects of repeated bilateral sonications in the presence of both pathologies. Methods: Herein, we investigate its functional and morphological outcomes on brains bearing both pathologies simultaneously. Eleven transgenic mice of the 3xTg-AD line (14 months old) expressing human amyloid beta and human tau and eleven age-matched wild-type littermates received four weekly bilateral sonications covering the hippocampus followed by working memory testing. Afterwards, immunohistochemistry and immunoassays (western blot and ELISA) were employed to assess any changes in amyloid beta and human tau. Furthermore, we present preliminary data from our clinical trial using a neuronavigation-guided FUS system for sonications in AD patients (NCT04118764). Results: Interestingly, both wild-type and transgenic animals that received FUS experienced improved working memory and spent significantly more time in the escape platform-quadrant, with wild-type animals spending 43.2% (sham: 37.7%) and transgenic animals spending 35.3% (sham: 31.0%) of the trial in the target quadrant. Furthermore, this behavioral amelioration in the transgenic animals correlated with a 58.3% decrease in the neuronal length affected by tau and a 27.2% reduction in total tau levels. Amyloid plaque population, volume and overall load were also reduced overall. Consistently, preliminary data from a clinical trial involving AD patients showed a 1.8% decrease of amyloid PET signal 3-weeks after treatment in the treated hemisphere compared to baseline. Conclusion: For the first time, it is shown that bilateral FUS-induced BBB opening significantly and simultaneously ameliorates both coexistent pathologies, which translated to improvements in spatial memory of transgenic animals with complex AD, the human mimicking phenotype. The level of cognitive improvement was significantly correlated with the volume of BBB opening. Non-transgenic animals were also shown to exhibit similar memory amelioration for the first time, indicating that BBB opening results into benefits in the neuronal function regardless of the existence of AD pathology. A potential mechanism of action for the reduction of the both pathologies investigated was the cholesterol metabolism, specifically the LRP1b receptor, which exhibited increased expression levels in transgenic mice following FUS-induced BBB opening. Initial clinical evidence supported that the beta amyloid reduction shown in rodents could be translatable to humans with significant amyloid reduction shown in the treated hemisphere

Investigation of the motion of a spherical object located at soft elastic and viscoelastic material interface for identification of material properties

Measuring the properties of soft viscoelastic materials is challenging. Here, the motion of a spherical object located at the soft elastic and viscoelastic material interface for the identification of material properties is thoroughly investigated. Formulations for different loading cases were derived. First, the theoretical models for a spherical object located at an elastic medium interface were derived, ignoring the medium viscosity. After summarizing the model for the force reducing to zero following the initial loading, we developed mathematical models for the force reducing to a lower non-zero value or increasing to a higher non-zero value, following the initial loading. Second, a similar derivation process was followed to evaluate the response of a spherical object located at a viscoelastic medium interface. Third, by performing systematic analyses, the theoretical models obtained via different approaches were compared and evaluated. Fourth, the measured and predicted responses of a spherical object located at a gelatin phantom interface were compared and the viscoelastic material properties were identified. It was seen that the frequency of oscillations of a spherical object located at the sample interface during loading was 10–15% different from that during unloading in the experimental studies here. The results showed that different loading cases have immense practical value and the formulations for different loading cases can provide an accurate determination of material properties in a multitude of biomedical and industrial applications

Alteration of functional connectivity in the cortex and major brain networks of non-human primates following focused ultrasound exposure in the dorsal striatum

Background: Focused ultrasound (FUS) is a non-invasive neuromodulation technology that is being investigated for potential treatment of neurological and psychiatric disorders. FUS combined with microbubbles can temporarily open the intact blood-brain barrier (BBB) of animals and humans, and facilitate drug delivery. FUS exposure, either with or without microbubbles, has been demonstrated to alter the behavior of non-human primates (NHP), and previous studies have demonstrated the transient and long-term effects of FUS neuromodulation on functional connectivity using resting state functional MRI. The behavioral effects of FUS vary depending on whether or not it is applied in conjunction with microbubbles to open the BBB, but it is unknown whether opening the BBB affects functional connectivity differently than FUS alone. Objective: To compare the effects of applying FUS alone (FUS neuromodulation) and FUS with microbubbles (FUS-BBB opening) on changes of resting state functional connectivity in NHP. Methods: We applied 2 min FUS exposure without (neuromodulation) and with microbubbles (BBB opening) in the dorsal striatum of lightly anesthetized non-human primates, and acquired resting state functional MRI 40 min respectively after FUS exposure. The functional connectivity (FC) in the cortex and major brain networks between the two approaches were measured and compared. Results: When applying FUS exposure to the caudate nucleus of NHP, we found that both FUS neuromodulation can activate FC between caudate and insular cortex, while inhibiting the FC between caudate and motor cortex. FUS-BBB opening can activate FC between the caudate and medial prefrontal cortex, and within the frontotemporal network (FTN). We also found both FUS and FUS-BBB opening can significantly activate FC within the default mode network (DMN). Conclusion: The results suggest applying FUS to a deep brain structure can alter functional connectivity in the DMN and FTN, and that FUS neuromodulation and FUS-mediated BBB opening can have different effects on patterns of functional connectivity