Knowledge Vault 3/25 - G.TEC BCI & Neurotechnology Spring School 2024 - Day 2
Ultrasound as a non-invasive tool for neurostimulation
Marc Fournelle, Fraunhofer IBMT (GE)
<Resume Image >

Concept Graph & Resume using Claude 3 Opus | Chat GPT4 | Llama 3:

graph LR classDef overview fill:#f9d4d4, font-weight:bold, font-size:14px; classDef ultrasound fill:#d4f9d4, font-weight:bold, font-size:14px; classDef therapy fill:#d4d4f9, font-weight:bold, font-size:14px; classDef neuromodulation fill:#f9f9d4, font-weight:bold, font-size:14px; classDef parameters fill:#f9d4f9, font-weight:bold, font-size:14px; classDef systems fill:#d4f9f9, font-weight:bold, font-size:14px; classDef summary fill:#f9d4d4, font-weight:bold, font-size:14px; A[Marc Fournelle] --> B[Fraunhofer IBMT: ultrasound research,
trends, neuromodulation. 1] A --> C[Fraunhofer IBMT: largest European
ultrasound facility. 2] C --> D[Ultrasound: cellular to
clinical applications. 3] C --> E[Multi-channel electronics: simple
to complex systems. 4] C --> F[Transducers: customize for
imaging, therapy. 5] C --> G[Software: control systems,
generate signals, extract data. 6] A --> H[Ultrasound therapy: significant
growth, new applications. 7] H --> I[HIFU: ablate tissue.
LIFU: neuromodulation. 8] I --> J[Ultrasound advantages: precision,
penetration, non-invasiveness. 9] I --> K[Ultrasound neuromodulation: animal
models, behavior effects. 10] I --> L[Human studies: sensory
perceptions, brain activity. 11] I --> M[Ultrasound parameters' effects
not fully understood. 12] A --> N[Ultrasound: pressure wave,
affected by tissue properties. 13] N --> O[Frequency impacts penetration,
precision, bandwidth. 14] N --> P[Intensity, duty cycle
impact energy deposition. 15] N --> Q[LIFU safety guidelines
still in development. 16] A --> R[Neuromodulation systems: complex
arrays to single-element transducers. 17] R --> S[Single element: fixed focus.
Array: 3D steering. 18] R --> T[Fraunhofer IBMT: flexible
matrix array systems. 19] T --> U[Systems deliver high
pressures, flexible sequences. 20] T --> V[Dynamic beam steering:
stimulate brain regions on demand. 21] T --> W[Systems: MR-compatible,
treatment planning integration. 22] T --> X[Dual-transducer cross-beam:
higher spatial precision. 23] A --> Y[Skull distorts focusing,
requires compensation. 24] Y --> Z[Phase correction techniques
for precise focusing through skull. 25] A --> AA[Medical ultrasound standards
used where applicable. 26] A --> AB[LIFU: promise for neuromodulation,
open questions remain. 27] AB --> AC[Flexible research systems
needed to address questions. 28] A --> AD[System miniaturization: trade-offs,
lose capabilities. 29] A --> AE[Whole-scalp coverage feasible,
increases cost, complexity. 30] class A,B,AB,AC,AD,AE summary; class C,D,E,F,G ultrasound; class H,I therapy; class J,K,L neuromodulation; class M,N,O,P,Q parameters; class R,S,T,U,V,W,X,Y,Z,AA systems;


1.-Mark from Fraunhofer IBMT presents an overview of ultrasound research, trends in ultrasound therapy, and ultrasound neuromodulation.

2.-Fraunhofer IBMT is one of the largest ultrasound research facilities in Europe, covering transducer design, electronics, software, and clinical translation.

3.-Ultrasound can image from the cellular level to clinical applications in both imaging and therapy.

4.-Multi-channel ultrasound electronics can range from simple few-channel systems to complex 1000+ channel systems for precise stimulation.

5.-Ultrasound transducers convert electrical signals to mechanical waves using piezoelectric crystals and are customized for different imaging and therapy applications.

6.-Software is used to control ultrasound systems, generate signals, and extract data for imaging or monitoring therapy.

7.-Ultrasound therapy has seen significant growth in the last decade with new applications emerging beyond traditional uses like kidney stone destruction.

8.-High intensity focused ultrasound (HIFU) is used for ablating tissue. Low intensity focused ultrasound (LIFU) is used for non-destructive neuromodulation.

9.-Ultrasound offers advantages of high spatial precision, deep penetration, and non-invasiveness compared to other neuromodulation methods like TMS, tDCS and DBS.

10.-Ultrasound neuromodulation has been studied in different animal models showing effects on behavior, neurotransmitter levels, and disease conditions like epilepsy.

11.-Human studies have demonstrated ultrasound's ability to evoke sensory perceptions and modulate brain activity related to sensory discrimination.

12.-The effects of various ultrasound parameters like frequency, pressure, pulse patterns on neuromodulation are not yet fully understood.

13.-Ultrasound is a pressure wave that acts as a longitudinal wave. Its propagation is affected by tissue properties causing effects like attenuation, reflection, and refraction.

14.-Ultrasound frequency impacts penetration depth, precision of focusing, and used bandwidth. 0.2-1 MHz is typically used for neuromodulation.

15.-Ultrasound intensity, duty cycle impact energy deposition. Must be chosen carefully to achieve desired effect while ensuring safety.

16.-Safety guidelines for LIFU neuromodulation are still being developed, in contrast to well-established standards for diagnostic ultrasound and HIFU ablation.

17.-Neuromodulation systems range from complex 1000+ element arrays for 3D focusing to simpler single-element transducers with flexible pulse parameters.

18.-Single element transducers have a fixed focus. Array transducers can steer the focus in 3D by applying phase delays.

19.-Fraunhofer IBMT develops flexible matrix array systems for neuromodulation research allowing control over key parameters and 3D focus steering.

20.-Systems can deliver pressures up to 9 MPa, sufficient for BBB opening and neuromodulation. Highly flexible pulse sequences can be defined.

21.-Dynamic beam steering allows moving the focus in arbitrary spatial patterns over time, enabling stimulation of different brain regions on demand.

22.-Systems are designed for high MR-compatibility for integration with MRI-based treatment planning. Markers help localize the transducer position.

23.-Dual-transducer cross-beam configurations are used to achieve higher spatial precision, overcoming the cigar-shaped focus of single transducers.

24.-The skull bone distorts ultrasound focusing due to its complex, layered structure with varying acoustic properties. This needs to be compensated.

25.-Phase aberration correction techniques using CT/MRI data of skull anatomy are applied for precise patient-specific focusing through the skull.

26.-Established medical ultrasound standards are used where applicable to prepare neuromodulation systems for clinical studies, as specific standards are still lacking.

27.-In summary, LIFU shows promise for non-invasive neuromodulation, but many open questions remain regarding optimal stimulation parameters and mechanisms of action.

28.-Flexible, research-suitable systems enabling a high degree of control over ultrasound parameters are needed to address these open questions.

29.-Size reduction of neuromodulation systems is possible but has trade-offs. Very small transducers lose capabilities for focusing and non-invasiveness.

30.-Whole-scalp coverage is feasible with ultrasound transducer arrays but increases cost and complexity due to high channel counts.

Knowledge Vault built byDavid Vivancos 2024