Bypassing absorbing objects in focused ultrasound using computer generated holographic technique.

Area of Science:

• Acoustic physics
• Medical imaging
• Biomedical engineering

Background:

• Focused ultrasound (FUS) therapy heats targeted tissue but faces challenges with ultrasound absorbers in the acoustic path.
• Absorbers can cause unintended heating, posing a risk in clinical applications like brain and liver treatments.

Purpose of the Study:

• To propose and demonstrate an acoustic simulation-based solution using 3D continuous acoustic holograms to reduce absorber heating in FUS.
• To compare the holographic solution against the standard geometrical method for mitigating unwanted heating.

Main Methods:

• Generated 3D continuous acoustic holograms using the iterative Gerchberg-Saxton (GS) algorithm and fast Fourier transform (FFT) acoustic simulation.
• Demonstrated hologram performance via temperature elevation images acquired using MRI-guided FUS with a planar phased-array transducer.

Main Results:

• Successfully generated 3D holograms with reduced intensity in the absorber region, tested using letter patterns 'T,' 'A,' and 'U.'
• The holographic solution achieved a 76% reduction in heating on the absorber while maintaining comparable heating at the intended focus.

Conclusions:

• Demonstrated the first generation of efficient, uniform 3D ultrasound holograms for bypassing absorbers in FUS.
• The holographic technology offers superior performance and flexibility over geometrical methods, reducing clinical risks associated with unintended heating.