Chirp-coded excitation imaging with a high-frequency ultrasound annular array

Area of Science:

• Biomedical Engineering
• Medical Imaging
• Acoustics

Background:

• High-frequency ultrasound (HFU) offers fine-resolution imaging for ophthalmology, dermatology, and small animal studies.
• Conventional HFU faces limitations in depth of field and penetration due to short wavelengths and high attenuation.
• Existing HFU methods struggle to image deeper tissues effectively.

Purpose of the Study:

• To enhance the depth of field (DOF) and penetration depth of HFU imaging.
• To investigate the efficacy of chirp-coded signals for improved HFU performance.
• To compare chirp-coded HFU with conventional impulse imaging.

Main Methods:

• Utilized a five-element annular array with synthetic-focusing for extended DOF.
• Employed 8-microsecond chirp-coded signals to excite array elements for increased penetration.
• Applied linear filtering to restore axial resolution and enhance signal-to-noise ratio (SNR).

Main Results:

• Chirp-coded excitation maintained axial and lateral resolution comparable to conventional methods.
• Evaluated SNR and penetration depth using a tissue-mimicking phantom with 10-microm glass beads.
• Ex vivo ophthalmic images revealed finer details with chirp-coded HFU than with conventional imaging.

Conclusions:

• Chirp-coded excitation is a viable method to improve HFU penetration depth and SNR without compromising resolution.
• This technique enables visualization of finer structures in biological tissues, particularly in ophthalmology.
• The study demonstrates a significant advancement in HFU imaging capabilities for deep tissue analysis.