Functional module for acoustic/mechanical stimulation
Nicolaus Copernicus University
- Publisher
- Zenodo
- Language
- en
Abstract
Milestone M2 – Functional module for acoustic/mechanical stimulation describes the development and integration of a functional module for mechanical stimulation with a high-speed optical coherence tomography (OCT) system. In summary: A piezoelectric transducer was designed to generate air-borne ultrasound at a frequency of 1.04 MHz, focused on the surface of a sample (for example, a cornea). The acoustic radiation force produced at the sample interface generates transient displacements, which in turn induce mechanical waves propagating through the sample. The transducer is driven by a waveform generator and an RF amplifier, and is positioned as close to perpendicular to the sample surface as experimentally feasible, so as not to block the OCT optical beam. Initial tests were conducted at AGH University in Cracow using a scattering gelatin phantom. Successive ultrasound pulses of 200 µs were delivered at 10 Hz, and a laser Doppler vibrometer was used to record microscopic displacements of the phantom surface induced by the ultrasound. The results demonstrated displacement maps of the phantom surface at different time instances (from 1 ms to 5 ms), confirming the propagation of elastic surface waves generated by non-contact ultrasound excitation. Figure 1 (Figure1_M2) illustrates the experimental setup, showing the swept-source OCT instrument integrated with the mechanical stimulation module.Figure 2 (Figure2_M2) presents the non-contact mechanical stimulation unit, highlighting the focusing air-coupled ultrasound transducer.Figure 3 (Figure3_M2) displays the wave propagation maps of the gelatin phantom surface, recorded at successive time frames, which clearly demonstrate the dynamic motion induced by ultrasound excitation. In conclusion, the non-contact mechanical stimulation module has been successfully developed, integrated with the OCT system, and experimentally validated, fulfilling the objectives of Milestone M2.
Full text
Raul Urriza Arpal Ireneusz Grulkowski Nicolaus Copernicus University in Torun MILESTONE M2 – Functional module for acoustic/mechanical stimulation The methodology requires integration of mechanical stimulation with high-speed optical coherence tomography (OCT) system (Fig. 1) to monitor propagation of mechanical waves in the sample. Fig. 1. Experimental system. swept-source OCT instrument with mechanical stimulation module. Non-contact mechanical excitation of the sample is performed with a specially designed piezoelectric transducer enabling generation of air-borne ultrasound at the frequency of 1.04 MHz focused on the interface of the sample (e.g. cornea). The shape of the cylindrical transducer provides maximum amplitude at the distance of 17 mm behind the interface of the transducer. Ultrasound beam reflection at the sample interface produces acoustic radiation force toward the medium, inducing a transient displacement at that surface that leads to generation of a mechanical wave propagating in the sample. The transducer is driven by a waveform generator, and the output signal from the generator is amplified by an RF amplifier (Fig. 2). The device was aligned as close to perpendicular to the sample surface as experimentally feasible, in order not to block the imaging optical beam (Fig. 2).
Fig. 2. Module for non-contact mechanical stimulation of the sample. (Left) Focusing air-coupled ultrasound transducer The initial tests were performed at the AGH University in Cracow using a scattering gel phantom. Successive pulses (each 200 μs) were delivered with a pulse repetition frequency of 10 Hz. A laser Doppler vibrometer was used to visualize micro-displacements of the gelatin phantom surface due to ultrasoundinduced elastic wave. The results in Fig. 3 show displacement maps of the phantom surface at different time instances (from 1 ms to 5 ms) demonstrating propagation of the mechanical surface wave. Fig. 3. Wave propagation of phantom surface due to non-contract ultrasound tapping.
