an-ultrasonic-tool-for-nerve-conduction-block-in-diabetic-rat-models

An Ultrasonic Tool for Nerve Conduction Block in Diabetic Rat Models

Nerve conduction block with a high intensity-focused ultrasound (HIFU) transducer has been performed in normal and diabetic animal models recently. HIFU ...

National Health Research Institutes

The electroacoustic conversion efficiency of the ultrasonic transducer is a critical performance index for high-power applications. The material properties, volume fraction (VF) and aspect ratio (AR) are typically regarded as the design parameters of the piezocomposite transducer. We hypothesized that the spacing between piezoelectric rods was also a dominant factor. Therefore, the inter-rod coupling effects on the efficiency of 1-3 piezocomposite ultrasonic transducers were investigated in this study. The efficiencies of six flat and three curved 1.0 MHz PZT4 epoxy composite transducers with different geometric parameters were measured. Finite element transient analyses of the inter-rod electrical-mechanical coupling in the composites were carried out to explain the measured results. The experimental results showed that for 0.47 AR, the 79% VF transducers had lower efficiency than the 64% VF and 53% VF transducers. For 0.19 AR, the efficiency of the 59% VF transducer was not greater than the efficiency of the 39% VF transducer. Numerical analyses demonstrated that the positive peak voltage induced by the coupling of the side rods was more than twice the level induced by the coupling of the diagonal rods for any spacing. The diagonal coupling voltage peak did not change for spacings larger than 0.2 mm. Moreover, for spacings of 0.05 and 0.1 mm, the inter-rod coupling caused 24% and 20% waveform shifts of the driving voltage, respectively, while the 0.2 mm spacing coupling caused a 14% reduction in the amplitude of the driving voltage. As a result, the asymmetry of the driving voltage degraded the efficiency of the composite transducers and became more severe when the spacing was decreased. We concluded that the efficiency loss induced by inter-rod coupling as a function of spacing should be considered when designing piezocomposite transducers.

Assessing the relationship between the inter-rod coupling and the efficiency of piezocomposite high-intensity focused ultrasound transducers.

Measurements of ultrasonic attenuation in the sciatic nerves of rats were performed to verify the feasibility of ultrasound diagnosis of peripheral neuropathy and to avoid damage to the nerves caused by overheating in pain management applications. A rat model of diabetic peripheral neuropathy was established. The proximal-segment and middle-segment sciatic nerves of control and neuropathic rats were dissected for the attenuation measurement. Two commercial ultrasound transducers and a self-developed experimental platform were used in the measurements. Using H&E staining and transmission electron (TE) microscopy, morphological analysis of the control and neuropathic nerves was performed to determine the relationship between attenuation and the histology of the nerves. The experimental results showed that the attenuation coefficients of the control, second-week, fourth-week, and eighth-week neuropathic nerves were -6.68 ± 0.50, -5.61 ± 0.34, -6.27 ± 0.40, and -7.10 ± 0.35 dB/cm at 2.68 MHz, respectively. The respective values at 7.50 MHz were -14.96 ± 0.79, -12.65 ± 0.28, -13.98 ± 1.07, and -16.00 ± 0.54 dB/cm. The changes in the attenuation coefficients were significantly different among the second-week, fourth-week, and eighth-week DN nerves. Additionally, the ultrasonic attenuation coefficient of the rat sciatic nerve was fourfold that of the cat brain and cow liver and twofold that of human muscle.

Measurement of ultrasonic attenuation in diabetic neuropathic sciatic nerves for diagnostic and therapeutic applications.

Patients with diabetic neuropathy often have neuropathic pain. The purpose of our work was to investigate the effects of high-intensity focused ultrasound (HIFU) on the conduction block of normal and neuropathic nerves for soothing pain. Adult male Sprague-Dawley rats were used, and diabetes was induced by streptozotocin injection. Diabetic neuropathy was evaluated with animal behavior tests. Sciatic nerves of both control and neuropathic rats were dissected from the starting point of the sciatic nerve to the point where the sural nerve ends near the ankle. The nerves were stored in Ringer's solution. The in vitro nerve was placed on a self-developed experimental platform for HIFU exposure. Stimulation and recording of the compound action potentials (CAPs) and sensory action potentials (SAPs) were performed. Control and neuropathic nerves exposed or not exposed to HIFU were submitted to histologic analysis. For the control and neuropathic nerves, suppression of CAPs and SAPs started 2 min post-HIFU treatment. Maximum suppression of SAPs was 34.4 ± 3.2% for the control rats and 11.6 ± 2.0% and 9.8 ± 3.0% for rats 4 wk post-injection and 8 wk post-injection, respectively. Time to full recovery was 25, 70 and 80 min, respectively. Histologic analysis revealed that the nerves in which CAPs and SAPs did not fully recover were damaged thermally or mechanically by HIFU. It is feasible to reversibly block nerves with appropriate HIFU treatment. Diabetic nerves were less suppressed by HIFU and were more vulnerable to permanent damage.

Article	Year
Assessing the relationship between the inter-rod coupling and the efficiency of piezocomposite high-intensity focused ultrasound transducers. Ultrasonics\| PubMed ID: 24269167	2014
Measurement of ultrasonic attenuation in diabetic neuropathic sciatic nerves for diagnostic and therapeutic applications. Annals of biomedical engineering\| PubMed ID: 24566928	2014
High-intensity focused ultrasound attenuates neural responses of sciatic nerves isolated from normal or neuropathic rats. Ultrasound in medicine & biology\| PubMed ID: 25438842	2015

Jung-Sung Cheng

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