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Improved Anatomical Specificity of Non-invasive Neuro-stimulation by High Frequency (5 MHz) Ultrasound.

Li GF, Zhao HX, Zhou H, Yan F, Wang JY, Xu CX, Wang CZ, Niu LL, Meng L, Wu S, Zhang HL, Qiu WB, Zheng HR - Sci Rep (2016)

Bottom Line: Electromyography (EMG) collected from tail muscles together with the motion response videos were analyzed for evaluating the stimulation effects.Our results indicate that 5 MHz ultrasound can successfully achieve neuro-stimulation.It provides a smaller stimulation region, which offers improved anatomical specificity for neuro-stimulation in a non-invasive manner.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biomedical and Health Engineering, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China.

ABSTRACT
Low frequency ultrasound (<1 MHz) has been demonstrated to be a promising approach for non-invasive neuro-stimulation. However, the focal width is limited to be half centimeter scale. Minimizing the stimulation region with higher frequency ultrasound will provide a great opportunity to expand its application. This study first time examines the feasibility of using high frequency (5 MHz) ultrasound to achieve neuro-stimulation in brain, and verifies the anatomical specificity of neuro-stimulation in vivo. 1 MHz and 5 MHz ultrasound stimulation were evaluated in the same group of mice. Electromyography (EMG) collected from tail muscles together with the motion response videos were analyzed for evaluating the stimulation effects. Our results indicate that 5 MHz ultrasound can successfully achieve neuro-stimulation. The equivalent diameter (ED) of the stimulation region with 5 MHz ultrasound (0.29 ± 0.08 mm) is significantly smaller than that with 1 MHz (0.83 ± 0.11 mm). The response latency of 5 MHz ultrasound (45 ± 31 ms) is also shorter than that of 1 MHz ultrasound (208 ± 111 ms). Consequently, high frequency (5 MHz) ultrasound can successfully activate the brain circuits in mice. It provides a smaller stimulation region, which offers improved anatomical specificity for neuro-stimulation in a non-invasive manner.

No MeSH data available.


Theoretical comparison of the stimulation region using 1 MHz and 5 MHz ultrasound.(a) Schematic diagram of focused ultrasound transducer. (b) Simulation results of 1 MHz ultrasound intensity, Y-Z plane (left), Y-X plane (right). (c) A mouse brain with its left hemisphere marked by two circles. One is for 1 MHz, −3 dB focal width (red, outside circle), the other one is for 5 MHz, −3 dB focal width (blue, inside circle). (d) Coronal section of a mouse brain, left side marked by two semi-ellipses which present 1 MHz, −3 dB sonication region (red, outside) and 5 MHz, −3 dB sonication region (blue, inside). (e) Simulation results of 5 MHz ultrasound which is similar with (b).
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f1: Theoretical comparison of the stimulation region using 1 MHz and 5 MHz ultrasound.(a) Schematic diagram of focused ultrasound transducer. (b) Simulation results of 1 MHz ultrasound intensity, Y-Z plane (left), Y-X plane (right). (c) A mouse brain with its left hemisphere marked by two circles. One is for 1 MHz, −3 dB focal width (red, outside circle), the other one is for 5 MHz, −3 dB focal width (blue, inside circle). (d) Coronal section of a mouse brain, left side marked by two semi-ellipses which present 1 MHz, −3 dB sonication region (red, outside) and 5 MHz, −3 dB sonication region (blue, inside). (e) Simulation results of 5 MHz ultrasound which is similar with (b).

Mentions: Figure 1a illustrates the outline of a concave transducer with its ultrasonic beam. Most of the acoustic energy concentrates on a region named as focal region. The width of focal region is proportional to the acoustic wavelength and the f-number of the transducer26. In the application field of biomedical studies, increasing the center frequency of a transducer is an efficient method to reduce the focal width. In order to theoretically evaluate the stimulation region by different ultrasound frequencies (1 MHz and 5 MHz), simulation was carried out by the Field II program27. Spatial peak temporal average intensity (Ispta), was used to represent the intensity of the ultrasound in this study. As the acoustic field simulation maps shown in Fig. 1b,e, the −3 dB intensity focal width of 1 MHz ultrasound is about 4.3 mm, while that parameter is significantly decreased to 0.86 mm for 5 MHz ultrasound. The Fig. 1c,d show the comparisons of focal width and depth for two transducers with 1 MHz and 5 MHz ultrasound frequency. Obviously, it tends to obtain a much smaller focal region using 5 MHz ultrasound than using 1 MHz ultrasound. So that 5 MHz ultrasound has the potential to achieve a much smaller stimulation region than 1 MHz ultrasound on the mouse brain.


Improved Anatomical Specificity of Non-invasive Neuro-stimulation by High Frequency (5 MHz) Ultrasound.

Li GF, Zhao HX, Zhou H, Yan F, Wang JY, Xu CX, Wang CZ, Niu LL, Meng L, Wu S, Zhang HL, Qiu WB, Zheng HR - Sci Rep (2016)

Theoretical comparison of the stimulation region using 1 MHz and 5 MHz ultrasound.(a) Schematic diagram of focused ultrasound transducer. (b) Simulation results of 1 MHz ultrasound intensity, Y-Z plane (left), Y-X plane (right). (c) A mouse brain with its left hemisphere marked by two circles. One is for 1 MHz, −3 dB focal width (red, outside circle), the other one is for 5 MHz, −3 dB focal width (blue, inside circle). (d) Coronal section of a mouse brain, left side marked by two semi-ellipses which present 1 MHz, −3 dB sonication region (red, outside) and 5 MHz, −3 dB sonication region (blue, inside). (e) Simulation results of 5 MHz ultrasound which is similar with (b).
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4837374&req=5

f1: Theoretical comparison of the stimulation region using 1 MHz and 5 MHz ultrasound.(a) Schematic diagram of focused ultrasound transducer. (b) Simulation results of 1 MHz ultrasound intensity, Y-Z plane (left), Y-X plane (right). (c) A mouse brain with its left hemisphere marked by two circles. One is for 1 MHz, −3 dB focal width (red, outside circle), the other one is for 5 MHz, −3 dB focal width (blue, inside circle). (d) Coronal section of a mouse brain, left side marked by two semi-ellipses which present 1 MHz, −3 dB sonication region (red, outside) and 5 MHz, −3 dB sonication region (blue, inside). (e) Simulation results of 5 MHz ultrasound which is similar with (b).
Mentions: Figure 1a illustrates the outline of a concave transducer with its ultrasonic beam. Most of the acoustic energy concentrates on a region named as focal region. The width of focal region is proportional to the acoustic wavelength and the f-number of the transducer26. In the application field of biomedical studies, increasing the center frequency of a transducer is an efficient method to reduce the focal width. In order to theoretically evaluate the stimulation region by different ultrasound frequencies (1 MHz and 5 MHz), simulation was carried out by the Field II program27. Spatial peak temporal average intensity (Ispta), was used to represent the intensity of the ultrasound in this study. As the acoustic field simulation maps shown in Fig. 1b,e, the −3 dB intensity focal width of 1 MHz ultrasound is about 4.3 mm, while that parameter is significantly decreased to 0.86 mm for 5 MHz ultrasound. The Fig. 1c,d show the comparisons of focal width and depth for two transducers with 1 MHz and 5 MHz ultrasound frequency. Obviously, it tends to obtain a much smaller focal region using 5 MHz ultrasound than using 1 MHz ultrasound. So that 5 MHz ultrasound has the potential to achieve a much smaller stimulation region than 1 MHz ultrasound on the mouse brain.

Bottom Line: Electromyography (EMG) collected from tail muscles together with the motion response videos were analyzed for evaluating the stimulation effects.Our results indicate that 5 MHz ultrasound can successfully achieve neuro-stimulation.It provides a smaller stimulation region, which offers improved anatomical specificity for neuro-stimulation in a non-invasive manner.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biomedical and Health Engineering, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China.

ABSTRACT
Low frequency ultrasound (<1 MHz) has been demonstrated to be a promising approach for non-invasive neuro-stimulation. However, the focal width is limited to be half centimeter scale. Minimizing the stimulation region with higher frequency ultrasound will provide a great opportunity to expand its application. This study first time examines the feasibility of using high frequency (5 MHz) ultrasound to achieve neuro-stimulation in brain, and verifies the anatomical specificity of neuro-stimulation in vivo. 1 MHz and 5 MHz ultrasound stimulation were evaluated in the same group of mice. Electromyography (EMG) collected from tail muscles together with the motion response videos were analyzed for evaluating the stimulation effects. Our results indicate that 5 MHz ultrasound can successfully achieve neuro-stimulation. The equivalent diameter (ED) of the stimulation region with 5 MHz ultrasound (0.29 ± 0.08 mm) is significantly smaller than that with 1 MHz (0.83 ± 0.11 mm). The response latency of 5 MHz ultrasound (45 ± 31 ms) is also shorter than that of 1 MHz ultrasound (208 ± 111 ms). Consequently, high frequency (5 MHz) ultrasound can successfully activate the brain circuits in mice. It provides a smaller stimulation region, which offers improved anatomical specificity for neuro-stimulation in a non-invasive manner.

No MeSH data available.