Device for treating biological tissue

Abstract

A device for treating a biological tissue (19) has a light source (14) for sending a plurality of light pulses (15) to the tissue (19) in order to place the tissue (19) in vibration during a treatment period (31). The device comprises a vibration sensor (21) which records the amplitude of the vibration (22) of the tissue (19) caused by the light source (14). By setting a current measurement (27) of the amplitude against an initial measurement (26) of the amplitude, a control unit (16) forms a relative value (30). The control unit (16) processes the relative value (30) in order to generate a control signal for the light source (14).

Description

Technical Field

[0001] This invention relates to a device for treating biological tissues. Background Technology

[0002] It is known that if tissue is set to vibrate at a frequency within the range of ultrasound, a therapeutic effect can be achieved. This is described in Teudt et al., IEEE T Bio-med Eng 58(6) 2011, along with many other works, and in Wenzel et al., JBO 14(4) 2009, which describes the auditory nerve of the cochlea.

[0003] Tissue vibrations can be induced by applying repeated light pulses to the tissue, which are then absorbed by the tissue. The light pulses trigger thermoplastic expansion and subsequent contraction, thus enabling the excitation of vibrations. To date, it has been found that modulating the light source to produce the desired effect in biological tissues without damaging the tissue is not straightforward. The intensity of a tissue's response to a light pulse depends on the type and state of the tissue, as well as the amplitude and frequency of the vibration. For tissues that respond strongly to light pulses, if the light pulse is too strong, there is a risk of permanent tissue damage due to excessively high amplitude. In less sensitive tissues, if the light pulse is too weak or the amplitude is too low, the desired effect may not be produced. Summary of the Invention

[0004] The object of this invention is to provide an apparatus for treating biological tissue, wherein the tissue can be treated with pulsed light, thereby reliably setting a desired vibrational state of the tissue. This object is achieved by utilizing the features of the independent claim, drawing upon the aforementioned prior art. Advantageous embodiments are given in the dependent claims.

[0005] The device according to the invention includes a light source to place the tissue in vibration in order to send multiple light pulses to the tissue during a treatment period. The device also includes a vibration sensor that measures the amplitude of the vibration of the tissue induced by the light source. A relative value is formed in the control unit by setting the current measured value of the amplitude relative to an initial measured value of the amplitude. The relative value is processed in the control unit to generate a control signal for the light source.

[0006] This invention is based on the idea of ​​controlling a light source according to a control signal determined by the vibrations of the actual tissue induced by the light pulse. Therefore, instead of adjusting the light source based on pre-made assumptions about the effects of the light pulse on the tissue, a control signal is generated for the light source that depends on the actual vibrations of the tissue. This provides the feasibility of adjusting the light source in a targeted manner to generate specific vibrational states within the tissue.

[0007] It is known that the absolute value of the measured amplitude does not always represent a suitable standard for controlling the light source. Therefore, this invention proposes setting the current measurement of amplitude relative to an initial measurement of amplitude. The initial measurement recorded at the start of treatment specifies the tissue's response to the light pulse at the start of treatment. The ratio between the current and initial measurements of amplitude forms a measure related to the degree of tissue vibration. This information is processed in the control unit as a relative value to control further processes of the treatment utilizing the light pulse.

[0008] The amplitude of tissue vibration depends on the pulse energy; the higher the pulse energy, the greater the amplitude. If the amplitude of tissue vibration increases even when the pulse energy remains the same, it indicates that the vibration is stronger.

[0009] It can normalize the initial and current amplitude measurements to pulse energy, resulting in normalized relative values. It can read from these normalized relative values ​​whether the amplitude of tissue vibration has changed relative to the same pulse energy. If a light pulse with the same pulse energy is sent to the tissue, the relative value is automatically a normalized relative value within that meaning.

[0010] Treatment performed using the device according to the invention does not cause permanent structural changes in the tissue. Instead, the tissue should be excited or stimulated by vibration without damaging its structure. If the amplitude increases too much, there is a risk of mechanical damage to the tissue due to structural tearing, or thermal damage due to insufficient dissipation of the currently generated heat. Therefore, a limit value for the relative value can be predetermined, and the light source can be controlled such that the relative value does not exceed this limit value. For example, this limit value can have a value between 1.1 and 2, preferably between 1.3 and 1.6.

[0011] It is also possible to predetermine a target value for the relative value and control the light source to achieve the target value. Treatment can be terminated when the target value is reached, i.e., the light source can be controlled to stop emitting any light pulses. The light source can also be controlled to maintain the relative value at the target value for a predetermined time interval. Other variations are also possible, such as continuing treatment with a lower relative value after the target value has been reached. For example, this can be achieved by reducing the pulse energy or pulse duration of the light source and / or increasing the time interval between two consecutive pulses. For example, the target value for the relative value can be between 1.05 and 1.5, preferably between 1.1 and 1.3, and more preferably between 1.15 and 1.25.

[0012] In one embodiment, a characteristic curve for the relative value to change over time is predetermined, and the light source is controlled such that the relative value follows the characteristic curve.

[0013] The light source can be controlled to emit light pulses with constant energy. The time interval between light pulses can remain constant during treatment. However, the time interval within treatment can also be modified to influence the progression of tissue vibration.

[0014] In different embodiments, low-energy light pulses are delivered to the tissue at the start of treatment, the energy level being determined to reliably prevent tissue damage. The pulse energy can be increased during treatment until the desired vibrational state of the tissue is achieved. Using standardized relative values ​​ensures that the amplitude does not increase to a level that would cause tissue damage.

[0015] The device can include a closed control loop that controls the emission of light pulses in a manner that sets the vibration of tissue to a predetermined amplitude. For example, it is desirable to maintain the amplitude at a constant set value after the amplitude increases at the start of treatment. The control signal of the light source can be designed to produce a constant set value.

[0016] Another feasible approach is to predetermine the characteristic curve of the amplitude of tissue vibration and control the light source through a closed control loop, thereby setting the amplitude according to the predetermined characteristic curve. For example, a characteristic curve showing a predetermined increase or decrease in amplitude measurement over time can be predetermined at the start of treatment or during treatment intervals. Final control of the treatment process can be implemented additionally or as an alternative to relative value control.

[0017] The light source can be configured to direct a large number of similar light pulses to the tissue during treatment. The light pulses can have the same pulse duration and the same pulse energy, resulting in the same amount of energy being delivered to the tissue with each light pulse. It is also feasible to use different light pulses for treatment to modulate tissue vibration, wherein, in particular, the pulse duration and / or pulse energy and / or pulse repetition frequency can be adjustablely controlled by a controller during the treatment duration. For example, the duration of a single light pulse can be between 0.1 ns and 100 μs, preferably between 10 ns and 2 μs.

[0018] The wavelength of the light can encompass one, two, or more than two spectral ranges, which are absorbed to varying degrees by the tissue to excite vibrations to varying degrees in different parts of the tissue. The light source can be a laser source emitting light within a strictly defined spectral range. In this case, the various spectral ranges can encompass the entire spectrum from ultraviolet light to far-infrared light, and can be, for example, in the range between 300 nm and 3000 nm. Specific embodiments can include, for example, lasers emitting at the fundamental frequency and its harmonic components (e.g., 1064 nm and 532 nm). Pulses of different wavelengths can be mixed synchronously or asynchronously in any desired order. A preferred variant for exciting vibrations is the alternating emission of light pulses, wherein the light pulses are located in different spectral ranges. The time pulse intervals can be the same.

[0019] The light pulses can be emitted in such a manner that the duration of each light pulse is shorter than the time interval between the end of the first light pulse and the start of the second light pulse that immediately follows the first light pulse. Preferably, the duration of the pause between two consecutive light pulses is at least 10 times longer than the pulse duration, more preferably 100 times longer, and even more preferably 1000 times longer.

[0020] The pause between two light pulses should not be too long, lest the tissue vibration decay back to its initial state during this period. Instead, the goal is to excite the tissue to produce continuous vibrations through the sum of the introduced light pulses. Therefore, the interval between pulses should preferably be shorter than the thermal relaxation time of the excited tissue.

[0021] Treatment refers to the continuous vibrational therapy that a series of light pulses delivers to the tissue as a whole. If another light pulse is directed into the tissue after it has simultaneously returned to its initial state, then this marks the beginning of a new treatment. The time required for treatment is called the treatment duration.

[0022] The invention also includes an apparatus configured to guide optical pulses in the form of therapeutic pulses and optical pulses in the form of measurement pulses to tissue during a treatment period. The therapeutic pulses can have a different spatial range than the measurement pulses. Different spatial ranges mean that the area covered on the treated tissue is larger or smaller. Specifically, the area covered by the therapeutic pulses can be larger than the area covered by the measurement pulses. For example, the measurement pulses can be placed at the center of the treatment area to record the maximum amplitude of tissue vibration. In addition to, or as an alternative to, different spatial ranges, the measurement pulses and therapeutic pulses can also have different pulse durations and / or pulse repetition frequencies.

[0023] The control unit can be configured to process only amplitude measurements of tissue vibrations triggered by the measuring pulses for the purpose of controlling the light source. One or more treatment pulses (their duration and energy tailored to the treatment requirements) can be pre-programmed by two measuring pulses in each case.

[0024] The device can include a measurement light source for generating measurement pulses, which is separate from the light source used for tissue treatment. The measurement pulses can be located in a different spectral range than the treatment pulses. Both the measurement pulses and the treatment pulses can be generated by a uniform light source.

[0025] The light source can be a laser. The beam path of the light source can be shaped to illuminate a point on the tissue. The point size, i.e., the diameter of the point, can be selected according to the tissue being treated. If treating the retina of the eye, the point size can be between 50 μm and 500 μm, preferably between 100 μm and 200 μm. For example, in the case of the tympanic membrane, the point can have a size of 5 mm. For example, in the case of other tissues such as subcutaneous nerve tissue, other point sizes depending on the size of the treatment area can be used, such as between 2 mm and 20 mm, preferably between 3 mm and 8 mm.

[0026] For example, radiation exposure from a single light pulse can range from 0.1 to 100 mJ / cm². 2 The duration of a single treatment can be between 0.02 s and 100 s, preferably between 0.05 s and 10 s, and more preferably between 0.1 s and 1 s. However, permanent vibrational excitation, such as modulated excitation for the tympanic membrane, middle ear, or inner ear, can also be considered. The number of light pulses during treatment can be between 100 and 100,000. Treatment refers to a series of light pulses that generally provide continuous vibrational therapy to the tissue. If another light pulse is directed into the tissue after the tissue has simultaneously returned to its initial state, then this is the start of a new treatment. All light pulses during treatment can be directed to the same area of ​​the tissue.

[0027] Tissue vibrations triggered by light pulses can result in thermoplastic expansion and contraction. Vibration sensors can be designed to directly measure tissue expansion. This is possible, for example, if the vibration sensor is an optical or acoustic interferometer.

[0028] Vibration sensors can also be used to measure the sound waves emitted during vibration, their amplitude, and / or their spectrum, thereby drawing conclusions about the vibrational state of the tissue. Vibration sensors can include microphones, hydrophones, or piezoelectric elements that respond to pressure waves. Attached Figure Description

[0029] The invention is now described by way of example with reference to the accompanying drawings, according to advantageous embodiments. It shows that:

[0030] Figure 1 Embodiments of the device according to the invention are shown;

[0031] Figure 2 The curves show the vibrations induced by the light pulses at the start of treatment;

[0032] Figure 3 This is shown during the later stages of treatment. Figure 2 Diagram;

[0033] Figures 4-6 Alternative embodiments of the device according to the invention are shown; and

[0034] Figure 7 This shows the amplitude of tissue vibration during the treatment process. Detailed Implementation

[0035] exist Figure 1 The apparatus according to the invention shown includes a laser source 14 that emits light pulses 15 of at least one wavelength under the control of a control unit 16. The light pulses 15 are guided to the patient's nerve tissue 19 via suitable optical elements 17. Each light pulse 15 induces vibrations in the retinal tissue through thermoplastic expansion. These vibrations generate pressure waves 22 that propagate from the nerve tissue 19. Figure 2 and Figure 3 An exemplary curve showing how the pressure wave changes over time is shown.

[0036] The device includes a vibration sensor 21 in the form of a hydrophone. The vibration sensor 21 provides feedback to the pressure wave 22 and outputs an electrical signal representing the amplitude and frequency of the pressure wave 22. The amplitude of the pressure wave 22 corresponds to the amplitude of the vibration of the nerve tissue 19.

[0037] The electrical signal generated by the vibration sensor 21 is transmitted as an amplitude measurement value to the control unit 16 via the wire 23 and processed in the control unit 16. At the start of treatment, a first light pulse 15 is sent to the nerve tissue 19, thereby inducing a first pressure wave 22, the amplitude of which is... Figure 2 As shown in the figure, the curve of pressure wave 22 is recorded by vibration sensor 21. The associated amplitude measurement value is stored in memory 24 as the initial amplitude measurement value 26.

[0038] During treatment, another light pulse 15 of the same type is directed to the nerve tissue 19 at constant intervals. Each light pulse 15 causes re-excitation of the vibration of the nerve tissue 19. During the pause between two light pulses 15, the vibration of the nerve tissue 19 decays rather than disappears completely. Overall, the light pulses 15 result in continuous vibrational excitation of the nerve tissue 19. Figure 7 An exemplary treatment time curve is shown, where the horizontal axis represents time t and the vertical axis represents the amplitude of tissue vibration. The relative value 30 according to the invention is determined by setting the current measurement of the amplitude relative to the initial measurement 26 of the amplitude. The interval of the light pulses ensures that the tissue vibration does not completely decay during the treatment time period 31.

[0039] By utilizing the permanent excitation of the same type of light pulse 15, the amplitude of the pressure wave 22 is increased. Figure 3 The text is a jumbled collection of characters and phrases, seemingly from different sources and lacking coherent sentences. A direct translation wouldn't be meaningful. Figure 5 The pressure wave 22 at the end of the treatment is shown. The amplitude measurement 27 is 50% greater than the initial amplitude measurement 26.

[0040] All amplitude measurements 27 obtained during treatment are directed to the control unit 16, where a relative value is formed by setting each amplitude measurement 27 relative to an initial amplitude measurement 26 stored in memory 24. The relative value is compared to a limit value in comparator 25 of the control unit 16. Whenever the relative value reaches the limit value, the control unit 16 sends a shutdown signal to the light source 14, causing the light source 14 to cease emitting light pulses 15. The limit value for the ratio (relative value) between the amplitude measurement value and the initial amplitude measurement 26 is 1.5 in this embodiment, and this limit is reached when the amplitude measurement 27 is 50% higher than the initial amplitude measurement 26. Figure 7 Treatment is terminated when the limit is reached. Subsequently, the neural tissue reverts to its initial state without vibration.

[0041] According to Figure 4In this embodiment, the light source 14 preferably does not emit the same type of light pulses 15, but instead varies the pulse energy and / or intervals during the treatment duration. The apparatus includes an additional measuring light source 28 that directs measuring pulses 18 to the nerve tissue 19 during pauses between treatment pulses 13 emitted by the light source 14. The treatment pulses 13 cover a larger area on the nerve tissue 19 compared to the measuring pulses 18. The pressure wave induced solely by the measuring pulses 18 is evaluated in the control unit 16 and set relative to an initial measurement 26 of the amplitude obtained using the same measuring pulses 18. In this way, the curve of the treatment pulses 13 can be aligned with the treatment needs without compromising the measurements using the measuring pulses 18. After reaching the target value for amplitude, the pulse energy of the treatment pulses 13 is reduced so that the amplitude of the vibration of the nerve tissue 19 remains constant for the remaining duration of treatment.

[0042] According to Figure 5 In this implementation, similarly, the light pulse 15 varies during the duration of treatment. The memory 24 of the control unit 16 stores not only the initial measurement value 26 of the amplitude, but also the pulse energy of the first light pulse 15, which induces a pressure wave 22. Subsequently, pressure waves are induced by light pulses 15, which have other pulse energies, pulse durations, and / or pulse repetition rates. The amplitude value 27 is normalized to pulse energy in module 38 before being sent to comparator 25 for comparison with the initial measurement value 26 of the amplitude. A normalized relative value is generated, which reproduces the ratio of the amplitude value 27 to the normalized pulse energy of the initial measurement value 26 of the amplitude, and represents the change in the state of the neural tissue 19.

[0043] exist Figure 6 An alternative implementation is shown, in which the amplitude of tissue vibration is measured in the form of an optical sensor using a vibration sensor 21.

Claims

1. An apparatus for treating biological tissue (19), the apparatus having a light source (14) for sending multiple light pulses (15) onto the tissue (19) during a treatment period (31) to place the tissue (19) in vibration, the apparatus having a vibration sensor (21) that measures the amplitude of vibration (22) of the tissue (19) caused by the light source (14), and the apparatus having a control unit (16) that forms a relative value (30) by setting a current amplitude measurement value (27) relative to an initial amplitude measurement value (26), and the control unit processes the relative value (30) to generate a control signal for the light source (14), the relative value being a ratio between the amplitude measurement value and the initial amplitude measurement value.

2. The apparatus according to claim 1, characterized in that, The initial amplitude measurement (26) and the current amplitude measurement (27) are normalized to pulse energy, such that the relative value (30) is a normalized relative value.

3. The apparatus according to claim 1 or 2, characterized in that, A target value is provided for the relative value (30), and the control unit (16) drives the light source (14) to make the relative value (30) reach the target value.

4. The apparatus according to claim 3, characterized in that, The target value is between 1.05 and 1.

5.

5. The apparatus according to claim 4, characterized in that, The target value is between 1.1 and 1.

3.

6. The apparatus according to claim 4, characterized in that, The target value is between 1.15 and 1.

25.

7. The apparatus according to claim 1 or 2, characterized in that, A characteristic curve for the time-varying relative value (30) is provided, and the control unit (16) drives the light source (14) to make the relative value (30) follow the characteristic curve.

8. The apparatus according to claim 1 or 2, characterized in that, The control signal is integrated into a closed control loop, which is used to set the relative value to a predetermined target value or a predetermined time curve.

9. The apparatus according to claim 1 or 2, characterized in that, The duration of the pause between two consecutive light pulses is less than the relaxation time of the tissue.

10. The apparatus according to claim 1 or 2, characterized in that, The light pulse (15) is directed to a point on the tissue, wherein the point has a diameter between 0.1 mm and 10 mm.

11. The apparatus according to claim 10, characterized in that, The point has a diameter between 0.2 mm and 3 mm.

12. The apparatus according to claim 1 or 2, characterized in that, Light pulses of different spectral ranges are directed onto the tissue.

13. The apparatus according to claim 1 or 2, characterized in that, During the treatment period (31), light pulses (15) are sent to the tissue (19) in the form of measurement pulses (18) and light pulses (15) are sent to the tissue (13) at different times, wherein the vibration sensor (21) measures the amplitude of the tissue vibration caused by the measurement pulses (18), and the measured values ​​are processed in the control unit (16).

14. The apparatus according to claim 13, characterized in that, The treatment pulse (13) covers a larger area on the tissue (19) compared to the measurement pulse (18).

15. The apparatus according to claim 13, characterized in that, The treatment pulse (13) is output in a different spectral range than the measurement pulse (18).

16. The apparatus according to claim 1 or 2, characterized in that, During treatment, the number of light pulses (15) is between 100 and 100,000.

17. The apparatus according to claim 1 or 2, characterized in that, The vibration sensor (21) is designed to determine the amplitude measurement (27) by utilizing the pressure wave caused by the vibration of the tissue (19).

18. The apparatus according to claim 1 or 2, characterized in that, The vibration sensor (21) is designed to optically determine the amplitude of tissue expansion and contraction using an interferometer.

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