Devices for treating biological tissues

Abstract

The present invention relates to a device for treating living tissue (19), comprising a light source (14) for sending a number of light pulses (15) to the tissue (19) within a treatment period (31) to vibrate the tissue (19). The device comprises a vibration sensor (21) for sensing the amplitude of the vibrations (22) of the tissue (19) caused by the light source (14). A control unit (16) calculates a relative value (30) by ratioing a current measurement (27) of the amplitude to an initial measurement (26) of the amplitude. The control unit (16) processes the relative value (30) to generate a control signal for the light source (14).

Description

Technical Field

[0001] The present invention relates to an apparatus for treating biological tissue.

[0002] It is known that a therapeutic effect can be obtained by vibrating tissue at a frequency in the ultrasonic range. This and many other things are described in Teudt et al., IEEE T Bio-med Eng 58(6)2011 for nerve cells, and Wenzel et al., JBO 14(4)2009 for the auditory nerve.

[0003] Tissue can be vibrated by applying repetitive light pulses to the tissue, and the repetitive light pulses are absorbed by the tissue. The light pulses cause thermoplastic expansion and subsequent contraction, and thus can be used to excite vibrations. So far, it has been found that it is not so easy to adjust the light source so that the light pulses produce the desired effect on living tissue without damaging the tissue. How strongly the tissue reacts to the light pulses depends on the type and state of the tissue as well as the amplitude and frequency of the vibrations. In the case of tissue that reacts strongly to light pulses, if the light pulses are too strong, there is a risk that the tissue will be permanently damaged as a result of the amplitude being too large. If the sensitivity of the tissue is low, if the light pulses are too weak or the amplitude is too small, the desired effect may not be obtained.

[0004] Based on the object of developing an apparatus for treating biological tissue that can use pulsed light to treat the tissue, thereby reliably generating the desired vibration state of the tissue. Based on the foregoing prior art, this object is achieved by the features of the independent claims. Preferred embodiments are specified in the dependent claims.

[0005] The apparatus according to the present invention comprises a light source for sending a number of light pulses onto tissue during a treatment period, thereby causing the tissue to vibrate. The apparatus also comprises a vibration sensor for measuring the amplitude of the tissue vibration caused by the light source. A relative value is formed in the control unit by associating the current measurement of amplitude with an initial measurement of 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 concept of controlling a light source based on a control signal determined based on the actual vibrations of tissue caused by light pulses. Therefore, the light source is no longer tuned based on pre-established assumptions about the effect of light pulses on tissue; instead, a control signal dependent on the actual vibrations of the tissue is generated for the light source. This provides the option of tuning the light source in a targeted manner so that a specific vibrational state is generated within the tissue.

[0007] It has been recognized that the absolute value of the measured amplitude itself does not necessarily represent a suitable criterion for controlling the light source. Therefore, the present invention includes a proposal to correlate the current measurement of amplitude with an initial measurement of amplitude. The initial measurement, recorded at the start of the treatment period, specifies how the tissue responds to the light pulse at the start of treatment. The ratio between the current and initial measurement of amplitude forms a measure related to the degree to which the tissue is vibrated. This information is processed in the form of relative values ​​in a control unit to control the further course of treatment with light pulses.

[0008] The amplitude of tissue vibration depends on the pulse energy; the higher the pulse energy, the larger the amplitude. If the amplitude of tissue vibration increases while the pulse energy remains the same, this indicates a stronger vibration.

[0009] The initial and current amplitude measurements can be normalized to the pulse energy such that the relative values ​​are normalized relative values. Whether the amplitude of tissue vibration has changed for the same pulse energy can be read from the normalized relative values. The relative values ​​are automatically normalized relative values ​​within the range of meaning when light pulses with the same pulse energy are delivered to the tissue.

[0010] The treatment using the apparatus according to the present invention does not cause permanent structural changes in tissue. Instead, the tissue should be excited or stimulated by vibration without damaging its structure. If the amplitude increase is too large, there is a risk of mechanical damage to the tissue due to tearing of the structure or thermal damage due to insufficient dissipation of the generated heat. Therefore, it is possible to predefine a limit value for the relative value and control the light source so that the relative value does not exceed the limit value. For example, the limit value for the relative value may be between 1.1 and 2, preferably between 1.3 and 1.6.

[0011] Furthermore, it is possible to predefine a target value for the relative value and control the light source so that the relative value reaches the target value. The treatment may be terminated when the target value is reached, i.e., the light source can be controlled so that it no longer emits any light pulses. It is also possible to control the light source so that the relative value remains at the target value for a predefined time interval. Other variations are also possible, for example, the treatment may continue at a lower relative value after the target value has been reached. As an example, this can be achieved by decreasing 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 may be 1.05 to 1.5, preferably 1.1 to 1.3, and more preferably 1.15 to 1.25.

[0012] In one embodiment, a characteristic curve over time is predefined for relative values, and the light source is controlled so that the relative values ​​follow the characteristic curve.

[0013] The light source can be controlled so that light pulses are emitted with a constant energy. The time interval between light pulses may remain the same during treatment. However, it is also possible to modify the time interval during treatment to influence the progression of tissue vibration.

[0014] In different embodiments, a low-energy light pulse is delivered to the tissue at the start of treatment, and the energy is determined to be magnitude such that damage to the tissue is reliably prevented. The pulse energy may be increased throughout the course of treatment until a desired vibrational state is generated in the tissue. Using normalized relative values, it is possible to ensure that the amplitude does not increase to the extent that tissue damage occurs.

[0015] The device may have a closed control loop that controls the emission of light pulses so that the tissue vibration is set to a predefined amplitude. For example, it may be desirable to increase the amplitude at the start of treatment and then maintain it at a constant setpoint. The control signal to the light source may be designed to generate a constant setpoint.

[0016] It is also possible to predefine a characteristic curve for the amplitude of tissue vibration and control the light source by a closed control loop so that the amplitude is set according to the predefined characteristic curve. For example, a predefined characteristic curve for the increase or decrease of amplitude measurements over time may be predefined at the start of treatment or during the time interval of treatment. Control resulting from the course of treatment can be implemented in addition to, or as an alternative to, control over relative values.

[0017] The light source can be configured to deliver a number of similar light pulses to the tissue over the duration of treatment. The light pulses may have the same pulse duration. The light pulses may have the same pulse energy, and as a result, the same amount of energy is delivered to the tissue by each light pulse. Treatment with different light pulses for tuning to tissue vibrations is also possible, and in particular, the pulse duration and / or pulse energy and / or pulse repetition frequency can be controlled by a control unit over the duration of treatment. For example, the duration of individual light pulses may be 0.1 ns to 100 μs, preferably 10 ns to 2 μs.

[0018] The wavelength of light may include one, two, or three or more spectral regions that are absorbed to different degrees by the tissue in order to excite the tissue and cause it to vibrate to different degrees within different parts. The light source may be a laser light source that emits light in a strictly defined spectral region. In this case, the various spectral regions may include the entire spectrum from UV to the far-IR spectrum, for example, in the range of 300 nm to 3000 nm. Certain embodiments may include, for example, a laser emitting at the fundamental frequency and its two-harmonic components, for example, 1064 nm and 532 nm. Pulses of different wavelengths may be mixed synchronously or asynchronously in any desired sequence. A preferred variant for exciting vibrations is the alternating emission of light pulses, where the light pulses are in different spectral regions. The temporal pulse interval may be the same.

[0019] The light pulses may be emitted such 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 immediately following it. Preferably, the duration of the pause between two consecutive light pulses is at least 10 times, preferably 100 times, and more preferably 1000 times longer than the pulse duration.

[0020] The pause between two light pulses should not be so long that the tissue vibrations decay and return to their initial state during this time. Rather, it is desired that the sum of the introduced light pulses excites the tissue to vibrate continuously. Therefore, the interval between pulses should preferably be shorter than the thermal relaxation time of the excited tissue.

[0021] The treatment, as a whole, refers to a series of light pulses that induce continuous vibrational therapy of the tissue. If, after the tissue has returned to its initial state, another light pulse is directed at the tissue, this marks the start of a new treatment. The duration of the treatment is called the treatment period.

[0022] The present invention also includes an apparatus configured such that light pulses in the form of therapeutic pulses and light pulses in the form of measurement pulses are delivered to tissue during a treatment period. The therapeutic pulses may have a different spatial range than the measurement pulses. Different spatial ranges mean that the area covered on the tissue being treated is larger or smaller. In particular, the area covered by the therapeutic pulses may be larger than the area covered by the measurement pulses. As an example, to record the maximum amplitude of tissue vibration, the measurement pulses may be placed in the center of the treatment area. In addition to, or instead of, different spatial ranges, the measurement pulses and therapeutic pulses may also have different pulse durations and / or pulse repetition frequencies.

[0023] The control unit may be configured to process only the amplitude measurements of tissue vibrations caused by the measurement pulses, for the purpose of controlling the light source. One or more therapeutic pulses, with pulse duration and pulse energy adapted to the requirements of the treatment, may be sandwiched between the two measurement pulses in each case.

[0024] The device may include a measurement light source for generating measurement pulses, separate from the light source used for tissue treatment. The measurement pulses may be in a different spectral region than the therapy pulses. It is also possible to generate both the measurement and therapy pulses using the same type of light source.

[0025] The light source may be a laser light source. The beam path of the light source may be shaped so that a spot on the tissue is illuminated. The spot size, i.e., the diameter of the spot, may be selected based on the tissue being treated. When treating the retina of the eye, the spot size may be 50 μm to 500 μm, preferably 100 μm to 200 μm. In the case of the eardrum, the spot may have a size of, for example, 5 mm. For other tissues, such as subcutaneous nerve tissue, it is possible to operate with other spot sizes depending on the size of the treatment area, for example, a spot size of 2 mm to 20 mm, preferably 3 mm to 8 mm.

[0026] The radiation exposure from individual light pulses is, for example, 0.1 to 100 mJ / cm². 2 It may be less than the maximum radiation exposure of the tissue as specified in the European standard DIN-EN 60825-1. The duration of a single treatment may be 0.02s to 100s, preferably 0.05s to 10s, more preferably 0.1s to 1s. However, persistent vibrational excitation for modulated excitation of the eardrum, middle ear, or inner ear is also possible, for example. The number of light pulses during treatment may be 100 to 100,000. Treatment as a whole refers to a series of light pulses that result in continuous vibrational therapy of the tissue. If, after the tissue has returned to its initial state, another light pulse is directed to the tissue, this marks the start of a new treatment. All light pulses during treatment may be directed to the same area of ​​the tissue.

[0027] Tissue vibrations induced by light pulses can be thermoplastic expansion and contraction. Vibration sensors can be designed for the direct measurement of tissue expansion. For example, this is possible when the vibration sensor is an optical interferometer or an acoustic interferometer.

[0028] It is also possible to use vibration sensors to measure the sound waves emitted during vibration, their amplitude, and / or their spectra, and thus draw conclusions about the vibrational state of the tissue. Vibration sensors may include microphones, hydrophones, or piezoelectric elements that respond to pressure waves.

[0029] The present invention will be described in an exemplary manner based on the following preferred embodiments with reference to the accompanying drawings. In the latter part, the following will be shown.

Brief Explanation of Drawings

[0030] [Figure 1] An embodiment of the apparatus according to the present invention is shown. [Figure 2] A curve of vibrations caused by light pulses at the start of treatment is shown. [Figure 3] A view of FIG. 2 in the later stage of treatment is shown. [Figure 4] An alternative embodiment of the apparatus according to the present invention is shown. [Figure 5] Another alternative embodiment of the apparatus according to the present invention is shown. [Figure 6] Yet another alternative embodiment of the apparatus according to the present invention is shown. [Figure 7] The amplitude of tissue vibrations over the course of treatment is shown.

[0031] The apparatus according to the present invention shown in FIG. 1 comprises a laser light 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 by suitable optical elements 17. Each light pulse 15 induces vibrations in the form of thermoplastic expansion within the retinal tissue. The vibrations cause a pressure wave 22 that starts from the nerve tissue 19 and propagates. FIGS. 2 and 3 show exemplary curves of the pressure wave over time.

[0032] The apparatus comprises a vibration sensor 21 in the form of a hydrophone. The vibration sensor 21 reacts to the pressure wave 22 and emits 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 vibrations of the nerve tissue 19.

[0033] The electrical signal generated by the vibration sensor 21 is sent via line 23 as an amplitude measurement to the control unit 16, where it is processed. The first light pulse 15 is delivered to the nerve tissue 19 at the start of treatment, resulting in the generation of the first pressure wave 22, the amplitude of which is shown in Figure 2. The profile of the pressure wave 22 is registered using the vibration sensor 21. The associated amplitude measurement is stored in memory 24 as the initial amplitude measurement 26.

[0034] Furthermore, similar light pulses 15 are induced in the nerve tissue 19 at regular intervals throughout the course of treatment. Each light pulse 15 results in a new excitation of vibration in the nerve tissue 19. The vibration of the nerve tissue 19 decays during the pause between two light pulses 15 without completely decaying. Overall, the light pulses 15 result in continuous vibrational excitation of the nerve tissue 19. Figure 7 shows the time profile of treatment in an exemplary manner, where the horizontal axis represents time t and the vertical axis represents the amplitude of tissue vibration. The relative value 30 according to the present invention is determined by relating the current measurement of amplitude to the initial measurement of amplitude 26. The interval between light pulses is such that the tissue vibration does not completely decay during the treatment period 31.

[0035] The amplitude of the pressure wave 22 increases as a result of persistent excitation by a similar light pulse 15. Figure 3 depicts the pressure wave 22 at the end of the treatment shown in Figure 5. The amplitude measurement 27 is 50% larger than the initial amplitude measurement 26.

[0036] All amplitude measurements 27 obtained during treatment are guided to a control unit 16, where a relative value is formed by associating each amplitude measurement 27 with an initial amplitude measurement 26 stored in memory 24. The relative value is compared to a limit value in a comparator 25 of the control unit 16. As soon as the relative value reaches the limit value, the control unit 16 sends a stop signal to the light source 14, and as a result the light source 14 no longer emits light pulses 15. The limit value of the ratio (relative value) of the amplitude measurement to the initial amplitude measurement 26 is 1.5 in an exemplary embodiment, and therefore the limit value is reached when the amplitude measurement 27 is 50% higher than the initial amplitude measurement 26. In Figure 7, treatment is terminated when the limit value is reached. Subsequently, the nerve tissue reverts to its initial state of nerve tissue without vibration.

[0037] In the exemplary embodiment shown in Figure 4, the light source 14 preferably does not emit similar light pulses 15, but instead the pulse energy and / or intervals vary over the duration of the treatment. The apparatus includes an additional measurement light source 28 that guides measurement pulses 18 to nerve tissue 19 during pauses between therapeutic pulses 13 emitted by the light source 14. On the nerve tissue 19, the therapeutic pulses 13 cover a wider area than the measurement pulses 18. Only the pressure waves caused by the measurement pulses 18 are evaluated by the control unit 16, and only these are associated with the initial amplitude measurements 26 obtained using the measurement pulses 18 as well. In this way, the progression of the therapeutic pulses 13 can be harmonized with the need for treatment without compromising the measurements by the measurement pulses 18. After reaching the target amplitude, the pulse energy of the therapeutic pulses 13 is reduced so that the amplitude of the vibrations in the nerve tissue 19 remains constant for the remainder of the treatment.

[0038] In the embodiment shown in Figure 5, the light pulse 15 is similarly varied over the duration of the treatment. The memory 24 of the control unit 16 is used to store not only the initial amplitude measurement 26 but also the pulse energy of the first light pulse 15 that produced the associated pressure wave 22. Subsequent pressure waves are caused by light pulses 15 having different pulse energies, pulse durations, and / or pulse repetition rates. Before the amplitude value 27 is supplied to the comparator 25 for comparison with the initial amplitude measurement 26, the amplitude value 27 is normalized to pulse energy in component 38. A normalized relative value is generated, reproducing the ratio of the normalized pulse energy of the amplitude value 27 to the initial measurement 26, and representing the change in the state of the nerve tissue 19.

[0039] Figure 6 shows an alternative embodiment in which the amplitude of tissue vibration is measured using a vibration sensor 21 in the form of an optical sensor.

Claims

1. A device for treating biological tissue (19), comprising: a light source (14) for sending a number of light pulses (15) onto the tissue (19) during a treatment period (31) to cause the tissue (19) to vibrate; a vibration sensor (21) for measuring the amplitude of the vibration (22) of the tissue (19) caused by the light source (14); a control unit (16) for which a current measurement (27) of the amplitude is associated with an initial measurement (26) of the amplitude to form a relative value (30), and which uses the relative value (30) as an input value to generate a control signal for adjusting the pulse energy of the light pulses (15) of the light source (14).

2. The apparatus according to claim 1, characterized in that the control unit is configured to obtain a normalized relative value by associating the initial measurement value (26) of the amplitude with the pulse energy and associating the current measurement value (27) of the amplitude with the pulse energy.

3. The apparatus according to claim 1 or 2, characterized in that the target value of the relative value (30) is predefined, and the control unit (16) controls the light source (14) so ​​that the relative value (30) reaches the target value.

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

5.

5. The apparatus according to any one of claims 1 to 4, characterized in that a characteristic curve over time is predefined with respect to the relative value (30), and the control unit (16) controls the light source (14) using a closed control loop so that the relative value (30) follows the characteristic curve.

6. The apparatus according to any one of claims 1 to 5, characterized in that the control signal is integrated into a closed control loop in which the relative value is set to a predefined target value or a predefined time profile.

7. The apparatus according to any one of claims 1 to 6, characterized in that the light pulse (15) is guided to a spot on the tissue, and the spot has a diameter of 0.1 mm to 10 mm.

8. The apparatus according to any one of claims 1 to 7, characterized in that a first light pulse and a second light pulse are irradiated onto the tissue during a treatment period (31), and the spectral region of the first light pulse is different from the spectral region of the second light pulse.

9. The apparatus according to any one of claims 1 to 8, characterized in that, during the treatment period (31), an optical pulse (15) in the form of a measurement pulse (18) and an optical pulse (15) in the form of a therapy pulse (13) are delivered onto the tissue (19), the vibration sensor (21) measures the amplitude of tissue vibration caused by the measurement pulse (18), and these measured values ​​are processed by the control unit (16).

10. The apparatus according to claim 9, characterized in that the light pulse in the form of the therapeutic pulse (13) covers a larger area on the tissue (19) than the light pulse in the form of the measurement pulse (18).

11. The apparatus according to claim 9 or 10, characterized in that the light pulse in the form of the therapeutic pulse (13) is output in a spectral region different from that of the light pulse in the form of the measurement pulse (18).

12. The apparatus according to any one of claims 1 to 11, characterized in that the number of light pulses (15) during treatment is 100 to 100,000.

13. The apparatus according to any one of claims 1 to 12, characterized in that the vibration sensor (21) is designed to determine an amplitude measurement value (27) by using a pressure wave (22) caused by the vibration of the tissue (19).

14. The apparatus according to any one of claims 1 to 12, 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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