Laser system for surgical applications

Abstract

Laser system for surgical applications comprising: a solid-state laser; a pumping lamp for pumping said solid-state laser; a power supply for feeding said pumping lamp; said power supply comprising capacitors; a controller for regulating said power supply; said controller is configurated to control said power supply in order to feeding said pumping lamp with a first voltage and then with a second voltage; and wherein said controller is configurated to discharging said capacitors until reaching the second voltage smaller to said first voltage.

Description

[0001] “LASER SYSTEM FOR SURGICAL APPLICATIONS

[0002] DESCRIPTION

[0003] The present invention refers to a laser system for surgical applications.

[0004] Systems based on laser technology capable of producing peak power between 2kW - 10kW are to be considered ideal for application of fragmentation of upper urinary tract stones or prostatic enucleation, ensuring high efficacy. In contrast, high peak power induces excessive back-propulsion and numerous and voluminous fragmentations. Such solutions below 2kW peak power become unstable and unusable.

[0005] Systems with reduced peak power available today, based for example on fiber optic laser technology as active medium, have the advantage of reducing the back- propulsion of the calcined particle but in contrast are more inefficient systems on hard stones. For such systems it is currently not possible to increase the peak power output due to technological limitation of fiber optics as active medium.

[0006] It is well known that a system with a peak power such as the one proposed could be realized starting from a high peak power system in which the introduction of a beam splitter attenuator based on moving mirrors would allow the excess energy to be deflected ensuring the necessary range (0.5kW - 2kW) for the application of interest. This solution was not considered advantageous precisely because of the use of movable mirrors, which would require a major remake of the system's electronic control system to ensure proper emission synchronism.

[0007] The object of the present invention is to provide a laser system for surgical applications able to overcome the drawback of the known art.

[0008] According to the present invention, these objects and others yet are achieved by a laser system for surgical applications, and a method described in the appended claims. In an embodiment the laser system for surgical applications comprising: a solid-state laser; a pumping lamp for pumping said solid-state laser; a power supply for feeding said pumping lamp; said power supply comprising capacitors; a controller for regulating said power supply; said controller is configurated to control said power supply in order to feeding said pumping lamp with a first voltage and then with a second voltage; and wherein said controller is configurated to discharging said capacitors until reaching the second voltage smaller to said first voltage.

[0009] Said controller is configurated to discharging said capacitors according a relation between laser threshold lamp-on time and flash-lamp voltage.

[0010] Preferably, said solid-state laser release a laser beam having a first peak power having a first length time and a second peak power having a second length time.

[0011] Said first peak power is greater than said second peak power, and said first length time is smaller than said second length time.

[0012] Wherein the first peak power is comprised between 8kW and 12kW; the second peak power is comprised between 0.5kW and 2kW; the first length time is comprised between 80ps and 120ps; the second length time is comprised between 0.5ms and 2ms.

[0013] Preferably, said controller is configurated to discharging said capacitors energizing the pumping lamp at high frequency below the solid-state laser threshold.

[0014] In another embodiment there is the method for obtaining from a single laser source with a first operating mode and a second operating mode; wherein said first operating mode comprises the phase of providing a laser beam having a first peak power for a first length time; wherein said second operating mode comprises the phase of providing a laser beam having a second peak power for a second length time; the method changes from said first operating mode to said second operating mode by discharging the capacitors of the power supply for feeding a pumping lamp of a solid- state laser according to a relation between laser threshold lamp-on time and flashlamp voltage.

[0015] In the prior art, there is the absence of a single integrated solution that allows effective treatments capable of reducing fragmentation dust.

[0016] The solution proposed is a single laser source that can switch into two operating modes with extreme efficiency.

[0017] The present solution is based on the adjustment of some laser generation parameters such as, for example, the supply voltage or pumping power of the active medium pumping lamps.

[0018] It is capable of adjusting, depending on whether a mechanical or coagulative effect is desired, in a stable way the peak power and, consequently, the pulse duration.

[0019] This solution improves the state of the art since makes it easier for the user to obtain the desired effect maintaining the non-invasive nature of the treatment.

[0020] The solution proposed consists of a single laser system for surgical applications of the upper urinary tract and prostate, generally in the urological field, capable of generating mechanical pulses that can convert in rapid times to a laser source capable of generating coagulation pulses.

[0021] More in detail heart the solution proposed is to realize an adjustment of the power supply of the solid-state laser pumping lamp so that a mechanical pulse and a coagulative pulse can be generated starting from a high pulse power source.

[0022] The characteristics and advantages of the present invention will be apparent from the following detailed description of a practical embodiment thereof, illustrated by way of non-limiting example in the accompanying drawings, wherein: figure 1 shows, in a schematic way, two impulses of a laser system for surgical applications according to the present invention; figure 2 shows, in a schematic way, a laser system for surgical applications according to the present invention; figure 3 shows, in a schematic way, a supply voltage of a laser system for surgical applications according to the present invention; figure 4 shows a model of the relation between laser threshold lamp-on time and flashlamp voltage of a laser system for surgical applications according to the present invention; figure 5 shows, in a schematic way, the coupling of two a laser system for surgical applications according to the present invention.

[0023] In the process of prostate enucleation, the action of detachment of the gland occurs through the action of shock waves, thus by mechanical effect, generated by the radiation of a laser, with a solid-state laser having a Holmium-doped crystal as active medium with an electromagnetic radiation having a wavelength typically 2100 nm and preferably between 1900nm and 2200nm, which by emitting a first laser pulse, called mechanical pulses, having a first peak power of about 10kW and preferably between 8kW and 12kW and a first time duration t1 of about 100 ps and preferably between 80 ps and 120 ps, generate mechanical waves in the biological fluid, typically saline solution, in which the gland itself is immersed, which by colliding with the gland results in its detachment. A possible consequence of the generation of such waves is damage to the blood vessels contained in the tissues containing the fluid and the gland itself.

[0024] Such damage creates bleeding, which in addition to being risky for the patient colour the fluid making the prostate gland not visible to the operator. The solution to such damage is a coagulation action, which can be done by a second laser pulse, called coagulation pulses, having a second peak power between 0.5kW and 2kW, likewise a system having a laser energy less than or equal to 2 J, typically less than 1 J with an average power less than or equal to 30W typically less than 15W with emission wavelengths typically 1900nm - 2200nm and a second time duration t3 of about 1 ms and preferably between 0.5 ms and 2 ms.

[0025] It is possible to switch from one configuration to another, as better explained later, in a third time t2 typically less than or equal to 1 s. That is, the time t2 is the time from the first laser pulse and the second laser pulse.

[0026] The laser system 10 for surgical applications comprises a pump lamp 11 which excite a solid state laser 12 having a Holmium-doped crystal as active medium. The pulses are directed to the target through a silicon optical fiber 13 having a typical diameter of 200pm, more generally between 140pm and 1000pm.

[0027] The laser system 10 further comprises a voltage supply 15 with capacitors for supply the pump lamp 11 , and a controller 14 which supervise all the devices of the laser system 10.

[0028] The voltage supply 15 comprises an adjustable voltage generator 16 followed by a first switch 17 a capacitor bank 18 and a second switch 19. The controller 14 manages also these devices.

[0029] The proposed solution is to define, by appropriate measurements, the value of the pump power so that the system can generate a peak power as desired.

[0030] That is to have several values of the voltage to apply to the capacitors (which is equal to the pump power of the lamp) which corresponds to the several peak power. The dependency between the capacitor voltage and the laser peak power is preferably contained in calibration tables dedicated to the different peak power regimes. Then the energy of the laser is regulated by varying the pulse duration.

[0031] The operating mode would be to select via a display-controllable pump lamp voltage regulating device that then allows the operator to quickly select the desired working point and from this calibrate the peak power so as to also have a laser pulse duration in accordance with the formula T = Eset / Pp, depending on the type of application the operator desires. Wherein T is the laser pulse duration, Eset is the laser pulse energy set by the user and Pp is the laser pulse peak power.

[0032] Such adjustment of the pumping lamps is done by adjusting the charging voltage of the capacitors that must be properly discharged to change from the short pulse to long pulse configuration.

[0033] To discharge the capacitors, the pumping lamp is energized (closing the switch 18), one or more times, for a time shorter than the time of the laser trigger threshold. In this way it is possible to discharge the capacitors at the due voltage less than or equal to 1 s.

[0034] That is the transition from short pulse to long pulse is accomplished by inhibiting the charging module (opening the switch 16) and then energizing (closing the switch 18) the pumping lamp at high frequency so that the pumping lamp is turned on for a time than the solid state laser is not excited, that is below the laser threshold. Additionally for accelerating the discharge the capacitors, resistive discharge modules can be used in synergy.

[0035] Once the voltage in the capacitors is low, the lamp-on time is increased above the laser threshold until reaching the required energy and a long pulse is obtained.

[0036] In fact, by increasing or decreasing the supply voltage of the pumping lamp, it is possible to convert the device from a system capable of generating a first short pulse of a first high peak power to a system capable of generating a second long pulse of a second lower peak power.

[0037] For changing from the first operative mode (mechanical pulse) to the second operative mode (coagulative pulse), a reduced time is achieved without turning off the pumping lamp, which would greatly lengthen the above conversion time, but by having the capacitors discharged by generating lamp pulses below the laser emission threshold of the system. Once the voltage in the capacitors is low, the lamp-on time is increased so as to excite the laser and a long pulse is obtained.

[0038] A precise model of the relation between laser threshold lamp-on time and flash-lamp voltage (capacitors voltage) is implemented in the system and it allow a stable operation of the laser cavity in this condition.

[0039] A precise modelisation is required in particular at low voltage operation where the threshold becomes strongly non-linear. Thanks to the modelisation it is possible to control exactly the switch on time of the pump lamp in order to obtain the required energy of the laser pulse.

[0040] The model is constructed from the characterization of many laser cavities thus have a good generality, measuring at any voltage the time necessary to trigger the solid state laser. The mean value measured are memorized in a table or a interpolation curve is used.

[0041] In figure 4 is shown the curve wherein for each voltage V of capacitors there is the corresponding time t of the laser threshold. The curve can be represented by the formula t = k VMwherein k and p are parameter of the model.

[0042] The system will use the model during the discharge of the capacitors, to adjust the lamp pulse time just below threshold so that to use the maximum possible energy that does not generate laser radiation and in the setting of the laser pulse energy (that is proportional to the duration of the lamp pulse above the threshold), to precisely adjust the lamp pulse duration.

[0043] Further, knowing precisely the value of the threshold pulse duration allows to precisely adjust the lamp pulse needed to obtain the required energy.

[0044] The model is used in order to choose, at the best way, the time (for each working voltage) for switch on the pump lamp to maintain the laser over or above threshold.

[0045] The time is chosen to maintain the laser just below threshold for discharge the capacitors more quickly as possible or is chosen to maintain the laser above threshold for excite the laser and deliver the right laser pulse, in particular with the second long pulse, wherein the non linearity at the low voltage operation make it difficult to drive correctly the laser.

[0046] The model, placed inside a microcontroller, that is a model that simulate the best fit of the trend of the threshold versus the lamp voltage, is implemented in the control electronics of the system.

[0047] An alternate way to obtain a low peak power effective pulse, is to slice the main pulse, obtained as above, in 2 to 10 sub-pulses (with 1 / 2 to 1 / 10 the energy of the global pulse), with a pause in between the sub-pulses, without changing the voltage settings of the flashlamp. The pulse duration will be between 10 ps to 500 ps and the pause duration will be between 10 ps and 1 ms. This solution will be usable especially in the coagulation of the soft tissues since does not require the time to discharge the capacitors.

[0048] In order to increase the repetition rates, it is possible to use two or more laser system 10 as above.

[0049] The laser output of the laser systems 10 are combined with each other either through two reflective optics 22, as dielectric mirror with a board reflectivity angle and a galvanometer mirror 23, or through two optical fibres, in a photodiode 24 which measures and records their pulse energy. The signal read by the photodiode 24 is sent, through an analog to digital converter to a microcontroller 25.

[0050] The microcontroller 25 manages the two laser systems 10 in a way so as to interlace the two laser output and achieve shorter timing of the output pulses.

[0051] In particular, the microcontroller 25 can cause the first laser pulse to be emitted by one of the two laser systems 10 and can cause the second laser pulse to be emitted by the other of the two laser systems 10, close to each other in order to reduce the time t2 between the first laser pulse and the second laser pulse.

Claims

CLAIMS1 . Laser system for surgical applications comprising: a solid-state laser; a pumping lamp for pumping said solid-state laser; a power supply for feeding said pumping lamp; said power supply comprising capacitors; a controller for regulating said power supply; said controller is configurated to control said power supply in order to feeding said pumping lamp with a first voltage and then with a second voltage; and wherein said controller is configurated to discharging said capacitors until reaching the second voltage smaller to said first voltage.

2. Laser system according to claim 1 wherein said controller is configurated to discharging said capacitors according a relation between laser threshold lamp- on time and flash-lamp voltage.

3. Laser system according to claim 1 wherein said solid-state laser release a laser beam having a first peak power having a first length time and a second peak power having a second length time.

4. Laser system according to claim 1 wherein said first peak power is greater than said second peak power, and said first length time is smaller than said second length time.

5. Laser system according to claim 1 wherein said first peak power is comprised between 8kW and 12kW.

6. Laser system according to claim 1 wherein said second peak power is comprised between 0.5kW and 2kW.

7. Laser system according to claim 1 wherein said first length time is comprised between 80ps and 120ps.

8. Laser system according to claim 1 wherein said second length time is comprised between 0.5ms and 2ms.

9. Laser system according to claim 1 wherein said controller is configurated to discharging said capacitors energizing the pumping lamp at high frequency below the solid-state laser threshold.

10. Method for obtaining from a single laser source with a first operating mode and a second operating mode; wherein said first operating mode comprises the phase of providing a laser beam having a first peak power for a first length time; wherein said second operating mode comprises the phase of providing a laser beam having a second peak power for a second length time; the method changes from said first operating mode to said second operating mode by discharging the capacitors of the power supply for feeding a pumping lamp of a solid-state laser according to a relation between laser threshold lamp-on time and flash-lamp voltage.

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