CN116490743A - Apparatus and method for enhancing the efficacy of a laser beam in a liquid medium - Google Patents

Abstract

The present disclosure relates generally to the field of laser-based medical devices. In particular, but not exclusively, the present disclosure relates to apparatus and methods for enhancing the efficacy of a laser beam in a liquid medium. In many embodiments, the laser pulses are modulated based on bubble dynamics to improve energy delivery to the target spot. Various exemplary pulsing schemes are described, including a decrease in modulating pulse power during exponential bubble expansion and an increase in modulating pulse power during exponential bubble collapse.

Description

Apparatus and method for enhancing the efficacy of a laser beam in a liquid medium

Cross-reference to related art

The present application claims priority from U.S. patent application Ser. No.63/118,117, entitled "Apparatus and Method for Enhancing Laser Beam Efficacy in a Liquid Medium," filed on even 25 th month 11 in 2020, which is incorporated herein by reference in its entirety.

The present application claims priority from U.S. patent application No.63/118,857, entitled "Method and System For Estimating Distance Between a Fiber End and a Target," filed on even 27 at 11/2020, c. ≡119, the entire contents of which are incorporated herein by reference.

The present application claims priority from U.S. patent application Ser. No.63/252,830, entitled "Method and System For Estimating Distance Between a Fiber End and a Target," filed on 6/10/2021, 35 U.S. C. ≡119, the entire contents of which are incorporated herein by reference.

Technical Field

The present disclosure relates generally to the field of laser-based medical devices. In particular, but not exclusively, the present disclosure relates to apparatus and methods for enhancing the efficacy of a laser beam in a liquid medium.

Background

Lasers are widely used to perform a variety of medical treatments, such as tissue coagulation, ablation, cutting, fragmentation, dusting, and enucleation. Laser treatment is performed through and in a variety of media and environments, such as gases, solids, and liquids. During laser treatment, the interaction between the laser radiation and the target object (e.g., body tissue such as prostate, kidney, or urinary stones) depends on the laser light used, as well as the absorption, reflection, and dispersion of the environment and the target object. Ureteral stones, kidney stones or the prostate are just three examples of common targets that can be treated by laser. Typically, the treatment environment may be saline or other similar liquid. The efficiency of laser therapy may be a function of the interaction between the laser energy and the target. The fraction of the laser energy that reaches and is absorbed by the target contributes to the desired surgical effect. However, the laser energy absorbed by the ambient medium can be considered as lost energy, which is no longer available for target treatment. Generally, laser parameters, such as wavelength, can be selected based on the desired clinical effect and characteristics of the target. For example, infrared (IR) lasers, such as holmium or thulium, may be used for laser lithotripsy to treat ureteral stones, renal colic, and prostate ablation or enucleation.

Disclosure of Invention

This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to necessarily identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

In one aspect, the present disclosure is directed to a system including a fiber laser and a controller. The controller may include a processor and a memory. The memory may include instructions that when executed by the processor cause the processor to perform one or more of: determining pulse energy for a fiber laser; identifying a distance between a tip of the fiber laser and the target point, wherein the liquid is located between the tip of the fiber laser and the target point; determining a modulation scheme based on the distance; setting an initial pulse power for the modulation scheme to generate an exponential bubble in the liquid based on the distance; and initiating a pulse via the fiber laser according to a modulation scheme, wherein the modulation scheme reduces the power of the pulse after initiating the pulse at the initial pulse power.

In some embodiments, the modulation scheme increases the power of the pulse to a maximum system power level at a time estimated for the exponential bubble to reach a maximum size. In some such embodiments, the instructions, when executed by the processor, further cause the processor to estimate a time for the index bubble to reach a maximum size based on the initial pulse power and an absorption coefficient of the liquid at a wavelength of the fiber laser.

In various embodiments, the instructions, when executed by the processor, further cause the processor to identify an updated distance between the tip of the fiber laser and the target point; and determining an updated modulation scheme based on the updated distance.

In various embodiments, the modulation scheme is configured to modulate the pulse power down during inflation of the exponential bubble and modulate the pulse power up during collapse of the exponential bubble.

In many embodiments, the modulation scheme includes an initial modulation frequency and instructions that when executed by the processor further cause the processor to determine the initial modulation frequency based on a time at which the exponential bubble collapses, a time at which the exponential bubble reaches a maximum size, and a time from initiation of the lasing to start of bubble formation.

In some embodiments, the instructions, when executed by the processor, further cause the processor to set an initial pulse power for the modulation scheme to generate an exponential bubble in the liquid based on the distance and the pulse energy.

In various embodiments, the instructions, when executed by the processor, further cause the processor to integrate the power of the pulse with respect to time and terminate the pulse when the integration of the power of the pulse with respect to time equals the pulse energy.

In various embodiments, the instructions, when executed by the processor, further cause the processor to classify the target as a distant target based on the distance, and set the initial pulse power to a maximum system power level based on classifying the target as distant. In each such embodiment, the modulation scheme is configured to obtain the resonance effect by cycling through a period between 0.7 and 1.3 times the time from the start of the exponential bubble to collapse.

In another aspect, the present disclosure is directed to at least one non-transitory computer-readable medium comprising a set of instructions that, in response to execution by a processor circuit, cause the processor circuit to perform one or more of: determining pulse energy for a fiber laser; identifying a distance between a tip of the fiber laser and the target point, wherein the liquid is located between the tip of the fiber laser and the target point; determining a modulation scheme based on the distance; setting an initial pulse power for the modulation scheme to generate an exponential bubble in the liquid based on the distance; and initiating a pulse via the fiber laser according to a modulation scheme, wherein the modulation scheme reduces the power of the pulse after initiating the pulse at the initial pulse power.

In some embodiments, the modulation scheme increases the power of the pulse to a maximum system power level at a time estimated for the exponential bubble to reach a maximum size. In some such embodiments, the set of instructions, in response to execution by the processor circuit, further cause the processor circuit to estimate a time taken for the index bubble to reach a maximum size based on the initial pulse power and an absorption coefficient of the liquid at a wavelength of the fiber laser.

In various embodiments, the set of instructions, in response to execution by the processor circuit, further cause the processor circuit to: identifying an updated distance between the tip of the fiber laser and the target; and determining an updated modulation scheme based on the updated distance.

In various embodiments, the set of instructions, in response to execution by the processor circuit, further cause the processor circuit to set an initial pulse power for the modulation scheme to generate an exponential bubble in the liquid based on the distance and the pulse energy.

In many embodiments, the set of instructions, in response to execution by the processor circuit, further cause the processor circuit to integrate the power of the pulse with respect to time and terminate the pulse when the integration of the power of the pulse with respect to time equals the pulse energy.

In yet another aspect, the present disclosure may include a method comprising one or more of: determining pulse energy for a fiber laser; identifying a distance between a tip of the fiber laser and the target point, wherein the liquid is located between the tip of the fiber laser and the target point; determining a modulation scheme based on the distance; setting an initial pulse power for the modulation scheme to generate an exponential bubble in the liquid based on the distance; and initiating a pulse via the fiber laser according to a modulation scheme, wherein the modulation scheme reduces the power of the pulse after initiating the pulse at the initial pulse power.

In some embodiments, the method includes modulating the pulse power down during inflation of the exponential bubble and modulating the pulse power up during collapse of the exponential bubble.

In various embodiments, the method includes classifying the target as a distant target based on the distance, and setting the initial pulse power to a maximum system power level based on classifying the target as distant. In various such embodiments, the method comprises cycling through a period between 0.7 and 1.3 times the time from the start of the exponential bubble to collapse.

Drawings

Non-limiting embodiments of the present disclosure are described by way of example with reference to the accompanying drawings, which are schematic and are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated is typically represented by a single numeral. It will be appreciated that various figures included in the disclosure may omit some components, illustrate portions of some components, and/or present some components as transparent to facilitate illustration and description of components that may otherwise appear hidden. For purposes of clarity, not every component is labeled in every drawing nor is every component of every embodiment shown where illustration is not necessary to allow those of ordinary skill in the art to understand the disclosure. In the figure:

Fig. 1 shows an exemplary diagram of pulses of a holmium laser and a thulium laser according to one or more embodiments described herein.

Fig. 2A and 2B illustrate various aspects of a holmium laser short pulse in different media according to one or more embodiments described herein.

Fig. 3A and 3B illustrate various aspects of a thulium laser long pulse in different media according to one or more embodiments described herein.

Fig. 4A illustrates an exemplary diagram of a thulium laser long pulse in an air medium according to one or more embodiments described herein.

Fig. 4B illustrates an exemplary diagram of a thulium laser long pulse in a liquid medium according to one or more embodiments described herein.

FIG. 5 illustrates an exemplary time series image of bubble dynamics in accordance with one or more embodiments described herein.

Fig. 6 illustrates an exemplary plot of laser power modulation as a function of bubble size in accordance with one or more embodiments described herein.

FIG. 7 illustrates an exemplary diagram of modulated and unmodulated laser pulses in conjunction with associated bubble dynamics according to one or more embodiments described herein.

FIG. 8 illustrates an exemplary diagram of modulating laser pulses in combination with associated bubble dynamics in accordance with one or more embodiments described herein.

Fig. 9 illustrates an exemplary laser system in accordance with one or more embodiments described herein.

FIG. 10 illustrates an exemplary process flow according to one or more embodiments described herein.

FIG. 11 illustrates a block diagram of a method for implementing an embodiment consistent with the present disclosure.

FIG. 12 illustrates a block diagram of an exemplary computer system for implementing embodiments consistent with the present disclosure.

Detailed Description

The present disclosure provides medical devices and techniques for enhancing the efficacy of a laser beam in a liquid medium, such as for a desired surgical effect on a target site. Many therapeutic environments have a liquid environment that tends to absorb a significant portion of the laser energy. For example, the liquid medium can absorb and attenuate laser energy, leaving less energy available for the desired surgical effect on the target. In addition, the energy absorbed by the liquid medium heats the surrounding tissue, causing unnecessary safety problems and the need to flush the area with cooling liquid.

One laser treatment technique (referred to herein as the bubble path effect) utilizes one or more bubbles as a gas path for laser energy to pass from the laser fiber tip to the target site. The resulting gas passages have a smaller absorption coefficient than the liquid passages. The bubble path effect is described in more detail in U.S. patent application Ser. Nos. 15/927,143, 16/177,800, and 15/861,905, which are incorporated herein by reference. However, as will be described in more detail below, bubble dynamics introduce a number of challenges in establishing and maintaining a gaseous pathway between the laser fiber tip and the target spot to improve laser beam efficacy.

Accordingly, one aspect of the present disclosure is to optimize the available laser energy to treat a target based on enhanced bubble path effects for the target, as will be discussed in more detail below. The amount of energy required to create the bubble path effect (i.e., create an air tunnel between the tip of the optical (or laser) fiber and the target) is also a function of the distance between the fiber tip and the target. Thus, another aspect of the present disclosure is to reduce the amount of laser energy that may be wasted to create a bubble path effect for a particular distance to a tissue target, and thus increase the amount of laser energy available to treat the target. Yet another aspect of the present disclosure is to increase the distance of the bubble path effect and reach targets farther from the laser fiber tip for a particular laser energy. Utilizing the present disclosure may result in less wasted energy in treating tissue at a given distance or allow tissue at a greater distance from the tip of the laser fiber to be treated at a given energy level.

In some bubble path effect techniques, a first laser pulse may be provided to create a first bubble through which a second laser pulse is provided through the bubble after a predefined time delay. The second laser pulse is transferred with reduced absorption due to the first gas bubble (and the relative absence of fluid) and reaches the tissue with higher energy than a single laser pulse passing through the liquid medium only. Furthermore, the energy of the first and second pulses and the time delay between the two pulses may be varied to achieve higher energy delivery to tissue present at different distances from the tip of the laser fiber.

Infrared lasers, such as holmium (Ho) lasers having a wavelength of 2100nm and thulium (Tm) lasers having a wavelength in the range of 1940nm to 1970nm, are strongly absorbed in liquid environments. For example, photons at 1940nm have an absorption coefficient of 110[1/cm ], and photons at 2100nm have an absorption coefficient of 25[1/cm ]. Typically, in a liquid environment, many photons generated by a holmium laser are absorbed before the laser pulse travels a distance of 0.5mm from where it exits the fiber, while photons generated by a thulium laser are absorbed before the laser pulse travels a distance of 0.1mm from where it exits the fiber. In contrast, solid-state holmium lasers are characterized by high peak power and relatively short pulses, while thulium fiber lasers (Thulium fiber laser, TFL) are characterized by lower peak power. Thus, TFL requires a longer time to generate an equivalent amount of energy than a solid-state holmium laser. For example, TFL will generate 0.5 joules of energy in a pulse duration of about 1 millisecond (ms), while a solid state holmium laser requires about 0.2ms to generate the same amount of energy. As will be discussed further below, a single bubble life cycle has been observed to last from about 0.2 to 0.3ms. Moreover, it has been observed that the bubble, once initiated, has its own dynamic characteristics, which are in many ways independent of the laser pulse (except for the initial characteristics of the pulse in a very short time frame of tens of microseconds). Based on the above, a short solid-state holmium laser pulse may end before the bubble will reach its maximum size, while a longer TFL pulse will last for 3-4 bubble life cycles. The above-mentioned incorporated references describe how to optimize the timing and energy distribution between the first and subsequent laser pulses to minimize the energy put in the bubble creation and maximize the amount of energy reaching the target spot. In addition, holmium lasers with reduced peak power can be used to extend the usual short pulse duration.

However, propagating holmium laser pulse energy over a longer pulse duration, as in the thulium pulse described above, may result in a pulse duration longer than the life cycle of a single bubble. As in the case of thulium, laser pulses with longer life cycles than a single bubble can produce a cascade of bubbles. The cascade of multiple bubbles can create a gaseous pathway to the target. However, such a cascade of bubbles is characterized by a series of individual bubbles that expand and collapse at different times and at different locations along the pathway. As a result, the effective length of the gaseous pathway varies with time. At different times and places, the gaseous discontinuities along the path are filled with energy absorbing liquid, and this will again increase the attenuation of the pulses generated by the laser. As a result, the energy delivered to the target is frequently interrupted in an unpredictable manner during the collapse of these bubbles, resulting in multiple sub-pulses during the pulse duration and significant waste of energy.

Accordingly, one or more embodiments described herein provide for effectively and efficiently managing laser energy levels along long laser pulses. In various embodiments, effective and efficient management of laser energy during long laser pulses may provide one or more of the following advantages: (i) an increase in laser energy delivered to the target at a given distance, (ii) a decrease in laser energy loss when establishing a gaseous pathway to the target, and (iii) stabilizing the pathway during pulsing, rather than being subject to random collapse with unpredictable energy transfer results. Many embodiments optimize the energy distribution along long laser pulses.

The various embodiments described herein provide for reducing or preventing heat accumulation in surrounding tissue by more effectively delivering laser energy to a target site at a lower energy level to achieve the same level of treatment. For example, laser energy may be delivered to the target site at 30W instead of 40W while achieving the same level of treatment. Many embodiments may generate pulses that optimize energy delivery through an aqueous environment. In many such embodiments, the optimized pulses, when formed, may be used to obtain one of the following benefits: (1) Using the same pulse energy to deliver more energy to the target at a given distance, resulting in faster/stronger desired effects on the tissue, such as rupture, dusting, bursting, etc. (improved efficiency/efficacy); and (3) using lower pulse energy to achieve the same desired effect as having higher pulse energy, thereby reducing undesired side effects and adverse consequences such as overheating of surrounding tissue (improved safety profile).

In some embodiments, lasers with low peak power and long pulses, such as TFL, may be utilized such that the overall size and stability of the generated bubble cascade is much longer (along the fiber axis from the laser fiber short to the target) than the individual bubbles of a typical short pulse laser. Thus, and unexpectedly, even though Tm photons have a much stronger absorption in water than Ho, when comparing short pulses Ho with long pulses Tm, the latter travel farther as they travel through longer bubble strings generated by TFL. Furthermore, longer pulse durations make better use of bubble cascading, as the pulses persist as the bubbles reach the target. However, although it has been observed that the TFL pulse is broken into multiple sub-pulses due to multiple bubble collapse, resulting in a large variation in energy delivery during the pulse duration, the Ho laser energy may produce similar energy delivery.

As mentioned above, the bubble has its own dynamics and once initiated is in many ways no longer related to the characteristics of the laser pulse. The initial bubbles formed by lasing grow first to a maximum size (depending on the initial peak power of the pulse) and then collapse. Typical bubble duration for holmium lasers is 200-300[ mu ] s. The laser pulse, which is longer than the life cycle of the bubble, creates a series of multiple bubbles that emanate from the laser fiber tip toward the target.

Fig. 1 shows an exemplary plot 100 of pulses of a holmium laser and a thulium laser according to one or more embodiments described herein. In the illustrated embodiment, the holmium and thulium lasers have equal energies of 0.2 joules. Graph 100 shows a typical high peak power holmium laser short pulse versus a low peak power quasi-continuous thulium long pulse. The graph 100 includes bubble size on the positive y-axis 102 (with potential target location at line 112), pulse power on the negative y-axis 104, and time on the x-axis 106. With respect to high peak power holmium laser short pulses, region 118 corresponds to pulse power, curve 108 corresponds to the created bubble, and line 114 corresponds to the effective distance the laser pulse travels through the liquid. With respect to low peak power quasi-continuous thulium long pulses, region 120 corresponds to pulse power, curve 110 corresponds to the created bubble, and line 116 corresponds to the effective distance that the laser pulse travels through the liquid.

In both cases, after a short delay of about several tens of microseconds (μs), subsequent to the initiation of the laser pulse, a bubble is created and begins to expand. In both cases, once created, the life cycle of the bubble appears to have its own internal dynamics, which is not only related to the laser pulse, but also the internal vapor pressure generated at the bubble nucleation site, which in turn may depend on absorption, instantaneous peak power, laser beam quality, and/or the presence and number of air pockets within the liquid.

The expansion of the bubbles takes time. In the case of a holmium pulse, the gas bubble reaches its maximum size well after the highest power peak of the laser, and in the case of a thulium laser, the gas bubble reaches its maximum size during the laser pulse. As also shown in fig. 1, for an exemplary target distance 112 (positioned at a distance of about 3 mm), the effective distance that a thulium laser pulse can travel through liquid 114 is much longer than the effective distance that a holmium laser pulse can travel through liquid 116. The various embodiments described herein take advantage of the independent dynamics of bubbles in order to optimize energy distribution using long pulses.

Fig. 2A and 2B illustrate exemplary graphs 200A, 200B of holmium laser short pulses in different media according to one or more embodiments described herein. Fig. 2A corresponds to an air medium and includes a graph 200A of pulse power measured from a distance of 3mm in the air medium over time 202. Fig. 2B corresponds to a liquid medium and includes a graph 200B of pulse power measured from a distance of 3mm in the liquid medium over time 206. In addition, FIG. 2B includes a time-series image of bubble dynamics 204 corresponding to and displayed in synchronization with graph 200B. In each case, a sensor placed in the air or water path may be used to sense and record the pulse power over time.

In the illustrated embodiment, the time series of images of bubble dynamics 204 are captured using a high speed camera. As shown in the time series image of bubble dynamics 204, a single exponential bubble is initiated after a short delay after the start of the laser pulse. As also shown in fig. 2B, the larger the bubble, the higher the amount of laser power that reaches the target, which is the sensor in the present exemplary laboratory setup. When the bubble size (or bubble tunnel size) meets or exceeds the distance to the target, the target experiences maximum energy, resulting in only air between the fiber tip and the target. Once the bubble begins to collapse, less laser power can reach the target. As also shown in fig. 2B, the bubble life cycle is longer than the laser pulse duration.

Fig. 3A and 3B illustrate exemplary graphs 300A, 300B of thulium laser long pulses in different media according to one or more embodiments described herein. Fig. 3A corresponds to an air medium and includes a plot 300A of pulse power measured from a distance of 2mm in the air medium over time 302. Fig. 3B corresponds to a liquid medium and includes a plot 300B of pulse power measured from a distance of 2mm in the liquid medium over time 306. In addition, FIG. 3B includes a time-series image of bubble dynamics 304 corresponding to and displayed in synchronization with graph 300B. In fig. 3A and 3B, the pulse power over time 302, 306 may correspond to an exemplary long pulse of a 0.2 joule thulium laser. In each case, a sensor placed in the air or water path is used to sense and record the pulse power over time.

Fig. 3A and 3B show very different behavior of long laser pulses as opposed to the short laser pulses of fig. 2A and 2B. Surprisingly, as shown in fig. 300B, the target spot in this case undergoes two separate effective laser pulses 308a and 308B, although only a single long laser pulse is generated. The dynamics of the bubble cascade may provide an explanation. Only after the gaseous pathway is sufficiently close to the target is some energy reached (in the case of Tm, most of the energy is absorbed by the water within 0.1 mm). Furthermore, the gaseous pathway takes time to get close enough to the target and during this time no laser power reaches the target. Instead, the laser power is absorbed mainly by the liquid on its way to the target. As previously mentioned, the energy absorbed by the liquid is not available for the treatment target and may be converted into unwanted heating of the surrounding tissue.

As compared to fig. 2A and 2B, it takes more time for the gaseous pathway to expand close enough to the target and for energy to reach the target due to the lower peak power. Moreover, in the case of a thulium laser that is more water-absorbed than holmium, the rising profile (and the falling time) of the laser light experienced by the target spot is much steeper than it is in the holmium case, as can be understood by comparison of figures 200B and 300B. Many of the embodiments described herein can utilize a predetermined pulse energy and distance to the target to control and optimize power modulation along the pulses so that more laser power is available during the effective pulses experienced by the target and less laser power is lost between the effective pulses. In many such embodiments, the user may select the pulse energy.

Referring now to the time series of images of bubble dynamics 304 of FIG. 3B, the plurality of images (or frames) of the time series are numbered from left to right 1-23. More specifically, frame #1 shows the tip of the fiber prior to the initiation of the laser pulse. Once the laser pulse begins, an exponential bubble, shown as frame 2, begins to grow relatively spherically at the fiber tip. As this exponential bubble continues to grow, it can be seen in frames 3 and 4 and at its leading edge, the second bubble starts to grow in a forward direction. Further, since such second bubbles are extensions of the exponential bubbles, the high pressure inside the exponential bubbles shapes the second bubbles into a more cylindrical shape. Further, as pressure is vented from the exponential bubble into the second bubble, the exponential bubble expands and decreases. As a result of both processes, most of the internal pressure in both bubbles expands mainly forward towards the target, as can be seen in frames 5-7.

At this stage, according to an example, the gaseous pathway has reached a sufficiently close target to subject the target to laser power. Another aspect of the present disclosure is to generate an exponential bubble, generate a second bubble at the leading edge of the exponential bubble, and let the exponential bubble spontaneously expand and shape the second bubble while the modulated laser pulse power drops to a level lower than that required to initiate the exponential bubble during that time. Furthermore, the exponential bubbles at the tip of the fiber tend to collapse and potentially degrade the tip of the fiber itself. As a result, the laser beam quality and the treatment efficiency may be reduced. The higher the laser power during initiation of the index bubble, the higher the internal pressure inside the index bubble and the stronger the cavitation effect on the fiber tip once the index bubble collapses. Thus, in embodiments of the present disclosure, the minimum laser power required to initiate an exponential bubble is used, followed by a decrease in laser power during expansion of the exponential bubble, with the laser power again being increased only after the exponential bubble begins to collapse to further build additional bubbles and a gaseous pathway to the target. Reducing cavitation effects on the fiber tip can delay its degradation.

Referring now to frame 9, it can be seen that the exponential bubble begins to collapse and the second bubble collapses and moves away from the collapsed exponential bubble. As seen in the next frame 10, the fluid fills the gaps between the separated bubbles, and the collapsed second bubbles, and the collapsed index bubbles. As a result, the target begins to experience reduced laser power until no energy reaches the target around frame 11. Further, in frame 10 and more clearly in frame 11, another index bubble is initiated and begins to expand at the tip of the fiber. At this stage, a similar process as described above with respect to frames 1-5 occurs, where the gaseous pathway must be reestablished, and only when the pathway reaches a sufficiently close target, it begins to undergo exposure to laser power again in about frame 16.

Thus, many of the embodiments described herein can modulate the laser power drop once an exponential bubble has been initiated and during the establishment of a gaseous pathway to the target. Many such embodiments thus optimize the energy distribution along the long pulse to make the bubble path effect more efficient in the individual life cycles of the bubble.

Fig. 4A-4B and 5 illustrate various aspects of thulium long laser pulses according to one or more embodiments described herein. More specifically, fig. 4A shows an exemplary graph 400A of a thulium laser long pulse having a time-varying pulse power in an air medium; FIG. 4B shows an exemplary graph 400B of a thulium laser long pulse having a pulse power in a liquid medium that varies over time; and FIG. 5 illustrates an exemplary time series of images corresponding to bubble dynamics 500 of graph 400B.

Referring to fig. 4A, a pulse power 402 in an air medium that is about 1ms in duration and that generates a long thulium laser pulse of 0.5 joules over time from a distance measurement of 2.5mm is shown in graph 400A. The corresponding measurements in the liquid medium are shown in graph 400B. The pulses of fig. 4A and 4B are longer than those shown in fig. 3A and 3B. Thus, the target spot experiences 4 effective laser "sub-pulses" 406a, 406B, 406c, 406d, as shown in FIG. 4B, as opposed to the two effective laser "sub-pulses" 308a, 308B discussed with respect to FIG. 3B. As previously described and as shown in fig. 4A, the laser is quasi-continuously on for about 1ms. In practice, however, the target in this example experiences four separate laser sub-pulses 406a, 406b, 406c, 406d. These four separate effective laser pulses 406a, 406b, 406c, 406d are the result of the creation and destruction of the gaseous pathway during the time the laser is on. The various embodiments described herein can modulate the power drop of the laser during the time that the gaseous pathway is being constructed, allowing for spontaneous expansion of the bubble, and save laser energy until the gaseous pathway is sufficiently close to the target tissue. Furthermore, when the gaseous pathway is sufficiently close to the target, embodiments can modulate the laser power rise and utilize the gaseous pathway to bring a greater amount of laser power to the target.

Providing further laser energy during the expansion of the bubble may waste energy because the bubble will not grow further in size during the initial pulse energy is applied, as this will mean "pushing air" within the bubble. In other words, there may be no further absorption within the bubble after the bubble begins to expand. To increase the size of the bubble until the target is reached, the laser energy is only consumed in the presence of liquid in the path from the tip of the laser fiber to the target, and the resulting absorption is converted to pressure, which re-expands the bubble. Then, when the gaseous pathway begins to break down and a liquid bridge is formed between the separated gas pockets, the modulated laser power is again reduced until the next opportunity to deliver higher laser power to the target through another effective gaseous pathway. Fig. 5 shows an image of bubble cascade dynamics discussed above with respect to fig. 4B.

Thulium Fiber Lasers (TFLs) are typically pumped by diode lasers to create long pulses. In addition, TFL produces long pulse conditions. Accordingly, one or more embodiments described herein may utilize the fact that the time constants associated with bubble formation, initiation, expansion, and collapse are shorter than the laser pulse length to modify the pulse power during long laser pulses. In contrast, short pulse lasers are typically pumped by a flash lamp, which itself operates in a very short pulse regime. The short pulse laser operates in a domain in which the bubble life cycle is longer than the laser pulse length. However, the embodiments described herein provide various lasers that are arranged to emit light having a high absorption coefficient in the relevant liquid and that can generate pulses longer than the lifetime of the gas bubbles, and further that can be modulated up and down. For example, one or more of yttrium aluminum garnet (Yttrium Aluminum Garnet, YAG), erbium, holmium, and other IR diodes or solid state lasers may be modulated up and down in accordance with the present disclosure without departing from the scope.

Various embodiments described herein may utilize the distance between the tip of the optical fiber and the target point to determine the mode of operation. For example, there may be two (or more) different scenarios or settings that may be selected based on the distance from the fiber tip and target point (typically automatically selected by the laser system). In a first example scenario, an exponential bubble expands to a sufficiently large distance and is sufficiently close to a target point to deliver laser energy. In a second example scenario, the expansion of the index bubble alone is not sufficient to be close enough to the target, and at least a second bubble is required to further expand the gaseous pathway before the target may be treated. In a first scenario, and in accordance with the present disclosure (see, e.g., the various V-shaped techniques described below), once an exponential bubble is created, the power of the laser is modulated downward until the exponential bubble is sufficiently close to the target point. Once the index bubble is close enough to the target, the power of the laser is modulated upward to treat the target. In a second scenario, and in accordance with the present disclosure (see, e.g., the various resonant modulation techniques described below), once an exponential bubble is generated, the laser power is modulated downward, and once the second or third bubble reaches the target it is modulated upward again to treat the target, and when the gaseous pathway begins to collapse, the laser power is modulated back.

As discussed above, different wavelengths and types of laser emissions have different absorption coefficients in a liquid operating environment. Thus, "close enough" to the target is a function of the laser light and may represent different distances for different lasers. As discussed above with respect to fig. 3B and 4B, the slope of the rising profile of the effective laser pulse experienced by the target spot is also a reflection of this distance. For example, thulium lasers absorb more strongly in liquids than holmium lasers. Thus, the target may begin to experience some laser power impact only when the gaseous pathway approaches the magnitude that thulium laser photons can travel in the liquid to the distance to the target. However, since holmium laser photons can travel longer distances in the liquid environment than thulium, the slope of the rising effective laser pulse is less steep. Thus, for thulium lasers, the distance to the target is sufficiently shorter than for holmium lasers. As the present disclosure may be implemented and practiced with different lasers, it will be appreciated that the concept of sufficient proximity is a function of the distance that the laser used and its photons can travel in a liquid environment.

Bubble dynamics typically have two stages, expansion followed by collapse. Furthermore, this dynamics has its own time constant. During the expansion of the bubble, where the bubble expands, further delivery of laser pulse power (power = energy rate) does not appear to be effective on the bubble itself, as nothing inside the bubble can push (i.e., there is no or little absorption medium inside the bubble).

By analogy with the harmonics of the operation of a fairground swing, in order to effectively increase the swing's amplitude, the "push" frequency should be matched with the natural frequency of the swing. In other words, if the pulse "resonates" with the natural frequency of the bubble (f 1/200 < us > -5000 < Hz >), the pulse will be most effective in increasing the bubble size. Thus, the various embodiments described herein may modulate the laser pulses based on the natural frequency of the bubbles.

In various embodiments, the laser pulses may be modulated based on the natural frequency of the bubbles as follows. A quasi-continuous wave (QCW) laser, such as TFL, may be used that is adapted to be powered up and down also during long quasi-continuous pulses. In many embodiments, powering up and powering down during quasi-continuous pulses may be accomplished by generating fluctuating power. Further, the fluctuating power may be generated by driving the pump laser source with a variable current while integrating over time to deliver the required Pulse Energy (PE). In various embodiments, the total volume of modulated power over time is equal to the requested PE defined by the user. According to some embodiments, the power may be at its highest at the beginning of the pulse, e.g., at the maximum power that the system can deliver.

Once an exponential bubble is initiated, the power may preferably be subsequently reduced until the bubble is at its maximum size, thereby providing a "reserve" of laser energy that may be better utilized to impinge on the target once the gaseous pathway is sufficiently close to the target. At the moment the bubble begins to collapse, the power may preferably fluctuate back to its maximum level. This should be repeated cyclically with a period approximately or substantially equal to the bubble lifetime.

Since the target may in some cases be moving (e.g. in the case of kidney stones) or even if the target is more or less stationary relative to the laser fiber tip, the distance between the laser fiber tip and the target may differ depending on the anatomy of the person or the actual access of the laser fiber tip to the target or the destruction of the target during the surgical procedure. Thus, the power fluctuation technique can vary based on the distance between the laser fiber tip and the target point. For example, when the distance to the target is changed (e.g., due to movement of the target and/or optical fiber, due to changes in patient anatomy or target, etc.), such distance changes may be measured, monitored, or estimated so that the power of the laser may be adjusted accordingly in flight. Thus, as the distance increases/decreases, the system can recalculate the pulse length required to create a sufficiently effective pulse and/or expose the target spot to sufficient laser energy to meet the clinical effect. For example, for a remote target, the number of cycles can be increased to provide a clear, stable, liquid free path from the laser fiber tip to the target.

Fig. 6 illustrates an exemplary graph 600 of laser pulse power modulation 604 as a function of bubble size 602 in accordance with one or more embodiments described herein. In various embodiments, diagram 600 includes an exemplary pulse power modulation scheme. The pulse modulation scheme may include one or more settings, modes, parameters, characteristics, features, etc. of the pulse, the environment (e.g., liquid medium, distance), and/or various components used to implement the pulse (see, e.g., laser system 900). The pulse power modulation 604 is illustrated by the sinusoidal pattern shown in the slanted hatched area. In this case, the power is modulated from a high level of 500W to a low level of 300W. According to this aspect of the disclosure, the laser power over the long pulse is modulated in a direction dynamically opposite to the bubble described above, so that the laser is modulated downward as the bubble expands and upward as the bubble collapses. The embodiments are not limited in this context.

Fig. 7 illustrates an exemplary plot 700 of modulated and unmodulated laser pulses in combination with associated bubble dynamics in accordance with one or more embodiments described herein. Diagram 700 shows an exemplary comparison between an unmodulated long laser pulse scheme 704a and its associated bubble dynamics 704b and a modulated long pulse scheme 702a and its associated bubble dynamics 702b according to the present disclosure. The graph 700 includes pulse power on the first y-axis 706, bubble size on the second y-axis 708, and time on the x-axis 710. In various embodiments, fig. 7 may correspond to a bubble path resonance modulation technique. For example, the laser pulse may be adapted to the bubble dynamics to cause the bubble size to resonate, resulting in increased energy delivery to the target site.

The flat, unmodulated, long pulse 704a shown in fig. 7 may cause cascading of bubbles that expand and collapse in a sinusoidal pattern (corresponding to bubble dynamics 704 b). In addition, bubbles from the unmodulated pulses 704a repeatedly grow to about the same size and collapse to about zero size in an uncontrolled manner. In other words, since there is no mechanism to control or synchronize bubble collapse and timing and/or position of laser power pulses, there is only random constructive and destructive interaction. As will be appreciated, the amount of energy put into the process is equal to the area under the pulsed power line 704a (the integral of power over time). However, when the laser power is modulated in a direction opposite to the bubble dynamics (see 702a,702 b), energy is saved during bubble expansion. In addition, during bubble collapse, higher energy modulation reduces the rate of collapse and accelerates the formation of the next bubble. The accelerated creation of the second foam occurs before the previous foam collapses to zero size and disappears. Thus, the second bubble starts from the "shoulder" of the first bubble and reaches a greater distance. Thus, many of the embodiments described herein may utilize a pulse modulation scheme (e.g., 702 a) whereby the same distance reached by the unmodulated pulse 704a is reached while using less laser energy.

Fig. 8 illustrates an exemplary diagram 800 in accordance with one or more embodiments described herein. Graph 800 shows an exemplary pulsing scheme 810 in combination with its associated bubble dynamics 812. Graph 800 includes pulse power on a first y-axis 802, bubble size (with target location line 808 at 2 mm) on a second y-axis 804, and time on an x-axis 806. In various embodiments, fig. 8 may correspond to a bubble path resonance modulation technique. For example, the target distance may be utilized to create bubbles of a corresponding size prior to burst of the delivery pulse.

The pulsing 810 shown in graph 800 operates in a direction opposite to the bubble size dynamics 812. In this example, the target point is located at a distance of 2mm from the fiber tip (see line 808). As shown in the illustrated embodiment, the bubble does not collapse to zero size, or collapse is at least reduced, because the power of the laser is modulated upward as the bubble begins to shrink in size. Each successive bubble builds up on its "shoulder" of the previous bubble, creating a gradual pattern until the gaseous pathway reaches a near target. As used herein, approaching a target point may mean less than or equal to a threshold distance. In many embodiments, the threshold distance may be determined based on one or more of the wavelength of the laser beam, its associated water absorption coefficient, and the maximum available power of the laser beam. For example, the threshold distance may be about 0.1mm when using a thulium laser and about 0.5 when using a holmium laser.

Once the gaseous pathway is established, the laser power is switched (or ramped up) to its maximum power (or power setting associated with the desired treatment) so that a majority of the pulse energy can be delivered to the target site. In various embodiments, the laser energy transfer in the liquid medium may be a function of the laser pulse shape in air, the dynamics of the bubble front over time, and the delay between initiation of the laser pulse and initiation of the bubble.

While the above discussion has generally been directed to treating distant targets, alternative pulsing profiles that improve energy delivery at relatively nearby target distances may be referred to as "chevrons". In various embodiments, nearby targets may be defined as those located at a distance that may be bridged solely by an exponential bubble, while distant targets may be defined as those located at a distance that is 2 to 4 times the size of the exponential bubble, requiring a "bubble string" to deliver sufficient energy to the target. Different lasers may result in different index bubble sizes. For example, an exponential bubble for a holmium laser may be approximately between 1mm and 2mm and an exponential bubble for a thulium laser may be approximately between 0.5mm and 1 mm.

In various embodiments, the V-shaped pulse modulation may have one or more of the following profile features: (a) starting at maximum power to create an initial bubble; (b) decreasing power as the bubble expands; and (c) increasing power back to maximum when the bubble is at its maximum size or when the bubble reaches the target (whichever is shortest). In various embodiments, such V-shaped pulsing will result in more efficient energy delivery than the holmium laser short mode (which resembles a downward sloping triangle) because it delivers more pulse energy during the expansion phase of the bubble, thus encountering less water absorption.

In various embodiments, the laser power and the distance between the fiber tip and the target point may be provided as inputs for optimizing pulse modulation. The exponential bubble maximum size may be a function of the instantaneous pulse power during the first 10s of microseconds, as well as the wavelength absorption in the water, the beam quality, and the delivery fiber geometry. Thus, for a given laser and delivery fiber, bubble dynamics for various peak powers can be measured, such as in a stage setup. A look-up table may be created to tabulate the relationship between { peak power and/or initial power, fiber size and wavelength } and { maximum bubble size, time from initiation of lasing to start of bubble formation (t 0), time to maximum bubble size (tmax) and collapse time }. From this information, an initial modulation frequency of approximately 1/(tc-tmax-t 0) can be obtained. Further insight into modulation frequency adjustment may be gained by experimental observations of the effect of modulation frequency variation on steam tunnel stability and energy delivery distance in a workstation setting without departing from the scope of the present disclosure. The exponential bubble size as a function of time may depend strongly on the pulse (peak) power and the absorption coefficient of the liquid at the laser wavelength. Thus, the pulse (peak) power and the absorption coefficient of the liquid at the laser wavelength can be used to estimate the time for an exponential bubble to reach its maximum size and begin to collapse.

Fig. 9 illustrates an example laser system 900 in accordance with one or more embodiments described herein. In various embodiments, laser system 900 or one or more components thereof may be used to implement one or more of the techniques described herein, such as one or more of the pulse modulation schemes. In many embodiments, the laser system 900 may be or include a fiber laser. In the illustrated embodiment, the laser system 900 includes a laser source 921 capable of generating a laser beam 923, a controller 922, a laser fiber 924 (or fibers 924), a connector 925, a partially transparent mirror 926A, a partially transfer mirror 926B, a photodetector 927, and a distance measurement module 929 that utilizes reflected light 928 to dynamically measure the distance between the tip of the laser fiber 924 and a target point (not shown). In various embodiments, the laser fiber 924 can be introduced into a body cavity using known means (e.g., an endoscope) for positioning the tip of the laser fiber 924 in proximity to a target site, such as a kidney or other urinary tract stone or prostate to be treated by ablation or enucleation. One or more components of fig. 9, or aspects thereof, may be incorporated into other embodiments of the present disclosure, or excluded from the described embodiments, without departing from the scope of the present disclosure. For example, the distance measurement module 929 and/or the photodetector 927 may be excluded from the laser system 900 without departing from the scope of this disclosure. The embodiments are not limited in this context.

The laser source 921 of the system 900 can generate a laser beam 923 that is transmitted through the connector 925 to the laser fiber 924 and thence to the target site. The system also includes a controller 922. Fig. 9 schematically illustrates an embodiment of the present invention. The laser system 900 is composed of a laser module 921 and a control unit 922. The laser beam 923 exiting the laser source 921 is configured to reach the optical fiber 924 through a connector 925. Partially transparent mirror 926A is located along the optical path of beam 923 and is configured to reflect at least a portion of beam 923 into photodetector module 927. Some of the backscattered light from the target spot enters the optical fiber 924, passes through the connector 925, and is configured to target the partially-transferred mirror 926B and enter the distance measurement module 929. The module 929 is configured to measure the distance between the tip of the optical fiber 924 and the target point. The modules 927 and 929 are also controlled by the programmable controller 922. In some embodiments, during operation, the programmable controller unit 922 may receive a first electrical signal from the module 927 indicative of the energy level of the laser pulse and/or a second electrical signal from the distance measurement module 929 indicative of the change in distance between the tip of the optical fiber 924 and the target point. In various embodiments, based on at least one of the first and second indication signals, the laser system 900 can be configured to adjust one or more operating parameters, such as the amount of current supplied to the laser pumping element, to maintain the energy level within the target point parameters and according to any dynamic change in laser performance or distance to the target point. Some aspects of the system 900 are described in more detail in U.S. patent No.10,231,781, (' 781 patent), the entire disclosure of which is incorporated herein by reference.

It will be appreciated that one or more embodiments described herein may be implemented without one or more of the photodetectors 927 and the distance measurement module 929. In some embodiments, the distance between the fiber tip and the target point may be a desired or predetermined distance. For example, the predetermined distance may be based on a mode of the laser system. In another example, the predetermined distance may be based on user input. Further, in some embodiments, the modulation scheme may be selected based on an operating mode and/or user input.

In various embodiments, the controller 922 may include a processor and a memory including instructions that, when executed by the processor, cause the processor to perform one or more techniques or aspects described herein. In many embodiments, the controller 922 may initiate and regulate the power emitted from the laser source 21. In some embodiments, the controller 922 may measure the distance from the tip of the laser fiber to the target point. In other embodiments, the distance may be provided as an input to the controller 922. For example, the distance measurement module 929 may provide the distance as an input to the controller 922. Techniques for determining the distance between the tip of a laser fiber and a target spot are described in more detail in U.S. Pat. No.9,017,316 and U.S. provisional patent application No.63/118,857, the entire disclosures of which are incorporated herein by reference. Depending on the measured distance, the controller 922 may initiate and adjust the amount of power it provides to the laser fiber, and in the context of the present disclosure, initiate and adjust the varying power configuration (modulation scheme) described herein.

In many embodiments, the laser system 900 can operate in different modes for near targets and far targets. As previously described, for example, V-shaped optimization can be used to determine a pulsing scheme for a nearby target and resonant modulation optimization can be used to determine a pulsing scheme for a distant target. In various embodiments, the controller 922 may determine which optimization and/or modulation scheme to use based at least in part on the distance to the target point.

For V-shape optimization on nearby targets, the inputs may include pulse energy and targets at very close ("contact"/"close"). As described above, the term "very close" may mean that the target point is within a distance from the tip of the laser fiber 924 that may be individually bridged by an exponential bubble. In such a scenario, the initial pulse power may be determined to deliver bubbles of approximately (or substantially) 1 to 2 times the size of the distance to the target point. Maximum energy delivery may occur when the bubble is equal to and greater than the distance to the target point. Thus, in some embodiments, the bubble size may be used to control the amount of time that maximum energy is delivered to the target point. For example, a bubble size that is approximately twice the distance to the target point may be used to deliver maximum energy over a relatively long period of time, and a bubble size that is approximately equal to the distance to the target point may be used to deliver maximum energy over a relatively short period of time. In some embodiments, the controller 922 may determine an initial pulse power. The laser may be emitted at an initial pulse power and then modulated downward until the bubble approaches a maximum size. The pulse power may then be increased to a maximum. In some embodiments, the system may start at maximum power when the initial pulse power is equal to maximum power, decrease power during bubble expansion, and increase again to maximum power when the bubble is at maximum size. Finally, the pulse may be terminated when the integral (power x time) is equal to the requested pulse energy. As used herein, "maximum power" may not mean the maximum power that the laser source can deliver, but may mean the power level for a desired therapy or treatment.

For resonant modulation optimization at a remote target, the input may include pulse energy and the target at the remote target (the "remote" mode). The initial pulse power may be set at the maximum system power. For example, the controller 922 may set the initial pulse power to a maximum level based on classifying the target as far based on the distance estimate. The laser may be emitted at a maximum power level and then modulated downward during bubble expansion. When the bubble reaches maximum size, the power can again be modulated to maximum. The modulation may then be cycled through a period in the range of 0.5 to 1.5 times the bubble expansion/collapse dynamics (e.g., 0.7-1.3 times the time from start to collapse) to achieve a resonant effect. In various embodiments, the period may be adjusted for each continuous bubble in the bubble string, such as due to a change in distance to the target point. When a train of bubbles is desired to bridge the distance to the target, the pulse power can be increased to a maximum to take advantage of the minimum liquid along the laser path between the fiber tip and the target. Finally, the pulse may be terminated when the integral (power x time) is equal to the requested pulse energy.

In one embodiment, a method of operating laser system 900 may include one or more of the following exemplary operational steps of laser system 900 configured to implement one or more pulse modulation schemes described herein. Step one, the user selects the type of fiber in use. According to one embodiment, a user may manually select one type of optical fiber to be used in a treatment. According to another embodiment, an automatic fiber identification system may be implemented. Step two, the user may select a desired therapeutic energy level. The pulse energy defined by the user for treatment may be the total energy desired to be emitted by the laser system in modulated pulses. In other words, and as will be discussed below, the system may be programmed and configured with a suitable programmable controller to set the pulsing scheme in a manner transparent to the user. For example, the user in the present embodiment may not need to set the values of various parameters.

Step three, the user may select a modulation scheme repetition rate (e.g., the time between modulation pulses). Step four, the user can select a desired (average) working distance between the fiber tip and the target tissue. According to another embodiment, the working distance may be automatically detected by the system, for example by using a distance assessment technique as described in U.S. patent application Ser. No.13/811,926, the entire contents of which are incorporated herein by reference. Step five, based on the previously manually loaded or automatically detected parameters, the system may automatically define or calculate operating values for one or more of peak power, initial power, fiber size, wavelength, maximum bubble size, time from initiation of lasing to start of bubble formation (t 0), time to maximum bubble size (tmax), and collapse time (tc) from a look-up table operably associated with the programmable controller.

Step six, pulses may be transmitted according to a modulation scheme. In various embodiments, the system may be configured to measure the actual value of each pulse/modulation scheme. In step seven and step eight, the system may be configured to compare the measured value with the predefined value on step five. If the measured parameters deviate from the predefined parameters, the system automatically corrects the deviation in step nine and sends a new set of operating parameters to the programmable controller, which is implemented in the next modulation scheme by repeating at step six. In this way, the system may keep the actual working value within a predefined range. It should be appreciated that during step seven, the system may be configured to measure different parameters that may be related to the actual laser pulse energy.

For example, according to one embodiment, the system may use the photodetector 927 to measure the optical energy output of the modulation scheme. According to another embodiment, for example, the system may be configured to measure current or voltage pulses sent to the laser pumping energy source. Thus, the feedback loop may be configured to feedback based on each measured parameter, whether this is a measured optical value, a measured current value, a measured voltage value, or any other measured parameter related to the pulse modulation scheme.

In some embodiments, the method of operating the laser system 900 may be loosely based on fig. 3A and 3B of the' 781 patent, of course, taking into account any differences in the laser sources and the laser firing sequences described herein, as illustrated in the flow chart of fig. 10.

Fig. 10 illustrates an exemplary process flow 1000 (or method 1000) in accordance with one or more embodiments described herein. In process flow 1000, a subset of the operational steps may include measuring a distance from a laser fiber tip to a target point at block 1002. For example, the controller unit 922 may determine the distance between the tip of the laser fiber 924 and the target point. More specifically, the controller unit 922 and/or circuitry of the distance measurement module 929 may execute instructions and/or receive signals to determine the distance between the tip of the laser fiber 924 and the target point. At decision block 1004, if the measured distance is less than or equal to distance (D) X, then method 1000 may proceed to V-mode; if, however, the distance D is greater than or equal to the distance X, the method may proceed to a modulation mode of operation. In various embodiments, the distance X may be determined experimentally and the results recorded in a look-up table that includes the distance along with other parameters such as the number of pulses and the power applied to the pulses. It should also be mentioned that since the target spot may be moving in its environment, such as kidney stones, the controller may be dynamic in nature and capable of adjusting parameters for the laser, including changing from a V-shaped mode to a resonant modulation mode and vice versa, based on repeatedly determining the distance D and repeatedly determining whether the distance D is greater or less than X.

After the mode is selected (e.g., at block 1006 or block 1020), method 1000 includes selecting parameters for the selected mode. For example, the controller 924 can select the number of pulses and the energy level to be applied to the target (blocks 1008, 1022). More specifically, in the event that a V mode is selected at block 1006, the controller 924 may select an energy level of the pulse; and in the event that a resonant mode is selected at block 1020, the controller 924 may select an energy level of the pulse and a modulation frequency for the pulse.

Continuing to blocks 1010 and 1024, method 1000 may include sending a control signal to a laser source 921 to cause the laser source to activate to emit a laser beam (blocks 1010, 1024), whereupon method 1000 includes operations for controller 924 to calculate pulse energy delivered to the target spot (blocks 1012, 1026). For example, the controller 924 can determine (or receive signals from a sensor that includes indications below) the pulse energy delivered to the target site. Further, at block 1012 or 1026, the controller 924 may estimate a number of effective pulses to be experienced by the target, an effective energy per single effective pulse to be delivered to the target, and a cumulative effective energy to be delivered to the target by the number of effective pulses. Further, for a selected energy level as may be selected by a user, the controller 924 may select the power modulation and bubble path modulation resonant frequencies such that the selected energy is actually delivered to the target in one of the more efficient pulses.

If the selection of the controller is sufficient (blocks 1014, 1028) to achieve the desired effect (stoning, dusting, etc.), the operator observing the degree of treatment may stop the system (blocks 1016, 1032), or vice versa, if the effect is not achieved (blocks 1018, 1030). Thus, the method 1000 may include receiving an indication from an operator (e.g., a physician or the like) whether the treatment is adequate. Based on the received indication, the method 1000 may either end (blocks 1016, 1032) or may repeat (blocks 1018, 1030) or, stated differently, return to block 1002. In this manner, an operator may provide an indication to a system (e.g., system 900) and system 900 may receive the indication and further or additional treatment carrier to achieve a desired effect. The steps may be dynamically adjusted using a closed feedback circuit connected to the controller. Thus, for example, if the distance to the target point changes during the procedure, a closed feedback loop may provide this information to the controller, which may then cause the controller to change the parameters of the treatment.

Fig. 11 illustrates a flow chart showing a method 1100 of implementing a modulation scheme according to some embodiments of the present disclosure. The method 1100 is described with reference to the system 900 and various configurations and embodiments described above. However, it is to be understood that method 1100 may be implemented using a system other than that described herein. The embodiments are not limited in this context.

At block 1102, the method 1100 includes determining pulse energy for a fiber laser. For example, the controller 922 may determine pulse energy for the laser source 921. In some embodiments, the controller 922 may determine the pulse energy based on input received via a user interface. In other embodiments, the controller 922 may determine the pulse energy based on one or more settings of the laser system 900. At block 1104, the method 1100 includes identifying a distance between a tip of the fiber laser and the target point, wherein the liquid is located between the tip of the fiber laser and the target point. For example, the controller 922 may determine a distance between the tip of the laser fiber 924 and the treatment target based on input from the distance measurement module 924. At block 1106, the method 1100 includes determining a modulation scheme based on the distance. For example, the controller 922 may select between a V-shaped modulation scheme and a resonant modulation scheme based on the distance between the tip of the laser fiber 924 and the target point.

At block 1108, the method 1100 includes setting an initial pulse power for a modulation scheme to generate an exponential bubble in the liquid based on the distance. For example, when the distance exceeds a threshold distance, the initial pulse power may be set to the maximum system power. In another example, when the distance is below the threshold distance, the initial pulse power may be set to deliver a bubble of 1 to 2 times the distance to the target point. In some such examples, a look-up table may be used to determine an initial pulse power to deliver a bubble to a target that is 1 to 2 times the distance to the target. At block 1110, the method 1100 includes initiating a pulse via a fiber laser according to a modulation scheme, wherein the modulation scheme reduces the power of the pulse after initiating the pulse at an initial pulse power. For example, controller 922 may initiate pulses via laser source 921 and laser fiber 924 according to modulation scheme 702a, or modulation scheme 810.

FIG. 12 is a block diagram of an exemplary computer system for implementing embodiments consistent with the present disclosure. In some embodiments, FIG. 12 illustrates a block diagram of an exemplary computer system 1200 for implementing embodiments consistent with the present disclosure. In some embodiments, computer system 1200, or one or more portions thereof, may include a controller 922. In some such embodiments, computer system 1200 can be used to control the operation of laser system 900 relative to a target site. The embodiments are not limited in this context.

Computer system 1200 may include a central processing unit ("CPU" or "processor") 1202. Processor 1202 may include at least one data processor for executing program elements for performing user or system generated business processes. The user may include a person, use a person such as the devices included in the present disclosure, or such devices themselves. The processor 1202 may include special purpose processing units such as an integrated system (bus) controller, memory management control unit, floating point unit, graphics processing unit, digital signal processing unit, and the like. The processor 1202 may be configured to communicate with input devices 1211 and output devices 1212 via the I/O interface 1201. The I/O interface 1201 may employ communication protocols/methods such as, but not limited to, audio, analog, digital, stereo, IEEE-1394, serial bus, universal serial bus (Universal Serial Bus, USB), infrared, PS/2, BNC, coaxial, component, composite, digital visual interface (Digital Visual Interface, DVI), high definition multimedia interface (High-definition multimedia interface, HDMI), radio Frequency (RF) antenna, S-Video, video graphics array (Video Graphics Array, VGA), IEEE802.n/b/g/n/x, bluetooth, cellular (e.g., code division multiple Access (Division Multiple Access, CDMA), high speed packet access (High-Speed Packet Access, HSPA+), global System for Mobile communications (Global System For Mobile Communications, GSM), long Term Evolution (LTE), wiMax, or the like.

Using the I/O interface 1201, the computer system 1200 may communicate with input devices 1211 and output devices 1212. In some embodiments, the processor 1202 may be arranged to communicate with the communication network 1209 via the network interface 1203. In various embodiments, a communication network 1209 may be used to communicate with a remote device 1220, such as for accessing a lookup table or utilizing external resources. The network interface 1203 may communicate with a communication network 1209. The network interface 1203 may employ connection protocols including, but not limited to, direct connection, ethernet (e.g., twisted pair 10/100/1000Base T), transmission control protocol/Internet protocol (Transmission Control Protocol/Internet Protocol, TCP/IP), token ring, IEEE802.11a/b/g/n/x, and the like. In some embodiments, one or more portions of computer system 1200 may be integrated into laser system 900. In some such embodiments, one or more components of the laser system 900 may include an input device 1211 and/or an output device 1212 (e.g., a distance measurement module 929, a laser source 921, a photodetector 927, etc.).

The communication network 1209 may be implemented as one of different types of networks, such as an intranet or local area network (Local Area Network, LAN), a closed area network (Closed Area Network, CAN), or the like. The communication network 1209 may be a private network or a shared network that represents an association of different types of networks that communicate with each other using multiple protocols, such as, for example, hypertext transfer protocol (Hypertext Transfer Protocol, HTTP), CAN protocol, transmission control protocol/internet protocol (TCP/IP), wireless Application Protocol (WAP), etc. In addition, the communication network 1209 may include various network devices including routers, bridges, servers, computing devices, storage devices, and the like. In some embodiments, the processor 1202 may be configured to communicate with a memory 1205 (e.g., RAM, ROM, etc., not shown in fig. 12) via a storage interface 1204. The storage interface 1204 may be connected to the memory 1205 using a connection protocol such as serial advanced technology attachment (Serial Advanced Technology Attachment, SATA), integrated drive electronics (Integrated Drive Electronics, IDE), IEEE-1394, universal Serial Bus (USB), fibre channel, small computer system interface (Small Computer Systems Interface, SCSI), etc., the memory 1205 including, but not limited to, a memory drive, removable disk drive, etc. The memory drives may further include drums, magnetic disk drives, magneto-optical disk drives, redundant arrays of independent disks (Redundant Array of Independent Discs, RAID), solid state memory devices, solid state drives, and the like.

The memory 1205 may store a set of programs or database components including, but not limited to, a user interface 1206, an operating system 1207, a web browser 1208, and instructions 1215, among others. In various embodiments, the instructions 1215 may include instructions that, when executed by the processor 1202, cause the processor 1202 to perform one or more of the techniques, steps, processes, and/or methods described herein to estimate a distance or perform a calibration. For example, instructions to perform method 380 may be stored in memory 1205. In many embodiments, the memory 1205 includes at least one non-transitory computer readable medium. In some embodiments, computer system 1200 may store user/application data, such as data, variables, records, and the like, as described in this disclosure. Such a database may be implemented as a fault tolerant, relational, scalable, secure database such as Oracle or Sybase.

The operating system 1207 may facilitate the resource management and operation of the computer system 1200. Examples of operating systems include, but are not limited toOS/>UNIX-like System release (e.g., BERKELEY SOFTWARE +.>(BSD)、/> OPENBSD, et al), -a method of treating cancer>Release (e.g. RED-> Etc.), or (I) on the neck>(/7/8, 10, etc.), -a. >GOOGLE ^TM ANDROID ^TM 、/>OS or the like. The user interface 1206 may facilitate display, execution, interaction, manipulation, or operation of program components through text or graphics facilities. For example, the user interface may provide computer interactive interface elements, such as cursors, icons, check boxes, menus, scroll bars, windows, widgets, and the like, on a display system operatively connected to computer system 1200. A graphical user interface (Graphical User Interface, GUI) may be employed, including but not limited to +.>Operating system (e.g., aero, metro, etc.), web interface libraries (e.g. AJAX、HTML、/>Etc.), etc.

In some embodiments, computer system 1200 may implement the program components stored by web browser 1208. The Web browser 1208 may be a hypertext browsing application, such asINTERNET/>GOOGLE ^TM CHROME ^TM 、/>Etc. Secure web browsing may be provided using secure hypertext transfer protocol (HTTPS), secure sockets layer (Secure Sockets Layer, SSL), transport layer security (Transport Layer Security, TLS), and the like. The Web browser 1208 may utilize, for example, AJAX, DHTML,Application programming interfaces (Application Programming Interface, API), and the like. In some embodiments, computer system 1200 may implement a program component stored by a mail server. The mail server may be an internet mail server such as Microsoft Exchange. Mail server can use e.g. Active Server Pages (ASP),/for example >C++/C#、/>.NET、CGI SCRIPYS、/>PHP、/>And the like. The mail server may utilize, for example, internet message Access protocol (Internet Message Access Protocol, IMAP), messaging application Programming interface (Messaging Application Programming Interface, MAPI), a message service protocol (MAPI),exchange, post office protocol (Post Office Protocol, POP), simple mail transfer protocol (Simple Mail Transfer Protocol, SMTP) and the like. In some embodiments, computer system 1200 may implement a program component stored by a mail client. The mail client may be a mail viewing application, such asMAIL、/> Etc.

Furthermore, one or more computer-readable storage media may be used to implement embodiments consistent with the present disclosure. Computer-readable storage media refers to any type of physical memory on which information or data readable by a processor may be stored. Thus, a computer-readable storage medium may store instructions for execution by one or more processors, including instructions for causing the processors to perform steps or stages consistent with embodiments described herein. The term "computer-readable medium" should be taken to include tangible articles and exclude carrier waves and transient signals, i.e., non-transient. Examples include random access Memory (Random Access Memory, RAM), read-Only Memory (ROM), volatile Memory, non-volatile Memory, hard disk drives, compact Disc (CD) ROMs, digital video discs (Digital Video Disc, DVDs), flash Memory drives, magnetic disks, and any other known physical storage medium.

It will be understood by those within the art that, in general, terms used herein, and generally, are intended as "open" terms (e.g., the term "comprising" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least"). Those skilled in the art will further understand that if a specific number of an introduced claim recitation is intended. For example, as an aid to understanding, the detailed description may contain usage of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim recitation to disclosures containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., "a" and/or "an" should typically be interpreted to mean "at least one" or "one or more"); the definite article is used as it applies to introduce claim recitations. Furthermore, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, typically means at least two recitations, or two or more recitations).

All of the apparatus and/or methods disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. Although the apparatus and methods of this disclosure have been described in terms of preferred embodiments, it will be apparent to those of skill in the art that variations may be applied to the apparatus and/or methods and in the steps or in the sequence of steps of the method described in this disclosure without departing from the concept, spirit and scope of the disclosure. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and concept of the disclosure as defined by the appended claims.

Claims (15)

1. A system, comprising:

a fiber laser; and

a controller comprising a processor and a memory, the memory comprising instructions that when executed by the processor cause the processor to:

determining pulse energy for the fiber laser;

identifying a distance between a tip of the fiber laser and a target point, wherein a liquid is located between the tip of the fiber laser and the target point;

determining a modulation scheme based on the distance;

setting an initial pulse power for the modulation scheme to generate an exponential bubble in the liquid based on the distance; and

A pulse is initiated via the fiber laser according to the modulation scheme, wherein the modulation scheme reduces the power of the pulse after initiating the pulse at the initial pulse power.

2. The system of claim 1, wherein the modulation scheme increases the power of the pulses to a maximum system power level at a time estimated for the exponential bubble to reach a maximum size.

3. The system of claim 2, wherein the instructions, when executed by the processor, further cause the processor to estimate a time for the exponential bubble to reach a maximum size based on the initial pulse power and an absorption coefficient of the liquid at a wavelength of the fiber laser.

4. The system of any of claims 1-3, wherein the instructions, when executed by the processor, further cause the processor to:

identifying an updated distance between the tip of the fiber laser and the target point; and

an updated modulation scheme is determined based on the updated distance.

5. The system of any of claims 1-4, wherein the modulation scheme is configured to modulate a decrease in pulse power during inflation of the exponential bubble and a rise in pulse power during collapse of the exponential bubble.

6. The system of any of claims 1-5, wherein the modulation scheme comprises an initial modulation frequency and instructions that when executed by the processor further cause the processor to determine the initial modulation frequency based on a time at which the exponential bubble collapses, a time at which the exponential bubble reaches a maximum size, and a time from initiation of lasing to start of bubble formation.

7. The system of any of claims 1-6, wherein the instructions, when executed by the processor, further cause the processor to set an initial pulse power for the modulation scheme to generate the exponential bubble in the liquid based on the distance and the pulse energy.

8. The system of any of claims 1-7, wherein the instructions, when executed by the processor, further cause the processor to integrate the power of the pulse with respect to time and terminate the pulse when the integrated power of the pulse with respect to time is equal to the pulse energy.

9. The system of claim 1, wherein the instructions, when executed by the processor, further cause the processor to classify the target point as a distant target point based on the distance and set the initial pulse power to a maximum system power level based on classifying the target point as distant.

10. The system of claim 9, wherein the modulation scheme is configured to obtain a resonance effect by cycling through a period between 0.7 and 1.3 times the time from the start of the exponential bubble to collapse.

11. A method, comprising:

determining pulse energy for a fiber laser;

identifying a distance between a tip of the fiber laser and a target point, wherein a liquid is located between the tip of the fiber laser and the target point;

determining a modulation scheme based on the distance;

setting an initial pulse power for the modulation scheme to generate an exponential bubble in the liquid based on the distance; and

a pulse is initiated via the fiber laser according to the modulation scheme, wherein the modulation scheme reduces the power of the pulse after initiating the pulse at the initial pulse power.

12. The method of claim 11, comprising modulating a pulse power drop during inflation of the exponential bubble and modulating a pulse power rise during collapse of the exponential bubble.

13. The method of any of claims 11 to 12, comprising classifying the target as a distant target based on the distance, and setting the initial pulse power to a maximum system power level based on classifying the target as distant.

14. The method of claim 13, comprising cycling through a period between 0.7 and 1.3 times the time from the start of the exponential bubble to collapse.

15. The method of any of claims 11 to 14, wherein the modulation scheme increases the power of the pulses to a maximum system power level at a time estimated for the exponential bubble to reach a maximum size.