Apparatus and method for enhancing laser beam efficacy in liquid medium

Abstract

To provide an apparatus for enhancing laser beam efficacy in a liquid medium.SOLUTION: The present disclosure generally relates to the field of laser based medical devices. Particularly, but not exclusively, the present disclosure relates to an apparatus and method for enhancing laser beam efficacy in a liquid medium. In many embodiments, laser pulses are modulated based on bubble dynamics to improve energy delivery to a target. A variety of exemplary pulse modulation schemes are described including modulating pulse power to be lowered during expansion of an index bubble and modulating pulse power to be increased during collapse of the index bubble.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] 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 laser beam efficacy in liquid media. [Background technology]

[0002] Lasers are widely used to perform various medical procedures, such as tissue coagulation, ablation, cutting, fragmentation, pulverization, and extraction. Laser procedures are performed through and within a variety of media and environments, including gases, solids, and liquids. During a laser procedure, the interaction between the laser radiation and the target object (e.g., biological tissue such as the prostate, kidney, or urinary stones) depends on the laser used and, among other factors, the absorption, reflection, and scattering of the environment and the target object. Ureteral stones, kidney stones, or prostate are just three examples of common targets that can be treated with a laser. Typically, the treatment environment can be saline or other similar liquids. The efficiency of a laser procedure can be a function of the interaction between the laser energy and the target. The portion of the laser energy that reaches and is absorbed by the target contributes to the desired surgical effect. However, laser energy absorbed by the environmental medium can be considered lost energy, which is no longer available for target treatment. Often, laser parameters, such as wavelength, are selected based on the desired clinical effect and the characteristics of the target. For example, infrared (IR) lasers such as holmium or thulium can be used for laser lithotripsy to treat ureteral stones, renal colic, and for prostate ablation or removal. Summary of the Invention

[0003] 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 necessarily intended to identify key features or essential features of the claimed subject matter, nor is it intended as an aid in determining the scope of the claimed subject matter.

[0004] In one aspect, the present disclosure relates 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 do one or more of: determine a pulse energy of the fiber laser; identify a distance between a tip of the fiber laser and a target, where the distance is between the tip of the fiber laser and the target, where a liquid is located between the tip of the fiber laser and the target; determine a modulation scheme based on the distance; set an initial pulse power of the modulation scheme to generate an index bubble in the liquid based on the distance; and initiate a pulse according to the modulation scheme via the fiber laser, where the modulation scheme reduces the power of the pulse after the pulse starts at the initial pulse power.

[0005] In some embodiments, the modulation scheme increases the power of the pulse to a maximum system power level when the index bubble is estimated to reach a maximum size. In some such embodiments, the instructions, when executed by a processor, further cause the processor to estimate the time it will take for the index bubble to reach a maximum size based on the initial pulse power and the absorptivity of the liquid at the wavelength of the fiber laser.

[0006] In various embodiments, the instructions, when executed by a processor, further cause the processor to identify an updated distance between the tip of the fiber laser and the target, and determine an updated modulation scheme based on the updated distance.

[0007] In some embodiments, the modulation scheme is configured to modulate the pulse power downward during the expansion period of the index bubble and modulate the pulse power upward during the collapse period of the index bubble.

[0008] In many embodiments, the modulation scheme comprises an initial modulation frequency, and the instructions, when executed by a processor, further cause the processor to determine the initial modulation frequency based on a time to collapse of the index bubble, a time to reach a maximum size of the index bubble, and a time from the start of laser emission to the start of bubble formation.

[0009] In some embodiments, the instructions, when executed by a processor, further cause the processor to set an initial pulse power of a modulation scheme to generate an index bubble in the liquid based on the distance and the pulse energy.

[0010] In various embodiments, the instructions, when executed by a processor, further cause the processor to integrate the power of the pulse with respect to time and terminate the pulse when the integral of the power of the pulse with respect to time equals the pulse energy.

[0011] In some embodiments, the instructions, when executed by a processor, further cause the processor to classify the target as a distant target based on distance, and set the initial pulse power to a maximum system power level based on the classification of the target as distant. In some such embodiments, the modulation scheme is configured to obtain a resonance effect by cycling with a period between 0.7 and 1.3 times the time from the inception to the collapse of the index bubble.

[0012] In another aspect, the disclosure relates to at least one non-transitory computer-readable medium comprising a set of instructions that, in response to being executed by a processor circuit, cause the processor circuit to do one or more of: determine a pulse energy of a fiber laser; identify a distance between a tip of the fiber laser and a target, wherein a liquid is located between the tip of the fiber laser and the target; determine a modulation scheme based on the distance; set an initial pulse power of the modulation scheme to generate an index bubble in the liquid based on the distance; and initiate a pulse according to the modulation scheme via the fiber laser, wherein the modulation scheme reduces the power of the pulse after initiating the pulse at the initial pulse power.

[0013] In some embodiments, the modulation scheme increases the power of the pulse to a maximum system power level at which the index bubble is estimated 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 the time it will take for the index bubble to reach a maximum size based on the initial pulse power and the absorptivity of the liquid at the wavelength of the fiber laser.

[0014] In various embodiments, the set of instructions, in response to execution by the processor circuit, further cause the processor circuit to identify an updated distance between the tip of the fiber laser and the target, and determine an updated modulation scheme based on the updated distance.

[0015] In some embodiments, the set of instructions, in response to execution by the processor circuit, further cause the processor circuit to set an initial pulse power of a modulation scheme to generate an index bubble in the liquid based on the distance and the pulse energy.

[0016] 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 integral of the power of the pulse with respect to time equals the pulse energy.

[0017] In yet another aspect, the present disclosure may include a method comprising one or more of: determining pulse energy of a fiber laser; identifying a distance between a tip of the fiber laser and a target, wherein a liquid is located between the tip of the fiber laser and the target; determining a modulation scheme based on the distance; setting an initial pulse power of the modulation scheme to generate an index bubble in the liquid based on the distance; and initiating a pulse according to the modulation scheme via the fiber laser, wherein the modulation scheme reduces the power of the pulse after initiating the pulse at the initial pulse power.

[0018] In some embodiments, the method includes modulating the pulse power downward during an expansion period of the index bubble and modulating the pulse power upward during a collapse period of the index bubble.

[0019] In various such embodiments, the method includes classifying the target as a distant target based on 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 includes cycling with a period between 0.7 and 1.3 times the time from inception to collapse of the index bubble.

[0020] Non-limiting embodiments of the present disclosure are described, by way of example, with reference to the accompanying drawings, which are schematic and not intended to be drawn to scale. In the drawings, each identical or nearly identical component illustrated is typically represented by a single numeral. It will be appreciated that the various figures included in this 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 be hidden. For purposes of clarity, not every component is labeled in every drawing, and not every component of each embodiment is shown unless illustration is necessary to enable those skilled in the art to understand the disclosure. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is an exemplary diagram of holmium and thulium laser pulses according to one or more embodiments described herein. [Figure 2A] 1A-1C illustrate various aspects of short holmium laser pulses in different media, according to one or more embodiments described herein. [Figure 2B] 1A-1C illustrate various aspects of short holmium laser pulses in different media, according to one or more embodiments described herein. [Figure 3A] 1A-1C illustrate various aspects of thulium laser long pulses in different media, according to one or more embodiments described herein. [Figure 3B] 1A-1C illustrate various aspects of thulium laser long pulses in different media, according to one or more embodiments described herein. [Figure 4A] 1 is an exemplary diagram of a thulium laser long pulse in air medium, according to one or more embodiments described herein. [Figure 4B]1 is an exemplary diagram of a thulium laser long pulse in a liquid medium, according to one or more embodiments described herein. [Figure 5] 10 is an exemplary time series of images of bubble dynamics, according to one or more embodiments described herein. [Figure 6] 10 is an exemplary diagram of modulated laser power in relation to bubble size, according to one or more embodiments described herein. [Figure 7] 1 is an exemplary illustration of modulated and unmodulated laser pulses and associated bubble dynamics according to one or more embodiments described herein. [Figure 8] 1 is an exemplary illustration of a modulated laser pulse and associated bubble dynamics according to one or more embodiments described herein. [Figure 9] FIG. 1 illustrates an exemplary laser system according to one or more embodiments described herein. [Figure 10] FIG. 1 illustrates an example process flow according to one or more embodiments described herein. [Figure 11] 1 is a block diagram of a method for implementing an embodiment consistent with the present disclosure. [Figure 12] FIG. 1 is a block diagram of an exemplary computer system for implementing embodiments consistent with the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0022] The present disclosure provides medical devices and techniques for enhancing laser beam effectiveness in a liquid medium, e.g., for a desired surgical effect on a target. The liquid environment of many treatment environments tends to absorb a significant portion of the laser energy. For example, the liquid medium can absorb and attenuate the laser energy, reducing the energy available for the desired surgical effect on the target. Energy absorbed by the liquid medium can also heat the surrounding tissue, creating undesirable safety issues and the need to irrigate the area with a cooling fluid.

[0023] One laser treatment technique, referred to herein as the bubble path effect, utilizes one or more bubbles to act as a gaseous pathway for laser energy to pass from the laser fiber tip to the target. The resulting gaseous pathway has a lower absorption rate than a liquid pathway. The bubble path effect is described in more detail in U.S. patent applications Ser. Nos. 15 / 927,143, 16 / 177,800, and 15 / 861,905, which are incorporated herein by reference. However, as will be explained in more detail below, bubble dynamics introduce many challenges in establishing and maintaining a gaseous pathway between the laser fiber tip and the target to improve laser beam effectiveness.

[0024] Thus, one aspect of the present disclosure is to optimize the available laser energy for treating a target based on an enhanced bubble-path effect on the target, which will be discussed in more detail below. The amount of energy required to create the bubble-path effect, i.e., to 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 tip of the fiber and the target. Therefore, another aspect of the present disclosure is to reduce the amount of laser energy that may be wasted creating the bubble-path effect for a particular distance to a tissue target, thus increasing the amount of laser energy available for treating the target. Yet another aspect of the present disclosure is to increase the distance of the bubble-path effect, reaching targets farther away from the laser fiber tip for a particular laser energy. Utilizing the present disclosure can result in less energy being wasted when treating tissue at a given distance, or can enable tissue to be treated at a greater distance from the laser fiber tip for a given level of energy.

[0025] In some bubble-pass techniques, a first laser pulse may be delivered to create a first bubble, through which a second laser pulse is delivered after a predefined time delay. Due to the first bubble (and the relative absence of fluid), the second laser pulse is transmitted with reduced absorption and reaches the tissue with higher energy than the energy of a single laser pulse traveling solely through the liquid medium. Furthermore, the energy of the first and second pulses, as well as the time delay between these two pulses, can be varied to achieve higher energy delivery to tissues located at various distances from the tip of the laser fiber.

[0026] Infrared lasers, such as holmium (Ho) lasers with a wavelength of 2100 nm and thulium (Tm) lasers with wavelengths in the 1940-1970 nm range, are strongly absorbed in liquid environments. For example, photons at 1940 nm have an absorption coefficient of 110 1 / cm, while photons at 2100 nm have an absorption coefficient of 25 1 / cm. Typically, in liquid environments, most of the photons generated by holmium lasers are absorbed before the laser pulse travels 0.5 mm after exiting the optical fiber, while photons generated by thulium lasers are absorbed before the laser pulse travels 0.1 mm after exiting the optical fiber. In comparison, solid-state holmium lasers are characterized by high peak power and relatively short pulses, while thulium fiber lasers (TFLs) are characterized by lower peak power. Therefore, TFLs require a longer time to generate an equivalent amount of energy compared to solid-state holmium lasers. For example, a TFL will generate 0.5 joules of energy in a pulse duration of approximately 1 millisecond (ms), while a solid-state holmium laser requires approximately 0.2 ms to generate the same amount of energy. As discussed further below, the lifetime of a single bubble has been observed to last approximately 0.2–0.3 ms. Furthermore, once initiated, the bubble has been observed to have its own dynamic characteristics, which, in many aspects, are independent of the laser pulse (except for the initial characteristics of the pulse in the very short time frame of tens of microseconds). Based on the above, a short solid-state holmium laser pulse may end before the bubble reaches its maximum size, while a longer TFL pulse will last for three to four bubble lifetimes. The above-mentioned references explain how to optimize the timing and energy distribution between the first and subsequent laser pulses to minimize the energy invested in bubble generation and maximize the amount of energy reaching the target. Furthermore, holmium lasers with reduced peak power can be used to extend the typically short pulse duration.

[0027] However, spreading the holmium laser pulse energy over a longer pulse duration, such as the period in the thulium pulse described above, results in pulse durations longer than the lifetime of a single bubble. As in the case of thulium, laser pulses longer than the lifetime of a single bubble result in the generation of a cascade of multiple bubbles. A cascade of multiple bubbles can create a gas path to the target. However, such a bubble cascade is characterized by a sequence of independent bubbles that expand and collapse at different times and locations along the path. As a result, the effective length of the gas path changes over time. Gas breaks along the path at different times and locations fill with energy-absorbing liquid, which again increases the attenuation of the laser-generated pulse. Therefore, the energy delivered to the target is frequently interrupted in an unpredictable manner during these bubble collapse periods, resulting in multiple subpulses and significant energy waste during the pulse duration.

[0028] Thus, one or more embodiments described herein provide for effective and efficient management of the level of laser energy along a long laser pulse. In various embodiments, effective and efficient management of laser energy during a long laser pulse can provide one or more of the following benefits: (i) increased laser energy delivered to a target at a given distance, (ii) reduced laser energy loss while the gaseous pathway to the target is established, and (iii) stabilization of the pathway during the pulse, as opposed to being subject to stochastic collapse, which has unpredictable energy delivery results. Many embodiments optimize the energy distribution along a long laser pulse.

[0029] Some embodiments described herein provide for reducing or preventing heat buildup in surrounding tissue by more effectively delivering laser energy to a target at a lower energy level to achieve the same level of treatment. For example, laser energy can be delivered to a target at 30 W instead of 40 W while achieving the same level of treatment. Many embodiments can generate pulses that optimize the delivery of energy through an aqueous environment. In many such embodiments, the optimized pulse, when formed, can be used to obtain one of the following benefits: (1) using the same pulse energy to deliver more energy to a target at a given distance, resulting in a faster / stronger intended effect on the tissue, such as fragmentation, shattering, popcorning, etc. (improved efficiency / effectiveness); (2) using the same pulse energy to deliver energy to a target at a longer distance (better action at distance / action at longer distance); and (3) using a lower pulse energy to obtain the same intended effect as with a higher pulse energy, thus reducing unintended side effects and adverse consequences, such as overheating of surrounding tissue (improved safety profile).

[0030] In some embodiments, lasers with low peak power and long pulses, such as TFLs, may be utilized, resulting in a much longer total size and stability of the bubble cascade (along the fiber axis from the laser fiber tip to the target) than the single bubble of a typical short-pulse laser. Therefore, and unexpectedly, even though Tm photons have much stronger absorption in water than Ho, the long Tm pulse travels farther than the short Ho pulse compared to the long Tm pulse, traveling through a longer train of bubbles generated by the TFL. Furthermore, since the pulse lasts for the bubbles to reach the target, a longer pulse duration better utilizes the bubble cascade. However, TFL pulses have been observed to break down into several subpulses due to multiple bubble collapses, resulting in a widely variable energy delivery during the pulse duration, while Ho laser energy can produce a similar energy delivery.

[0031] As mentioned above, bubbles have their own dynamics, and once initiated, in many embodiments, they are no longer related to the characteristics of the laser pulse. The initial bubble formed by the first laser pulse grows to a maximum size (dependent on the initial peak power of the pulse) and then collapses. Typical bubble durations for holmium lasers are approximately 200-300 μs. Laser pulses longer than the bubble lifetime will produce several bubbles in succession that exit the laser fiber tip and travel toward the target.

[0032] FIG. 1 illustrates an exemplary diagram 100 of holmium and thulium laser pulses according to one or more embodiments described herein. In the illustrated embodiment, the holmium and thulium lasers have equal energy of 0.2 Joules. Diagram 100 illustrates a low-peak-power, quasi-continuous, long thulium pulse in contrast to a typical high-peak-power, short holmium laser pulse. Diagram 100 includes bubble size on the positive Y-axis 102 (with potential target locations at line 112), pulse power on the negative Y-axis 104, and time on the X-axis 106. For the high-peak-power holmium laser short pulse, region 118 corresponds to pulse power, curve 108 corresponds to the bubble created, and line 114 corresponds to the effective distance the laser pulse travels through the liquid. For a low peak power quasi-continuous thulium long pulse, region 120 corresponds to the pulse power, curve 110 corresponds to the bubbles created, and line 116 corresponds to the effective distance the laser pulse travels through the liquid.

[0033] In both cases, following the onset of the laser pulse, a bubble is created and begins to expand after a short delay on the order of tens of microseconds (μs). In both cases, the bubble's lifetime, once created, appears to have its own internal dynamics that are not solely related to the laser pulse but also include the internal vapor pressure generated at the bubble extraction site, which may in turn depend on absorption, instantaneous peak power, laser beam quality, and / or the presence and amount of air pockets within the liquid.

[0034] Bubble expansion takes time. In the case of a holmium pulse, the bubble reaches its maximum size well after the highest power peak of the laser, while in the case of a thulium laser, the bubble reaches its maximum size during the laser pulse. FIG. 1 also shows that for an exemplary target distance 112 (positioned at a distance of approximately 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. Some embodiments described herein exploit the independent dynamics of the bubbles to optimize energy distribution using long pulses.

[0035] 2A and 2B illustrate exemplary diagrams 200A and 200B of short holmium laser pulses in different media, according to one or more embodiments described herein. FIG. 2A corresponds to an air medium and includes a diagram 200A of pulse power 202 over time measured in the air medium from a distance of 3 mm. FIG. 2B corresponds to a liquid medium and includes a diagram 200B of pulse power 206 over time measured in the liquid medium from a distance of 3 mm. FIG. 2B also includes a time series of bubble dynamics images 204 corresponding to and shown synchronized with diagram 200B. In each case, a sensor positioned in the air or water path can be utilized to sense and record pulse power over time.

[0036] In the illustrated embodiment, time-series images 204 of bubble dynamics were captured using a high-speed camera. As shown in the time-series image 204 of bubble dynamics, a single index bubble was initiated after a short delay following the onset of the laser pulse. Figure 2B shows that the larger the bubble, the higher the amount of laser power reaching the target, which in this exemplary laboratory setting was the sensor. The maximum energy is experienced by the target while the bubble size (or bubble tunnel size) meets or exceeds the distance to the target, resulting in only air between the fiber tip and the target. Once the bubble begins to collapse, less laser power can reach the target. Figure 2B also shows that the bubble lifetime is longer than the laser pulse duration.

[0037] 3A and 3B illustrate exemplary diagrams 300A and 300B of a thulium laser long pulse in different media, according to one or more embodiments described herein. FIG. 3A corresponds to an air medium and includes a diagram 300A of pulse power over time 302 measured in the air medium from a distance of 2 mm. FIG. 3B corresponds to a liquid medium and includes a diagram 300B of pulse power over time 306 measured in the liquid medium from a distance of 2 mm. FIG. 3B also includes a time series image 304 of bubble dynamics corresponding to and shown synchronized with diagram 300B. In FIGS. 3A and 3B, the pulse power over time 302 and 306 may correspond to an exemplary long pulse of a 0.2 Joule thulium laser. In each case, a sensor positioned in the air or water path is utilized to sense and record the pulse power over time.

[0038] Figures 3A and 3B show the significantly different behavior of a long laser pulse, as opposed to the short laser pulse of Figures 2A and 2B. Surprisingly, as shown in Figure 300B, the target in this case experiences two separate effective laser pulses 308a and 308b, even though only a single long laser pulse was generated. The dynamics of bubble cascades can provide an explanation. Only after the gas path is close enough to the target does some energy reach it (in the case of Tm, most of the energy is absorbed by water within 0.1 mm). Furthermore, it takes time for the gas path to get close enough to the target, and during this time, no laser power reaches the target. Instead, the laser power is primarily absorbed by the liquid on its way to the target. As previously mentioned, the energy absorbed by the liquid is not available to treat the target and can result in unwanted heating of the surrounding tissue.

[0039] Due to the lower peak power, it takes more time for the gas path to expand close enough to the target and for the energy to reach the target, as compared to FIGS. 2A and 2B. Furthermore, in the case of a thulium laser, which is more absorbed by water than holmium, the rise profile (and fall) of the laser experienced by the target is much steeper than in the case of holmium, as can be seen by comparing FIGS. 200B and 300B. Many embodiments described herein can utilize a given pulse energy and target distance to control and optimize power modulation along the pulse, resulting in more laser power being available during the effective pulse experienced by the target and less laser power being lost between effective pulses. In many such embodiments, the user can select the pulse energy.

[0040] Referring now to the bubble dynamics time series image 304 in Figure 3B, several of the images (or frames) in the time series are numbered 1 through 23 from left to right. More specifically, frame 1 shows the tip of the fiber before the start of the laser pulse. Once the laser pulse begins, the index bubble, shown in frame 2, begins to grow into a relatively spherical shape at the tip of the fiber. As this index bubble continues to grow, a second bubble can be seen at its leading edge beginning to grow in the forward direction in frames 3 and 4. Furthermore, because this second bubble is an extension of the index bubble, the high pressure inside the index bubble shapes the second bubble into a more cylindrical shape. Also, as pressure is vented from the index bubble to the second bubble, the index bubble expansion decreases. The result of these two processes is that the majority of the internal pressure in these two bubbles expands primarily forward toward the target, as can be seen in frames 5 through 7.

[0041] At this stage, in this example, the gas path has reached the target close enough that the target experiences laser power. Another aspect of the present disclosure is to generate an index bubble, generate a second bubble at the leading edge of the index bubble, and then modulate the laser pulse power down to a level lower than that required to initiate the index bubble during that time period, causing the index bubble to expand and the second bubble to spontaneously form. Furthermore, the index bubble at the tip of the fiber tends to collapse at its own tip, potentially degrading the fiber. As a result, laser beam quality, as well as treatment efficiency, can be reduced. The higher the laser power during the index bubble initiation period, the higher the internal pressure inside the index bubble, and the stronger the cavitation effect on the tip of the fiber once the index bubble collapses. Therefore, in one embodiment of the present disclosure, the minimum laser power required to initiate the index bubble is used, followed by reduced laser power during the index bubble's expansion period, while the laser power is increased again only after the index bubble begins to collapse, establishing additional bubbles and further gas pathways to the target. Reducing the cavitation effect on the fiber tip can slow its degradation.

[0042] Now, referring to frame 9, we can see that the index bubble begins to collapse, causing a second bubble to break away from the collapsed index bubble. As seen in the next frame 10, fluid fills the gap between the separated bubbles, as well as the collapsing second bubble and the collapsing index bubble. As a result, the target begins to experience reduced laser power until around frame 11, when no more energy reaches the target. Also, at frame 10, and more specifically at frame 11, we can see that another index bubble is initiated and begins to expand at the tip of the fiber. At this stage, the gas path needs to be reestablished, a process similar to that described with respect to frames 1-5, until the path reaches close enough to the target that it again begins to experience exposure to laser power around frame 16.

[0043] Therefore, many embodiments described herein may modulate the laser power down once the index bubble is initiated and during the establishment of the gas path to the target, thereby optimizing the energy distribution along the long pulse to make the bubble-path effect more efficient in light of the independent bubble lifetimes.

[0044] 4A-4B and 5 illustrate various aspects of thulium long laser pulses according to one or more embodiments described herein. More specifically, FIG. 4A illustrates an exemplary diagram 400A of a thulium laser long pulse in an air medium having pulse power 402 over time, FIG. 4B illustrates an exemplary diagram 400B of a thulium laser long pulse in a liquid medium having pulse power 404 over time, and FIG. 5 illustrates an exemplary time series of bubble dynamics images 500 corresponding to diagram 400B.

[0045] Referring to FIG. 4A, the pulse power 402 over time of a long thulium laser pulse in air, approximately 1 ms in duration and producing 0.5 Joules as measured from a distance of 2.5 mm, is shown in FIG. 400A. The corresponding measurement in a liquid medium is shown in FIG. 4B. The pulses in FIGS. 4A and 4B are longer than those shown in FIGS. 3A and 3B. Therefore, the target experiences four effective laser “sub-pulses” 406a, 406b, 406c, and 406d, as shown in FIG. 4B, as opposed to the two effective laser “sub-pulses” 308a and 308b discussed in connection with FIG. 3B. As previously discussed and shown in FIG. 4A, the laser is on quasi-continuously for approximately 1 ms. However, in effect, the target in this example experiences four separate laser sub-pulses 406a, 406b, 406c, and 406d. These four separated effective laser pulses 406a, 406b, 406c, and 406d are the result of the creation and destruction of the gas pathway during the time period the laser is on. Some embodiments described herein may modulate the laser power downward during the time period when the gas pathway is established, thereby allowing spontaneous expansion of the bubble and conserving laser energy until the gas pathway is close enough to the target tissue. Furthermore, when the gas pathway is close enough to the target, embodiments may modulate the laser power upward, utilizing the gas pathway to deliver a higher amount of laser power to the target.

[0046] Providing additional laser energy during the bubble expansion period would be wasted energy because it would "push air" within the bubble, preventing the bubble from growing further in size during the initial pulse energy applied. In other words, there would be no further absorption within the bubble after it begins to expand. To increase the bubble size until the target is reached, laser energy would be consumed only while there is liquid in the path from the laser fiber tip to the target. As a result, the resulting absorption would be converted to pressure, which would re-expand the bubble. Then, if the gas path begins to tear and develop a liquid bridge between the separated gas pockets, the laser power would again be modulated downward until the next opportunity to deliver higher laser power to the target through another effective gas path. Figure 5 shows an image of the bubble cascade dynamics discussed above in connection with Figure 4B.

[0047] Thulium fiber lasers (TFLs) are typically pumped by diode lasers to produce long pulses. Furthermore, TFLs generate long pulse regimes. Accordingly, one or more embodiments described herein may exploit the fact that the time constants associated with bubble formation, initiation, expansion, and collapse are shorter than the laser pulse length to modify pulse power during long laser pulses. In contrast, short-pulse lasers are typically pumped by flash lamps, which themselves operate in a very short pulse regime. Short-pulse lasers operate in a domain where the bubble lifetime is longer than the laser pulse length. However, the embodiments described herein provide various lasers configured to emit light with high absorption in the relevant liquid, which can generate pulses longer than the bubble lifetime and can be modulated up or down. For example, one or more of yttrium aluminum garnet (YAG), erbium, holmium, and other IR diode or solid-state lasers can be modulated up or down in accordance with the present disclosure without departing from its scope.

[0048] Various embodiments described herein may utilize the distance between the tip of the optical fiber and the target to determine the mode of operation. For example, there may be two (or more) different scenarios or settings, which may be selected (often automatically by the laser system) based on the distance from the tip of the optical fiber to the target. In a first exemplary scenario, the index bubble expands to a sufficiently large distance and is close enough to the target for delivery of laser energy. In a second exemplary scenario, the expansion of the index bubble alone is not sufficient to achieve close enough proximity to the target, and at least a second bubble is required to further expand the gas path before the target can be treated. In the first scenario, and in accordance with the present disclosure (see, for example, the various V-shaped techniques described below), once the index bubble is created, the power of the laser is modulated downward until the index bubble is close enough to the target. Once the index bubble is close enough to the target, the power of the laser is modulated upward to treat the target. In the second scenario, and in accordance with the present disclosure (see, e.g., the various resonance modulation techniques described below), once the index bubble is generated, the laser power is modulated down, and when the second or third bubble reaches the target, the laser power is modulated up again to treat the target, and when the gas path begins to tear, the laser power is modulated down again.

[0049] As discussed above, different wavelengths and types of laser radiation have different absorption rates in a liquid working environment. Therefore, "close enough" to a target is a function of the laser and can represent different distances for different lasers. As discussed above in connection with Figures 3B and 4B, the slope of the effective laser pulse rise profile experienced by the target also reflects this distance. For example, thulium lasers are more strongly absorbed in liquids than holmium lasers. Therefore, the target can begin to experience some laser power effects only when the gas path reaches a distance to the target that is approximately the distance that thulium laser photons can travel in a liquid. However, because holmium laser photons can travel a longer distance in a liquid environment than thulium, the slope of the effective laser pulse rise is not as steep. Therefore, close enough to a target for a thulium laser is a shorter distance than for a holmium laser. It will be appreciated that the present disclosure may be realized and practiced with different lasers, and therefore the concept of close enough is a function of the laser used and the distance its photons can travel in the liquid environment.

[0050] Bubble dynamics generally have two phases: expansion followed by collapse. Furthermore, this dynamics has its own time constant. During this bubble expansion period, there is nothing inside the bubble to push against (i.e., there is no or little absorbing medium inside the bubble), so further application of laser pulse power (power = energy rate) does not appear to have an effective effect on the bubble itself.

[0051] Using the harmonic analogy of the motion of a playground swing, to effectively increase the swing amplitude, the "push" frequency should match the natural frequency of the swing. In other words, a pulse will be most effective at increasing bubble size if it is "resonant" with the bubble's natural frequency (f≈1 / 200 [us]≈5000 [Hz]). Thus, various embodiments described herein may modulate the laser pulse based on the bubble's natural frequency.

[0052] In various embodiments, the laser pulse can be modulated based on the bubble's natural frequency as follows: A quasi-continuous wave (QCW) laser, such as a TFL, suitable for being powered up and down during long quasi-continuous pulses can be used. In many embodiments, powering up and down during quasi-continuous pulses can be achieved by generating a varying power. Furthermore, the varying power can be generated by driving a pump laser source with a variable current while integrating over time to provide the desired pulse energy (PE). In various embodiments, the overall integral of the modulated power over time is equal to the desired PE as defined by the user. According to some embodiments, the power is highest at the beginning of the pulse, e.g., the maximum power that can be provided by the system.

[0053] Once the index bubble is initiated, the power can then preferably be reduced until the bubble reaches its maximum size, thus providing a "reserve" of laser energy that can be better utilized to impact the target when the gas path approaches the target sufficiently. When the bubble begins to collapse, the power can preferably be varied back to its maximum level. This should be repeated periodically, with the period approximately equal to or substantially equal to the bubble lifetime.

[0054] In some cases, the target may move (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 vary depending on the person's anatomy or the actual access of the target by the laser fiber tip, or the destruction of the target during the procedure. Therefore, the power variation technique may be modified based on the distance between the laser fiber tip and the target. For example, if the distance to the target is changed (e.g., due to movement of the target and / or optical fiber, changes in the patient's anatomy or the target, etc.), such distance changes may be measured, monitored, or estimated, so that the laser power may be adjusted accordingly on the fly. Therefore, if the distance increases / decreases, the system may recalculate the required pulse length to produce a sufficient effective pulse and / or expose the target to sufficient laser energy to meet the required clinical effect. For example, for a distant target, the number of cycles may be increased to provide a clear, stable, and fluid-free path from the laser fiber tip to the target.

[0055] FIG. 6 illustrates an example diagram 600 of laser pulse power modulation 604 relative to bubble size 602, according to one or more embodiments described herein. In various embodiments, diagram 600 includes an example 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 utilized to implement the pulse (see, e.g., laser system 900). The pulse power modulation 604 is illustrated by the sinusoidal pattern shown in the hatched area. In this case, the power is modulated from a high level of 500 W to a low level of 300 W. According to this aspect of the disclosure, the laser power of the long pulse is modulated in the opposite direction to the bubble dynamics described above, such that when the bubble expands, the laser is modulated down and when the bubble collapses, the laser is modulated up. The embodiments are not limited in this context.

[0056] FIG. 7 illustrates an example diagram 700 of modulated and unmodulated laser pulses and associated bubble dynamics according to one or more embodiments described herein. Diagram 700 shows an example 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. Diagram 700 includes pulse power on a first Y-axis 706, bubble size on a second Y-axis 708, and time on an X-axis 710. In various embodiments, FIG. 7 can accommodate a bubble path resonance modulation technique. For example, a laser pulse can be matched to the bubble dynamics to induce bubble size resonance, resulting in increased energy delivery to the target.

[0057] The flat, unmodulated long pulse 704a shown in FIG. 7 can cause a cascade of bubbles that expand and collapse in a sinusoidal pattern (corresponding to bubble dynamics 704b). Furthermore, the bubbles from the unmodulated pulse 704a repeatedly grow to approximately the same size and collapse to approximately zero size in an uncontrolled manner. In other words, since there is no mechanism for controlling or synchronizing the timing and / or location of the bubble collapse with the laser power pulse, there is only random constructive and destructive interaction. As will be appreciated, the amount of energy invested in the process is equal to the area under the pulse power line 704a (integral of power over time). However, if the laser power is modulated in the opposite direction to the bubble dynamics (see 702a, 702b), energy is conserved during the bubble expansion period. Furthermore, higher energy modulation during the bubble collapse period reduces the pace of collapse and accelerates the formation of the next bubble. The accelerated creation of the second bubble occurs before the preceding bubble collapses to zero size and disappears. Therefore, the second bubble begins on the "shoulder" of the first bubble and reaches a greater distance. Therefore, many embodiments described herein may utilize a pulse modulation scheme (e.g., 702a) whereby the same distance reached by the unmodulated pulse 704a is reached while using less laser energy.

[0058] FIG. 8 illustrates an example diagram 800 according to one or more embodiments described herein. Diagram 800 shows an example pulse modulation scheme 810 and its associated bubble dynamics 812. Diagram 800 includes pulse power on a first Y-axis 802, bubble size on a second Y-axis 804 (with a target position line 808 at 2 mm), and time on an X-axis 806. In various embodiments, FIG. 8 may correspond to a bubble path resonance modulation technique. For example, a target distance may be utilized to generate correspondingly sized bubbles prior to delivering a pulse burst.

[0059] The pulse modulation 810 illustrated in diagram 800 acts in the opposite direction on bubble size dynamics 812. In this example, the target is located 2 mm from the tip of the optical fiber (see line 808). As shown in the illustrated embodiment, when the bubble size begins to decrease, the laser power is modulated upward so that the bubble does not collapse to zero size, or at least the collapse is reduced. Every successive bubble builds on the "shoulder" of its predecessor, creating a staircase pattern until the gas path reaches near the target. As used herein, near the target may be taken to mean at or below 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 approximately 0.1 mm when using a thulium laser and approximately 0.5 mm when using a holmium laser.

[0060] Once the gas pathway is established, the laser power can be switched (or increased) to its maximum power (or power setting associated with the desired treatment) so that the majority of the pulse energy can be delivered to the target. In various embodiments, laser energy transfer in liquid media can be a function of the laser pulse shape in air, the dynamics of the bubble front over time, and the delay between the start of the laser pulse and the start of the bubble.

[0061] While the above discussion is generally directed to treating targets at a distance, an alternative pulse modulation profile for improving energy delivery at relatively close target distances may be referred to as "V-shaped." In various embodiments, a close target may be defined as a target located at a distance that can be bridged only by an index bubble, and a distant target may be defined as a target located at a distance that is two to four times the size of the index bubble, requiring a "train of bubbles" to deliver sufficient energy to the target. Different lasers may result in different index bubble sizes. For example, the index bubble of a holmium laser may be approximately 1 mm to 2 mm, while the index bubble of a thulium laser may be approximately 0.5 mm to 1 mm.

[0062] In various embodiments, the V-shaped pulse modulation can have one or more of the following profile characteristics: (a) start with maximum power to create the initial bubble, (b) reduce power while the bubble expands, and (c) increase power back to maximum while the bubble is at its maximum size or when the bubble is expected to reach the target (whichever comes first). In various embodiments, this V-shaped pulse modulation results in more efficient energy delivery than the short mode of the holmium laser (which resembles a downward-sloping triangle) because it delivers more pulse energy during the bubble expansion phase and therefore encounters less water absorption.

[0063] In various embodiments, the laser power and the distance between the fiber tip and the target can be provided as inputs for optimizing pulse modulation. The maximum size of the index bubble can be a function of the instantaneous pulse power during the first few tens of microseconds, as well as wavelength absorption in water, beam quality, and delivery fiber geometry. Therefore, for a given laser and delivery fiber, bubble dynamics for various peak powers can be measured, such as in a bench setup. A lookup table can be created to tabulate the relationship between peak and / or initial power, fiber size, and wavelength, and the maximum bubble size, the time from the start of laser firing to the onset of bubble formation (t0), the time to reach maximum bubble size (tmax), and the time to collapse (tc). From this information, the initial modulation frequency can be roughly obtained as 1 / (tc - tmax - t0). Further insight into the dynamic adjustment of modulation frequency can be derived through experimental observation in a bench setup of the effect of varying modulation frequency on vapor tunnel stability and energy delivery distance without departing from the scope of this disclosure. The index bubble size as a function of time can be strongly dependent on the pulse (peak) power and the liquid's absorptivity at the laser wavelength, which can be used to estimate the time at which the index bubble reaches its maximum size and begins to collapse.

[0064] 9 illustrates an exemplary laser system 900 according to one or more embodiments described herein. In various embodiments, the laser system 900, or one or more components thereof, may be utilized to implement one or more of the techniques described herein, such as one or more 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 optical fiber 924), a connector 925, a partially transparent mirror 926A, a partially transmissive 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 (not shown). In various embodiments, a known device (e.g., an endoscope) may be utilized to introduce laser fiber 924 into a body cavity to position the tip of laser fiber 924 near a target, such as a kidney stone or other urinary tract stone or prostate, to be treated by ablation or extraction. One or more components of FIG. 9 , or aspects thereof, may be incorporated into other embodiments of the present disclosure or may be omitted from the described embodiments without departing from the scope of the present disclosure. For example, distance measurement module 929 and / or photodetector 927 may be omitted from laser system 900 without departing from the scope of the present disclosure. The embodiments are not limited in this context.

[0065] A laser source 921 of the system 900 may generate a laser beam 923, which is transmitted through a connector 925 to a laser fiber 924 and from there to a target. The system also includes a controller 922. FIG. 9 schematically illustrates one embodiment of the present invention. The laser system 900 includes a laser module 921 and a control unit 922. The laser beam 923 from the laser source 921 is configured to pass through the connector 925 and reach the optical fiber 924. A partially transparent mirror 926A positioned along the optical path of the beam 923 is configured to reflect at least a portion of the beam 923 into a photodetector module 927. A portion of the backscattered light from the target enters the optical fiber 924, passes through the connector 925, and is partially transmitted to the target mirror 926B, which then enters a distance measurement module 929. The module 929 is configured to measure the distance between the tip of the optical fiber 924 and the target. Modules 927 and 929 are also controlled by programmable controller 922. In some embodiments, during operation, programmable controller unit 922 may receive from module 927 a first electrical signal indicative of the energy level of the laser pulse and / or from distance measurement module 929 a second electrical signal indicative of a change in distance between the tip of optical fiber 924 and the target. In various embodiments, laser system 900 may be configured to adjust one or more operating parameters, such as the amount of current supplied to the lasing element, based on at least one of the first and second beacon signals to maintain the energy level within the target parameters and in accordance with any dynamic changes in laser performance or distance to the target. Some aspects of system 900 are described in more detail in U.S. Pat. No. 10,231,781 (the '781 patent), the disclosure of which is incorporated herein by reference in its entirety.

[0066] It will be appreciated that one or more embodiments described herein may be implemented without one or more of the photodetector 927 and the distance measurement module 929. In some embodiments, the distance between the fiber tip and the target may be an expected distance or a predetermined distance. For example, the predetermined distance may be based on the mode of the laser system. In another example, the predetermined distance may be based on user input. Furthermore, in some embodiments, a modulation scheme may be selected based on the mode of operation and / or user input.

[0067] In various embodiments, the controller 922 may include a processor and a memory comprising 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 output 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. In other embodiments, the distance may be provided as an input to the controller 922. For example, a distance measurement module 929 may provide the distance as an input to the controller 922. Techniques for determining the distance between the tip of the laser fiber and the target 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 regulate the amount of power provided to the laser fiber and, in the context of this disclosure, the variable power configurations (modulation schemes) described herein.

[0068] In many embodiments, laser system 900 may operate in different modes for near and distant targets. As previously described, for example, V-shaped optimization may be utilized to determine the pulse modulation scheme for near targets, and resonant modulation optimization may be utilized to determine the pulse modulation scheme for distant targets. In various embodiments, controller 922 may determine which optimization and / or modulation scheme to use based at least in part on the distance to the target.

[0069] In the case of V-shaped optimization for a nearby target, inputs may include pulse energy and nearby (“touching” / “near”) target. As explained above, the term “close” can mean that the target is within a distance from the tip of the laser fiber 924 that can be bridged only by the index bubble. In such a scenario, the initial pulse power may be determined to deliver a bubble approximately (or substantially) one to two times the size of the distance to the target. Maximum energy delivery may occur while the bubble is at or above the distance to the target. Thus, in some embodiments, bubble size may be used to control the amount of time that maximum energy is delivered to the target. For example, a bubble size approximately twice the distance to the target may be used to deliver maximum energy for a relatively long period of time, while a bubble size approximately equal to the distance to the target may be used to deliver maximum energy for a relatively short period of time. In some embodiments, the controller 922 may determine the initial pulse power. The laser may be fired at the initial pulse power and then modulated downward until the bubble approaches its maximum size. The pulse power may then be increased to its maximum. In some embodiments, if the initial pulse power is equal to the maximum power, the system may begin at the maximum power, reduce the power during the bubble expansion period, and then increase it again to the maximum power when the bubble is at its maximum size. Finally, the pulse may be terminated when the integral (power x time) equals the required pulse energy. As used herein, "maximum power" may not refer to the maximum power that the laser source can deliver, but instead may refer to the power level for the desired treatment or procedure.

[0070] For resonance modulation optimization for a distant target, inputs may include pulse energy and the distant target ("remote" mode). The initial pulse power may be set to the maximum system power. For example, the controller 922 may set the initial pulse power to a maximum level based on a classification of the target as distant based on a distance estimate. The laser may be fired at a maximum power level and then modulated downward during the bubble expansion period. Once the bubble reaches its maximum size, the power may be modulated back up to the maximum. The modulation may then be cycled with a period ranging from 0.5 to 1.5 times the bubble expansion / collapse dynamics (e.g., 0.7 to 1.3 times the time from inception to collapse) to achieve a resonance effect. In various embodiments, the period may be adjusted for each successive bubble in the bubble train due to, for example, changes in the distance to the target. If the bubble train is expected to bridge the distance to the target, the pulse power may be increased to a maximum to utilize minimal liquid along the laser path between the fiber tip and the target. Finally, when the integral (power x time) equals the desired pulse energy, the pulse can be terminated.

[0071] In one embodiment, a method of operating the laser system 900 may include one or more of the following exemplary steps of operating the laser system 900 configured to implement one or more pulse modulation schemes described herein. In step 1, a user selects the type of fiber to use. According to one embodiment, the user may manually select the type of fiber to be used in the procedure. According to another embodiment, an automatic fiber recognition system may be implemented. In step 2, the user may select the required treatment energy level. The pulse energy defined by the user for the treatment may be the overall energy expected to be emitted by the laser system in the modulated pulses. In other words, and as discussed below, the system may be programmed and configured to set up the pulse modulation scheme in a manner that is transparent to the user using a suitable programmable controller. For example, the user in this embodiment may not be required to set up values ​​for various parameters.

[0072] In step 3, the user may select the modulation scheme repetition rate (e.g., the time between modulated pulses). In step 4, the user may select the desired (average) working distance between the tip of the fiber and the target tissue. According to another embodiment, the working distance may be automatically detected by the system, for example, by using distance estimation techniques such as those described in U.S. Patent Application No. 13 / 811,926, the entire contents of which are incorporated herein by reference. In step 5, based on previously manually loaded or automatically detected parameters, the system may automatically define or calculate working values ​​for one or more of peak power, initial power, fiber size, wavelength, maximum bubble size, time from the start of laser firing to the onset of bubble formation (t), time to reach maximum bubble size (t), and time to collapse (t) from a look-up table operatively associated with the programmable controller.

[0073] In step 6, pulses may be fired according to the modulation scheme. In various embodiments, the system may be configured to measure the actual values ​​of each pulse / modulation scheme. In steps 7 and 8, the system may be configured to compare the measured values ​​with the predefined values ​​in step 5. Should the measured parameters deviate from the predefined parameters, the system automatically corrects such deviation in step 9, and a new set of operating parameters is sent to the programmable controller for implementation in the next modulation scheme by repeating step 6. In this way, the system may maintain the actual operating values ​​within a predefined range. It should be understood that during step 7, the system may be configured to measure different parameters that may be related to the actual laser pulse energy.

[0074] For example, according to one embodiment, the system may use a 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 the current or voltage pulses sent to the laser excitation energy source. As such, a feedback loop may be configured to feed back 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.

[0075] In some embodiments, the method of operating laser system 900 may be loosely based on Figures 3A and 3B of the '781 patent and the sequence of laser firing described herein, as illustrated in the flowchart of Figure 10, taking into account, of course, any differences in the laser source.

[0076] FIG. 10 illustrates an exemplary process flow 1000 (or method 1000) according to one or more embodiments described herein. In process flow 1000, a subset of operational steps may include measuring a distance from a laser fiber tip to a target at block 1002. For example, controller unit 922 may determine the distance between the tip of laser fiber 924 and the target. More specifically, circuitry in controller unit 922 and / or distance measurement module 929 may execute instructions and / or receive signals to determine the distance between the tip of laser fiber 924 and the target. At decision block 1004, if the measured distance is less than distance (D)X or is equal to or less than distance (D)X, method 1000 may transition to a V-mode. However, if distance D is greater than distance X or is equal to or greater than distance X, the method may transition to a modulation mode of operation. In various embodiments, the distance X may be determined experimentally and the results recorded in a lookup table that includes the distance and other parameters, such as the number of pulses and the power applied per pulse. It should also be noted that because the target may move in its environment, such as a kidney stone, the controller may be dynamic in nature and capable of adjusting parameters for the laser, including changing from V-shaped mode to resonant modulation mode and vice versa, based on repeatedly determining the distance D and repeatedly determining whether the distance D is greater than or less than X. The embodiments are not limited in this context.

[0077] After a mode is selected (e.g., in block 1006 or block 1020), method 1000 includes selecting parameters for the selected mode. For example, controller 924 can select the number of pulses and the energy level to be applied to the target (blocks 1008, 1022). More specifically, if V mode is selected in block 1006, controller 924 can select the energy level of the pulses, and if resonant mode is selected in block 1020, controller 924 can select the energy level of the pulses and the modulation frequency for the pulses.

[0078] Following blocks 1010 and 1024, method 1000 may include sending a control signal to laser source 921 to activate the laser source and emit a laser beam (blocks 1010, 1024), after which method 1000 may include an operation by controller 924 to calculate the pulse energy to be delivered to the target (blocks 1012, 1026). For example, controller 924 may determine the pulse energy to be delivered to the target (or receive a signal from a sensor comprising an indication of the pulse energy). Also, in block 1012 or 1026, controller 924 may estimate one or more of the number of effective pulses to be experienced by the target, the effective energy per effective pulse to be delivered to the target, or the accumulated effective energy over the number of effective pulses to be delivered to the target. Furthermore, for a selected energy level, such as may be selected by a user, controller 924 may select power modulation and bubble path modulation resonant frequencies so that the selected energy is actually delivered to the target in one of the more effective pulses.

[0079] If the controller selection is sufficient to achieve the desired effect (stone breaking, crushing, etc.) (blocks 1014, 1028), the operator, observing the extent of the treatment, may stop the system (blocks 1016, 1032); vice versa if the effect is not achieved (blocks 1018, 1030). Thus, method 1000 may include receiving an indication from an operator (e.g., a physician, etc.) that the treatment is sufficient or not. Based on the received indication, method 1000 may either terminate (blocks 1016, 1032) or repeat (blocks 1018, 1030), or alternatively, return to block 1002. In this manner, the operator may provide an indication to the system (e.g., system 900), and system 900 may receive the indication and further or additional treatments may be performed to achieve the desired effect. The process may be dynamically adjusted using a closed feedback loop connected to the controller. So, for example, if the distance to the target changes during the procedure, a closed feedback loop may provide that information to the controller, which may then cause the controller to change the parameters of the procedure.

[0080] 11 illustrates a flowchart 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 the various configurations and embodiments described above. However, it should be appreciated that the method 1100 may be implemented using a system different from the system described herein. The embodiments are not limited in this context.

[0081] At block 1102, the method 1100 includes determining a pulse energy of the fiber laser. For example, the controller 922 may determine the pulse energy of 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 the tip of the fiber laser and the target, where a liquid is located between the tip of the fiber laser and the target. For example, the controller 922 may identify and determine the 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.

[0082] At block 1108, method 1100 includes setting an initial pulse power of a modulation scheme to generate index bubbles in the liquid based on the distance. For example, if the distance exceeds a threshold distance, the initial pulse power may be set to the maximum system power. In another example, if the distance is below a threshold distance, the initial pulse power may be set to provide bubbles having a size between one and two times the distance to the target. In some such examples, a lookup table may be used to determine the initial pulse power that will provide bubbles having a size between one and two times the distance to the target. At block 1110, method 1100 includes initiating a pulse according to a modulation scheme via the fiber laser, the modulation scheme reducing the power of the pulse after initiating the pulse at the initial pulse power. For example, controller 922 may initiate a pulse according to modulation scheme 702a or modulation scheme 810 via laser source 921 and laser fiber 924.

[0083] 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 comprise controller 922. In some such embodiments, computer system 1200 may be utilized to control operation of laser system 900 relative to a target. The embodiments are not limited in this context.

[0084] The computer system 1200 may include a central processing unit ("CPU" or "processor") 1202. The processor 1202 may include at least one data processor for executing program components for executing user- or system-generated business processes. A user may include a person using a device such as those included in this disclosure, or such a device itself. The processor 1202 may include dedicated processing units, such as an integrated system (bus) controller, memory management control unit, floating-point unit, graphics processing unit, digital signal processing unit, etc. The processor 1202 may be arranged to communicate with input devices 1211 and output devices 1212 via an input / output interface 1201. The input / output interface 1201 may employ communication protocols / methods such as, without limitation, audio, analog, digital, stereo, IEEE-1394, serial bus, Universal Serial Bus (USB), infrared, PS / 2, BNC, coaxial, component, composite, Digital Visual Interface (DVI), High-Definition Multimedia Interface (HDMI), radio frequency (RF) antenna, S-video, Video Graphics Array (VGA), IEEE 802.n / b / g / n / x, Bluetooth, cellular (e.g., Code Division Multiple Access (CDMA), High-Speed ​​Packet Access (HSPA+), Global System for Mobile Communications (GSM), Long Term Evolution (LTE), WiMax, etc.), and others.

[0085] Using input / output interface 1201, computer system 1200 may communicate with input devices 1211 and output devices 1212. In some embodiments, processor 1202 may be arranged to communicate with communications network 1209 via network interface 1203. In various embodiments, communications network 1209 may be utilized to communicate with remote devices 1220, such as to access lookup tables or utilize external resources. Network interface 1203 may communicate with communications network 1209. Network interface 1203 may employ connection protocols including, without limitation, direct connect, Ethernet (e.g., twisted pair 10 / 100 / 1000 Base T), Transmission Control Protocol / Internet Protocol (TCP / IP), Token Ring, IEEE 802.11a / b / g / n / x, etc. 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 comprise 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.).

[0086] The communication network 1209 can be implemented as one of different types of networks, such as an intranet or local area network (LAN), a closed area network (CAN), and the like. The communication network 1209 can be a dedicated network or a shared network, which represents an association of different types of networks communicating with each other using various protocols, such as Hypertext Transfer Protocol (HTTP), CAN protocol, Transmission Control Protocol / Internet Protocol (TCP / IP), Wireless Application Protocol (WAP), etc. Furthermore, the communication network 1209 can include various network devices, including routers, bridges, servers, computing devices, storage devices, etc. In some embodiments, the processor 1202 can be arranged to communicate with memory 1205 (e.g., RAM, ROM, etc. not shown in FIG. 12 ) via a storage interface 1204. The storage interface 1204 may include, without limitation, memory drives, removable disk drives, etc., and may connect to the memory 1205 employing connection protocols such as Serial Advanced Technology Attachment (SATA), Integrated Drive Electronics (IDE), IEEE-1394, Universal Serial Bus (USB), Fibre Channel, Small Computer System Interface (SCSI), etc. The memory drive may further include a drum, magnetic disk drive, magneto-optical drive, optical drive, redundant array of independent disks (RAID), solid state memory device, solid state drive, etc.

[0087] Memory 1205 may store a collection of program or database components, including, without limitation, a user interface 1206, an operating system 1207, a web browser 1208, and instructions 1215, among others. In various embodiments, instructions 1215 may include instructions that, when executed by processor 1202, cause processor 1202 to perform one or more techniques, processes, procedures, and / or methods described herein, such as estimating distance or performing a calibration. For example, instructions for performing method 380 may be stored in memory 1205. In many embodiments, 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, etc., as described in this disclosure. Such a database may be implemented as a fault-tolerant, relational, scalable, secure database, such as Oracle® or Sybase®.

[0088] Operating system 1207 may facilitate resource management and operation of computer system 1200. Examples of operating systems include, without limitation, APPLE® MACINTOSH® OS X®, UNIX®, UNIX-like system distributions (e.g., BERKELEY SOFTWARE DISTRIBUTION (BSD), FREEBSD®, NETBSD™, OPENBSD™, etc.), LINUX® distributions (e.g., RED HAT®, UBUNTU®, KUBUNTU™, etc.), IBM® OS / 2®, MICROSOFT® WINDOWS® (XP®, VISTA® / 7 / 8, 10, etc.), APPLE® IOS®, GOOGLE® ANDROID®, BLACKBERRY® OS, etc. User interface 1206 may facilitate the display, execution, interaction, manipulation, or operation of program components through textual or graphical features. For example, the user interface may provide computer interaction interface elements, such as cursors, icons, check boxes, menus, scrollers, windows, widgets, etc., on a display system operatively connected to computer system 1200. Graphical user interfaces (GUIs) may be employed including, without limitation, Apple® Macintosh® operating system Aqua®, IBM® OS / 2®, Microsoft® Windows® (e.g., Aero, Metro, etc.), web interface libraries (e.g., ActiveX®, Java®, JavaScript®, AJAX, HTML, Adobe® Flash®, etc.), etc.

[0089] In some embodiments, computer system 1200 may implement program components stored in web browser 1208. Web browser 1208 may be a hypertext browsing application such as MICROSOFT® INTERNET EXPLORER®, GOOGLE® CHROME®, MOZILLA® FIREFOX®, APPLE® SAFARI®, etc. Secure web browsing may be provided using Secure Hypertext Transfer Protocol (HTTPS), Secure Sockets Layer (SSL), Transport Layer Security (TLS), etc. Web browser 1208 may utilize features such as AJAX, DHTML, ADOBE® FLASH®, JAVASCRIPT®, JAVA®, application programming interfaces (APIs), etc. In some embodiments, computer system 1200 may implement program components stored in a mail server. The mail server may be an Internet mail server such as Microsoft Exchange. The mail server may utilize functionality such as Active Server Pages (ASP), ACTIVEX®, ANSI® C++ / C#, MICROSOFT®, .NET, CGI SCRIPTS, JAVA®, JAVASCRIPT®, PERL®, PHP, PYTHON®, WEBOBJECTS®, etc. The mail server may utilize communication protocols such as Internet Message Access Protocol (IMAP), Messaging Application Programming Interface (MAPI), MICROSOFT® Exchange, Post Office Protocol (POP), Simple Mail Transfer Protocol (SMTP), etc. In some embodiments, computer system 1200 may implement program components stored in a mail client.The email client can be an email viewing application such as APPLE® MAIL, MICROSOFT® ENTOURAGE®, MICROSOFT® OUTLOOK®, MOZILLA® THUNDERBIRD®, or the like.

[0090] Additionally, one or more computer-readable storage media may be utilized in implementing embodiments consistent with the present disclosure. A computer-readable storage medium refers to any type of physical memory in 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 processor to perform steps or stages consistent with the embodiments described herein. The term "computer-readable medium" should be understood to include tangible items and exclude carrier waves and transitory signals, i.e., non-transitory. Examples include random access memory (RAM), read-only memory (ROM), volatile memory, non-volatile memory, hard drives, compact disc (CD) ROMs, digital video discs (DVDs), flash drives, disks, and any other known physical storage medium.

[0091] In general, it will be understood by those skilled in the art that the terms used herein are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including, but not limited to," the term "having" should be interpreted as "having at least," the term "including" should be interpreted as "including, but not limited to," etc.). It will also be understood by those skilled in the art whether a particular number of introduced claim recitations is intended. For example, as an aid to understanding, the detailed description may contain the use 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 as suggesting that introducing a claim recitation with the indefinite article "a" or "an" limits any particular claim containing such introduced claim recitation to a disclosure containing only one of such recitations, even if the same claim includes the introductory phrase "one or more" or "at least one" and the indefinite article "a" or "an" (e.g., "a" and / or "an" should typically be interpreted to mean "at least one" or "one or more"). The same applies to the use of definite articles used to introduce claim recitations. Also, those skilled in the art will recognize that even if a specific number of introduced claim recitations is explicitly recited, such a recitation should typically be interpreted to mean at least the recited number (e.g., a minimum recitation of "two recitations" without other modifiers typically means at least two recitations, or more than two recitations).

[0092] All of the devices and / or methods disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. While the devices and methods of the present disclosure have been described in terms of preferred embodiments, it may be apparent to those skilled in the art that variations can be applied to the devices and / or methods and in the steps or sequence of steps of the methods described herein without departing from the concept, spirit, and scope of the present 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 present disclosure, as defined by the appended claims.

Claims

1. a fiber laser; a controller comprising a processor and a memory, the memory comprising instructions that, when executed by the processor, cause the processor to: determining a pulse energy of the fiber laser; identifying a distance between a tip of the fiber laser and a target, wherein a liquid is located between the tip of the fiber laser and the target; determining a modulation scheme based on said distance; setting an initial pulse power of the modulation scheme to generate an index bubble in the liquid based on the distance; initiating a pulse through the fiber laser according to the modulation scheme, the modulation scheme reducing the power of the pulse after initiation of the pulse at the initial pulse power; A system that allows the following to be performed.

2. 2. The system of claim 1, wherein the modulation scheme increases the power of the pulse to a maximum system power level when the index bubble is estimated to reach a maximum size.

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

4. The instructions, when executed by the processor, cause the processor to: identifying an updated distance between the tip of the fiber laser and the target; determining an updated modulation scheme based on the updated distance; and The system according to claim 1 , further comprising:

5. 5. The system of claim 1, wherein the modulation scheme is configured to modulate pulse power downward during an expansion period of the index bubble and modulate pulse power upward during a collapse period of the index bubble.

6. 6. The system of claim 1, wherein the modulation scheme comprises an initial modulation frequency, and the instructions, when executed by the processor, further cause the processor to determine the initial modulation frequency based on a time to collapse of the index bubble, a time to reach a maximum size of the index bubble, and a time from start of laser emission to start of bubble formation.

7. 7. The system of claim 1, wherein the instructions, when executed by the processor, further cause the processor to set the initial pulse power of the modulation scheme to generate the index bubble in the liquid based on the distance and the pulse energy.

8. 8. The system of claim 1, 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 integral of the power of the pulse with respect to time equals the pulse energy.

9. 10. The system of claim 1, wherein 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.

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

11. determining a pulse energy of the fiber laser; identifying a distance between a tip of the fiber laser and a target, wherein a liquid is located between the tip of the fiber laser and the target; determining a modulation scheme based on said distance; setting an initial pulse power of the modulation scheme to generate an index bubble in the liquid based on the distance; initiating a pulse via the fiber laser according to the modulation scheme, the modulation scheme reducing the power of the pulse after initiation of the pulse at the initial pulse power.

12. 12. The method of claim 11, comprising modulating pulse power downward during expansion of the index bubble and modulating pulse power upward during collapse of the index bubble.

13. 13. The method of claim 11 or 12, comprising classifying a 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. 14. The method of claim 13, comprising cycling at a period between 0.7 and 1.3 times the time from inception to collapse of the index bubble.

15. 15. The method of any one of claims 11 to 14, wherein the modulation scheme increases the power of the pulse to a maximum system power level when the index bubble is estimated to reach a maximum size.

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