APPARATUS AND METHOD FOR ENHANCING LASER BEAM EFFICACY IN A LIQUID MEDIUM

Abstract

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 scheme are described including modulating pulse power down during expansion of an index bubble and modulating pulse power up during collapse of the index bubble.

Description

RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. § 119 to U.S. Provisional Patent Application No. 63/118,117, titled “Apparatus and Method for Enhancing Laser Beam Efficacy in a Liquid Medium”, filed on Nov. 25, 2020, the entirety of which is incorporated herein by reference.

This application claims the benefit of priority under 35 U.S.C. § 119 to U.S. Provisional Application No. 63/118,857, titled “Method and System for Estimating Distance Between a Fiber End and a Target”, filed on Nov. 27, 2020, the entirety of which is incorporated herein by reference.

This application claims the benefit of priority under 35 U.S.C. § 119 to U.S. Provisional Patent Application No. 63/252,830, titled “Method and System for Estimating Distance Between a Fiber End and a Target”, filed on Oct. 6, 2021, the entirety of which is incorporated herein by reference.

TECHNICAL FIELD

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.

BACKGROUND

Lasers are widely used for performing various medical treatments such as tissue coagulation, ablation, cutting, fragmenting, dusting and enucleation. Laser treatments are conducted through and within various mediums and environments such as gases, solids, and liquids. During laser treatments, the interaction between the laser radiation and a target object (e.g., body tissue such as prostate, kidney, or urinary stones), depends on the laser used and, among other things, on the absorption, reflection, and dispersion of the environment and the target object. Ureteral stones, kidney stones, or prostate are only three examples of common targets which may be treated by a laser. Typically, the treatment environment may be saline or other similar liquids. The efficiency of laser treatment may be a function of the interaction between the laser energy and target. The portion of the laser energy that reaches and is absorbed by the target contributes to the required surgical effect. However, the laser energy absorbed by the environment medium can be considered lost energy, which is no longer available for target treatment. Oftentimes, laser parameters, such as wavelength, may be selected based on the desired clinical effect and the 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 for prostate ablation or enucleation.

BRIEF SUMMARY

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 as an aid in determining the scope of the claimed subject matter.

In one aspect, the present disclosure relates to a system, comprising a fiber laser and a controller. The controller may include a processor and memory. The memory may include instructions that when executed by the processor cause the processor to perform one or more of: determine a pulse energy for the 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 for 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 power of the pulse after initiation of the pulse at the initial pulse power.

In some embodiments, the modulation scheme increases power of the pulse to a maximal system power level at a time estimated for the index bubble to reach maximal size. In some such embodiments, the instructions, when executed by the processor, further cause the processor to estimate the time the index bubble takes to reach maximal 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; and determine an updated modulation scheme based on the updated distance.

In several embodiments, the modulation scheme is configured to modulate pulse power down during expansion of the index bubble and modulate pulse power up during collapse of the index bubble.

In many embodiments, 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 for the index bubble to reach maximum size, and a time from lasing initiation to start of bubble formation.

In some embodiments, the instructions, when executed by the processor, further cause the processor to set the initial pulse power for the modulation scheme to generate the index 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 integral of the power of the pulse with respect to time equals the pulse energy.

In several embodiments, the instructions, when executed by the processor, further cause the processor to classify the target as distant target based on the distance and set the initial pulse power to a maximal system power level based on classification of the target as distant. In several such embodiments, the modulation scheme is configured obtain a resonant effect by cycling at periods between 0.7 and 1.3 times a time from start to collapse of the index bubble.

In another aspect, the present 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 perform one or more of: determine a pulse energy for 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 for 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 power of the pulse after initiation of the pulse at the initial pulse power.

In some embodiments, the modulation scheme increases power of the pulse to a maximal system power level at a time estimated for the index bubble to reach maximal 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 the index bubble takes to reach maximal 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: 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.

In several embodiments, the set of instructions, in response to execution by the processor circuit, further cause the processor circuit to set the initial pulse power for the modulation scheme to generate the index 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 integral 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 a pulse energy for 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 for 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 power of the pulse after initiation of the pulse at the initial pulse power.

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

In various embodiments, the method includes classifying the target as distant target based on the distance and set the initial pulse power to a maximal system power level based on classification of the target as distant. In various such embodiments, the method includes cycling at periods between 0.7 and 1.3 times a time from start to collapse of the index bubble.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting embodiments of the present disclosure are described by way of example with reference to the accompanying figures, which are schematic and not intended to be drawn to scale. In the figures, each identical or nearly identical component illustrated is typically represented by a single numeral. In will be appreciated that 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 appear hidden. For purposes of clarity, not every component is labeled in every figure, nor is every component of each embodiment shown where illustration is not necessary to allow those of ordinary skill in the art to understand the disclosure. In the figures:

FIG. 1 illustrates an exemplary diagram of pulses of a Holmium laser and a Thulium laser according to one or more embodiments described herein.

FIGS. 2A and 2B illustrate various aspects of Holmium laser short pulses in different mediums according to one or more embodiments described herein.

FIGS. 3A and 3B illustrate various aspects of Thulium laser long pulses in different mediums 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 of images of bubble dynamics according to one or more embodiments described herein.

FIG. 6 illustrates an exemplary diagram of laser power modulated in relation to bubble size according to 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 a modulated laser pulse in conjunction with associated bubble dynamics according to one or more embodiments described herein.

FIG. 9 illustrates an exemplary laser system according to 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 embodiments 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 laser beam efficacy in a liquid medium, such as for a desired surgical effect on a target. The liquid environment of many treatment environments tends to absorb a significant portion of laser energy. For example, the liquid medium can absorb and attenuate the laser energy, leaving less energy available for the desired surgical effect on the target. Additionally, energy absorbed by the liquid medium can heat surrounding tissue, leading to unwanted safety issues and the need to irrigate the areas with cooling fluids.

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

Accordingly, it is one aspect of the present disclosure to optimize the available laser energy to treat a target based on an enhanced bubble path effect for targets which will be discussed in more detail below. The amount of energy needed to create a bubble path effect, that is, the creation of an air tunnel between a tip of an optical (or laser) fiber and a target, is also a function of the distance between the tip of the fiber and target. Therefore, it is another aspect of the present disclosure, to reduce the amount of laser energy which may be wasted to create the bubble path effect for a specific distance to a tissue target, and thus to increase the amount of laser energy available to treat the target. It is yet another aspect of the present disclosure to increase the distance of the bubble path effect and to reach targets further away from the laser fiber tip for a specific laser energy. Utilizing the present disclosure can result in less wasted energy when treating a tissue at a given distance or allow treating tissue further distances away from the laser fiber tip for a given level of energy.

In some bubble path effect technologies, 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 bubble (and the relative absence of fluid) and reaches the tissue with higher energy as compared to that of a single laser pulse traveling through a liquid medium only. Furthermore, the energies of the first and second pulse, as well as the time delay between the two pulses, may be varied to achieve a higher energy delivery to the tissue, which is present at various distances from a tip of the laser fiber.

Infrared lasers, such as Holmium (Ho) lasers, having a wavelength of 2100 nm and Thulium (Tm) lasers, having a wavelength in the range of 1940 nm to 1970 nm, are strongly absorbed in a liquid environment. For example, the photons at 1940 nm wavelength have an absorption coefficient of 110 [1/cm] and the photons at 2100 nm wavelength have the absorption coefficient of 25 [1/cm]. Typically, in a liquid environment, many of the photons produced by the Holmium laser are absorbed before the laser pulse travels a distance of 0.5 mm from where it exits the optical fiber while the photons produced by the Thulium lasers are absorbed before the laser pulse travels a distance of 0.1 mm from where it exits the optical fiber. In comparison, a solid-state Holmium laser is characterized by high peak power and relatively short pulses, while a Thulium fiber laser (TFL) is characterized by a lower peak power. Therefore, it takes a longer time for a TFL, compared to a solid-state Holmium laser, to generate an equal amount of energy. For example, a TFL will generate an energy of 0.5 Jules in a pulse duration of about 1 milliseconds (ms) while it takes about 0.2 ms for a solid-state Holmium laser to generate the same amount of energy. As will be further discussed below, it has been observed that the life cycle of a single bubble lasts about 0.2-0.3 ms. Moreover, it has been observed that the bubble, once initiated, has its own dynamic characteristics which is in many aspects unrelated to the laser pulse (except for the pulse's initial characteristics at a very short time frame of a few 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 3-4 bubble life cycles. The incorporated references mentioned above describe how to optimize the timing and the distribution of energies among the first and subsequent laser pulses to minimize the energy invested in bubble creation and maximize the amount of energy that reaches the target. Further, a Holmium laser with a reduced peak power may be used to extend the usual short pulse duration.

However, spreading a Holmium laser pulse energy over a longer pulse duration, like that in the above-mentioned Thulium pulse, may result in a pulse duration which is longer than the life cycle of a single bubble. As in the case with Thulium, a laser pulse which is longer than the life cycle of a single bubble results in the creation of a cascade of multiple bubbles. A cascade of multiple bubbles may create a gaseous pathway to the target. However, such a bubble cascade is characterized by sequence of independent bubbles, which expand and collapse at different times and at different locations along the pathway. As a result, the effective length of the gaseous pathway changes over time. Gaseous discontinuations along the pathway, at different times and locations, are filled with energy absorbing liquid and this will again increase attenuation of the pulse produced by the laser. Thus, the energy delivered to the target is frequently interrupted during these bubble collapses in an unpredictable fashion, resulting in multiple sub-pulses during the pulse duration and a significant waste of energy.

Accordingly, one or more embodiments described herein provide for effectively and efficiently manage the level of the laser energy along long laser pulses. In various embodiments, effective and efficient management of laser energy during long laser pulses can provide one or more of the following advantages: (i) laser energy delivered to the target at a given distance is increased, (ii) laser energy losses while the gaseous pathway to the target is being built are decreased, and (iii) stabilization of the pathway over the course of the pulse, as opposed to being subjected to stochastic collapses with unpredictable energy deliver results. Many embodiments optimize the energy distribution along long laser pulses.

Several embodiments described herein provide to reduce, or prevent, heat buildup in the surrounding tissues by more effectively delivering laser energy to a target at lower energy levels to achieve the same level of treatment. For example, laser energy may be delivered to a target at 30 W instead of 40 W while achieving the same level of treatment. Many embodiments may generate pulses that optimize the delivery of energy through a water environment. In many such embodiments, when formed, the optimized pulse 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 intended effect on tissue, such as fragmentation, dusting, pop-corning, etcetera (improved efficiency/efficacy); (2) using the same pulse energy to deliver energy to the target at a longer distance (better action at distance/action at longer distances); 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 outcomes, such as over-heating of surrounding tissue (improved safety profile).

In some embodiments, a laser with low peak-power and long pulses, such as a TFL, may be utilized so that the total size and stability of the bubble cascade generated is much longer (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, when comparing short pulse Ho to long pulse Tm, the latter travels further, as it travels through the longer train of bubbles produced by the TFL. Further, a longer pulse duration takes better advantage of the cascade of bubbles as the pulse persists while the bubbles reach the target. However, while it has been observed that the TFL pulses are severed into several sub-pulses due to the multiple bubble collapses, resulting in a widely variable 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, in many aspects it is no longer related to the characteristics of the laser pulse. An initial bubble formed by firing the laser first grows to a maximum size (dependent on the initial peak power of the pulse), and then collapses. The typical bubble duration for a Holmium laser is −200-300[μs]. Laser pulses which are longer than the life cycle of the bubble, create several bubbles, in a series, emanating from the laser fiber tip towards the target.

FIG. 1 illustrates an exemplary diagram 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 an equal energy of 0.2 Joules. Diagram 100 illustrates a typical high peak-power Holmium laser short pulse versus low peak-power quasi-continuous Thulium long pulse. The diagram 100 includes bubble size on the positive y-axis 102 (with a potential target position at line 112), pulse power on the negative y-axis 104, and time on the x-axis 106. With respect to the high peak-power Holmium laser short pulse, area 118 corresponds to the pulse power, curve 108 corresponds to the bubble created, and line 114 corresponds to the effective distance the laser pulse travels through liquid. With respect to the low peak-power quasi-continuous Thulium long pulse, area 120 corresponds to the pulse power, curve 110 corresponds to the bubble created, and line 116 corresponds to the effective distance the laser pulse travels through liquid.

In both cases, after a short delay, on the order of a few tens of microseconds (μs), following the laser pulse initiation, a bubble is created and starts to expand. In both cases, the life cycle of the bubble, once created, appears to have its own internal dynamics which are not solely related to the laser pulse, and includes the internal vapor pressure generated in the bubble enucleation site, which in turn can depend on absorption, instantaneous peak power, laser beam quality, and/or the presence and amount of air pockets inside the liquid.

It takes time for the bubble to expand. In the case of the Holmium pulse, the bubble reaches its maximum size well after the highest power peak of the laser and in the case of the Thulium laser, the bubble reaches its maximum size during the laser pulse. Also shown in FIG. 1 is that for an exemplary target distance 112 (positioned at a distance of about 3 mm), the effective distance the Thulium laser pulse can travel through liquid 114 is much longer than the effective distance the Holmium laser pulse can travel through liquid 116. Several embodiments described herein take advantage of the independent dynamics of the bubbles in order to optimize the energy distribution using a long pulse.

FIGS. 2A and 2B illustrate exemplary diagrams 200A, 200B of Holmium laser short pulses in different mediums according to one or more embodiments described herein. FIG. 2A corresponds to an air medium and includes diagram 200A of pulse power over time 202 as measured in the air medium from a distance of 3 mm. FIG. 2B corresponds to a liquid medium and includes diagram 200B of pulse power over time 206 as measured in the liquid medium from a distance of 3 mm. Additionally, FIG. 2B includes a time series of images of bubble dynamics 204 corresponding to, and shown in synchrony with, the diagram 200B. In each case a sensor placed within an air or water pathway can be utilized to sense and record pulse power over time.

In the illustrated embodiment, the times series of images of bubble dynamics 204 were taken using a high-speed camera. As shown in the times series of images of bubble dynamics 204, a single index bubble was initiated after a short delay following the beginning of the laser pulse. Also shown in FIG. 2B is that the bigger the bubble, the higher amount of laser power reaches the target, which was a sensor in this exemplary lab setting. 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 starts to collapse, less laser power can reach the target. Also shown in FIG. 2B is that the bubble life cycle is longer than the laser pulse duration.

FIGS. 3A and 3B illustrates exemplary diagrams 300A, 300B of Thulium laser long pulses in different mediums according to one or more embodiments described herein. FIG. 3A corresponds to an air medium and includes diagram 300A of pulse power over time 302 as measured in the air medium from a distance of 2 mm. FIG. 3B corresponds to a liquid medium and includes diagram 300B of pulse power over time 306 as measured in the liquid medium from a distance of 2 mm. Additionally, FIG. 3B includes a time series of images of bubble dynamics 304 corresponding to, and shown in synchrony with, the diagram 300B. In FIGS. 3A and 3B, the pulse powers over time 302, 306 may correspond to an exemplary long pulse of Thulium laser of 0.2 Joule. In each case a sensor placed within an air or water pathway is utilized to sense and record pulse power over time.

FIGS. 3A and 3B show the very different behavior of a long laser pulse in contrast to the short laser pulse of FIGS. 2A and 2B. Surprisingly, as shown in diagram 300B, the target in this case experiences two separate effective laser pulses 308a and 308b, although only a single long laser pulse was generated. The dynamics of the cascade of bubbles can provide the explanation. It is only after the gaseous pathway gets close enough to the target that some energy reaches the target (in the case of Tm, most energy is absorbed in water within 0.1 mm). Further, it takes time for the gaseous pathway to come close enough to the target, and during this time, no laser power reaches the target. Instead, the laser power is mainly absorbed by the liquid in the way to the target. As previously mentioned, energy absorbed by the liquid is not available to treat the target and may turn into unwanted heating of surrounding tissues.

Due to the lower peak power, in comparison to FIGS. 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. Moreover, in the case of the Thulium laser, which is more absorbed by water than Holmium, the rising profile of the laser (as well as the falling time) as experienced by the target is much steeper than it is in the Holmium case, as can be appreciated by a comparison of the diagrams 200B and 300B. Many embodiments described herein may utilize a predetermined pulse energy and a distance to the target to control and optimize the power modulation along the pulse so that more laser power is available during an effective pulse experienced by a target, and less laser power is lost between effective pulses. In many such embodiments, a user may select the pulse energy.

Referring now to the time series of images of bubble dynamics 304 of FIG. 3B, several of the images (or frames) of the time series are numbered, 1-23 from left to right. More specifically, frame #1 shows the tip of the fiber before the initiation of the laser pulse. Once the laser pulse starts, an index bubble, shown in frame 2, starts to grow relatively spherically at the tip of the fiber. As this index bubble continues to grow, it can be seen in frame 3 and 4 that at its front edge, a second bubble starts to grow in a forward direction. Moreover, since this second bubble is an extension of the index bubble, the high pressure inside the index bubble shapes the second bubble to a more cylindrical shape. In addition, as pressure is drained from the index bubble into the second bubble, the index bubble expansion decreases. The result of these two processes is that most of the inside pressure in these two bubbles expands mainly forwardly toward the target as can be seen in frames 5-7.

At this stage, according to the example, the gaseous pathway has reached close enough to the target so that the target experiences the laser power. It is another aspect of the disclosure to generate an index bubble, to generate a second bubble at the front edge of the index bubble and to let the index bubble to inflate and shape the second bubble spontaneously while modulating down the laser pulse power during that time to a lower level than the level which is required to initiate the index bubble. Furthermore, the index bubble at the tip of the fiber tends to collapse on tip of the fiber itself and may degrade it. As a result, the laser beam quality may be reduced as well as the treatment efficiency. The higher the laser power during the initiation of the index bubble, 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 an embodiment of the present disclosure a minimum laser power needed to initiate an index bubble is used, followed by a decreased laser power during the expansion of the index bubble while the laser power is increased again only after the index bubble starts to collapse to further build additional bubbles and a gaseous pathway to the target. Reducing the cavitation effect on the tip of the fiber may delay its degradation.

Referring now to frame 9, it can be seen that the index bubble starts to collapse, and the second bubble breaks off and away from the collapsed index bubble. As seen in next frame 10, fluid fills up the gap between the separated bubbles, and also collapsing second bubble, and the collapsing index bubble. As a result, the target starts to experience a decreased power of laser until no energy reaches the target around frame 11. Also, in frame 10 and more clearly in frame 11, it can be seen that another index bubble is initiated and starts to expand at the tip of the fiber. At this stage, a similar process which was described above regarding fames 1-5 takes place where the gaseous pathway has to be rebuilt, and it is only until the pathway reaches close enough to the target before it starts to experience again an exposure to laser power in around frame 16.

Accordingly, many embodiments described herein may modulate down the laser power once an index bubble has been initiated and during the buildup of the gaseous pathway to the target. Many such embodiments thereby optimize the energy distribution along long pulses to make the bubble path effect more efficient in light of the independent life cycles of the bubbles.

FIGS. 4A-4B and FIG. 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 with pulse power over time 402; FIG. 4B illustrates an exemplary diagram 400B of a Thulium laser long pulse in a liquid medium with pulse power over time 404; and FIG. 5 illustrates an exemplary time series of images of bubble dynamics 500 corresponding to diagram 400B.

Referring to FIG. 4A, the pulse power over time 402 of a long Thulium laser pulse, in an air medium, of about 1 ms in duration and which generates 0.5 Joule as measured from a distance of 2.5 mm is shown in diagram 400A. The corresponding measurement in a liquid medium is shown in FIG. 4B. The pulse of FIGS. 4A and 4B are longer than the pulse shown in FIGS. 3A and 3B. As such, the target 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 in relation to FIG. 3B. As previously mentioned, and shown in FIG. 4A, the laser is quasi-continuously on for about 1 ms. However, effectively, a target in this example, experiences four separated laser sub-pulses 406a, 406b, 406c, 406d. These four separated effective laser pulses 406a, 406b, 406c, 406d are the result of the creation and destruction of the gaseous pathways during the time that the laser is on. Several embodiments described herein may modulate the power of the laser down during the time that the gaseous pathways are built, thereby allowing the spontaneous expansion of the bubbles, and saving laser energy until the gaseous pathway is close enough to the targe tissue. Further, when a gaseous pathway is close enough to a target, embodiments may modulate the laser power up and the utilize the gaseous pathway to bring higher amounts of laser power to the target.

Providing further laser energy during bubble expansion may waste energy because the bubble will not grow further in size during the initial pulse energy applied, since that would mean “pushing against air” within the bubble. In other words, there may be no further absorption within the bubble after it starts expanding. To increase the size of the bubble until the target is reached, laser energy may be expended only while there is liquid in the path from the laser fiber tip to the target so that the resulting absorption is translated into pressure which in re-expands the bubble. Then, when the gaseous pathway starts to break down and develop liquid bridges between separated gaseous pockets, to modulate the laser power down again until the next opportunity to deliver higher laser power to the target through another effective gaseous pathway. FIG. 5 shows the images of the bubbles cascade dynamics discussed above in relation to the FIG. 4B.

A Thulium Fiber Laser (TFL) is typically pumped by a diode laser to create long pulses. Further, a TFL produces a long pulse regime. Accordingly, one or more embodiments described herein may leverage the fact that the time constants associated with bubble formation, initiation, expansion, and collapse are shorter than the laser pulse lengths to modify the pulse power during long laser pulses. In contrast, short pulse lasers are usually pumped by flash lamps, which themselves operate in very short pulse regimes. Short pulse lasers operate in a domain in which the bubble life cycle is longer than the laser pulse length. However, embodiments described herein provide a variety of lasers arranged to emit light having a high absorption coefficient in the relevant liquid and which may generate pulses that are longer than the life cycle of the bubble, and further which may be modulated up and down. For example, one or more of Yttrium Aluminum Garnet (YAG), Erbium, Holmium, and other IR diode or solid state lasers may be modulated up and down according to the present disclosure without departing from the scope.

Various embodiments described herein may utilize a distance between the tip of the optical fiber and the target to determine a mode of operation. For example, there could be two (or more) different scenarios or settings, which might be selected (often automatically by the laser system) based on the distance from the tip of the optical fiber and the target. In a first example scenario, the index bubble expands to a large enough distance and gets close enough to the target for delivery of laser energy. In a second example scenario, the expansion of the index bubble alone is not enough to get 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 the first scenario, and in accordance with the present disclosure (e.g., see various V-shape techniques described below), once the index bubble is created, the power of the laser is modulated down until the index bubble gets close enough to the target. Once the index bubble gets close enough to the target, the power of the laser is modulated up to treat the target. In the second scenario, and in accordance with the present disclosure (e.g., see various resonant modulation techniques described below), once the index bubble is generated the laser power is modulated down and it is modulated up again to treat the target once the second or third bubble reaches the target and when the gaseous pathway starts to break the laser power is modulated back down.

As discussed above, different wavelength and types of laser emissions have different absorption coefficients in a liquid working environment. Therefore, to be “close enough” to a target is a function of the laser and may represent different distances for different lasers. As discussed above in relation to FIGS. 3B and 4B, the slope of the rising profile of an effective laser pulse a target experiences, is also a reflection of this distance. For example, a Thulium laser is absorbed more strongly in the liquid than a Holmium laser. Accordingly, only when the gaseous pathway reaches a distance to the target in a magnitude close to that a Thulium laser photons can travel in the liquid, the target may start to experience some laser power impact. However, since Holmium laser photons may travel in the liquid environment a longer distance than Thulium, the slope of the rising effective laser pulse is less steep. It follows that a close enough distance to a target for a Thulium laser is a shorter distance than it is for a Holmium laser. Since this disclosure may be realized and practiced by different lasers, it will be appreciated that the notion of being close enough is a function of the laser used and the distance its photons can travel in the liquid environment.

Bubble dynamics generally have two phases, expansion followed by collapse. Further, this dynamic has its own time constants. During this bubble expansion, in which the bubble expands, further delivery of laser pulse power (power=rate of energy) appears not to effectively act on the bubble itself, as there is nothing inside the bubble to push against (i.e. there is no or very few absorption media inside the bubble).

Thinking of the harmonics of the operation of a playground-type swing as an analogy, in order to effectively increase the swing's amplitude, the “pushing” frequency should be matched to the swing's natural frequency. In other words, a pulse will be most effective at increasing bubble size if it is “resonant” with the bubble natural frequency (f˜1/200[us] ˜5000 [Hz]). Accordingly, various embodiments described herein may modulate laser pulses based on the natural frequency of a bubble.

In various embodiments, laser pulses may be modulated based on the natural frequency of a bubble as follows. A quasi-continuous wave (QCW) laser that is suitable to also being powered up and down during a long quasi-continuous pulse may be used, such as a TFL. In many embodiments, powering up and down during quasi-continuous pulses may be accomplished by generating fluctuating power. Further the fluctuating power may be generated by driving the pumping laser sources at variable currents while integrating over time to deliver a requested pulse energy (PE). In various embodiments, the overall integral of the modulated power over time equals the requested PE as defined by the user. According to some embodiments, power may be at its highest at the start of the pulse, for example, at the maximum power deliverable by the system.

Once an index bubble is initiated, the power may preferably then be reduced until the bubble is at its max size, thus providing a “reserve” of laser energy that may be better utilized to impact the target once the gaseous pathway gets close enough to the target. At the time the bubble starts to collapse, power may preferably be fluctuated back to its maximum level. This should be repeated in cycles, with a period approximately or substantially equal to the bubble lifetime.

Since in some cases the target may move (in the case of a kidney stone for example) or, even if the target is more or less stationary with respect 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 practical access to the target by the laser fiber tip, or destruction of the target during a procedure. Accordingly, the power fluctuation technique may be varied based on the distance between the laser fiber tip and the target. For example, when the distance to a target is changed (e.g., due to a movement of the target and/or the optical fiber, due to patient anatomy or target changes, or the like) such a distance change may be measured, monitored, or estimated so that the power of the laser may be adjusted accordingly on the fly. Accordingly, when the distance increases/decreases, the system may recalculate the length of the pulse required to create enough effective pulses and/or to expose the target to enough laser energy in order to meet the clinical effect required. For example, with distant targets, the number of cycles may be increased in order to provide a clear, stable, liquid free path from the laser fiber tip to the target.

FIG. 6 illustrates an exemplary diagram 600 of laser pulse power modulation 604 in relation to bubble size 602 according to one or more embodiments described herein. In various embodiments, diagram 600 includes an exemplary pulse power modulation scheme. A pulse modulation scheme may include one or more settings, modes, parameters, characteristics, features, and the like 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 shown by a sinusoidal-type pattern shown in the slanted hatched area. In this case, 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 over long pulses is modulated in an opposite direction to the bubble dynamics described above so that when the bubble expands the laser is modulated down and when the bubble collapses the laser is modulated up. Embodiments are not limited in this context.

FIG. 7 illustrates an exemplary diagram 700 of modulated and unmodulated laser pulses in conjunction with associated bubble dynamics according to 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 according to the present disclosure and its associated bubble dynamics 702b. The diagram 700 includes pulse power on a first y-axis 706, bubble size on a second y-axis 708, and time on the x-axis 710. In various embodiments, FIG. 7 may correspond to bubble path resonant modulation techniques. For instance, the laser pulse may be fit to bubble dynamics to cause bubble size resonation, leading to increased energy delivery to a target.

The flat, unmodulated, long pulse 704a shown in FIG. 7 may cause a cascade of bubbles which expand and collapse in a sinusoidal pattern (corresponding to bubble dynamics 704b). Moreover, the bubbles from the unmodulated pulse 704a grow to about the same size and collapse to about zero size repeatedly in an uncontrolled way. In other words, since there is no mechanism to control or synch the timing and/or location of the bubble collapse and the laser power pulses there is only random constructive and destructive interactions. As will be appreciated, the amount of energy invested in the process is equal to the area below the pulse power line 704a (the integral of the power over time). However, when the laser power is modulated in an opposite direction to the bubble dynamics (see 702a, 702b), energy is saved during the expansion of the bubble. Further, the higher energy modulation during bubble collapsing, reduces the pace of collapse, and accelerates the formation of the next bubble. The accelerated creation of the second bubble takes place before the previous bubble collapses to a zero size and vanishes. Therefore, the second bubble starts from the “shoulders” of the first bubble and reaches further distance. Accordingly, 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.

FIG. 8 illustrates an exemplary diagram 800 according to one or more embodiments described herein. Diagram 800 shows an exemplary pulse modulation scheme 810 in conjunction with its associated bubble dynamics 812. The 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 the x-axis 806. In various embodiments, FIG. 8 may correspond to bubble path resonant modulation techniques. For instance, a target distance may be utilized to create a correspondingly sized bubble prior to delivering a pulse burst.

The pulse modulation 810 illustrated in diagram 800 works in a counter direction to the bubble size dynamics 812. In this example, the target is located at a distance of 2 mm from the tip of an optical fiber (see line 808). As shown in the illustrated embodiment, since the power of the laser is modulated up when the bubble size starts to shrink, the bubbles do not collapse to a zero size, or the collapse is at least reduced. Every successive bubble is built on the “shoulders” of its previous bubble, creating a step wise pattern until the gaseous pathway reaches close to the target. As used herein, close to the target can be taken to 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 approximately 0.1 mm when using a Thulium laser and approximately 0.5 when using a Holmium laser.

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

While the above discussion has generally been directed to treating targets at a distance, an alternative pulse modulation profile to improve energy delivery at relatively nearby target distances may be the termed as a “V-shape”. In various embodiments, nearby targets may be defined as those located at distances that can be bridged by the index bubble alone, and distant targets may be defined as those located at distances which are 2 to 4 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, an index bubble for a Holmium laser may be approximately between 1 mm and 2 mm and an index bubble for a Thulium laser may be approximately between 0.5 mm and 1 mm.

In various embodiments, a V-shape pulse modulation may have one or more of the following profile characteristics: (a) start with maximal power to create initial bubble; (b) drop power while bubble expands; and (c) increase power back to maximum while bubble is at its maximal size or when the bubble is expected to reach the target (whichever is shortest). In various embodiments, this V-shape pulse modulation would result in more efficient energy delivery than a Holmium laser short mode (which resembles a downward slope triangle) because it delivers more of the pulse energy during the expanded phase of the bubble, thus encountering less water absorption.

In various embodiments, the laser power and a distance between the fiber tip and the target may be provided as input for optimizing the pulse modulation. The index bubble maximal size may be a function of the instantaneous pulse power during the first few 10 s of microseconds as well as of the wavelength absorption in water, beam quality, and delivery fiber geometry. Accordingly, for a given laser and delivery fiber, the bubble dynamics for various peak powers can be measured, such as in a bench setup. A lookup table may be created to tabulate the relationship between {peak power and/or initial power, fiber size, and wavelength} vs. {max bubble size, time from lasing initiation to start of bubble formation (t0), time to reach bubble maximum size (tmax), and time to collapse (tc)}. From this information, the initial modulation frequency may be obtained as roughly 1/(tc−tmax−t0). Further insight into modulation frequency dynamic adjustment may be derived by experimental observation in the bench setup of modulation frequency change effects 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 may be strongly dependent on pulse (peak) power and the absorption coefficient of the liquid at the laser wavelength. Accordingly the pulse (peak) power and the absorption coefficient of the liquid at the laser wavelength may be utilized to estimate the time an index bubble reaches its maximal size and starts to collapse.

FIG. 9 illustrates an exemplary laser system 900 according to one or more embodiments described herein. In various embodiments, 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 of the pulse modulation schemes. In many embodiments, laser system 900 may be, or include, a fiber laser. In the illustrated embodiment, laser system 900 includes a laser source 921 capable of producing a laser beam 923, a controller 922, laser fiber 924 (or optical fiber 924), connector 925, a partially transparent mirror 926A, a partially transferred 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 a target (not shown). In various embodiments, a known apparatus (e.g., an endoscope) may be utilized to introduce the laser fiber 924 into a body cavity for positioning the tip of the laser fiber 924 proximate to a target, such as a kidney or other urinary tract stone or a prostate that is 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 this disclosure. For example, distance measurement module 929 and/or photo detector 927 may be excluded from laser system 900 without departing from the scope of this disclosure. Embodiments are not limited in this context.

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

It will be appreciated that one or more embodiments described hereby may be implemented without one or more of photo detector 927 and distance measurement module 929. In some embodiments, a distance between a fiber tip and a target may be an expected 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, modulation schemes may be selected based on a mode of operation and/or user input.

In various embodiments, the controller 922 may include a processor and 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 emanating from the laser source 21. In some embodiments, the controller 922 may measuring the distance from the tip of the laser fiber to the target. In other embodiments, the distance may be provided as input to the controller 922. For example, distance measurement module 929 may provide the distance as input to controller 922. Techniques for determining 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 herein incorporated by reference. Depending on the distance measured, the controller 922 may initiate and regulate the amount of power which is provided to the laser fiber, and in the context of the present disclosure, the varying power configurations (modulation schemes) described herein.

In many embodiments, the laser system 900 may operate in different modes for nearby targets and distant targets. As previously mentioned, for example, V-shape optimization may be utilized to determine pulse modulation schemes for nearby targets and resonant modulation optimization may be utilized to determine pulse modulation schemes for distant targets. 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.

For V-shape optimization on nearby targets, the inputs may include pulse energy and a target at close proximity (“contact”/“close”). As described above, the term “close proximity” can mean that the target is within a distance from the tip of the laser fiber 924 that can be bridged by the index bubble alone. In such a scenario, the initial pulse power may be determined to deliver a bubble of size approximately (or substantially) 1 to 2 times the distance to the target. Max energy delivery may occur while the bubble is equal to and larger than the distance to the target. Accordingly, in some embodiments, bubble size may be utilized to control an amount of time maximal energy is delivered to a target. For example, a bubble size approximately two times the distance to the target may be utilized to deliver maximal energy for a relatively long period of time and a bubble size approximately equal to the distance to the target may be utilized to deliver maximal 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 down until the time the bubble is near maximal size. Then the pulse power may be raised to maximum. In some embodiments, when the initial pulse power is equal to the max power the system may start at max power, reduce power during bubble expansion, and raise to max power again when the bubble is at maximal size. Finally, the pulse may be terminated when the integral (power×time) is equal to the requested pulse energy. As used herein, “max power” may not mean the maximum power with which the laser source can deliver, but instead can mean the power level for the desired therapy or treatment.

For resonant modulation optimization on distant targets, the inputs may include pulse energy and a target at distance (“distance” mode). The initial pulse power may be set at the maximal system power. For example, controller 922 may set the initial pulse power to the max level based on classification of a target as distant based on a distance estimation. The laser may be fired at the maximal power level and then modulated down during bubble expansion. The power may be modulated up to max again when the bubble reaches maximal size. Then the modulation may be cycled at periods in the range of 0.5 to 1.5 times the bubble expansion/collapse dynamics (e.g., ×0.7-×1.3 of the time from start to collapse) to achieve a resonant effect. In various embodiments, the period may be adjusted for each sequential bubble in the bubble train, such as due to changes in the distance to the target. When the train of bubbles is expected to bridge the distance to the target, the pulse power may be raised to max to take advantage of minimal liquid being located along the pathway of the laser between the fiber tip and the target. Finally, the pulse may be terminated when the integral (power×time) is equal to the requested pulse energy.

In one embodiment, a method of operating the laser system 900 may include one or more of the following exemplary operational steps of the laser system 900, which is configured to implement one or more pulse modulation schemes described herein. Step one, a user selects the type of fiber in use. According to one embodiment, a user may select manually a type of fiber to be used in the treatment. According to another embodiment, an automatic fiber recognition system may be implemented. Step two, a 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 a modulated pulse. In other words, and as will be discussed below, the system may be programmed and configured, using a suitable programmable controller, to set up a pulse modulation scheme in a way transparent to the user. For example, the user in this embodiment may not be required to set up the values for various parameters.

Step three, a user may select the modulation scheme repetition rate (e.g., the time between modulated pulses). Step four, a user may select a desired (average) working distance between the tip of the fiber and the target tissue. According to another embodiment, the working distance may be detected by the system automatically, for example, by using a distance evaluation technology as described in the U.S. patent application Ser. No. 13/811,926, the entirety of which is incorporated herein by reference. Step five, based on previously manually loaded or automatically detected parameters, the system may define automatically, from a lookup table operatively associated with the programmable controller or calculates the working values for one or more of peak power, initial power, fiber size, wavelength, max bubble size, time from lasing initiation to start of bubble formation (t0), time to reach bubble maximum size (tmax), and time to collapse (tc).

Step six, a pulse may be fired according to the modulation scheme. In various embodiments, the system may be configured to measure actual values of each pulse/modulation scheme. In step seven and eight, the system may be configured to compare the measured values to the predefined values on step five. Should the measured parameters deviate from the predefined parameter, the system automatically corrects such deviation in step nine, and a new set of working parameters are sent to the programmable controller which for implementation in the next modulation scheme by repeating at step six. In this way, the system may maintain the actual working values within the predefined range. It should be understood that during step seven, the system may be configured to measure different parameters which may be related to actual laser pulse energy.

For example, according to one embodiment, the system may use photodetector 927 to measure optical energy output of the modulation scheme. According to another embodiment, for example, the system may be configured to measure current or voltage pulses which are sent to the laser pumping energy source. Therefore, 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 which is related to a pulse modulation scheme.

In some embodiments, a method of operating the laser system 900 may be loosely based on FIGS. 3A and 3B of the '781 patent, accounting, of course, for any differences in the laser source, and the sequence of laser firings described herein, as illustrated in the flowchart of FIG. 10.

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 operation steps may include measuring the distance from the laser fiber tip to the target at block 1002. For example, controller unit 922 can determine a distance between the tip of the laser fiber 924 and a target. More specifically, circuitry of controller unit 922 and/or distance measurement module 929 can execute instructions and/or receive signals to determine a distance between the tip of the laser fiber 924 and the target. At decision block 1004, if the distance measured is less than or less than or equal to a distance (D) X, then the method 1000 can proceed to a V-shape mode; if, however, the distance D is greater than or greater than or equal to the distance X, the method can proceed to a modulation mode of operation. In various embodiments, the distance X may be determined experimentally and the results recorded in a lookup table which includes distances as well as other parameters such as the number of pulses and the power applied to the pulses. It should also be mentioned that since the target may be mobile in its environment, such as a kidney stone, the controller may be dynamic in nature and able to adjust parameters for the laser, including changing from a V-shape 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 than or less than X. Embodiments are not limited in this context.

After the mode is selected (e.g., at block 1006 or block 1020), method 1000 include 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 (block 1008, 1022). More specifically, where the V mode is selected at block 1006, controller 924 can select an energy level of the pulses; and where the resonant mode is selected at block 1020, the controller 924 can select an energy level of the pulses and a modulation frequency for the pulses.

Continuing to block 1010 and 1024, method 1000 can include sending control signals to the laser source 921 to cause the laser source to activate to fire the laser beam (block 1010, 1024), whereupon the method 1000 includes operations for the controller 924 to calculate the pulse energy delivered to the target (block 1012, 1026). For example, controller 924 can determine (or receive signals from sensors comprising indications of) pulse energy delivered to the target. In addition, at blocks 1012 or 1026) the controller 924 may estimate one or more of the number of effective pulses to be experienced by a target, the effective energy per every single effective pulse to be delivered to the target, and the accumulated effective energy to be delivered to the target by the number of effective pulses. Moreover, for a selected energy level as may be selected by a user, the controller 924 can select the power modulation and bubble path modulation resonant frequency so that the selected energy is actually delivered to the target in one of more effective pulses.

If the controller selections were sufficient (block 1014, 1028) to achieve the desired effect (stone breakup, dusting, etc.), the operator observing the extent of treatment may stop the system (block 1016, 1032) and vice versa if the effects are not achieved (block 1018, 1030). Accordingly, method 1000 can include receiving an indication from an operator (e.g., physician, or the like) that the treatment is sufficient or not. Based on the received indication, method 1000 can either end (block 1016, 1032) or can repeat (block 1018, 1030) or said differently, return to block 1002. In this manner, the operator may provide an indication to the system (e.g., system 900) and the system 900 can receive the indication and further or additional treatments carrier out to reach the desired effects. The steps may be adjusted dynamically using a closed feedback circuit connected to the controller. Thus, by way of example, if the distance to the target changes during the procedure, the closed feedback loop may provide that information to the controller which then may cause the controller to change the parameters of treatment.

FIG. 11 illustrates a flowchart showing a method 1100 of implementing a modulation scheme in accordance with some embodiments of the present disclosure. The method 1100 is described with reference to the system 900 and to the various configurations and embodiments described above. It is to be appreciated however, that the method 1100 could be implemented using a system different than that described herein. Embodiments are not limited in this context.

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

At block 1108, the method 1100 includes setting an initial pulse power for the modulation scheme to generate an index bubble in the liquid based on the distance. For example, when the distance is over a threshold distance, the initial pulse power may be set to a maximal system power. In another example, when the distance is under a threshold distance, the initial pulse power may be set to deliver a bubble with a size that is 1 to 2 times the distance to the target. In some such examples, a lookup table may be used to determine the initial pulse power that will deliver the bubble with a size that is 1 to 2 times the distance to the target. At block 1110, the method 1100 includes initiating a pulse according to the modulation scheme via the fiber laser, wherein the modulation scheme reduces power of the pulse after initiation of 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.

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, the computer system 1200, or one or more portions thereof, may comprise controller 922. In some such embodiments, the computer system 1200 may be utilized to control operation of laser system 900 with respect to a target. Embodiments are not limited in this context.

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, a person using a device such as those included in this disclosure, or such a device itself. The processor 1202 may include specialized processing units such as integrated system (bus) controllers, memory management control units, floating point units, graphics processing units, digital signal processing units, etc. The processor 1202 may be disposed in communication with input devices 1211 and output devices 1212 via I/O interface 1201. The I/O 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) antennas, 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, or the like), etc.

Using the I/O interface 1201, computer system 1200 may communicate with input devices 1211 and output devices 1212. In some embodiments, the processor 1202 may be disposed in communication with a communication network 1209 via a network interface 1203. In various embodiments, the communication network 1209 may be utilized to communicate with a remote device 1220, such as for accesses look-up tables or utilizing external resources. The network interface 1203 may communicate with the communication network 1209. The 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 the computer system 1200 may be integrated into the 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., distance measurement module 929, laser source 921, photodetector 927, etcetera).

The communication network 1209 can be implemented as one of the different types of networks, such as intranet or Local Area Network (LAN), Closed Area Network (CAN) and such. The communication network 1209 may either be a dedicated network or a shared network, which represents an association of the different types of networks that use a variety of protocols, for example, Hypertext Transfer Protocol (HTTP), CAN Protocol, Transmission Control Protocol/Internet Protocol (TCP/IP), Wireless Application Protocol (WAP), etc., to communicate with each other. Further, the communication network 1209 may include a variety of network devices, including routers, bridges, servers, computing devices, storage devices, etc. In some embodiments, the processor 1202 may be disposed in communication with a memory 1205 (e.g., RAM, ROM, etc. not shown in FIG. 12) via a storage interface 1204. The storage interface 1204 may connect to memory 1205 including, without limitation, memory drives, removable disc drives, etc., employing connection protocols such as Serial Advanced Technology Attachment (SATA), Integrated Drive Electronics (IDE), IEEE-1394, Universal Serial Bus (USB), fiber channel, Small Computer Systems Interface (SCSI), etc. The memory drives may further include a drum, magnetic disc drive, magneto-optical drive, optical drive, Redundant Array of Independent Discs (RAID), solid-state memory devices, solid-state drives, etc.

The 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, etcetera. In various embodiments, instructions 1215 may include instructions that when executed by the processor 1202 cause the processor 1202 to perform one or more techniques, steps, procedures, and/or methods described herein, such to estimate a distance or perform a calibration. For example, instructions to perform 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, the computer system 1200 may store user/application data, such as the data, variables, records, etc. as described in this disclosure. Such databases may be implemented as fault-tolerant, relational, scalable, secure databases such as Oracle or Sybase.

The operating system 1207 may facilitate resource management and operation of the 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, or the like. The User interface 1206 may facilitate display, execution, interaction, manipulation, or operation of program components through textual or graphical facilities. For example, user interfaces may provide computer interaction interface elements on a display system operatively connected to the computer system 1200, such as cursors, icons, checkboxes, menus, scrollers, windows, widgets, etc. Graphical User Interfaces (GUIs) may be employed, including, without limitation, Apple® Macintosh® operating systems' Aqua®, IBM® OS/2®, Microsoft® Windows® (e.g., Aero, Metro, etc.), web interface libraries (e.g., ActiveX®, Java®, JavaScript®, AJAX, HTML, Adobe® Flash®, etc.), or the like.

In some embodiments, the computer system 1200 may implement the web browser 1208 stored program components. The web browser 1208 may be a hypertext viewing application, such as MICROSOFT® INTERNET EXPLORER®, GOOGLE™ CHROME™, MOZILLA® FIREFOX®, APPLE® SAFARI®, etc. Secure web browsing may be provided using Secure Hypertext Transport Protocol (HTTPS), Secure Sockets Layer (SSL), Transport Layer Security (TLS), etc. Web browsers 1208 may utilize facilities such as AJAX, DHTML, ADOBE® FLASH®, JAVASCRIPT®, JAVA®, Application Programming Interfaces (APIs), etc. In some embodiments, the computer system 1200 may implement a mail server stored program component. The mail server may be an Internet mail server such as Microsoft Exchange, or the like. The mail server may utilize facilities 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), or the like. In some embodiments, the computer system 1200 may implement a mail client stored program component. The mail client may be a mail viewing application, such as APPLE® MAIL, MICROSOFT® ENTOURAGE®, MICROSOFT® OUTLOOK®, MOZILLA® THUNDERBIRD®, etc.

Furthermore, 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 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 processor(s) 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 transient 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 Disc (DVDs), flash drives, disks, and any other known physical storage media.

It will be understood by those within the art that, in general, terms used herein, and 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 “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended. For example, as an aid to understanding, the detail 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 same holds true for the use of definite articles used to introduce claim recitations. In addition, 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 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 this disclosure have been described in terms of preferred embodiments, it may be apparent to those of skill in the art that variations can be applied to the devices and/or methods and in the steps or in the sequence of steps of the method described herein 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

1. A system, comprising:

a fiber laser; and

a controller comprising a processor and memory, the memory comprising instructions that when executed by the processor cause the processor to: determine a pulse energy for the 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 for 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 power of the pulse after initiation of the pulse at the initial pulse power.

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

3. The system of claim 2, wherein the instructions, when executed by the processor, further cause the processor to estimate the time the index bubble takes to reach maximal 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 claim 1, wherein 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; and

determine an updated modulation scheme based on the updated distance.

5. The system of claim 1, wherein the modulation scheme is configured to modulate pulse power down during expansion of the index bubble and modulate pulse power up during collapse of the index bubble.

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 for the index bubble to reach maximum size, and a time from lasing initiation to start of bubble formation.

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

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

10. The system of claim 9, wherein the modulation scheme is configured obtain a resonant effect by cycling at periods between 0.7 and 1.3 times a time from start to collapse of the index bubble.

11. 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:

determine a pulse energy for 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 for 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 power of the pulse after initiation of the pulse at the initial pulse power.

12. The at least one non-transitory computer-readable medium of claim 11, wherein the modulation scheme increases power of the pulse to a maximal system power level at a time estimated for the index bubble to reach maximal size.

13. The at least one non-transitory computer-readable medium of claim 12, wherein the set of instructions, in response to execution by the processor circuit, further cause the processor circuit to estimate the time the index bubble takes to reach maximal size based on the initial pulse power and an absorption coefficient of the liquid at a wavelength of the fiber laser.

14. The at least one non-transitory computer-readable medium of claim 11, wherein 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.

15. The at least one non-transitory computer-readable medium of claim 11, wherein the set of instructions, in response to execution by the processor circuit, further cause the processor circuit to set the initial pulse power for the modulation scheme to generate the index bubble in the liquid based on the distance and the pulse energy.

16. The at least one non-transitory computer-readable medium of claim 11, wherein 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.

17. A method, comprising:

determining a pulse energy for 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 for 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 power of the pulse after initiation of the pulse at the initial pulse power.

18. The method of claim 17, comprising modulating pulse power down during expansion of the index bubble and modulating pulse power up during collapse of the index bubble.

19. The method of claim 17, comprising classifying the target as distant target based on the distance and set the initial pulse power to a maximal system power level based on classification of the target as distant.

20. The method of claim 19, comprising cycling at periods between 0.7 and 1.3 times a time from start to collapse of the index bubble.