Laser Tissue Ablation System

Abstract

To provide systems and methods for determining and controlling a distance between an endoscope tip and a target.SOLUTION: In a laser tissue ablation system, a distal end of an optical fiber can extend from an endoscope. The optical fiber can receive therapeutic laser light pulses at first times, receive measurement light pulses at second times, direct the therapeutic laser light pulses and the measurement light pulses toward a target, collect, as collected light pulses, at least some of the measurement light pulses that are reflected from the target, and direct, as return light pulses, at least some of the collected light pulses away from the distal end of the optical fiber. An optical detector can sense at least some of the return light pulses. Processor circuitry can perform a time-of-flight analysis of the sensed return light pulses to determine a spacing between the distal end of the optical fiber and the target, and can generate a spacing data signal representing the determined spacing.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Application No. 63 / 377,889, filed September 30, 2022, which is incorporated herein by reference in its entirety.

[0002] This document relates generally to endoscopy systems, and more particularly to systems and methods for determining and controlling the distance between an endoscope tip and a target. [Background technology]

[0003] An operator, such as a physician, practitioner, or user, can use an endoscope to provide visual access to a location inside a patient. The operator can insert the endoscope into the patient's body. The endoscope can deliver light to a target being inspected, such as a target anatomical structure or object. The endoscope can collect light reflected from the object. The reflected light can convey information about the target being inspected.

[0004] The endoscope may include a working channel. In some examples, an operator may perform suction through the working channel. In some examples, an operator may pass instruments such as brushes, biopsy needles, or forceps through the working channel. In some examples, an operator may perform minimally invasive surgery through the working channel, such as to remove unwanted tissue or foreign matter from a patient's body.

[0005] An endoscope can use a laser or plasma system to perform laser treatments such as ablation, coagulation, vaporization, fragmentation, and lithotripsy. In laser treatments, an operator can use an endoscope to deliver surgical laser energy to various target treatment areas, such as soft or hard tissue. In lithotripsy, an operator can use an endoscope to deliver surgical laser energy to break up stone structures within a patient's kidney, gallbladder, ureter, or other stone-forming areas, or to ablate large stones into smaller fragments. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] U.S. Patent Application Publication No. 2021 / 0161364 Summary of the Invention [Means for solving the problem]

[0007] In one example, a laser tissue ablation system can include an endoscope; an optical fiber including a distal end extending from the endoscope, the optical fiber configured to receive a therapeutic laser light pulse at a first time and receive a measurement light pulse at a second time different from the first time; direct the therapeutic laser light pulse and the measurement light pulse along the optical fiber so that they emerge from the distal end of the optical fiber toward a target; collect at least a portion of the measurement light pulse reflected from the target as collected light pulses; and direct at least a portion of the collected light pulses along the optical fiber away from the distal end of the optical fiber as return light pulses; a photodetector configured to sense at least a portion of the return light pulses; and a processor circuit configured to perform time-of-flight analysis of the sensed return light pulses to determine a spacing between the distal end of the optical fiber and the target; and generate a spacing data signal representative of the determined spacing.

[0008] In one example, a method for operating laser tissue ablation including an endoscope and an optical fiber including a distal end extending from the endoscope includes receiving a therapeutic laser light pulse at a first time using the optical fiber; receiving a measurement light pulse at a second time different from the first time using the optical fiber; directing the therapeutic laser light pulse and the measurement light pulse along the optical fiber so that they emerge from the distal end of the optical fiber toward a target; collecting, using the optical fiber, at least a portion of the measurement light pulse reflected from the target as collected light pulses; directing at least a portion of the collected light pulses along the optical fiber away from the distal end of the optical fiber as return light pulses; sensing, using a photodetector, at least a portion of the return light pulses; performing time-of-flight analysis of the sensed return light pulses to determine a spacing between the distal end of the optical fiber and the target; and generating a spacing data signal representative of the determined spacing.

[0009] In one example, a laser tissue ablation system includes a therapeutic laser light source configured to generate therapeutic laser light pulses at a first time; a measurement light source configured to generate measurement light pulses at a second time different from the first time; an endoscope spaced from the therapeutic laser light source and the measurement light source; and an optical fiber including a distal end extending from the endoscope, the optical fiber including: directing the therapeutic laser light pulses and the measurement light pulses along the optical fiber to emerge from the distal end of the optical fiber toward a target; collecting at least a portion of the measurement light pulses reflected from the target as collected light pulses; directing at least a portion of the collected light pulses along the optical fiber away from the distal end of the optical fiber as return light pulses; collecting at least a portion of the therapeutic light pulses reflected from the target as collected therapeutic light pulses; and directing at least a portion of the collected therapeutic light pulses as return therapeutic light pulses through the optical fiber. and directing the returned therapeutic light pulses along the fiber and away from the distal end of the optical fiber; a photodetector configured to sense at least a portion of the returned therapeutic light pulses; a spectrometer configured to analyze the returned therapeutic light pulses; a processor circuit configured to perform a time-of-flight analysis of the sensed returned light pulses to determine a distance between the distal end of the optical fiber and the target, generate a distance data signal representative of the determined distance, and electronically communicate the distance data signal to the spectrometer; an illumination light source disposed at the distal end of the endoscope and configured to illuminate the target with visible illumination light; a camera disposed at the distal end of the endoscope and configured to generate a video image of the illuminated target; and a display coupled to the processor circuit and configured to display the video image of the illuminated target and a visual representation of the determined distance represented by the distance data signal.

[0010] Various embodiments are illustrated by way of example in the accompanying drawing figures. Such embodiments are illustrative and are not intended to be exhaustive or exclusive embodiments of the present subject matter. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic side view of an example laser tissue ablation system. [Figure 2] 1 is a flowchart of an example method for operating a laser tissue ablation system. [Figure 3] FIG. 1 is a schematic diagram of an exemplary computer-based clinical decision support system configured to provide distance values. DETAILED DESCRIPTION OF THE INVENTION

[0012] In a laser therapy treatment, a practitioner may position the distal end of an endoscope near a target, such as a kidney stone. The endoscope may include an optical fiber that can deliver therapeutic laser light to the target, such as via the distal end of the optical fiber. During treatment, it may be beneficial to dynamically monitor or dynamically control the separation between the distal end of the optical fiber and the target. For example, if the distal end of the optical fiber is positioned too close to the target, a condition known as flashing may occur, which may degrade the distal end of the optical fiber. Similarly, if the distal end of the optical fiber is positioned too far from the target, a significant portion of the therapeutic laser light may be absorbed before reaching the target, which may reduce the efficiency of the laser therapy treatment or prolong the procedure.

[0013] The laser tissue ablation system described in detail below can use time-of-flight techniques on light returning through the optical fiber to dynamically monitor the separation between the distal end of the optical fiber and the target (referred to in the following paragraph as "real-time separation").

[0014] Specifically, during a laser therapy treatment, the surgical system can use time-of-flight techniques on light returning through the optical fiber to dynamically determine real-time separation and can provide user feedback and / or take action in response to the real-time separation value. For example, the surgical system can provide user feedback to the practitioner indicative of the real-time separation, such as displaying a numerical value on a display, displaying a graphical representation of the real-time separation on a display, displaying a visual indicator that indicates when the real-time separation is within one of several specified ranges (too small, acceptable, too large, etc.), playing an audio alert, etc. As another example, the surgical system can take action in response to the real-time separation, such as retracting the optical fiber distally if the real-time separation is too low, automatically positioning the distal end of the optical fiber to have a specified value of real-time separation, etc.

[0015] Because time-of-flight measurements use light returning through an optical fiber, the measurement technique is sometimes referred to as coaxial.

[0016] FIG. 1 shows a schematic side view of an example of a laser tissue ablation system 100. The laser tissue ablation system 100 may include an endoscope 102. The endoscope 102 may be held by an operator, who may position the endoscope 102 to view and ablate one or more targets, such as kidney stones, at one or more internal locations of a patient, as needed. In some examples, the endoscope 102 may be rigid. In one or more examples, the endoscope 102 may be elongated along an elongation axis. The endoscope 102 may include one or more channels, passages, or openings extending through the endoscope 102 along the elongation axis. For example, the endoscope 102 may include a working channel. In some examples, an operator may perform suction through the working channel. In some examples, an operator may pass an instrument, such as a brush, biopsy needle, or forceps, through the working channel. In some examples, an operator may perform minimally invasive surgery through the working channel, such as to remove unwanted tissue or foreign matter from a patient's body. As another example, the endoscope 102 may include an irrigation channel that can deliver irrigant to the target site to flush out debris from the target, etc. Other channels may also be used.

[0017] The laser tissue ablation system 100 can include an illumination light source 104 disposed at the distal end 106 of the endoscope 102. For example, the illumination light source 104 can include one or more light emitting diodes disposed at the distal end 106 of the endoscope 102. In some examples, the light emitting diodes can be white light emitting diodes. For example, the white light emitting diodes can include blue or violet light emitting diodes combined with a phosphor that can absorb some or all of the blue or violet light and, in response, emit one or more longer wavelengths of light, such as in the yellow portion of the electromagnetic spectrum. Other illumination light sources can also be used. The illumination light source 104 can illuminate the target 108 with visible light illumination having a visible light illumination spectral range. In some examples, the visible light illumination spectral range can include wavelengths in the visible portion of the electromagnetic spectrum.

[0018] The laser tissue ablation system 100 can include a video camera 110 disposed at the distal end 106 of the endoscope 102. In some examples, the video camera 110 can include a lens, a sensor element disposed at the focal plane of the lens, and electronics capable of converting an electrical signal generated by the sensor element into a digital signal. The video camera element can be disposed in a relatively small, sealed package at the distal end 106 of the endoscope 102. The video camera 110 can capture real-time video images of the illuminated target 108.

[0019] The laser tissue ablation system 100 can include a video display 112 capable of displaying a video image of the illuminated target 108. For example, the video display 112 can be mounted on or in an equipment rack separate from the endoscope 102. The video display 112 can provide the practitioner with a real-time image of the target 108 illuminated with white light from the illumination source 104.

[0020] The laser tissue ablation system 100 can include a therapeutic laser source 114 capable of generating laser light, such as pulsed laser light. In some examples, the therapeutic laser source 114 can generate a therapeutic laser light pulse at a first time. The therapeutic laser source 114 can be located remotely from the endoscope 102 so that the endoscope 102 can be positionable by an operator, while the therapeutic laser source 114 can be located within a laser housing that can remain in a fixed position spaced apart from the endoscope 102 during treatment. In some examples, the therapeutic laser source 114 can include a thulium fiber laser capable of generating light having one or more wavelengths between about 1920 nm and about 1960 nm. In some examples, the therapeutic laser source 114 can include a thulium:YAG (yttrium aluminum garnet) laser capable of generating light at a wavelength of 2010 nm. In some examples, the therapeutic laser source 114 can include a holmium:YAG laser capable of generating light at a wavelength of 2120 nm. In some examples, the therapeutic laser source 114 can include an Erbium:YAG laser capable of generating light at a wavelength of 2940 nm. In some examples, the laser light generated by the therapeutic laser source 114 can include a first wavelength, such as between about 1908 nm and about 2940 nm, or between about 1920 nm and 1960 nm, between about 1900 nm and about 1940 nm, greater than about 1900 nm, greater than about 1800 nm, or other wavelengths. For these (and other) therapeutic laser sources, the laser light can have a wavelength in a portion of the electromagnetic spectrum where water (a major component of tissue) has relatively high absorption. During treatment, tissue can absorb the laser light, heat locally to relatively high temperatures, and decompose due to localized thermal strain within the tissue.

[0021] The laser tissue ablation system 100 can include a measurement light source 158 that can generate measurement light pulses at a second time different from the first time. For example, the first and second times can be alternated such that the treatment laser light source 114 generates treatment laser light pulses when the measurement light source 158 is not generating light, and the measurement light source 158 generates measurement light pulses when the treatment laser light source 114 is not generating light. As another example, the treatment laser light source 114 can generate a series of pulses (e.g., 10 pulses), and the measurement light source 158 can generate measurement light pulses, with the sequence of 11 pulses repeated as needed. These are merely example schemes for generating measurement light pulses at a second time different from the first time, and other schemes can also be used.

[0022] The laser tissue ablation system 100 can include an optical fiber 116 that can extend from the endoscope 102. In some examples, the optical fiber 116 can be a multimode optical fiber. In some examples, the optical fiber 116 can have a distal end 118 that extends from the distal end 106 of the endoscope 102.

[0023] The therapeutic laser source 114 and the measurement light source 158 can direct the therapeutic laser light pulses and the measurement light pulses, respectively, at different times into the proximal portion 120 of the optical fiber 116, such as via the therapeutic laser source optical fiber 122 and the free-space optical coupler / splitter 124. The free-space optical coupler / splitter 124 can include a collimating lens 126 with a focal plane located at the distal end 128 of the therapeutic laser source optical fiber 122, which can collimate (or at least partially focus) the light from the therapeutic laser source 114. The collimated light can pass through a return path beam splitter 130 and be focused by a bidirectional focusing lens 132 onto the proximal portion 120 of the optical fiber 116. The free-space optical coupler / splitter 124 can include an input path beam splitter 160 that can receive the measurement light pulse from the measurement light source 158 and direct the measurement light pulse onto a common optical path with the therapeutic laser light pulse from the therapeutic laser light source 114. In some examples, the therapeutic laser light source 114 can direct the therapeutic laser light pulse along a first optical path, the measurement light source 158 can direct the measurement light pulse along a second optical path, the measurement light pulse being spectrally separated from the therapeutic laser light pulse, and the input path beam splitter 160 can be a dichroic beam splitter positioned to combine the first and second optical paths so that they are aligned along a third optical path extending into the optical fiber 116. The bidirectional focusing lens 132 can direct the therapeutic laser light pulse (e.g., at a first time) and the measurement light pulse (e.g., at a second time) onto the proximal portion 120 of the optical fiber 116. Bidirectional focusing lens 132 can collimate the returning light returning through optical fiber 116. Return path beam splitter 130 can direct all or a portion (or spectral portion) of the returning light onto return path focusing lens 134, which can focus the returning light onto end 136 of return path optical fiber 138. Return path optical fiber 138 can direct the returning light to a sensor (described below).The free-space optical coupler / splitter 124 is just one configuration for such a coupler / splitter. Alternatively, a fiber-based optical coupler / splitter can also be used.

[0024] The optical fiber 116 can receive the therapeutic laser light pulse at a first time. The optical fiber 116 can receive the measurement light pulse at a second time different from the first time. The optical fiber 116 can direct the therapeutic laser light pulse and the measurement light pulse along the optical fiber 116 so that they emerge from a distal end 118 of the optical fiber 116 toward the target 108. The optical fiber 116 can collect at least a portion of the measurement light pulse reflected from the target 108 as a collected light pulse. The optical fiber 116 can direct at least a portion of the collected light pulse along the optical fiber 116 away from the distal end 118 of the optical fiber 116 as return light.

[0025] The laser tissue ablation system 100 may include a photodetector 140 capable of sensing at least a portion of the returned light pulses. The photodetector 140 may include a photosensitive sensor element 142 capable of converting an optical signal, such as a returned light pulse, into an internal electrical signal. The photodetector 140, as shown in the configuration of FIG. 1, may also include a sensor circuit 144, which may convert or process the internal electrical signal from the photosensitive sensor element 142 into an analog or digital sensor data signal 146 that can be interpreted by a processor circuit 148 (described below). The photodetector 140 may further include one or more wavelength-sensitive elements, which enable the sensor circuit 144 to provide intensity measurements of the returned light as a function of wavelength.

[0026] For example, the wavelength-sensitive element of the photodetector 140 can include a dichroic beam splitter (e.g., implemented as a thin-film coating on the return path beam splitter 130) that can separate the measurement light from the treatment laser light. The dichroic beam splitter can have a threshold wavelength and can direct light having wavelengths shorter than the threshold wavelength along a first optical path and light having wavelengths longer than the threshold wavelength along a second optical path. The threshold wavelength can have any suitable wavelength value between the wavelength of the measurement light and the wavelength of the treatment laser light. In some examples, the dichroic beam splitter can be implemented as a thin-film coating on the surface of a transparent optical element such as a prism.

[0027] In some configurations, the photodetector 140 may include a dichroic beam splitter (e.g., implemented as a thin-film coating on the return path beam splitter 130) that can receive the returned light, direct the treatment laser light along a first optical path, and direct the measurement light along a second optical path. The photosensitive sensor element 142 of the photodetector 140 may include a sensor element or detector that can detect light from the second optical path. In some examples, the photosensitive sensor element 142 may include a single detector element. In other examples, the photosensitive sensor element 142 may include a multi-pixel detector element. The photodetector 140 may further include a sensor circuit 144 that can generate one or more sensor data signals 146 in response to the light received by the photodetector. A processor circuit 148 (described below) may analyze the one or more sensor data signals 146 to determine whether and / or when a flashing event occurred.

[0028] In some configurations, the sensor circuit 144 of the photodetector 140 (and optionally the wavelength-sensitive element of the photodetector 140) can include a spectrometer capable of measuring the returning light spectroscopically. For these configurations, the photosensitive sensor element 142 can include a spectrometer sensor or spectrometer detector capable of receiving all or a portion of the returning light. For these configurations, the sensor data signal 146 can be a spectrometer output signal that includes data representing light intensity (or amplitude, or other suitable photometric quantity) as a function of wavelength. The processor circuit 148 (described below) can analyze the spectrometer output signal to determine the spectroscopic profile of the target 108 and / or the material composition of the target 108.

[0029] For configurations in which the light detector 140 includes a spectrometer, the laser tissue ablation system 100 can optionally perform an analysis of the target 108 based on the returned light. For example, the optical fiber 116 can collect at least a portion of the therapeutic light pulse reflected from the target 108 as a collected therapeutic light pulse. The optical fiber 116 can direct at least a portion of the collected therapeutic light pulse along the optical fiber 116 and away from the distal end 118 of the optical fiber 116 as a returned therapeutic light pulse. The spectrometer can analyze the returned therapeutic light pulse. In some examples, the processor circuit 148 (described below) can use the spectroscopic profile of the target 108 to determine the material composition of the target 108, such as by matching the measured spectroscopic profile of the target 108 with one or more of a specified (finite) plurality of predetermined spectroscopic profiles corresponding to known materials. These are merely examples, and other suitable analyses of the target 108 can be performed.

[0030] The laser tissue ablation system 100 may include a processor circuit 148. In some examples, the processor circuit 148 may be referred to as a controller. In some examples, the processor circuit 148 may be implemented purely in software. In some examples, the processor circuit 148 may be implemented purely in hardware. In some examples, the processor circuit 148 may be implemented as a combination of software and hardware. In some examples, the processor circuit 148 may be implemented on a single processor. In some examples, the processor circuit 148 may be implemented on multiple processors. In some examples, the multiple processors may be housed within a common housing. In some examples, at least two of the multiple processors may be spaced apart within different housings.

[0031] In some examples, the free-space optical coupler / splitter 124, the photodetector 140, and the processing circuitry 148 can be contained within a housing 150. The therapeutic laser source 114 can direct laser light into the housing via a therapeutic laser source optical fiber 122. The optical fiber 116 can direct the laser light from the housing 150 to the endoscope 102 and tether the endoscope 102 to the housing 150. The video display 112 can optionally be attached to or integrated with the housing 150.

[0032] The processor circuitry 148 can perform time-of-flight analysis of the sensed return light pulses to determine the spacing (Z) (e.g., real-time separation) between the distal end 118 of the optical fiber 116 and the target 108. The processor circuitry 148 can use one or more measurement techniques to determine the spacing (Z), some examples of which are described herein.

[0033] In some examples, the processor circuit 148 can perform time-of-flight analysis of the sensed return optical pulses by determining, for each individual return optical pulse, the duration between the sensing of the return optical pulse by the photodetector and the arrival of the corresponding reference signal. In other words, the processor circuit 148 can determine the interval (Z) by directly sensing the arrival time of a particular pulse. Three examples of direct sensing techniques are as follows:

[0034] In a first example, the distal end 118 of the optical fiber 116 can generate a reflection that can form a reference signal. The measurement light pulse can reflect from the distal end 118 of the optical fiber 116 to form a reference light pulse that propagates along the optical fiber 116 away from the distal end 118 of the optical fiber 116. The duration between the arrival of the reference signal (reflected from the distal end 118 of the optical fiber 116) and the returning light pulse (reflected from the target 108) represents the round-trip time of the returning light pulse as it propagates from the distal end 118 of the optical fiber 116 to the target 108 and back. The physical separation can be calculated as half the round-trip duration multiplied by the speed of light in a vacuum, divided by the refractive index of the medium between the optical fiber 116 and the target 108 (which can be approximated as water).

[0035] In a second example, the measurement light source 158 can generate a reference electrical pulse at a time corresponding to the measurement light pulse so that the reference electrical pulse can directly form the reference signal (e.g., rather than a signal resulting from detection of the pulse).

[0036] In a third example, the measurement light source 158 can include a first light source 158A capable of generating a first measurement light pulse at a first wavelength and a second light source 158B capable of generating a second measurement light pulse at a second wavelength different from the first wavelength. The optical fiber 116 can include a fiber material having non-zero dispersion such that the first measurement light pulse and the second measurement light pulse propagate along the optical fiber 116 at different velocities given by the speed of light in a vacuum divided by the respective refractive indices of the fiber material at the respective wavelengths. The first measurement light pulse can form a return light pulse. The second measurement light pulse can be sensed by the photodetector 140 to form a corresponding reference signal.

[0037] These are just three examples of measurement techniques for determining the interval (Z) by directly sensing the arrival time of a particular pulse. Other direct sensing techniques can also be used.

[0038] Alternatively, the processor circuit 148 can perform a time-of-flight analysis of the sensed return light pulses without directly sensing the arrival time of a particular pulse. For example, in one example of such an indirect measurement technique, the processor circuit 148 can perform a time-of-flight analysis of the sensed return light pulses by determining, for each return light pulse, a first amount of accumulated light for a first duration of the return light pulse, a second amount of accumulated light for a second duration of the return light pulse, and using a ratio of the first and second amounts of accumulated light to determine the spacing between the distal end of the optical fiber and the target. Further details regarding indirect measurement techniques are provided in U.S. Patent Application Publication No. 2021 / 0161364, which is incorporated herein by reference in its entirety.

[0039] In some examples, the measurement light source 158 can be a LIDAR (light detection and ranging) light source. In some examples, the light detector 140 can include a LIDAR detector 162. In some examples, the laser tissue ablation system can further include a beam splitter 164 that can separate the return light pulse from the return therapeutic light pulse, direct the return light pulse to the LIDAR detector 162, and direct the return therapeutic light pulse to a spectrometer (such as in the sensor circuit 144). In some examples, the processor circuit 148 can electronically communicate data representing the determined spacing (Z) to the spectrometer (such as in the sensor circuit 144).

[0040] The processor circuitry 148 can take one or more actions in response to determining the spacing (Z) (e.g., real-time separation) between the distal end 118 of the optical fiber 116 and the target 108. Some examples of such actions are as follows:

[0041] In a first example, the processor circuit 148 can generate an interval data signal representing the determined interval (Z). In some examples, the interval data signal can be a digital signal. For example, the interval data signal can include a variable stored in memory. The variable can have a value corresponding to the determined interval (Z). In some examples, the interval data signal can be an analog signal. For example, the interval data signal can include an electrical signal having a voltage value corresponding to the determined interval (Z). Other interval data signals can also be used. The processor circuit 148 can optionally transmit the interval data signal, or data corresponding to the interval data signal, to one or more other components of the laser tissue ablation system 100 so that the other components can take one or more actions in response to receiving the value of the determined interval (Z).

[0042] In a second example, the processor circuit 148 can retract the optical fiber 116 proximally (e.g., by increasing the spacing (Z)), such as to avoid a flashing event that could damage the distal end 118 of the optical fiber 116. For example, the laser tissue ablation system 100 can further include an actuator 152 that can advance the optical fiber 116 distally and retract the optical fiber 116 proximally relative to the endoscope 102. In some examples, as in the configuration of FIG. 1 , the actuator 152 can include a wheel. The wheel can have a center that is fixed in position relative to the endoscope 102. The wheel can have a circumferential surface that contacts the optical fiber 116. The wheel can be rotatable from a rotary actuator, such as a rotary actuator located at or near the center of the wheel. In some examples, the processor circuit 148 can compare the determined spacing (Z) with a specified threshold and cause the actuator 152 to automatically reduce the difference between the determined spacing (Z) and the specified threshold. The use of such a threshold can effectively create a servo that can maintain the distal end 118 of the optical fiber 116 at a constant distance from the target 108 .

[0043] In a third example, the processor circuit 148 can vary at least one operating parameter of the therapeutic laser light source 114 in response to the determined interval (Z) as represented by the interval data signal. For example, if the determined interval (Z) as represented by the interval data signal is less than a specified threshold interval, the processor circuit 148 automatically turns off the therapeutic laser light source. In other words, if the processor circuit 148 determines that the interval (Z) is less than a specified threshold, such as close enough to initiate a flashing event that could damage the distal end 118 of the optical fiber 116, the processor circuit 148 can cause the therapeutic laser light source 114 to reduce the output power of the therapeutic laser light source 114, such as by automatically turning off the therapeutic laser light source 114. Reducing the output power and / or turning off the therapeutic laser light source 114 can optionally be used in combination with another action, such as causing the actuator 152 to increase the determined interval (Z).

[0044] In a fourth example, the video display 112, which can display a video image captured by the video camera 110 of the target 108 illuminated by the illumination source 104, can additionally display a visual representation of the determined spacing (Z) represented by the spacing data signal. In some examples, the visual representation can include one or more numbers corresponding to the determined spacing (Z) in appropriate units, such as mm. In some examples, the visual representation can include one or more colors. For example, the video display 112 can display green when the determined spacing (Z) is within a specified range (e.g., a desired range for optimal operation of the laser tissue ablation system 100), yellow when the determined spacing (Z) is just outside the range, and red when the determined spacing (Z) is relatively far outside the range. Other color schemes can also be used. Other visual representations can also be used. In some examples, the laser tissue ablation system 100 can optionally provide an audio alert that can alert the practitioner to the determined spacing (Z).

[0045] These are just four examples of actions that may be taken in response to determining the spacing (Z) (e.g., real-time separation) between the distal end 118 of the optical fiber 116 and the target 108. These actions may be performed alone or in any combination. Other actions may also be taken.

[0046] 2 shows a flowchart of an example method 200 for operating a laser tissue ablation system, such as laser tissue ablation system 100 of FIG. 1 or any other suitable laser tissue ablation system. The laser tissue ablation system may include an endoscope and an optical fiber including a distal end extending from the endoscope. Method 200 is merely one example method for operating a laser tissue ablation system, and other methods may be used.

[0047] In operation 202, the optical fiber can receive a therapeutic laser light pulse at a first time.

[0048] In operation 204, the optical fiber can receive the measurement light pulse at a second time different from the first time.

[0049] In operation 206, the optical fiber can direct the therapeutic laser light pulse and the measurement light pulse along the optical fiber so that they emerge from the distal end of the optical fiber towards the target.

[0050] In operation 208, the optical fiber may collect at least a portion of the measurement light pulse reflected from the target as a collected light pulse.

[0051] In operation 210, the optical fiber can direct at least a portion of the collected light pulses as return light pulses along the optical fiber and away from the distal end of the optical fiber.

[0052] In operation 212, a photodetector may sense at least a portion of the returning light pulse.

[0053] In operation 214, the processor circuit may perform a time-of-flight analysis of the sensed return light pulses to determine the spacing between the distal end of the optical fiber and the target.

[0054] In operation 216, the processor circuit may generate an interval data signal representative of the determined interval.

[0055] In some examples, performing time-of-flight analysis may include determining, for each return light pulse, the duration between sensing the return light pulse by the photodetector and the arrival of the corresponding reference signal.

[0056] In some examples, performing the time-of-flight analysis can include determining, for each return light pulse, a first amount of accumulated light for a first duration of the return light pulse, determining a second amount of accumulated light for a second duration of the return light pulse, and using a ratio of the first and second amounts of accumulated light to determine a spacing between the distal end of the optical fiber and the target.

[0057] In some examples, method 200 optionally further includes collecting, with an optical fiber, at least a portion of the therapeutic light pulse reflected from the target as a collected therapeutic light pulse; directing at least a portion of the collected therapeutic light pulse along the optical fiber away from a distal end of the optical fiber as a return therapeutic light pulse; analyzing, with a spectrometer, the return therapeutic light pulse; and electronically communicating data representing the determined interval to the spectrometer.

[0058] 3 shows a schematic diagram of an exemplary computer-based clinical decision support system (CDSS) 300 configured to provide a distance (Z) value. For example, the optical properties can include the optical power / intensity (I) of the returned light. In various embodiments, the CDSS 300 includes an input interface 302 in which the patient-specific optical properties are provided as input features to an artificial intelligence (AI) model 304, a processor such as the processor circuit 148 that performs inference operations in which the optical properties are applied to the AI ​​model to generate a distance (Z) value, and a user interface (UI) in which the distance (Z) value is communicated to a user, e.g., a clinician.

[0059] In some embodiments, the input interface 302 may be a direct data link between the CDSS 300 and one or more medical devices, such as the laser tissue ablation system 100 or endoscope 102, that generate at least a portion of the input features. For example, the input interface 302 may transmit optical properties directly to the CDSS during a therapeutic and / or diagnostic medical procedure. Additionally or alternatively, the input interface 302 may be a classic user interface that facilitates interaction between a user and the CDSS 300. For example, the input interface 302 may facilitate a user interface through which a user may manually input optical properties. Additionally or alternatively, the input interface 302 may provide the CDSS 300 with access to an electronic patient record from which one or more input features may be extracted. In any of these cases, the input interface 302 is configured to collect optical properties associated with a particular patient at or before the CDSS 300 is used to evaluate a medical condition addressed by the laser tissue ablation system 100 or endoscope 102, such as a kidney stone.

[0060] Based on one or more of the above input features, a processor, such as the processor circuit 148, performs an inference operation using an AI model to generate a distance (Z) value. For example, the input interface 302 can deliver optical properties to an input layer of the AI ​​model, which propagates the input features through the AI ​​model to an output layer. An AI model can provide a computer system with the ability to perform tasks without being explicitly programmed by making inferences based on patterns discovered in analyzing data. AI models explore the study and construction of algorithms (e.g., machine learning algorithms) that can learn from existing data and make predictions about new data. Such algorithms operate by building an AI model from example training data to make data-driven predictions or decisions, which are expressed as outputs or evaluations.

[0061] There are two general modes of machine learning (ML): supervised and unsupervised. Supervised ML uses prior knowledge (e.g., examples that associate inputs with outputs or outcomes) to learn relationships between inputs and outputs. The goal of supervised ML is to learn a function that best approximates the relationship between training inputs and outputs, given some training data, so that the ML model can implement the same relationship when given the input to generate the corresponding output. Unsupervised ML is the training of an ML algorithm using unclassified or unlabeled information, allowing the algorithm to act on that information without guidance. Unsupervised ML is useful in exploratory analysis because it can automatically identify structure in data.

[0062] Common tasks for supervised ML are classification and regression problems. Classification problems, also called categorization problems, aim to classify an item into one of several categorical values ​​(e.g., is this object an apple or an orange?). Regression algorithms aim to quantify some items (e.g., by providing a score for the value of some input). Some examples of commonly used supervised ML algorithms are logistic regression (LR), naive Bayes, random forest (RF), neural networks (NN), deep neural networks (DNN), matrix decomposition, and support vector machines (SVM).

[0063] Some common tasks for unsupervised ML include clustering, representation learning, and density estimation. Some examples of commonly used unsupervised ML algorithms are k-means clustering, principal component analysis, and autoencoders.

[0064] Another type of ML is federated learning (also known as collaborative learning), which trains algorithms across multiple distributed devices that hold local data without exchanging data. This approach contrasts with traditional centralized machine learning techniques, where all local datasets are uploaded to a single server, as well as more classical distributed approaches that often assume local data samples are identically distributed. Federated learning allows multiple actors to build a common, robust machine learning model without sharing data, thus addressing important issues such as data privacy, data security, data access rights, and access to heterogeneous data.

[0065] In some examples, the AI ​​model may be continuously or periodically trained prior to execution of an inference operation by a processor, such as processor circuitry 148. Then, during the inference operation, patient-specific input features provided to the AI ​​model may be propagated from an input layer, through one or more hidden layers, and ultimately to an output layer corresponding to a distance (Z) value.

[0066] In some examples, the AI ​​model can include a database that can include data corresponding to the patient. The database can provide the patient record to the CDSS 300. In some examples, the AI ​​model can receive optical properties from a sensor, such as the photodetector 140 or the LIDAR detector 162.

[0067] During and / or following the inference operation, the distance (Z) value may be communicated to a user via a user interface (UI) and / or may cause an actuator or alarm connected to the processor to automatically perform a desired action. For example, the processor may cause an actuator to move the optical fiber relative to the endoscope. Alternatively, the processor may cause an alarm to alert the practitioner.

[0068] In some examples, the CDSS 300 may optionally be used to determine the action to be taken in response to the value of distance (Z).

[0069] Some features described herein may provide methods and devices that can distinguish between various target compositions, for example, in endoscopic in vivo medical applications (e.g., hard or soft tissue). This may allow an operator to continuously monitor the composition of the target viewed through the endoscope throughout the procedure. This may also be used in conjunction with a laser system, in which case the method may provide feedback to the laser system to adjust settings based on the target composition. This feature may allow for instantaneous adjustment of laser settings within the setting range of the original laser settings selected by the operator.

[0070] Some features described herein can be used to provide systems and methods that measure differences in the chemical composition of a target in vivo and suggest or automatically adjust laser settings to better achieve a desired effect. Examples of targets and applications include laser lithotripsy of kidney stones and laser ablation or vaporization of soft tissue. In one example, three major components are provided: a laser, a spectroscopy system, and a feedback analyzer. In one example, a laser system controller can automatically program laser treatment with appropriate laser parameter settings based on the target composition. In one example, the laser can be controlled based on a machine learning algorithm trained using spectroscopy data. Additionally or alternatively, the operator can continuously receive indications of target type during treatment and be prompted to adjust laser settings. By adjusting laser settings and adapting laser treatment to the compositional components of a single stone target, stone ablation or dusting procedures can be performed faster and more energy-efficiently.

[0071] Some features described herein may provide systems and methods for providing data input to a feedback analyzer, including internet connectivity and connectivity to other surgical devices with measurement capabilities. In addition, the laser system may provide input data to another system, such as an image processor, so that a treatment monitor can display information related to the medical treatment to the operator. One example of this is more clearly distinguishing between different soft tissues, vasculature, overlying tissues, and different chemical compositions within the same target, such as a stone, within the field of view during treatment.

[0072] Some features described herein may provide systems and methods for identifying different target types, such as different tissue types or different stone types. In some cases, a single stone structure (e.g., a kidney stone, bladder stone, pancreaticobiliary stone, or gallbladder stone) may have two or more different compositions throughout its volume, such as brushite, calcium phosphate (CaP), calcium oxalate dihydrate (COD), calcium oxalate monohydrate (COM), ammonium magnesium phosphate (MAP), or a cholesterol- or uric acid-based stone structure. For example, the target stone structure may include a first portion of COD and a second portion of COM. According to one aspect, this document describes systems and methods for continuously identifying different compositions contained within a single target (e.g., a single stone) based on continuous collection and analysis of in vivo spectroscopic data. Treatment (e.g., laser therapy) may be adapted according to the identified target composition. For example, in response to identifying a first composition (e.g., COD) within a target stone, the laser system may be programmed with a first laser parameter setting (e.g., power, exposure time, or launch angle, etc.) and deliver a laser beam accordingly to ablate or pulverize the first portion. Spectroscopic data may be continuously collected and analyzed during laser treatment. In response to identifying a second composition (e.g., COM) within the same target stone being treated that is different from the first composition, the laser treatment may be adjusted, such as by programming the laser system with a second laser parameter setting (e.g., different power, exposure time, or launch angle, etc.) that is different from the first laser parameter setting, and deliver a laser beam accordingly to ablate or pulverize the second portion of the same target stone. In some examples, multiple different laser sources may be included within the laser system. Stone portions of different compositions may be treated by different laser sources. The appropriate laser to use may be determined by identifying the stone type.

[0073] Some features described herein may be used in connection with laser systems for various applications where incorporating different types of laser sources may be advantageous. For example, the features described herein may be suitable in industrial or medical settings, such as medical diagnostics, treatments, and surgical procedures. The features described herein may be used in connection with endoscopy, laser surgery, laser lithotripsy, laser settings, and / or spectroscopy.

[0074] In the foregoing detailed description, the method and apparatus of the present disclosure have been described with reference to specific embodiments thereof. It will, however, be apparent that various modifications and changes may be made thereto without departing from the broader spirit and scope of the present disclosure. The present specification and figures are therefore to be regarded as illustrative rather than restrictive.

[0075] To further illustrate the devices and related methods disclosed herein, a non-limiting list of examples is provided below. Each of the following non-limiting examples can stand alone or can be combined with any one or more of the other examples in any permutation or combination.

[0076] In Example 1, a laser tissue ablation system can include an endoscope; an optical fiber including a distal end extending from the endoscope, the optical fiber configured to receive a therapeutic laser light pulse at a first time and receive a measurement light pulse at a second time different from the first time; direct the therapeutic laser light pulse and the measurement light pulse along the optical fiber to emerge from the distal end of the optical fiber toward a target; collect at least a portion of the measurement light pulse reflected from the target as collected light pulses; and direct at least a portion of the collected light pulses along the optical fiber away from the distal end of the optical fiber as return light pulses; a photodetector configured to sense at least a portion of the return light pulses; and a processor circuit configured to perform time-of-flight analysis of the sensed return light pulses to determine a spacing between the distal end of the optical fiber and the target; and generate a spacing data signal representative of the determined spacing.

[0077] In Example 2, the laser tissue ablation system of Example 1 can optionally further include a therapeutic laser light source spaced from the endoscope and configured to generate a therapeutic laser light pulse at a first time, and a measurement light source spaced from the endoscope and configured to generate a measurement light pulse at a second time.

[0078] In Example 3, the laser tissue ablation system of any one of Examples 1-2 can be optionally configured such that the processor circuit is configured to perform time-of-flight analysis of the sensed return light pulses by determining, for each return light pulse, the duration between sensing the return light pulse by the photodetector and the arrival of a corresponding reference signal.

[0079] In Example 4, the laser tissue ablation system of any one of Examples 1-3 can be optionally configured such that the measurement light pulse reflects from the distal end of the optical fiber to form a reference light pulse that propagates along the optical fiber away from the distal end of the optical fiber, and the photodetector is further configured to sense at least a portion of the reference light pulse and form a reference signal in response thereto.

[0080] In Example 5, the laser tissue ablation system of any one of Examples 1-4 can be optionally configured such that the measurement light source is further configured to generate a reference electrical pulse at a time corresponding to the measurement light pulse, the reference electrical pulse forming a reference signal.

[0081] In Example 6, the laser tissue ablation system of any one of Examples 1-5 can be optionally configured such that the measurement light source includes a first light source configured to generate a first measurement light pulse at a first wavelength and a second light source configured to generate a second measurement light pulse at a second wavelength different from the first wavelength, the optical fiber includes a fiber material having non-zero dispersion such that the first measurement light pulse and the second measurement light pulse propagate along the optical fiber at different velocities, the first measurement light pulse forms a return light pulse, and the second measurement light pulse is sensed by the photodetector to generate a corresponding reference signal.

[0082] In Example 7, the laser tissue ablation system of any one of Examples 1-6 can be optionally configured such that the processor circuit is configured to perform time-of-flight analysis of the sensed return light pulses by determining, for each return light pulse, a first amount of accumulated light for a first duration of the return light pulse, determining a second amount of accumulated light for a second duration of the return light pulse, and using a ratio of the first and second amounts of accumulated light to determine a spacing between the distal end of the optical fiber and the target.

[0083] In Example 8, the laser tissue ablation system of any one of Examples 1-7 optionally further comprises an actuator configured to advance the optical fiber distally and retract the optical fiber proximally relative to the endoscope, and the processor circuitry is further configured to compare the determined interval with a specified threshold and cause the actuator to automatically reduce a difference between the determined interval and the specified threshold.

[0084] In Example 9, the laser tissue ablation system of any one of Examples 1-8 can be optionally configured such that the actuator comprises a wheel, the wheel having a center fixed in position relative to the endoscope, the wheel having a circumferential surface in contact with the optical fiber, and the wheel is rotatable from a rotary actuator.

[0085] In Example 10, the laser tissue ablation system of any one of Examples 1-9 can be optionally configured such that the processor circuit is further configured to vary at least one operating parameter of the therapeutic laser source in response to the determined interval represented by the interval data signal.

[0086] In Example 11, the laser tissue ablation system of any one of Examples 1-10 can be optionally configured such that if the determined interval represented by the interval data signal is less than a specified threshold interval, the processor circuitry is further configured to automatically turn off the therapeutic laser light source.

[0087] In Example 12, the laser tissue ablation system of any one of Examples 1-11 can optionally further include an illumination light source disposed at the distal end of the endoscope and configured to illuminate a target with visible illumination light; a camera disposed at the distal end of the endoscope and configured to generate a video image of the illuminated target; and a display coupled to the processor circuit and configured to display the video image of the illuminated target and a visual representation of the determined interval represented by the interval data signal.

[0088] In Example 13, the laser tissue ablation system of any one of Examples 1-12 can be optionally configured such that the therapeutic laser light source is configured to direct therapeutic laser light pulses along a first optical path, the measurement light source is configured to direct measurement light pulses along a second optical path, the measurement light pulses are spectrally separated from the therapeutic laser light pulses, and the laser tissue ablation system further comprises a dichroic beam splitter positioned to combine the first and second optical paths so as to be aligned along a third optical path extending into the optical fiber.

[0089] In Example 14, the laser tissue ablation system of any one of Examples 1-13 can be optionally configured such that the optical fiber is further configured to collect at least a portion of the therapeutic light pulse reflected from the target as a collected therapeutic light pulse and direct at least a portion of the collected therapeutic light pulse along the optical fiber away from a distal end of the optical fiber as a return therapeutic light pulse, and the laser tissue ablation system further comprises a spectrometer configured to analyze the return therapeutic light pulse.

[0090] In Example 15, the laser tissue ablation system of any one of Examples 1-14 can be optionally configured such that the measurement light source is a LIDAR light source and the light detector is a LIDAR detector, the laser tissue ablation system further comprising a beam splitter configured to separate the return light pulse from the return therapeutic light pulse and direct the return light pulse to the LIDAR detector and direct the return therapeutic light pulse to the spectrometer, and the processor circuitry is configured to electronically communicate data representing the determined interval to the spectrometer.

[0091] In Example 16, a method for operating a laser tissue ablation system including an endoscope and an optical fiber including a distal end extending from the endoscope includes receiving a therapeutic laser light pulse at a first time using the optical fiber; receiving a measurement light pulse at a second time different from the first time using the optical fiber; directing the therapeutic laser light pulse and the measurement light pulse along the optical fiber so that they emerge from the distal end of the optical fiber toward a target; collecting, using the optical fiber, at least a portion of the measurement light pulse reflected from the target as collected light pulses; directing at least a portion of the collected light pulses along the optical fiber away from the distal end of the optical fiber as return light pulses; sensing, using a photodetector, at least a portion of the return light pulses; performing time-of-flight analysis of the sensed return light pulses to determine a spacing between the distal end of the optical fiber and the target; and generating a spacing data signal representative of the determined spacing.

[0092] In Example 17, the method of Example 16 can be optionally configured such that performing the time-of-flight analysis includes determining, for each return optical pulse, the duration between sensing the return optical pulse by the optical detector and the arrival of a corresponding reference signal.

[0093] In Example 18, the method of any one of Examples 16-17 can be optionally configured such that the step of performing the time-of-flight analysis includes, for each return light pulse, determining a first amount of accumulated light for a first duration of the return light pulse, determining a second amount of accumulated light for a second duration of the return light pulse, and using a ratio of the first and second amounts of accumulated light to determine a spacing between the distal end of the optical fiber and the target.

[0094] In Example 19, the method of any one of Examples 16-18 can optionally further include collecting, with an optical fiber, at least a portion of the therapeutic light pulse reflected from the target as a collected therapeutic light pulse; directing at least a portion of the collected therapeutic light pulse along the optical fiber away from a distal end of the optical fiber as a return therapeutic light pulse; analyzing, with a spectrometer, the return therapeutic light pulse; and electronically communicating data representing the determined interval to the spectrometer.

[0095] In Example 20, a laser tissue ablation system includes a therapeutic laser light source configured to generate therapeutic laser light pulses at a first time; a measurement light source configured to generate measurement light pulses at a second time different from the first time; an endoscope spaced from the therapeutic laser light source and the measurement light source; and an optical fiber including a distal end extending from the endoscope, the optical fiber including: directing the therapeutic laser light pulses and the measurement light pulses along the optical fiber to emerge from the distal end of the optical fiber toward a target; collecting at least a portion of the measurement light pulses reflected from the target as collected light pulses; directing at least a portion of the collected light pulses along the optical fiber away from the distal end of the optical fiber as return light pulses; collecting at least a portion of the therapeutic light pulses reflected from the target as collected therapeutic light pulses; and directing at least a portion of the collected therapeutic light pulses as return therapeutic light pulses through the optical fiber. and directing the returned therapeutic light pulses along a distance away from the distal end of the optical fiber; a photodetector configured to sense at least a portion of the returned therapeutic light pulses; a spectrometer configured to analyze the returned therapeutic light pulses; a processor circuit configured to perform a time-of-flight analysis of the sensed returned therapeutic light pulses to determine a distance between the distal end of the optical fiber and the target, generate a distance data signal representative of the determined distance, and electronically communicate the distance data signal to the spectrometer; an illumination light source disposed at the distal end of the endoscope and configured to illuminate the target with visible illumination light; a camera disposed at the distal end of the endoscope and configured to generate a video image of the illuminated target; and a display coupled to the processor circuit and configured to display the video image of the illuminated target and a visual representation of the determined distance represented by the distance data signal. [Explanation of symbols]

[0096] 100 Laser Tissue Ablation System 102 Endoscope 104 Lighting source 106 Distal end 108 Target 110 Video Camera 112 Video Display 114 Therapeutic laser light source 116 Optical Fiber 118 Distal end 120 proximal part 122 Therapeutic laser light source optical fiber 124 Free Space Optical Coupler / Splitter 126 Collimating Lens 128 Distal End 130 Return Path Beam Splitter 132 Bidirectional focusing lens 134 Return path focusing lens 136 edge 138 Return path optical fiber 140 Photodetector 142 Photosensitive sensor element 144 Sensor Circuit 146 Analog or digital sensor data signals, sensor data signals 148 Processor Circuit 150 Housing 152 Actuator 158 Measurement light source 158A First Light Source 158B Second Light Source 160 Incident Path Beam Splitter 162 LIDAR detectors 164 Beam Splitter 300 Clinical Decision Support System (CDSS), CDSS 302 Input Interface 304 Artificial Intelligence (AI) Models

Claims

1. 1. A laser tissue ablation system comprising: An endoscope and an optical fiber including a distal end extending from the endoscope, receiving a therapeutic laser light pulse at a first time; receiving a measurement light pulse at a second time different from the first time; directing the therapeutic laser light pulse and the measurement light pulse along the optical fiber so that they emerge from the distal end of the optical fiber toward a target; collecting at least a portion of the measurement light pulse reflected from the target as a collected light pulse; directing at least a portion of the collected light pulses as return light pulses along the optical fiber away from the distal end of the optical fiber; an optical fiber configured to a spectrometer configured to sense at least a portion of the returned light pulses and analyze the returned light pulses; 1. A processor circuit, comprising: performing a time-of-flight analysis of the sensed return light pulses to determine a distance between the distal end of the optical fiber and the target; generating a spacing data signal representative of the determined spacing; a processor circuit configured to: Equipped with the laser tissue ablation system comprises: a therapeutic laser light source spaced from the endoscope and configured to generate the therapeutic laser light pulse at the first time; a measurement light source spaced from the endoscope and configured to generate the measurement light pulse at the second time; The optical fiber collecting at least a portion of the therapeutic laser light pulse reflected from the target as a collected therapeutic light pulse; directing at least a portion of the collected therapeutic light pulses as return therapeutic light pulses along the optical fiber away from the distal end of the optical fiber; further configured to: The laser tissue ablation system, wherein the processor circuit is further configured to automatically turn off the therapeutic laser source if the determined interval represented by the interval data signal is less than a specified threshold interval.

2. 2. The laser tissue ablation system of claim 1, wherein the processor circuit is configured to perform the time-of-flight analysis of the sensed return light pulses by determining, for each return light pulse, the duration between the sensing of the return light pulse by the spectrometer and the arrival of a corresponding reference signal.

3. the measurement light pulse reflects from the distal end of the optical fiber to form a reference light pulse that propagates along the optical fiber away from the distal end of the optical fiber; the spectrometer is further configured to sense at least a portion of the reference light pulse and form the reference signal in response thereto.

3. The laser tissue ablation system of claim 2.

4. 3. The laser tissue ablation system of claim 2, wherein the measurement light source is further configured to generate a reference electrical pulse at a time corresponding to the measurement light pulse, the reference electrical pulse forming the reference signal.

5. the therapeutic laser light source is configured to direct the therapeutic laser light pulses along a first optical path; the measurement light source is configured to direct the measurement light pulse along a second optical path, the measurement light pulse being spectrally separated from the treatment laser light pulse; the laser tissue ablation system further comprising a dichroic beam splitter positioned to combine the first and second optical paths so as to be aligned along a third optical path extending within the optical fiber; 10. The laser tissue ablation system of claim 1.

6. 10. The laser tissue ablation system of claim 1, wherein the processor circuit is further configured to automatically turn off the therapeutic laser source if the determined interval represented by the interval data signal is less than a specified threshold interval.

7. The processor circuit, for each returned optical pulse: determining a first amount of accumulated light for a first duration of the returned light pulse; determining a second amount of accumulated light for a second duration of the returned light pulse; using a ratio of the first and second amounts of accumulated light to determine the spacing between the distal end of the optical fiber and the target; configured to perform the time-of-flight analysis of the sensed return light pulses by 10. The laser tissue ablation system of claim 1.

8. an actuator configured to distally advance the optical fiber and proximally retract the optical fiber relative to the endoscope; the processor circuitry comprises: comparing the determined interval with a specified threshold; causing the actuator to automatically reduce the difference between the determined interval and the specified threshold. further configured as follows:

10. The laser tissue ablation system of claim 1.

9. the actuator comprises a wheel; the wheel having a center fixed in position relative to the endoscope; the wheel has a peripheral surface that contacts the optical fiber; the wheel is rotatable relative to a rotary actuator; 9. The laser tissue ablation system of claim 8.

10. an illumination source disposed at a distal end of the endoscope and configured to illuminate the target with visible illumination light; a camera disposed at the distal end of the endoscope and configured to generate a video image of the illuminated target; a display coupled to the processor circuit and configured to display the video image of the illuminated target and a visual representation of the determined distance represented by the distance data signal; 10. The laser tissue ablation system of claim 1, further comprising:

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