Patent Application
20230404383
The present invention relates to laser scanning methods, laser irradiation devices, and laser scanning programs.
A known medical device in the related art scans a laser beam for treatment or imaging (e.g., see Non Patent Literatures 1 and 2). In Non Patent Literatures 1 and 2, an optical fiber is vibrated by an actuator to scan a laser beam emitted from the distal end of the optical fiber. In detail, Non Patent Literature 1 uses an electromagnetic actuator having a magnet bead fixed to the optical fiber and a solenoid disposed around the magnet bead. Non Patent Literature 2 uses a piezoelectric actuator having a piezoelectric element fixed to the optical fiber.
A first aspect of the present invention provides a laser scanning method including emitting a pulsed laser beam from a distal end of an optical fiber in a liquid medium during a first period, the pulsed laser beam being emitted for generating a bubble at the distal end; stopping emission of the pulsed laser beam from the distal end during a second period, wherein the first period is a period for moving the optical fiber closer toward an operation member disposed parallel to the optical fiber by utilizing contraction of the bubble that comes into contact with or close to the operation member, and wherein the second period is a period for moving the optical fiber away from the operation member. The laser scanning method further includes: changing a frequency of the pulsed laser beam; detecting movement of the optical fiber at each frequency; determining a resonance frequency of the optical fiber based on the detected movement; and determining a timing for emitting the pulsed laser beam from the distal end based on the resonance frequency of the optical fiber.
Another aspect of the present invention provides a laser irradiation device including an optical fiber that emits a pulsed laser beam from a distal end thereof in a liquid medium; a processor having a hardware, the processor controlling the laser beam emitted from the optical fiber; and a movement detector that detects movement of the optical fiber, wherein the processor is configured to emit the pulsed laser beam from the distal end during a first period, the pulsed laser beam being emitted for generating a bubble at the distal end, and wherein the processor is configured to stop emission of the pulsed laser beam from the distal end during a second period, wherein the first period is a period for moving the optical fiber closer toward an operation member disposed parallel to the optical fiber by utilizing contraction of the bubble that comes into contact with or close to the operation member, and wherein the second period is a period for moving the optical fiber away from the operation member, wherein the processor is configured to: change a frequency of the pulsed laser beam; detect movement of the optical fiber at each frequency based on information from the movement detector; determine a resonance frequency of the optical fiber based on the detected movement; and determine a timing for emitting the pulsed laser beam from the distal end based on the resonance frequency.
Another aspect of the present invention provides a storage medium storing a laser scanning program causing a laser irradiation device to execute: emitting a pulsed laser beam from a distal end of an optical fiber in a liquid medium during a first period, the pulsed laser beam being emitted for generating a bubble at the distal end; stopping emission of the pulsed laser beam from the distal end during a second period, wherein the first period is a period for moving the optical fiber closer toward an operation member disposed parallel to the optical fiber by utilizing contraction of the bubble that comes into contact with or close to the operation member, and wherein the second period is a period for moving the optical fiber away from the operation member, wherein the laser scanning program causes the laser irradiation device to execute: changing a frequency of the pulsed laser beam and detecting movement of the optical fiber at each frequency; determining a resonance frequency of the optical fiber based on the detected movement; and determining a timing for emitting the pulsed laser beam from the distal end based on the resonance frequency.
A laser scanning method and a laser irradiation device according to an embodiment of the present invention will be described below with reference to the drawings.
As shown in
The endoscope 10 is, for example, a rigid or flexible ureteroscope and has a surgical-tool channel 10a extending longitudinally through the endoscope 10. The endoscope 10 acquires an endoscopic image including a distal end 2a (to be described later) of an optical fiber 2, inserted into the body via the surgical-tool channel 10a, and the treatment target A.
The display unit 20 is a display device of any type, such as a liquid crystal display, and displays the endoscopic image acquired by the endoscope 10.
The laser irradiation device 1 includes the optical fiber 2, a tubular sheath (support member) 3 that supports the optical fiber 2, an operation member 4, a laser oscillator 5, a movement detector 6, a storage unit 7, and a processor 8.
The optical fiber 2 is, for example, a single-mode fiber having a cladding diameter of 125 μm. The optical fiber 2 may be a multi-mode fiber or a double cladding fiber.
The sheath 3 is insertable into the surgical-tool channel 10a. The optical fiber 2 extends through the sheath 3 in the longitudinal direction of the sheath 3, and the distal end of the optical fiber 2 protrudes from the distal end of the sheath 3.
A distal end 3a of the sheath 3 is a support section that supports the optical fiber 2 at a position located at a base end side relative to a distal end 2a of the optical fiber 2 with a distance. The inner diameter of the support section 3a is smaller than the inner diameter of other sections of the sheath 3, and is equal to the outer diameter of the optical fiber 2 or slightly larger than the outer diameter of the optical fiber 2. Therefore, at the support section 3a, the position of the optical fiber 2 is fixed in the radial direction. Accordingly, a vibration region 2b of the optical fiber 2 which is disposed at a distal end side relative to the support section 3a and which includes the distal end 2a is supported in a cantilever manner by the sheath 3, and the vibration region 2b can be vibrated in the radial direction of the optical fiber 2 about a part, acting as a fulcrum, of the optical fiber 2 in the support section 3a.
The operation member 4 is a plate-shaped member disposed parallel to the vibration region 2b and is fixed to the sheath 3. In the reference drawings, the surface at the optical fiber 2 side of the operation member 4 is a flat surface, but may alternatively be a surface having another shape, such as a curved surface.
The operation member 4 is disposed only at one side of the optical fiber 2 in the radial direction. As will be described later, the operation member 4 is provided for applying, to the distal end 2a, a contraction force acting toward the operation member 4 during contraction of a bubble B generated at the distal end 2a. The distance in the radial direction between the distal end 2a at an initial position and the operation member 4 is designed such that the bubble B comes into contact with the operation member 4. In order to cause the bubble B to reliably come into contact with the operation member 4, the distal end of the operation member 4 is preferably disposed at a position where the distal end protrudes relative to the distal end 2a of the optical fiber 2.
The laser oscillator 5 generates a pulsed laser beam L for treating the treatment target A. For example, the laser beam L is an infrared beam, and the laser oscillator 5 is a thulium fiber laser, a holmium YAG laser, a thulium YAG laser, an erbium YAG laser, a pulsed dye laser, or a Q-switch Nd YAG laser. The laser oscillator 5 is connected to the base end of the optical fiber 2 and supplies the laser beam L to the optical fiber 2. The laser beam L is emitted from the distal end 2a toward the treatment target A.
The laser oscillator 5 is connected to a foot switch 9. The laser oscillator 5 generates the laser beam L and supplies it to the optical fiber 2 when the foot switch 9 is pressed.
When the laser irradiation device 1 is used for treating the treatment target A, the treatment target A is surrounded and covered by a liquid medium M, and the vibration region 2b and the operation member 4 disposed outside the sheath 3 are disposed in the medium M. The medium M is a liquid, such as water, a physiological saline solution, a perfusate, a non-electrolytic solution, or a biological fluid like urine.
As shown in
In detail, when the emission of the laser beam L from the distal end 2a starts, the laser beam L is absorbed by the medium M and therefore the temperature of the medium M increases, whereby the bubble B is generated at the distal end 2a (t=t1).
While the laser beam L is being emitted, the bubble B grows and comes into contact with the operation member 4 (t=t2).
Then, when the emission of the laser beam L ends, the bubble B starts to contract, and the distal end 2a moves closer toward the operation member 4 as the bubble B contracts (t=t3 and t4). Specifically, since only one side of the bubble B is in contact with the operation member 4, hydraulic pressure acts unevenly on the bubble B, thus causing the bubble B to contract toward the operation member 4. Accordingly, the distal end 2a receives a contraction force F of the bubble B acting toward the operation member 4, so that the distal end 2a moves closer toward the operation member 4.
Subsequently, the bubble B vanishes and the contraction force F dissipates (t=t5).
After the bubble B vanishes, a restoring force of the vibration region 2b causes the distal end 2a to move away from the operation member 4 (t=t6).
In addition to the case where the bubble B is in contact with the operation member 4, as in t=t2, t3, and t4, the bubble contraction force F acting toward the operation member 4 is applied to the distal end 2a also in a state where the bubble B is not in contact with the operation member 4 since the operation member 4 exists near the bubble B.
As shown in
Each of the first period I and the third period III is the first half of one repetition cycle T1, and the second period II is the second half of one repetition cycle T1. In detail, the first period I is a period in which the optical fiber 2 at the initial position is moved closer toward the operation member 4 in accordance with contraction of the bubble B. The second period II is a period that is subsequent to the first period I or the third period III and in which the optical fiber 2 moves away from the operation member 4. The third period III is a period that is subsequent to the second period II and in which the optical fiber 2 moves closer toward the operation member 4.
The aforementioned pulse group is repeatedly emitted at the repetition frequency f1, so that the distal end 2a vibrates in the radial direction at the repetition frequency f1, as shown in
In
The movement detector 6 detects movement of the optical fiber 2 that is vibrating. The movement at least includes a vibration amplitude of the distal end 2a of the optical fiber 2, and may further include a vibration frequency. In an example, the movement detector 6 has a vibration detection element 6a fixed to the sheath 3. The vibration detection element 6a is, for example, a vibration sensor, a pressure sensor, or a strain gauge. The vibration of the vibration region 2b is transmitted to the vibration detection element 6a via the support section 3a so as to be detected by the vibration detection element 6a. A detection signal output from the vibration detection element 6a changes with the same frequency as the vibration frequency of the vibration region 2b. The amplitude of the detection signal increases with increasing vibration amplitude of the distal end 2a. Therefore, it is possible to detect a vibration frequency and a vibration amplitude of the optical fiber 2 based on the vibration frequency and the vibration amplitude of the detection signal.
The storage unit 7 has a memory, such as a RAM, and a nonvolatile, non-transitory computer-readable storage medium, such as a ROM or an HDD. The storage medium stores a laser scanning program therein.
The processor 8 has hardware, such as a central processing unit, and executes a laser scanning method, to be described below, in accordance with the laser scanning program.
Next, the laser scanning method according to this embodiment executed by the processor 8 will be described.
As shown in
In step S1, the surgeon inserts the endoscope 10 into the body, such as the ureter, of a patient C, inserts the sheath 3 into the body via the surgical-tool channel 10a together with the optical fiber 2 and the operation member 4, and disposes the vibration region 2b and the operation member 4 outside the endoscope 2. The space surrounding the vibration region 2b and the operation member 4 is filled with the liquid medium M.
Subsequently, the surgeon inputs a command to the laser irradiation device 1 by using, for example, an input unit (not shown), so as to cause the laser irradiation device 1 to execute the calibration in step S2 to step S10.
The calibration includes a first process (step S2 to step S6) for setting the pulse-group repetition frequency f1 and a second process (step S7 to step S10) for setting the pulse-group frequency f3 and the number of pulses.
As shown in
In the first process, the processor 8 causes the laser oscillator 5 to repeatedly generate the pulsed laser beam L, so that the pulsed laser beam L is repeatedly emitted from the distal end 2a of the optical fiber 2 (step S2). Moreover, the processor 8 changes the pulse frequency of the laser beam L in a continuous or stepwise fashion (step S3).
In step S2 and step S3, the distal end 2a vibrates synchronously with the pulse frequency of the laser beam L. The vibration amplitude of the distal end 2a reaches a maximum when the pulse frequency matches the resonance frequency of the vibration region 2b. The movement detector 6 detects movement including the vibration amplitude of the distal end 2a at each frequency (step S4).
The processor 8 determines that the pulse frequency corresponding to the maximum vibration amplitude is the resonance frequency of the vibration region 2b (step S5), and sets the pulse-group repetition frequency f1 to the resonance frequency (step S6).
Then, in the second process, the processor 8 changes the pulse-group frequency f3 and the number of pulses within a time period equivalent to half of the repetition cycle T1 in a state where the set repetition frequency f1 is fixed (step S7).
In step S7, the vibration amplitude of the distal end 2a changes along with the changes in the pulse-group frequency f3 and the number of pulses. The movement detector 6 detects the movement including the vibration amplitude of the distal end 2a at each pulse-group frequency and each number of pulses (step S8).
The processor 8 determines a combination of the pulse-group frequency and the number of pulses corresponding to the maximum vibration amplitude (step S9), and sets the pulse-group frequency f3 and the number of pulses in the pulse group in each of the first period I and the third period III to the determined pulse-group frequency f3 and the determined number of pulses (step S10).
As shown in
T2 denotes a time period from the start of emission of the first pulsed laser beam L to the start of emission of the last pulsed laser beam L in one pulse group. As shown in
The movement of the optical fiber 2 detected in step S4 and step S8 may be displayed on the display unit 20. For example, the display unit 20 may display a graph indicating the relationship between the pulse frequency and the vibration amplitude, or may display the determined resonance frequency. Moreover, the display unit 20 may display a graph indicating the relationship among the pulse-group frequency, the number of pulses, and the vibration amplitude.
Next, in step S11, the surgeon presses the foot switch 9 to irradiate the treatment target A with the laser beam L from the distal end 2a of the optical fiber 2, thereby performing a treatment on the treatment target A.
In step S11, the processor 8 controls the laser oscillator 5 to generate a pulse group having the frequencies f1 and f3 and the number of pulses set in step S6 and step S10. Accordingly, the distal end 2a vibrates at the repetition frequency f1, whereby the laser beam L is scanned.
In detail, during the first period I corresponding to the first half of the first repetition cycle T1, the pulse group is emitted from the distal end 2a, and the bubble B coming into contact with or close to the operation member 4 forms and contracts, which causes the distal end 2a to move closer toward the operation member 4. During the subsequent second period II, the distal end 2a moves away from the operation member 4, and the emission of the pulse group stops during that time.
During the third period III corresponding to the first half of the subsequent repetition cycle T1, the pulse group is emitted again from the distal end 2a, and the bubble B coming into contact with or close to the operation member 4 forms and contracts, which causes the distal end 2a to move closer toward the operation member 4. During the subsequent second period II, the distal end 2a moves away from the operation member 4, and the emission of the pulse group stops during that time.
Subsequently, the emission of the pulse group in the third period III and the stoppage of the pulse group in the second period II are alternately repeated.
Accordingly, the laser irradiation device 1 according to this embodiment utilizes the contraction force F of the bubble B generated at the distal end 2a of the optical fiber 2 as a driving force for vibrating the distal end 2a. The bubble B is generated by the treatment laser beam L emitted from the distal end 2a. Specifically, it is not necessary to add an actuator for driving the optical fiber 2 to the optical fiber 2. Thus, it is possible to reduce the diameter of a portion of the laser irradiation device 1 which is inserted into the body. Moreover, a function for scanning the laser beam L can be added to the laser irradiation device 1 without increasing the power consumption of the laser irradiation device 1.
In a case where an electromagnetic or piezoelectric actuator is used for vibrating the optical fiber 2, an electromagnetic field generated by the actuator may have an adverse effect on the endoscopic image. In this embodiment, the treatment laser beam L is an infrared beam, therefore an adverse effect on the endoscopic image can be prevented.
Furthermore, in order to crush a calculus efficiently, it is preferable that the scanning range of the laser beam L be wide. In this embodiment, the pulsed laser beam L is emitted from the distal end 2a only during the first period I and the third period III in which the optical fiber 2 moves closer toward the operation member 4, and the emission of the laser beam L is stopped during the second period II in which the optical fiber 2 moves away from the operation member 4. Accordingly, the contraction force F is prevented from being applied in a direction opposite the moving direction of the distal end 2a, that is, a direction that inhibits the vibration and thus causes the vibration amplitude to decrease, so that the distal end 2a can be vibrated efficiently by the contraction force F.
Supposing that the pulsed laser beam L is emitted from the distal end 2a during the second period II, the contraction force F acts on the distal end 2a in the direction opposite the moving direction of the optical fiber 2. Thus, the contraction force F acts as a braking force against the vibration of the optical fiber 2, thus inhibiting an increase in the amplitude.
Furthermore, in this embodiment, the pulsed laser beam L is emitted multiple times from the distal end 2a during the first period I and the third period III, and the bubble B forms and contrasts multiple times while the distal end 2a moves closer toward the operation member 4. Accordingly, the contraction force F acts multiple times on the distal end 2a, so that the vibration amplitude of the distal end 2a and the scanning range of the laser beam L can be increased. As a result, the treatment efficiency of the treatment target A can be enhanced, thereby increasing, for example, the crushing volume of the calculus.
Because the resonance frequency of the vibration region 2b varies between the air and the liquid medium M, it is difficult to accurately predict the resonance frequency of the vibration region 2b in the usage environment. Furthermore, in order to obtain a vibration amplitude of the distal end 2a required for scanning the laser beam L in the liquid medium M, it is important to cause the vibration region 2b to resonate by matching the pulse-group repetition frequency with the resonance frequency of the vibration region 2b.
According to this embodiment, the resonance frequency can be calibrated in a state where the vibration region 2b is disposed in the treatment environment, so that the resonance frequency of the vibration region 2b can be accurately measured in the treatment environment. Moreover, according to this embodiment, the pulse-group frequency f3 and the number of pulses are also calibrated in the state where the vibration region 2b is disposed in the treatment environment. Accordingly, during the treatment, the vibration amplitude of the distal end 2a and the irradiation range of the laser beam L can be maximized.
In the above embodiment, the optical fiber 2 and the operation member 4 are combined with each other by means of the sheath 3, and are inserted in the same surgical-tool channel 10a. However, the configuration of the optical fiber 2 and the operation member 4 is not limited to this, and may be modified, where appropriate.
In
In
In
In
In the modification in
In the above embodiment, the movement detector 6 detects the movement of the optical fiber 2 by using the vibration detection element 6a. Alternatively, the specific configuration of the movement detector 6 is not limited to this, and the movement may be detected by using other means.
In a modified embodiment, a movement detector 6 may detect, during the calibration, the movement based on an endoscopic image which is obtained by the endoscope 10 and which includes the distal end 2a.
In another modification, the movement detector 6 may supply another laser beam as a measurement beam together with the laser beam L for treatment to the optical fiber 2, and may detect the measurement beam reflected at the treatment target A and returning via the optical fiber 2. The intensity of the measurement beam changes with time in accordance with the vibration amplitude and the vibration frequency of the distal end 2a. The movement detector 6 can detect the movement of the optical fiber 2 based on the temporal change in the detected intensity of the measurement beam.
The present disclosure is advantageous in that a laser beam can be scanned in a liquid medium without having to add an actuator for driving an optical fiber to the optical fiber and without increasing the power consumption.
| Number | Date | Country | Kind |
|---|---|---|---|
| PCT/JP2021/009531 | Mar 2021 | WO | international |
This is a continuation of International Application PCT/JP2022/008752, with an international filing date of Mar. 2, 2022, which is hereby incorporated by reference herein in its entirety, and this application claims the benefit of priority to International Application PCT/JP2021/009531, filed Mar. 10, 2021, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2022/008752 | Mar 2022 | US |
| Child | 18242115 | US |
