Apparatus, method and system for a laser safety interlock for a catheter

Abstract

This patent application aims to teach an imaging device, method, and system for providing a laser safety interlock for at least one optical probe within the device. The interlock mechanism ensures that the laser is turned off when the optical probe is not spinning, thus suppressing laser beam hazards.

Description

Technical Field

[0001] Cross-reference to Related Patent Applications This application claims priority from U.S. Provisional Patent Application No. 63 / 388,145, filed with the United States Patent and Trademark Office on July 11, 2022, the disclosure of which is hereby incorporated by reference in its entirety.

[0002] The present disclosure generally relates to optical imaging devices, methods, and systems, and more particularly to a catheter that combines fluorescence and optical coherence tomography and includes an interlock system for restricting laser light generated by the imaging device to reduce the potential for damage.

Background Art

[0003] In optical coherence tomography (OCT), high-resolution cross-sectional imaging of tissue microstructure is provided in situ in real time, while in fluorescence imaging, visualization of molecular processes is possible. By integrating OCT and fluorescence imaging in a single catheter, co-localized anatomical and molecular information can be simultaneously obtained from a target tissue such as an arterial wall. For example, in "Ex.Vivo catheter-based imaging of coronary atherosclerosis using multimodality OCT and NIRAF excited at 633 nm" (Biomed Opt Express 2015, 6(4):1363-1375), Wang discloses an OCT-fluorescence imaging system that simultaneously uses He:Ne excitation light for fluorescence and a swept laser for OCT through an optical fiber probe.

[0004] In an optical imaging system, a patient interface unit (PIU) is used as an interface between a catheter and a system console. The PIU consists of an optical fiber rotary joint, a rotation motor, a translation motor, and a driver for the motors. To obtain cross-sectional images of tubes and cavities such as blood vessels, the esophagus, and the nasal cavity, an optical probe (accommodated in a catheter sheath) rotates with an optical fiber rotary joint (FORJ) by a rotation motor. Further, since the optical probe translates longitudinally by a translation motor simultaneously during rotation, an image with a helical scan pattern can be obtained. This translation is most commonly performed by pulling back the tip of the probe toward the proximal end, and thus is called pullback. In the system, since a laser beam is used to illuminate a sample such as tissue, improper use or exposure to laser light may cause permanent or temporary damage to the eyes, and means for controlling the laser is required to minimize unnecessary exposure.

[0005] For example, referring to European Patent No. 2698105 titled “Laser Interlock System for Medical Use” for Samsung Electronics Co., Ltd., an ultrasonic data acquisition unit (210) for acquiring ultrasonic data about an object is taught. The ultrasonic data acquisition unit includes an ultrasonic probe, a light source unit (220) that emits laser light, and a control unit (230) that turns the light source unit on or off according to the acquired ultrasonic data. The control unit is configured to determine whether contact has occurred between the object and the probe using the acquired ultrasonic data, and turn the light source unit on or off according to the determination.

[0006] The feature of the determination is that the control unit includes the following: an image generator that generates a two-dimensional (2D) ultrasonic image using the acquired ultrasonic data; a profile detector that detects the profile of an object from the 2D ultrasonic image; and a state determiner that calculates a profile difference by comparing the detected profile of the object with profile sample information corresponding to the object. The state determiner is configured to determine that contact has occurred between the object and the probe when the calculated profile difference is smaller than a preset threshold value. The control unit further includes a light source control unit, and the light source control unit turns on the light source unit when the state determiner determines that contact has occurred between the object and the probe.

[0007] However, this system has a drawback that the optical probe in the catheter spins while laser imaging is active in the normal state. In this case, the laser beam is irradiated only for a short time when directed at the eye. Under the two field-of-view conditions (difference in distance and aperture diameter) shown in Table 1, under normal conditions, the laser irradiation is significantly reduced by the spin of the optical power. However, such a significant reduction is not achieved when the optical probe is stationary (not rotating) during laser operation due to uncertainties in the laser / motor timing control or software defects. The two field-of-view conditions in Table 1 are: 1. the distance between the eye and the catheter laser is 2000 mm and the aperture is 50 mm, and 2. the distance is 100 mm and the aperture is 7 mm. As shown in Table 1, when the optical probe is spinning, the optical power to the aperture is reduced to 0.4% and 1.1% respectively compared to the optical power when the optical probe is stationary (not spinning and directed at the aperture). Under normal conditions, the laser irradiation is significantly reduced by the rotation of the optical power, but when the optical probe is stationary (not rotating) when the laser is on due to uncertainties in the laser / motor timing control or software defects, the reduction is slight.

Table 1

[0008] Accordingly, in view of the above problems, the present invention provides an apparatus, method and system for reducing the drawbacks of established technologies. SUMMARY OF THE INVENTION

[0009] This patent application aims to teach an apparatus, method and system for eliminating or significantly reducing laser irradiation in an optical probe.

[0010] In one embodiment, the present disclosure teaches an optical imaging apparatus comprising: an imaging engine having at least one laser source and a laser controller; a patient interface unit having a rotary motor, a rotary joint and a probe connection part; and a probe having an optical fiber for irradiating laser light from at least one laser source. The probe rotates by a rotary motor during imaging, and the laser light functions only during the rotation of the probe.

[0011] In an additional embodiment, the optical imaging apparatus further comprises an interlock circuit for controlling the functionality of the laser light.

[0012] In a further additional embodiment, the interlock circuit further comprises a frequency comparator for generating an on state and an off state of the laser light according to the rotation speed of the rotary motor. Furthermore, it is assumed that the interlock circuit is a redundant circuit. In this case, the redundant circuit includes two frequency comparators, one comparator is a positive comparator and the other comparator is a negative comparator.

[0013] In another embodiment, the laser light functions only when the probe rotates beyond a threshold value. Furthermore, the threshold value may be 1000 rotations per minute or more.

[0014] In yet another embodiment of the optical imaging apparatus, the rotary motor has an encoder for generating a spin signal for calculating the rotation speed. Furthermore, the spin signal from the encoder is 100 pulses or more per rotation.

[0015] In a further embodiment, the present disclosure teaches an optical imaging method comprising an optical imaging apparatus comprising: an imaging engine having at least one laser source and a laser control unit; a patient interface unit having a rotary motor, a rotary joint, and a probe connection part; and a probe having an optical fiber for irradiating laser light from at least one laser source. The probe rotates by a rotary motor during imaging, and the laser light functions only during rotation of the probe.

Brief Description of the Drawings

[0016] Further objects, features, and advantages of the present disclosure will become apparent from the following detailed description when interpreted in conjunction with the accompanying drawings showing exemplary embodiments of the invention.

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

[0018] Throughout the figures, unless otherwise specified, the same reference numbers and characters are used to indicate similar features, elements, components, or parts of the illustrated embodiments. Additionally, reference numerals including the designation “’” (e.g., 12’ or 24’) mean secondary elements and / or references of the same nature and / or type. Further, the present disclosure will be described in detail with reference to the figures hereinafter, which is made in relation to the exemplary embodiments. It is intended that changes and modifications can be made to the described embodiments without departing from the true scope and spirit of the present disclosure as defined by the appended paragraphs.

DETAILED DESCRIPTION OF THE INVENTION

[0019] Optical fiber catheters and endoscopes have been developed for accessing internal organs. For example, in cardiology, OCT (optical coherence tomography), white light backscattering, NIRS (near-infrared spectroscopy), and fluorescence techniques have been developed to observe the structure and / or molecular images of blood vessels using catheters. The catheter (having a sheath and an optical probe) is navigated into the coronary artery.

[0020] To obtain cross-sectional images of tubes and cavities such as blood vessels, esophagus, nasal cavity, etc., the optical probe rotates together with an optical fiber rotary joint (FORJ). Further, during rotation, the optical probe simultaneously translates longitudinally so that a helical scan pattern image can be obtained. This translation is most commonly performed by pulling back the tip of the probe towards the proximal end, and thus is called pullback.

[0021] In the first embodiment shown in FIGS. 1 and 2, imaging of the coronary artery by an exemplary intravascular OCT-fluorescence system will be described. In this embodiment, the system 10 provides a laser safety interlock to ensure that the laser is turned off when the optical probe is not spinning.

[0022] Describing the system overview in detail, the imaging system 10 includes a console 12, a PIU 14 (patient interface unit), and a catheter 16. The console 12 includes a host computer 18, imaging engines (OCT engine 20 and fluorescence engine 22), and a laser safety interlock circuit 24. The imaging engines 20, 22 house an OCT light source 26, a fluorescence laser source 50, and a control unit 62. The laser safety interlock circuit 24 supplies an interlock signal to the laser control unit 62 to turn on both lasers only when the rotary motor 58 in the PIU 14 is spinning. In the following sections, a detailed description of each component and their interactions will be explained.

[0023] OCT Engine Referring to FIG. 3, an OCT laser beam with a wavelength of approximately 1.3 μm is supplied from the OCT light source 26 and split by the splitter 32 into the reference arm 28 and the sample arm 30. In the reference arm 28, the reference beam 34 is reflected by the reference mirror 36. In the sample arm 30, the sample beam 38 passes through the PIU14 (Patient Interface Unit) and the catheter 16 and is reflected and / or scattered by the sample 40. The fibers of the PIU14 and the catheter are made of DCF (Double Clad Fiber). The OCT laser beam illuminates the sample 40 (outside the catheter) through the core of the DCF, the scattered light from the sample 40 is collected, sent back through the PIU14 to the circulator 42 of the OCT interferometer, and combined with the reference beam 34 at the combiner 44 to generate interference fringes. The output of the interferometer is detected using an OCT detector 46 such as a photodiode or a multi-array camera. Next, the signal is transferred to the processor 48, and signal processing is performed to generate an OCT image. The interference fringes are generated only when the optical path length of the sample arm matches the optical path length of the reference arm within the coherence length of the light source.

[0024] Fluorescence engine From the fluorescence light source 50, an excitation laser with a wavelength of 0.635 μm is supplied to the sample 40 (outside the catheter) through the PIU14 and the catheter 16. The Patient Interface Unit (PIU, detailed below) includes a free-space beam combiner so that the excitation light is coupled to the DCF common to OCT.

[0025] The excitation laser 26 and / or 50 illuminates the sample 40 from the distal end of the optical probe within the catheter 16. The sample 40 emits autofluorescence with a broadband wavelength of 0.65 - 0.90 μm. The autofluorescence is sent through the PIU14 to a fluorescence detector 52 such as a photomultiplier tube (PMT). Next, the analog electrical signal of the fluorescence detector 52 is collected by the data acquisition board (DAQ2) 54.

[0026] PIU (Patient Interface Unit) PIU14 is an interface between the catheter 16 and the console 12, and the PIU14 provides means for spinning and linearly translating the imaging core (optical probe) of the catheter within the outer sheath of the catheter. As can be seen in FIG. 4, the PIU14 includes a free space beam combiner, a FORJ56 (fiber optic rotary joint), a rotation motor 58, a translation motor 60, a linear stage 66, a motor driver / controller 62, and a catheter connector 64.

[0027] The FORJ56 (shown in more detail in FIG. 5) can transmit optical signals without interruption while rotating the double clad fiber shown on the left side along the fiber axis of FIG. 5. The FORJ56 has a free space optical beam coupler that separates the rotor 69 and the stator 68. The rotor 69 has a double clad fiber with a lens for creating a parallel beam. The rotor 69 is connected to the optical probe 16 and the stator 68 is connected to the optical subsystem.

[0028] The free space beam combiner 90 has a dichroic filter 92 that separates light of different wavelengths (OCT laser, excitation laser, and autofluorescence light). Also, the beam combiner includes a low pass filter or a band pass filter in front of the autofluorescence channel to remove the excitation light and minimize the excitation light noise at the fluorescence detector. The cut-off wavelength of the filter (low pass or band pass) is selected from approximately 645 - 700 nm.

[0029] The rotation motor 58 transmits torque to the rotor. Also, the translation motor 60 and the linear stage 66 are used for pullback, and the motor driver / controller 62 (hereinafter referred to as the controller or motor driver) drives both the rotation motor 58 and the translation motor 60. The encoder 67 is attached to the rotation motor 58, generates an encoder signal output for feedback with respect to the rotation motor 58, and provides a signal to the laser safety interlock circuit 24 to monitor the movement of the rotation motor 58.

[0030] Catheter The catheter 16 shown in FIG. 6 includes a sheath 70, a coil 72, a protector 76, and an optical probe 74. The catheter 16 is connected to the PIU 14. The optical probe 74 has an optical fiber connector, an optical fiber, and an optical distal lens 78. The optical fiber connector is used for physical engagement with the PIU 14. The optical fiber transmits light to the distal lens 78, and the distal lens 78 shapes the light beam to irradiate the sample 40 and efficiently collects the light from the sample 40.

[0031] The coil 72 delivers torque from the proximal end to the distal end by the rotation motor 58 of the PIU 14. There is a mirror at the distal end of the catheter so that the light beam is deflected outward. The coil 72 is fixed to the optical probe 74 so that the distal tip of the optical probe 74 also spins to observe the omnidirectional image of the inner surface of a hollow organ such as a blood vessel. The optical probe 74 has a fiber connector at the proximal end and a double-clad fiber and a distal lens 78 at the distal end. The fiber connector is connected to the PIU 14. The double-clad fiber is used to transmit and collect OCT light through the core and collect autofluorescence from the sample 40 through the cladding. The distal lens 78 is used to focus light on the sample and / or collect light from the sample. Since the size of the core is much smaller than that of the cladding, the scattered light passing through the cladding is relatively higher than the scattered light passing through the core.

[0032] Laser safety interlock The laser safety interlock circuit 24 supplies a laser safety interlock signal to the laser control unit 62. FIG. 7 shows in detail the high-level architecture related to the safety interlock circuit 24. The signal of the encoder 67 of the rotary motor 58 from the PIU is sent to the frequency comparators 82, 84 of the laser safety interlock circuit 24. The frequency comparators 82, 84 monitor digital signals and generate digital signals when the threshold is exceeded. Redundancy is added by the circuits of the two frequency comparators 82, 84 (frequency comparator P82, frequency comparator N84), and the fact that the two signals are logically opposite to each other helps to detect transmission problems between the laser safety interlock circuit 24 and the imaging laser control unit 62.

[0033] The signal output of the frequency comparator P82 is logic high when the rotational speed exceeds the threshold, and logic low otherwise. The signal output of the frequency comparator N84 is logic low when the rotational speed exceeds the threshold, and logic high otherwise. The two output signals from the frequency comparators are sent to a logic circuit and are generated only when the frequency comparators are in an active state. A truth table is shown in FIG. 7. Next, the interlock signal is sent to the laser control unit 62, and the laser control unit 62 shuts down the laser.

[0034] As an example, when the threshold is set to 1000 rpm, the maximum duration of laser irradiation for a 7 mm aperture at a distance of 100 mm is 60 / 1000×0.07 / 2π = 0.668 (milliseconds). Also, the response time is set to less than 0.250 milliseconds so that the circuit shuts down the laser immediately. Note that the response time is defined as the motor spin speed less than the threshold until the laser irradiation is shut down.

[0035] In the worst-case scenario, immediately after the duration of 1000 rpm, the rotary motor suddenly stops, and the time base becomes 0.668 + 0.250 = 0.918 milliseconds. The threshold and the response time are determined based on the optical power and the time base that the system can irradiate the laser beam. Generally, increasing the threshold and shortening the response time can minimize laser irradiation.

[0036] To represent the movement of the rotary motor, a hall sensor signal can be used instead of the encoder signal, thereby eliminating the need for the encoder 67 to realize the input of the laser safety interlock circuit and simplifying the rotary motor. However, since the encoder 67 generates a plurality of pulses per revolution (for example, 500 pulses per revolution), it helps to shorten the response time. The frequency comparators 82 and 84 require at least several pulses to determine the pulse frequency. When the threshold value is 1000 rpm, the pulse period is 60 milliseconds. When the encoder signal is 100 pulses per revolution, the pulse period is 0.60 milliseconds. When the signal of the encoder 67 exceeds 100 pulses per revolution, the time base becomes faster, which helps to minimize laser irradiation for the end user.

[0037] Frequency comparator Figure 8 illustrates a circuit for achieving a fast response time. The detected signal, that is, the digital pulse train from the PIU spin encoder, is applied to the B input of the retriggerable multivibrator U1. The output pulse width of U1 is set to a pulse period equal to the period of the desired trip frequency by the resistor R4 and the capacitor C2.

[0038] When the motor is not spinning, U1 is not triggered, its output is low, and the voltage of the capacitor C1 is zero. The outputs of U2 and U3 are low, and NIRAF does not operate. When the motor spins, U1 is triggered by each rising edge of the pulse train, and C1 is charged. When the pulse train frequency exceeds the minimum allowable frequency, C1 is charged to VCC. U2 trips at 1 / 2 VCC and activates the NIRAF laser. Since hysteresis is provided by the resistor R5, once triggered, it is necessary to lower the pulse train frequency to remove the enable signal to NIRAF. When the frequency of the pulse train drops to the set point, the voltage of the capacitor C1 drops to the trip point, the comparator goes low, and the NIRAF laser stops.

[0039] In another embodiment, when the motor spins, U1 is triggered by each rising edge of the pulse train. At the rising edge of the pulse train, the two flip - flops are also triggered. If the pulse period of U1 is smaller than the trigger frequency, the flip - flop clocks a logic 0 (before the U1 output goes from low to high), and the laser is stopped. When the pulse train frequency exceeds the minimum allowable frequency, U1 is triggered again and the output goes high continuously. At the next rising edge of the pulse train, logic 1 is clocked into U2A, and at the second rising edge of the pulse train, logic 1 is clocked into U2B, and the laser is activated.

Claims

1. An imaging engine having at least one laser source and a control unit for controlling the laser source, A patient interface unit having a rotary motor, a rotary joint and a probe connection part, A probe having an optical fiber for irradiating laser light from the at least one laser source, An optical imaging device comprising: The probe rotates by the rotary motor during imaging, The laser light functions only during the rotation of the probe, Device.

2. The device according to claim 1, further comprising an interlock circuit for controlling the functionality of the laser light. The device according to claim 1.

3. The device according to claim 2, wherein the interlock circuit further comprises a frequency comparator for generating an on state and an off state of the laser light according to the rotation speed of the rotary motor. The device according to claim 2.

4. The device according to claim 2, wherein the interlock circuit is a redundant circuit.

5. The redundant circuit includes two frequency comparators, One comparator is a positive comparator and the other comparator is a negative comparator, The device according to claim 4.

6. The laser light functions only when the probe rotates beyond a threshold value, The device according to claim 1.

7. The device according to claim 4, wherein the threshold value is 1000 rotations per minute or more.

8. The device according to claim 1, wherein the rotary motor has an encoder for generating a spin signal for calculating a rotation speed. The device according to claim 1.

9. The spin signal from the encoder is 100 pulses or more per rotation, The device according to claim 8.

10. A method of operating an optical imaging device, The optical imaging device, An imaging engine having at least one laser source and a control unit for controlling the laser source, A patient interface unit having a rotary motor, a rotary joint and a probe connection part, A probe having an optical fiber for irradiating laser light from the at least one laser source, Comprising: The method includes: Rotating the probe by the rotary motor; Irradiating the laser light during the rotation of the probe to capture an image; Stopping the laser light when a disturbance of the probe occurs. A method comprising.

11. The method according to claim 10, further comprising an interlock circuit for controlling the functionality of the laser light. The method according to claim 10.

12. When a frequency comparator that generates the on-state and off-state of the laser beam according to the rotational speed of the rotary motor reaches or exceeds a threshold value, the disturbance of the probe occurs. The method according to claim 10.

13. The method according to claim 11, wherein the interlock circuit is a redundant circuit.

14. The redundant circuit includes two frequency comparators. One comparator is a positive-side comparator and the other comparator is a negative-side comparator. The method according to claim 13.

15. The laser beam functions only when the probe rotates beyond a threshold value. The method according to claim 10.

16. The threshold value is 1000 rotations per minute or more. The method according to claim 13.

17. The method according to claim 10, further including the step of an encoder of the rotary motor generating a spin signal for calculating a rotational speed. The method according to claim 10.

18. The spin signal from the encoder is 100 pulses or more per rotation. The method according to claim 17.

Images