CN114848139A

CN114848139A - 2940 nmEr: YAG laser blood vessel plaque ablation instrument

Info

Publication number: CN114848139A
Application number: CN202110107310.3A
Authority: CN
Inventors: 杜金波
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-01-27
Filing date: 2021-01-27
Publication date: 2022-08-05

Abstract

The invention relates to a therapeutic apparatus for cardiovascular plaque ablation. By using Er: the 2940nm laser emitted by YAG can be absorbed by the water-containing biological tissue strongly, and the cardiovascular plaque is vaporized to replace the heavy and expensive imported xenon chloride excimer laser which is adopted clinically at present. Greatly reduces the medical burden of nearly one hundred million patients with cardiovascular and limb angiostenosis in China, and can also greatly reduce the medical insurance expenditure of China. Preventing us from seizing our neck on critical medical devices.

Description

2940 nmEr: YAG laser blood vessel plaque ablation instrument

Technical Field

The invention relates to a light-based medical instrument, in particular to an er laser 2940nm used for a cardiovascular plaque ablation instrument, and belongs to the technical field of surgical instruments, devices or methods for transferring energy in a non-mechanical form to or from a human body in International patent Classification A61B 18/00'.

Background

Atheromatous plaque deposited in coronary arteries severely blocks the blood flow in the heart vessels, causing myocardial ischemia, angina and even myocardial infarction. At present, cardiovascular diseases become the leading cause of death of urban and rural residents in China, and the latest statistical data shows that the cardiovascular diseases account for 44.8 percent of the cause of death of rural residents and 41.9 percent of the cause of death of urban residents, and are ranked first. It is a serious disease that is more dangerous to human health than cancer. According to the data on the network, more than 4000 million cardiovascular patients exist in China, and if the patients are added with carotid plaque and lower limb angiostenosis, the number of patients is nearly hundreds of millions. This figure has also risen with the increase in the standard of living of people.

One of the current approaches to treating cardiovascular stenosis is to bypass a severely occluded segment of blood vessel with a good blood vessel, either artificial or cut elsewhere, called a cardiovascular bypass. This requires a large open chest procedure. Another method is to pass a catheter with an inflatable balloon at the most anterior end through the vessel to the stenosed site of the plaque, and then inflate the catheter to dilate the stenosed vessel, even placing a stent in the stenosed site, to prevent the plaque from retracting. As shown in figure 1.

However, this approach is not suitable for many patients, for example, where the balloon is unable to enter or expand due to improper plaque location and vessel shape, or due to severe occlusion or plaque hardening. Especially in the coronary arteries, and once the thrombus has entered other parts of the vessel it can cause new blockages, especially into the cerebral vessels, which is more dangerous. Since the plaque is not removed, even with so-called drug stents, the formation of new stenosis is only delayed. Thus, it has been invented to apply laser light to the plaque through an optical fiber to ablate the plaque by vaporization. Particles after ablation by vaporization are generally smaller than 10 microns, and the possibility of causing new blood vessel blockage is very low ⁽⁷⁾ . The laser commonly accepted at home and abroad for plaque ablation is XeCl (xenon chloride) excimer laser. Chlorine is the chlorine in common salt, sodium chloride, and xenon is an inert gas. They are normally not combined together. However, under the condition of high-voltage discharge, the two ions are ionized to form xenon chloride excimer temporarily. They are called excimer molecules because they will automatically break apart quickly, returning to an atomic state. When they separate, laser light is emitted. The wavelength of the emitted laser light was 308 nm. The shortest wavelength that we can see to the human eye is about 430 nanometers. 308 nanometers belongs to ultraviolet light not visible to the human eye. The energy of single photon is very high, which can open the valence bonds of organic protein and nucleic acid, thus can ablate the atheromatous plaque. This is often referred to as photochemistry. However, the excimer laser has high manufacturing difficulty and unstable output, and due to volatilization of the high-voltage discharge electrode material, the gas purity is reduced, and the output energy is reduced, so that the excimer laser needs to be replaced by new chlorine and xenon. The devices made in China are not up to now closed, and one device needs nearly ten million yuan RMB from foreign import. The cost is high for foreign personnel to repair. According to the online report, the treatment of the cardiovascular plaque by the excimer laser ablation is only carried out in Beijing Anzhen Hospital, Beijing three hospitals, Fuweizhou Hospital, Xuanwu Hospital and Qinghua ChangG Hospital. At present, more than 4000 million cardiovascular patients exist in China, if expensive equipment imported from abroad is adopted, foreign exchange of astronomical numbers is needed, and the common people need to use the expensive equipmentThe cost of medical treatment is huge, and the nation also needs huge medical insurance expenses. The situation that such high-end medical devices rely on importation is to the time when it must be changed!

In the last 80-90 s, there were two parallel directions when looking for lasers to ablate cardiovascular plaques abroad: an ultraviolet-emitting excimer laser such as xenon chloride; another class is the use of water-absorbing mid-infrared lasers. Such as a holmium laser, at a wavelength of 2100 nm; er laser, wavelength 2940 nm. Because all biological tissues, including enamel and dentin, and all bones contain water, atheromatous plaque and even calcified hard plaque contain large amounts of water. After absorbing the mid-infrared laser, the water heats and vaporizes to melt the plaque. Since ultraviolet laser light can be transmitted through the well-established quartz optical fiber in the past 80-90 years, er laser 2940nm cannot transmit the quartz optical fiber at all, most of the er laser light is holmium laser light in the off-body test and the clinical test in the year. In a report of 1996, a total of 120 patients, 129 with plaque stenosis, including some patients with thrombus (not suitable for balloon dilatation), were successfully ablated with holmium laser. Holmium laser can also pass through a quartz optical fiber, but reaches the edge of a transmission curve, and the loss is large. In addition, the absorption coefficient of water to 2100nm is low, the pulse width is hundreds of microseconds, and the damage to surrounding normal tissues is large, so that the excimer laser occupies the upwind in the later clinical competition.

Disclosure of Invention

1. The method is carried out by using solid Er: fast ablation of vascular plaques by YAG 2940nm laser instead of 308nm xenon chloride excimer laser

We wanted to develop er lases. One reason is the development of mid-infrared optical fibers due to the need for mid-infrared communications. Today, 2940nm fluoride and sulfide glass optical fiber (ZLBAN) and white gem optical fiber which can transmit 2940,2780nm energy more than 1 j/pulse and continuous power more than 100w, transmittance per meter more than 96% are available in commercial products at home and abroad. This provides a good premise for ablating cardiovascular plaques with 2940nm er laser.

In principle, laser light entersAfter the biological tissue, the biological tissue does not travel straight as in air, but is absorbed and scattered by the tissue. Acting with biological tissues, three major factors are mainly determined: the absorption coefficient of the tissue for the laser light of the wavelength used is alpha (cm-1). The stronger the absorption, the faster the laser decays after entering the tissue, and the shallower the penetration. Another major factor is the laser action time, which for pulsed laser is the laser pulse width Δ τ. The narrower the pulse width, the shorter the action time, and the shallower the penetration. Thirdly, the area of the laser pulse point of action is divided by the pulse energy, i.e. the energy density (J/cm) ² ). The energy density is divided by the pulse width, which is the power density of the laser. FIG. 2 shows the absorption coefficient, penetration depth and wavelength of pure water at 20 ℃. Table 1 shows the absorption coefficient values of water and water-containing biological tissue for different wavelengths of laser light.

From Table 1, it can be seen that the hydrous biological tissue is paired with CO ₂ (10.6 μm) to Er: the absorption in the mid-infrared band of YLF (er-doped lithium yttrium fluoride, wavelength 1.73 μm) is mainly due to the absorption of water in biological tissues. Due to Er: the YAG has a wavelength of 2.94 microns near the absorption peak of water, so that the absorption coefficient is as high as 2700cm ^-1 The highest value of (c). From Nd: YAG from 1.06 μm to argon laser, in the near infrared and visible light bands, water is substantially transparent to visible light except for specific chromophores in biological tissue such as heme, hemocyanin derivatives, and thus the absorption of biological tissue is low. However, in the ultraviolet band emitted by excimer laser after XeF and XeCl, the absorption coefficient is increased because the bonding of organic molecules such as protein and nucleic acid can be destroyed by ultraviolet high-energy photons. From Table 1, Er: YAG, Ho: the absorption coefficients of YAG and XeCl are 2700, 35 and 200 (cm) respectively ^-1 ). In the last 80-90 s, most of the externally published mid-infrared lasers used as holmium lasers for plaque ablation. The use of an er laser (which at that time could not be transmitted using a quartz fiber) would be significantly better than a holmium laser because the absorption coefficient of the tissue for 2940nm is 77 times greater than 2100nm and 13.5 times greater than XeCl 308 nm. Smaller energies may be used to control a smaller range of peripheral thermal damage. The safety is better. A large number of Er: YAG, 2940nm laser, Ho: YAG 2100nm laser ablation of bone, skin, artery, cornea, sclera and intraocular lensCompared with various data, er laser is far lower than a holmium laser ablation threshold value, efficiency is high, and secondary damage to the periphery is small. Compared with the currently clinically used 308nm excimer laser, the ablation efficiency of the atheroma is improved by at least 5 to 10 times.

2. With a Q-switch Er: YAG laser replacing long pulse width free oscillation laser

The second is the effect of the laser pulse width. Er: YAG laser operation generally has two modes: the free-running mode consists of a series of individual spikes of about 1 microsecond duration, the total width of which is determined by the pumping width of the xenon discharge, typically in the range of 70-250 microseconds (see fig. 3). The other is a Q-switch mode, which outputs a single pulse (1 microsecond-10) with a pulse width of tens to one hundred and nanoseconds ^-6 Second, 1 ns 10 ^-9 Seconds), (see fig. 4).

The laser is hit in the air through a focusing lens or through a transmission optical fiber

On atheromatous plaque or normal vessel walls in saline or blood, these tissues absorb the laser light, which converts the laser energy into heat, raising the temperature of the point of action with the concomitant generation of acoustic pressure waves (ultrasound oscillations). At the same time, the light waves, and thus the heat, are also transmitted deep into the tissue. If the tissue absorption coefficient is large and the laser pulse time is short, the tissue at the action point is rapidly heated and vaporized. Plaque ablation is limited to a small extent and damage to deep tissue is limited. On the contrary, the tissue has small absorption coefficient to light, the laser action time is long, the temperature rise at the light irradiation point is slow, and the heat diffusion to the deep layer is increased. It follows that laser pulse width plays an important role in plaque ablation.

Despite the strong absorption of water, with a free-running 2940nm laser, typically containing a series of oscillation spikes at 200 microseconds, under low energy density (< 25j/cm2), the laser-tissue interaction is mainly vaporization. The depth of thermal damage around the vaporization pit can be controlled to be below 10-20 microns. However, at high energy density (80j/cm2), the vaporization of the lower layer generates a large pressure due to the increased depth, but does not evaporate as quickly as the surface layer into the low pressure space, thus generating heat and mechanical expansion around, resulting in micro-blasting. The depth of thermal damage can even reach > 100 microns due to vaporization pressure. To reduce the depth of thermal damage to surrounding tissue caused by ablation of the er laser, the laser pulse width, i.e., the laser application time, must be reduced to within the thermal relaxation time of the vascular wall tissue (about 1 microsecond). Therefore, the Q-switch am laser is adopted to be a narrow pulse (less than 1 microsecond) of tens to hundreds of nanoseconds, so that the damage depth of 2940nm laser is easily controlled to be less than 5-10 microns, and the safety of the blood vessel wall is ensured. But this is not to say that the narrower the laser pulse width the better. With the narrowing of the pulse width, the peak power density is correspondingly improved, firstly, the damage of the transmission optical fiber is easily caused, and simultaneously, the ablation of the plaque generates stronger micro-blasting and even plasma ignition and is accompanied by shock waves, thereby causing discomfort and even vasospasm in the operation process of a patient, and the mechanical impact enlarges stripped fragments and is easy to cause new blockage. Damage to surrounding normal tissue may also increase. Table 2 shows the theoretical parameters for effective ablation of atheroma with different wavelengths.

3.2940 nmQ switching the laser element, one way is to use a normal incidence, antireflection coated approach, which facilitates the laser mounting and tuning, as shown in fig. 5. However, the prior 2940nm coating technology in China is not over-closed, and a film layer with slightly larger energy is easy to damage. Therefore, the Brinell angle incident Q-switch is adopted, and the antireflection film does not need to be plated on the surface. Avoid the destruction of 2940nm film layer. As shown in fig. 6.

4. Using lasers with high repetition rate (> 20Hz) and power density not too great above the ablation threshold to increase ablation rate and ensure safety of the vessel wall

Of course the main problem considered above is to reduce the thermal damage of the ablated plaque to the surrounding normal tissue. Thereby ensuring the safety of the vessel wall. By reducing the pulse width, the energy density is reduced. The energy density of the ablation is reduced but still kept at a level not too high above the ablation threshold (which will leave the ablated material mostly in a vaporized state, avoiding new occlusions due to larger particles). This, of course, reduces the speed of ablation, making the procedure undesirably long. This can be compensated by a suitable increase in the laser pulse repetition rate. Even if the repetition rate reaches 100Hz, the interval between the front pulse and the rear pulse still has the thermal relaxation time of 10ms. which is far larger than the plaque by 1 microsecond, the heat accumulation can not be caused, and the thermal injury range can still be kept at a safe level. In addition, at the beginning of ablation, the plaque layer is thicker and the energy density used can be suitably increased. Along with the gradual thinning of the plaque, the laser energy density and the repetition rate are correspondingly reduced, which can be realized by an artificial intelligence method. The inverse 308nm excimer laser is mainly based on the absorption of protein and nucleic acid to ultraviolet laser. These high-energy UV laser photons can disrupt the bonding of organic molecules, but are also accompanied by thermal and mechanical shock destruction, otherwise plaque material is not removed! According to the report of Zhouyijdoctor, the wavelength adopted in the operation is about 308nm, and the effect of improving coronary blood flow is achieved by emitting high-energy pulses, breaking chemical bonds caused by very high energy density and short action time, releasing energy, vaporizing liquid water in cells to generate steam bubbles, leading to the disintegration of tissues through rapid expansion and contraction, and vaporizing obstructive atheromatous plaque substances. It can be seen that the uv laser and the mid-ir laser are in communication in the mechanism of plaque removal. It cannot be said that the excimer laser is a "cold laser", and the mid-infrared laser is a "hot laser", which is not scientific. The key issue is that ensuring the safety of the vessel wall is available with an acceptable ablation rate!

The 5.2940nm laser and the detection beam are transmitted by ZBLAN optical fiber or white gem optical fiber, and the core diameter is 100-200 microns. Can transmit laser light of 0.35-5 microns. X-ray angiography monitoring is adopted in the initial stage, and the photoacoustic endoscopic imaging technology is further adopted after the technology is mature to ensure effective plaque ablation and safety of the blood vessel wall. At present, the clinical intravascular plaque interventional therapy adopts X-ray angiography monitoring and is characterized by being simple, convenient and easy to implement. Photoacoustic endoscopic imaging technology is further developed. Ultrasonic signals generated by laser irradiated on a blood vessel wall are converted into electric signals by a probe at the front end of the catheter and then transmitted to an external screen for distinguishing the blood vessel wall, particularly the shape, components and vulnerability of plaque, and the efficiency of laser ablation and the safety of the blood vessel wall are ensured.

6. The invention uses solid laser to replace bulky gas laser. The volume is greatly reduced. Easy to move and convenient to use. The cost is estimated to be one tenth of the imported therapy machines. Can be widely popularized in China and also can be exported.

Detailed description of the invention

1. Two Q-switch schemes of lithium niobate electro-luminescence and frustrated total internal reflection are adopted. Narrow pulses with nanosecond pulse width are obtained, the pulse width is widened to 100-1000 nanosecond width, vaporization of stripped plaque or particles smaller than 10 micrometers is guaranteed, and re-blockage of blood vessels is prevented. And also ensures that the safety of the transmission optical fiber is not damaged. A specific method of broadening the pulses is described in my laser lithotripsy invention patent.

2. In order to make the device and adjustment simple and convenient, all optical elements adopt vertical incidence, and the incidence surface is plated with a 2940nm antireflection film. As shown in fig. 5. In view of the fact that the current domestic 2940nm coating technology is not relevant, a Brinell angle incident Q switch scheme is designed. As shown in fig. 6.

3. Due to Er: YAG crystal pair adjusting Nd: the 630nm red light used by YAG indicates that the light is not transparent, and the indicating light of the 2940nm laser is adjusted to be changed into a orange-yellow laser diode laser with the wavelength of 561 nm.

4. In order to obtain 2940nm laser output with high repetition rate, Er: the YAG bar hot-focusing and annealing effects design the use of 5 laser diode bars surrounding pump Er: the YAG rod scheme greatly reduces Er: the YAG rod has heat focusing effect, high output efficiency and long service life of lamp pump, and the laser diode pump has long service life of ten thousand hours.

The 5.2940nm therapeutic light and the diagnostic monitoring light are transmitted by ZBLAN optical fiber or white gem optical fiber, and the core diameter is 100-200 microns. It comprises ZrF ₄ (zirconium fluoride), BaF ₂ (barium fluoride), LaF ₂ (lanthanum fluoride), AlF ₂ (aluminium fluoride), NaF (sodium fluoride) several materials mix the glass-fiber of making. Can transmit 2940,2780nm energy more than 1 j/pulse and continuous power more than 100 w/meterThe transmittance is more than 96%, and the product is sold at home and abroad (imported from Japan at home at present).

6. The 308nm laser of xenon chloride excimer is ineffective to harden plaque, the clinical ablation harden plaque at present adopts the drill bit with diamond powder on the periphery to grind, the 2940nm laser utilizes the moisture absorption in the tissue, the heater gasification, produces the micro-blasting ablation tissue, even the hardest enamel, the dentin can be ablated, the hardened plaque does not have the problem at all to the 2940nm laser ablation.

7. The invention uses solid laser to replace bulky gas laser. The volume is greatly reduced. Easy to move and convenient to use. The cost is estimated to be one tenth of the imported therapy machines. Can be widely popularized in China and also can be exported.

Drawings

Figure 1. balloon dilatation or stenting of a vessel narrowed by plaque.

FIG. 2.20 ℃ absorption coefficient of pure water, penetration depth, as a function of laser wavelength.

FIG. 3. Er: YAG free-running laser waveform.

FIG. 4. Er: YAG Q switched laser waveforms.

FIG. 5. vertical incidence lithium niobate electro-optical Q-switch Er: YAG laser.

Figure 6 a buchner angle electro-optic Q-switched laser.

Figure 7. a berkovich angle frustrated total internal reflection Q-switched laser.

FIG. 8 is a table 1 showing absorption coefficient values of water and water-containing biological tissues for laser light of different wavelengths;

table 2. theoretical parameters for effective ablation of atheromatous plaque with lasers of different wavelengths.

Claims

1. The invention relates to a novel laser light source and a method for ablating vascular plaques, wherein the working substances are Er: YAG laser crystal. Er doping density is 50%. The output wavelength was 2940 nm. The output laser energy is 30-400mj/pulse, the pulse width is 50ns-250 mu s, the repetition rate is 1-40Hz., the low repetition rate adopts a pulse xenon lamp for pumping, and the high repetition rate adopts a laser diode bar for pumping.

2. According to claim 1, the laser operates in Q-switch mode for pulse widths less than 2 μ s and in non-Q-switch mode for pulses at 20 μ s, depending on the treatment requirements.

3. In order to improve the efficiency of the lamp pump, the laser power supply adopts a square wave discharging mode of IGBT discharging.

4, Er: YAG laser Q switch adopts lithium niobate electro-optical Q switch mode or frustrated total internal reflection Q switch, is decided by the optimization of ablation plaque to parameters such as laser pulse width, pulse energy, repetition rate.

The 5.2940nm laser was transmitted using a ZBLAN fiber or a sapphire fiber with a core of 100,200 μm.

The heart catheter with the guide wire performs the specific operation of plaque ablation.

6. The monitoring of ablation plaque was early monitored using X-ray angiography. And replacing the photoacoustic endoscopic imaging technology after the photoacoustic endoscopic imaging technology is mature.

The 7.2940nm laser energy density and repetition rate are automatically controlled by an artificial intelligence method according to the progress of the plaque ablation, and are reduced in batches from high to low so as to ensure the effectiveness of the plaque ablation and the safety of the blood vessel wall.