Method, device and method of use of the device for coagulating varicose veins by high intensity focused ultrasound

Abstract

A method and apparatus for treating blood vessels are disclosed. In particular, the invention is directed to a method of occluding varicose veins while avoiding the formation of bubble clouds in the tissue surrounding the blood vessels and / or the interaction of bubble clouds with ultrasound beams. The invention is also directed to an apparatus adapted to perform the method.

Description

Technical Field

[0001] The present invention relates to a method, apparatus, and method of using the apparatus for treating blood vessels, particularly varicose veins, by high-intensity focused ultrasound (HIFU) according to the features of the independent patent claims. Background Technology

[0002] Heat therapy is known to be used to occlude veins, for example, in the treatment of varicose veins.

[0003] US8,214,052 discloses an invasive method for treating a vein using a catheter capable of delivering heat to the vein wall. The catheter is placed within the vein segment to be treated, radiofrequency energy is applied to heat the vein wall, and then the catheter is withdrawn from the vein.

[0004] The main drawback of this method is that a catheter must be invasively inserted into the segment of vein to be treated, which carries the risk of perforation, and it is a complicated procedure for tortuous veins.

[0005] HIFU devices allow for non-invasive treatment of targets within a patient's body. To focus the HIFU device on the target area, imaging of the area surrounding the target area is performed, for example, by MRI, ultrasound, CT, or optical imaging. In particular, HIFU devices with integrated mode-B ultrasound imaging are used, as exemplarily described in WO 2006 / 129045 A2.

[0006] Mechanical or thermal effects have been described as potential mechanisms for intravenous HIFU treatment. Mechanical effects rely on causing damage to the vascular endothelium to promote thrombus formation and subsequently lead to occlusion. This approach has not yet been proven effective without adjuvant medication (Hwang et al., 2005, 2006, 2010; Zhou et al., 2011).

[0007] Thermal effects can also damage the endothelium, and are more effective because the damage can extend to other layers of the vein wall (media, adventitia) and the thermal denaturation of collagen produces beneficial luminal contraction. Other thermal methods (laser, radiofrequency) are now widely accepted.

[0008] HIFU thermal ablation is most effective when blood flow is reduced to a minimum to avoid heat sink effect.

[0009] Hynynen et al. described a combination of mechanical and thermal effects in 1996, in which mechanical action was used to induce vasospasm, thereby stopping blood flow and placing the blood vessels in a configuration favorable to subsequent thermal pulses.

[0010] Hynynen et al. further described the characteristics of the focal spot, noting that the half-intensity beam diameter and length were 1.0 mm and 4.8 mm, respectively. The target diameter was described as approximately 0.6 mm, measured from X-ray angiography. Hynynen et al. also disclosed the idea of ​​intentionally damaging the tissue surrounding the blood vessel to occlude it.

[0011] In the following text, "pulse" refers to the delivery of ultrasound energy into tissue, specifically for the purpose of achieving a therapeutic effect in said tissue, while "site" refers to the central location of the focal spot during the pulse. "Above" the structure refers to the space between the structure and the HIFU transducer, and "below" is defined accordingly. Therefore, the "top" or "surface" portion of the structure refers to the structural portion closer to the HIFU transducer.

[0012] Hynynen et al. described a treatment plan in 1996 in which pulses were delivered at multiple locations forming a square of 4x4 sites centered on veins in a transverse plane.

[0013] In practice, the position of each site relative to the vein is crucial. In fact, if a pulse causes cavitation or boiling in the tissue located between the transducer and the vein, the bubble cloud will act as a strong reflector for subsequent pulses delivered at or near the current site, thereby causing damage to gradually increase in front of the focal plane. Summary of the Invention

[0014] Therefore, the object of the present invention is to overcome the shortcomings of the prior art and to provide an improved method for HIFU treatment of a hollow structure comprising walls and fluid in an uncompressed state, such as a blood vessel, and in particular to provide a treatment method that avoids damage outside the target area and ensures proper formation of damage within the target area.

[0015] The method and apparatus according to the independent claims of the present invention achieve this and other objectives.

[0016] The method according to the invention is for treating hollow targets with a HIFU beam having a focal spot. The focal spot, in particular, the center of the focal spot, is located at a position that is farther (especially deeper) than the target depth indicating the target location or tangential to the target depth, in order to avoid or limit the generation of bubbles, in particular bubble clouds, in the tissue located between the treatment head and the target during pulse emission.

[0017] In a particularly preferred embodiment, the HIFU beam is directed such that the center of the focal spot and / or the point of maximum intensity of the sound field is located at a position at least tangent to or deeper than the target.

[0018] Preferably, the center of the focal spot and / or the point of maximum intensity of the sound field, as referred to herein, is measured in water as a reference.

[0019] A position deeper than the target can be understood as a position along the axis extending from the treatment head or transducer to the target that is closer to the target than the treatment head / transducer, but not between the treatment head / transducer and the target.

[0020] Target depth is generally understood as the location or orientation of a target (e.g., the wall of a vein). However, a target may have a non-negligible thickness relative to its focal spot size. In such cases, target depth should be understood as any depth within the target such that the target depth represents the target. For example, if the target is a vein, the target level could be defined as the center of the vein, or the upper or lower boundary of the vein wall.

[0021] The distance relative to the target depth can be selected to avoid or limit the formation of bubble clouds in the tissue located between the target and the treatment head. In particular, the difference relative to the target depth can be included in the range of 0 to 16 mm, preferably 0 to 12 mm, and especially preferably 0 to 8 mm. If cavitation and / or boiling are used as the basic mechanism for damage formation, this will generate a bubble cloud a few millimeters above the foci.

[0022] Limiting bubble formation can specifically mean that the bubble formed by the first pulse does not interfere with the second and subsequent pulses. For example, if a pulse is provided at a lateral distance of 3 mm, the first pulse provided at a first position may cause bubble formation. If the size and position of the bubble formed by the first pulse are set such that the next HIFU pulse provided at a second position 3 mm from the first position is not reflected by the bubble cloud, then the bubble formation of the first pulse may have been sufficiently limited.

[0023] Therefore, this range is particularly preferred to be 2 to 8 mm. Where boiling and / or cavitation are not particularly significant, this range is particularly preferred to be 0 to 2 mm.

[0024] Alternatively and / or additionally, the difference relative to the target depth includes the range of 10% to 200% of the focal length, preferably 20% to 100% of the focal length, and most preferably 30% to 70% of the focal length.

[0025] For example, a practical implementation could include setting the focal point such that the surface boundary of the focal spot is tangent to the surface boundary of the vein wall. Thus, the distance could be:

[0026] The distance from the top of the fovea to the top of the vein wall is 0 mm.

[0027] The distance from the center of the apothecia to the top of the vein wall is approximately half the size of the apothecia, typically 1 to 4 millimeters.

[0028] These values ​​may vary depending on the target depth (top of the vein, middle of the vein, etc.) and the definition of the focal spot.

[0029] In addition, additional safety margins may be included. For example, this safety margin may be defined based on prior experiments that quantify the variability of damage size or the variability of hyperechoic marker size and / or other factors. In this case, a reliability interval may be used to set the safety margin. For example, if the standard deviation of the HEM dimension above the focal point is 1 mm, the additional safety margin for this value may be included in the distance between the target depth and the focal point.

[0030] The target, in its uncompressed state, includes the wall and the liquid.

[0031] In particular, the present invention provides a method for appropriately positioning the site relative to the target in a manner that enables the formation of air bubbles in the tissue located between the transducer and the vein to be avoided or limited.

[0032] If a bubble cloud is generated in soft tissue, the bubbles will be trapped within the tissue, and the bubble cloud will then act as a strong reflector for several seconds. In contrast, this method relies on the fact that bubbles generated in fluids (such as blood) after and during HIFU will be rapidly removed. This may occur due to dissolution, scouring, radiation, or buoyancy. The nucleus may still be partially present in the next pulse, but it is minimized due to the aforementioned effects. Bubbles can be removed by positioning the site in an area containing a liquid such as blood. Inducing bubbles in tissue below the target is harmless, and may even be beneficial because a bubble cloud below the target can both shield the underlying tissue and reflect some energy back to the target.

[0033] These areas can be set according to specific standards. The standard is explained below regarding "focal spot". Focal spot is generally understood as an area with an intensity greater than the maximum intensity -6dB.

[0034] However, these criteria can also be applied to other limitations, and in the following, in particular assuming the absence of interaction between the beam and pre-existing bubbles (in which case cavitation or boiling may occur in the tissue under the treatment conditions (power, pulse duration, etc.)), the expression "focal spot" should be understood as the area surrounding the point of maximum intensity of the sound field. These concepts can refer to actual areas (e.g., actual -6 dB focal spots in tissue), or estimations based on measurements in a test environment (especially in water), geometry-based calculations, simulations, experiments, etc. As is known to those skilled in the art, bubble clouds can grow significantly above the focal spot, resulting in what is commonly referred to as "tadpole-shaped lesions," and sometimes significant bubble activity can be detected primarily above the focal spot.

[0035] If the target is compressible, the method of the present invention is more effective when the target does not collapse or only partially collapses. If the target is a vein, it is preferably partially collapsed. However, these methods are also applicable when the target completely collapses. In this case, there is no fluid inside the target, but to avoid the target being obscured by a cloud of bubbles, the pulse is preferably provided below the target.

[0036] The "top" of the focal spot (located near the transducer boundary) can be tangent to the upper boundary of the target (closer to the transducer boundary).

[0037] In a preferred embodiment, the target depth is the depth of the surface portion of the target wall.

[0038] In another preferred embodiment, the target depth is therefore the depth of the target wall portion located away from the center of the treatment head or target lumen.

[0039] Preferably, a safety margin is added in the distance between the focal spot and the target depth.

[0040] For example, the top of the foil can be positioned below the lower boundary of the target. This is particularly concerning when the pulse causes cavitation or boiling before it ends. In this case, reflections caused by the bubble cloud present at the foil can lead to intense pre-foil thermal deposition during the pulse, which can cause undesirable cavitation or boiling above the target, especially when the foil is too high.

[0041] Preferably, an additional safety margin is considered for the variability in tissue characteristics. In this case, the top of the focal spot is located at a predetermined distance from the upper boundary of the target. This distance is typically between λ / 5 and 10λ, where λ represents the wavelength of the HIFU pulse. Additionally or alternatively, the safety margin may also be defined based on the variability in the size of the generated bubble cloud or the resulting damage (which can be, for example, measured, simulated, estimated, or known from prior experiments).

[0042] In yet another preferred embodiment, the target depth is defined as a safety margin added to the depth of the surface portion, the center of the target lumen, or the deep portion of the target wall. Specifically, the safety margin can be defined as a percentage of the lumen wall thickness or the size of the foci. Preferably, it includes a range of 0 to 5 mm, or even more preferably, 0.1 to 1 mm.

[0043] These methods are also applicable to situations involving infiltration (e.g., tumescent anesthesia). In this case, the distance can, but is not necessarily, be implemented relative to a target area filled with injected fluid. For example, the rule applied could be to always position the top of the focal spot outside the upper boundary of the area filled with injected fluid. In a preferred embodiment, the target depth is therefore defined as the depth of the surface portion of the area filled with fluid due to infiltration.

[0044] In another preferred embodiment, the target depth is defined as the depth of the surface portion of the area filled with fluid due to wetting, plus a safety margin.

[0045] In practice, this distance from the target depth is preferably achieved based on automatic or manual segmentation of the target on the acquired image. Preferably, it is based on A-mode, B-mode, color Doppler, dual-function ultrasound, or magnetic resonance imaging. It can also be based on passive or active cavitation, bubble detection algorithms: for example, after providing pulses designed to induce cavitation only in blood (because it is easier in tissue), the location of a vein can be determined based on cavitation mapping.

[0046] In a preferred embodiment, the target depth for each treatment site is determined based on an automatic segmentation algorithm. For example, when the vein is not compressed, it can be easily segmented based on the fact that the lumen is hypoechoic and free of speckle. If it is at least partially compressed, segmentation of the open vein can be utilized and the segment can be followed using a speckle tracking algorithm or based on anatomical landmarks (fascia, bone, etc.).

[0047] In a preferred embodiment, the safety margin varies according to the characteristics of the pulse (duration, power, beam shape, etc.). Preferably, it increases as the power or duration increases. Preferably, this variation is automatic based on prior knowledge obtained from previous experiments, simulations, or measurements.

[0048] In an alternative preferred embodiment, the target depth is determined for each segment based on manual segmentation of the target. Alternatively, it can be based on manually setting one or more markers on real-time images.

[0049] Setting the focal spot according to one of these criteria may damage tissue located beneath the target. However, since contraction of surrounding tissue can compress structures and thus improve treatment outcomes, this should not be considered harmful.

[0050] In another preferred embodiment, a marker indicating the location associated with the focal spot is overlaid on the monitoring image, and the position of the focal spot relative to the target is adjusted before each pulse, which is typically done by the user.

[0051] In particular, the markers can be overlaid on the surveillance image and the user can set the focal spot so that, for example, the marker is below the upper boundary of the target, as seen in the image.

[0052] Additionally or alternatively, at least one mark indicating the extent along the ultrasonic propagation axis is superimposed on the monitoring image. The extent indicates the location where the target should be.

[0053] In a preferred embodiment, the focal spot is configured such that tissue located deeper than the target is pulsed and damaged less than tissue located above the target. Preferably, tissue located above the target is not damaged at all.

[0054] In some cases, bubble clouds may still form even when the method according to the invention is applied due to statistical fluctuations (e.g., due to local tissue characteristics). In particular, bubble clouds may be generated above the target even when the proposed apparatus or method is applied. In this case, it is preferable to adjust the spacing between several treatment sites to avoid a masking effect. Therefore, alternatively or additionally, the invention also provides and relates to a method for modifying the direction or position of the HIFU beam when a bubble cloud is detected. Bubble clouds can be detected automatically through continuous or repetitive monitoring. Modification of the HIFU beam can then also be performed automatically based on the monitoring results. In an alternative embodiment, modification can occur based on manual detection of the bubble cloud.

[0055] Therefore, another method according to the invention may also include monitoring for the presence of a bubble cloud that would interact with the HIFU beam in soft tissue above the target. If such a bubble cloud is detected, the method includes modifying the focal spot position of the HIFU pulse.

[0056] In a preferred embodiment, the modification of the HIFU pulse position occurs based on manual detection of the bubble cloud.

[0057] Preferably, when the bubble cloud is visible above the target or at a specific depth defined relative to the target, the lateral spacing between treatment sites is increased to ensure that the bubble cloud is not within the ultrasound beam. Additional safety margins can also be used to account for diffraction and variability in tissue properties.

[0058] In a preferred embodiment, the modification occurs based on the automatic detection of bubble clouds.

[0059] Bubble cloud detection algorithms for automatic detection of bubble clouds can be employed. In particular, this is advantageous if monitoring is based on B-mode imaging and the bubble cloud is caused by boiling. This is because bubble clouds caused by boiling exhibit easily detectable high-echoic features, especially when comparing the post-pulse image with at least one image captured before the pulse. This comparison can be performed by algorithms, particularly those disclosed in EP 2 599 444.

[0060] In particular, overlays may be used. An overlay should mean a means for displaying graphic depictions (preferably markings) on real-time and / or acquired ultrasound images. For example, an overlay may include illustrations of focal spots and / or different markings to indicate therapeutic features and / or some anatomical structures.

[0061] In a preferred embodiment, a safety margin regarding the focal spot location or other pulse characteristics (power, duration, beam shape, etc.) is adjusted based on the position and size of one or more bubble clouds generated relative to the target by one or more previous pulses. For example, for the first pulse, a -6 dB focal spot can be manually positioned tangent to the upper boundary of the vein based on an appropriate overlay indicating the spot location on the real-time image. Based on prior experiments, the resulting bubble cloud is expected to extend 2 mm above the target, which will not negatively impact subsequent pulses. After this pulse is sent, the bubble cloud is automatically segmented based on the B-mode image. Due to the local features of the tissue and the pulse parameters, the bubble cloud appears to extend 4 mm above the target. Therefore, the safety margin is automatically increased from 0 mm to 2 mm to compensate for this unexpected growth of the bubble cloud above the target. The overlay is modified to include a mark indicating that the upper boundary of the focal spot should be set 2 mm below the upper boundary of the vein. For example, a small segment is shown 2 mm above the focal spot in the illustration.

[0062] In an alternative preferred implementation, the modification is triggered by the user. Specifically, the user can manually trigger an increase in the lateral spacing between treatment areas by manually setting the next area or by using simple interactions (buttons) on the user interface, which automatically adds a predetermined value to the spacing.

[0063] Alternatively, the lateral spacing is limited prior to treatment based on prior knowledge of the size of the bubble cloud caused by the pulse.

[0064] In particular, the lateral spacing within a segment can vary within a range.

[0065] If the monitoring device only provides 2D information (which is the case for a conventional mode B imager), the imager is preferably rotated or moved perpendicular to the imaging plane to obtain 3D information about the location of the bubble cloud and the spacing is adjusted as described above.

[0066] In a preferred embodiment, the position of the pulse is modified by moving the beam approximately perpendicular to the main ultrasound propagation axis so that the HIFU beam is tangential to or substantially does not intersect with the bubble cloud.

[0067] In another preferred embodiment, the position of the pulse is modified by moving the beam approximately perpendicular to the main ultrasound propagation axis by a certain distance, thereby providing a safety margin for the separation of the HIFU beam and the bubble cloud.

[0068] The implementation of the above method may be difficult in practice because several concurrent factors, including venous compression and focal spot position, must be adjusted. According to another aspect, the present invention therefore further addresses this difficulty by targeting devices for performing ultrasound therapy, particularly HIFU therapy.

[0069] The present invention also relates to an apparatus.

[0070] Ultrasound therapy devices, particularly HIFU (High-Intensity Focused Ultrasound) therapy devices, include a probe. The probe has an ultrasonic transducer for delivering therapeutic ultrasonic waves focused on a target within the object. The device also has an imaging device for imaging the object, preferably within the treatment head, including a display. The device includes a controller unit operatively connected to the transducer to control the emission of HIFU pulses, and optionally connected to an actuator and a compression unit. The display is adapted to overlay at least one marker on the monitoring image. This marker indicates the location associated with the focal spot and / or the extent to which the target should be located along the ultrasonic propagation axis.

[0071] It may also include a compression unit for applying compressive force to the object, and / or an actuator that allows the probe to move at least along the main ultrasound propagation axis or substantially perpendicular to the patient's skin.

[0072] Preferably, to avoid potentially dangerous lateral movement to the patient, the actuator is controlled to move along the main ultrasound propagation axis or approximately perpendicular to the patient's skin.

[0073] This device is particularly well-suited for allowing manual positioning of the focal spot of a HIFU treatment transducer near a target. The device may additionally or alternatively be adapted to allow the user to indicate the location of the target or the desired or acceptable range of the focal spot. The device may also be adapted to automatically adjust the position of the focal spot based on an image tracking algorithm using a controller unit to induce the actuator and compression unit.

[0074] Specifically, the device includes a memory and is adapted to store in the memory a target depth (or range) representing the area where the target should be located relative to the focal spot. It may further include an overlay display device to assist the user in properly positioning the focal spot relative to the vein (e.g., an overlay of the focal spot, markers depicting the locations where anatomical structures (e.g., deep walls of the target) should be located, or an overlay of the range where the target should be located). Finally, the device can be adapted to automatically locate the focal spot based on the location of the vein and an automatic segmentation algorithm that can follow the target's position relative to the focal spot in real time as the target's position is adjusted (speckle tracking, or automatic segmentation based on veins or anatomical landmarks).

[0075] Preferably, the treatment device thus allows the user to roughly position the focal spot near the desired location, and the device automatically fine-tunes the position of the focal spot and optionally the level of compression of the target or other factors.

[0076] Fine-tuning can be performed based on optimization algorithms. In this context, the cost function can be limited to quantifying the "distance" between the actual state and the desired state, characterized by the location of the focal point and optionally by the state of venous collapse and other possible state factors. Then, optimization algorithms (gradient method, Newton's method, metaheuristic method, etc.) can be used to adjust the parameters to minimize the cost function.

[0077] Because veins can be completely collapsed, image-tracking algorithms that only track veins may not be sufficient. This could be the case, for example, if a treatment head is pushed against the skin and pressure is applied to the anatomical structure. Therefore, the algorithm could include a speckle tracking algorithm. This algorithm also considers the environment of the vein, such as the surrounding tissue.

[0078] In a preferred embodiment, the compression unit includes a membrane element mounted on the probe. The membrane element defines a chamber that can be filled with fluid.

[0079] Fluid ensures acoustic coupling, as disclosed in, for example, WO2011064209A1. The pumping system enables fluid to circulate from the reservoir to the membrane in a closed loop. At least one controller unit is capable of controlling fluid circulation according to at least one rule (e.g., constant fluid pressure within the membrane or constant fluid volume within the balloon). This controller can be the same as described above or a separate, independent controller. Appropriate sensors (e.g., pressure sensors within the balloon) are provided to control the operation of the pumping system.

[0080] An ultrasound probe and a therapeutic transducer can be embedded in the probe, which is held by an actuator. Preferably, the actuator can move at least along the main ultrasound propagation axis or substantially perpendicular to the patient's skin.

[0081] Fluid is circulated via a pumping system. The pumping system can be operated in at least two operating modes via a controller unit. In a first operating mode of the controller unit, the pressure of the fluid in the chamber is controlled such that when the transducer moves a given distance perpendicular to the skin or along the main ultrasound propagation axis, it causes the focal spot to shift approximately the same distance in the same direction within the anatomical structure. In this second mode, transducer movement is translated into approximately the same amount of focal spot movement within the anatomical structure. The fluid pressure remains constant.

[0082] In the second operating mode of the controller unit, the pressure is controlled such that when the transducer moves perpendicular to the skin or along the main ultrasound propagation axis, it causes target compression but does not cause a significant change in the depth of the focal spot beneath the skin. The fluid volume within the balloon remains constant.

[0083] These two operating modes allow the execution of the methods described below.

[0084] The treatment device may also include at least one monitoring device (e.g., an ultrasound probe), a display, and a device for operator interaction with the display (e.g., a touchscreen).

[0085] The present invention also relates to the method of using the device disclosed above.

[0086] In the first step, the treatment transducer is manually set so that the focal spot is near the target and the target is within the monitor's field of view. The desired or acceptable location range of the target or focal spot is then graphically marked on the monitor. Additionally, the device fine-tunes the parameters of the compression unit and moves the transducer to properly set the focal spot. Preferably, the device is adapted to automatically fine-tune parameters (e.g., pressure within the coupling fluid, and / or feedback loop parameters) and move the transducer to set the focal spot at the desired location and compress the target to the desired level. Specifically, the operator can set the treatment transducer and / or delineate the desired location within an acceptable range for the target or focal spot. Additionally or alternatively, the device can calculate the target's position within the anatomical structure based on a tracking algorithm that uses the operator-drawn location as the target position.

[0087] For example, the step of automatically fine-tuning the parameters of the compression unit can be performed by iteratively adjusting the position of the focal spot in the anatomical structure by moving the actuator when the fluid control is in pressure control mode and compressing the target when the fluid control is in volume control mode.

[0088] The step of outlining the desired location or acceptable range of the focal spot can also be omitted, and the target location is automatically detected by the software without operator input. Specifically, an automatic segmentation algorithm based on the contrast between the vein lumen and surrounding tissue can be used. The latter is hypoechoic. Detection is preferably performed near or in a predetermined area around the focal spot, or by penalizing the distance to the focal spot.

[0089] This invention also relates to a method of using an ultrasound device, particularly a HIFU treatment device. The device includes a handheld probe comprising an ultrasound transducer for focusing therapeutic ultrasound waves onto a target within an object and an imaging device for imaging the object. A controller unit is operatively connected to at least the probe and a compression unit. The compression unit is provided to apply a compressive force to the object. The compression unit also includes a diaphragm mounted on the probe, filled with fluid circulated by a pumping system. The controller unit is adapted to control the pumping system and the compressive force by switching between at least two operating modes. In a first operating mode (R1) of the controller unit, moving the transducer perpendicular to the skin or along the main ultrasound propagation axis a given distance causes the focal spot to shift approximately the same distance in the same direction within the anatomical structure. In a second operating mode (R2) of the controller unit, moving the transducer perpendicular to the skin or along the main ultrasound propagation path causes compression of the target but does not cause a significant change in the depth of the focal spot beneath the skin. The method of using the device includes controlling the compressive force and the pumping system such that focal spot positioning is performed in mode R1 and adjustment of target compression is performed in mode R2.

[0090] In a preferred embodiment, the method further includes a feedback loop, wherein the steps of locating the focal spot and adjusting target compression are repeated alternately. Specifically, the feedback loop can be used to facilitate focal spot location and includes the following steps:

[0091] i.) Control fluid circulation according to rule R1, which makes it easy to locate the focus.

[0092] ii.) Switch the fluid circulation to rule R2, which allows the target to be compressed without significantly altering the position of the focal spot within the anatomical structure.

[0093] If precise adjustment of the focus position is required, several iterations can be performed.

[0094] Alternatively, a third step iii.) can be implemented, in which the fluid circulation is switched to a mode in which the fluid pressure is kept constant at the current value, which may be high due to the control device being controlled according to rule R2 during step ii.). Attached Figure Description

[0095] The present invention will now be described in detail with reference to the following accompanying drawings:

[0096] Figure 1 The effect of the bubble cloud interacting with the ultrasonic beam is illustrated schematically.

[0097] Figure 2 The working principle of the method according to the invention is illustrated schematically, wherein the interaction between the bubble cloud and the ultrasonic beam is avoided.

[0098] Figure 3 The diagram illustrates the location of focal spots with different safety margins.

[0099] Figure 4 The working principle of the method according to the invention is illustrated schematically, wherein the interaction between the bubble cloud and the ultrasonic beam is avoided from the top.

[0100] Figure 5 A schematic diagram of an ultrasonic device according to the present invention is shown.

[0101] Figure 6 The orientation of the focus relative to the target and treatment head is schematically shown. Detailed Implementation

[0102] Figure 1 The working principle of the method according to the invention is shown, and the object of the invention is explained. HIFU treatment is delivered to a target comprising a wall 3 and a lumen 4. To avoid the formation of a bubble cloud in region 2 between the targets 3, 4 and the treatment head, the focus 32 of the HIFU beam is set below the target level 31 in the direction of ultrasound propagation. In this example, the target level is chosen as the inner surface boundary of the target wall 3. However, the center or outer surface level of the target wall 3 can also be used. The lower focus 32 allows treatment to be performed without the formation of a new bubble cloud.

[0103] However, the previous pulse 5 may have already generated a bubble cloud in region 2 that interacted with the ultrasonic beam 1. This interaction resulted in region 6, which experienced increased heating, and region 7, which was then shielded.

[0104] Figure 2 A preferred embodiment of the method according to the invention is illustrated schematically. During treatment of a target comprising a wall 3 and a lumen 4, the HIFU beam 1 is positioned such that no bubble cloud is expected to form in the tissue above the target. However, a bubble cloud has already formed and been detected in region 2 during a previous HIFU emission step (not shown). Because the current bubble cloud in region 2 can interact with the HIFU beam 1, the position of the HIFU beam is modified by laterally shifting an appropriate distance 8 to avoid this interaction.

[0105] Figure 3This illustrates how the focal spot 9 is tangent to the more superficial boundary of the target when treating a target including the wall 3 and the lumen 4. Figure 3 a) Tangent to the center of the target ( Figure 3 c) or the deeper boundary of the target ( Figure 3 e) Tangent. An additional safety margin can be used ( Figure 3 (b, 3d, and 3f). Although not explicitly shown in the figures, those skilled in the art will recognize that other locations for the focal spot, particularly those between the illustrated cases, are feasible. For example, the focal spot could be tangent to the level of the outer surface of the upper wall or the level of the inner surface of the upper wall. In all cases, soft tissue deeper than the target will be damaged. As a general rule, the deeper the focal spot 9 is positioned relative to the target level, the less likely it is to form a bubble cloud in the tissue above the target wall 3. However, the therapeutic effect on the target wall 3 decreases with increasing depth. Therefore, the focal spot should be located as deep as possible to avoid the formation of a bubble cloud, but should be as close as possible to the target level.

[0106] Figure 4 Treatment is described in a plane perpendicular to the propagation axis of the HIFU beam. In the case of treating a target including the wall 3 and lumen 4, previous pulses 10a, 10b, and 10c have generated bubble clouds 11 that extend into the soft tissue above the target. When positioned at the planned site 12, the imaging probe rotates to contact the bubble clouds 11 generated by the previous pulses 10a-10c. Because the bubble clouds 11 interact with the HIFU beam (not shown), the site moves to another location 13.

[0107] Figure 5 An apparatus 50 for treating a patient via HIFU according to the present invention is schematically shown. The apparatus 50 includes a probe 51 having a treatment transducer 55. This transducer is adapted to provide ultrasound waves focused onto a target 54 in an object 53. In this embodiment, the treatment head 51 also includes an imaging device 56. The treatment head also includes a compression unit 52, here in the form of a diaphragm 64, which is mounted on the probe 51 and forms a chamber for receiving fluid. The fluid in the chamber is circulated by a pumping system 63. The apparatus also includes an actuator 60 connected to the probe 51 via an arm 57 and adapted to move the treatment head 51 along a main ultrasound propagation axis 58 and perpendicular to the patient's skin 59. The apparatus also includes a controller unit 61 operatively connected to the transducer 55, the compression unit 52, and the actuator 60, in this example connected via a cable 62.

[0108] Figure 6 It schematically shows, as Figure 5The treatment head 51 is shown, in which a balloon 52 is placed on the patient's skin 100 to treat a target 103. The center of the focal spot 101 is located deeper than the target. For illustration, an axis 102 extending from the treatment head 51 through the target 103 is shown. The center of the focal spot 101 is farther from the treatment head 51 than the target, i.e., the distance between the treatment head 51 and the center of the focal spot is greater than the distance between the target and the treatment head 51. Therefore, the center of the focal spot 101 is not located between the target 103 and the treatment head.

Claims

1. A HIFU treatment device for performing a method of treating veins (3, 4) via a HIFU beam (1), the device (50) comprising: The probe (51) has an ultrasonic transducer (55) for providing the HIFU beam (1) with a focal spot (32, 101) focused on the target (54) within the object (53). An imaging device (56) for imaging the object (53) includes a display. A controller unit (61), operably connected to the ultrasonic transducer (55), is used to control the transmission of the HIFU beam. A memory, wherein at least one of the location associated with the focal spot and the range in which the target should be located along the main ultrasound propagation axis is stored in the memory. The method includes: The positioning probe positions the center of the focal spot (32, 101) deeper than the center of the vein, and the method further includes emitting HIFU pulses such that the center of the focal spot is deeper than the center of the vein, and the upper boundary of the focal spot is located at or deeper than the upper boundary of the vein, thereby avoiding or limiting the generation of air bubbles in the first tissue located between the probe and the vein during HIFU pulse emission. The device is characterized in that, The display is adapted to overlay at least one mark on the monitored image, wherein the mark represents at least one of the location associated with the focal spot and the range in which the target should be located along the main ultrasonic propagation axis.

2. The apparatus according to claim 1 further includes an actuator (60) for moving the probe (51).

3. The apparatus according to claim 2, wherein, The controller unit (61) is operatively connected to at least the actuator (60) and the compression unit (52), wherein the device (50) is adapted to: Allows manual positioning of the focal spot of the ultrasonic transducer (55) near the target (54), and Allows the user to indicate the location of the target (54) or the desired or acceptable location range of the focal spot (32), and The controller unit (61) uses an image tracking algorithm to automatically adjust the position of the focal spot (32) to set the focal spot, guide the actuator (60) and / or the compression unit (52).

4. The apparatus according to claim 1 or 2, wherein, The focal spot can move together with the multi-element transducer.

5. The apparatus according to claim 1 or 2 further includes a compression unit (52) for applying a compressive force to the object (53).

6. The apparatus of claim 1 or 2 further comprises a pumping system through which the fluid is circulated.

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