Monitoring ablation progress using linear EBUS data

Abstract

A system and method for treating target tissue using cryoablation are presented. A linear intrabronchial ultrasound (EBUS) device is positioned adjacent to the target tissue and used to guide a percutaneously inserted cryoablation probe into the target tissue. The EBUS device is partially rotated to generate multiple image slices, which are then combined. To overcome the acoustic shadow generated by the ice ball, a 3D model of the ice ball is generated based on positions identified on the visible portion of the ice ball's periphery. These positions are mirrored across axes defined for the cryoablation probe to determine the approximate positions of the hidden, invisible periphery. This model is then displayed along with the location of the target tissue and a representation of the necrotic region of the ice ball, defined by selected isotherms.

Description

Technical Field

[0005]

[0001] Priority Claim This application claims the benefit of priority of U.S. Patent Application No. 18 / 200,161, filed on May 22, 2023. The content of this U.S. patent application is incorporated herein by reference.

[0002] The present disclosure relates to a linear endobronchial ultrasound (linear EBUS) for monitoring cryoablation treatment of target tissue by inserting an ultrasonic probe into the lung.

Background Art

[0003] Cryosurgery or cryoablation is a procedure that destroys abnormal or target tissue through a freezing process. By freezing tissue cells, the cells or organelles within the cells rupture. Typically, the cryosurgery process involves inserting a device ("cryoprobe") into the abnormal tissue and then cooling this device. In most cases, cooling of the cryoprobe is achieved by passing a high-pressure gas, such as argon, through the device. By cooling the cryoprobe in this way, an "ice ball" of frozen tissue centered around the distal end of the cryoprobe is formed.

[0004] To succeed in this procedure, it is important that the size, shape, and position of the ice ball are accurately determined. If the ice ball is larger than necessary, healthy tissue located around the target tissue will be damaged unnecessarily. If the ice ball is too small, abnormal tissue that should have been killed through this process will remain.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

[0006] One embodiment of the present disclosure presents a method for treating tumors or other target tissues using cryoablation. This method begins with locating the target tissue, for example, by performing pre-procedure CT imaging. By combining the generated images, a 3D image or 3D model of the patient or the patient's organs may be generated. This 3D model of the patient's anatomical structures (e.g., lungs) is then aligned with the patient's body structure, for example, by using electromagnetic fields and position sensors (or other surgical navigation techniques).

[0007] During the procedure, a linear intrabronchial ultrasound (EBUS) device is positioned adjacent to the target tissue within the patient's trachea and bronchial tree. The EBUS then images the target tissue, and at this point, the ultrasound image data can be used to fine-tune the alignment between a 3D model of the patient's anatomical structure and the patient's body structure, i.e., the actual anatomical structure. These EBUS images may be used to guide a cryoprobe that is percutaneously inserted into the target tissue. For example, similar to a linear EBUS device, the cryoprobe may have an electromagnetic sensor that allows for the determination of the position and orientation of the probe tip within an electromagnetic field. The cryoprobe then initiates the freezing of the target tissue.

[0008] At this point, the EBUS device generates multiple image slices by being partially rotated, and these slice images are combined to generate a 3D image and 3D model of the target tissue and the growing ice ball. Due to impedance mismatch resulting from the properties of the ice ball relative to the surrounding unfrozen tissue, the ultrasonic energy emitted from the EBUS device may not be able to pass through the surrounding surface (or periphery) of the ice ball.

[0009] A 3D model of the ice ball is generated to give the practitioner an understanding of the relationship between the growing ice ball and the target tissue. This model is created by identifying the visible portion of the ice ball's surrounding surface and determining the locations of its points. These locations are then compared to an axis defined by the orientation of the tip of the freezing probe. A line segment perpendicular to this axis is identified to a point on the surrounding surface. Then, using a line segment of the same length on the opposite side, a point representing an approximate location on the hidden, invisible surface of the ice ball is identified. By "mirroring" a sufficient number of points across the axis of the freezing probe, the approximate locations of large segments of the hidden, invisible surface are defined. This is then combined with the points on the visible surface to generate a model of the ice ball.

[0010] The generated model is presented to the practitioner on a computerized user interface (typically on a computer display), which also displays the location of the target tissue in the same 3D space. Furthermore, this interface displays approximate isotherms / isothermal surfaces within the iceball model. These isotherms indicate the approximate range of the necrotic zone of the iceball. In one embodiment, these isotherms are drawn in an estimated range that has a persistent temperature of -40°C. The system is designed to recognize whether the iceball forming at the location of the target tissue is a first or second iceball. If it is a second iceball, the isotherms / isothermal surfaces may be drawn in a higher temperature approximation, since effective necrosis is possible at higher temperatures (e.g., -30°C) if the tissue has undergone repeated freeze-thaw cycles. If the EBUS device detects expansion of the periphery of the iceball, the periphery and isotherms are redrawn in real time. In this case, the practitioner can modify the planned freezing process as a result of the display on the user interface 1200. [Brief explanation of the drawing]

[0011] [Figure 1] This is a perspective view showing percutaneous insertion of a cryoprobe under the guidance of an intrabronchial ultrasound (EBUS) device. [Figure 2] This is a schematic side view of the ultrasonic transducer of an EBUS device that forms an observation area showing the target tissue. [Figure 3] This is a plan view of the distal tip portion of a second embodiment of an EBUS device. [Figure 4] This is a schematic diagram of an EBUS device that generates multiple slices through rotation. [Figure 5] Figure 1 is a schematic side view of the freezing probe that punctures target tissue and forms an ice ball. [Figure 6] This is a schematic diagram of a formed ice ball, with three isotherms illustrated. [Figure 7]Schematic diagram of the formed ice ball in Fig. 6 after the second freezing. [Figure 8] Schematic diagram of the EBUS device of Fig. 2 showing an idealized image of the ice ball formed within the target tissue. [Figure 9] Schematic diagram of the EBUS device of Fig. 2 for observing the ice ball formed within the target tissue under the condition where an acoustic shadow has occurred. [Figure 10] Schematic side view showing the formation of an ice ball model by mirroring. [Figure 11] Schematic axial view showing the formation of an ice ball model by mirroring. [Figure 12] Figure showing a user interface indicating the positions of the ice ball models in Figs. 10 and 11 and the target tissue. [Figure 13] Flow chart showing a method for implementing an embodiment of the present disclosure. [Figure 14] Schematic diagram of the EBUS device of Fig. 2 showing an idealized image of an irregular ice ball. [Figure 15] Schematic diagram of the EBUS device of Fig. 2 for observing an irregular ice ball under the condition where an acoustic shadow has occurred. [Figure 16] Figure showing a user interface indicating the positions of the ice ball models in Figs. 10 and 11 and the target tissue.

Mode for Carrying Out the Invention

[0012] Formation of Ice Ball Cryoablation is typically performed to kill abnormal tissue previously detected in a patient. In most cases, the exact location of this abnormal tissue is identified by imaging using prior art such as CT or MRI imaging. Further, using this data, it is possible to generate a 3D model of the patient including the abnormal tissue. Analysis of this 3D model enables the creation of a treatment plan including targeting the abnormal tissue for ablation. Depending on the situation, this analysis determines that cryoablation should be utilized to ablate this target tissue.

[0013] Under such circumstances, as shown in FIG. 1, to treat a patient using a cryoablation procedure, patient 100 is prepared. Computer system 140 is in communication with the devices used on the patient and is involved in the display of the 3D model of the patient on display 150. Patient 100 is registered with navigation system 160 using an initial registration process well-known in the prior art. In some cases, this registration process involves placing patient 100 within an electromagnetic field generated by navigation system 160, guiding a navigation-compatible surgical instrument within the 3D space monitored by navigation system 160 to a known location of the patient's body structure (such as the main tracheal bifurcation, etc.), and then updating the reference coordinate system data to place the 3D model in the same position relative to the patient's body structure. Devices having electromagnetic (EM) sensors are capable of detecting this electromagnetic field and further of being located within the electromagnetic field, i.e., these devices located within the 3D space can also be located relative to the 3D model of the body. Electromagnetic field-based surgical navigation technology is just one of a number of known surgical navigation technologies that can be deployed in various embodiments of the present disclosure. In these embodiments, the electromagnetic field generator within navigation system 160 may be replaced with different navigation technology devices that enable position navigation of the instruments registered in the 3D model of the patient.

[0014] As shown in Figure 1, once the procedure is ready to begin, the target tissue 120 of the patient 100 is located using a linear endobronchial ultrasound (EBUS) device 110. In one embodiment, as shown in Figure 2, the linear EBUS device 110 has a curve array of ultrasound transducers 112 at its distal tip. The EBUS device 110 can also constitute part of a bronchoscope, such as the commercially available Olympus BF-UC180F from Olympus (Tokyo, Japan).

[0015] The EBUS device 110 is inserted into the trachea and bronchial tree and manipulated to a position near the target tissue 120. The ultrasound transducer 112 is acoustically coupled to the airway wall 202, either by direct contact or by inflating a saline-filled balloon (not shown in Figure 2) that surrounds the transducer 112 and contacts the airway wall 202. Once acoustically coupled, the ultrasound transducer 112 can acquire an image of the tissue located on the opposite side of the airway wall 202. In Figure 2, this image region is shown as image region 114. In this case, image region 114 represents a portion of the target tissue 120.

[0016] The EBUS device 110 incorporates EM sensors 116 positioned near the ultrasonic transducer 112, which sense the electromagnetic field present around the patient 100. Importantly, these EM sensors 116 can identify all six degrees of freedom (DoF), consisting of x, y, and z positions, as well as pitch, roll, and yaw. Typically, physical sensors can sense five of the six degrees of freedom. For example, using techniques such as those described in U.S. Patent No. 8,696,549 (owned by Veran Medical Technologies, Inc., St. Louis, Missouri, USA), it is possible to identify a sixth degree of freedom from a sensor 116 that only senses five degrees of freedom. Alternatively, all six degrees of freedom can be identified using two offset five-degree-of-freedom sensors. If the x, y, and z positions of the tip are known, along with the pitch, yaw, and roll orientation of the tip, the computer system 140 can interpret the ultrasonic image data acquired by the sensor 116 and gain a deeper understanding of the position of this image data.

[0017] In one embodiment, the imaging data from image region 114 can be used to precisely locate the target tissue 120 relative to the EBUS device 110. This is because the location of the target tissue 120 is precisely known within the patient's 3D model, and the EBUS device 110 can also be located relative to this 3D model. As a result, this new information can be used to fine-tune the alignment process between the model and the patient. In other words, the imaging data from image region 114 may indicate that minor corrections are needed to accurately align the positional information generated by the electromagnetic field and EM sensor 116 with the 3D model.

[0018] Next, after this fine-tuning of alignment, the ultrasound transducer 112 is used to monitor the percutaneous insertion of the cryoprobe 130 into the patient 100. The tip 132 of the cryoprobe 130 may be specially designed to improve its identifiability under ultrasound, for example, by providing grooves or other physical deformable parts (e.g., highly echogenic features) that are highly visible to ultrasound energy. As shown in Figure 2, ultrasound imaging by the EBUS device 110 allows observation of this tip 132, which can help the operator guide the cryoprobe 130 to the target tissue 120.

[0019] Furthermore, Figure 1 shows one or more computer systems 140 that send signals and power to the EBUS device 110 and the freeze probe 130, receive signals from these devices 110 and 130, analyze those signals, and display the analysis results to the user. Such a computer system 140 is a standard computing device equipped with a CPU, short-term and long-term storage, computer programming, a display system, and interfaces as needed for communication with and control of the devices 110 and 130. In addition, the computer system 140 is also involved in carrying out the calculation and display steps in the method described herein. The computer system 140 may consist of a single computer or multiple computers that control the devices 110 and 130 and operate individually or jointly to carry out the method described herein.

[0020] Figure 3 shows an alternative embodiment of the ultrasound catheter 300 in which the linear transducer array 310 is located near the tip 302 of the catheter 300. The linear transducer array 310 may be flat and, in one embodiment, is located on a flat surface 320 at the tip of the ultrasound catheter 300. Thus, the ultrasound catheter 300 differs from the EBUS device 110 shown in Figures 1 and 2, which has a curved array of ultrasound transducers 112. However, the ultrasound catheter 300 also comprises the EBUS device 110. The flat surface 320 may extend along the entire length of the catheter 300 or terminate at position 322. Position 322 separates the tip portion having the flat surface 320 from the rest of the catheter 300 330. Thus, this rest portion 330 may have a circular or substantially round cross-section to facilitate movement within the introduction catheter 350. The cross-section of the tip portion having a flat surface 320 may be semicircular, and the flat surface 320 holding the linear transducer array 310 is located on a rounded bottom portion (not shown). Furthermore, the catheter 300 may include an electromagnetic (EM) sensor 340 embedded in the distal end 302. These EM sensors 340 function as described above in relation to the sensor 116. The electronic device package 342 is coupled to the linear transducer array 310 and the EM sensors 340, enabling control of signals transmitted to and from these components.

[0021] The ultrasonic transducers 112, 310 within the EBUS device 110 may be configured in accordance with the disclosures of U.S. Provisional Patent Application No. 62 / 776,667 and U.S. Provisional Patent Application No. 62 / 776,677, both filed jointly by the owner of this application on December 7, 2018. The entire contents of these two provisional applications are incorporated herein by reference. These ultrasonic transducers 112, 310 may also be micromachine ultrasonic transducers (or MUTs), such as piezoelectric MUTs (or pMUTs) and capacitive MUTs (or cMUTs), where pMUT transducers often utilize a lead zirconate titanate (or PZT) piezoelectric layer. These types of transducers are capable of transmitting and detecting ultrasonic energy at various frequencies, such as in the range of 4 MHz to 50 MHz.

[0022] Figure 4 shows a typical configuration of a linear EBUS device 110 that is rotatable in a fixed position around a rotary access 400. Furthermore, Figure 4 shows various image region slices 410 that are individually generated at different rotational positions of the EBUS device 110. Each of these slices 410 effectively forms a two-dimensional image plane generated by the EBUS device 110. During use, the EBUS device 110 can be rotated around the rotary access 400 by the physician performing the procedure, either manually or by the use of a rotary stepping motor (not shown). Motorized rotation can help generate a sufficient number of slices 410 to enable "live" 3D ultrasound image generation. A roll sensor on the EBUS device 110 can determine a specific orientation of the image slices 410.

[0023] As shown in Figure 4, multiple slices 410 may contain data representing the target tissue 120. The computer system 140 receives image data representing each of these individual image slices 410 from the EBUS device 110. These individual slices can be stored by the computer system 140 and displayed when requested, but the computer system 140 can also combine the information in the multiple slices 410 into a single model of the portion of the patient shown in these slices 410, which includes a model of the target tissue 120. This model can then be presented to the physician as a 3D image of that region. The generated model can also be incorporated into a previously generated 3D model of the patient 100.

[0024] Monitoring of cryoablation As shown in Figures 1 and 2, the EBUS device 110 can identify and locate the target tissue 120 and track the insertion of the cryoablation probe 130 into the target tissue 120. Furthermore, the EBUS device 110 can also monitor the cryoablation process itself. This process begins after the tip 132 of the cryoablation probe 130 is inserted into the target tissue 120, as shown in Figure 5. Argon gas then passes through the probe 130. Due to the design of the probe 130, this gas expands at or near the tip 132. As argon gas decreases in temperature upon expansion, this expansion causes very rapid cooling of the tip 132 of the probe 130. In a conventional cryoablation probe 130, the injection of argon gas causes the tissue located near the tip 132 to reach a temperature of -160 to -170 degrees Celsius (°C). This temperature causes the ice ball 520 of the frozen tissue to rapidly form adjacent to the tip 132 and expand into the target tissue 120.

[0025] The temperature of the ice ball 520 formed near the probe can be below -160°C, while the surface temperature of the ice ball 520 remains at 0°C. It is generally accepted that, in order to reliably destroy the tissue, it needs to reach a temperature of -40°C or below for approximately 3 minutes. This temperature causes intracellular freezing, which is destructive to most cells. Therefore, the abnormal tissue is typically frozen for 3–5 minutes during the cryoablation procedure. As shown in Figure 6, the size of the ice ball 520 has increased at this point. After this time period, at least half of the diameter of the ice ball 520 has reached -40°C. This is schematically illustrated by the central region 600 in Figure 6. The broader shaded region 610 indicates the approximate location of the -20°C isotherm, and the outer surface 620 of the ice ball 520 has a temperature of -0°C.

[0026] Most cryoablation practitioners perform this procedure twice because only the portion of the ice ball 520 that maintains a sustained temperature of -40°C is reliably destroyed. After the first formation of the ice ball 520, this ice ball is thawed. The slow thawing of the frozen tissue within the ice ball 520 causes the ice crystals to fuse during thawing, forming larger crystals, which in turn cause further cell damage. This thawing process can be accelerated by passing helium through the cryoablation probe 130. Unlike cryogenic gases such as argon, helium increases in temperature when it expands. When helium passes through the cryoablation probe 130, the opposite effect is obtained compared to argon, and the tip 132 of the cryoablation probe 130 is heated.

[0027] In the standard procedure of freezing abnormal tissue a second time after thawing, tissue freezing occurs more rapidly (resulting in greater destructiveness to the tissue). This makes it possible to completely destroy the tissue at a slightly higher temperature, such as -20°C to -30°C. As a result, the effective therapeutic area of ​​this procedure is closer to the periphery 420 of the ice ball 520. As shown in Figure 7, the central necrotic area extends to the vicinity of the -20°C isotherm 610. In most cases, the distance between the necrotic area and the periphery of the ice ball is considered to be 4 to 10 mm. Since the outer region of the ice ball 520 is located outside the area 610 where the therapeutic effect is guaranteed, it is generally necessary to form an ice ball larger than the tissue 120 that is to be destroyed during cryosurgery.

[0028] Figure 8 shows an idealized image of monitoring a cryoablation procedure using an EBUS device 110. The image region 114 of the EBUS device 110 includes tissue 120. The cryoprobe 130 is monitored as it is percutaneously inserted into the target tissue 120, and then the ultrasound transducer 112 tracks the formation of the ice ball 520.

[0029] Unfortunately, this idealized image is not realistic. This is because the ice ball 520, due to its frozen state, is an extremely high echogenicity to ultrasonic energy. In fact, differences in physical properties between thawed and frozen tissue, including changes in tissue density and the resulting changes in the speed of sound propagating within the tissue, create an acoustic impedance mismatch, causing virtually all ultrasonic energy to be reflected by the ice ball 520. Furthermore, the ice ball 520 itself absorbs ultrasonic energy far more efficiently than unfrozen tissue. Therefore, as shown in Figure 9, the reflective properties of the ice ball 520 produce a clear image of the ice ball surface 920 closest to the ultrasonic transducer 112, but the ultrasonic energy is virtually unable to penetrate beyond this surface 920. This creates an acoustic shadow 930 behind this surface 920, so the resulting ultrasonic image does not show the tissue or structure behind the surface 920. This acoustic shadow 930 is shown as a shadow line 930 in the drawing. Furthermore, elements not included in the acoustic shadow 930 are also shown within this image region 114; in Figure 9, a portion of the target tissue 120 and a portion of the freezing probe 130 are included in this image region 114.

[0030] Figure 9 shows a single image region 114 at a specific point in time. However, as described above, multiple slices 410 are generated by rotating the EBUS device 110, and these slices can be combined to generate a 3D image or 3D model. Furthermore, each slice 410, including the ice ball 520, is similarly affected by the acoustic shadow 930. Therefore, the 3D image / model displays only the surface 920 of the ice ball 520 as seen from the viewpoint 910 determined by the EBUS device 110. As a result, the practitioner can confirm that the ice ball 520 was formed by the freezing probe 130 and that a portion of the target tissue 120 remains untablated on this side of the ice ball surface 920. However, the practitioner cannot confirm whether the distal portion of the target tissue 120 has been properly ablated because they cannot see the acoustic shadow 930 that has occurred on the other side of the immediate surface 920 of the ice ball 520.

[0031] While it is possible to wait for the ice ball 520 to thaw before imaging the ablated tissue, waiting for thawing does not provide useful guidance on whether the process should be continued for a longer period during the freezing process. To overcome this constraint, it is possible to generate an approximation 1000 of the ice ball 520, as shown in Figure 10. This approximation 1000 is generated by the computer system 140 based on information about the visible surface 920 of the ice ball 520 acquired by the EBUS device 110. In Figure 10, this surface 920 is illustrated along with the axis 1010 of the freezing probe 130. This axis 1010 is defined by examining the six degrees of freedom sensors of the freezing probe 130. This information makes it possible to determine the position and orientation of the tip 132 of the freezing probe 130, which is then used to set the axis 1010 in the same 3D space as the identified surface 920.

[0032] Once axis 1010 is identified, each position in 3D space on the visible surface 920 is reflected across axis 1010, as indicated by arrow 1020. In 2D space, this reflection generates an approximate opposite position on the invisible surface 1030. To achieve this, positions on the visible surface 920 are compared to axis 1010. A line segment perpendicular to axis 1010 is identified between axis 1010 and a point on the peripheral surface. Then, an opposite line segment of the same length is used to approximate a point located on the hidden, invisible side of the ice ball. A sufficient number of points are "mirrored" across the freezing probe axis to generate an approximate position of a large segment of the hidden, invisible periphery. This is then combined with points on the visible surface to generate a model of the ice ball.

[0033] It should be noted that this mirroring, or reflection, is performed in three-dimensional space. Figure 11 shows the reflections 1020 at each point across axis 1010 when axis 1010 is viewed downward in the axial direction. The invisible surface 1030 is generated by the reflection 1020 process and then combined with the visible surface 920 to generate the iceball model 1000 520.

[0034] Next, as shown in Figure 12, the model 1000 can be presented to the practitioner via a user interface 1200 generated on the display 150 by the computer system 140. While the user interface 1200 can present the 3D model 1000 through known visualization techniques, for the sake of simplicity in this diagram, the interface 1200 shows only 2D slice images of the model 1000. The model 1000 is shown within the rendering unit 1210 of the live image area 114 of the EBUS device 110. Since the computer system 140 has complete knowledge of the location of the target tissue 120, the location of the abnormal tissue 1220 is further displayed in the same space as the iceball model 1000. In this way, the practitioner can see the iceball 520 on the live interface 1200 and compare its current size, shape, and location to the target tissue 120. As the size of the iceball 520 increases during the freezing process, the size of the surface 920, as seen by the ultrasonic transducer 112, also increases accordingly. The computer system 140 identifies this change, adjusts the approximate position of the invisible surface 1030 using the new position of the surface 920 in the reflection process 1020, and further displays the modified model 1000 on the interface 1200 in near real time.

[0035] It should be noted that Model 1000 of the ice ball 520 cannot reproduce the round portion of the ice ball 520 located far from the tip 132 of the freezing probe 130. Sufficient information is obtained from the visible surface 920. As a result, Model 1000 of the ice ball 520 has a flat portion instead. This is not a requirement of the modeling process, but it demonstrates the limitations of the reflection process 1020. These modeling steps may include additional steps to generate a more rounded portion located far from the tip 132 based on actual observation data and the diameter of the flat portion.

[0036] In one embodiment, the interface 1200 is displayed on a live view of the visual information observed by the ultrasound transducer 112. Thus, a standard ultrasound screen is displayed in live mode up to the visible surface 920 of the iceball 520. However, instead of displaying the acoustic shadow 930 on the interface, the computer system 140 displays the invisible portion of the iceball 520 and the target tissue 120 by superimposing a portion of the abnormal tissue location 1220 and the model 1000. This can be done using either a 2D live ultrasound image or a 3D live ultrasound image.

[0037] As described above in relation to Figures 6 and 7, the outer surface of the ice ball 520 is not as important to the practitioner as the -40°C isotherm 600 during the first freezing process and the -20°C isotherm 610 during the second freezing process. This is because these two boundaries define the area of ​​tissue that can be considered fully ablated. This boundary is represented as the internal isotherm 1230 in interface 1200. The computer system 140 is capable of monitoring the freeze-ablation process, including the freezing and thawing of the tissue. Thus, the computer system 140 recognizes whether the current freezing process is the first freezing (meaning the -40°C isotherm 600 is the effective ablation region) or the second freezing (meaning the -20°C isotherm 610 is the effective ablation region). In either case, the approximate effective ablation region 1230 is further included in interface 1200. This allows the practitioner to continue the freezing process as appropriate to ensure that the entire target tissue 120 is fully ablated. Alternatively, the practitioner can confirm that continued freezing is inappropriate and that the unablated target tissue 120 should be ablated after repositioning the freezing probe 130 or after placing an additional freezing probe 130.

[0038] Process 1300 Each of the steps described above can be incorporated into a process or method 1300, as shown in the flowchart in Figure 13. Before the start of this method, a 3D model of the patient is generated using a standard imaging technique, such as a CT or MRI scan. The patient is then registered in this 3D model by generating an electromagnetic field around the patient and using an EM sensor.

[0039] The first step 1305 in Method 1300 is to position the EBUS device 110 within the tracheal and bronchial tree of patient 100 so as to be positioned adjacent to the target tissue 120. In step 1310, the ultrasound transducer 112 of the EBUS device 110 images the target tissue 120. This image data can be integrated into a 3D model of the patient. Positional information acquired from the EM sensor 116 on the EBUS device 110 may provide sufficient detail regarding the position of the target tissue 120 to allow for fine-tuning of the alignment between the 3D model and the patient at this point.

[0040] In step 1315, the cryoprobe 130 is percutaneously inserted into the target tissue 120. As will be described in more detail below, in some cases, multiple cryoprobes 130 may be inserted into the target tissue 120 to form ice balls 1430 of different shapes and sizes. This insertion may be guided by image data acquired by the ultrasound transducer 112. This live image data may be displayed by the computer system 140. At this point, as described above in relation to Figure 4, the EBUS device 110 may be rotated to generate multiple image slices 410. These multiple slices are combined together in step 1330 to generate a 3D image and 3D model of what was captured by the ultrasound transducer 112 of the EBUS device 110.

[0041] In step 1320, freezing of the target tissue 120 is initiated using the freezing probe 130 and is still monitored by the ultrasound transducer 112. This is achieved in step 1325. The EBUS device 110 can monitor the formation of the ice ball 520 and its position relative to the target tissue 120. Due to the nature of the formed ice ball 520, the EBUS device 110 cannot form an image of the other side of the visible surface 920 of the ice ball 520 due to the acoustic shadow 930 generated by the freezing outer surface 620 of the ice ball. Nevertheless, the basic ultrasound images generated by steps 1305-1330 can be very useful in monitoring the cryoablation procedure.

[0042] To overcome the acoustic shadow 930 challenge, step 1335 identifies the axis 1010 of the freezing probe 130. More specifically, the position and orientation of the tip 132 of the freezing probe 130 are used to form this axis 1010. This position and orientation are determined by analyzing an EM sensor located on the tip 132 of the freezing probe 130. In step 1340, each position in 3D space is identified on the visible surface 920 of the ice ball 520. In this case, these 3D positions are reflected across the axis 1010 to identify points located on the hidden surface 1030. This reflection is made perpendicular to the axis 1010, and the invisible surface 1030 is considered to be formed at a point on the visible surface 920 and equidistant from the axis 1010 at the reflection point on the opposite side of the axis 1010. In step 1345, the 3D positions of the visible surface 920 are combined with determined points on the hidden surface 1030 to form a 3D model 1000 of the ice ball 520. Not all points on the visible surface 920 need to be reflected in this way; only a sufficient number of representative samples are needed to identify the shape of the ice ball 520. The 3D model 1000 can approximate the positions between selected 3D positions on the visible surface and reflection points on the hidden surface.

[0043] In step 1350, it is necessary to select an appropriate temperature for effective ablation. As mentioned above, during the first freezing of the tissue, only the portion of the ice ball 520 that maintains a sustained temperature of -40°C can be reliably destroyed. Consequently, if this is the first freezing, a temperature of -40°C is selected. If this is the second freezing, complete tissue destruction is expected to occur at higher temperatures, such as -20°C to -30°C. Therefore, if this is the second freezing, a higher temperature of -25°C is probably selected. Next, an isotherm 1230 of the selected temperature is added to the model 1000 of the ice ball 520. This isotherm 1230 needs to be approximated based on known temperature fluctuations at the edge of the ice ball 520 during cryoablation. For example, the distance between the periphery of the ice ball 520 and the -40°C necrotic zone is generally acceptable to be 10 mm or less. Through appropriate testing, it is possible to establish a direct relationship between the distance inside the ice ball 520 and the tissue temperature at that location. This test must be performed during the active freezing session because the temperature curve within the ice ball 520 can change significantly after the freezing process is complete or, for example, during the active thawing process. For example, the -40°C isotherm can be considered to be located 8 mm inward from the periphery of the ice ball 520, while the -25°C isotherm can be considered to be located 5 mm inward from the periphery of the ice ball 520. In step 1355, this selected isotherm is added to the Model 1000 of the ice ball 520.

[0044] In some embodiments, the selected isotherm is not added to Model 1000 of the ice ball 520 until the specified temperature has been maintained for a given period of time. As described above, according to the current understanding, in order to consider that the tissue is completely ablated during at least the first freezing process, a temperature of -40°C must be maintained for 3 minutes. The computer system 140 can monitor which part of the ice ball 520 has reached this temperature by using the distance specified in the previous paragraph, and only after this temperature has been maintained for a suitable period of time can the selected isotherm be added to Model 1000.

[0045] In step 1360, the computer system 140 presents the operator with an interface 1200. More specifically, the location of the model 1000 of the ice ball 520 is shown on the user interface 1200, along with the location of the selected isotherm 1230 and the modeled location 1220 of the target tissue 120. Furthermore, a live ultrasound image may be displayed on this interface 1200 up to the visible surface 920 of the ice ball 520. The ice ball model 1000, the selected isotherm 1230, and the modeled location 1220 of the target tissue 120 are then shown in the region constituting the acoustic shadow 930. Additionally, the ultrasound image may be complemented to highlight the visible contours of the visible surface 920 of the ice ball 520 and the target tissue 120.

[0046] In some embodiments, programming on one or more of the computer systems 140 compares an iceball model 1000, or more specifically, a generated selected isotherm 1230, with the size and shape of the abnormal tissue location 1220. The programming then identifies the portion of the target tissue outside the selected isotherm 1230 (which defines the effective therapeutic area of ​​the ablated tissue region) and then visually highlights the portion of the abnormal tissue location 1220 located outside this effective therapeutic area by modifying the user interface 1200. This visual highlighting can be achieved through various visual characteristics. For example, the user interface 1200 may distinguish these portions by using different colors, different intensities, or flashing or other periodic changes in the display.

[0047] Next, in step 1365, the practitioner modifies their planned freezing process as a result of the display in the user interface 1200. For example, the user interface 1200 may indicate that the entire target tissue 120 may be completely ablated by showing an abnormal tissue location 1220 completely surrounded by the selected isotherm 1230. As a result, this freezing process may be completed earlier than originally expected. By preventing over-freezing, ablation of healthy tissue is prevented. On the other hand, if the selected isotherm 1230 cannot surround the abnormal tissue location 1220, the user interface 1200 may indicate that additional freezing beyond what was planned is required to completely ablate the target tissue 120.

[0048] Step 1370 indicates that the interface 1200 is updated in near real-time during the freezing process so that it has the information necessary for the practitioner to know whether it is possible to stop the current freezing process or whether the freezing process should be continued in order to completely ablate the target tissue 120.

[0049] Step 1375 indicates that this method 1300 can be used across multiple freezing cycles. As described above, step 1350 selects an appropriate temperature for the current state of the entire ablation procedure. This requires that method 1300 be able to recognize when the first freezing process will stop, when the first ice ball 520 will thaw, and when the second freezing process will begin. This recognition process occurs in step 1375. Such identification is relatively easy to program into the computer system 140, since the steps described above are designed to identify the periphery of the ice ball 520. Thus, after the ice ball 520 has been detected, grown, and disappeared, the computer system 140 recognizes that the appearance of a new ice ball 520 is the result of the second freezing process. Method 1300 then terminates in 1380.

[0050] Note that in Figure 13, steps 1370 and 1375 are illustrated as occurring chronologically after the other steps of Method 1300. This differs from the actual implementation of these steps. For example, the update in step 1370 requires the continued implementation of steps 1325-1365, while the second freeze for the same organization detected in step 1375 occurs during the continued implementation of steps 1320-1370. These steps 1370 and 1375 are presented at the end of Method 1300 solely for the purpose of visually demonstrating that these elements 1370 and 1375 constitute part of the other steps of Method 1300.

[0051] Application of multiple freezing probes Depending on the situation, it may be necessary to form ice balls of different shapes to match the shape and size of the target tissue 120. In this situation, multiple freezing probes may be inserted into different parts of the tissue 120. In Figure 14, the first freezing probe 130 is joined with the second freezing probe 1410 and the third freezing probe 1420. These freezing probes 130, 1410, and 1420 may be inserted into the target tissue 120 using an introduction cannula, but this is not mandatory. When the three freezing probes 130, 1410, and 1420 are cooled, they cooperate to form a single ice ball 1430 with an integrated but irregularly shaped surface 1432. Some of these freezing probes 130, 1410, and 1420 may operate at different temperatures, with slightly higher temperatures having a lower freezing effect. Furthermore, the manufacturing process of the freezing probes 130, 1410, and 1420 can influence the shape of the resulting ice ball (for example, some probes produce a more spherical shape). By using different designs and temperatures among the freezing probes 130, 1410, and 1420, it is possible to intentionally shape the resulting ice ball 1430 into a form that more effectively kills the target tissue 120 while minimizing damage to surrounding tissue.

[0052] The process for monitoring the formation of this irregularly shaped ice ball is the same process 1300 described above. Steps 1305-1325 are used to insert the freezing probe and monitor the freezing process. However, because the ice ball 1430 is irregularly shaped, the likelihood of the reflection process generating a model that accurately reflects the shape of the ice ball 1430 is reduced. However, if multiple freezing probes 130, 1410, and 1420 are positioned almost coplanar with the ultrasonic transducer 112 of the EBUS device 110 and used in a symmetrical pattern around the axis of the central freezing probe 130, then process 1300 can be applied.

[0053] As shown in Figure 15, the ultrasonic transducer 112 of the EBUS device 110 can only recognize the near-visible side 1500 of the formed ice ball 1430. The transducer 112 can image the fact that the near portion of the target tissue 120 has not been ablated, but it cannot recognize the far side of the ice ball 1430 due to the acoustic shadow 1510 generated by the ice ball 1430. However, the computer system 140 can identify an axis 1520 representing the angle and position of the central freezing probe 130. This axis can be used to generate a user interface 1600, as shown in Figure 16. This user interface 1600 shows the image portion 1610 of the target tissue 120 and the generated model 1620 of the ice ball 1430. Furthermore, the user interface 1600 shows selected isotherms 1630 indicating the area of ​​current effective ablation.

[0054] The above process 1300 and the resulting models 1000 and 1620 are primarily designed to provide live monitoring of cryoablation procedures. After the ice ball 520 (or ice ball 1430) has thawed, the EBUS device 110 can image the thawed and ablated tissue. This tissue can be directly visualized by the ultrasound transducer 112 of the EBUS device 110 and then compared to the target tissue 120. However, waiting for thawing to occur means that no assistance is provided to the practitioner during the cryoablation procedure. The above method and apparatus can provide images that directly assist the practitioner during the freezing process of the procedure.

[0055] Numerous features and advantages of this disclosure are evident from the above description. Numerous modifications and variations will be readily conceivable to those skilled in the art. Such modifications are possible, and therefore this disclosure is not limited to the exact same structure and operation as those illustrated and described. Rather, this disclosure is limited only by the appended claims. [Explanation of Symbols]

[0056] 100 patients 110 Linear Endobronchial Ultrasound (EBUS) Device 112 Ultrasonic Transducer 114 Image area 116 Electromagnetic (EM) Sensors 120 Target tissue 130 Freezing probe 132 Tip 140 Computer Systems 150 displays 160 Navigation System 202 Airway wall 300 Ultrasound Catheter 302 Tip 310 Linear Transducer Array 320 flat surface 322 positions 330 Remaining portion 340 Electromagnetic (EM) Sensors 342 Electronic device packages 350 Introduction Catheter 400 RPM access 410 image region slices, image slices 420 Peripheral area 520 Ice Balls 600 central area 610 Shaded area 620 outer surface, frozen outer surface 910 Perspective 920 Ice ball surface, visible surface 930 Acoustic Shadow, Shadow Line 1000 approximations, models, 3D models 1010 axis 1020 Reflection, reflection process, arrow 1030 Invisible surface, hidden surface 1200 User Interfaces 1210 Imaging section 1220 Abnormal tissue location, modeled location 1230 Inner isotherms, approximate effective ablation region 1410 Second freezing probe 1420 Third freezing probe 1430 Ice Ball 1432 Irregularly shaped surface 1500 Nearby visible side 1510 Acoustic Shadow 1520 axis 1600 User Interfaces 1610 Imaging section 1620 Model 1630 Selected isotherms

Claims

1. A method for treating patients, a) The step of positioning an ultrasound device in a fixed location within the trachea and bronchial tree of the patient in order to image the target tissue, b) The step of placing a cryoprobe in the target tissue, c) A step of generating an ice ball by cooling the freezing probe, d) During the step of generating the ice ball, i) By rotating the ultrasound device, multiple 2D image slices of the target tissue are generated. ii) Using a computer to combine the multiple 2D image slices to identify the visible surface of the ice ball, iii) Using the computer, generate a 3D model of the ice ball based on the visible surface, iv) Using the computer, generate isotherms for the 3D model at a selected temperature identified for effective ablation, and v) Using the computer, the 3D model of the ice ball and the isotherms are displayed on the user interface. The steps to perform Methods that include...

2. The method according to claim 1, wherein the ultrasound device is a linear intrabronchial ultrasound (EBUS) device.

3. The method according to claim 2, wherein the linear intrabronchial ultrasound (EBUS) device has a plurality of ultrasonic transducer elements, and further, the plurality of ultrasonic transducer elements are of a type selected from the group consisting of PZT-based transducers, pMUT-based transducers, and cMUT-based transducers.

4. The method according to claim 1, further comprising the step of displaying the 3D model of the ice ball and the target tissue rendering section relative to the isotherm on the user interface.

5. The method according to claim 1, further comprising the steps of identifying a portion of the target tissue outside the isotherm by comparing the 3D model of the ice ball on the computer with the recognized size and shape of the target tissue, and displaying the identified portion of the target tissue on the user interface using distinguishable visual characteristics.

6. The method according to claim 1, wherein the distal end of the ultrasonic device further comprises an electromagnetic sensor that receives an electromagnetic signal for locating the distal end in an electromagnetic field, the method further comprising the step of using the electromagnetic signal to display the 3D model of the ice ball on the target tissue visualization section on the user interface.

7. The method according to claim 1, wherein the 3D model of the ice ball and the isotherms displayed on the user interface change over time in accordance with the increase in the size of the ice ball.

8. The method according to claim 1, further comprising the step of terminating the generation of the ice ball before the expected end time when the user interface indicates that the isotherm surrounds the target tissue.

9. The method according to claim 1, further comprising the step of continuing to generate the ice ball beyond the expected end time if the user interface indicates that the isotherm does not surround the target tissue.

10. Generating the aforementioned 3D model is i) Identifying the axis of the freezing probe, ii) Identifying the 3D position of the ice ball on the visible surface, iii) Identifying a point on the hidden surface of the ice ball by reflecting the identified 3D position across the axis of the freezing probe, iv) Combining the 3D position on the visible surface with the identified point on the hidden surface The method according to claim 1, including the method described in claim 1.

11. The method according to claim 10, wherein the reflection of the identified 3D position across the axis of the freezing probe is performed perpendicular to the axis, and the point is located equidistant from the axis as the identified 3D position.

12. The method according to claim 10, wherein only a selected number of 3D positions are reflected, and the 3D model approximates the positions between the selected number of 3D positions on the visible surface and the points on the hidden surface.

13. To generate the isotherm for the 3D model at the selected temperature, i) Identifying a location at a known distance from the periphery of the ice ball that is known to be below the selected temperature, ii) Identifying the isotherm located at a known distance from the periphery of the ice ball. The method according to claim 1, including the method described in claim 1.

14. The method according to claim 13, wherein the known distance is determined by a temperature test in a cryoablation test.

15. The method according to claim 13, further comprising the requirement that the temperature below the selected temperature be maintained for a predetermined period of time.

16. The method according to claim 15, wherein the predetermined time period is at least 3 minutes.

17. a) Freezing probe and b) Ultrasonic devices and, c) Display and, d) A computer system in communication with the freezing probe, the ultrasonic device, and the display, wherein the computer system has a processor that operates under programming, and the programming is transmitted to the computer system i) Receiving a 2D image slice of target tissue within the patient from the ultrasound device as the ultrasound device rotates within the patient, wherein the 2D image slice includes a portion of the ice ball formed by the freezing probe. ii) By combining the 2D image slices, the visible surface of the ice ball can be identified, iii) Generating a 3D model of the ice ball based on the visible surface, iv) With respect to the 3D model of the ice ball, generate isotherms at a selected temperature identified for effective ablation, v) To generate a user interface on the display that shows the 3D model of the ice ball and the isotherms. A computer system to carry out this task A system that includes these features.

18. The system according to claim 17, wherein the computer system comprises a model of the target tissue aligned with the patient, and the user interface further displays a rendering section of the target tissue relative to the 3D model of the ice ball and the isotherm.

19. The system according to claim 18, wherein the programming further causes the computer system to identify a portion of the target tissue located outside the isotherm by comparing the 3D model of the ice ball with a known size and shape of the target tissue, and further, the user interface indicates the identified portion of the target tissue using distinguishable visual characteristics.

20. The aforementioned programming is i) Identifying the axis of the freezing probe, ii) Identifying the 3D position of the ice ball on the visible surface, iii) Identifying a point on the hidden surface of the ice ball by reflecting the identified 3D position across the axis of the freezing probe, iv) Combining the 3D position on the visible surface with the identified point on the hidden surface The system according to claim 17, wherein the computer system is made to perform the above, thereby causing the computer system to generate the 3D model of the ice ball.

21. The system according to claim 20, wherein the identified 3D position is reflected perpendicularly from the axis across the axis of the freezing probe, and the point is equidistant from the axis as the identified 3D position.

22. The system according to claim 20, wherein only a selected number of 3D positions are reflected, and the 3D model of the ice ball approximates the positions between the selected number of 3D positions on the visible surface and the points on the hidden surface.

23. To generate the isotherm for the 3D model at the selected temperature, i) Identifying a location at a known distance from the periphery of the ice ball that is known to be below the selected temperature, ii) Identifying the isotherm located at a known distance from the periphery of the ice ball. The system according to claim 17, including the system described in claim 17.

24. The known distance is determined by a temperature test in a cryoablation test, according to claim 23.

25. The system according to claim 23, further comprising the requirement that the temperature below the selected temperature be maintained for a predetermined period of time.

26. The system according to claim 25, wherein the predetermined time period is at least 3 minutes.

27. A computer system that communicates with a freezing probe, an ultrasound device, and a display, a) Processor, b) The processor, i) Receiving a 2D image slice of target tissue within the patient from the ultrasound device as the ultrasound device rotates within the patient, wherein the 2D image slice includes a portion of the ice ball formed by the freezing probe. ii) By combining the 2D image slices, the visible surface of the ice ball can be identified, iii) Generating a 3D model of the ice ball based on the visible surface, iv) With respect to the 3D model of the ice ball, generate isotherms at a selected temperature identified for effective ablation, v) To generate a user interface on the display that shows the 3D model of the ice ball and the isotherms. A program and A computer system equipped with the following features.

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