RO136019A0 - Motion compensation system and method for electromagnetic navigation in coronary angioplasty - Google Patents

Abstract

The invention relates to a motion compensation system and method for electromagnetic navigation in coronary angioplasty. According to the invention, the system comprises a device for electromagnetic positioning in space, having a low magnetic field generator (4), which is placed near the patient during the investigative procedure, so that the anatomical area of interest is included in the magnetic field volume, a control unit (5), which interprets the electrical signals received from some sensors, and transforms them into coordinates and angles of rotation, an active marker (3) intended to be placed on the patient's back, a guiding tool (1) with a position sensor, and a computer (2) running a program product, the system allowing real-time navigation of the tool (1) inside the patient's coronary tree using a virtual coronary angiography and allowing corrections of the heart and lung movements.

Description

RO 136019 AO

MOTION COMPENSATION SYSTEM AND METHOD FOR ELECTROMAGNETIC NAVIGATION IN CORONARY ANGIOPLASTY

The invention relates to a system for coronary angioplasty that improves the navigation of a stenting guide or an interventional catheter in the coronary arterial system of the heart to the vicinity of suspected coronary stenoses to subsequently place an intravascular stent. The system uses an electromagnetic positioning system for the real-time position of the tip of the guide or catheter and represents it on a three-dimensional virtual model correlated with the patient's anatomy. For guidance in the coronary arteries, the system renders a virtual coronary image corresponding to the position of the instrument. During navigation to the target to be investigated, the system must take into account the patient's voluntary chest movement, respiratory movement and heart movement to correlate the imaging data with the electromagnetic positioning system that compensates for the patient's movement. Deviation from the set path can be automatically corrected by the system using the collision check with the inner surface of the virtual coronary artery system and possibly the central path of a) coronary arteries. The placement of the final stent is done with the help of the classic balloon and expandable stent system, which contains in the lumen or the guide with a position sensor at the tip.

The invention describes a coronary navigation system with electromagnetic tracking intended to assist medical procedures for coronary angioplasty using coronary CT angiography. By medical procedures, we consider coronary artery stenting and balloon dilation for the treatment of coronary artery disease, or heart valve replacement, such as transthoracic aortic valve implantation (TAVA) or stent placement in the lower limbs.

Coronary heart disease (CHD), also known as chronic ischemic heart disease (CHD) or ischemic heart disease, involves reduced blood flow to the heart muscle due to the formation of plaques/deposits in the arteries of the heart.

Coronary CT Angiography xCoronary CT angiography (CTA) is the use of computed tomography angiography (CT Angio) to evaluate the coronary arteries of the heart. The patient receives an intravenous injection of radiocontrast and then the heart is scanned using a high-speed CT scanner, allowing doctors to assess the degree of occlusion of the coronary arteries, usually to diagnose coronary artery disease. (see Figure 1)

Figure: CTA example

Faster CT machines, due to their multidetector capabilities, have made imaging of the heart and circulatory system very practical in a number of clinical settings. capacity

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Page | 2 faster enabled imaging of the heart with minimal involuntary movements, which creates use on the image, and has a number of practical applications. It is useful in the diagnosis of suspected coronary artery disease, in the follow-up of coronary artery bypass grafting, in the evaluation of valvular heart disease, and in the evaluation of cardiac masses.[2]

The positive predictive value of cardiac CTA is approximately 82% and the negative predictive value is approximately 93%.

In addition to diagnostic abilities, cardiac CTA contains important prognostic information. Severity of stenosis and extent of coronary artery disease are important prognostic indicators. However, one of the unique features of cardiac CTA is that it allows visualization of the vessel wall in a non-invasive manner. Therefore, the technique is able to identify features of coronary artery disease that are associated with the development of acute coronary syndrome.

CTA can also be used to evaluate and plan heart valve repair, such as TRAY procedures.

Treatment of Coronary Artery Disease in Vos and Wang concluded that in 2015, CAD affected 110 million people and resulted in 8.9 million deaths. It accounts for 15.6% of all deaths, making it the most common cause of death globally. The risk of death from CAD for a given age decreased between 1980 and 2010, particularly in developed countries. The number of CAD cases for a given age also declined between 1990 and 2010. In the United States, in 2010, about 20% of those over 65 had CAD, while it was present in 7% of those aged 45 to 64 and 1.3% of those 18 to 45. Rates were higher among men than among women of a given age.

Percutaneous coronary intervention, or angioplasty, is a procedure to open narrowed or blocked blood vessels that supply blood to the heart. These blood vessels are called coronary arteries.

Figure 2: Catheterization lab and an example of angioplasty image

A coronary artery stent is a small tube with metal mesh that extends inside a coronary artery. A stent is often placed during or immediately after angioplasty. It helps prevent the artery from closing again. A drug-eluting stent has a drug embedded in it that helps prevent the artery from closing long-term.

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P a g i n a | 3X

The doctor will insert a flexible tube (catheter) into an artery. Sometimes, the catheter will be placed. in the patient's arm or wrist, or in the upper leg area (groin). The patient will be awake during the procedure.

The doctor will use live X-ray images to carefully guide the catheter up into the heart and arteries. Liquid contrast (sometimes called "dye") will be injected into your body to highlight the flow of blood through the arteries. This helps the doctor see any blockages in the blood vessels leading to the patient's heart (see Figure 2).

A guidewire is moved into and over the blockage. A balloon catheter is pushed over the guidewire and into the blockage. The balloon at the end is blown (inflated). This opens the blocked vessel and restores proper blood flow to the heart.

A wire mesh tube (stent) can then be placed in this blocked area. The stent is inserted together with the balloon catheter. It expands when the balloon is inflated. The stent is left there to help keep the artery open.

Problems with X-ray angioplasty in “Huang PS, Chen ZC, Tang KT, Chang WT. Assessment of radiation exposure to physicians during angioplasty. for hemodialysis access dysfunction. Acta Cardiol Sin. 2019;35(l):27-31. doi:10.6515/ACS.201901 35(1).20180730A" it is concluded that one of the important risks of angioplasty is radiation exposure. depending on a multitude of factors (eg, the complexity of the coronary artery lesion, body mass index), the patient is exposed to varying doses of radiation, from lower values to sometimes large ones. Adequate preoperative planning could reduce procedure time and, implicitly, contribute to dose reduction. In addition to patients, invasive cardiologists and angiologists are exposed to long-term, low-dose occupational radiation. Because radiation accumulates over the years, even small doses contribute to the risk of malignancy, hereditary effects, and tissue reactions.

Figure 3.-Exposure of the user of the angiograph in the environment! radiant

It is often difficult for practitioners and interventionalists to wear the heavy lead aprons and thyroid shields. These lead garments must be checked frequently for cracks or else they are ineffective. It is recommended that physicians insist that all lead aprons be dated, when they were last purchased and checked, that they choose the "newest" apron available, and that they encourage all colleagues to close their lead after use to extend longevity . Also, the association between discomfort, fatigue and ease of movement while wearing different types of lead aprons has not been widely studied, and it is well known that these aprons create a lot of problems for doctors. Also, some studies have shown that

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P a g i n a | 4 Sixty-three percent of shields and aprons had detectable surface lead, which was associated with visual appearance, shield type, and storage method. Shields containing lead are a recently identified, potentially widespread source of lead exposure in the healthcare industry.

This invention will overcome all the previously described problems.

CardioCTNav system

The invention consisted of a software platform, based on computed tomography and medical electromagnetic tracking, for preoperative planning of the stenting procedure and for real-time guidance of stent navigation along coronary arteries or other blood vessels to the area of stenosis in during the intervention.

This platform, called CardioCTNav, contributes significantly to the reduction of procedure time and, also very importantly, could reduce or even eliminate the need for fluoroscopy during the intervention. In this way, the patient and the interventional cardiologists will be exposed to a much lower time and radiation dose than in "traditional" angiographic intervention, in a user scenario over the intended software application, the starting point is cardiac computed tomography (CT ) of the patient. in the analysis phase, the platform will enable fluid dynamics simulations based on Lattice Boltzmann methods to assess coronary artery stenosis, mark an area of interest and plan an optimal trajectory for stenting navigation. during the actual intervention, using a set of electromagnetic sensors placed on the patient and the medical instrument, the position of the stent will be visualized in real time in a virtual 3D scene relative to a 3D image of the patient reconstructed from CT. In this way, the physician will receive significant visual guidance in navigating the stent to the area of interest. In this scenario, "traditional" radiation procedures would be used only in the initial phase (CT), to acquire the image of the patient further used for planning and electromagnetic navigation, and in the final phases (CT or angiography), after the flexibility of catheter insertion , to confirm stent position.

The advantages of applying the invention, described in this patent, consist of:

- the possibility of biopsy guidance in the culprit areas of the coronary arteries,

- reducing the time of performing the medical coronary angioplasty procedure; - increasing the degree of success and quality of angioplasty procedures;

- integration of the system with existing equipment and instruments (eg classic stent and balloon devices and insertion guidewires);

- faster implementation of the centerline-based navigation algorithm that eliminates the initial step of selecting the culprit coronary artery.

An embodiment of the invention is shown below in connection with Figures 4-7, which represent:

- figure 4 - Medical cart with navigation system for coronary angiography, according to the invention;

- figure 5 - Scheme of the navigation system

- figure 6 - The Planning screen of the software application;

- figure 7 - Navigation screen of the software application;

- figure 8 - Procedure steps

- figure 9 - Diagrams with respiratory and cardiac movement

- figure 10 - Assembly of guidance instruments

The coronary navigation system according to the invention consists of the following elements: - an electromagnetic device for positioning in space, consisting of a low-intensity magnetic field generator (see Fig. 5), which is positioned close to the patient during the investigative procedure, so that the anatomical area of interest, which will be investigated, is included in

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Page | 5 the volume of the magnetic field; a control unit, which interprets the electrical signals received from some sensors and transforms them into coordinates and rotation angles (position vector and orientation), relative to the magnetic field generator;

- a guide/catheter instrument (see Fig. 5 ) for navigation to the calcified plaque and for the stent placenta, tubular, flexible, of equal length and diameter smaller than that of the internal channel of the stent device. At the proximal end of the guide wire, an electromagnetic position sensor is inserted and fixed, whose electrical wires connected to a cable and a specific connector pass through a tube and exit through the distal end of the instrument (see fig. 10).

- an active adhesive marker will be attached to the back skin of the patient's trunk (see Fig. 5 ) before the angioplasty procedure, between the patient's two shoulder blades.

- a compact computer running a dedicated application, with two main screens (see fig. 6 and 7), having the general architecture and the steps in the clinical flow shown in fig. 8, and which is developed to command the execution of the following operations:

i. reads several sequential imaging sections of a patient cardiac CT scan volume, in standard DICOM (Digital Imaging and Communications in Medicine) format;

ii. to remove the lungs and bones of the chest and to recognize the heart and the system of coronary arteries by the segmentation method of growing the region and constructing their surfaces, to make a three-dimensional digital model of the scanned anatomy that we will hereinafter call the 3D Virtual Volume;

iii. to build the three-dimensional (3D) virtual volume of the heart and coronary arteries (see fig. 6) of the patient, by the marching cubes method using hardware acceleration The algorithm is applied without the use of intermediate stages of blood vessel extraction, but directly on the initial DICOM data and allows real-time selection of the desired isosurface.

iv. to allow identification on CT sections and the position of the calcified plaque/target, the position of the active marker on the patient volume (see fig.6);

v. propose a path of the guidance tool to the target calcified plaque (see fig. 7) following the centerline path inside the coronary arteries, using search algorithms such as the A Star algorithm and allow the user to modify it;

are you coming. to acquire position data, provided by the sensors embedded in the guidewire instrument and the active marker in the generated magnetic field;

Viii.. The previously generated Virtual 3D Volume is used as input data to generate the virtual coronary image.

ix. Align the 3D virtual volume with the patient's physical space using the active sensor if the patient moves or changes position during the procedure,

x. calculate and display in real time the position of the tool head inside the 3D Virtual Volume, according to the position data provided by its sensor;

xi. to create a virtual section according to the 3D Virtual Volume model, positioned by the axis of the sensor at the end of the instrument and of variable orientation, set by the user;

xii. to calculate and display various data such as distance to calcified plaque, calibration error, other system errors, loss of sensor connection to the system, by sensor exit outside the tracked physical volume.

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Integration of the full system into the proposed coronary navigation CT suite

Figure 5: Schematic of the navigation system

Figure 6: The Planning screen of the software application;

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Figure 7: Navigation screen of the software application;

Figure 8: 4-step navigation time diagram of the coronary angiography system according to the invention;

Uncoupled movement of the patient's heart and chest in ; exhale(E)/inhale(I)

Figure 9: Diagrams with respiratory and cardiac movement

The direction of movement of a patient's lungs, heart, and chest

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Figure 10. The ensemble of the 3 instruments

Using the system according to the invention requires the user to complete the following steps:

1. To use the core of the software platform which contains some basic functionality

a) It will load medical information from various formats (Dicom, meta images) and render reconstructed 2D/3D images of the patient.

b) It will integrate and control an electromagnetic tracking device - we will use the Aurora NDI EM developed by Northern Digital, connected via a USB port to the computer that will run the software application. This integration means that the software application could recognize the connected tracking device, find the sensors connected to the system, and turn on/off the flow of sensor position and orientation information sent by the tracking device.

2. Will perform a preoperative planning and simulation module integrated into the core software platform

a) .This module extracts from CT (computed tomography) the reconstructed image of the patient's carotid arteries and will allow the identification of the bifurcation points. This type of algorithm is known in medical imaging software as segmentation - we use a version of the segmentation algorithm based on a modified version of the "region growing" algorithm.

A final component of the planning module will be an algorithm that will generate a path within the coronary arteries between a chosen starting point and the desired stent location. Even if there are no multiple possibilities to navigate between two points inside the arteries, this method will allow the interventionalist to simulate in advance the navigation of the stent, to familiarize himself with the geometry of the arteries, to identify the bifurcation points to be passed, to evaluate the distance and time between these points etc. We used a centerline algorithm related to the A* method, between the starting point and the desired target location.

3. To use the navigation module, also integrated in the basic platform, which allows real-time information about the position of the medical instrument to be rendered in 2D / 3D virtual scenes over the reconstructed CT image of the patient. There are several components and algorithms that we will develop in this module.

One of the most important aspects of medical tracking, whether optical or electromagnetic, is the registration (alignment) between two separate coordinate spaces - the actual physical space of the patient (and tracking device) and the virtual space of 2D/3D. patient images reconstructed from tomography. We developed a registration algorithm based on landmark registration, or the Horn method, which requires the selection of two separate sets of three points each, one set in physical space (with the help of the tracker) and the other set in virtual space with the help of software tools and of computer input devices (eg mouse).

To improve the accuracy of the information provided to the interventional physician by the tracking module, we have developed algorithms and methods to correct the initial registration as follows:

Due to inherent errors associated with recording methods, sometimes the visual representation of

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Page | 9 of the sensor in the 2D/3D virtual scenes will be placed outside the arteries. We will "force" the sensor representation to stay inside the artery tubes with a collision detection and resolution algorithm based only on voxels and CT Hounsfield units,

According to the invention, a collision detection and resolution algorithm will be used that will permanently preserve the representation of the medical instrument inside the coronary arteries. It is assumed that initially, before the start of collision detection, the tool is represented inside the surface of blood vessels. The position of the instrument will be provided at discrete times. Also, the surface representation of the blood vessels consists of small triangles. The steps for detecting and resolving collisions are as follows (see Figure 11):

Figure 11. Collision detection overview

Z - given two positions P _t , P _i+Î at two successive moments of time t, (t + 1), the intersection of the segment P _s , P _t +i with the triangles on the surface is evaluated. To avoid too long calculations, the triangles will be grouped into a data structure that will allow only the triangles in the "neighborhood" of the segment to be considered. If no intersection was detected, then the Pt+ta position remained inside the surface.

Z - if the segment P _t , P _t +t intersects a triangle (denoted Tr in Fig. 11 and P^is the point of intersection), then P _t +t is brought from the same side of the triangle Tr as Pt along a "minimum" route (P _t +i P't+t). From the position Pt+1 a line perpendicular to the plane Tr is drawn. The intersection with Tr is denoted by P'Tr and, if the time interval in which two successive positions are provided is small enough, it should be inside the triangle Tr . If not, then further corrections are required (see Fig. 11). From the point P _t draw a parallel to the plane Tr , in the plane (PtPt+iP'îr). The intersection of the two lines "drawn" above represents the corrected position P't+ta of the medical instrument.

□ If the projection of the position P _t +i on the plane Tr is actually outside the triangle Tr (Fig. 11), then the line formed by the points Ρτ _Γ and Ρ'τγ intersects with the perimeter of the triangle , the intersection is denoted Ρτγ). The intersection of the lines (P _t P _t +i) and (Ρι+ιΡτ _Γ ) represents, in this case, the corrected position Pt+ia of the medical instrument.

Claims (3)

RO 136019 AO Page | 1 CLAIMS 1. Navigation system for coronary angioplasty (according to figure l) consisting of the following elements; - an electromagnetic positioning device in space, consisting of a generator (4) of a low magnetic field, which is positioned close to the patient during the investigative procedure, so that the anatomical area of interest to be investigated is included in the volume of the magnetic field, - a control unit (5), which interprets the electrical signals received from some sensors and transforms them into coordinates and rotation angles; - an active marker (3), to be placed on the back skin of the patient's torso; - a guidewire type instrument (1) with a position sensor for orientation at the tip of the guidewire; - a computer (2) running a software product, characterized in that it allows real-time navigation of the instrument (1) inside the coronary tree of the patient using a virtual coronary anoscopy and allows corrections of the movements of the heart and lungs. Figure 1: Navigation system diagram 2. Product control program (figure 2), dedicated to the navigation system in coronary angioplasty, according to claim 1, developed to control the execution of the following operations: i. reads some serial imaging sections of a volume scanned by computed tomography or magnetic resonance imaging, in DICOM (Digital Imaging and Communications in Medicine) standard format; ii. creates a three-dimensional digital model of the scanned anatomy and a three-dimensional virtual model of the heart and coronary system using the marching cube method using hardware acceleration. The algorithm is applied again using the intermediate steps of surface extraction, but directly on the initial DICOM data and allows the real-time selection of the desired isosurface value. iv. allows the localization by selection with the mouse, on the tomographic sections or on the virtual models of several targets (stenoses or plaques) and an active marker used for the registration/fusion between the physical electromagnetic space and the CT space, v. proposes a path of the guidance tool to the site of the culprit stenosis of the affected coronary artery after the path of the central line (figure 4 ) and allows its modification by the user; vi. acquires position data, provided by the sensors embedded in the guidewire instrument and the active marker; are you coming. creates a virtual video camera above the guidewire instrument that presents a real-time virtual coronary image through the three-dimensional virtual model of the coronary artery system, viii, aligns the three-dimensional virtual models with the patient using a single 6DOF active marker placed on the back of the patient's skin trunk, the virtual ones chosen on the three-dimensional models and the real ones on the patient's body, the problem of absolute orientation between the coordinate systems of the two RO 136019 AO Page | 2 < volumes being solved by an algorithm using quatemions for computing the correspondence transformation; ix. calculates and displays on a computer screen on the virtual models, during the procedure, the position of the tip of the guidewire in the patient, according to the position data provided by the electromagnetic sensor; x. creates a virtual plane (coronal, frontal and sagittal plane) through the virtual model of the patient's anatomy, positioned by the three XYZ axes of the sensor at the end of the instrument and of variable orientation, set by the user; xi. allows displaying the cardiac and respiratory motion of the heart and changes the color of the virtual tip of the guide wire from red, which means the least precision, and green, which means the maximum precision of the tip location, based on the tip position in the cardiac cycles and respiratory. xii. when navigating narrow coronary artery tubes, it will continuously display the position of the sensor at the guidewire tip both with the centerline path established in the planning phase, and make adjustments to the position of the guidewire tip by calculating collisions with the inner surface of the coronary artery virtual heart. xiii. according to the invention, a collision detection and resolution algorithm will be used that will permanently preserve the representation of the tip of the guidewire inside the coronaries. It is assumed that initially Figure 2: Product control program Figure 3: Automated centerline of a coronary artery