CN104161546A - Ultrasonic probe calibration system and method based on locatable puncture needle - Google Patents

Abstract

The invention discloses an ultrasonic probe calibration system and method based on a positionable puncture needle. The calibration method includes: S1. Design and manufacture of a calibration model; S2. Extraction of feature points of the calibration model in an ultrasonic image; S3. Solve the calibration transformation matrix for the calibration feature points. The present invention can solve the current ultrasound-guided interventional therapy and the calibration problem of trackable and positioned ultrasound probes in the free-style three-dimensional ultrasound imaging system, so as to obtain more accurate calibration accuracy and more convenient calibration operation, and the accurately calibrated ultrasound can effectively provide three-dimensional ultrasound Improve the quality of reconstructed images and improve the safety and success rate of surgery.

Description

Ultrasound probe calibration system and method based on positionable puncture needle

technical field

The invention relates to the technical field of medical equipment and ultrasonic detection, in particular to an ultrasonic probe calibration system and method based on a positionable puncture needle.

Background technique

In ultrasound-guided interventional therapy and surgery, the spatial position of the ultrasound probe needs to be tracked by a three-dimensional space positioning system, and unified into the same coordinate system with the surgical instruments being tracked at the same time, so that the posture and position of the equipment can be accurately displayed on the ultrasound on the image, presented to the doctor. The technique of tracking the ultrasound probe with a 3D positioning system is also applied to the acquisition and reconstruction of freestyle 3D ultrasound images. In order to be able to track the imaging plane extending from the ultrasound probe, it is first necessary to determine the transformation relationship from the position tracking sensor coordinate system to the ultrasound imaging plane coordinate system. The process of measuring and solving for this transformation is ultrasound probe calibration.

The current main methods for spatial calibration of ultrasound probes are:

A point method for calibration based on intersecting lines or a sphere in a phantom, a surface method for calibration based on a plane phantom, and a method for calibration based on intrinsic feature points of an image. A common method for calibrating an ultrasound probe is to scan an ultrasound phantom with known specific geometric dimensions, such as crossed lines with known specific geometric dimensions placed in a water tank or small spheres arranged according to certain rules. Ultrasound scans these points from multiple angles, and then segments these feature points in the ultrasound image. Since each point specifically corresponds to its known position in the world coordinate system, the overdetermined equation formed by these point sets can be solved by an optimization method.

The second is a method of calibration based on a planar phantom, which places a planar phantom clearly imaged in ultrasound in a water tank, and uses the relevant characteristic straight lines on the plane for calibration. However, its calibration accuracy is limited by the narrow imaging angle and depth, because the thickness and clarity of the planar phantom imaging depend on the scanning depth and ultrasound focus settings during scanning. Another problem is that the propagation speed of ultrasonic waves in water is different from that in human tissue (the propagation speed of ultrasonic waves in human tissue is 1540m/s), so if the result of calibrating the planar phantom in the water tank For human body scanning, there will be certain errors and eventually lead to distortion of the reconstructed image. The usual way to solve this problem is to inject specific substances (such as salt, alcohol or glycerin) into the water tank so that the propagation velocity of the mixed liquid to ultrasonic waves is 1540m/s.

The third calibration method is not to use the phantom, but to directly use the relevant information between the collected ultrasound image frames to estimate. This method needs to track the relative position of the selected feature points in the ultrasound image between the image frames .

Among the existing ultrasonic probe calibration methods, the first type of calibration method based on point phantoms has the following problems: since the thickness of the ultrasonic velocity is limited, it is difficult to align the ultrasonic probe directly to the center of these characteristic spheres, And when the probe is not aimed directly at the sphere, the sphere may also appear on the corresponding ultrasound image. The second type of method based on the phantom has the following problems: the ultrasonic imaging plane is required to pass through the feature plane of the phantom, which requires a high calibration operation for the operator, and the extraction of feature points on the phantom is inconvenient. The problem of the third type of calibration method based on the correlation of image feature points is: because there are many speckle noises in the ultrasound image, it is difficult to accurately segment out the feature points in the image and match them, so the calibration of this type of method The accuracy is relatively low.

Therefore, in view of the above technical problems, it is necessary to provide an ultrasonic probe calibration system and method based on a positionable puncture needle.

Contents of the invention

In view of this, the object of the present invention is to provide a new ultrasonic probe calibration system and method based on a positionable puncture needle.

In order to achieve the above object, the technical solutions provided by the embodiments of the present invention are as follows:

An ultrasonic probe calibration system based on a positionable puncture needle, the system includes an ultrasonic host, a space positioning device connected to the ultrasonic host and a system host, the system host is used for data collection and calibration, and the space positioning device It includes a spatial positioning system host, an ultrasonic probe, and an optical tracking object, and the optical tracking object includes an ultrasonic probe fixture fixedly installed on the ultrasonic probe, a puncture needle and a first spatial positioning sensor fixedly installed on the ultrasonic probe fixture, and a fixed The second spatial positioning sensor installed on the puncture needle.

As a further improvement of the present invention, the first spatial positioning sensor and the second spatial positioning sensor are optical sensors or electromagnetic sensors.

Correspondingly, a method for calibrating an ultrasonic probe based on a positionable puncture needle, the method includes:

S1. Calibration model design and production;

S2. Extraction of calibration model feature points in the ultrasound image;

S3. Solving a calibration transformation matrix according to the calibration feature points extracted from the ultrasonic image.

As a further improvement of the present invention, the calibration model in the step S1 is:

M _TN u _i = M _TR M _RP X _i ,

Among them, u _i is the actual spatial position of _the second spatial positioning sensor on the puncture needle; _Xi is the pixel coordinate of the second spatial positioning sensor on the puncture needle in the ultrasound image; The rigid body transformation matrix of the tracking object; M _TR represents the transformation matrix of the ultrasonic probe relative to the optical tracking object, and M _TR represents the spatial position and orientation information of the ultrasonic probe; M _TN represents the transformation matrix of the point on the puncture needle relative to the real-time ultrasonic probe.

As a further improvement of the present invention, the step S3 is specifically:

The calibration transformation matrix M _RP is solved according to the calibration feature points extracted from the ultrasonic image.

As a further improvement of the present invention, the step S3 is specifically:

The corresponding calibration equation is solved by the method of least squares:

$<span\; class="notranslate">\; [</span>\stackrel{<span\; class="notranslate">\; ~</span>}{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; RP</span>}}}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; arg</span>}\underset{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; RP</span>}}}{\mathrm{<span\; class="notranslate">\; min</span>}}\underset{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; TN</span>}}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; TR</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; RP</span>}}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; |</span>$

As a further improvement of the present invention, the step S2 is specifically:

Hough transform is used to detect the linear features of the puncture needle in the ultrasonic image, and the calibration feature points on the linear features are extracted.

The present invention has the following beneficial effects:

The present invention can solve the current ultrasound-guided interventional therapy and the calibration problem of trackable and positioned ultrasound probes in the free-style three-dimensional ultrasound imaging system, so as to obtain more accurate calibration accuracy and more convenient calibration operation, and the accurately calibrated ultrasound can effectively provide three-dimensional ultrasound Improve the quality of reconstructed images and improve the safety and success rate of surgery.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments described in the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

Fig. 1 is a block diagram of an ultrasonic probe calibration system in a specific embodiment of the present invention.

Fig. 2 is a schematic flowchart of an ultrasonic probe calibration method in a specific embodiment of the present invention.

Fig. 3 is a schematic diagram of solving the calibration equation of the ultrasonic probe calibration method in a specific embodiment of the present invention.

Detailed ways

In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described The embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

Referring to Fig. 1, the present invention discloses an ultrasonic probe calibration system based on a positionable puncture needle, comprising an ultrasonic host 5, a spatial positioning device connected to the ultrasonic host 5, and a system host 2, the system host 2 serves as a data acquisition and The graphic workstation for calibration and solution, the spatial positioning device includes a spatial positioning system host 1, an ultrasonic probe 6, and an optical tracking object, and the optical tracking object includes an ultrasonic probe fixture 7 fixedly installed on the ultrasonic probe 6, and an ultrasonic probe fixture 7 fixedly installed on the ultrasonic probe fixture 7. The puncture needle and the first spatial positioning sensor 8, and the second spatial positioning sensor 10 fixedly installed on the puncture needle 9.

When performing an operation on the patient 3 on the operating bed 4 , scanning with a positionable ultrasonic probe is performed, and the spatial positioning sensor can be fixed on the traditional ultrasonic probe by using the ultrasonic probe fixture on the optical tracking object conveniently. Preferably, the first and second spatial positioning sensors in the present invention are optical sensors or electromagnetic sensors.

This system fixes the first spatial positioning sensor on the traditional two-dimensional ultrasonic probe, and is used to obtain the precise spatial position (including: position information, orientation information) of the ultrasonic probe relative to the coordinate origin of the optical marker itself. These spatial positioning information data streams will be collected by the control unit of the spatial positioning device, and input to the system host through the data line of the specific interface. At the same time, the ultrasonic image of each frame output by the ultrasonic host is input to the graphics workstation through a specific interface and an API interface matched with the host. The self-developed ultrasonic probe calibration software system is installed on the graphics workstation, which can simultaneously collect and record the real-time video stream from the ultrasonic host and the spatial position data stream from the spatial positioning system host for subsequent calibration solutions.

Correspondingly, as shown in FIG. 2, the method for calibrating an ultrasonic probe based on a positionable puncture needle specifically includes the following steps:

S1. Calibration model design and production;

S2. Extraction of calibration model feature points in the ultrasound image;

S3. Solving a calibration transformation matrix according to the calibration feature points extracted from the ultrasonic image.

The first step in the calibration process is the design and fabrication of the calibration model. In the calibration method of ultrasonic probe, the design and manufacture of the calibration model is very important. The quality of the model design directly affects whether the calibration operation is simple, whether the calibration feature point imaging is clear, whether the feature point extraction is convenient, and whether the subsequent calibration solution is accurate. According to the manufacturing manual of the tracking sensor device provided by the spatial positioning device and the original puncture positioning frame of the two-dimensional ultrasound system, an optical tracking object was made, including the ultrasonic probe fixture, the puncture needle, the first spatial positioning sensor, and the second spatial positioning The sensor can be conveniently and seamlessly combined with the existing ultrasonic probe puncture frame, which conforms to the doctor's operating habits.

Through the second spatial positioning sensor on the puncture needle, the actual spatial position u _i of each point on the puncture needle can be obtained in real time by the spatial positioning device; by tracking the actual position of the puncture needle on the ultrasound image, the puncture Image pixel coordinates X _i of point u _i on the needle. It can be seen from Figure 3 that u _i and _Xi are different representations of the same point in two different coordinate systems. Therefore, the relationship between the two is as follows (ie, the calibration model):

M _TN u _i = M _TR M _RP X _i ,

Wherein, T is the coordinate system of the space positioning device, N is the coordinate system of the second space positioning sensor on the puncture needle, R is the coordinate system of the first space positioning sensor on the ultrasound probe, and P is the coordinate system of the ultrasound image plane. M _RP represents the rigid body transformation matrix from the ultrasonic image scanning plane to the optical tracking object that needs to be calculated and solved; M _TR represents the transformation matrix of the ultrasonic probe relative to the optical tracking object, and M _TR represents the spatial position and orientation information of the ultrasonic probe (usually collectively referred to as attitude information), obtained from the real-time output of the spatial positioning device; M _TN represents the transformation matrix of the point on the puncture needle relative to the real-time ultrasound probe.

The second step of calibration is to extract the feature points of the phantom in the ultrasonic image. The puncture probe is displayed as a straight line feature on the ultrasonic imaging plane. The automatic extraction of the straight line is more convenient and faster than the automatic extraction of points. Preferably, the present invention The Hough transform is used to detect the straight line feature of the puncture needle in the ultrasound image.

The third step in the calibration process is to solve the calibration transformation matrix M _RP according to the calibration feature points extracted from the ultrasound image.

Since the calibration feature points are known relative to the actual spatial physical coordinates of the space positioning device, and are in one-to-one correspondence with their pixel points on the ultrasonic plane, the present invention uses the least squares method to solve the correspondence according to a series of feature points obtained. The calibration equation for :

$<span\; class="notranslate">\; [</span>\stackrel{<span\; class="notranslate">\; ~</span>}{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; RP</span>}}}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; arg</span>}\underset{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; RP</span>}}}{\mathrm{<span\; class="notranslate">\; min</span>}}\underset{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; TN</span>}}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; TR</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; RP</span>}}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; |</span>$

The ultrasonic probe calibration method based on the positionable puncture needle of the present invention can ensure that the ultrasound imaging plane just passes through the puncture needle, making the calibration process easy to operate.

In addition, the present invention ensures that the puncture needle is always known and visible in the ultrasound image plane. At the same time, since the puncture needle is linear, even if part of the puncture needle is not clearly displayed on the ultrasound image, the information of the missing part can be accurately estimated through direct linear fitting.

To sum up, the ultrasonic probe calibration system and method based on the positionable puncture needle of the present invention can solve the calibration problem of the trackable and positionable ultrasonic probe in the current ultrasound-guided interventional therapy and free-style three-dimensional ultrasound imaging system, so as to obtain more accurate calibration Accurate and more convenient calibration operation, accurate calibration of ultrasound can effectively provide the quality of three-dimensional ultrasound reconstruction images, and improve the safety and success rate of surgery.

It will be apparent to those skilled in the art that the invention is not limited to the details of the above-described exemplary embodiments, but that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Accordingly, the embodiments should be regarded in all points of view as exemplary and not restrictive, the scope of the invention being defined by the appended claims rather than the foregoing description, and it is therefore intended that the scope of the invention be defined by the appended claims rather than by the foregoing description. All changes within the meaning and range of equivalents of the elements are embraced in the present invention. Any reference sign in a claim should not be construed as limiting the claim concerned.

In addition, it should be understood that although this specification is described according to implementation modes, not each implementation mode only contains an independent technical solution, and this description in the specification is only for clarity, and those skilled in the art should take the specification as a whole , the technical solutions in the various embodiments can also be properly combined to form other implementations that can be understood by those skilled in the art.

Claims (7)

1. An ultrasonic probe calibration system based on a positionable puncture needle, characterized in that the system includes an ultrasonic host and a space positioning device connected to the ultrasonic host and a system host, and the system host is used for data acquisition and calibration solution , the space positioning device includes a space positioning system host, an ultrasonic probe, and an optical tracking object, and the optical tracking object includes an ultrasonic probe fixture fixedly installed on the ultrasonic probe, a puncture needle fixedly installed on the ultrasonic probe fixture, and a first The spatial positioning sensor and the second spatial positioning sensor are fixedly installed on the puncture needle. 2. The system according to claim 1, wherein the first spatial positioning sensor and the second spatial positioning sensor are optical sensors or electromagnetic sensors. 3. A method for calibrating an ultrasonic probe based on a positionable puncture needle as claimed in claim 1, wherein the method comprises: S1. Calibration model design and production; S2. Extraction of calibration model feature points in the ultrasound image; S3. Solving a calibration transformation matrix according to the calibration feature points extracted from the ultrasonic image. 4. The method according to claim 3, wherein the calibration model in the step S1 is: M _TN u _i = M _TR M _RP X _i , Among them, u _i is the actual spatial position of _the second spatial positioning sensor on the puncture needle; _Xi is the pixel coordinate of the second spatial positioning sensor on the puncture needle in the ultrasound image; The rigid body transformation matrix of the tracking object; M _TR represents the transformation matrix of the ultrasonic probe relative to the optical tracking object, and M _TR represents the spatial position and orientation information of the ultrasonic probe; M _TN represents the transformation matrix of the point on the puncture needle relative to the real-time ultrasonic probe. 5. The method according to claim 4, characterized in that, the step S3 is specifically: The calibration transformation matrix M _RP is solved according to the calibration feature points extracted from the ultrasonic image. 6. The method according to claim 5, characterized in that, the step S3 is specifically: The corresponding calibration equation is solved by the method of least squares: $<span\; class="notranslate">\; [</span>\stackrel{<span\; class="notranslate">\; ~</span>}{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; RP</span>}}}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; arg</span>}\underset{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; RP</span>}}}{\mathrm{<span\; class="notranslate">\; min</span>}}\underset{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; TN</span>}}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; TR</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; RP</span>}}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; |</span>$ 7. The method according to claim 3, wherein the step S2 is specifically: Hough transform is used to detect the linear features of the puncture needle in the ultrasonic image, and the calibration feature points on the linear features are extracted.