TW201519856A - Surgical positioning method - Google Patents

Abstract

The present invention relates to a surgical positioning method. The surgical positioning method applies in a C-arm image-guided system. By converting the coordinate system between a positioning unit and a C-arm and obtaining the coordinate from a sensor, the X-ray image can only take once time. The surgical positioning method can combine the X-ray image and the coordinate from the sensor to obtain a real-time position of a surgical instrument in the X-ray image.

Description

Surgical positioning method

The invention relates to a surgical positioning method, in particular to a surgical positioning method applied to a C-arm shooting.

At present, in orthopedic or spinal surgery, medical personnel often need to implant some implants into the human body. In order to accurately implant the implants into the correct position, computer-assisted positioning technology has been developed in recent years. Improve the accuracy of positioning during surgery. Medical personnel can use the imaging equipment to obtain a two-dimensional image of the patient's lesion location in advance, and then use the computer to reconstruct the stereoscopic image of the lesion and coordinate it. In this way, the coordinate position of the surgical tool can be input during the operation to guide the computer, which greatly improves the accuracy of the positioning during the operation.

The C-arm is a tool commonly used in orthopedic or spinal surgery to confirm the orientation of the surgical tool and to establish a medical image as a basis for guiding and positioning the medical staff during surgery. At present, the positioning process of the C-arm is to install a dynamic reference frame (DRF) on the patient and the C-arm, and then take the first X-ray image at the first shooting position with the C-arm, and The relative position of the C-arm to the patient at this time was recorded with an optical camera. Then move the C-arm to the second shooting position to shoot The second X-ray image is recorded with an optical camera to record the relative position of the C-arm at the second shooting position to the patient. Using the secondary X-ray image, the relative position of the C-arm and the patient, the conversion formula of the three-dimensional coordinates of the lesion of the patient and the two-dimensional plane coordinates of the corresponding point on the X-ray image is calculated to obtain the lesion. The position in the three-dimensional space serves as the basis for the guidance and positioning of medical personnel during surgery.

However, the above method must use the C-arm to capture more than two X-ray images. The C-arm has the advantages of low imaging cost, fast imaging speed, and high maneuverability. However, in order to continuously confirm the position of the surgical tool, it must be continuously photographed. The new images have caused patients and medical personnel to withstand high doses of radiation during the operation, which is a serious threat to human health. In addition, in order to simultaneously track the C-arm and the dynamic reference frame of the patient, the optical camera needs to use an optical camera with a wide tracking range and a large volume, which not only increases the manufacturing cost, but also is not conducive to carrying, and cannot reduce the operating room. Space.

In view of this, how to effectively reduce the number of X-ray images taken by the C-arm, and only need to track the dynamic reference frame of the patient, without tracking the dynamic reference frame on the C-arm to balance the operation time. Accuracy, lower manufacturing costs and increased system portability are one of the urgent issues to be solved.

In view of the above problems, an object of the present invention is to provide a surgical positioning method for use in a C-arm image guidance system, through the coordinate system between the positioning unit and the C-arm, and with the space coordinates obtained by the sensor So that the C-arm only needs to take an X-ray image once, then the X-ray can be taken In combination with the spatial coordinates obtained by the sensor, real-time position information of the surgical instrument relative to the positioning unit on the X-ray image can be obtained.

In order to achieve the above object or other objects, the present invention provides a surgical positioning method for a C-arm image guiding system, which is used in a surgical site with a surgical instrument having a plurality of marking point elements, the surgical positioning method comprising the following Step: (1) providing a C-arm and a positioning unit, the positioning unit having a plurality of marking point elements and the positioning unit is fixed to the surgical site; (2) markings located at a center point of the marking point elements Point elements are defined as origins, and space coordinates of the point elements relative to the origin are calculated to obtain a first coordinate system; (3) using the C-arm to perform an X for the positioning unit and the surgical site Optical image capturing to obtain a second coordinate system, and simultaneously obtaining a first space coordinate of the positioning unit by a sensor; (4) obtaining a conversion relationship between the first coordinate system and the second coordinate system (5) using the sensor to obtain a second space coordinate of the surgical instrument; and (6) calculating a phase of the first space coordinate and the second space coordinate on the X-ray image according to the conversion relationship Position, the surgical instrument to obtain an X-ray image to the real-time location relative to the positioning unit.

According to the surgical positioning method of the present invention, the conversion relationship between the positioning unit and the coordinate system between the C-arms can be obtained. Therefore, the sensor does not need to track the dynamic reference frame on the C-arm, and only needs to track the surgical instrument. Positioning unit, and using the conversion relationship to convert the coordinate system of the surgical instrument to the same coordinate system as the X-ray image, and combining the positioning unit to obtain the surgical instrument on the X-ray image relative to the positioning unit Instant bit Set information, and achieve the accuracy of positioning during surgery, reduce manufacturing costs and increase system portability.

10‧‧‧C-arm

11‧‧‧ projection point

12‧‧‧ Patients

121, 122‧‧‧ feature points

13‧‧‧Projection surface

131, 132‧‧‧ projection point

21‧‧‧First coordinate system

22‧‧‧Second coordinate system

F‧‧•focal length

S01~S06‧‧‧Steps

T _z ‧‧‧ translation

1 is a schematic view of an embodiment of a surgical positioning method of the present invention; and FIG. 2 is a flow chart of a surgical positioning method of the present invention.

The embodiments of the present invention are described in the following specific embodiments, and those skilled in the art can easily understand other advantages and functions of the present invention by the disclosure of the present disclosure, and may also use other different embodiments. Implement or apply. Thus, the present invention encompasses any component or method of any particular embodiment disclosed herein, and can be combined with any component or method of any other embodiment disclosed herein.

Please refer to FIGS. 1 and 2 at the same time. The surgical positioning method of the present invention is used in conjunction with a surgical instrument in a surgical site, for example, in a lumbar spine minimally invasive internal fixation operation, and the surgical instrument may specifically be an electric knife or a tapping tooth. Cone, the surgical site is the spine, lumbar vertebrae, joints, hip joints or other bone parts of the patient, etc. Therefore, the surgical positioning method of the present invention is one of the related technologies of computer-assisted surgery, and is assisted by image navigation technology. To reduce the misalignment rate of the screw during implantation of a pedicle screw. The surgical instrument has a plurality of landmarks, and the marker elements on the surgical instrument are at least four or more, and the marker elements are disposed on the same plane. The marker element is specifically a passive reflective sphere with a reflective function or an active light source.

In step S01, the surgical positioning method of the present invention must be applied to a C-arm (C-arm) 10 and a C-arm image guiding system of the positioning unit. The C-arm 10 is an imaging device that can take X-ray images during surgery. If used with a navigation system, the X-ray image can be used for navigation. The positioning unit is a dynamic reference frame (DRF) of the device at the surgical site of the patient 12, and the positioning unit has a plurality of marking point elements, and the marking point component is specifically coated with a special coating and has a reflecting function. Reflective ball, which reflects the light emitted by the sensor, or a light-emitting element with an active light source, such as an infrared light-emitting diode that emits a specific segment wavelength (880 nm to 930 m). Further, the number of marker elements is at least four or more, and the marker elements disposed on the positioning unit must be on different planes. In Fig. 1, the feature points 121, 122 on the patient 12 are the point elements on the corresponding positioning unit. In this embodiment, two feature points 121, 122 (i.e., two point elements) are used. For the sake of explanation, the best is four or more, but the invention is not limited thereto.

In step S02, one point of the marker point component on the positioning unit must be defined as the origin, specifically, the marker point component located at the center point of the plurality of marker point components is determined as the origin, and other marker point components can be Calculating the spatial coordinates of the origin to determine the spatial coordinates of each marker element. In one embodiment, feature point 121 on patient 12 is used as the origin. The space coordinates of the overall marker point elements may constitute the first coordinate system 21. Specifically, the first coordinate system 12 is a coordinate system of the patient (ie, the coordinate system of the positioning unit), and the relative spatial coordinates of the feature point 122 are calculated by using the feature point 121 as the origin.

In step S03, after the C-arm 10 is moved and positioned, the C-arm 10 can be used to perform an X-ray image capturing operation. When taking an X-ray image, it must be confirmed that all the marker elements on the positioning unit are within the imaging range of the X-ray image, that is, the C-arm 10 is for taking the X-ray image for the positioning unit and the surgical site, and The coordinate system used in the X-ray image is the second coordinate system 22. Specifically, the C-arm 10 must include the feature points 121 and 122 in the imaging range of the X-ray image. The second coordinate system 22 is a coordinate system of the C-arm. The captured X-ray image is illustrated by a simulated projection surface 13. Since the C-arm 10 incorporates the feature points 121 and 122 into the imaging range of the X-ray image, it can be seen on the projection surface 13 respectively. Projection points 131, 132 of feature points 121, 122. While the C-arm 10 captures the X-ray image, the spatial position of the positioning unit is tracked by a sensor to obtain a first space coordinate, and the sensor is specifically an infrared sensor. In one embodiment, the C-arm 10 can be moved such that the center of the C-arm 10 faces the origin as much as possible to reduce the complexity of subsequent calculations, that is, the projection point of the center of the C-arm 10. 11 is as close as possible to the feature point 121 as the origin, but the invention is not limited thereto.

In step S04, the first coordinate system and the second coordinate system obtained by the foregoing are calculated to obtain a conversion relationship between the two, and the conversion relationship is specifically a homogeneous transformation matrix, which is a 4×4 matrix. Can be expressed as Where R is an orthogonal matrix and T is a translation matrix. The orthogonal matrix is obtained according to a relative angular relationship between the first coordinate system and the second coordinate system, and the translation matrix is obtained by the distance between the center of the C-arm and the origin.

In detail, the projection point 11 is the center point of the C-arm 10, and the coordinate system unit of the projection point 11 of the C-arm 10 can be defined first. , That is, the second coordinate system 22. The coordinate system unit vector of the feature points 121, 122 can be defined as Since the feature point 121 is defined as the origin (M ₀ ), the coordinate (M _i ) of the feature point 122 can be derived by using the feature point 121 as the origin, that is, the feature points 121 and 122 are in the space. It is understood that the unknown is the coordinates of the projection points 131, 132 of the feature points 121, 122 in the second coordinate system 22. Suppose the image coordinates of the projected projection point 132 are ( x _i , y _i ), the coordinates of the feature point 122 are ( X _i , Y _i , Z _i ), and the vectors of the feature points 121 and 122 are .

Therefore, the orthogonal matrix R in the homogeneous transformation matrix can be expressed as The orthogonal matrix R represents a relative angular relationship between the first coordinate system and the second coordinate system, wherein R ₁ , R ₂ , and R _{3 are} defined as column vectors of the orthogonal matrix R, and each column in the orthogonal matrix R is respectively Unit vector for the second coordinate system , the relative position in the first coordinate system is defined separately And .

In addition, the translation matrix T in the homogeneous transformation matrix can be expressed as The translation matrix T represents the distance from the center of the C-arm to the origin. Since the projection point 11 at the center of the C-arm 10 is aligned with the feature point 121 as the origin as much as possible, the vector of the projection point 11 and the feature point 121 is parallel to the vector of the projection point 11 and the projection point 131, so the first coordinate system is calculated. just translational shift amount T _z coordinates of the projection point T _z is the shift amount of the center 10 of the C-arm 11 to the Z-axis distance between the feature point 121, which further define the C-arm 10 The distance from the projection point 11 to the projection surface 13 at the center is the focal length f. In proportional vertical projection, the scale factor of the vector projected on the projection surface 13 is The image coordinates of the projection point 132 are ( x _i , y _i ) and can be expressed as . In the scaled vertical projection, the depth between the feature points 121, 122 will be much smaller than the distance between the feature point 121 as the origin to the projection point 11 of the center of the C-arm 10, and therefore, the projection point 132 can be The image coordinates are ( x _i , y _i ) further expressed as Where ε is the calculation error.

Scale factor and Can be defined as two vectors on the projection surface 13 And known The image coordinates of the projection point 132 containing the error are ( x _i ', y _i ), x _i ', y _i ' can be respectively Calculated from the vector of feature points 121, 122, the formula can be expressed as:

will Substituting the second formula . In order to make the correction calculation error more accurate, first assume the error ε =0, and then calculate according to the above formula , then Calculate R ₃ , and with R _{3 ,} calculate ε _i and check whether ε _i approaches ε _{i -1} . If it approaches, the operation ends, and the ε _{i is} used as the error calculation value to correct; if not approaching Then ε _{i is taken} as ε and substituted into the above formula to recalculate until ε _i approaches ε _{i -1} . In this way, the error value can be corrected by this operation flow, thereby obtaining a more accurate image.

After obtaining the conversion relationship, the coordinate system of the surgical instrument can be converted into the coordinate system of the C-arm when the surgical instrument is used in the surgical site. In step S05, the sensor must first use the sensor to obtain the second spatial coordinate of the surgical instrument. After obtaining the second space coordinate in step S06, the second space coordinate is converted into a coordinate system of the C-arm by using the conversion relationship, and the first space coordinate of the positioning unit is also used together by the conversion relationship. Conversion. After the first space coordinate and the second space coordinate are converted into the coordinate system of the C-arm, the relative position of the positioning unit and the surgical instrument can be displayed on the X-ray image. In this way, as long as the space coordinates of the surgical instrument are continuously tracked by the sensor, the instantaneous position information of the surgical instrument relative to the positioning unit can be obtained on the X-ray image immediately after the conversion relationship is converted. Therefore, the sensor does not need to track the dynamic reference frame on the C-arm, and only needs to track the positioning unit on the surgical instrument, so that the sensor with a smaller tracking range can be used, further reducing the manufacturing cost and increasing the system's Portability. The surgical positioning method of the present invention only needs to take an X-ray image once to achieve the purpose of surgical positioning, and the patient and the medical personnel do not have to bear excessive high doses of radiation.

The above embodiments are merely illustrative of the technical principles, features, and effects of the present invention, and are not intended to limit the scope of implementation of the present invention. Modifications and variations of the embodiments described above may be made without departing from the spirit and scope of the invention. Equivalent modifications and variations made using the teachings of the present invention are still covered by the scope of the following claims. The scope of the invention should be as set forth in the following claims.

S01~S06‧‧‧Steps

Claims (9)

A surgical positioning method is applied to a C-arm image guiding system, which is used in a surgical site with a surgical instrument having a plurality of marking point components. The surgical positioning method comprises the following steps: (1) providing a C-arm and a positioning unit having a plurality of marking point elements and the positioning unit is fixed to the surgical site; (2) defining a marking point element located at a center point of the marking point elements as an origin, and calculating the points Marking a point element relative to a spatial coordinate of the origin to obtain a first coordinate system; (3) using the C-arm to perform an X-ray image capture on the positioning unit and the surgical site to obtain a second coordinate system And obtaining a first space coordinate of the positioning unit by a sensor; (4) obtaining a conversion relationship between the first coordinate system and the second coordinate system; (5) obtaining the function by using the sensor a second space coordinate of the surgical instrument; and (6) calculating a relative position of the first space coordinate and the second space coordinate on the X-ray image according to the conversion relationship to obtain the surgical instrument on the X-ray image For real-time location of the positioning unit. The surgical positioning method of claim 1, wherein the positioning unit is a dynamic reference frame, and the plurality of marking point elements of the positioning unit are at least four and are respectively disposed in different planes. on. The surgical positioning method according to claim 1, wherein the plurality of marking point elements of the surgical instrument are at least four or more and disposed on the same plane. The surgical positioning method of claim 1, wherein the marking point elements are reflective balls or infrared light emitting diodes. The surgical positioning method of claim 1, wherein the sensor is an infrared sensor. The surgical positioning method according to claim 1, wherein the conversion relationship is a homogeneous transformation matrix. The surgical positioning method of claim 6, wherein the homogeneous transformation matrix further comprises an orthogonal matrix, wherein the orthogonal matrix is based on a relative angle between the first coordinate system and the second coordinate system Relationship earners. The surgical positioning method of claim 6, wherein the homogeneous transformation matrix further comprises a translation matrix obtained by a distance from a center of the C-arm to the origin. The surgical positioning method according to claim 1, wherein the surgical instrument is an electric burner or a tapping cone.