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X ray perspective view calibration method in operation navigation system

A technique of surgical navigation and calibration method, which is applied in the field of X-ray fluoroscopic image calibration in a spinal surgery navigation system, can solve the problems of limiting the functional application of a C-arm X-ray machine, affecting the flexibility of surgical navigation, and the stability to be improved, etc. To achieve the effect of convenient clinical application, difficult to estimate deformation, and reliable algorithm

Inactive Publication Date: 2011-04-27
FUDAN UNIV +1
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Problems solved by technology

However, this type of method has the following disadvantages: First, surgical navigation can only be carried out in the fluoroscopy position where the internal parameters of the imaging system are fixed, which limits the functional application of some C-arm X-ray machines and affects the flexibility of surgical navigation.
However, due to the interference of images such as the patient's body and surgical instruments in addition to the marker point information in the fluoroscopic image, the calibration process is complicated and the stability needs to be improved.

Method used

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  • X ray perspective view calibration method in operation navigation system
  • X ray perspective view calibration method in operation navigation system

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Embodiment 1

[0019] 1. X-ray fluoroscopic image acquisition and preprocessing

[0020] The X-ray fluoroscopic image is digitized by video acquisition technology, and the noise is comprehensively suppressed by the method of multi-frame averaging filtering and wavelet transform. First, the images are multi-stacked and averaged, and then the averaged image is used as the input image for wavelet transform filtering. The type of wavelet adopts the symmetric wavelet symN proposed by Daubechies, N=2, 3, . After the above series of processing, the image noise is effectively filtered out and the detail information in the original image is well preserved.

[0021] 2. Marker recognition and correction

[0022] The background information is filtered first. Using the principle of digital subtraction: set the original image as I Source , using a kernel function whose size is the diameter of the marker point to I Source Perform median filtering to obtain the background image I without marked points ...

Embodiment 2

[0085] Example 2 Collection and calibration test of clinical fluoroscopic images

[0086] The calibration target is fixed on the image intensifier of the C-type wall X-ray machine, and the proximal target surface is close to the input screen of the intensifier to collect the fluoroscopic image of the patient. Taking into account the sampling time and the movement of the patient's body, the present invention superimposes and averages the images collected within the first 0.5 seconds after the fluoroscopy pedal is released, and performs wavelet filtering;

[0087] The marking point is automatically identified, and the kernel function of the median filter is 2.5 mm; the present invention uses filtering and subtraction methods to remove the information of the non-marking point in the image. In the template matching algorithm, with 0.85 as the threshold, all points with R(i, j)>0.85 are listed as possible marked point centers, and cluster processing is performed to find the class c...

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Abstract

The invention belonging to process and application field of medical images relates to an X-ray perspective image demarcating method of an operation navigation system. The method comprises obtaining X-ray perspective images containing marking point information in the operation, performing filtration and subtraction to obtain the images only containing marking point information, obtaining the center coordinate and the arrangement direction of the marking points by utilizing methods of template matching, cluster analysis and statistics of information entropy, correcting the marking point coordinate by using a B belt transect and calculating the demarcating parameters. A projection coordinate of the marking point is obtained according to the obtained imaging model parameters, all pixels of the image is corrected according to the distance between the projection coordinate and the real coordinate on the image to obtained a corrected X-ray perspective image for the operation navigation system. The method has characteristics of simple embodiment, reliable algorithm, convenience in clinical application and improvement of precision of the operation navigation system.

Description

technical field [0001] The invention belongs to the field of medical image processing and application, and relates to a method for calibrating X-ray fluoroscopic images, in particular to a method for calibrating X-ray fluoroscopic images in a spinal surgery navigation system. Background technique [0002] Surgical navigation based on C-arm X-ray fluoroscopic images is a main type of spine surgery navigation, and is mostly used in thoracolumbar spine surgery. For such surgical navigation, it is necessary to calculate the internal parameters of the imaging system, such as focal length, image scale factor, radial distortion, etc., and external parameters, such as the focal space position, projection direction, etc., based on the X-ray fluoroscopic image. The above process is called the calibration of the imaging system. At the same time, due to the spherical effect of the image intensifier of the X-ray machine and the magnetic field offset caused by gravity, the obtained fluor...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): A61B6/02A61B19/00G06T7/00A61B34/20
Inventor 张翼宋志坚王满宁李文生姚德民
Owner FUDAN UNIV
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