JP2006167448A - Imaging method and apparatus for supporting operator during interventional radiology procedure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging method, displaying the position of at least one point of a surgical instrument disposed in a vascular system of a patient in real time. <P>SOLUTION: This imaging method is implemented according to a computer program in an imaging apparatus 1. This method includes: a step of digitizing a two-dimensional image obtained by an image obtaining system 2 by an image digitizing device 13; a step of determining the current three-dimensional position of a predetermined point of the surgical instrument from the digitized image and a three-dimensional model of the vascular system of the patient stored in a memory 4 by a processor 3; a step of determining the current three-dimensional position as a function of the position before the surgical instrument in the three-dimensional model and the position of a blood vessel of the vascular system represented by the three-dimensional model; and a step of displaying an image representing the point of the surgical instrument by the current three-dimensional position using a display system 5. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is directed, in one embodiment, to an imaging method and apparatus for interventional radiology. Specifically, the present invention is directed, in one embodiment, to a medical imaging method and apparatus for displaying in real time the position of a surgical instrument located within an object, such as a patient's vasculature. .

  In general, the principles of an interventional radiology procedure include guiding and applying a therapeutic instrument within an object, ie, a patient's artery, for an operator with the aid of a medical imaging device. This medical imaging device can acquire, process and display a two-dimensional image representing the vascular system and treatment instrument in real time. These two-dimensional images allow the operator to more easily guide the therapeutic instrument into the artery by estimating the position of the therapeutic instrument within the vascular system.

  However, the displayed two-dimensional (2D) image is two-dimensional while the vascular system is three-dimensional. As a result, the operator lacks the coordinates required to determine the position of the surgical instrument within the vascular system with the highest possible accuracy.

  The prior art has proposed a medical imaging apparatus and method capable of displaying a three-dimensional (3D) image representing a treatment instrument at the current position together with the vascular system.

  U.S. Pat. No. 6,317,621 describes an apparatus and method. The medical imaging apparatus has an image acquisition system, a processing system, and a display system. The image acquisition system has a biplanar system that can simultaneously acquire two 2D images acquired at different angles. The processing system can determine the current position of the treatment instrument in three dimensions. In order to determine this current position, the processing system calculates 3D coordinates (X, Y, Z) of the points of the treatment instrument. The display system can display a 3D image representing the current position of the treatment instrument and the patient's vascular system. In order to calculate the coordinates of the points of the treatment instrument, the processing system uses two 2D images acquired simultaneously at different angles. However, simultaneous acquisition of two 2D images requires high dose X-rays to be emitted towards the patient. Such high X-ray exposure is detrimental to the patient. In addition, uncertainty remains about the calculated 3D coordinates.

U.S. Pat. No. 6,389,104 describes medical imaging and related methods and apparatus capable of displaying a 3D image representing the current position of the treatment instrument and the patient's vasculature. The image acquisition system is a single plane system capable of acquiring 2D images. The current position is determined by calculating the 3D coordinates of the therapeutic instrument point from the 2D image representing the therapeutic instrument and the vascular system. Nonetheless, there is no exact mathematical method for calculating a single 3D coordinate starting from a single 2D image. Thus, the displayed 3D image does not represent the treatment instrument at its actual current position. The displayed 3D image represents the treatment instrument at its most probable current location. The operator does not have any visual information that accurately determines the accuracy probability of the current position displayed.
US Pat. No. 6,317,621 US Pat. No. 6,389,104

  The present invention, in one embodiment, is directed to an imaging method and apparatus that overcomes at least one of the above-mentioned drawbacks.

  One embodiment of the present invention provides a three-dimensional model representation that represents the vasculature of an object such as a patient and the location of at least one point of a surgical instrument displaced in the vasculature. Intended for imaging methods that can be performed in time. In that case, the position of at least one point of the surgical instrument at the point of the surgical instrument in the vascular system is estimated. In one embodiment of the method, a region in the vicinity of the projection on the image of the point whose position is to be estimated is determined in the two-dimensional image of the patient. As a function of the three-dimensional position previously determined for the blood vessel position and / or surgical instrument point represented in the three-dimensional model, the points in the three-dimensional model projected into the neighborhood on the two-dimensional model Selected.

  One embodiment of the present invention is a three-dimensional model representing a vascular system, and an imaging device capable of displaying in real time the position of at least one point of a surgical instrument displaced in the vascular system. Is targeted. In one embodiment of the invention, the imaging device comprises means for estimating a current three-dimensional position of a surgical instrument point in the vascular system, the means for estimating being a two-dimensional image of a patient, Means for determining a region within the vicinity of the projection of the point to be estimated on the image, as a function of the position of the blood vessel represented in the three-dimensional model and / or for the point of the surgical instrument Means for selecting a point in the three-dimensional model to be projected into the neighborhood on the two-dimensional model as a function of the three-dimensional position.

  One embodiment of the present invention is directed to a suitable computer program comprising encoding means for performing the method described above. An instruction support is also provided for storing the computer program described above.

  Other features and advantages of the apparatus and method according to the invention will become more apparent upon reading the following description, which is given purely by way of non-limiting example as to be read with reference to the accompanying drawings. .

  During an interventional radiology procedure, the operator places the active end of the surgical instrument through the blood vessels (veins and arteries) of the patient's vasculature and into the area to be treated within the patient's body. The surgical instrument may be a catheter, a guide wire, or other instrument known to those skilled in the art. The catheter is a very thin tube (2-6 mm in diameter) with a length of approximately 1 m, guided by a movable, flexible, radiation-free guide wire.

  In order to facilitate placement of the active end of the surgical instrument, the imaging device can display an output image representing the current three-dimensional (3D) position of the surgical instrument in real time. To determine the current 3D position of the surgical instrument, the 3D coordinates (X, Y, Z) of the surgical instrument are calculated using a 3D model and a two-dimensional (2D) image of the patient's vasculature. . A 3D model of a patient's vasculature is a three-dimensional image that represents the blood vessels of the patient's body.

  In one embodiment of the invention, one can choose to display either the current 3D position of the entire surgical instrument or the current 3D position of a certain point of the surgical instrument. For example, an output image representing the current 3D position of the active end of the surgical instrument can be selected to be displayed. Also, an output image representing the current 3D position of the surgical instrument tip can be selected to be displayed. Still further, an output image representing the 3D position that the apex point occupied one after another from the beginning of the interventional radiology procedure can be chosen to be displayed.

  In the following description and examples, only the search for the current 3D position of the tip of the surgical instrument used by the operator during an interventional radiology procedure will be considered. The distal point of the surgical instrument corresponds to the apex of the active end of the instrument inserted into the patient's vasculature.

  An example of the imaging apparatus will be described below. Referring to FIG. 1, a block diagram obtains a two-dimensional (2D) image of an object 6 to display an output image representing the current 3D position of the surgical instrument tip, The imaging apparatus 1 which can process the acquired 2D image is illustrated. The apparatus 1 includes an image acquisition system 2, an image processing system 3, and an image display system 5.

  The image acquisition system 2 can acquire a 2D image representing the surgical instrument and the vascular system in two dimensions. The image acquisition system has a single plane scanner. The image acquisition system 2 includes, for example, an ultrasound image acquisition system, a magnetic resonance imaging (MRI) image acquisition system, an image acquisition system based on unique photon emission tomography (UPET), a computer-aided tomography image acquisition system (CAT), and a positron An emission tomography image acquisition system (PET) or an X-ray image acquisition system.

  The image processing system 3 includes processing means to which various processing methods can be applied. The image processing system 3 can be integrated with the image acquisition system 2 or can be separate from the image acquisition system 2. The processing system 3 is, for example, one or several computers, one or several processing devices, one or several microcontrollers, one or several microcomputers, one or several programmable Automaton, one or several application specific integrated circuits, other programmable circuits, or other equipment including a computer such as a workstation. The processing system is coupled to means 4 for providing memory. This memory means 4 can be integrated with the processing system 3 or can be separate from the processing system 3. Such a memory means 4 can in particular store a 3D model of the vascular system being examined.

  The display system 5 can display an output image representing the current 3D position of the surgical instrument tip. For example, this current 3D position can be superimposed on a 3D model of the vascular system in the output image. The image display system 5 can be integrated with the image acquisition system 2 or the processing system 3 or can be separate from the image acquisition and processing systems 2 and 3.

  The operation principle of the apparatus illustrated in FIG. 1 is as follows. The image acquisition system 2 transmits an acquisition signal toward the object 6 to generate original projection data. This original projection data is converted into a 2D image representing the surgical instrument and the vascular system in two dimensions. This 2D image is sent to the processing system 3. The processing system 3 processes the 2D image by processing means suitable for applying the processing method. Specifically, the processing means can execute the imaging method described below. With this imaging method, an output image representing the current 3D position of the tip point can be obtained starting from the 3D model and 2D image. This output image is displayed on the display system. With N being a given time interval (eg, N = 10 milliseconds), every N seconds, the image acquisition system acquires projection data to obtain a 2D image. Each 2D image corresponds to a new current position of the surgical instrument tip. The current position of the tip point is determined in real time from the 2D image and the 3D model. In this way, an output image representing the current 3D position of the surgical instrument tip is repeatedly generated every N seconds.

  Referring to FIG. 2, one embodiment of the imaging device of FIG. 1 is illustrated. The imaging device includes an image acquisition system 2, a processing system 3, a memory means 4, a display system 5, an image digitizing device 13, and an image reconstruction device 14.

  The image acquisition system 2 is an image acquisition system. The image acquisition system 2 comprises an emission means 7 in the form of an X-ray source, a radiation image acquisition means 8 and a support means 9. The radiographic image acquisition means 8 is a brightness | luminance amplifier provided with the plane sensor or the camera, for example. The discharge means 7 and the radiation image acquisition means 8 are fixed to both ends of the support means 9 in the form of a semicircular arm, for example. The support means 9 can position the ejection means 7 and the radiation image acquisition means 8 with respect to the patient 6.

  The processing system 3 includes a processing means 10, a motor control device 11 for supporting means, and an X-ray control device 12. The motor control device 11 for the support means controls the speed and position of the support means 9. The X-ray controller 12 supplies power and synchronization signals to the X-ray source 7. In one embodiment of the present invention, the processing system 3 comprises a reading device (not shown) for reading imaging method instructions from an instruction carrier (not shown) such as a floppy disk or a CD-ROM, for example , Floppy disk or CD-ROM drive. In another embodiment of the invention, the processing means 10 executes imaging method instructions (described below) stored in software (not shown).

  The memory means 4 is, for example, a read only memory (ROM) and a random access memory (RAM). The display system 5 may be any type of display device known to those skilled in the art, such as, for example, a computer screen, monitor, flat screen, plasma screen or the like. The image digitizing device 13 is a data acquisition system (DAS). DAS samples an analog signal and converts the signal to a digital signal. The image reconstruction device 14 can reconstruct a 2D image from a plurality of digital data. The DAS 13 and the image reconstruction device 14 can be integrated with the processing system 3 or can be separate from the processing system 3.

  When acquiring the 2D radiation image, the emission unit 7 projects the X-ray beam 20 toward the image acquisition unit 8. The image acquisition means 8 detects all projection X-rays that have passed through the patient, generates an electrical signal, and sends the electrical signal to the DAS 13. The DAS 13 samples analog electrical signals received from the image acquisition means and converts them into digital signals. An image reconstructor 14 receives sampled and digitized data from DAS 13 and performs 2D image reconstruction at high speed. The reconstructed 2D image is supplied as an input to the processing unit 10, and the processing unit 10 stores the 2D image in the memory unit 4. The processing means 10 is programmed to perform the imaging method described below and to process 2D images from the image reconstruction device. The output image obtained from the processing means is displayed on the display system.

  Hereinafter, an imaging method for obtaining an output image representing the current 3D position of the distal point of the surgical instrument will be described. This imaging method requires a 3D model of the vascular system as input. All methods known to those skilled in the art can be used to obtain the 3D model, for example, the method described in US Pat. No. 6,389,104 can be used. A 3D model of a patient can also acquire two 2D images simultaneously by tomography that can acquire a portion (eg, trunk) of a patient in slices (cross sections) or from two different angles. It can be obtained with a two-plane scanner.

  One stage of the method involves acquiring and digitizing a 2D image. Another stage of the method includes determining the 2D position of the tip point in the 2D image acquired by the acquisition system. All methods known to those skilled in the art can be used to locate the tip of a surgical instrument in a 2D image. For example, a region growth method can be used. These methods include morphological mathematical pre-processing (expansion, erosion, and combinations thereof such as opening and closing), threshold processing to obtain binary images, post-processing for image smoothing, etc. Can do.

  Another stage of the method determines the exact position of the emission means 7 and the radiation image acquisition means 8 relative to the 3D acquisition object, i.e. the acquisition geometry corresponding to the position of the acquisition system relative to the patient 6 during the 2D image acquisition. Including that. Methods known to those skilled in the art can be used to determine the acquisition geometry. By determining the acquisition geometry, two of the three coordinates (X and Y coordinates) that define the current 3D position of the tip can be determined. An example of how the acquisition geometry can be determined is to calculate a plurality of images representing the projection of the 3D model on the projection plane for different positions and orientations of the 3D model relative to the projection plane, and to acquire these projection images and acquisitions. Comparing the obtained 2D image and finding a projection image that can be superimposed on the acquired 2D image. The position and orientation of the patient during acquisition of the 2D image correspond to the position and orientation of the 3D model during calculation of the projection image that can be superimposed on the acquired 2D image.

  Here, it is understood that there is uncertainty about the acquired geometry due to mechanical inaccuracy, patient movement that may occur during 2D image acquisition, or blood vessel deformation that may be caused by the surgical instrument. Is done. This error in acquisition geometry is taken into account during one of the stages that allows the determination of the 3D position of the surgical instrument tip.

  After the processing means calculates the 3D model, locates the surgical instrument in the 2D image, and determines the acquisition geometry, the processing means is a subsequent step in the imaging method to determine the current 3D position of the tip point. Execute.

  As shown in FIG. 3, after the acquisition geometry is determined, the tip of the instrument is located somewhere on the axis 21 connecting the emission means 7 and the radiation image acquisition means 8. I understand. Since the information contained in the acquired 2D image is insufficient to determine the 3D coordinates of the tip point, there are certain conditions that the tip point must satisfy in order to determine the current 3D position of the tip point. Applied. Those conditions are as follows. (1) The position of the distal point is a function of the position of the blood vessel in the three-dimensional model, and the distal point of the surgical instrument is not randomly positioned on the axis, but is positioned in the blood vessels 22 and 23. And / or (2) that the current position of the distal point is a function of the previous position of the distal point and that the movement of the distal point of the surgical instrument is continuous; If the acquisition of the 2D image at t is close in time to the acquisition of the 2D image at time t-1, the 3D position of the tip point at time t is spatially the 3D position of the tip point at time t-1. It is close.

  Each new acquired 2D image corresponds to a projection of the vascular system onto the radiological image acquisition means 8. For each new acquired 2D image, the axis 21 connecting the emission means 7 and the projection of the tip point onto the radiation image acquisition means 8 is taken into account. With this axis, the slope Z (Z axis) of the orthonormal benchmark having the abscissa X and the ordinate Y can be defined. Consider a set of voxels 67 around this axis 21. This set of voxels 67 corresponds to a point of the vascular system that projects within the vicinity of the 2D position of the tip point on the 2D image.

  For each integer value of the Z coordinate (the Z axis is parallel to the optical axis 21), consider R voxels in the vicinity of a set of voxels 67. Here, R is an integer. By taking into account the R voxels in the vicinity around the axis 21, errors in the acquired geometry are taken into account.

  Each voxel on axis 21 corresponds to a grayscale value having a value between 0 and 255. For each voxel on the axis 21, an integer value is stored in a point sequence (also referred to as a “line”) 24 consisting of a series of points (one voxel on the axis 21 corresponds to one point in the point sequence). This value is equal to the maximum grayscale value of the voxel in the neighborhood 25 if the neighborhood (subset) 25 of the voxel intersects the blood vessel, and zero if the neighborhood of the voxel (subset) 26 does not intersect the vessel. be equivalent to. By setting the value of the point sequence 24 corresponding to the vicinity of the voxel that does not intersect any blood vessel to zero, the tip point must remain in the blood vessel.

  The missing information is the position of the tip point on this line 24 and the segment containing the tip's current 3D position can be determined, but the exact current 3D position cannot be determined. Each new acquired 2D image corresponds to a new position of the tip point. One line 24 is generated for each new acquired 2D image to form a small image 40 called a “curved slice” as shown in FIG.

  At time t = 0, a first 2D image is acquired and a first line 27 is generated. This line includes first, second and third segments 28, 29 and 30 corresponding to the first, second and third blood vessels 31, 32 and 33 where the tip points may be placed. . At time t = 1, a second 2D image is acquired and a second line 34 is generated and then continued in the same manner.

  As acquisitions continue in this manner, certain segments that may contain the surgical instrument tip are rejected. For example, at time t = 8, the first and second segments 28 and 29 corresponding to the first and second blood vessels 31 and 32 no longer exist in the generated line. However, the previous position is taken into account to determine the current 3D position of the tip point. Therefore, at t = 8, it is certain that the distal point of the surgical instrument is located in the blood vessel 33.

  Several blood vessels may join to produce an ambiguous portion 35, which means an intersection at a level where the surgical instrument may follow several paths 36,37. In this case, there will again be uncertainty about the segment containing the tip. In one embodiment of the imaging method, these ambiguous parts can be managed and displayed. These ambiguous parts are unavoidable because multiple blood vessels may be projected onto the same point in the 2D image.

  Next, one embodiment of an imaging method for determining the current 3D position of the surgical instrument tip will be described. When initializing the method, or after the operator has moved the surgical instrument suddenly, it will search for all possible 3D positions along the entire line. Each segment in the line that contains a value above a fixed intensity threshold may contain a surgical instrument tip. If the previous position of the surgical instrument tip is known sufficiently close, the search for possible current 3D positions is limited and the following steps are performed. That is, finding a starting point taking into account a segment about the previous position of the instrument tip, searching for a boundary starting from this point, searching for a new branch starting at this segment, Repeating the above steps for each segment of the line, suppressing all new line segments with grayscale points below a fixed threshold, fusing the segments of the new line, and the instrument tip point Estimating the reliability of segments that could potentially be found.

  FIG. 5 is a flow diagram of one embodiment of an imaging method. Each new acquired 2D image corresponds to a new position for the tip point. The first stage of the method involves taking a 2D image and digitizing it. The acquired geometry is then determined and subsequent steps are performed.

  In step 410, an axis line 21 connecting the emission means 7 and the 2D projection on the radiation image acquisition means 8 at the tip point is drawn, and the corresponding line 24 is calculated. If the acquired 2D image is the first acquired image (initialization), or if the position before the tip is too far from the current position, step 420 is performed. In this stage 420, the line 24 is processed by a function unit called a first line function unit. The first line function unit calculates the position with the highest probability for the tip point. In other words, the first line function unit determines the line segment most likely to include the tip point from among the plurality of line segments.

  The subsequent steps are then performed for each line segment. In step 430, a new starting point is determined for the segment being handled. This starting point is chosen according to the specific criteria described below.

  In step 440, the segment boundaries are searched. These boundaries are the points at the ends of the segment. In order to calculate the new boundary of the segment, the starting point of the segment is used with the specific criteria described below.

  In step 450, a new segment to be added to the line is searched. Add a new segment to the line according to the criteria described below.

In step 460, the segments are sorted to generate a tree structure. Segments are sorted along the Z axis and joined to the previous line segment. In step 470, segment control is performed. According to the criteria described below, specific segments are merged and other segments are suppressed.

  In step 480, line segment reliability is estimated and the appropriateness of the displayed result is expressed using a color code. For example, a line segment having a high probability of including a tip point is displayed in green, while a segment having a low probability of including a tip point is displayed in yellow. Prior to display, these results are processed by a smoothing function to improve the display quality.

  In step 490, such a result is displayed on the display means.

  It will be appreciated that certain steps of the method can be performed sequentially or in parallel. Moreover, certain steps can be performed in a different order.

  Next, the search for the start point of one segment will be described. The start point 50 of the segment is the point of maximum gray scale value within the segment. To determine this starting point 50, consider the limits defined by the boundaries of this segment in the previous line.

  Next, a search for a new boundary of one segment will be described. With reference to FIGS. 6-8, the steps for searching for a new boundary are illustrated. These figures are graphs representing the intensity of points as a function of the position of the points along the line (Z coordinate). Consider a line of a “curved slice” image with a given starting point 50. Search for two boundaries. The search for each boundary is performed as follows. Moving from the start point 50 of the grayscale value V point by point, continue until the next condition is satisfied. That is, (a) until a point 52 with a gray scale value lower than the first fixed value 53 is reached (see FIG. 6), or (b) a second fixed value at the minimum gray scale value 56 reached from the starting point 50. Continue until a point 54 with a grayscale value greater than the sum of the values 55 (see FIG. 7) is reached. When one of the two conditions (a) and (b) above is met, the new boundaries 58 and 59 are the last ones that have a grayscale value greater than the first value in the case of condition (a). Corresponding to the reached point 57, and in the case of condition (b), it corresponds to the point 56 having the minimum gray scale value (see FIG. 8).

  Next, addition of a new segment will be described. In the next two cases, a new segment 60 is added to one side of an existing segment 62 in the current line 61. (A) the new boundary 63 of the existing segment 62 in the current line 61 is smaller on the one side than the boundary 64 of the existing segment in the previous line 65 (this is new on the one side) Means that the point defining the boundary is included in the existing segment of the previous line), and the boundary on the one side has been reached at the stage of determining the new boundary (for condition b) Or (b) the new boundary 63 of the existing segment 62 is smaller than the boundary 64 of the existing segment in the previous line 65 on the one side, and This is the case when the space 60 between the old and new boundaries on the side is wide and the point 66 in this space has a grayscale value greater than a fixed threshold.

  FIG. 9 shows an example when a new segment is added. You will notice that the left boundary of the new line is wider than the left boundary of the previous line. There is no space on the left for adding new segments. On the other hand, the right boundary of the new line is smaller than the right boundary of the previous line. That is, there is free space that can be used for new segments. When a new segment is detected, a new boundary is searched by performing the step of finding a new boundary as previously described.

  Next, a tree structure will be described. On each line there are multiple segments that may contain the instrument tip. The tree structure allows a potential path to be tracked over time. For each new segment found, assign a unique label (or tag) and send it to the corresponding segment in the next line. The label of the “parent” is stored in the storage means. This means that the labels belonging to the previous line corresponding to the current line segment are stored in the memory means.

  Next, segment suppression will be described. A segment is suppressed as a function of the maximum grayscale value of the segment point. If a segment's maximum grayscale value point is below a fixed threshold, the segment is suppressed.

  Next, the fusion of two segments will be described. Two adjacent segments in a line can be fused. To do this, search for the point of maximum gray scale value for each segment. Next, a minimum grayscale value point between these two maximum grayscale value points is searched. Then, consider the respective difference between the grayscale value of the point of minimum grayscale value and the grayscale value of the point of two maximum grayscale values. If one of these differences is below a fixed threshold, the two segments are merged.

  Next, an assessment of the suitability of a segment that may contain the tip of a surgical instrument will be described. A “reliability score” that can assess the adequacy of the presence of a surgical instrument tip within the segment can be obtained, for example, by the average grayscale value of the voxels of the segment. This confidence score can be displayed for the operator by a color code. Segments with a reliability score lower than a fixed threshold cannot also be displayed in the output image.

  Next, smoothing of the obtained result will be described. During the smoothing stage, the center of the segment is displayed. The change along the Z-axis between one line and the next following line is thresholded only for display and to improve display quality. The threshold can vary with the amplitude of change along the Z axis. The threshold increases when the preceding change is high. Otherwise, the threshold is decreased.

  Next, the visualization of the results obtained in one embodiment of the method will be described. In the described method, starting from a 2D image and a 3D model, the current 3D position of the tip of the surgical instrument can be determined. The results obtained can be displayed in the form of a volume rendered 3D diagram 100, a curved slice image 110 with an ambiguous part, or a projection 120 of maximum intensity.

  One embodiment of the method and imaging apparatus described above can assist the operator in placing the active end of the surgical instrument in the area to be handled during the interventional procedure. Also, in one embodiment of the method and imaging apparatus, the current 3D position of one or all points of the instrument can be determined. In addition, when the single plane scanner of the acquisition system is displaced between two acquisitions of 2D images, the movement of the single plane scanner can be assimilated into movement by the patient, so the steps of the imaging method are Not changed. Finally, there are no restrictions on the method used to determine the 3D model of the vascular system.

  One embodiment of the method can also propose functions other than those described above. For example, the method can suggest a different angle when there is an ambiguous part (this means that two 2D at two different angles to determine the current 3D position of the instrument when there is an ambiguous part. Collimating around the tracked point (s) of the surgical instrument to reduce the level of x-rays emitted towards the patient Better resistance to errors (errors related to patients, projections, etc.) by dynamically correcting the errors by considering the previous position for the determination of the current position Can be proposed.

  Furthermore, an embodiment of the method can be used in an acquisition system that includes a two-plane scanner to improve the quality of results obtained with this type of acquisition system.

  To calculate the current three-dimensional (3D) position of an instrument point from a two-dimensional (2D) image, the following two conditions are considered. That is, the conditions are constraints on the position of the point of the surgical instrument tip (the tip must be located inside the blood vessel) and the continuity of instrument movement (the 2D image acquired at time t is If it is temporally close to the image acquired at time t-1, then the 3D position of the instrument point at time t is spatially close to the position of the instrument at time t-1.

  In yet another embodiment of the present invention, the condition for the position of the blood vessel in the selection stage, that the selected point in the 3D model must be located inside the blood vessel, and the selected in the 3D model. And a condition for the estimated three-dimensional position before the surgical instrument point in the selection stage that the point must be spatially close to the estimated three-dimensional position before the surgical instrument point. it can. One embodiment of the method may include calculating a probability that the three-dimensional position of the surgical instrument point corresponds to the position of the selected point in the three-dimensional model. One embodiment of the method may further include displaying selected points in the three-dimensional model in a color that depends on the calculated probability. One embodiment of the method may include generating a sequence of points (lines) including a series of points in the selection step. Each point in the point sequence corresponds to one of a plurality of points projecting into the neighborhood, and the point sequence includes a segment consisting of gray level points greater than zero. The gray level of points in the row that do not belong to a blood vessel is set to zero, and each segment corresponds to a blood vessel portion of the vascular system. One embodiment of the method may include searching for a starting point for a segment of the sequence of points in the selection step. In one embodiment of the method, the selecting step can include searching the boundary for a segment of the point sequence. In one embodiment of the method, the selecting step can include adding a new segment to the point sequence if an existing segment of the point sequence meets certain criteria. In one embodiment of the method, the selecting step includes sorting each segment of the point sequence as a function of their position within the point sequence and the position of the segment of the previous processed point sequence. Can do. In one embodiment of the method, the selecting step can include deleting a segment of the point sequence according to certain criteria. In one embodiment of the method, the selecting step can include merging adjacent segments according to certain criteria. In one embodiment of the method, the selecting step can include evaluating a segment of the point sequence, wherein the evaluation includes a color for each segment as a function of the probability of including the instrument tip point therein. Includes assigning.

Furthermore, while the present invention has been described with respect to exemplary embodiments, those skilled in the art can make various changes in function and / or method and / or result without departing from the scope of the invention, and It will be understood that the elements can be replaced with equivalents. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Accordingly, the invention is not limited to the specific embodiments disclosed as the best mode for carrying out the invention, but the invention includes all embodiments that fall within the scope of the claims. Furthermore, the terms “first”, “second”, etc. are not used to indicate order or importance, but rather the terms “first”, “second”, etc. refer to one element or feature. It is used to distinguish it from things. Further, the reference numerals in the claims corresponding to the reference numerals in the drawings are merely used for easier understanding of the present invention, and are not intended to narrow the scope of the present invention. Absent. The matters described in the claims of the present application are incorporated into the specification and become a part of the description items of the specification.

1 is a schematic diagram illustrating one embodiment of an image acquisition and processing system. 1 is a schematic diagram showing an X-ray image acquisition system. 1 is a schematic diagram showing two blood vessels of an X-ray emission means, a radiographic image acquisition means and a vascular system. 1 is a schematic diagram showing images of blood vessels with different vascular systems. 2 is a flow diagram of one embodiment of an imaging method. 1 is a schematic diagram illustrating a stage for defining a new boundary in an imaging method. 1 is a schematic diagram illustrating a stage for defining a new boundary in an imaging method. 1 is a schematic diagram illustrating a stage for defining a new boundary in an imaging method. Fig. 4 is a schematic diagram showing two lines from two 2D images, with the lower line containing one segment and the upper line containing two segments. 1 is a schematic diagram showing different types of displays of imaging methods.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Imaging apparatus 2 Image acquisition system 3 Image processing system 4 Memory means 5 Image display system 6 Object 7 Release means 8 Radiation image acquisition means 9 Support means 10 Processing means 11 Motor control apparatus 12 X-ray control apparatus 13 Image digitizing apparatus 14 Image reconstruction device 20 X-ray beam 21 Optical axis 22, 23 Blood vessel 24 Point sequence (line)
25, 26 Voxel neighborhood (subset)
27, 34 Line 28, 29, 30 Segment 31, 32, 33 Blood vessel 35 Ambiguous part 36 Path 40 Small image 50 Start point 52 point 53 First fixed value 54 point 55 Second fixed value 56 point 57 point 58, 59 New boundary 60 New segment 61 Current line 62 Existing segment 63, 64 Boundary 65 Previous line 66 Point 100 3D view 110 Curved slice image 120 Maximum intensity projection

Claims (20)

An imaging method for performing real-time display of a position of at least one point of a surgical instrument arranged in a vascular system of an object in a three-dimensional model, wherein the vascular system (6) In an imaging method in which a current three-dimensional position of the surgical instrument point is estimated,
Determining, in a two-dimensional image of the object, a region within the vicinity of the projection of the point whose position is to be estimated on the image;
3D projecting into the neighborhood on the 2D model as a function of the position of the blood vessel (22, 23) represented in the 3D model and / or the 3D position previously determined for the point of the surgical instrument Selecting a point in the model;
An imaging method comprising: The method according to claim 1, wherein the selected point in the three-dimensional model is located in a blood vessel as a condition for the position of the blood vessel (22, 23) in the selecting step. The condition for the previously estimated 3D position of the surgical instrument point in the selecting step is that the selected point in the 3D model is the 3D estimated before the surgical instrument point. The method of claim 1, wherein the method is spatially close to the location. The method of claim 1, including calculating a probability that a three-dimensional position of the surgical instrument point corresponds to a position of the selected point in a three-dimensional model. 5. The method of claim 4, comprising displaying the selected points in a three-dimensional model in a color that depends on the calculated probability. The selecting step (410) includes generating a point sequence (24) consisting of a series of points, each point in the point sequence (24) corresponding one point to a point projected into the neighborhood. The method according to claim 1. The gray level of points in the point sequence (24) that do not belong to the blood vessel (22, 23) is set to zero, so that the point sequence (24) is a point with a gray level greater than zero ( 28. A method according to claim 6, comprising segments consisting of 28, 29, 30), each segment corresponding to a vascular part (22, 23) of the vasculature. The method according to claim 6 or 7, wherein the selecting comprises searching (430) for a starting point (50) for a segment (28, 29, 30) of the sequence (24). 9. A method according to any one of claims 6 to 8, wherein the selecting comprises searching (440) for a boundary (58, 59) for the segment of the point sequence. The selecting step includes the step (450) of adding a new segment (60) to the point sequence when an existing segment (62) of the point sequence (61) meets a specific criterion. 10. The method according to any one of claims 6 to 9. The step of selecting comprises selecting each segment (28, 29, 30) of the point sequence (24) between their position within the point sequence (24) and the position of the segment of the previous processed point sequence. 11. A method according to any one of claims 6 to 10, comprising sorting (460) as a function. 12. A method according to any one of claims 6 to 11, wherein the step of selecting comprises deleting (470) the segment of the point sequence according to specific criteria. 13. A method according to any one of claims 6 to 12, wherein the selecting step includes the step of combining (470) the segments of the point sequence according to specific criteria. The selecting step includes evaluating (480) a segment of the point sequence, wherein the evaluation is applied to each segment as a function of the probability that the instrument tip is located within each segment. 14. A method according to any one of claims 6 to 13, comprising assigning a color. An imaging apparatus (1) for displaying in real time a three-dimensional model representing a vascular system of an object and displaying a position of at least one point of a surgical instrument arranged in the vascular system. ,
Means for estimating a current three-dimensional position of a point of the surgical instrument in the patient's vasculature, the means for estimating comprising:
Means (10) for determining a region in the vicinity of a projection on the image of a point whose position should be estimated in the two-dimensional image of the object;
Projecting into the neighborhood on the two-dimensional model as a function of the position of the blood vessel (22, 23) represented in the three-dimensional model and / or as a function of the previous three-dimensional position estimated for the point of the surgical instrument Means for selecting a point in the three-dimensional model to be
An imaging apparatus (1) comprising: The imaging apparatus according to claim 15, further comprising means for executing the medical imaging method according to claim 2. 15. A computer program comprising program code means for executing the method of any one of claims 2 to 14 when the program is executed on a computer. 15. A computer program product comprising a computer usable medium having computer readable program code means embodied in the medium and performing the steps of the method according to any one of claims 2-14. A computer readable medium having computer readable program code means embodied in the medium and performing the steps of the method according to any one of claims 2 to 14. An article of manufacture for use in a computer system. 15. A program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform the steps of the method according to any one of claims 2-14. Program storage device.