Method and apparatus for determining the position of a surgical tool relative to a target volume inside an animal body

Abstract

The invention relates to a method for determining the position of a surgical tool relative to a target volume inside an animal body according to a pre-plan comprising the steps of i) obtaining a plurality of two-dimensional images of said target volume using imaging means, each 2D-image being represented by an image data slice I(x,y,z); ii) reconstructing from said plurality of image data slices I(x,y,z) a three-dimensional image of said target volume using transformation means, said 3D-image being represented by a volumetric image data array V(x,y,z); iii) displaying said three-dimensional image of said target volume to an user using displaying means.

Claims

1. A surgical imaging system for determining and displaying, within a computer-generated display, a current position of a surgical tool relative to a pre-planned position of the surgical tool, the surgical imaging system comprising: an imaging device that obtains a three-dimensional image of a target volume within the patient; and a controller connected to the imaging device that: generates a first display signal for displaying, on a display device of a computer system, the three-dimensional image of the target volume, where the displayed three-dimensional image includes a three-dimensional imaginary representation of the surgical tool inserted in the target volume at a position corresponding to at least one preplanned position of the surgical tool; receives a user selection interacting with the three-dimensional image on the display device that identifies a selected location in the displayed three-dimensional image; generates, responsive to receiving the user selection that identifies the selected location in the displayed three-dimensional image, a control signal causing the imaging device to capture a corresponding location on the patient matching the selected location in the displayed three-dimensional image; and controls the imaging device to obtain a real-time two-dimensional image of the corresponding location on the patient; and generates a second display signal for displaying in the real-time two-dimensional image a depiction of the surgical tool at the current position in the patient, and wherein the second display signal is configured to display a visual feedback, via the display device of the computer system, that indicates the current position of the surgical tool in the patient relative to the at least one preplanned position of the surgical tool.

2. The system of claim 1, wherein the selected location includes the at least one preplanned position of the surgical tool.

3. The system of claim 1, wherein the system includes an adjustor that controller controls to adjust the imaging device based upon the control signal.

4. The system of claim 1, wherein the system includes an adjustor that controller controls to adjust the surgical tool to correct the actual position to correspond with the at least one preplanned position of the surgical tool.

5. The system of claim 1, wherein the user selection is received from a display pointer, a mouse pointer, or a keyboard.

Description

(1) The invention will now be described in combination with a drawing, which drawing shows in:

(2) FIG. 1 shows in very schematic form a known radiation treatment device using imaging means;

(3) FIG. 2 a block diagram depicting a first embodiment of the method according to the invention;

(4) FIG. 3 a block diagram depicting a second embodiment of the method according to the invention;

(5) FIG. 4 a more detailed embodiment of an apparatus according to the invention;

(6) FIG. 5 a further more detailed embodiment of an apparatus according to the invention.

(7) FIG. 1 shows in very schematic form various elements of a known radiation treatment device using a template-assembly for implanting one or more energy emitting sources, e.g. radioactive seeds towards a desired location within an animal body, for example into a prostate gland using ultrasound imaging means.

(8) The known device shown in FIG. 1 operates as follows. A patient 1 is under spinal or general anaesthesia and lies on the operating table 2 in lithotomy position. The (ultrasound) imaging probe 7 is introduced into the rectum and the probe is connected via signal line 7a with a well known image screen, where an image may be seen of the inside of the patient in particular of the prostate gland 11 as seen from the point of view of the imaging probe 7. The template assembly 5 is attached to the stepping device 4, thereby insuring the correlation of the ultrasound image geometry and the template-assembly 5. Subsequently further needles 10 are introduced in the body and the prostate gland under ultrasound guidance one by one.

(9) Moving the imaging probe with the drive means 4 longitudinally within the rectum controls the needle depths of each needle 10. After all needles 10 have been placed, their positions relative to the prostate gland 11 are determined in at least one of several known ways. In a known way the therapy planning module 12a determines how the needles 10 are to be placed in the prostate and how many radiation emitting sources are to be placed in what order in each of the needles 10. The information about the desired placement of the radioactive seeds in the needles 10 is used to control the seed loading unit 8.

(10) FIGS. 2 and 3 disclose a block diagram depicting a first and a second embodiment of the method according to the invention. In the Figures with reference numeral 20 imaging means are depicted, which in FIG. 2 consists of imaging means based on magnetic resonance imaging. The MRI means depicted with reference numeral 20 in FIG. 2 generally comprises a power source for energizing the gradient coils G.sub.x, G.sub.y, G.sub.z. The gradient coils are in FIG. 2 depicted with reference numeral 21 (G.sub.x−G.sub.y−G.sub.z).

(11) When independently energized, the three gradient coils produce a linearly variable magnetic field in any direction, where the net gradient is equal to √(G.sub.x.sup.2+G.sub.y.sup.2+G.sub.z.sup.2). With an appropriate design, the gradient coils G.sub.x, G.sub.y, G.sub.z create a magnetic field, that linearly varies in strength versus distance over a predefined field of view. When superimposed upon a homogeneous magnetic field B.sub.o not shown in the figures positive fields add to B.sub.o and negative gradient fields reduce B.sub.o

(12) The resulting gradient is linear, position-dependent and it causes protons to alter their precessional frequency corresponding to their position along the applied gradient in a known and predictable way. Any gradient direction is possible by superimposition of the three MRI involves RF excitations at the Larmor-frequency of the protons combined with magnetic field gradients to localize the signal from each individual volume element after the excitation.

(13) The MR imaging means 20 are connected to a central processing unit CPU 22 intended for operating the imaging means 20.

(14) Central processing unit 22 interacts with transformation means 23, which means include digitizer and image processing units for digitizing and further processing the two-dimensional images generated by said imaging means 20.

(15) Hereto the transformation means 23 may include storage means (for example physical memory) for storing the two-dimensional images obtained from the imaging means 20 as 2D information. The transformation means 23 capture and digitize the two-dimensional information transfers the 2D information to a computer system 24 for planning and visualisation purposes. Also in computer system 24 said two-dimensional image information is transformed into a three-dimensional image of the target volume being imaged.

(16) Said computer system 24 may include planning software for pre-planning for example a radioactive treatment on the target volume being imaged by imaging means 20.

(17) As will be elucidated in more detail with reference to FIG. 4 the method according to the invention is further characterized in that within said three-dimensional image being visualized in said computer system 24 a specific imaginary target location is to be selected using suitable selecting means. Upon said selection in said computer means 24 the central processing unit 22 is provided with control signals from said computer system 24, which CPU 22 in turn controls the MR imaging means 20 for obtaining a two-dimensional image in which image the target location within the target volume corresponding with the imaginary target location selected within said three-dimensional image is obtained.

(18) In FIG. 3 the method according to the invention is described using an ultrasound probe 20 having an ultrasound transducer 21 which may consists of multiple ultrasound transducer elements 21.sub.n. The ultrasound probe 20 is provided with drive means (not shown) for displacing the transducer element 21 in longitudinal direction or in rotational direction relative to the target volume to be imaged.

(19) Ultrasound wave signals emitted by the transducer element 21 towards the target volume to be examined are orientated in a physical interaction field that intersects the target volume to be imaged as a slice. Within said physical interaction field the ultrasound wave signals can be transmitted, absorbed or reflected dependent on the composition of the tissue.

(20) The reflected ultrasound wave signals are received by the transducer element 21 and fed to an ultrasound processing unit (transformation means) 23 for generating a two-dimensional image corresponding to the physical interaction field (image slice) of the target volume. By rotating the transducer element 21 multiple two-dimensional image slices spaced apart from each other are obtained.

(21) As in FIG. 2, also in FIG. 3 unit 24 transforms these two-dimensional image slices into a three-dimensional image, which is used by said computer system 24 for planning and visualisation purposes.

(22) By selecting an imaginary target location within said three-dimensional image being displayed by said computer system 24 control signals are generated and fed to the control means of the ultrasound probe 20. Based on said control signals the transducer element 21 is displaced in longitudinal or rotational orientation relative to the target volume such that the physical interaction field of the ultrasound wave signals propagating towards the target volume corresponds with the imaginary target location selected within said three-dimensional image.

(23) Hence one two-dimensional image is obtained of said specific target location within the target volume corresponding with the imaginary target location selected within said three-dimensional image.

(24) In FIG. 4 a more detailed embodiment of an apparatus implementing the method according to the invention is disclosed. For a proper understanding likewise parts are described with identical reference numerals.

(25) In FIG. 4 reference numeral 30 depicts schematically an animal body (a patient), whereas reference numeral 31 depicts the target volume under examination, for example an internal organ contained in said animal body 30. Referring to FIG. 1 said organ 31 can be the prostate gland of a male person 30, which person has to undergo a radioactive therapy treatment session by implanting—using multiple implant needles 28.sub.n—one or more energy emitting sources, for example radioactive seeds, through said implant needles 28.sub.n at desired locations within the prostate 31.

(26) For performing the imaging technique as used with the method and apparatus according to the invention magnetic resonance imaging means 20 (MRI) are used. As already described in FIG. 2 each MRI means comprise multiple gradient coils 21 (G.sub.x, G.sub.y, G.sub.z), which coils can be energized or activated separately depending on the image acquisition to be performed.

(27) The method and apparatus according to the invention are based on the imaging technique to obtain a three-dimensional image of a specific target volume 31 inside an animal body 30 by generating a plurality of two-dimensional image slices 31.sub.2D with a proper operation of the imaging means 20.

(28) For obtaining multiple two-dimensional image slices 31.sub.2D the gradient coils 21 (G.sub.x, G.sub.y, G.sub.z) are controlled in a such manner that a physical interaction field intersecting or slicing the target volume 31 corresponding with an image slice is created.

(29) The magnetic field and RF created by said magnetic resonance imaging means interact with the tissue of the target volume 31 in said physical interaction field. The interaction between the magnetic field generated by the gradient coils 21 (G.sub.x, G.sub.y, G.sub.z) is collected by a receiver coil 25 of the magnetic resonance imaging means 20 resulting in a two-dimensional image corresponding with the visual representation of the target volume 31 within said slice (physical interaction field).

(30) A plurality of two-dimensional image slices 31.sub.2D are collected and stored in suitable storage means in a processing unit 33. The plurality of two-dimensional image slices 31.sub.2D are transformed by computer system 24 using suitable transformation means into a three-dimensional image of the target volume 31. The three-dimensional image is stored within computer system 24 and displayed on a display 24a (reference numeral 31.sub.3D).

(31) This transformation technique for generating a three-dimensional image from a plurality of two-dimensional image slices is known in the art.

(32) According to the invention it is intended to manipulate the imaging means 20 by selecting a specific imaginary target location 37 within the three-dimensional image 31.sub.3D being displayed on display 24a. The target location being selected is in FIG. 4 depicted with a circle 37. The selection of said imaginary target location 37 can be performed using specific selection means like for example a mouse pointer a display pointer (for example a light pen) or an other suitable input device like a computer keyboard.

(33) The selection of the specific imaginary target location or region 37 triggers or activates control means 22 (central processing unit) for controlling the imaging means 20. In FIG. 4, due to the selection of specific target region 37 within the imaginary three-dimensional image 31.sub.3D the magnetic resonance imaging means 20 are controlled/activated such that the gradient coils 21 (G.sub.x, G.sub.y, G.sub.z) are activated such, that one two-dimensional image 31.sub.2D′ of said imaginary target region 37 as selected is obtained via transformation means 23 where said single two-dimension image slice is imaged and digitized for further displaying purposes.

(34) This digitized two-dimensional image 31.sub.2D′ is displayed to the user (diagnostician) using display means 34. Said display means 34 can be a separate display device being part of transformation means 23, but it can also be implemented in the display 24b of the computer system 24. In the latter case display 24b is divided in several sub-windows, wherein each sub-window is used for displaying the three-dimensional image 31.sub.3D or the single two-dimensional image 31.sub.2D′ of the specific target region 37 as selected in said three-dimensional image 31.sub.3D respectively.

(35) In a likewise manner is it possible to implement the method and apparatus in combination with ultrasound imaging means as depicted in FIG. 5. In this FIG. 5 ultrasound image slice are produced using the transducer elements 21.sub.n of the ultrasound probe 20. Said probe 20 is—like in FIG. 1—inserted into the rectum of a male patient 30 for ultrasound imaging of the internal organs and more in particular the prostate gland 31.

(36) Ultrasound wave signals 26 are transmitted by the transducer elements 21.sub.n (of ultrasound transducer 21) towards the prostate gland 31 (target volume) and reflected ultrasound wave signals are received therefrom. The reflected ultrasound wave signals received by the ultrasound probe 20 are processed by the ultrasound processing unit (transformation means) 23 and a two-dimensional image of the target volume under examination is formed. By rotating the ultrasound probe 20 (the ultrasound transducer 21) relative to the target volume subsequent two-dimensional image slices 31.sub.2D are obtained and processed by ultrasound processing unit (transformation means) 23.

(37) The transformation means 23 capture and digitize the two-dimensional image information and transfers the 2D information to a computer system 24 for planning and visualisation purposes. Also in computer system 24 said plurality of two-dimensional image slices 31.sub.2D are transformed into a three-dimensional image 31.sub.3D of the target volume 31 being imaged. Said computer system 24 may include planning software for pre-planning for example a radioactive treatment on the target volume 31 being imaged by imaging means 20.

(38) Similar to the embodiment of FIG. 4 the ultrasound imaging probe 20 can be manipulated by selecting a specific imaginary target location 37 within the three-dimensional image 36 being displayed on display 24a. The target location being selected is in FIG. 5 depicted with a circle 37.

(39) Due to the selection of the specific imaginary target location or region 37 the ultrasound probe 20 is controlled by computer system 24. The ultrasound transducer 21 can be displaced in longitudinal and rotation manner relative to the target volume 31 in order to create a psychical interaction field through the target volume 31 corresponding to the selected imaginary target location 37. The re-orientation of the ultrasound transducer 21 relative to the target volume generates one two-dimensional image 31.sub.2D′ of said imaginary target region 37 as selected. Said single two-dimensional image 31.sub.2D′ is captured and digitized by transformation means 23 for further displaying purposes.

(40) This digitized two-dimensional image 31.sub.2D′ is displayed to the user (diagnostician) using display means 34. Said display means 34 can be a separate display device being part of transformation means 23, but it can also be implemented in the display 24b of the computer system 24. In the latter case display 24b is divided in several sub-windows, wherein each sub-window is used for displaying the three-dimensional image 31.sub.3D or the single two-dimensional image 31.sub.2D′ of the specific target region 37 as selected in said three-dimensional image 31.sub.3D respectively.

(41) Hence with the method and apparatus according to the invention it is possible to control the imaging means 20 (MRI or ultrasound) in an indirect remote manner by selecting an image direction in the three-dimensional image of the target volume 31 within the animal body 30. An user can control the magnetic resonance imaging means 20 from behind display 24a using the computer system 24 and control means 22.

(42) This imaging technique is beneficial for example medical applications using a pre-plan, for example a pre-planned therapy treatment and more in particularly for use with the brachytherapy treatment of prostate cancer using the device as depicted in FIG. 1.

(43) For a treatment of prostate cancer using multiple implant needles 28.sub.n to be inserted inside a prostate gland 31 of a male person 30 the desired, pre-planned location/depth of the multiple implant needles 28.sub.n is pre-planned according to a desired-treatment therapy using known treatment planning software contained for example in computer system 24. The implant needles 28.sub.n are considered a surgical tool, and are displayed as imaginary surgical tools 28.sub.n′ and projected on said three-dimensional image 31.sub.3D of the prostate gland 31.

(44) Likewise it is possible to project a frame 24b of vertical and horizontal lines on said three-dimensional image 31.sub.3D, which frame 24b may correspond with aperture or grid orientation on template-assembly 5 as depicted in FIG. 1. By selecting a specific grid position within frame 24b a specific implant needle 28.sub.1 (for example the implant needle depicted with reference numeral 29) is selected and its insertion through the animal body 30 towards its desired, pre-planned depth within the prostate gland 31 can be monitored with the single two-dimensional image 31.sub.2D′.

(45) The selection of the grid position within frame 24b corresponding with specific implant needle 29 leads to a remote control of imaging means 20 via control means 22 resulting in one two-dimensional image 31.sub.2D′ depicting the image slice intersecting with said grid position.

(46) As with this imaging technique the insertion of the specific implant needle 29 can be monitored in real-time it is possible to control via control line 35 the needle insertion means 36 until said implant needle 29 reaches its desired, pre-planned depth relative to the prostate gland 31.

(47) Subsequent energy emitting sources, for example radioactive seeds, can be inserted through said implant needle 29 for performing a radioactive therapy treatment as pre-planned using planning software contained in computer system 24.