Patent Publication Number: US-2023148138-A1

Title: Ablation planning system

Description:
FIELD OF THE INVENTION 
     The invention relates to tissue ablation system, in particular to the planning of ablations. 
     BACKGROUND OF THE INVENTION 
     In tissue ablation, an ablation probe is inserted into a subject to locally ablate tissue. Various types probes exist for ablating tissue. For example, heat, cold, radio frequency power, and lasers can all be used to ablate tissue. 
     United States patent application publication US20150320509A1 discloses a system for surgical procedure assistance. In one example, a first image of a patient captured prior to a surgical procedure is received. A treatment plan is generated based on the first image. The treatment plan includes information related to one or more surgical instruments. A second image of the patient captured after the surgical procedure has been initiated is received. The treatment plan is dynamically adjusted based on a pose of any of the one or more surgical instruments identified from the second image. A third image of the patient captured after a lesion is treated by at least one of the surgical instruments based on the adjusted treatment plan is received. Whether a further treatment to the lesion is needed is determined based on the third image. Upon determining a further treatment is needed, an updated treatment plan is dynamically generated based on the third image. 
     SUMMARY OF THE INVENTION 
     The invention provides for a medical instrument, a computer program, and a method in the independent claims. Embodiments are given in the dependent claims. 
     A difficult part of accurately performing tissue ablation is accurately planning the ablations. Embodiments may provide for a system which aids in the planning of ablations. An anatomical segmentation and a target zone segmentation are received and then used to render several three-dimensional models on a planning graphical user interface. A first three-dimensional model shows the anatomical segmentation and the target zone segmentation. A second three-dimensional model shows a remaining portion of the target zone segmentation. An ablation zone selector on the planning graphical user interface enables the selection of an ablation zone. The system then updates the remaining portion (the second three-dimensional model) by removing the ablation zone from the remaining portion. This process may be repeated to plan the entire ablation. 
     In one aspect the invention provides for a medical instrument that comprises a user interface. The user interface comprises a display. The medical instrument further comprises a memory storing machine-executable instructions. The medical instrument further comprises a computational system that is configured for controlling the medical instrument. The medical instrument may take different forms in different examples. In some examples the medical instrument is a workstation or computing system. In other examples the medical instrument may include other components such as an ablation system. 
     Execution of the machine-executable instructions causes the computational system to receive an anatomical segmentation identifying a location of an anatomical structure. The anatomical segmentation could be in the form of a segmentation of a medical image. In other examples the anatomical segmentation is simply identification of a region of the anatomical structure independent of a medical image. Execution of the machine-executable instructions further causes the computational system to receive a target zone segmentation identifying a location of a volume at least partially within the anatomical segmentation. This volume may also be referred to as the target zone. 
     Execution of the machine-executable instructions further causes the processor to display a planning graphical user interface using the display. The planning graphical user interface comprises a first panel configured for rendering a cross-sectional view of the anatomical segmentation and the target zone segmentation. The planning graphical user interface further comprises a second panel configured for displaying a rendering of a first three-dimensional model of the anatomical segmentation and the target zone segmentation. 
     The rendering of the first three-dimensional model may for example be a two-dimensional rendering of the three-dimensional model. In other examples a three-dimensional rendering may be used. The planning graphical user interface further comprises a third panel configured for rendering a second three-dimensional model of a remaining portion of the target zone segmentation. The planning graphical user interface further comprises an ablation selector configured for providing an ablation zone descriptive of a volume at least partially within the remaining portion. 
     Execution of the machine-executable instructions further causes the computational system to repeatedly receive the ablation zone from the ablation selector. Execution of the machine-executable instructions further causes the computational system to repeatedly update the remaining portion by removing the ablation zone from the remaining portion. This embodiment may be beneficial because it may aid in the planning of an ablation. The display of the remaining portion may aid in the selection of the proper ablation zone. 
     In another embodiment the ablation selector is configured to receive a selection of a volume within the remaining portion. Execution of the machine-executable instructions further causes the processor to generate the ablation zone in response to receiving the selection of a volume from the ablation selector. For example, the user interface may display the possible volumes which could be ablated. 
     In another embodiment the ablation selector is configured for receiving a selection of a trajectory that intersects the remaining portion. Execution of the machine-executable instructions further causes the processor to generate the ablation zone in response to receiving the selection of the trajectory from the ablation selector. A particular ablation system may have a guide or set insertion points where a probe may be inserted. The user interface may for example display the possible trajectories which a physician or other operator can choose from and can then plan the ablation and see the projected results. 
     In another embodiment the memory further comprises an automated planning module configured for outputting the ablation zone in response to inputting the remaining portion. The ablation selector is configured to receive an automated planning request. Execution of the machine-executable instructions further causes the processor to generate the ablation zone by inputting the remaining portion into the automated planning module in response to receiving the automated planning request. The automated planning module may for example be implemented in different ways. In one example a neural network could be used to choose the ablation zone in response to the existing remaining portion. In other examples the automated planning module may use a search algorithm that looks at all of the possible choices and then chooses an ablation zone which matches predetermined criteria. For example, the ablation zone may be chosen such that the maximum amount of tissue is ablated. 
     In another embodiment execution of the machine-executable instructions further causes the processor to generate insertion instructions for inserting the ablation probe in response to receiving the ablation zone from the ablation selector. The medical instrument may for example be useful in planning an ablation operation. During or after the planning has taken place the insertion instructions may be provided for use by the physician or medical technician. 
     In another embodiment the medical instrument comprises an ablation probe system comprising an ablation probe. The medical instrument further comprises an ablation probe tracking system registered to the anatomical segmentation. The ablation probe tracking system may for example be implemented in a variety of different ways. There may for example be a radio-frequency tag or other transmitter on the ablation probe which enables tracking. In other cases, the ablation probe tracking system may track the probe at least partially using an input medical image such as from a CT system or a magnetic resonance imaging system. 
     Execution of the machine-executable instructions further causes the computational system to receive probe tracking data from the ablation probe. Execution of the machine-executable instructions further causes the computational system to update the remaining portion using the probe tracking data. When the ablation probe is actually inserted into a subject the actual area which the ablation probe reaches may be different than what is intended. In this embodiment the remaining portion is updated so that it matches the actual position of the ablation probe. 
     In another embodiment the ablation probe is a radio-frequency ablation probe. 
     In another embodiment the ablation probe is a microwave ablation probe. 
     In another embodiment the ablation probe is a high-intensity focused ultrasound ablation probe. 
     In another embodiment the ablation probe is a focal or focused laser ablation probe. 
     In another embodiment the ablation probe is an irreversible electroporation probe. 
     In another embodiment the ablation probe is a cryo-ablation probe. 
     In another embodiment the medical instrument further comprises a guidance medical imaging system. Execution of the machine-executable instructions further causes the computational system to control the guidance medical imaging system to acquire real-time guidance medical imaging data during acquisition of tracking data from the ablation probe. Execution of the machine-executable instructions further causes the computational system to display the real-time guidance medical imaging data on the user interface in real time. The real-time guidance medical image data may for example be used to track and locate the position of the probe exactly and also update the remaining portion. 
     In another embodiment the guidance medical imaging system is a computed tomography system. 
     In another embodiment the guidance medical imaging system is an ultrasound imaging system. 
     In another embodiment the guidance medical imaging system is a magnetic resonance imaging system. 
     In another embodiment the guidance medical imaging system is an X-ray fluoroscope. 
     In another embodiment execution of the machine-executable instructions further causes the computational system to receive a planning magnetic resonance image descriptive of a region of interest of a subject. Anatomical segmentation identifies a location of an anatomical structure within the planning magnetic resonance image. The first panel is further configured for rendering a cross-sectional view of the planning magnetic resonance image. 
     In another embodiment the memory further stores an automated segmentation algorithm configured for generating the anatomical segmentation and/or the target zone segmentation in response to inputting the planning magnetic resonance image. Execution of the machine-executable instructions further causes the processor to generate the anatomical segmentation and/or the target zone segmentation by inputting the planning magnetic resonance image into the automated segmentation algorithm. 
     The automated segmentation algorithm may be implemented in a variety of ways. In one example the automated segmentation algorithm is implemented as a neural network. In other examples the automated segmentation algorithm may perform the segmentation by using an anatomical atlas. In another example the automated segmentation algorithm uses a deformable shape model to perform the segmentation. 
     In another embodiment the medical instrument further comprises a planning magnetic resonance image system configured for acquiring planning k-space data of the subject. The label planning on the planning magnetic resonance image is intended to indicate a particular magnetic resonance imaging system. Likewise, the term planning k-space data is intended to indicate specific k-space data and the word planning is used as a label. The memory further comprises planning pulse sequence commands configured for controlling the magnetic resonance imaging system to acquire the planning k-space data. 
     Execution of the machine-executable instructions further causes the computational system to control the planning magnetic resonance imaging system with the planning pulse sequence commands to acquire the planning k-space data. Execution of the machine-executable instructions further causes the computational system to reconstruct the planning magnetic resonance image from the planning k-space data. 
     In another embodiment the display is a three-dimensional display. This for example may be a display that is provided by goggles or other virtual reality or augmented reality system. Execution of the machine-executable instructions further causes the processor to render the first three-dimensional model and the second three-dimensional model three-dimensionally using the three-dimensional display. 
     In another aspect the invention provides for a computer program that comprises machine-executable instructions for execution by a computational system controlling a medical instrument. The medical instrument comprises a user interface comprising a display. Execution of the machine-executable instructions causes the computational system to receive an anatomical segmentation identifying a location of an anatomical structure. Execution of the machine-executable instructions further causes the computational system to receive a target zone segmentation identifying a location of a volume at least partially within the anatomical segmentation. Execution of the machine-executable instructions further causes the computational system to display a planning graphical user interface using the display. 
     The planning graphical user interface comprises a first panel configured for rendering a cross-sectional view of the anatomical segmentation and the target zone segmentation. The planning graphical user interface further comprises a second panel configured for displaying a rendering of the first three-dimensional model of the anatomical segmentation and the target zone segmentation. The planning graphical user interface further comprises a third panel configured for rendering a second three-dimensional model of the remaining portion of the target zone segmentation. The planning graphical user interface further comprises an ablation selector configured for providing an ablation zone descriptive of a volume at least partially within the remaining portion. 
     Execution of the machine-executable instructions further causes the computational system to repeatedly receive the ablation zone from the ablation selector. Execution of the machine-executable instructions further causes the computational system to repeatedly update the remaining portion by removing the ablation zone from the remaining portion. 
     In another aspect the invention provides for a method of operating a medical instrument. The medical instrument comprises a user interface. The user interface comprises a display. The method comprises receiving an anatomical segmentation identifying a location of an anatomical structure. The method further comprises receiving a target zone segmentation identifying a location of a volume at least partially within the anatomical segmentation. The method further comprises displaying a planning graphical user interface using the display. The planning graphical user interface comprises a first panel configured for rendering a cross-sectional view of the anatomical segmentation and the target zone segmentation. 
     The planning graphical user interface further comprises a second panel configured for displaying a rendering of a first three-dimensional model of the anatomical segmentation and the target zone segmentation. The planning graphical user interface further comprises a third panel configured for rendering a second three-dimensional model of a remaining portion of the target zone segmentation. The planning graphical user interface further comprises an ablation selector configured for providing an ablation zone descriptive of a volume at least partially within the remaining portion. The method further comprises repeatedly receiving the ablation zone from the ablation selector. The method further comprises repeatedly updating the remaining portion by removing the ablation zone from the remaining portion. 
     It is understood that one or more of the aforementioned embodiments of the invention may be combined as long as the combined embodiments are not mutually exclusive. 
     As will be appreciated by one skilled in the art, aspects of the present invention may be embodied as an apparatus, method or computer program product. Accordingly, aspects of the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system.” Furthermore, aspects of the present invention may take the form of a computer program product embodied in one or more computer readable medium(s) having computer executable code embodied thereon. 
     Any combination of one or more computer readable medium(s) may be utilized. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A ‘computer-readable storage medium’ as used herein encompasses any tangible storage medium which may store instructions which are executable by a processor or computational system of a computing device. The computer-readable storage medium may be referred to as a computer-readable non-transitory storage medium. The computer-readable storage medium may also be referred to as a tangible computer readable medium. In some embodiments, a computer-readable storage medium may also be able to store data which is able to be accessed by the computational system of the computing device. Examples of computer-readable storage media include, but are not limited to: a floppy disk, a magnetic hard disk drive, a solid state hard disk, flash memory, a USB thumb drive, Random Access Memory (RAM), Read Only Memory (ROM), an optical disk, a magneto-optical disk, and the register file of the computational system. Examples of optical disks include Compact Disks (CD) and Digital Versatile Disks (DVD), for example CD-ROM, CD-RW, CD-R, DVD-ROM, DVD-RW, or DVD-R disks. The term computer readable-storage medium also refers to various types of recording media capable of being accessed by the computer device via a network or communication link. For example, data may be retrieved over a modem, over the internet, or over a local area network. Computer executable code embodied on a computer readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wire line, optical fiber cable, RF, etc., or any suitable combination of the foregoing. 
     A computer readable signal medium may include a propagated data signal with computer executable code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A computer readable signal medium may be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. 
     ‘Computer memory’ or ‘memory’ is an example of a computer-readable storage medium. Computer memory is any memory which is directly accessible to a computational system. ‘Computer storage’ or ‘storage’ is a further example of a computer-readable storage medium. Computer storage is any non-volatile computer-readable storage medium. In some embodiments computer storage may also be computer memory or vice versa. 
     A ‘computational system’ as used herein encompasses an electronic component which is able to execute a program or machine executable instruction or computer executable code. References to the computational system comprising the example of “a computational system” should be interpreted as possibly comprising more than one computational system or processing core. The computational system may for instance be a multi-core processor. A computational system may also refer to a collection of computational systems within a single computer system or distributed amongst multiple computer systems. The term computational system should also be interpreted to possibly refer to a collection or network of computing devices each comprising a processor or computational systems. The machine executable code or instructions may be executed by multiple computational systems or processors that may be within the same computing device or which may even be distributed across multiple computing devices. 
     Machine executable instructions or computer executable code may comprise instructions or a program which causes a processor or other computational system to perform an aspect of the present invention. Computer executable code for carrying out operations for aspects of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C++ or the like and conventional procedural programming languages, such as the “C” programming language or similar programming languages and compiled into machine executable instructions. In some instances, the computer executable code may be in the form of a high-level language or in a pre-compiled form and be used in conjunction with an interpreter which generates the machine executable instructions on the fly. In other instances, the machine executable instructions or computer executable code may be in the form of programming for programmable logic gate arrays. 
     The computer executable code may execute entirely on the user&#39;s computer, partly on the user&#39;s computer, as a stand-alone software package, partly on the user&#39;s computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user&#39;s computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). 
     Aspects of the present invention are described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It is understood that each block or a portion of the blocks of the flowchart, illustrations, and/or block diagrams, can be implemented by computer program instructions in form of computer executable code when applicable. It is further under stood that, when not mutually exclusive, combinations of blocks in different flowcharts, illustrations, and/or block diagrams may be combined. These computer program instructions may be provided to a computational system of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the computational system of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. 
     These machine executable instructions or computer program instructions may also be stored in a computer readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks. 
     The machine executable instructions or computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. 
     A ‘user interface’ as used herein is an interface which allows a user or operator to interact with a computer or computer system. A ‘user interface’ may also be referred to as a ‘human interface device.’ A user interface may provide information or data to the operator and/or receive information or data from the operator. A user interface may enable input from an operator to be received by the computer and may provide output to the user from the computer. In other words, the user interface may allow an operator to control or manipulate a computer and the interface may allow the computer indicate the effects of the operator&#39;s control or manipulation. The display of data or information on a display or a graphical user interface is an example of providing information to an operator. The receiving of data through a keyboard, mouse, trackball, touchpad, pointing stick, graphics tablet, joystick, gamepad, webcam, headset, pedals, wired glove, remote control, and accelerometer are all examples of user interface components which enable the receiving of information or data from an operator. 
     A ‘hardware interface’ as used herein encompasses an interface which enables the computational system of a computer system to interact with and/or control an external computing device and/or apparatus. A hardware interface may allow a computational system to send control signals or instructions to an external computing device and/or apparatus. A hardware interface may also enable a computational system to exchange data with an external computing device and/or apparatus. Examples of a hardware interface include, but are not limited to: a universal serial bus, IEEE 1394 port, parallel port, IEEE 1284 port, serial port, RS-232 port, IEEE-488 port, Bluetooth connection, Wireless local area network connection, TCP/IP connection, Ethernet connection, control voltage interface, MIDI interface, analog input interface, and digital input interface. 
     A ‘display’ or ‘display device’ as used herein encompasses an output device or a user interface adapted for displaying images or data. A display may output visual, audio, and or tactile data. Examples of a display include, but are not limited to: a computer monitor, a television screen, a touch screen, tactile electronic display, Braille screen, Cathode ray tube (CRT), Storage tube, Bi-stable display, Electronic paper, Vector display, Flat panel display, Vacuum fluorescent display (VF), Light-emitting diode (LED) displays, Electroluminescent display (ELD), Plasma display panels (PDP), Liquid crystal display (LCD), Organic light-emitting diode displays (OLED), a projector, and Head-mounted display. 
     K-space data is defined herein as being the recorded measurements of radio frequency signals emitted by atomic spins using the antenna of a Magnetic resonance apparatus during a magnetic resonance imaging scan. Magnetic resonance data is an example of tomographic medical image data. 
     A Magnetic Resonance Imaging (MRI) image, MR image, or magnetic resonance imaging data is defined herein as being the reconstructed two- or three-dimensional visualization of anatomic data comprised within the magnetic resonance imaging data. This visualization can be performed using a computer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following preferred embodiments of the invention will be described, by way of example only, and with reference to the drawings in which: 
         FIG.  1    illustrates an example of a medical instrument; 
         FIG.  2    illustrates a further example of a medical instrument; 
         FIG.  3    shows a flow chart which illustrates a method of operating the medical instrument of  FIG.  1    or  FIG.  2   ; 
         FIG.  4    illustrates a further example of a medical instrument; 
         FIG.  5    illustrates a further example of a medical instrument; 
         FIG.  6    illustrates an example of a planning magnetic resonance image; 
         FIG.  7    shows a ultrasound image with the segmentations of  FIG.  6   ; 
         FIG.  8    shows a rendering of the second three-dimensional model; 
         FIG.  9    shows a further rendering of the second three-dimensional model; and 
         FIG.  10    shows a rendering of a transperineal grid template. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Like numbered elements in these figures are either equivalent elements or perform the same function. Elements which have been discussed previously will not necessarily be discussed in later figures if the function is equivalent. 
       FIG.  1    illustrates an example of a medical instrument  100 . The medical instrument  100  is shown as comprising in this particular example a computer  102 . The computer  102  is shown as comprising an optional hardware interface  104 . The hardware interface  104  may for example be used to control other components of the medical instrument  100  if they are present. The medical instrument  100  is further shown as comprising a computational system  106 . The computational system  106  is intended to represent one or more computational systems or devices such as processors of other computers. The computational system  106  may be distributed also in multiple locations. The medical instrument  100  is further shown as comprising a user interface  108 . The user interface comprises a planning graphical user interface  112 . The medical instrument  100  is further shown as comprising a memory  110 . The memory  110  represents any memory that is accessible to the computational system  106 . 
     The medical instrument  100  illustrated in  FIG.  1    may be a component or part of a variety of different types of systems. In one example the medical instrument  100  is a workstation or a computing device which is used for planning. In another example the medical instrument  100  may be integrated with an ablation probe or ablation probe system. In another example the medical instrument  100  may be integrated with a magnetic resonance imaging or other medical imaging system. 
     The memory  110  is further shown as comprising an optional automated planning module  126 . The automated planning module may be configured for outputting a selected ablation zone in response to inputting the remaining portion. The memory  128  is further shown as comprising insertion instructions  128  which may be presented on an optional display for insertion instructions  148 . For example, the insertion instructions  128  may comprise instructions on where and how far to insert an ablation probe. 
     The planning graphical user interface  112  is shown as comprising a first panel  130 , a second panel  132 , and a third panel  134 . The first panel is configured for rendering a cross-sectional view of the anatomical segmentation  136  and a cross-sectional view of the target zone segmentation  138 . The first panel  130  may also be configured for displaying a cross-sectional of a medical image such as a magnetic resonance image with these two cross-sectional views of the segmentations  136 ,  138 . 
     The second panel  132  is configured for displaying a rendering of a first three-dimensional model  140 . The first three-dimensional model  140  is a three-dimensional model of the anatomical segmentation  122  and the target zone segmentation  124 . The second panel  132  may be useful because it may display the three-dimensional models of the segmentations  122  and  124  without any other medical imaging data and also in the three-dimensional means. 
     The third panel  134  displays a second three-dimensional model  142  that shows a remaining portion of the target zone segmentation  124 . Shown within the panel  134  are a number of ablation zone selectors  144  that are volumes. These correspond to volumes that the operator can select to further ablate the target zone  124 . After an ablation zone selector  144  has been removed a variety of actions may take place. For example, this area may be removed from the target zone segmentation  124  to show a smaller volume or region that still needs to be ablated. It may also cause the insertion instructions  128  to be generated. In some examples this medical instrument  100  may be used purely for planning purposes. For example, the insertion instructions  128  could be followed at a later time. In other examples the medical instrument  100  could be integrated with an ablation probe and/or medical imaging system for tracking and real-time updating of the remaining portion  142 . 
     Also shown on the planning graphical user interface  112  is an optional automated planning request control  146 . For example, when this button  146  is activated by the operator the automated planning module  126  may for example choose one of the ablation zone selectors  144  automatically. 
       FIG.  2    illustrates a further example of a medical instrument  200 . The medical instrument  200  in  FIG.  2    is similar to the medical instrument  100  in  FIG.  1    except in this example instead of the ablation zone selector selecting volumes the ablation zone selector instead selects trajectories  144 ′. These for example may be a choice of different insertion points for an ablation probe. Once a trajectory  144 ′ is selected the ablation zone that will be ablated may be determined and this may be removed or subtracted from the remaining portion  142 . 
       FIG.  3    shows a flowchart which illustrates a method of operating the medical instrument  100  of  FIG.  1  or  200    of  FIG.  2   . First in step  300  the anatomical segmentation  122  identifying a location of an anatomical structure is received. Next in step  302  the target zone segmentation  124  is received and this identifies the location of a volume at least partially within the anatomical segmentation. Next in step  304  the planning graphical user interface  112  is displayed. The planning graphical user interface  112  comprises a first panel  130  that is configured for rendering a cross-sectional view of the anatomical segmentation  136  and a cross-sectional view of the target zone segmentation  138 . The planning graphical user interface  112  further comprises a second panel  132  that is configured for displaying a rendering of a first three-dimensional model  140  of the anatomical segmentation  122  and the target zone segmentation  124 . 
     The planning graphical user interface  112  further comprises a third panel  134  which is configured for rendering a second three-dimensional model  142  of a remaining portion of the target zone segmentation. The planning graphical user interface further comprises an ablation selector  144 ,  144 ′ configured for providing an ablation zone descriptive of a volume at least partially within the remaining portion. The method then proceeds to step  306 . In step  306  the ablation zone is received from the ablation zone selector  144 ,  144 ′. Then in step  308  the remaining portion  142  is updated by removing the ablation zone from the remaining portion. This causes the remaining portion to become smaller. The method then proceeds to decision box  310 . In this step it asks are the iterations finished. If the answer is no then the method returns back to step  306  and another ablation zone is selected. If the answer is yes then the method proceeds to step  312  and the method illustrated in  FIG.  3    ends. 
       FIG.  4    shows a further example of a medical instrument  400 . The medical instrument  400  in  FIG.  4    is similar to the medical instruments  100  and  200  depicted in  FIGS.  1  and  2   . The medical instrument  400  additionally comprises a guidance medical image system  402  and an ablation probe tracking system  412 . There is also an ablation probe system  406  displayed. The guidance medical image system  402  may represent any number of different modalities of medical imaging that may be used for tracking the insertion of the ablation probe  406 . The guidance medical imaging system  402  has an imaging zone  404  from which guidance medical image data  422  can be acquired. A subject  408  is shown as on a subject support  410  and is supported such that the anatomical structure  416  and the target zone  418  are within the imaging zone  404 . 
     The planning graphical user interface  112  is further shown as having a real-time rendering  424  of the guidance medical image data  422  acquired by the guidance medical imaging system  402 . It clearly displays the position of the ablation probe  406 . The medical instrument  400  is also shown as comprising an ablation probe tracking system  412 . This may for example comprise electronics which are able to localize the position and orientation of the ablation probe  406  so that is can be better determined what region of the subject  408  is actually ablated by the probe  406 . This can be used to update or correct the remaining portion  142 . 
       FIG.  5    illustrates a further example of a medical instrument  500 . The medical instrument  500  in  FIG.  5    is similar to the medical instruments  100  and  200  except that the medical instrument  500  further comprises a planning magnetic resonance imaging system  502 . The planning magnetic resonance imaging system  502  is a magnetic resonance imaging system. The term planning in the planning magnetic resonance imaging system is simply a label. Likewise, the planning label is used for pulse sequence commands, k-space data and images from this planning magnetic resonance imaging system  502 . The features of  FIG.  5    may be freely combined with the features of  FIG.  4   . In some instances, the planning magnetic resonance imaging system  502  may be identical with the guidance medical imaging system  402 . 
     The planning magnetic resonance imaging system  502  comprises a magnet  504 . The magnet  504  is a superconducting cylindrical type magnet with a bore  506  through it. The use of different types of magnets is also possible; for instance it is also possible to use both a split cylindrical magnet and a so called open magnet. A split cylindrical magnet is similar to a standard cylindrical magnet, except that the cryostat has been split into two sections to allow access to the iso-plane of the magnet, such magnets may for instance be used in conjunction with charged particle beam therapy. An open magnet has two magnet sections, one above the other with a space in-between that is large enough to receive a subject: the arrangement of the two sections area similar to that of a Helmholtz coil. Open magnets are popular, because the subject is less confined. Inside the cryostat of the cylindrical magnet there is a collection of superconducting coils. 
     Within the bore  506  of the cylindrical magnet  504  there is an imaging zone  508  where the magnetic field is strong and uniform enough to perform magnetic resonance imaging. A region of interest  509  is shown within the imaging zone  508 . The k-space data that is acquired typically acquired for the region of interest. The subject  408  is shown as being supported by a subject support  520  such that at least a portion of the subject  408  is within the imaging zone  508  and the region of interest  509 . The anatomical structure  416  and the target zone  418  are within the field of view  509  which is also inside of the imaging zone  508 . 
     Within the bore  506  of the magnet there is also a set of magnetic field gradient coils  510  which is used for acquisition of preliminary magnetic resonance data to spatially encode magnetic spins within the imaging zone  508  of the magnet  504 . The magnetic field gradient coils  510  connected to a magnetic field gradient coil power supply  512 . The magnetic field gradient coils  510  are intended to be representative. Typically magnetic field gradient coils  510  comprise three separate sets of coils for spatially encoding in three orthogonal spatial directions. A magnetic field gradient power supply supplies current to the magnetic field gradient coils. The current supplied to the magnetic field gradient coils  510  is controlled as a function of time and may be ramped or pulsed. 
     Adjacent to the imaging zone  508  is a radio-frequency coil  514  for manipulating the orientations of magnetic spins within the imaging zone  508  and for receiving radio transmissions from spins also within the imaging zone  508 . The radio frequency antenna may comprise multiple coil elements. The radio frequency antenna may also be referred to as a channel or antenna. The radio-frequency coil  514  is connected to a radio frequency transceiver  516 . The radio-frequency coil  514  and radio frequency transceiver  516  may be replaced by separate transmit and receive coils and a separate transmitter and receiver. It is understood that the radio-frequency coil  514  and the radio frequency transceiver  516  are representative. The radio-frequency coil  514  is intended to also represent a dedicated transmit antenna and a dedicated receive antenna. Likewise the transceiver  516  may also represent a separate transmitter and receivers. The radio-frequency coil  514  may also have multiple receive/transmit elements and the radio frequency transceiver  516  may have multiple receive/transmit channels. For example if a parallel imaging technique such as SENSE is performed, the radio-frequency could  514  will have multiple coil elements. 
     The transceiver  516  and the gradient controller  512  are shown as being connected to the hardware interface  104  of a computer system  102 . 
     The memory  110  is further shown as comprising planning pulse sequence commands  530 . The planning pulse sequence commands  530  are pulse sequence commands. The planning pulse sequence commands  530  are data or commands which may be converted into commands that control the planning magnetic resonance imaging system  502  to acquire the planning k-space data  532 . The planning k-space data  532  is k-space data. The memory  110  is further shown as comprising a planning magnetic resonance image  534 . The planning magnetic resonance image was reconstructed from the planning k-space data  532  and may be segmented. The memory  110  is further shown as comprising an automated segmentation algorithm  536  that is able to automatically generate the anatomical segmentation  122  and/or the target zone segmentation  124  using the planning magnetic resonance image  534  as input. In some cases, these segmentations may also be provided manually using the planning graphical user interface  112 . 
     In thermal tumor ablation procedures (and may other types of ablations), it is beneficial to fully cover the tumor to eradicate the disease, without ablating surrounding critical structures. For this purpose, it is possible to create a plan upfront, yet real-time feedback mechanisms while placing the ablation applicators and performing the ablation are missing. 
     Examples may provide a feedback mechanism to help clinicians in assessing coverage of the tumor, and especially in identifying areas that are not treated within the tumor. The system includes visualization of the untreated area in 2D and 3D including associated interaction mechanisms. 
     Examples may be particularly relevant to the field of thermal ablation in general, and specifically addresses the need to support identification of areas that are not treated. Although the disclosure below is also relevant to many other types of ablation. 
     Percutaneous thermal ablation is an interventional cancer treatment option that has seen significant increase in adoption in the past decade, and is predicted to continue to grow at a CAGR of 8-10% through 2024. Thermal ablation can be delivered using various ablation modalities, including radiofrequency (RF), microwave (MW), high-intensity focused ultrasound (HIFU), focal laser ablation (FLA), irreversible electroporation (IRE), cryo-ablation, etc. 
     In clinical practice, these ablation procedures consist of placing one or more ablation applicators (ablation probe  406 ) inside or near the target region (target zone  418 ) with the help of image guidance. Typically, physicians place these needle-like applicators while inspecting real-time ultrasound or interventional radiology images (CT/MR), based on information provided from the manufacturer, results in clinical trials and personal experience. The use of more advanced ablation therapy planning systems (ATPS) to plan the ablation and guide needle placement, akin to the radiation therapy planning systems (RTPS) used in brachytherapy procedures, is not wide spread due to their limited availability. 
     In current ablation procedures, quality assurance is limited. Most procedures are performed without a plan, and if a plan is defined, it is visualized by displaying the covered/treated area, without direct feedback on the presence of small untreated areas (“gaps”) between individual ablations inside the target. 
     Examples may provide for an ablation therapy guidance system, capable displaying the untreated area within the target (the remaining portion  142 ). This display (planning graphical user interface  112 ) is interactive, 3D rendering that allows the user to determine where to place additional applicators to cover the untreated areas. 
     Given discrete binary representations of a lesion L (target zone  418 ) to be treated and the ablation zone Z ( 600 ), the untreated area U (the remaining portion  142 ) can be computed by the following equation: 
         U=L\Z={x∈L|x∉Z}   (1)
 
     For the purpose of visualization, the binary region U may need to be converted in a mesh or contour structure. For this purpose, the calculation may include marching squares or marching cubes as a post-processing step. 
     The untreated area may be visualized in 2D, e.g. on top of multi-planar reformat (MPR) visualizations of 3D image volume covering the area to be treated, or on top of live US images that are registered to the applicator plan through real-time tracking. 
       FIGS.  6  and  7    below provide example of 2D untreated area visualizations.  FIG.  6    shows an example of a planning magnetic resonance image  534 . There is visible an anatomical segmentation  122  with a target zone segmentation  124  and an ablation zone  600 . 
       FIG.  7    shows the same segmentations  122 ,  124  and the location of the ablation zone  600  in an ultrasound image  700 . The location of a suggested position for the ablation probe  702  is also displayed. 
     The untreated area (the remaining portion  142 ) may be visualized in 3D, e.g. by shaded surface in combination with other anatomical parts to reveal the relative location of the untreated area with respect to surrounding tissue. 
       FIGS.  8  and  9    show two views of the third panel  134 . In  FIG.  8    the remaining portion  142  is the entire target zone segmentation  124 . An ablation zone  144  has been selected. After this is selected the volume of the ablation zone is removed from the remaining portion  142 .  FIG.  9    shows the remaining portion  142  after the ablation zone  144  has been removed. 
     In transperineal prostate procedures, the visualization may include a visualization of the transperineal grid template (a needle guidance device) through which applicators are being inserted. This enables the users to decide on the correct approach to cover the untreated area. 
       FIG.  10    shows an alternative means of visualization. Illustrated in  FIG.  10    is a rendering of a transperineal grid template that lays a matrix of circles labeled A-M and  1 - 13 . These represent different locations where an ablation probe may be inserted. Underneath this grid  1000  the ablation zone  600  is illustrated as well as the remaining portion  124 . Superimposing  600  in  124  on the grid  1000  may help an operator visualize the proper location to insert an ablation probe. 
     When including more regions for healthy tissue and organs at risk, these 3D surface renderings may possibly be generated with the help of advanced techniques, such as glass rendering. 
     When the untreated area is visualized in 3D renderings, alongside MPR visualizations of a 3D image volume of the area to be treated, the system may incorporate a navigation aid that positions the MPR viewers based on a clicked untreated area as visualized in a 3D rendering. 
     In some examples, when the untreated area is visualized, the user may be able to plan an ablation within the untreated area: 
     by clicking a location in the untreated area (in MPR view or 3D rendering), 
     by clicking a needle trajectory that passes through the untreated area (e.g. .clicking a grid hole in prostate procedures), and 
     by clicking a button to initiate automated planning. 
     The visualization of the untreated areas plays an important role during two decision moments in an ablation procedure that is guided by an ATPS. 
     The first moment is the review and approval of the plan that is to be implanted by the user. Before starting to do so, the user can inspect his plan to assess whether there are no remaining uncovered areas in the target lesion. 
     The second moment is after placement of the applicators, where small deviations from the plan are inevitable. Such deviations may introduce small untreated areas in between the applicators, which can now easily be visualized. If there are gaps, the user can decide to plan further ablations, to place an applicator in the untreated area, or to accept the gap as is. 
     Examples may possibly provide for medical instruments with one or more of the following features: 
     A medical instrument cable of computing and displaying the untreated area within a target for an ablation treatment. 
     A medical instrument capable of visualizing the untreated area relative to needle guidance device. 
     A medical instrument capable of calculating a new ablation plan that will cover the untreated area. 
     A medical instrument in which the display of the untreated area is achieved using 2D rendering techniques. 
     A medical instrument in which the display of the untreated area is achieved using 3D rendering techniques. 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. 
     Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems. Any reference signs in the claims should not be construed as limiting the scope. 
     LIST OF REFERENCE NUMERALS 
     
         
           100  medical instrument 
           102  computer 
           104  hardware interface 
           106  computational system 
           108  user interface 
           110  memory 
           112  planning graphical user interface 
           120  machine executable instructions 
           122  anatomical segmentation 
           124  target zone segmentation 
           126  automated planning module 
           128  insertion instructions 
           130  first panel 
           132  second panel 
           134  third panel 
           136  cross sectional view of anatomical segmentation 
           138  cross sectional view of target zone segmentation 
           140  first three-dimensional model 
           142  second three-dimensional model of the remaining portion 
           144  ablation zone selector (volume selector) 
           144 ′ ablation zone selector (trajectory selector) 
           146  automated planning request control 
           148  display for insertion instructions 
           200  medical instrument 
           300  receive an anatomical segmentation identifying a location of an anatomical structure 
           302  receive a target zone segmentation identifying a location of a volume at least partially within the anatomical segmentation 
           304  display a planning graphical user interface using the display 
           306  receive the ablation zone from the ablation selector 
           308  update the remaining portion by removing the ablation zone from the remaining portion 
           310  Iterations finished? 
           312  end 
           400  medical instrument 
           402  guidance medical imaging system 
           404  imaging zone 
           406  ablation probe system 
           408  subject 
           410  support 
           412  ablation probe tracking system 
           416  anatomical structure 
           418  target zone 
           420  probe tracking data 
           422  guidance medical image data 
           424  real time rendering of guidance medical image data 
           500  medical instrument 
           502  planning magnetic resonance imaging system 
           504  magnet 
           506  bore of magnet 
           508  imaging zone 
           509  region of interest 
           510  magnetic field gradient coils 
           512  magnetic field gradient coil power supply 
           514  radio-frequency coil 
           516  transceiver 
           520  subject support 
           530  planning pulse sequence commands 
           532  planning k-space data 
           534  planning magnetic resonance image 
           536  automated segmentation algorithm 
           600  ablation zone 
           700  ultrasound image 
           702  location of ablation probe 
           1000  transperineal grid template