Method for registering three-dimensional representations of an object on the object itself and device for providing navigation assistance in an object implementing said method

Abstract

The invention relates to a registration method comprising: a step of recording (100, 102, 114, 116) two three-dimensional representations of an object (12) and the locations of at least three reference points (Pr) of the object in said two three-dimensional representations; a step of angularly registering the first three-dimensional representation on the object on the basis of a step of recording (104) the locations of the reference points on the object in a reference frame linked to a referencing accessory (24) attached to the object; a step of performing the surface registration (106, 108, 110) of the first three-dimensional representation on the object comprising a step of recording (108) the locations of the surface points (Ps) in addition to the reference points on the surface of the object in the three-dimensional reference frame linked to the referencing accessory; and a step of registering the second three-dimensional representation of the object on the object itself comprising a step of performing the surface registration (120) of said second three-dimensional representation on the basis of the step of recording (108) the locations of the reference points produced for performing the surface registration of the first three-dimensional representation.

Description

Method for realigning three-dimensional representations of an object on the object itself and device for assisting navigation in an object implementing this method

[0001] The present invention relates to a method for three-dimensional registration of three-dimensional representations of an object on the object itself, using a referencing ancillary fixed on the object and a stylus whose tip is locatable in a three-dimensional reference frame linked to the referencing ancillary. It also relates to a computer program comprising instructions for executing the steps of such a method, as well as a device for assisting navigation in an object implementing this registration method.

[0002] The invention applies more particularly to a method of this type comprising: a recording in memory of a first three-dimensional representation of the object according to a first three-dimensional imaging mode and locations of at least three reference points of the object in this first three-dimensional representation; an angular three-dimensional resetting, by a calculation unit, of this first three-dimensional representation on the object from a recording, using the tip of the stylus, of locations of the reference points of the object in the three-dimensional reference frame linked to the referencing ancillary;a three-dimensional surface registration, by the calculation unit, of this first three-dimensional representation on the object comprising: an extraction of a surface of the object in the first three-dimensional representation, a recording, using the tip of the stylus, of locations of a plurality of surface points other than the reference points on the surface of the object in the three-dimensional reference frame linked to the referencing ancillary, and the calculation of the three-dimensional surface registration from this recording of locations of surface points.;

[0003] Such a three-dimensional registration method is for example implemented in a device for assisting navigation in an object using an instrument with a functional end such as the surgical navigation device marketed under the registered trademark “Collin Navigation Solutions” and intended for otorhinolaryngology interventions. The object is then the head of a human or animal patient inside which an intervention, using a surgical instrument, must be envisaged by the auditory, nasal or oral route. This is a non-limiting example of an industrial application of the present invention.

[0004] More precisely, the three-dimensional angular registration carried out by recording the locations of the reference points chosen by a practitioner both in the first three-dimensional representation of the object and on the object itself makes it possible to facilitate, by simplifying it, the calculation of a transition matrix between the reference frame linked to the object, that is to say the one linked to the referencing ancillary, and a reference frame linked to the first three-dimensional representation. This simplification results from a limitation of the possible solutions in the well-known algorithmic resolution of the calculation of the transition matrix.

[0005] Furthermore, provision may be made for: a recording in memory of a second three-dimensional representation of the object according to a second three-dimensional imaging mode, other than the first three-dimensional imaging mode, and of locations of the reference points of the object in this second three-dimensional representation; and a three-dimensional registration of this second three-dimensional representation of the object on the object itself.

[0006] More generally, it is possible to provide for the three-dimensional recording and registration of more than two three-dimensional representations. However, each three-dimensional registration, even simplified by taking locations of landmarks, remains algorithmically complex and therefore costly in terms of computation time. Multiplying the three-dimensional representations that can be recorded, registered and displayed for a navigation aid device in an object is therefore certainly very interesting from the point of view of a multimodal approach to intervention in the object, but it has certain limitations.

[0007] Another solution could be to re-align the first three-dimensional representation on the object, then to re-align, in particular to merge, each other three-dimensional representation on the first. But in reality it is not simpler. Moreover, the methods of registration by fusion of data known in medical imaging, between CT and magnetic resonance imaging in particular, are not satisfactory for an application in otorhinolaryngology which takes advantage of separate displays of the different acquisition modes.

[0008] It may therefore be desirable to provide a three-dimensional recalibration process which makes it possible to overcome at least some of the aforementioned problems and constraints.

[0009] A method is therefore proposed for three-dimensional registration of three-dimensional representations of an object on the object itself, using a referencing ancillary fixed on the object and a stylus whose tip can be located in a three-dimensional reference frame linked to the referencing ancillary, comprising: a recording in memory of a first three-dimensional representation of the object according to a first three-dimensional imaging mode and locations of at least three reference points of the object in this first three-dimensional representation; an angular three-dimensional registration, by a calculation unit, of this first three-dimensional representation on the object from a recording, using the tip of the stylus, of locations of the reference points of the object in the three-dimensional reference frame linked to the referencing ancillary;a three-dimensional surface registration, by the calculation unit, of this first three-dimensional representation on the object comprising: an extraction of a surface of the object in the first three-dimensional representation, a recording, using the tip of the stylus, of locations of a plurality of surface points other than the reference points on the surface of the object in the three-dimensional reference system linked to the referencing ancillary, and the calculation of the three-dimensional surface registration from this recording of locations of surface points; a recording in memory of a second three-dimensional representation of the object according to a second three-dimensional imaging mode, other than the first three-dimensional imaging mode, and of locations of the reference points of the object in this second three-dimensional representation;anda three-dimensional registration of this second three-dimensional representation of the object on the object itself; in which the three-dimensional registration of the second three-dimensional representation comprises a three-dimensional surface registration of this second three-dimensional representation, by the calculation unit, from the recording of the locations of surface points carried out for the surface registration of the first three-dimensional representation.;

[0010] Taking advantage of the recording of the locations of surface points carried out for the surface registration of the first three-dimensional representation, to carry out the three-dimensional surface registration of the second three-dimensional representation, is a trick which simplifies the three-dimensional registration of any three-dimensional representation recordable from the second, since the same process can be applied to a third three-dimensional representation replacing the second, etc. This also makes it possible to increase the number of surface points to be located by stylus to improve the quality of each three-dimensional surface registration, without increasing the complexity and duration of the registration protocol.

[0011] Optionally, the three-dimensional registration of the second three-dimensional representation comprises an angular three-dimensional registration, by the calculation unit, of this second three-dimensional representation on the object from the recording, carried out for the angular three-dimensional registration of the first three-dimensional representation, of the locations of the reference points of the surface of the object in the three-dimensional reference frame linked to the referencing ancillary.

[0012] Also optionally: the three-dimensional surface registration of the first three-dimensional representation on the object comprises the calculation of a first transition matrix between the locations of the recorded surface points and their locations on the surface of the object as extracted in the first three-dimensional representation; and the three-dimensional surface registration of the second three-dimensional representation comprises an extraction of a surface of the object in the second three-dimensional representation and the calculation of a second transition matrix between the locations of the recorded surface points for the surface registration of the first three-dimensional representation and their locations on the surface of the object as extracted in the second three-dimensional representation.

[0013] Also optionally, the three-dimensional surface registration of the first three-dimensional representation on the object comprises the recording of the locations of several hundred surface points other than the reference points on the surface of the object in the three-dimensional reference system linked to the referencing ancillary, preferably between 200 and 1000 surface points, more preferably between 500 and 600 surface points.

[0014] Also optionally, a three-dimensional registration method according to the invention comprises the prior acquisition: of the first three-dimensional representation in the form of a volume image of the object by scanner or computed tomography; and of the second three-dimensional representation in the form of a volume image of the object by magnetic resonance.

[0015] Also optionally, the object is a human or animal patient's head and the referencing ancillary is a device fixed to this head with a stability capable of inducing a submillimetric registration error, for example a forehead band fixed in a stable manner on the patient's forehead, a forehead pad fixed in a stable manner on the patient's forehead or an oral device clamped in the patient's mouth between his teeth.

[0016] Optionally also, the patient's head reference points are non-aligned, for example comprising at least one nasion location point, one nasolabial junction location point and one external orbital rim location point when the referencing ancillary is stably fixed to the patient's forehead.

[0017] There is also provided a computer program downloadable from a communication network and / or recorded on a computer-readable medium and / or executable by a processor, comprising instructions for executing the steps of a method for three-dimensional registration of three-dimensional representations of an object on the object itself according to the invention, when said program is executed by a computing unit of a device for assisting navigation in the object using an instrument with a functional end, and when this device further comprises: a memory for storing a first three-dimensional representation of the object according to a first three-dimensional imaging mode, locations of at least three reference points of the object in this first three-dimensional representation,of a second three-dimensional representation of the object according to a second three-dimensional imaging mode other than the first three-dimensional imaging mode, and of locations of the reference points of the object in this second three-dimensional representation; a referencing ancillary intended to be fixed on the object; and a stylus, manipulable by an operator, a tip of which is localizable in a three-dimensional reference frame linked to the referencing ancillary.,

[0018] There is also provided a device for assisting navigation in an object using an instrument with a functional end, comprising: a memory for storing a first three-dimensional representation of the object according to a first three-dimensional imaging mode, locations of at least three reference points of the object in this first three-dimensional representation, a second three-dimensional representation of the object according to a second three-dimensional imaging mode other than the first three-dimensional imaging mode, and locations of the reference points of the object in this second three-dimensional representation; a computing unit designed for three-dimensional registration of said first and second three-dimensional representations of the object on the object itself; a referencing ancillary intended to be fixed on the object;a stylus having a tip that can be located in a three-dimensional reference frame linked to the referencing ancillary; in which the calculation unit is more precisely designed to perform: a three-dimensional angular recalibration of the first three-dimensional representation on the object from a recording, by interaction with the tip of the stylus when it is manipulated by an operator, of the locations of the reference points of the object in the three-dimensional reference frame linked to the referencing ancillary;a three-dimensional surface registration of the first three-dimensional representation on the object comprising:an extraction of a surface of the object in the first three-dimensional representation,a recording, by interaction with the tip of the stylus when it is manipulated by an operator, of locations of a plurality of surface points other than the reference points on the surface of the object in the three-dimensional reference system linked to the referencing ancillary, andthe calculation of the three-dimensional surface registration from this recording of locations of surface points;the calculation unit being further designed so that the three-dimensional registration of the second three-dimensional representation comprises a three-dimensional surface registration of this second three-dimensional representation from the recording of the locations of surface points carried out for the surface registration of the first three-dimensional representation.;

[0019] Optionally, a device for assisting navigation in an object according to the invention may further comprise:an instrument, one functional end of which can be located in the three-dimensional reference system linked to the referencing ancillary; anda screen for simultaneously displaying several planar sectional reconstructions of the object, including at least two planar reconstructions of the same section of the object obtained respectively from one and the other of the first and second three-dimensional representations;in which the calculation unit is designed to:locate and visually display the functional end of the instrument in each planar sectional reconstruction of the object displayed by the screen;andswitching the display between several planar sectional reconstructions of the object according to the first three-dimensional representation, several planar sectional reconstructions of the object according to the second three-dimensional representation and several planar sectional reconstructions of the object according to the first and second three-dimensional representations, this switching being activatable by a predetermined approximation between the functional end of the instrument and a calibration plot of the referencing ancillary.;

[0020] The invention will be better understood with the aid of the following description, given solely by way of example and with reference to the appended drawings in which: diagrammatically represents the general structure of a device for assisting navigation in an object, according to one embodiment of the invention, illustrates an example of simultaneous display of several planar reconstructions in section of the object of the obtained from two different three-dimensional representations, such as can be obtained on a screen of the navigation aid device of the. illustrates the successive steps of a method for three-dimensional recalibration of three-dimensional representations of the object of the on itself, such as can be implemented by the navigation aid device of the.

[0021] The device 10 for assisting navigation in an object 12 shown schematically in the comprises a movable navigation unit 14 comprising a main box 16 with electrical, electronic and software components, for example mounted on casters and provided with a grip handle (not shown) to be moved by a practitioner, and a display screen 18, for example a touch screen, secured to the main box 16. In the non-limiting example shown in the, it is more precisely a surgical navigation device intended for interventions in otorhinolaryngology (ENT). The object 12 is then the head of a human or animal patient inside which an intervention must be envisaged by auditory, nasal or oral route.

[0022] To do this, the navigation aid device 10 further comprises an instrument 20 with a functional end 22, such as an ENT surgical instrument with a suction cannula, rotating tip, forceps, or any other functional end 22 useful for an ENT surgical intervention via the auditory, nasal or oral route.

[0023] For the implementation of a method of three-dimensional registration of three-dimensional representations of the object 12 on the object 12 itself, as well as a method of navigation assisted by tracking, on the display screen 18, a movement of the functional end 22 of the surgical instrument 20 in interior cavities of the head 12 of the patient, the navigation aid device 10 further comprises: a referencing ancillary 24 with an active electromagnetic location element 26 (i.e. an electromagnetic sensor with an emitting function), intended to be fixed in a manner known per se on the head 12 of the patient, and a registration stylet 28 of which a distal tip 30 is locatable in a three-dimensional reference frame linked to the referencing ancillary 24, this reference frame therefore also being linked to the head 12 of the patient when the referencing ancillary 24 is fixed thereto.

[0024] The methods of fixing the referencing ancillary 24 on the head 12 are known per se and will not be detailed. They are for example advantageously defined so as to ensure stability of the fixing capable of inducing a resetting error, and therefore a submillimetric navigation tracking error.

[0025] The illustration shows a referencing ancillary 24 in the form of a forehead pad fixed in a stable manner by double-sided adhesive tape on the patient's forehead, but any other well-known referencing ancillary is also suitable: for example a forehead band fixed in a stable manner on the patient's forehead, an oral device clamped in the patient's mouth between his teeth, a bone device screwed laterally into the patient's skull, or any other form of referencing ancillary suitable for an ENT surgical procedure.

[0026] It will be noted that the way in which the distal tip 30 of the resetting stylet 28 can be located in the three-dimensional reference frame linked to the referencing ancillary 24 (using an electromagnetic sensor with a reception function for example) is well known, so that the electromagnetic technology implemented for such localization will not be detailed. And it is according to this same technology that the surgical instrument 20 can also be located in the three-dimensional reference frame linked to the referencing ancillary 24 (also using an electromagnetic sensor with a reception function for example). More precisely, so that it is its functional end 22, potentially interchangeable, which is itself directly localizable in the three-dimensional reference frame linked to the referencing ancillary 24, a calibration of the surgical instrument 20 may be necessary.This calibration, carried out using a calibration plot 31 attached to the referencing ancillary 24, or using the recalibration stylus 28, is also well known, so it will not be detailed either.

[0027] It will also be noted that during an intervention implementing the three-dimensional registration of three-dimensional representations of the object 12 on the object 12 itself, the calibration of the surgical instrument 20 or the aforementioned assisted navigation, it is appropriate to isolate the head 12 of the patient on which the referencing ancillary 24, the registration stylet 28 and the surgical instrument 20 are fixed from any disturbance, in particular from any disturbance due to too great proximity of the movable navigation unit 14. This is the reason why the operating field Z1 in which the head 12 of the patient, the referencing ancillary 24, the registration stylet 28 and the surgical instrument 20 are located is distant and well isolated from the navigation aid field Z2 in which the movable navigation unit 14 is located. This distance, or this isolation, is marked in draw the horizontal line T in broken lines.

[0028] To interact with the referencing ancillary 24, the resetting stylet 28 and the surgical instrument 20, the main box 16 is provided with a spatial localization interface 32 with electromagnetic field creation. This is an electronic element making it possible to determine the three-dimensional spatial coordinates of a specific sensor, such as those embedded in the referencing ancillary 24, the resetting stylet 28 and the surgical instrument 20. Such a spatial localization interface 32 is well known, so it will not be detailed.

[0029] The main box 16 is further provided with an interface 34 for connection to other possible peripherals: in particular a keyboard 36, a mouse 38 and / or a remote control 40. The remote control 40 is for example connected by an infrared type IR wireless link, which allows it to be used in the operating field Z1. The interface 34 may further comprise a USB port, a CD-ROM reader, or any other video input making it possible to record a three-dimensional representation of the object 12 previously acquired according to any three-dimensional imaging mode.

[0030] The main box 16 further comprises several functional modules which will be described below. In the example described, these modules are of a software nature. Thus, the main box 16 comprises a computer-type element 42 comprising a processing unit 44, interacting with the spatial location interface 32, the interface 34 and the display screen 18, and an associated memory area 46 in which a data storage area 48 and several computer programs 50 to 60 or several functions of the same computer program are recorded. These computer programs comprise instructions designed to be executed by the processing unit 44 in order to carry out the functions of the software modules. They are presented as distinct, but this distinction is purely functional. They could just as well be grouped according to all possible combinations into one or more software programs.Their functions could also be at least partly microprogrammed or microwired in dedicated integrated circuits, such as digital circuits. Thus, alternatively, the computer 42 could be replaced by an electronic device composed solely of digital circuits (without a computer program) for the realization of the same functions.

[0031] The main box 16 thus firstly comprises a software module 50, intended to be executed by the processing unit 44, for recording in memory 46, more precisely in the data storage area 48, three-dimensional representations of the object 12, otherwise generally called “series”, according to any three-dimensional imaging modes, preferably according to one or more imaging modes by scanner (i.e. by computed tomography) or MRI (i.e. for “Magnetic Resonance Imaging”) with or without injection of contrast product(s). Generally speaking, any three-dimensional imaging mode allowing extraction of a surface of the object 12 is suitable, knowing that the series obtained by scanner are mainly used in ENT surgery. A limit may be set in terms of the number of series that can be recorded in the data storage area 48, for example four.

[0032] The main box 16 further comprises a software module 52, intended to be executed by the processing unit 44, for three-dimensional angular recalibration of each three-dimensional representation of the object 12 recorded in the data storage area 48 on the object 12 itself.

[0033] According to an example of an angular recalibration protocol advantageously implemented but not limiting, in particular if it is a question of angularly recalibrating a first three-dimensional representation, it is a question of locating at least three predetermined reference points of the object 12 in the three-dimensional representation concerned and recording them in the data storage area 48, then locating these same reference points in the three-dimensional reference system linked to the referencing ancillary 24 using the tip 30 of the stylus 28 in a manner known per se and also recording them in the data storage area 48.If it is a question of angularly realigning a second or subsequent three-dimensional representation, while the first three-dimensional representation has already been angularly realigned, it is sufficient to locate the reference points of the object 12 in the three-dimensional representation concerned and to record them in the data storage area 48 without needing to locate these same reference points again in the three-dimensional reference system linked to the referencing ancillary 24 using the stylus 28, since the angular realignment can advantageously take advantage of the locations recorded using the stylus 28 for the first three-dimensional representation given that they have no reason a priori to be different.

[0034] Reference points should be chosen that are as unaligned as possible to make the angular resetting effective and precise. For example, when the referencing ancillary 24 is a band or a pad fixed in a stable manner on the patient's forehead, the reference points generally chosen are a nasion location point, a nasolabial junction location point and a left and / or right external orbital rim location point. They conventionally indicate the main north, south and west and / or east orientations. Any other reference point can be freely chosen depending on the location where the referencing ancillary 24 is fixed, the intended application, and even more generally the nature of the object 12.

[0035] The main box 16 further comprises a software module 54, intended to be executed by the processing unit 44, for three-dimensional surface registration of each three-dimensional representation of the object 12 recorded in the data storage area 48 on the object 12 itself.

[0036] According to an example of a surface registration protocol advantageously implemented but not limiting, if it is a question of registering a first three-dimensional representation, it is first of all a question of extracting a surface of the object 12 in the three-dimensional representation concerned and of recording it in the data storage area 48. This can generally be done automatically if good known conditions of acquisition of this three-dimensional representation have been respected. It is also a question of locating a plurality of surface points other than the reference points on the surface of the object 12 in the three-dimensional reference system linked to the referencing ancillary 24 using the tip 30 of the stylus 28 and of recording them in the data storage area 48. It is finally a question of calculating the three-dimensional surface registration from this recording of locations of surface points.

[0037] More specifically, the three-dimensional surface registration of the first three-dimensional representation on the object 12 comprises the calculation of a first transition matrix between the locations of the surface points recorded previously and their locations on the surface of the object 12 as extracted in the first three-dimensional representation. The prior angular registration makes it possible to facilitate the calculation of this first transition matrix by limiting the possible solutions.

[0038] If it is a question of registering a second or subsequent three-dimensional representation, while the first three-dimensional representation has already been registered according to the aforementioned surface registration protocol, it is sufficient to extract a surface of the object 12 in the three-dimensional representation concerned and to record it in the data storage area 48, then to directly carry out a three-dimensional surface registration of this second or subsequent three-dimensional representation from the recording of the locations of surface points carried out for the surface registration of the first three-dimensional representation. This way of proceeding is very advantageous because the recording of the locations of surface points can be tedious and time-consuming.

[0039] More specifically, the three-dimensional surface registration of the second or subsequent three-dimensional representation on the object 12 comprises the calculation of a second transition matrix between the locations of the surface points previously recorded for the surface registration of the first three-dimensional representation and their locations on the surface of the object 12 as extracted in the second or subsequent three-dimensional representation. Similarly, the prior angular registration of the second or subsequent three-dimensional representation makes it possible to facilitate the calculation of this second transition matrix by limiting the possible solutions.

[0040] Concretely, many surface points can be located using the tip 30 of the stylet 28 by moving it over the patient's head 12, in particular all around the reference points. There is no real limit. For example, several hundred surface points are advantageously located in the three-dimensional reference system linked to the referencing ancillary 24 for the most precise surface registration possible in ENT surgery, preferably between 200 and 1000 surface points, more preferably between 500 and 600 surface points.

[0041] The main box 16 further comprises a software module 56, intended to be executed by the processing unit 44, for selecting a display to assist navigation carried out using the surgical instrument 20 when each three-dimensional representation recorded in the data storage area 48 has been realigned by executing the software modules 52 and 54. In particular when two realigned three-dimensional representations are available in memory 46, for example one in the form of a volume image of the object 12 by scanner, the other in the form of a volume image of the object 12 by magnetic resonance, the software module 56 manages the possible selection of a simultaneous display of several planar reconstructions in section of the object 12, including at least two planar reconstructions of the same section of the object 12 obtained respectively from one and the other of the first and second three-dimensional representations.

[0042] In ENT surgery, the planar sectional reconstructions of the object 12 generally relate to sagittal, axial and coronal sections. They are obtained by a calculation known per se, in particular by interpolation, from real sections acquired according to the imaging mode considered. In the example illustrated on the display screen 18 of the, an upper left window illustrates a menu allowing to select for example a display mode from several predetermined ones, to carry out the calibration of the surgical instrument 20 or to review the registration and the reference points of the three-dimensional representations available. A lower left window illustrates a real-time video tracking by endoscopic camera of the surgical instrument 20 in operating mode. A central upper window illustrates a coronal planar reconstruction by scanner including a positioning of the functional end 22 of the surgical instrument 20.An upper right window illustrates the same coronal planar reconstruction by MRI including a positioning of the functional end 22 of the surgical instrument 20. A lower central window illustrates an axial planar reconstruction by scanner including a positioning of the functional end 22 of the surgical instrument 20. A lower right window illustrates the same axial planar reconstruction by MRI including a positioning of the functional end 22 of the surgical instrument 20. This makes it possible to assess the position of the functional end 22 of the surgical instrument 20 on both scanner and MRI imaging modes at the same time.

[0043] The main box 16 further comprises a software module 58, intended to be executed by the processing unit 44, for tracking by real-time location of the functional end 22 of the surgical instrument 20 and for updating at each instant each of the planar reconstructions displayed simultaneously on the screen 18 which comprise it.

[0044] The main box 16 further comprises a software module 60, intended to be executed by the processing unit 44, for switching the display on the screen 18 between several planar sectional reconstructions of the object 12 according to the first three-dimensional CT representation, several planar sectional reconstructions of the object 12 according to the second three-dimensional MRI representation and several planar sectional reconstructions of the object 12 according to the first and second three-dimensional CT and MRI representations, this switching being in particular activatable by a predetermined approximation between the functional end 22 of the surgical instrument 20 and a specific receiver of the referencing ancillary 24, for example its calibration pad 31.This predetermined approximation assumes the prior calibration of the surgical instrument 20 as mentioned previously, to make its functional end 22 locatable relative to the calibration pad 31. Advantageously, the predetermined approximation is defined in terms of maximum distance and minimum duration. In other words, the predetermined approximation is a distance less than or equal to Dmax between the functional end 22 of the surgical instrument 20 and the calibration pad 31 for at least a duration Tmin. Concretely, Dmax is for example equal to 5 mm and Tmin equal to 2 s. These values ​​are those which from experience seem to work best to avoid an inopportune change of display by unintentionally bringing the functional end 22 closer to the calibration pad 31 during manipulation.Concretely also, Dmax and Tmin can be adjustable, for example in predefined ranges such as [2 mm; 8 mm] for Dmax and [1 s; 5 s] for Tmin. Of course, the predetermined approach designed to activate the display switching requires a particular gesture, that of correctly positioning the functional end 22 of the surgical instrument 20 at less than Dmax from the calibration pin 31 for at least Tmin, but this gesture once known is simple and intuitive to carry out.

[0045] This switching can also be activated by direct interaction with the display screen 18 when it is touch-sensitive. But this interaction is less simple and intuitive than the particular gesture mentioned above.

[0046] Each window displayed on the screen 18 and presenting a planar reconstruction in sagittal, axial or coronal section of the object 12 can furthermore possibly be switched individually, for example by tactile interaction or other means, to change section and / or imaging mode.

[0047] The software modules 56, 58 and 60 are executable independently by the processing unit 44, not necessarily in the order of their presentation above. They can also be executed at the same time.

[0048] Illustrates another non-limiting example of simultaneous display of several planar reconstructions in section of the object 12 according to the first and second three-dimensional CT and MRI representations mentioned above. The display is here subdivided into six windows. The three upper windows are respectively planar reconstructions in sagittal, coronal and axial sections of CT mode, while the three lower windows are respectively the same planar reconstructions in sagittal, coronal and axial sections of MRI mode. In each window, the functional end 22 of the surgical instrument 20 is precisely located at the intersection of two axes, one horizontal and the other vertical. The fact of visualizing and following the functional end 22 simultaneously in the three sagittal, coronal and axial sections and in the two CT and MRI imaging modes is a valuable aid for the practitioner.

[0049] The method of three-dimensional recalibration of three-dimensional representations of the object 12 on the object 12 itself as it can be implemented by the navigation aid device of the, corresponding to the execution of the software modules 50, 52 and 54, will now be detailed in accordance with the succession of steps of the.

[0050] During a step 100 carried out by executing the software module 50, a first three-dimensional representation of the object 12 according to a first three-dimensional imaging mode, for example one according to a scanner acquisition mode, is recorded in the data storage area 48.

[0051] During a following step 102 carried out by executing the software module 52, at least three predetermined reference points Pr of the object 12 are located in the first three-dimensional representation and recorded in the data storage area 48. In the example of 1a, four reference points Pr are predetermined and located: a nasion location point, a nasolabial junction location point, a left external orbital rim location point and a right external orbital rim location point.

[0052] During a following step 104 carried out by executing the software module 52, these same reference points Pr are located in the three-dimensional reference system linked to the referencing ancillary 24 using the tip 30 of the stylus 28 in a manner known per se and they are also recorded in the data storage area 48.

[0053] During a following step 106 carried out by executing the software module 54, a surface of the object 12 is extracted in the first three-dimensional representation and is recorded in the data storage area 48.

[0054] During a following step 108 carried out by executing the software module 54, several surface points Ps other than the reference points Pr are located on the surface of the object 12 in the three-dimensional reference system linked to the referencing ancillary 24 using the tip 30 of the stylus 28 and are recorded in the data storage area 48.

[0055] During a following step 110 carried out by executing the software module 54, the three-dimensional surface registration of the first three-dimensional representation is calculated from this recording of locations of surface points Ps. The calculation of the first passage matrix that it involves is facilitated by the prior angular registration carried out by executing steps 102 and 104.

[0056] During a following step 112, the registration obtained from the first three-dimensional representation of the object 12 on the object 12 itself can be validated using the stylus 28 according to a protocol known per se, so that this step will not be detailed.

[0057] During a following step 114 carried out by executing the software module 50, a second three-dimensional representation of the object 12 according to a second three-dimensional imaging mode, for example according to an MRI acquisition mode, is recorded in the data storage area 48.

[0058] During a following step 116 carried out by executing the software module 52, the predetermined reference points Pr of the object 12 are located in the second three-dimensional representation and recorded in the data storage area 48.

[0059] During a following step 118 carried out by executing the software module 54, a surface of the object 12 is extracted in the second three-dimensional representation and is recorded in the data storage area 48.

[0060] During a following step 120 carried out by executing the software module 54, the three-dimensional surface registration of the second three-dimensional representation is calculated from the recording of the locations of the surface points Ps carried out in step 108. The calculation of the second passage matrix that it involves is facilitated by the prior angular registration carried out by executing steps 116 and 104.

[0061] Finally, during a following step 122, the registration obtained from the second three-dimensional representation of the object 12 on the object 12 itself can also be validated using the stylus 28 according to a protocol identical to that of step 112.

[0062] It is clear that a method of three-dimensional registration of three-dimensional representations of an object on the object itself such as that described above makes it possible to envisage a simultaneous display of several different three-dimensional representations of this object by facilitating and accelerating the registration. This simultaneous display in several planar reconstructions in sections of the object according to different acquisition modes, advantageously scanner and MRI but not only, is a powerful tool to aid navigation in the object for an application in ENT surgery.

[0063] It should also be noted that the invention is not limited to the embodiment described above. It will indeed appear to those skilled in the art that various modifications can be made to the embodiment described above, in light of the teaching which has just been disclosed to them. In the detailed presentation of the invention which is given above, the terms used should not be interpreted as limiting the invention to the embodiment set out in the present description, but should be interpreted to include all equivalents which can be foreseen by those skilled in the art by applying their general knowledge to the implementation of the teaching which has just been disclosed to them.

Claims

Method for three-dimensional registration of three-dimensional representations of an object (12) on the object (12) itself, using a referencing ancillary (24) fixed on the object (12), a stylus (28) of which a tip (30) is locatable in a three-dimensional reference frame linked to the referencing ancillary (24) and an instrument (20) of which a functional end (22) is locatable in the three-dimensional reference frame linked to the referencing ancillary (24), comprising: a recording (100, 102) in memory of a first three-dimensional representation of the object (12) according to a first three-dimensional imaging mode and of localizations of at least three reference points (Pr) of the object (12) in this first three-dimensional representation;a three-dimensional angular registration (102, 104), by a computing unit (44), of this first three-dimensional representation on the object (12) from a recording (104), using the tip (30) of the stylus (28), of the locations of the reference points (Pr) of the object (12) in the three-dimensional frame linked to the referencing ancillary (24); a three-dimensional surface registration (106, 108, 110), by the computing unit (44), of this first three-dimensional representation on the object (12) comprising: an extraction (106) of a surface of the object (12) in the first three-dimensional representation, a recording (108) of the locations of a plurality of surface points (Ps) other than the reference points (Pr) on the surface of the object (12) in the three-dimensional frame linked to the referencing ancillary of referencing (24), and the calculation (110) of the three-dimensional surface registration from this recording (108) of surface point locations;a recording (114, 116) in memory of a second three-dimensional representation of the object (12) according to a second three-dimensional imaging mode, other than the first three-dimensional imaging mode, and of locations of the reference points (Pr) of the object (12) in this second three-dimensional representation; a three-dimensional registration (116, 118, 120) of this second three-dimensional representation of the object (12) on the object (12) itself; and a simultaneous display of several planar reconstructions in section of the object (12); the three-dimensional registration (116, 118, 120) of the second three-dimensional representation comprising a three-dimensional surface registration (118, 120) of this second three-dimensional representation, by the calculation unit (44), from the recording (108) of the locations of surface points (Ps) made for the surface registration (110) of the first three-dimensional representation;characterized in that the recording of the locations of the plurality of surface points (Ps) other than the reference points (Pr) on the surface of the object (12) in the three-dimensional reference frame linked to the referencing tool (24) is done using the tip (30) of the stylus (28); and in that the display is switchable between several planar cross-sectional reconstructions of the object (12) according to the first three-dimensional representation, several planar cross-sectional reconstructions of the object (12) according to the second three-dimensional representation and several planar cross-sectional reconstructions of the object (12) according to the first and second three-dimensional representations, this switching being activable by a predetermined proximity between the functional end (22) of the instrument (20) and a calibration pad (31) of the referencing tool (24). Three-dimensional registration method according to claim 1, wherein the three-dimensional registration (116, 118, 120) of the second three-dimensional representation includes an angular three-dimensional registration (116, 104), by the calculation unit (44), of this second three-dimensional representation on the object (12) from the recording (104), made for the angular three-dimensional registration (102, 104) of the first three-dimensional representation, of the locations of the reference points (Pr) of the surface of the object (12) in the three-dimensional reference frame linked to the referencing ancillary (24). Three-dimensional registration method according to claim 1 or 2, wherein: the three-dimensional surface registration (106, 108, 110) of the first three-dimensional representation on the object (12) includes the calculation (110) of a first transition matrix between the locations of the recorded surface points (Ps) and their locations on the surface of the object (12) as extracted (106) in the first three-dimensional representation;and the three-dimensional surface registration (118, 120) of the second three-dimensional representation includes an extraction (118) of a surface of the object (12) in the second three-dimensional representation and the calculation (120) of a second transition matrix between the locations of the surface points (Ps) recorded (108) for the surface registration (106, 108, 110) of the first three-dimensional representation and their locations on the surface of the object (12) as extracted (118) in the second three-dimensional representation.; A three-dimensional registration method according to any one of claims 1 to 3, wherein the three-dimensional surface registration (106, 108, 110) of the first three-dimensional representation on the object (12) comprises the recording (108) of the locations of several hundred surface points (Ps) other than the reference points (Pr) on the surface of the object (12) in the three-dimensional reference frame linked to the referencing ancillary (24), preferably between 200 and 1000 surface points, preferably even more between 500 and 600 surface points. A three-dimensional registration method according to any one of claims 1 to 4, comprising the prior acquisition of: the first three-dimensional representation in the form of a volumetric image of the object (12) by scanning or computed tomography; and the second three-dimensional representation in the form of a volumetric image of the object (12) by magnetic resonance. A three-dimensional registration method according to any one of claims 1 to 5, wherein the object (12) is a human or animal patient head and the referencing ancillary (24) is a device fixed on this head with a stability capable of inducing a submillimeter registration error, for example a forehead band stably fixed on the patient's forehead, a forehead pad stably fixed on the patient's forehead, or an oral device clamped in the patient's mouth between his teeth. Three-dimensional registration method according to claim 6, wherein the reference points (Pr) of the patient's head are non-aligned, comprising for example at least one nasion location point, one nasolabial junction location point and one external orbital rim location point when the referencing ancillary (24) is stably fixed on the patient's forehead. A computer program downloadable from a communication network and / or stored on a computer-readable medium and / or executable by a processor, comprising instructions (50, 52, 54) for executing the steps of a three-dimensional registration method of three-dimensional representations of an object (12) on the object (12) itself according to any one of claims 1 to 7, where said program is executed by a computing unit (44) of a device (10) for navigating within the object (12), and where this device (10) further comprises: a memory (48) for storing a first three-dimensional representation of the object (12) according to a first three-dimensional imaging mode, and locations of at least three reference points (Pr) of the object (12) in this first three-dimensional representation,of a second three-dimensional representation of the object (12) according to a second three-dimensional imaging mode other than the first three-dimensional imaging mode, and of the locations of the reference points (Pr) of the object (12) in this second three-dimensional representation; a referencing ancillary (24) intended to be fixed on the object (12); a stylus (28), manipulable by an operator, of which a tip (30) is localizable in a three-dimensional reference frame linked to the referencing ancillary (24); an instrument (20) of which a functional end (22) is localizable in the three-dimensional reference frame linked to the referencing ancillary (24); and a screen (18) for the simultaneous display of several planar reconstructions in cross-section of the object (12), including at least two planar reconstructions of the same cross-section of the object (12) obtained respectively from one and the other of the first and second three-dimensional representations. Navigation aid device (10) for an object (12), comprising: a memory (48) for storing a first three-dimensional representation of the object (12) according to a first three-dimensional imaging mode, locations of at least three reference points (Pr) of the object (12) in this first three-dimensional representation, a second three-dimensional representation of the object (12) according to a second three-dimensional imaging mode other than the first three-dimensional imaging mode, and locations of the reference points (Pr) of the object (12) in this second three-dimensional representation; a computing unit (44) designed for three-dimensional registration of said first and second three-dimensional representations of the object (12) on the object (12) itself; a referencing ancillary (24) intended to be fixed on the object (12);a stylus (28) of which a tip (30) is locatable in a three-dimensional reference frame linked to the referencing ancillary (24); an instrument (20) of which a functional end (22) is locatable in the three-dimensional reference frame linked to the referencing ancillary (24); and a screen (18) for the simultaneous display of several planar reconstructions in cross-section of the object (12), of which at least two planar reconstructions of the same cross-section of the object (12) are obtained respectively from one and the other of the first and second three-dimensional representations;in which the computing unit (44) is more precisely designed (50, 52, 54) to perform: a three-dimensional angular registration of the first three-dimensional representation on the object (12) from a recording, by interaction with the tip (30) of the stylus (28) when it is manipulated by an operator, of the locations of the reference points (Pr) of the object (12) in the three-dimensional reference frame linked to the referencing ancillary (24);a three-dimensional surface registration of the first three-dimensional representation on the object (12) comprising: an extraction of a surface of the object (12) in the first three-dimensional representation, a recording of locations of a plurality of surface points (Ps) other than the reference points (Pr) on the surface of the object (12) in the three-dimensional reference frame linked to the referencing ancillary (24), and the calculation of the three-dimensional surface registration from this recording of surface point locations; the calculation unit (44) being designed (54) so ​​that the three-dimensional registration of the second three-dimensional representation includes a three-dimensional surface registration of this second three-dimensional representation from the recording of the surface point locations (Ps) made for the surface registration of the first three-dimensional representation;characterized in that the recording of the locations of the plurality of surface points (Ps) other than the reference points (Pr) on the surface of the object (12) in the three-dimensional reference frame linked to the referencing ancillary (24) is done by interaction with the tip (30) of the stylus (28) when it is manipulated by an operator; and in that the computing unit (44) is designed (58, 60) to switch the display between several planar reconstructions in section of the object (12) according to the first three-dimensional representation, several planar reconstructions in section of the object (12) according to the second three-dimensional representation and several planar reconstructions in section of the object (12) according to the first and second three-dimensional representations, this switching being activatable by a predetermined approach between the functional end (22) of the instrument (20) and a calibration pad (31) of the referencing ancillary (24).; Device (10) for navigation aid in an object (12) according to claim 9, wherein the computing unit (44) is further designed (58, 60) to locate and visually display the functional end (22) of the instrument (20) in each planar cross-sectional reconstruction of the object (12) displayed by the screen (18).

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