Description

[0001] The 3D ultrasound scanning with the recording of the spatial position of two- dimensional ultrasound frames has been described as a method by several authors and the technical implementation methods have been synthetically presented by Pedersen and Szabo T in patent W02006 / 127142A2. The position of each two-dimensional frame is determined by a device that identifies the spatial position of the transducer during scanning. This is usually a self-standing device, distinct from the ultrasound machine. Each bi-dimensional frame is assigned a label with its own spatial position, which generates an ultrasonographic 3D reconstruction with enhanced accuracy. This reconstruction is quantitatively appropriate [1] In the case of ultrasonographic three-dimensional reconstruction methods based on bi- dimensional, time-synchronized spatial positioning information obtained using accelerometer- and gyroscope-type spatial positioning sensors [1], - but also for the other mentioned cases, prior to ultrasonographic scanning - there is a need for a spatial calibration phase, recommending the use of spatial calibration methods pertaining to other authors [1]

[0002] The solution of the aforementioned authors was to apply sensors for reading the variation of spatial position to of the bi-dimensional transducer. The process of reading and applying position labels for each bi-dimensional ultrasonographic frame is carried out in relation to an initial position, acquired at a certain time, chosen arbitrarily. This brings about 2 potential consequences which remain unsolved: the accumulation of errors over time as the three-dimensional scan is being performed and the inability to resume an interrupted scan, given the arbitrary and impossible to replicate manner in which this initial reference was chosen.

[0003] There are no detailed methods for reducing the subject's motion artifacts and for resuming the scanning procedure of the object after qualitative and quantitative evaluations of the obtained 3D model. Current methods of three-dimensional ultrasonographic reconstruction do not solve the problem of completing the 3D ultrasound model after an evaluation performed by the operator, by resuming the scanning procedure.

[0004] Previous methods have been described, methods which, based on physical correlations in of the real world, manage to automatically or semi-automatically overlap 3D models of the same scanned areas with the help of complementary technologies [2] There are, however, disadvantages in this case: it is mandatory to scan the patient in the same session using both the ultrasound machine and X-ray scans. [0005] Another solution was that of coupling the transducer of an ultrasound machine to a robotic arm controlled by the operator using a computing unit. Consequently, a system designed in this way can be utilized by employing the computing unit [4], but it is not specified how the following factors can be reduced: the patient's motion artifacts, those of the examined area or the manner of choosing the incidence in which the ultrasonographic data is acquired with respect to the patient. Ultrasonographic 3D reconstruction methods are usually performed by moving the transducer using stepper motors, obtaining parallel bi-dimensional frames that do not take into account the anatomical shape of the examined areas when deciding the incidence of the acquired ultrasonographic, bi-dimensional frame with respect to the examined area.

[0006] The accuracy in terms of trueness and reproducibility of 3D ultrasonographic reconstructions depend on a multitude of factors such as: immobilization, fixation of the examined area throughout the scan with respect to the coordinate system of the spatial positioning reading sensors, which also includes the implementation of algorithms meant to compensate for the patient's movement, as well as resilience of the examined tissues and how they become deformed during the scan. Choosing non-deformable, low-resilience tissues that can be immobilized or fixed during scanning would be helpful in developing 3D ultrasound scanning methods. Periodontal tissue can generate provide such an easily controllable context or environment.

[0007] Gingival soft tissues are currently being examined using the gold standard recommended by the World Health Organization, namely periodontal probing. This is an invasive analog method, dependent on an operator, with low accuracy and reproducibility. The emergence of an imaging method that would assess and monitor the evolution of this condition which has a particularly high incidence worldwide is necessary for the application of appropriate prevention methods.

[0008] With regard to 3D periodontal ultrasonographic examination, there is a solution that describes the use of a spatial positioning system in order to enable the three-dimensional reconstructions of the periodontal areas examined, starting from the acquired two-dimensional ultrasonographic frames [4]

[0009] The practical applicability of these last two 3D ultrasonography methods is not currently realized or recognized on a large scale, precisely because the efficient methods of immobilizing the examined areas are not described, which is decisive in terms of the quality of the three- dimensional ultrasonographic reconstructions that are obtained. Another inconvenience is that the data acquisition is carried out by positioning the transducer at the level of the examined area with the help of stepper motors that restrict the choice of ultrasonographic incidence in order to obtain high-quality, two-dimensional images. As the movement of these stepper motors is linear, the transducer cannot effectively follow the curvatures of the examined areas and the two-dimensional ultrasonographic images are strongly artifacted.

[0010] The method presented by Salcudean et. al., which uses a robotic arm for mechanized transducer positioning, focuses on examining areas of the human body that are difficult to immobilize and easily deformable. The periodontium scanning method suggested by Mukdadi et. al. especially describes the in vitro examination of parts, precisely in order to avoid the problem of immobilizing the patient. Studies carried out by the same author are performed exclusively in vitro, using pig mandibles and not in vivo, using patient immobilization techniques [5] As the areas of interest are not immobilized in the case of in vitro examinations or patients, by developing certain methods for fixing the scanned areas relative to the scanner’s reference system of spatial coordinates, it is not possible to resume and correct defects in the three-dimensional ultrasonographic model that is obtained.

[0011] Other previously proposed periodontal ultrasonographic 3D scanning methods [6] solved the problem of in vitro acquisition of 2D ultrasonographic data and their transformation, by adding synchronized spatial position information into 3D frames that subsequently make up the scanned volume. The positioning of the transducer is also achieved using stepper motors that have low efficiency in the area of the curvatures of the maxilas. Also, the immobilization process takes place by applying belts at the level of the patient's skull cap, scanning each tooth in turn, segmentally. Subsequently, the composition of the acquired volumes occurs.

[0012] The method of three-dimensional ultrasonographic scanning and 3D modeling, proposed in this paper, with respect to areas of interest which are fixed in relation to the reference system of the three-dimensional ultrasound scanner eliminates the aforementioned disadvantages by offering a complete scanning solution consisting in a specially designed ultrasound 3D scanner based on a Portable Coordinate Measuring Machine (CMM) and a standard ultrasound machine. The coordinate measuring machine will be responsible for determining the spatial position of the ultrasound transducer during ultrasonographic scans. Data from these devices is read and processed to perform a three-dimensional modeling of a patient's soft tissues and hard tissues (bone and teeth) surfaces in the area of the head and neck. The ultrasonographic 3D reconstruction is performed by employing methods for fixing the examined areas in relation to the coordinates reference system which belongs to the system responsible for determining the spatial position of the transducer of the three-dimensional ultrasonographic scanner. Tissues in the head area, especially gingival tissues, have low resilience and low thickness and can be considered immobile and non-deformable during scanning. Immobilizing them with respect to the spatial coordinates reading system during the scan is necessary in order to increase the accuracy of the three-dimensional ultrasound reconstructions, eventually reaching a similar accuracy as in the case of scanning non- deformable and immobile objects in relation to the reference system of the scanner's spatial positioning system.

[0013] Other ultrasonographic scanning methods propose the correction of motion artifacts using estimated data and do not use volumetric data correlated to real-world information recorded using spatial positioning sensors [7]

[0014] 3D scans used to assess a patient's maxillas are currently performed using X-rays, Cone Beam Computed Tomography. The motion artifacts are attenuated by employing various methods of compensation for the patient's movements, such as optical sensors that record the patient's head movements during X-ray scans [8]

[0015] An ultrasonographic 3D scanner complements the information generated by the X-ray, by providing data on the soft tissues and hard tissue surfaces examined, which could be an integral part of a complex and complete 3D model of the scanned area. This model would be carried out by X-ray imaging investigations (Cone Beam Computed Tomography) which reconstruct 3D hard tissues, but which do not have a sufficient resolution of soft tissues. The outer surfaces of the scanned object can be modeled three-dimensionally using optical scanning methods and in the case of the oral cavity using intra-oral 3D scanners. CBCT and intra-oral optical scanning are widely used in dentistry nowadays, but there is no method or product that is currently usable for the in-depth 3D imaging examination of soft tissues. The soft tissue layers located between the hard tissues and the outer surfaces will be reconstructed three- dimensionally using ultrasonography at high resolution and having low artifacts.

[0016] The problem solved by the present invention:

[0017] Ensuring the predictability of the spatial position of the results of ultrasonographic examinations in 2D frames recorded by fixing and calculating the position of the examined area with respect to the reference system of the device used to determine the spatial position of the 2D probe of a 3D ultrasonographic scanner, especially designed for this purpose. This would be done by employing a calculation method of a point that represents the absolute origin of the examined area, both in the real world and in the three-dimensional reconstruction obtained following the ultrasonographic 3D scan.

[0018] Once this predictability is ensured, it will be possible to:

[0019] 1. Perform three-dimensional ultrasonographic reconstruction of scanned areas with enhanced accuracy;

[0020] 2. Complete an ultrasonographic 3D model obtained by resuming scanning in areas where the acquired resolution or information is not sufficient;

[0021] 3. Merging the obtained ultrasonographic 3D model with 3D models made for the same area examined by X-ray scanning with Cone Beam Computed Tomography technology, obtained by intra-oral optical scans or any other 3D reconstructions obtained using complementary medical imaging technologies by applying the calculation method of a point that represents the absolute origin of the examined area.

[0022] Means of achieving the 3D ultrasound low artifacts reconstruction:

[0023] - Ultrasonographic 3D scanner especially designed for this purpose (fig. 1 and 2) comprised of a standard ultrasound 3 having a two-dimensional transducer 5 and a system 2 for determining the spatial position of the transducer 5 which allows the calculation of its spatial position and angulation on the 3 axes - i.e., a coordinate measuring machine, such as an articulated arm or an optical system [10], with the optional function of scanning a surface by palpation; and

[0024] - Elements of mechanical immobilization or immobilization by calculating the relative position in real time throughout the ultrasonographic scanning of the examined area relative to the coordinate reference system (coordinate measuring machine) 2 for determining the spatial position of the transducer 5 of the ultrasonographic 3D scanner.

[0025] Input data for 3D ultrasound reconstruction:

[0026] - 2D ultrasound images obtained in a freehand manner, incidences chosen arbitrarily by the operator. Two-dimensional ultrasound frames can be obtained in a manual, operator- dependent or semi-automatic mode, the human operator being guided by a software for analyzing the result obtained or fully robotically, automatically, the incidences of two- dimensional ultrasonographic frames obtained by robotic movement of the transducer assisted by the computing unit 1 by predictions conducted about the tracked anatomical structures

[0027] - spatial position data for each ultrasound frame acquired: system meant to determine the spatial position of the ultrasound transducer that allows real-time calculation of the position and angulation on the 3 axes of the ultrasound probe during the examination

[0028] Output data:

[0029] A 3D ultrasound model containing the modeling of scanned soft tissues and hard tissue surfaces in the scanned area.

[0030] Method of achieving the 3D ultrasound low artifacts reconstruction:

[0031] Calculating an absolute origin of the examined area provides us with the possibility to interrupt the acquisition in order to analyze the obtained result and resume the 3D scanning if the 3D model does not correspond qualitatively or quantitatively, as well as the possibility of aligning ultrasonographic 3D models or other 3D models of the same examined area obtained by using other alternative imaging technologies, at different times from the moment they are generated.

[0032] Advantages of the proposed method:

[0033] - The proposed method manages to overlap the three-dimensional scans obtained using complementary imaging technologies or the same technology by correlating 2 or more scans, by calculating an absolute origin of the examined area, without having to scan, in the same session, in order to obtain three-dimensional models of the examined area. The time interval between 2 scans is not significant, as long as the position of the teeth does not change.

[0034] - As it is a freehand two-dimensional scan, high quality ultrasonographic images can be acquired because the incidence of the ultrasonographic plane can be chosen according to the ideal incidence at the level of the examined surface. This choice can be made by a human operator (being dependent on it) or by a human operator assisted by the computing unit in the case of an operator who is less experienced in medical imaging. It could also be done in a completely independent manner, through software predictions and robotic examination.

[0035] - By calculating the absolute origin of the examined area, it will be possible to automatically fuse the obtained scans by employing complementary imaging technologies. Every voxel in the obtained three-dimensional reconstruction has, as a reference, the calculated absolute origin.

[0036] - Through the 3D ultrasonographic reconstruction of the examined areas, it will be possible to interpret the results subsequent to performing the examination, even remotely. This is currently impossible in terms of ultrasonographic investigations, as the ultrasonographic method is dependent on the operator [10,11]

[0037] - The calculation of an absolute origin of the examined area will allow comparisons to be made with respect to the evolution of the disease through monitoring performed with high accuracy, operator independent.

[0038] - The non-invasive character of the imaging technique will make it possible to monitor the evolution of the condition without restricting side effects such as those generated by cumulative ionizing radiation, as in the case of CBCT performed with X-rays, the imaging method of choice for most dental conditions nowadays.

[0039] The following is a representation of the invention in connection to the ultrasonographic 3D scanner (Chifor Ultrasound Tomograph) schematically displayed in Fig. 1 and Fig. 2.

[0040] Fig 1 - Schematic representation of a three-dimensional ultrasonographic scanner consisting of a system for determining the angulation and spatial position of the transducer on the 3 axes, ultrasound machine and computing unit,

[0041] Fig 2 - 3D ultrasound scanner consisting of a system meant to determine the spatial position of the transducer represented by an articulated arm for coordinate measuring, computing unit and an ultrasound machine with a 2D transducer.

[0042] The three-dimensional ultrasound scanner consists of a computing unit 1 that reads data from a spatial positioning system represented by an articulated arm used for coordinate measuring 2 at the probe to which the transducer 5 is connected, coupled. The function is that of handheld ultrasound scanner of an ultrasound machine 3, generating a multitude of two- dimensional images of the explored area.

[0043] Simultaneous reading of the spatial position with the acquisition of each two- dimensional frame is performed at the command of the computing unit 1 and is ensured by the system 2 for determining the spatial position of the transducer 5. Temporal synchronization of the two-dimensional ultrasound frames with spatial position data will be performed by the unit of calculation 1 by ordering (at a given time) the acquisition of the two-dimensional frame, to which a time label will be applied, from the ultrasound machine 3 through the transducer 5 and by ordering (at the same point in time) the acquisition of spatial positioning data, to which a time label will be applied by the computing unit 1, from the spatial position reading system 2 by means of the probing palpation probe 4. If the ultrasound machine 3 is a device that does not allow the command for the acquisition of two-dimensional frames at a certain moment of time by the computational unit 1, then the data synchronization process will be performed through temporal synchronization (diagram 1, temporal synchronization of data by means of finding a unique event in the 2 data streams acquired from the ultrasound machine 3 and from the spatial position reading system 2 of the transducer 5).

[0044] The spatial localization read by the system 2 of the transducer 5 may also have an optional palpation function of some areas of interest accomplished the probe 4 in order to locate them spatially, relative to the reference system in X, Y, Z coordinates of the probe 4 (fig 2). The system 2 which determines the spatial position of the transducer 5 may be, for example, a coordinate measuring machine, such as an articulated arm 2 or an optical system 14, with the optional function of scanning a surface by palpation. The probe 4 and the transducer 5 are used in the unit of the 3D ultrasound scanner generating the transducer-probe assembly 6 (fig. 1, fig. 2). To establish the spatial position of the two-dimensional ultrasonographic frames, their reference system XI, Yl, Z1 originating in the corner of the acquired two-dimensional ultrasonographic frame (XI width, Z1 height) and the direction of movement of the transducer generating the Yl axis (fig. 2). Their determination with respect to the coordinate reference system X, Y, Z in of the ultrasound 3D scanner, which is the same as the spatial coordinate reference of the system 2 for determining the spatial position of the transducer 5 (fig. 2) is done by applying a transformation matrix, following a spatial calibration process [1], prior to the ultrasonographic 3D scanning. The calculation algorithms will be implemented using the computing unit 1.

[0045] The result of the ultrasound explorations using the ultrasonographic 3D scanner will be the three-dimensional ultrasonographic modeling of some fixed areas of interest with respect to the X, Y, Z reference system of the scanner fig 2.

[0046] The process of constructing the reference base for the ultrasonographic measurement of a jaw maxilla, by fixing the examined area relative to the spatial coordinates system for determining the spatial position of the transducer. [0047] Step 1 : Perform three-dimensional intra-oral optical scanning

[0048] Step 2: Obtain digital information to describe the three-dimensional optical reference model of the dental arch.

[0049] Step 3: Design and build the custom mouth guard through by means of three- dimensional computerized manufacturing.

[0050] Step 4: Apply the mouth guard to the dental arch

[0051] Step 5: Fixate the maxila using the individual custom mouth guard, fitted into one of the fixing solutions - 1, 2 or 3

[0052] Step 6: Calibrate and calculate the absolute origin of the fixed examined area

[0053]

[0054] The description of the custom mouth guard and the instructions for its usage are displayed in:

[0055] Fig. 3 - Custom mouth guard A made in order to fixate maxilla B

[0056] Fig. 4 - Custom mouth guard A, customized fixing element of maxilla B, with flat benchmarks 10 necessary to calculate the absolute origin O of the examined area B relative to the coordinate system XI, Yl, Z1 of the spatial position reading system 2 of the 2D ultrasonographic probe 5 of the 3D ultrasound scanner

[0057] Fig. 5 - Custom mouth guard A with marks 10 applied to the maxilla of patient B, lateral view

[0058] Fig. 6 - Alternative 1: mechanical immobilization of the patient's head using the immobilization assembly described in the patent application submitted to OSIM Romania (State Office for Inventions and Trademarks, Romania), entitled "Assembly and method of immobilization of the head for three-dimensional examinations" with registration number 2019 00641 / 10.10.2019.

[0059] Fig. 7 - Alternative 2: fixing the examined area B is done by fitting the maxilla with a custom mouth guard with 3 flat surfaces 10 pinned to a second articulated arm 13.

[0060] Fig. 8 - Alternative 3: fixing the examined area fitting the maxilla B with a custom mouth guard A attached to a support, having applied targets marks on it 15 to detect its position by means of an optical space positioning system 14. Transducer 5 is caught in a support with marks 16 applied in order to detect its position by using an optical spatial positioning system

14.

[0061] The following is an example of the procedure of building the reference base for the ultrasonographic measurement of a maxilla, by fixing the examined area relative to the reference of the coordinate system responsible for determining the spatial position of the transducer: A custom mouth guard manufactured by computer-aided design and manufacturing technology is used nowadays in another context as a surgical guide for the application of dental implants. Through an orifice, a milling cutter is inserted wherewith the bone is milled in order to apply the implant. The custom mouth guard is designed with the help of a software, starting from the optical impression of the maxilla on which it will be applied. By overlapping the optical fingerprint over the CBCT (Cone Beam Computed Tomography), the depth and the angle of the bone implant can be applied to are both calculated.

[0062] Step 1

Starting from the existing optical scanning technology of a maxillary arch, an intra-oral scanner is used to generate an optical impression, scan of the maxillary arch which will be ultrasonographically examined. Alternatively, a classic impression of the maxillary arch can be made, after which a dental laboratory will digitize the respective impression.

[0063] Step 2

With the help of a software, the custom mouth guard A Fig 3 and 4 is designed, at the level of which the handle 9 is applied in the computerized design phase, with the help of which it will be connected or mounted using one of the 3 used alternatives in fixing the examining area. Also, at least 3 plane marks 10 will be applied, used for the subsequent alignment of 3D models obtained by through the method of calculating the absolute origin O.

[0064] Step 3

Step 3 consists in the computerized manufacturing by milling or 3D printing of the custom mouth guard A. The mouth guard A has a concave, irregular part 7, 8, which is the negative of the occlusal (biting) surfaces of the teeth 7 and the lateral surfaces of the teeth 8 (about 20-30% of the external, buccal and oral surfaces). In this area, the patient's teeth are fixated. In the case of the rest of the convex, exterior areas 11, a stiffening occurs or these result from the project or the execution technique. The handle 9 is part of the connection area within step 5. At the level of the outer surfaces of the mouth guard, there are at least 3 flat surfaces 10. These flat surfaces 10 are arranged such that through their virtual extensions a, b, c they intersect virtually at one point, generating the absolute origin O. This point O represents, in the real world, the spatial reference generated by the intersection of the 3 flat surfaces at landmarks 10 for the examined maxillary area B and in the virtual world, it represents the spatial reference of the three-dimensional ultrasonographic reconstruction, each voxel relating spatially to this point O.

[0065] Step 4

Step 4 is represented by the application of the mouth guard at the level of the maxilla B Fig. 5. Considering the impressions from the internal surface of the mouth guard 7 and 8 representing the negative of the dental surfaces through which the mouth guard A will be positioned at the level of the maxilla B, it will be considered from now on that the mouth guard A ‘fuses’ with the maxilla B, as there is sufficient rigidity between them for changes to appear during the scan, compared to the reference system X, Y, Z.

[0066] Step 5

Step 5 represents the fixation of the maxilla B by using the individual mouth guard A, mounted in one of the fixing solutions - alternatives 1, 2 or 3. This fixation of the mouth guard B aims to reduce the movement artifacts by mechanically immobilizing the examined area B, in case of alternative 1 or offering the possibility to calculate the movements of the maxilla B, compared to the reference system X, Y, Z in the case of alternatives 2 or 3. In the case of connecting the mouth guard through alternative 1, the mechanical restraint assembly of the examined area Fig 6, it enters a support area or alternative 2 - is connected to a second articulated arm used as a spatial positioning system 13, Fig 6 of mouth guard B or alternative 3 Fig 7 is connected to the support 15, for the marks of the optical system 14, the measuring machine in coordinates (Fig 6 alternative 2, spatial positioning system provided by a second articulated arm or Fig 7 alternative 3, marks of the optical positioning system of the transducer). The articulated coordinate measuring arm 2 and the articulated coordinate measuring arm 13 are stationary relative to each other. By fixing the mouth guard by means of alternative 2, the position of the absolute origin and implicitly that of the examined area can be calculated relative to the X, Y, Z coordinate system of the spatial positioning reading system 2 of transducer 5. Using the same principle, it will be possible to use alternative 3 for the same purpose of calculating the position of the ultrasonographic plane XI, Yl, Z1 relative to the absolute origin O of the examined area B during the ultrasonographic 3D scan. [0067] Steps 1-5 are performed separately for each maxillary arch (upper jaw, lower jaw = mandible)

If the scan is to be performed at the level of the head or neck, except for the mandible, steps 1 - 5 are performed only for the upper jaw. The maxillas are fixed individually relative to the X, Y, Z coordinate system of reference of the 3D ultrasound scanner. Each examination/data acquisition process will be performed separately for the upper jaw and separately for the mandible. By fixing the upper jaw through this procedure, the premises for the acquisition of data for the entire head and neck are created, the upper jaw being an integral and immobile part of the skull.

[0068] Step 6 detailed with the help of

[0069] Fig 9 - Palpation in at least 3 non-linear points of a plane element at the level of the mouth guard in order to fix and calculate the spatial position of the respective plane relative to the coordinate reference system of the spatial position reading system of the 2D probe pertaining to the ultrasonographic 3D scanner

[0070] Fig 10 - Ultrasonographic scanning of the 3 plane elements at the level of the mouth guard in order to fix and calculate the spatial position of the examined area relative to the coordinate reference system of the spatial position reading system of the 2D probe pertaining to the ultrasonographic 3D scanner in order to subsequently report the scanning result to the calculated absolute origin.

[0071] Diagram 1: The method of fixing and calculating the position of the examined area, relative to the coordinate reference system of the spatial position reading system of the 2D probe of a 3D ultrasound scanner.

[0072] Palpation of the 3 plane elements 10 of the mouth guard A in order to fix and calculate the spatial position of the examined area B relative to the coordinate reference system X, Y, Z of the spatial position reading system of the 2D ultrasound probe of the 3D ultrasonographic scanner in order to subsequently report the result scan to the absolute origin O calculated (Fig.

9)·

[0073] Ultrasonographic scanning in 2 different incidences ual and ua2 of a plane element a between the 3 landmarks 10 at the level of the mouth guard A in order to fixate and calculate the spatial position of the respective plane relative to the reference system of the coordinate spatial position XI, Yl, Z1 of the 2D probe of the 3D ultrasound scanner. [0074] The fixation using this procedure is done performed for the following reasons and having the following expectations/objectives:

[0075] (a) Reduction of motion artifacts by using error compensation algorithms (optical system or a second articulated arm, coordinate measuring machine in which the mouth guard is fitted, the spatial positioning system of the transducer 5 may be replaced by electromagnetic sensors or sensors from the accelerometer and gyroscope range or any system from which the 3 necessary translations and 3 rotations can be read) or by mechanical immobilizations (containment assembly, alternative 1)

[0076] (b) Easier fusion of complementary imaging technologies results for the examination of the same area in order to achieve a complete and complex 3D reconstruction of the explored area without first having to segment the 2D images or the reconstructed 3D obj ects. The overlay will generate information about the structures in their entirety: hard tissue surfaces and in-depth (X-rays), soft tissue surfaces and in-depth (ultrasonography), hard and soft tissue surfaces exposed in the oral cavity (optical impressions/ intra-oral scanning)

[0077] (c) This fusion of complementary imaging technologies will enable automated segmentation to be achieved by applying a process of intersection of sets of 3D points obtained by the aforementioned complementary imaging technologies.

[0078] Following the construction of the reference base for measuring a maxilla, by performing ultrasonographic scanning or palpation of flat surfaces, the mouth guard provides the coordinates of the jaw maxilla, of the area examined by establishing its absolute origin O.

[0079] If the fixation is done on the maxilla, the absolute origin of the patient's maxilla, head and neck is obtained.

[0080] If the fixation is made at the level of the mandible, the absolute origin is calculated for the mandible.

[0081] 3D Ultrasonography of the area of interest: data acquisition and generation of the ultrasonographic 3D model (Ultrasound Chifor Tomography)

[0082] The patient scanning procedure is presented in:

[0083] Diagram 2: 3D Scanning method and completion of the ultrasonographic 3D model obtained by resuming the scan [0084] Diagram 3: Process of obtaining the spatial calibration matrix of the ultrasonographic plane with the output data of the transducer’s spatial positioning system

[0085] Fig 11 - 3D Ultrasonography of an upper jaw, using Alternative 1 as a solution for fixing the examined area - mechanical head restraint

[0086] The transducer 5 is attached to the unit, by means of part 6, with the probe 4 of the system 2 for determining the spatial position of the transducer 5. They will be used only as fixed in a rigid assembly 6. The rigidity of the assembly 6 will determine the quality of the scan result. The area of the maxilla B to be scanned will be fixed, in advance, by the procedure of fixing the examined area according to diagram 1. The process of establishing the reference base of the ultrasonographic measurement by fixing the examined area in relation to the reference coordinate system X, Y, Z will be performed using Alternative 1, in this example, by going through steps 1 to 6. Subsequently, the movements of the assembly 6 are performed by the operator in order to position the transducer 5 in the appropriate incidence for the acquisition of images of 2D ultrasonographic frames. The ultrasound plane aU will intersect the jaw maxilla B in the incidence chosen by the operator. The ultrasound machine 3 generates the 2D ultrasonographic frame according to diagram 2 and the spatial position determination system 2 of transducer 5 generates spatial position data, bringing information about translation on the X, Y, Z axes and roll, pitch, and yaw angulation (diagram 2). These 2 data streams represent the input data for 3D ultrasonographic reconstruction algorithms. The temporal synchronization of the data will be performed with hardware, by the command generated by the computing unit 1 or by the temporal synchronization procedure which involves the identification of a unique moment in time in the 2 data streams generated - for example by repeatedly touching a hard, flat and fixed surface in relation to the reference coordinate system X, Y, Z generating (in the position data) the repeated blocking of the values on a certain axis, for example Z. In 2D ultrasonographic frames, it will generate the appearance of a sudden image change in exactly the same moment of time by identifying a line on the ultrasound machine screen 3 generated by the intersection of the ultrasonographic plane aU with the plane of the hard surface with which the transducer 5 comes into contact.

[0087] Coordinate measurements of the translational and rotational movements of the assembly 6, obtained in the X, Y, Z coordinate system of the system for determining the spatial position 2 of the transducer 5 to which a calculation algorithm will be applied, using a rotation matrix generated as a result of the spatial calibration process according to Diagram 3. This will generate the translation and rotation of the ultrasonographic plane aU of the transducer 5 in the coordinate system XI, Yl, Zl. In this way, when acquiring a 2D ultrasonographic frame, a corresponding spatial position will be generated in the XI, Yl, Zl coordinate system, containing information about the translation and rotation of this plane, obtaining an ultrasonographic 3D frame to as displayed in Diagram 2.

[0088] The grouping of several 3D ultrasonographic planes in the XI, Yl, Zl coordinate system will generate the 3D ultrasonographic model of the examined area. It will have the absolute origin O calculated according to the plane landmarks 10 of the mouth guard A in the

X, Y, Z coordinate system following the application of the procedure for fixing the examined area by palpating them. If the fixation of the examined area is done by ultrasonographic scanning of the landmarks 10, the absolute origin O will be obtained in the XI, Yl, Zl coordinate system. In order to pass the position data which are is formed by the translation read on the 3 axes and the rotation of roll, pitch and yaw from the X, Y, Z coordinate system to the

XI, Yl, Zl system, the calibration matrix resulting from the procedure spatial calibration is applied. When the operator considers that the area of interest has been covered by ultrasound scanning, he can stop scanning and evaluate the obtained 3D ultrasonographic model. This evaluation can be done carried out in the same meeting or in another meeting at a different time. If completing the 3D ultrasonographic model is desired, the previous steps are repeated, starting with fixing the examined area B to the reference system X, Y, Z by palpating the landmarks 10 or to the reference system XI, Yl, Zl or by ultrasonographic scanning of the landmarks 10. After the calculation of O, the scanning procedure can be resumed by the operator in the area where the ultrasonographic 3D model is inadequate, from a qualitative or quantitative point of view. This process of completing the scan can be resumed as many times as it is desired (Diagram 2), until a final ultrasonographic 3D model is obtained by ensuring a sufficient density/resolution of the 3D ultrasound reconstruction.

[0089] The process of aligning 3D ultrasound models using the absolute origin

[0090] This procedure requires the use of three-dimensional ultrasonographic models subsequent to examinations performed at different times or obtained by using complementary imaging technologies being detailed in:

[0091] Diagram 4: A complete and complex 3D model of the examined area obtained by the fusion of complementary imaging technologies examination results after scanning the same area visualizing all the hard and soft anatomical structures. [0092] If it is desired to align ultrasonographic 3D models to perform automated or semi- automated comparisons this will be possible if the scan was performed after calculating the origin O using the 3D scanner (Chifor Ultrasound Tomography Scanner) presented and going through the steps of the construction process of the reference basis for ultrasonographic measurement of a maxilla. In the case of the upper jaw, the measurement and alignment of the ultrasonographic 3D model can be performed for the entire head and neck region. As long as the position of the teeth does not change, the mouth guard A can be reused by fitting the dental arch of the maxilla B of the same patient. 3D Ultrasonographic models made at different times following ultrasonographic explorations performed after fixing the maxilla B by using the mouth guard A and calculating the absolute origin O using the marks 10 at this level can be aligned with minimal computational effort and high accuracy without requiring post-processing of all two-dimensional ultrasonographic images acquired from the area of interest. It is only necessary to identify the spatial position of the 3 planes 10 at the level of the mouth guard A.

[0093] Imaging explorations will be performed using complementary technologies, subsequent to the application of the mouth guard A to the patient. The flat surfaces of the marks 10 will be identified in 3D models obtained of the examined areas.

[0094] The last stage is the alignment of the 3D models obtained using complementary technologies, by using the calculated absolute origin O and their integration in a complete and complex 3D model (diagram 4).

[0095] References

1. Pedersen PC, Szabo TL. Free-hand three-dimensional ultrasound diagnostic imaging with position and angle determination sensors. Patent No WO2006127142A2, Pub. Date. 2006-11-30.

2. Mercier LT, Lindseth F, Collins DL. A review of calibration techniques for freehand 3- D ultrasound systems. Ultrasound Med Biol. 2005; 31(4): 449-71.

3. Gogin NPB, Florent R, Yves P, Cathier F. Combination of ultrasound and X-ray systems. Patent No.: US 2012/0245458 Al, Pub. Date: 2012-09-27.

4. Salcudean SE, Bell GS, Lawrence PD, Marko A, Jameson M. Robotically assisted medical ultrasound. Patent No.: US 6,425,865 Bl. 2002-07-30.