FR2719760A1 - Process of computer simulated radioscopy and aid to surgery. - Google Patents

Abstract

A computer-simulated radioscopy method for use in surgery, and particularly in microsurgery, wherein an exhaustive volumetric acquisition of digital images of the operating region is performed; a set of static sensors (16) is placed on the patient to determine a referential of at least three-dimensional co-ordinates; the acquired digital images and the referential are correlated; all of the operative features of the microinstruments (24) to be used by the surgeon during the operation are digitally input; a dynamic topological sensor (18) is lockably attached to the microinstrument used (24) in a predetermined position; the position of the dynamic sensor in relation to the referential is constantly monitored and the exact position of the distal end of the microinstrument (24) is calculated; and the exact position of at least the distal end of the microinstrument (24) on the corresponding digital image is displayed in real time on a screen (4) during the operation.

Description

 The present invention relates to a method of computer simulated radioscopy and aid to surgery, in particular to microsurgery.

 In general, in endocavitary microsurgery, a microscope for the areas to be operated that is substantially superficial is used as the operating visualization means, and an endoscope for the areas inaccessible to direct vision. However, microscope vision has its limits since it is a direct vision which sometimes requires the collapse of the surface structures before accessing the deeper structures. Endoscope vision then has the advantage of respecting the anatomical structures explored. However, it can be hindered by bleeding or anatomical changes.

In both cases, the neighboring organs remain invisible to the surgeon, who then risks damaging a noble organ without being able to discern it. It is thus obvious that the reliability of the operation depends on the only experience of the surgeon, since there exists in each operation a certain degree of uncontrollable uncertainty.

 To help the surgeon, it has become common to carry out radiological tracking by scanography or by means of nuclear magnetic resonance imaging (MRI) before the operation. All these visualization means, however precise they may be, are deferred over time in relation to the intervention. Radioscopy, on the other hand, gives images in real time, but it has many drawbacks linked in particular to its cost, its gravity which slows down the operation and above all the irradiation of the patient and the practitioner. The intraoperative scanner has been considered in exceptional situations, but cannot reasonably become routine.

 The invention aims to overcome these drawbacks and allow the surgeon to easily locate in real time any microinstrument he uses on a digital image previously recorded and this, without intraoperative irradiation.

 In the Panorama du Médecin ni 3905 of November 19, 1993, an article entitled "Medicine Affected by Virtual Reality" describes what surgery will be in the near future with the use of images obtained by CT. In this prospective article, it is specified that the virtual three-dimensional image and the endoscopic image must be connected to achieve the desired goals. It is therefore a simple registration of images.

In a more pragmatic and less prospective way, the EP document
AO 326 768 describes the use of an electro-goniometer, one end of which is fixed to the surgical instrument and the other to a reference block in the form of an articulated arm. The latter is maintained in a constant position relative to the patient by means of a screw introduced into the patient's tibia. This document essentially describes how to help the surgeon to position an instrument, essentially a saw blade or a drill, by identifying the precise position of this instrument.

 Document WO-A-90/09 141 describes a system using a surgical video microscope making it possible to obtain surgical imaging on a monitor. This imaging consists of a set of cross-sectional and plan views obtained by moiré interferometry, and more generally intended for microsurgery of the eye.

In addition, various documents, such as the article "Virtual
Reality Surgical Simulator: The First Steps ", published in Surg. Endosc., May-June 1993, 7 (3): pages 203-205, which describes various perspectives in microsurgery following the intensive use of simulators flight in aviation, or "Micromachining Technology and
Biomedical Engineering ", published in Appl. Biochem. Biotechnol. In March 1993, 38 (3): pages 233-242, which specifies the progress made in the micro-technologies notably by the stereo-television and the virtual images, show that there is nothing really concrete to date in the field of microsurgery.

 All of these documents clearly show that we know how to acquire a digital image by CT or MRI and that the personal computers currently available have sufficient computing power for image processing. On the other hand, it clearly appears that the technologies described in these documents do not master the means of locating the instruments and moving them in an operating field other than by intraoperative irradiation. Furthermore, none of these documents shows how a surgeon can be effectively helped when he has to operate in a sensitive and blind area.

 The invention therefore relates to a new concept of computer simulated radioscopy ("RSO") which is entirely desirable to suppress all irradiation during the operation, while retaining the same possibilities of visualization in real time.

 The present invention therefore relates to a new and concrete method of computer-simulated radioscopy and aid to surgery. It finds its preferred applications in endo-nasal or intra-spinal microsurgery, in intracerebral neurosurgery, in particular as a replacement for stereotaxic surgery, and also in orthopedics.

According to the invention, the method comprises the following steps
the complete volumetric acquisition of digital images is carried out by scanography, nuclear magnetic resonance imaging means or equivalent, of the region to be operated;
a set of static sensors fixed to a bone tissue fixed to the region to be operated is placed on the patient and determining a reference frame of coordinates at least three-dimensional;
a correlation is ensured between the digital images acquired and the above-mentioned reference frame;
all the useful characteristics of the micro-instruments that the surgeon has to use during the operation are digitally entered;
a dynamic topological sensor is fixed on the micro-instrument used by the surgeon, in a lockable manner and at a determined point;
the position of the dynamic sensor is determined at any time relative to the above-mentioned reference frame and the precise position of the distal end of the micro-instrument used is calculated; and
the precise position at least of the distal end of the micro-instrument is displayed in real time on a screen during the operation on the digital image corresponding to this position.

 Preferably, the dynamic topological sensor is fixed to the proximal part of the micro-instrument outside the operating field.

 The sensors can use all known physical principles (electromagnetic field, optical or infrared field, ultrasound, microwave, metal detectors, etc.), and combinations thereof. However, electromagnetic type sensors are preferred because they determine a six-dimensional signal including the spatial coordinates and the angular coordinates of the dynamic topological sensor.

 Preferably also, prior to the operation, the hazardous areas close to the operated region are determined on the digital image, the coordinates of these areas are recorded, and during the operation, a warning signal is determined as a function of the distance between the micro-instrument and, in particular, its distal end, and closest to the danger zones.

The invention will be better understood, and other objects, advantages and characteristics thereof will appear more clearly on reading the following description of the preferred embodiments given without limitation and to which a sheet of drawings is attached. on which:
Figure 1 schematically shows the installation required for the implementation of the method according to the invention; and
Figure 2 shows schematically a micro-instrument provided with sensors according to the invention.

 Referring now to the drawings and, more particularly to FIG. 1, the installation required for the implementation of the method of assisting the surgeon in microsurgery essentially comprises a computer 2 provided with a large computing capacity for managing images in real time. This computer is connected to a screen 4 forming a monitor for displaying the images processed and stored in an appropriate memory 6. This memory is favorably connected by modulator-demodulator and telephone line of a switched network 8 to a scanning processing center 10. In fact, the scanning processing center 10 is generally far from the operating room where the surgeon will practice, and it is necessary for him to receive digitized images.

 The monitor can also receive images from the microscope and the endoscope 12 via the computer 2.

 The control of the computer by the surgeon is done, for example, by voice or by foot, by means of an input device 14 comprising a validation key and means for moving a cursor accessible to the foot.

 A set 16 of static sensors is previously fixed on the patient, for example on a bone tissue secured to the region where the surgeon must operate.

 By the word "sensor" is meant a device making it possible to identify at least one position.

 This set 16 of static sensors will make it possible to determine a reference system necessary for monitoring the micro-instrument during the operation. At least one of these static sensors can favorably be secured to a bone area, for example to the skull, before the actual operation, while another will, for example, be secured to the palatal vault by means of a Inflatable balloon intended to fill the intra-oral volume and to limit mechanical stresses. In practice, a single judiciously placed static sensor is sufficient, but the addition of a second sensor makes it possible to validate the information at any time. In fact, if one of the static sensors detaches from the bone tissue, its movement will be automatically detected by the other sensor before it can result in the slightest error.

 A dynamic topological sensor 18 is locked on the microinstrument used by the surgeon. Usually, ten instruments are more than enough for the intervention with, at most, two instruments used simultaneously. The preferred system then comprises four sensors, two static 16 and two dynamic 18 temporarily locked to the instrument used.

 When the micro-instrument has a mobile part (micro-scissors or pliers, for example), it is necessary to know its degree of opening. An analog potentiometer 20 of potentiometer type is then added to the micro-instrument.

 Preferably, these sensors 16 and 18 each separately analyze the ambient electromagnetic field emitted by the interface 22. However, in this case, the micro-instruments are made of a non-ferromagnetic material, for example plastic or titanium.

 Alternatively, these sensors 16, 18 will use other aforementioned physical signals.

 The static 16 and dynamic sensors 18 are connected to an interface 22 whose output signal is applied to an input of the computer 2. This output signal gives, in real time, the measurement of the precise position of the dynamic sensor 18 in six dimensions including the Cartesian spatial coordinates of the sensor and the angular coordinates of its orientation of the pitch, yaw and roll type.

 Obviously, before any operation, the system is calibrated.

 FIG. 2 shows, by way of example, a micro-forceps 24 usually used in microsurgery. The opening angle B of the distal end forming a clamp 26 is measured by means of the analog sensor 20, while the dynamic topological sensor 18 is fixed to the proximal part of the micro-instrument at a determined point. It is necessary to relocate the sensor 18, so that the physical signal, for example electromagnetic signal, does not have to pass through the patient's tissues. In addition, a sensor fixed to the distal part of the micro-instrument would be troublesome both for the surgeon's vision and for his manipulation.

 Due to the relocation of the dynamic sensor 18, it is necessary to calculate the precise position of the distal end of the micro-instrument as a function of the location signal of the sensor and of the precise point where it is locked. For this purpose, all the useful characteristics of the micro-instruments that the surgeon will use during the operation must have been previously entered in the computer library.

 Before the operation, it is also necessary to ensure a correlation between the digital image stored in memory 6 and the frame of reference determined by the static sensors 16. To this end, the system is initialized by the surgeon by touching, with his microphone -instrument, a precise point of the patient, for example the inter-incisor gap or an external canthus, point easily determinable both on the digital image and on the patient.

 During the operation, the surgeon can control the computer 2 by means of the input device 14 or by voice to select a function, make an enlargement of the image, etc. On the screen 4, the precise position is displayed of the distal end of the micro-instrument and, simultaneously, the two-dimensional digital image corresponding to this position. Preferably, the screen 4 comprises several zones making it possible to display a plurality of two-dimensional images in different planes so as to make visible to the surgeon neighboring zones which he cannot physically see directly, and / or three-dimensional images.

 According to a preferred embodiment of the invention, before the operation, the surgeon determines on the digital image the dangerous zones close to the place where he is going to operate. The coordinates of these danger zones are then stored in memory 6. During the operation, the computer emits a warning signal when the distal end of the micro-instrument approaches one of these danger zones. Preferably, this warning signal is an audible signal the frequency of which is a function of the exact distance between any part of the micro-instrument used and the closest to these danger zones. This warning signal can also be a voice signal indicating the precise distance. This ensures security, especially when a dangerous area is absolutely not visible directly to the surgeon.

 According to an equally preferred embodiment of the invention, all the images displayed during the operation are recorded in memory 6. This recording can then constitute a postoperative magnetic report. In addition, the recording can be favorably used for educational or post-operative analysis purposes. For this purpose, the recording must be locked automatically to avoid any subsequent manipulation of the images (by analogy to what is commonly called "black box" in aviation). Such locking is necessary in forensic applications of the invention.

 Although we have represented and described what are currently considered to be the preferred embodiments of the present invention, it is obvious that those skilled in the art will be able to make various changes and modifications thereto without departing from the scope of the present invention as defined below.

Claims (11)

 1 - Process of computer-simulated radioscopy and surgical aid, according to which  an exhaustive volumetric acquisition of digital images is carried out by scanography, nuclear magnetic resonance imaging means or equivalent, of the region to be operated  a set of static sensors (16) fixed to a bone tissue fixed to said region is placed on the patient and determining a reference frame of coordinates at least three-dimensional  we ensure a correlation between the digital images acquired and the said frame of reference  all the useful characteristics of the microinstruments (24) that the surgeon is led to use during the operation are digitally entered;  a dynamic topological sensor (18) is fixed on the micro-instrument (24) used by the surgeon, in a lockable manner and at a determined point;  the position of the dynamic sensor is determined at any time relative to said reference frame and the precise position of the distal end of said micro-instrument (24) is calculated; and  the said precise position at least of the distal end of the said micro-instrument (24) is displayed in real time on a screen (4) during the operation on the digital image corresponding to this position.  2 - Method according to claim 1 characterized in that said dynamic topological sensor (18) is fixed to the proximal part of said micro-instrument (24) and outside the operating field so as to eliminate any physical signal passing through a tissue of the patient .  3 - Method according to claim 1 or 2 characterized in that said sensors (16, 18) are of the electromagnetic type.  4 - Method according to claim 3 characterized in that said micro-instrument (24) is made of a nonferromagnetic material.  5 - Method according to claim 1 or 2 characterized in that said sensors (16, 18) use at least one of the physical principles chosen from the group comprising an optical or infrared field, ultrasound, microwaves , metal detectors, and combinations thereof.  6 - Method according to any one of claims 3 or 4 characterized in that said sensors (16, 18) determine a signal in six dimensions comprising the spatial coordinates and the angular coordinates of said dynamic topological sensor (18).  7 - Method according to any one of the preceding claims, characterized in that the system (2, 22, 16, 18) is calibrated before the operation.  8 - Method according to any one of the preceding claims characterized in that one determines, in addition, the degree of opening (B) of the micro-instrument (24), if the latter comprises a movable part (26) .  9 - Method according to any one of the preceding claims, characterized in that lton displays on said screen (4), during the operation, a plurality of digital images in two dimensions according to different planes or digital images in three dimensions .  10 - Method according to any one of the preceding claims characterized in that it further comprises the following steps  prior to the operation, the hazardous areas close to said region are determined on the digital image  the coordinates of said zones are recorded; and  during the operation, a warning signal is determined as a function of the distance between any part of said micro-instrument (24) and the closest to said dangerous zones.  11 - Method according to any one of the preceding claims, characterized in that, in addition, all the images displayed on said screen (4) are recorded during the operation.