Intracortical-detection device and corresponding control method

Abstract

An intracortical-detection device including: at least one electrode that contacts a group of neurons; a first body, forming a surface that contacts a portion of a cerebral region; a first motor that moves the electrode with respect to the first body; a second motor; and a second body, operatively connected to the second motor, the first and second bodies being able to slide with respect to one another in a first direction, under the action of the second motor. The detection device moreover includes a sensor generating an electrical signal indicating a pressure exerted by the portion of cerebral region on the surface.

Claims

1. An intracortical-detection device comprising: at least one electrode configured to contact a group of neurons; a first body, forming a surface configured to contact a portion of a cerebral region; a first motor configured to move said at least one electrode with respect to said first body; a second motor fixed with respect to said first body; and a second body, operatively connected to said second motor, said first and second bodies being able to slide with respect to one another in a first direction, under the action of said second motor; a sensor configured to generate an electrical signal indicating a pressure exerted by said portion of cerebral region on said surface; a crank, which is coupled to said second body and can be driven in rotation by said second motor about a second direction transverse with respect to said first direction; and a constraint configured to prevent motion of said first body with respect to said second body in directions different from said first direction; wherein said sensor comprises a transducer arranged on said crank and configured to vary an own electrical quantity as a function of a deformation of said crank caused by the pressure exerted by said portion of cerebral region on said surface.

2. The detection device according to claim 1, further comprising a control unit configured to govern said second motor as a function of said electrical signal.

3. The detection device according to claim 2, wherein said control unit is configured to control said second motor so that said surface exerts a substantially constant pressure on said portion of cerebral region.

4. The detection device according to claim 1, wherein said crank is S-shaped and defines a first face and a second face parallel to one another and parallel to said second direction, said transducer being arranged on said first and second faces.

5. The detection device according to claim 4, further comprising a groove fixed with respect to said second body and directed in a third direction transverse with respect to said first and second directions, and a pin, fixed with respect to said crank and co-operating with said groove; and wherein said crank includes a first end and a second end arranged in an axial direction and constrained to said second electric motor and to said pin, respectively, and an intermediate portion arranged between said first and second ends; and wherein said first and second faces are formed by said intermediate portion and are transverse with respect to said axial direction.

6. The detection device according to claim 4, wherein said transducer comprises a first strain gauge and a second strain gauge, arranged on said first and second faces, respectively.

7. The detection device according to claim 1, wherein said constraint comprises a guide, fixed with respect to said first body and parallel to said first direction, and a slide, fixed with respect to said second body and constrained to move along said guide.

8. An intracortical-detection system comprising an intracortical-detection device according to claim 1 and a display device, electrically connected to said sensor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) For a better understanding of the invention, embodiments thereof are now described, purely by way of non-limiting example, with reference to the attached drawings, wherein:

(2) FIG. 1 shows a perspective view of an intracortical-detection system of a known type;

(3) FIG. 2 shows a perspective view of an intracortical-detection system according to the present invention;

(4) FIG. 3 shows a perspective view of a portion of the intracortical-detection system illustrated in FIG. 2;

(5) FIG. 4 shows an electrical diagram of a Wheatstone-bridge circuit;

(6) FIGS. 5, 6 and 7 show block diagrams regarding portions of the intracortical-detection system illustrated in FIG. 2;

(7) FIG. 8 is a perspective view of a variant of a crank of the intracortical-detection system illustrated in FIG. 2; and

(8) FIG. 9 shows qualitatively a distribution of the mechanical stresses along the crank illustrated in FIG. 8.

BEST MODE FOR CARRYING OUT THE INVENTION

(9) FIG. 2 shows an intracortical-detection system comprising an intracortical-detection device, referred to hereinafter as detection system 40 and detection device 41, respectively. The detection system 40 and the detection device 41 are described hereinafter, the present description being limited just to the differences with respect to the detection system 1 and to the detection device 2 described previously and illustrated in FIG. 1. Moreover, components of the detection system 40 already present in the detection system 1 described previously are designated in the same way, except where otherwise specified.

(10) In detail, the detection device 41 comprises a first strain gauge 42 and a second strain gauge 44 (illustrated in FIG. 3), of a type in itself known. In particular, each of the first and second strain gauges 42, 44 is a transducer that is able to vary its own electrical resistance as a function of a mechanical deformation to which it is subjected. Even more in particular, each of the first and second strain gauges 42, 44 can be formed, in a way in itself known, by a wire made of semiconductor material.

(11) As illustrated in greater detail in FIG. 3, the first and second strain gauges 42, 44 are arranged, respectively, on a first face 46 and a second face 48 of the crank 16 opposite to one another. In detail, the first and second faces 46, 48 are arranged parallel to the axis of rotation R and to the crank axis H, i.e., are parallel to the plane defined by this axis of rotation R and this crank axis H.

(12) Even though they are not illustrated, the first and second strain gauges 42, 44 are electrically connected to the electronic card, here designated by 45. Moreover, the electronic card 45 includes a first resistive element 52 and a second resistive element 54, which, as illustrated in FIG. 4, form, together with the first and second strain gauges 42, 44, a Wheatstone-bridge electrical circuit 55.

(13) In detail, the first and second strain gauges 42, 44 are connected in a first reading node n.sub.1, whilst the first and second resistive elements 52, 54 are connected in a second reading node n.sub.2. Moreover, the first strain gauge 42 and the first resistive element 52 are connected in a first biasing node n.sub.3, whilst the second strain gauge 44 and the second resistive element 54 are connected in a second biasing node n.sub.4.

(14) In greater detail, according to a possible embodiment, the first and second strain gauges 42, 44 are the same as one another and have a value of resistance at rest, i.e., in the absence of tensile or compressive forces, equal to R.sub.s. Moreover, the first and second resistive elements 52, 54 both have a value of resistance equal to R.sub.s.

(15) The electronic card 45 moreover includes a voltage generator 58, which is connected between the first and second biasing nodes n.sub.3, n.sub.4 in such a way as to impose a biasing voltage between them. Moreover, the electronic card 45 comprises a voltage detector 60, which is connected between the first and second reading nodes n.sub.1, n.sub.2 and is designed to determine a reading voltage, present between the first and second reading nodes n.sub.1, n.sub.2. In other words, the voltage detector 60 is designed to supply an electrical read signal, indicating the voltage present between the first and second reading nodes n.sub.1, n.sub.2.

(16) Operatively, the cerebral tissue exerts a pressure against the surface 30 of the contact element 14. Moreover, since the first and second bodies 3, 4 are mechanically coupled by means of the guide 22 and the slide 24, the first body 3 can move only in a direction parallel to the longitudinal axis L of the detection device 41; consequently, the pressure exerted by the cerebral tissue on the surface 30 is transmitted to the pin 26. As illustrated in FIG. 3, this means that the pin 26 is subject to a force F.sub.p, which causes a deformation of the crank 16, and hence of the first and second faces 46, 48.

(17) The deformation of the first and second faces 46, 48 causes a variation of the resistances of the first and second strain gauges 42, 44. In fact, we find that the resistance of one between the first and second strain gauges 42, 44 increases with respect to the value at rest, whereas the resistance of the other decreases. In particular, we find that one between the first and second strain gauges 42, 44 assumes a resistance equal to R.sub.s+R.sub.p, whereas the other assumes a resistance equal to R.sub.s−R.sub.p.

(18) The reading voltage present between the first and second reading nodes n.sub.1, n.sub.2 is proportional to the resistance R.sub.p, which depends linearly upon the force F.sub.p. The electrical read signal supplied by the voltage detector 60 hence indicates the pressure exerted by the cerebral tissue on the surface 30 of the contact element 14.

(19) As illustrated in FIG. 5, in a way in itself known, the electronic card 45 can supply the electrical read signal to the peripheral electronic unit, which is here and in FIG. 2 designated by 70.

(20) In particular, the peripheral electronic unit 70 includes a processing circuit 72, electrically connected to the voltage detector 60 and designed to determine the pressure exerted by the cerebral tissue on the surface 30 of the contact element 14, on the basis of the electrical read signal supplied by the voltage detector 60. In detail, the processing circuit 72 generates an electrical measurement signal, which represents the pressure exerted by the cerebral tissue on the surface 30 of the contact element 14. In other words, the Wheatstone-bridge electrical circuit 55, the voltage detector 60, and the processing circuit 72 form an electrical pressure sensor.

(21) The peripheral electronic unit 70 can thus supply to the control station P, to which it is connected, the electrical measurement signal, as determined by the processing circuit 72. In a way in itself known, the control station P includes a screen and is programmed to enable display on this screen of the values of the pressure exerted instant by instant by the cerebral tissue on the surface 30 of the contact element 14, as represented by the electrical measurement signal.

(22) Thanks to the detection system 40, the surgeon can continuously have available quantitative information regarding the pressure exerted by the cerebral tissue on the surface 30, and can hence govern with greater precision the second electric motor 10, in order to apply on the first portion of cerebral region an initial static pressure adequate to guarantee contact between the surface 30 and the cerebral tissue, thus countering the bulging without inducing ischaemias.

(23) Alternatively, as illustrated in FIG. 6, the electronic unit can itself include the processing circuit 72, once again connected to the voltage detector 60. In this case, the processing circuit 72 can be directly connected to the control station P.

(24) In order to enable also compensation of pulsations of the cerebral tissue, it is moreover possible to adopt the embodiment illustrated in FIG. 7. According to this embodiment, the electrical read signal supplied by the voltage detector 60 is used for controlling in closed loop the second electric motor 10, so that the position of the detection device 41, and in particular the position of the first body 3 with respect to the second body 4, adapts dynamically as a function of the instantaneous pressure exerted by the cerebral tissue on the surface 30.

(25) In detail, according to this embodiment, the detection system 40 includes a control unit 80, which is of an electronic type and is electrically connected to the voltage detector 60 and to the second electric motor 10. In particular, the control unit 80 is arranged between the voltage detector 60 and the second electric motor 10. Moreover, the control unit 80 can be formed within the electronic card 45 or else within the peripheral electronic unit 70.

(26) In greater detail, the control unit 80 governs the second electric motor 10 as a function of the electrical read signal generated by the voltage detector 60, i.e., as a function of the pressure exerted by the cerebral tissue on the surface 30.

(27) In particular, in a way in itself known, the control unit 80 is designed to implement a control of the second electric motor 10 of the so-called “proportional-integral-derivative” (PID) type, on the basis of the electrical read signal supplied by the voltage detector 60 and of an electrical reference signal, which can be set by the user. For example, the electrical reference signal can be such that, in the (hypothetical) absence of pulsations, the pressure exerted by the surface 30 is equal to an optimal static pressure for the purposes of containment of bulging.

(28) In other words, the voltage detector 60, the control unit 80, and the second electric motor 10 form a closed-loop control circuit of the second electric motor 10, since the electrical read signal supplied by the voltage detector 60 depends upon the position of the first body 3 with respect to the second body 4 and is hence affected by the operation of the second electric motor 10. Consequently, the second electric motor 10 is governed on the basis of a quantity (the reading voltage) that depends upon operation of the electric motor 10.

(29) Operatively, the closed-loop control circuit causes the second electric motor 10 to be governed in such a way as to keep the pressure exerted by the surface 30 on the cerebral tissue constant. Equivalently, the second electric motor 10 is governed so that the relative position of the array of electrodes 6 with respect to the cerebral tissue does not vary on account of pulsation of the cerebral tissue. In other words, the array of electrodes 6 moves, under the action of the second electric motor 10, together with the first body 3, in such a way as to follow the movements of the cerebral tissue due to pulsation. In this way, not only is the position of the electrodes within the cerebral tissue kept constant, but moreover rubbing of the electrodes against the cerebral tissue in which they are inserted is limited, with consequent reduction of the electrical noise caused by this rubbing.

(30) In order to increase the sensitivity of the first and second strain gauges 42, 44 with respect to the pressure exerted by the cerebral tissue on the surface 30, i.e., in order to increase the variation of resistance (R.sub.p) of the first and second strain gauges 42, 44 given the same force F.sub.p, it is moreover possible to adopt a crank of the type illustrated in FIG. 8, where it is designated by 90.

(31) In detail, the crank 90 is elongated along the crank axis H and is S-shaped. Moreover, the crank 90 includes a first peripheral portion 92 and a second peripheral portion 94, which are arranged on the crank axis H and function respectively as first and second ends of the crank 90; the first and second peripheral portions 92, 94 are respectively constrained to the second electric motor 10 and to the pin 26, the latter being also here fixed with respect to the crank 90.

(32) In greater detail, the first and second peripheral portions 92, 94 are connected by a first curved portion 96 and second curved portion 98, as well as by a plane portion 100, the latter being arranged between, and connected to, the first and second curved portions 96, 98. The first and second curved portions 96, 98 are moreover respectively connected, not only to the plane portion 100 but also to the first and second peripheral portions 92, 94.

(33) The first and second peripheral portions 92, 94 have circular shapes, the centres of which are aligned along an axis parallel to the crank axis H. Moreover, the first and second curved portions 96 and 98 are arranged parallel to the crank axis H, and on opposite sides. The plane portion 100 defines a first face 102 and a second face 104, both plane and parallel to one another, and on which the first and second strain gauges 42, 44 are respectively arranged. In particular, the first and second faces 102, 104 are arranged perpendicular to the crank axis H, and parallel to the axis of rotation R about which the crank 90 turns.

(34) Given the same force F.sub.p, the S-shaped crank 90 deforms more than the crank 16. Furthermore, the first and second faces 102, 104 are particularly subject to tensile/compressive stress following upon the action of the force F.sub.p. As a demonstration of this, FIG. 9 shows qualitatively the distribution of the mechanical stresses along the crank 90. Consequently, given the same force F.sub.p, the first and second strain gauges 42, 44 undergo a deformation greater than the case where they are constrained on the first face 46 and on the second face 48 of the crank 16. Consequently, the sensitivity of the electrical pressure sensor formed by the Wheatstone-bridge electrical circuit 55, by the voltage detector 60, and by the processing circuit 72 is increased.

(35) The advantages that the present detection device affords emerge clearly from the foregoing description.

(36) In particular, the present detection device makes it possible to provide the surgeon in real time with quantitative information on the pressure effectively exerted by the cerebral tissue on the surface 30 of the contact element 14, enabling him to regulate correctly the pressure exerted by the detection device 2 on the cerebral tissue.

(37) In addition, according to the embodiment illustrated in FIG. 7, the instantaneous pressure exerted by the surface 30 on the cerebral tissue is kept substantially constant, irrespective of the pulsations of the cerebral tissue, which are precisely compensated dynamically in an automatic way thanks to the closed-loop control of the second electric motor 10. This compensation is made independently of the positioning of the array of electrodes 6 and moreover enables limitation of the electrical noise due to the relative motion of the array of electrodes 6 with respect to the cerebral tissue in which it is immersed.

(38) Finally, it is evident that modifications and variations may be made to the present detection device, without thereby departing from the scope of the present invention.

(39) For instance, instead of the first and second strain gauges 42, 44, transducers of a different type may be used, such as for example piezo-capacitive or piezo-resistive pressure sensors set on the surface 30. In addition, the arrangements of the first and second strain gauges 42, 44 may be different from what has been illustrated.

(40) Likewise, variations may be made to the Wheatstone-bridge electrical circuit 55. For example, in a way in itself known, the electronic card 45 can control the voltage present on the second reading node n.sub.2 in order to prevent saturation of the Wheatstone-bridge electrical circuit 55 due to the inevitable differences between the resistances of the first and second strain gauges 42, 44 and of the first and second resistive elements 52, 54. For this reason, the electronic card 45 can include a digital-to-analog converter (not illustrated) designed to impose, in a way in itself known, the voltage on the second reading node n.sub.2.

(41) It is likewise possible for the first and second strain gauges 42, 44 to form a circuit of a type different from the Wheatstone-bridge electrical circuit 55.