METHOD FOR DETERMINING THE MECHANICAL PROPERTIES OF A PELVIC CAVITY, AND MEASURING DEVICE

Abstract

The present invention provides a method (30) of determining mechanical properties of the pelvic cavity of a person or an animal, the pelvic cavity including a plurality of organs and the method comprising a step (34) during which pressure is measured at one or more points of the surface of one of the organs of said pelvic cavity, and during which, simultaneously, movements of a plurality of organs of said pelvic cavity are also measured.

The present invention also provides a measuring device for measuring pressure in an organ of the pelvic cavity in order to perform the above method (30). The measuring device comprises an optical fiber pressure sensor mounted in a non-metallic housing, and a closed flexible reservoir mounted in said non-metallic housing and having a surface, in particular a flexible surface, that constitutes a pressure measuring surface.

Claims

1. A method of determining mechanical properties of the pelvic cavity of a person or an animal, the pelvic cavity including a plurality of organs and the method comprising a step during which pressure is measured at one or more points of the surface of one of the organs of said pelvic cavity, and during which, simultaneously, movements of a plurality of organs of said pelvic cavity are also measured.

2. A method according to claim 1, wherein said organ on the surface of which pressure is measured is the vagina or the rectum.

3. A method according to claim 1, wherein the movements of said pelvic cavity are measured from data obtained by MRI of the person or of the animal.

4. A method according to claim 1, also including a step of constructing a digital model of the pelvic cavity from imaging data of the shape of the pelvic cavity.

5. A method according to the preceding claim 4, wherein construction of the digital model includes subdividing the digital model into finite elements.

6. A method according to claim 4, wherein the mechanical properties used in the digital model are modified in such a manner that the movements obtained with the digital model of said plurality of organs approach the movements as measured when the pressures at said one or more points of the surface of one of the organs of the digital model are equal to the measured pressures.

7. A method according to claim 4, also including, after modifying the mechanical properties of the digital model, a step of modifying the digital model in order to simulate possible mechanical behavior of the pelvic cavity of the person or of the animal.

8. A measuring device for measuring pressure in an organ of the pelvic cavity, the device comprising an optical fiber pressure sensor mounted in a non-metallic housing, and a closed flexible reservoir mounted in said non-metallic housing and having a surface, in particular a flexible surface, that constitutes a pressure measuring surface, the pressure measuring surface being configured to put into contact with a surface of the organ of the cavity and the flexible reservoir being configured to transmit pressure exerted on the measuring surface to the optical fiber sensor.

9. A measuring device according to claim 8, wherein the flexible reservoir is filled with a fluid or with a gel.

10. A measuring device according to claim 8, presenting a longitudinal direction, and wherein the pressure measuring surface is a substantially plane surface having its normal perpendicular to the longitudinal direction.

11. A device according to claim 8, wherein at least a portion of the optical fiber sensor is mounted in said flexible reservoir or else in contact with a surface of said flexible reservoir.

12. A measuring device according to claim 8, wherein the surface of the closed flexible reservoir is a flexible surface.

13. A method according to claim 3, wherein the movements of said pelvic cavity are measured from data obtained by dynamic MRI of the person or of the animal.

14. A method according to claim 4, wherein the step of constructing a digital model of the pelvic cavity from imaging data of the shape of the pelvic cavity comprises a step of constructing a digital model of the pelvic cavity from data obtained by static MRI of the person or of the animal.

15. A method according to claim 4, wherein the step of constructing a digital model of the pelvic cavity from imaging data of the shape of the pelvic cavity comprises a step of constructing a digital model of the pelvic cavity from data obtained by static MRI of the person or of the animal, and from standard mechanical properties.

16. A method according to claim 7, wherein the step of modifying the digital model comprises a step of modifying the shape of the digital model or modifying a mechanical property.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The invention and its advantages can be better understood on reading the following detailed description of a particular embodiment taken as a non-limiting example and shown in the accompanying drawings, in which:

[0035] FIGS. 1 and 2 are diagrammatic views of a measuring device of the invention; and

[0036] FIG. 3 is a flow chart of an implementation of the method of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0037] FIG. 1 is a diagram of a device 1 for measuring pressure in an organ of the pelvic cavity.

[0038] The measuring device 1 comprises in particular a body 2. The body 2 extends in a longitudinal direction and enables a mechanical connection to be obtained between a positioning handle 4 and pressure measuring means 6. The body 2 is rigid or semi-rigid for the purpose of transmitting mechanical forces exerted on the handle 4, and it is not metallic in order to be compatible with an MRI environment.

[0039] The positioning handle 4 is mounted in the longitudinal direction of the body 2 and enables a gynecologist to position and orient the pressure measuring means 6 easily while the device is in use. The positioning handle 4 may in particular be removably mounted, e.g. via a connector 8, at one of the ends of the body 2.

[0040] Finally, the device 1 includes the pressure measuring means 6 mounted on the body 2 in the longitudinal direction at its end remote from its end connected to the handle 4.

[0041] As shown in FIG. 2, the pressure measuring means 6 comprise a rigid non-metallic housing 10 defining an inside volume that is to receive a fluid or a liquid.

[0042] The non-metallic housing 10 also presents a through opening 12 in the longitudinal direction of the device 1 for inserting one or more optical fibers 14 including an end 14a that constitutes an optical fiber sensor that is positioned in the inside volume defined by the non-metallic housing 10. The non-metallic housing 10 also has a lateral opening 16, with its normal being substantially perpendicular to the longitudinal direction of the device 1 and serving to define the outline of a measuring surface 18.

[0043] By way of example, the optical fiber sensor 14a may operate by interferometry: an incident light wave is reflected by a dielectric mirror and constitutes a reference wave. The incident beam is also reflected by a diaphragm, i.e. a membrane that is deformable under the effect of an external pressure, and it interferes with the reference beam. The path-length wave difference between the reference beam and the beam reflected by the diaphragm then makes it possible to determine the deformation of the diaphragm, and indirectly to determine the pressure exerted thereon.

[0044] The inside volume defined by the non-metallic housing 10 is filled with a fluid or a gel 20 and the lateral opening 16 is covered by a flexible membrane 22 that forms, in the lateral opening 16, the measuring surface 18 of the pressure measuring means 6. The membrane 22 then has the function of deforming in order to transmit pressure to the optical fiber(s) via the fluid or gel present in the cavity, while guaranteeing that the inside volume is sealed. The fluid or the gel provided inside the housing 10 is substantially incompressible, so as to transmit the pressure variations applied to the measuring surface 18 to the end(s) 14a of the optical fiber(s) 14. The quantity of fluid in the inside volume of the non-metallic housing is constant and does not vary. The membrane 22 may be flexible and elastic, or it may be flexible and non-elastic. It thus becomes possible to measure along the axis of the longitudinal direction of the optical fiber(s) 14, i.e. in the longitudinal direction of the device 1, any variation in pressure that is exerted in a direction perpendicular to said longitudinal direction.

[0045] Specifically, the optical fibers serve to measure pressure at their distal ends 14a, and they cannot be bent given their brittle nature. The fluid or gel that is in contact both with the measuring surface 18 positioned on a lateral side of the measuring device 1 and with the end(s) of the optical fiber(s) 14 serves to transmit the pressure from the measuring surface 18 to the sensitive surface(s) of the optical fiber(s) 14. There is thus no need for the optical fiber(s) 14 to be curved, which might break them.

[0046] Furthermore, the presence of fluid or gel inside the housing 10 also makes it easy to identify and locate the measuring means 6 in MRI images. This enables the local pressure field measured by the device 1 to be characterized accurately.

[0047] The measuring means 6 may present the following characteristics: sensitivity of 0.2 millimeters of mercury (mmHg), an optical fiber having a length of 10 meters (m) in order to connect the measuring means 6 to the data acquisition computer, a size less than or equal to 15 millimeters (mm), and a data acquisition frequency greater than or equal to 10 hertz (Hz).

[0048] The measuring means 6 are thus completely compatible with an MRI environment. Specifically, firstly the signals transmitted by the optical fiber are not disturbed in any way by the magnetic field or by the radiofrequency waves generated by the MRI during conventional observation sequences of pelvic pathologies, and secondly the presence of the measuring means 6 does not give rise to any artifacts in the images that need to be observed for diagnostic purposes and for making measurements associated with movements.

[0049] The device 1 shown in FIGS. 1 and 2 has only one measuring surface 18. Nevertheless, it is also possible to envisage providing a measuring device with a plurality of pressure measuring means 6 arranged along the longitudinal direction of the body, or indeed a housing 10 with a plurality of measuring surfaces 18 arranged around the periphery of the housing 10 so as to provide a device with a plurality of measuring zones. Under such circumstances, each measuring surface 18 should be associated with a respective reservoir of fluid or gel and with one or more optical fibers, and the device can then be used to acquire a plurality of pressure values simultaneously.

[0050] The non-metallic housing 10 may be made of hard plastic, e.g. of acrylonitrile butadiene styrene (ABS). The optical fiber(s) is/are then inserted into the non-metallic housing 10. A flexible membrane 22, e.g. made of silicone, is positioned to close the inside volume of the non-metallic housing 10, and the housing is then filled with an aqueous echographic gel by means of a syringe.

[0051] In order to limit discomfort for the patient while the device is in use and in order to ensure that it is sealed, the body 2 and the pressure measuring means 6 may in particular be covered in a flexible membrane 24, e.g. made of silicone.

[0052] Furthermore, in order to enable suitable measurements to be made of intra-vaginal or intra-rectal pressure, the measuring device 1 is designed to have a shape that guarantees contact between the measuring surface 18 of the measuring means 6 with the wall of the cavity, and also low stress against said cavity. This avoids excessively deforming the cavity, which could modify how the results should be interpreted.

[0053] A device 1 is thus obtained that can easily be observed in an MRI environment, and that provides measurements that are not disturbed by said MRI environment.

[0054] FIG. 3 shows the various steps of the method 30 of determining mechanical properties of a person's pelvic cavity, in particular in non-destructive and in in vivo manner. In a first step 32, a three-dimensional digital model is constructed of the person's pelvic cavity, e.g. using images obtained by static MRI. The digital model may also be made by being subdivided into finite elements in order to make possible the resetting as described below.

[0055] In a step 34, measurements are performed simultaneously both of pressure at a plurality of points on the surface of one of the organs and also of movements of a plurality of organs. Pressure measurement may be performed with a device 1 as described with reference to FIGS. 1 and 2, while the movements of organs may be measured by dynamic MRI imaging.

[0056] Finally, in a step 36, the mechanical properties of the digital model constructed in step 32 are modified so that these movements obtained by the digital model correspond to the movements measured during the step 34. Such a modification of the digital model may be performed in particular by simulation, using a digital model subdivided into finite elements, simulating the movements obtained for a given pressure field, and by comparing them with the movements as measured during the step 34: the finite element digital model is then reset in order to minimize differences between the two types of movement values.

[0057] By means of this method, it is thus possible to obtain a digital model of the patient that combines firstly the three-dimensional shape of the patient and secondly mechanical properties that are specific to the patient.

[0058] A last step 38 may then be performed using the resulting digital model. During the step 38, the digital model is modified either in terms of its three-dimensional shape or in terms of its mechanical properties, so as to simulate possible behavior of the patient's pelvic cavity.

[0059] Such a step can thus serve to improve diagnosis of pelvic pathologies, e.g. by identifying pathological zones having mechanical properties that are abnormally low or abnormally high, as applies for a prolapse, endometriosis, or a tumor. Likewise, it is also possible to improve therapy of pelvic pathologies by proposing strategies that are better adapted and by making it possible to take account of the specific features of each patient, such as for example simulating various surgical operations and proposing the operation the patient finds most appropriate, or indeed tailoring prostheses to have shapes and mechanical properties that are specifically adapted to the patient. Finally, it is also possible in preventative manner to determine features specific to a woman several months before childbirth and thus to determine complications better and in the much longer term.

[0060] Thus, by means of a local measurement of pressure and an overall measurement of movements, which measurements are performed simultaneously, it becomes possible to construct a digital model of a patient's pelvic cavity, which model is representative and reliable. Thereafter, such a model presents the advantage of being able to identify or simulate various abnormalities or complications that might arise with the patient, in order to adapt the procedures or operations that are to be undertaken.