METHOD AND PROBE FOR PREDICTING SPONTANEOUS PRETERM DELIVERY

Abstract

A cervix probe is equipped with a tactile sensor array and an ultrasound transducer and configured for simultaneous acquisition of stress data and ultrasound strain data for the same sector of the cervix. Acquired and recorded stress and strain data are transmitted to a data processor for calculating cervix elasticity and cervix length, followed by calculating a probability of spontaneous preterm delivery using a clinically validated predictive model.

Claims

1. A method for predicting spontaneous preterm delivery, the method comprising the steps of: a) providing a cervix probe with a head equipped with a plurality of tactile sensors and an ultrasound transducer, said head positioned at an angle to a probe shaft, thereby said probe is configured for an orthogonal contact with a cervix surface of a pregnant woman, b) inserting said cervix probe into a vagina to contact said cervix surface, c) applying cervix deformation with said cervix probe, while simultaneously acquiring cervix stress data using said tactile sensors and cervix strain data using said ultrasound transducer, d) calculating cervix elasticity and cervix length using said cervix stress data and said cervix strain data, and e) calculating probability of spontaneous preterm delivery using a predictive model having as inputs said cervix elasticity and said cervix length.

2. The method as in claim 1, wherein said steps (c) and (d) are conducted for more than one sector of said cervix.

3. The method as in claim 2, wherein said steps (c) and (d) are performed on four radial sectors of said cervix.

4. The method as in claim 1, wherein said steps (b) through (e) are performed on the same pregnant woman repeatedly beginning from about 22 weeks of pregnancy.

5. The method as in claim 1, wherein said step (d) further comprising calculating cervix length from ultrasound pulse time-of-flight from said cervix surface to an internal os surface of said cervix.

6. The method as in claim 1, wherein said step (e) further comprising calculating said cervix elasticity based on a finite element model simulation for a cervix.

7. The method as in claim 1, wherein said step (d) further comprising compiling of a cervix map with a set of sectors each showing said respective cervix elasticity and said cervix length.

8. The method as in claim 1, wherein in said step (e) said predictive model is derived using a clinical validation study.

9. A probe for predicting spontaneous preterm delivery, said probe comprising: a head equipped with a plurality of front-facing tactile sensors and a front-facing ultrasound transducer, said head positioned at an angle to a probe shaft, thereby said probe is configured for an orthogonal contact with a cervix surface, said plurality of tactile sensors forming together a tactile sensor array located over at least a portion of said head, said ultrasound transducer is positioned adjacent to said plurality of tactile sensors on said head, said tactile sensor array is configured to acquire stress data and said ultrasound transducer is configured to emit an ultrasound pulse and to acquire a scattered ultrasound waveform from said cervix during cervix deformation by said probe, a control unit operably connected to said tactile sensor array and said ultrasound transducer and configured for acquiring said stress data using said tactile sensors and said scattered ultrasound waveform using said ultrasound transducer, and a data processor operably connected to said control unit and configured for calculating cervix elasticity and cervix length using said stress data and said ultrasound waveforms, said data processor is further configured to calculate a probability of spontaneous preterm delivery.

10. The probe as in claim 9, wherein said head further comprises an elastic layer covering said tactile sensor array and said ultrasound transducer to allow reversible stress transmission therethrough and multiple disinfections of said probe.

11. The probe as in claim 9, wherein said ultrasound transducer is made using a piezoceramic composite material with a mylar film with a predetermined thickness as an acoustic matching layer.

12. The probe as in claim 9, wherein said ultrasound transducer has an elastic backing layer to allow attenuation of acoustic backscattering from a support base housing thereof.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0034] Subject matter is particularly pointed out and distinctly claimed in the concluding portion of the specification. The foregoing and other features of the present disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only several embodiments in accordance with the disclosure and are, therefore, not to be considered limiting of its scope, the disclosure will be described with additional specificity and detail through use of the accompanying drawings, in which:

[0035] FIG. 1 illustrates a cervix probe location during acquisition of stress and ultrasound strain data from cervix using cervix deformation along the black arrow;

[0036] FIG. 2 shows an embodiment of a probe for predicting spontaneous preterm delivery;

[0037] FIG. 3 shows a close-up cross-sectional view of a probe head with tactile and ultrasound transducers;

[0038] FIG. 4 presents a block-diagram of the probe of the present invention;

[0039] FIG. 5 shows a graph with ultrasound signals reflected from internal cervical os during cervix deformation by the probe (left panel) and stress-strain data (right panel) recorded for 32 y.o. woman at 25-week pregnancy;

[0040] FIG. 6 shows clinical data for cervix elasticity and length for 10 pregnant women and cervix map for subject No. 10;

[0041] FIG. 7 presents a data flow chart of a method for predicting spontaneous preterm delivery; and

[0042] FIG. 8 presents a block-diagram of the steps of the method for predicting spontaneous preterm delivery.

DETAILED DESCRIPTION OF THE INVENTION

[0043] The following description sets forth various examples along with specific details to provide a thorough understanding of claimed subject matter. It will be understood by those skilled in the art, however, that claimed subject matter may be practiced without one or more of the specific details disclosed herein. Further, in some circumstances, well-known methods, procedures, systems, components and/or circuits have not been described in detail in order to avoid unnecessarily obscuring claimed subject matter. In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and make part of this disclosure.

[0044] Specific terms are used in the following description, which are defined as follows:

[0045] tactile sensor is the sensor capable to measure an applied force averaged per sensor area or pressure;

[0046] ultrasound transducer is the sensor capable to emit and receive an acoustic wave;

[0047] stress is a force per unit of area (pressure) measured at surface of cervix;

[0048] strain is a soft tissue displacement under tissue deformation;

[0049] FIG. 1 illustrates a cervix probe 105 location during acquisition of stress and strain data from a cervix 107 at cervix deformation with the probe head 108 oriented along arrow 109. Shown in FIG. 1 is a sagittal cross-section of the pelvic floor of a pregnant woman with a fetus 101. The pelvic landmarks are a bladder 103, a vagina 104, a rectal canal 106 with anus 110. The probe head 108 may have a flat surface with tactile sensors and ultrasound transducers contacting the cervix 107 surface, either directly or through an elastic protective layer. The probe head 108 may be designed to have sensors in contact with the entire cervix or individual parts thereof. In other embodiments, the head 108 may include groups of sensors designed to contact individual sectors of cervix 107; such as 2 sectors, 3 sectors, 4 sectors, 5 sectors, 6 sectors, 7 sectors, 8 sectors, 9 sectors, 10 sectors, as the invention is not limited in this regard. The following description uses a four-sector exemplary approach for characterization of the cervix (upper, lower, and two lateral sectors of the cervix).

[0050] FIG. 1 further shows the probe head 108 paced in contact with the upper cervix sector. The size of the head 108 and location of the sensors may be arranged for the head to be used to characterize the entire cervix all at once, or alternatively for characterizing each desired sector or groups of adjacent sectors of the cervix at a time.

[0051] A front portion of probe head 108 containing sensors may be suitably shaped for contacting cervix surface generally perpendicular to the internal os surface 102 of the cervix 107. It allows acquisition of ultrasound reflected signal from the internal os 102 and measuring a time-of-flight for the ultrasound reflected signal. Taking into account the acoustic speed of about 1,540 m/s for soft human tissues, one may calculate the cervix length from internal os surface to the cervix surface contacting the probe head 108. Changes in the time-of-flight during the cervix compression or deformation by the probe head 108 may be used to provide strain data for the respective cervix sector or a group of sectors currently under investigation. A plurality of tactile sensors (from 1 to 16 sensors) may be used to form together a tactile array located over at least a portion of the probe head 108, which may be configured to record stress data from cervix surface during cervical tissue deformation by the front portion of the probe 105. The tactile sensor array may include 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16 suitable tactile sensors as the invention is not limited in this regard.

[0052] An ultrasound transducer may be located adjacent to the plurality of tactile sensors over the same front portion of the probe head 108. The tactile sensor array may be configured to acquire stress data in the form of pressure data on each tactile sensor while the ultrasound transducer may be configured to first emit an ultrasound pulse and then to acquire a scattered ultrasound waveform from soft tissues of the cervix including the internal os surface for the same sector of cervix. A control unit (not shown) may be operably connected to the tactile sensors array and to the ultrasound transducer. The control unit may further be configured for acquiring stress data from tactile sensors and a scattered ultrasound waveform data from the ultrasound transducer. A data processor (not shown) may be operably connected to the control unit and configured for calculating cervix elasticity and length from stress data and ultrasound waveforms.

[0053] FIG. 2 presents an exemplary embodiment of a probe 200 for predicting spontaneous preterm delivery. The probe 200 may comprise a handle 205, a shaft 204 and a head 203 with a flat surface configured for contacting cervix as shown in FIG.1. The probe 200 may contain a tactile array 202 with a plurality of sensors (four in this case) and at least one ultrasound transducer 201 as shown in FIG. 2. In one embodiment, the ultrasound 5.0 MHz transducer 201 measuring about 3.5 mm in size may be configured for working in the pulse-echo mode with data acquisition resolution of about 20 ns (50 MHz sample rate). Biocompatible, two-component silicone (such as for example made by NuSil Technology, CA) may be employed to provide sensor assembly with a functional, durable and stable mechanical protection cover. A proprietary printed circuit board of a control unit may be designed to perform the dual functions of stress signal acquisition and generation/acquisition of synchronized ultrasound signals. Its key features are to operate and acquire data from the plurality of tactile sensors 202 and the ultrasound transducer 201 at about 100 data frames per second. The stress measurement noise level in this example is about 25 Pa within the operational range of 40 kPa. The ultrasound transmitting pulses have a peak amplitude below 50 V and a length of less than 1 s, which provide acoustic power significantly below the limits established by the FDA for ultrasound emission in obstetrics: spatial-peak temporal-average I.sub.spta=94 (mW/cm2), spatial-peak pulse-average intensity I.sub.sppa=190 (W/cm2), and mechanical index MI=1.9.

[0054] Medical grade 316 stainless steel, used in production of surgical instruments, may be used to fabricate the probe shaft 204 while biocompatible plastic materials may be used for probe handle 205 and a head 203. The device software interface may be configured to allow real-time observation of the cervical ultrasound signal as well as the level of applied stress. The ultrasound peak position for cervix internal os signal may be calculated with the use of a signal envelope after the Gaussian complex wavelet filtering at 5 MHz frequency. The cervical elasticity may be calculated as a stress/strain ratio of applied load to the cervix surface from the probe (stress) to the resultant changes of the cervical length (strain). This approach was validated with the soft tissue models in bench testing and verification. Young's modulus was calculated from the stress-strain data based on a semi-infinitive linear elastic model and based on a finite element modeling of the cervix deformation with the probe 200.

[0055] The cervix examination procedure may comprise the following four main steps: [0056] (1) inserting the speculum into vagina to provide appropriate visualization and access to the cervix; [0057] (2) performing probe measurements at various portions of the cervix, such as for example at 3, 6, 9, and 12 o'clock, specifying the probe head location on the cervix surface and on a cervix map displayed to the user; [0058] (3) reviewing of the measurement results (ultrasound reflected waves and applied loads), and [0059] (4) removal of the probe and speculum from the vagina.

[0060] FIG. 3 presents an embodiment of a cervix probe with a head 300 equipped with tactile sensors 302 and 305 and an ultrasound transducer 304 for predicting spontaneous preterm delivery. The number of tactile sensors may be more than 2 as mentioned above. All tactile sensors may be positioned around the ultrasound transducer 304, which may be placed in a geometrical center of the plurality of tactile sensors of the array. A tactile sensor may be made as a capacitive type sensor although other force sensors may be used for the purposes of the invention.

[0061] The ultrasound transducer may be built from composite piezoceramic materials, for example 1-3 composites, and may be characterized by lower acoustic impedances (for example ranging from about 5 MRayl to about 30 MRayl), high coupling coefficients (typically about 0.6 to about 0.75), high bandwidth and lower mechanical quality factor (Qm). The ultrasound transducer 304 may be covered with an acoustic matching layer 303 on the front side and a backing layer 307 on the back side. The matching layer 303 may be preferably made using a mylar film of 0.09 mm thickness for 6 MHz. The thickness of the matching layer 303 was optimized experimentally for other frequencies by maximizing scattered signal amplitude and minimizing signal length. The backing layer 307 may be filled by silicone with attenuation of about 20 dB/mm at 6 MHz in a cavity with a depth of about 5 mm located behind the ultrasound transducer 304. Both tactile sensors 302, 305 and the ultrasound transducer 304 may be positioned on a support base 308 placed inside the probe body 309 with a central cavity 310 extending therethrough for housing electrical wiring of the sensors and the transducer. After positioning of the support base 308 with assembled sensors and transducer therein in the suitably sized front opening of the probe body 309, it may be secured therein by filling the spaces 301, 306 and 315 with a medical grade silicone having acoustic impedance of about 1 MRayl. The thickness of a surface layer 301 covering the tactile sensors 302, 305 may be about 0.4 mm. The silicone layer 303 covering the ultrasound transducer 304 may be about 0.3 mm thick. The probe head 316 may have a diameter of about 10-12 mm. The angle 313 between the probe central line in shaft 311 and central line 314 inside the probe head may be about 140 degrees. This allows positioning of the probe head orthogonally to the cervix surface and at the same time allowing for an easy insertion of the probe into vagina and removal therefrom after the test procedure is complete.

[0062] FIG. 4 presents a block-diagram of a system 400 for predicting spontaneous preterm delivery. A probe 401 comprises a plurality of tactile sensors 402 forming together a tactile sensor array located over at least a portion of the probe head. The probe 401 further comprises an ultrasound transducer 403 located adjacent to the plurality of tactile sensors on the same front surface. The tactile array 402 may be configured to acquire stress data and the ultrasound transducer 403 is configured to emit an ultrasound pulse and to acquire a scattered ultrasound waveform from soft tissues of cervix for the same sector of cervix. A control unit 404 may be operably connected to the tactile sensors 402 and the ultrasound transducer 403 and configured for acquiring the stress data from tactile sensors 402 and the scattered ultrasound waveform from ultrasound transducer 403. A data processor 405 is operably connected to the control unit 404 and configured for calculating cervix elasticity and length from stress data and ultrasound waveforms, which in turn may be used for calculating of probability of spontaneous preterm delivery.

[0063] FIG. 5 shows exemplary ultrasound signals 501-503 obtained from cervical tissue during cervix deformation by the probe (left panel) and a graph 506 of stress (pressure) versus strain (compression) data recorded for 32 y.o. woman at 25 week pregnancy (right panel). The recorded ultrasound signals 501-503 had an identifiable peak amplitude 504 reflected from the cervix's internal os, which may be used for a reproducible measurement of ultrasound time-of-flight and cervix length in mm as shown along the horizontal axis. The peak position was calculated with the use of a signal envelope lines (Gaussian complex wavelet filtering) as shown in the left panel of FIG. 5. Line 505 shows the translation of the peak position (cervix length) into stress-to-strain graph 506 on the right panel, which shows a graph of dependence of applied stress to the cervix in kPa from the cervix length during its deformation. Availability of stress-to-strain data allows calculation on the cervix elasticity.

EXAMPLE

[0064] FIG. 6 shows clinical results of measured cervix elasticity and length for 10 pregnant women and a cervix map 600. The cervix map 600 may have a number of sectors, in this case four sectors. The results for subject No. 10 (tissue elasticity and length distribution per four sectors) are shown in cervix map 600. Average values and standard deviations (up/down bars) for cervical elasticity and length for 10 cases were calculated based on two measurements per each of the 4 sectors (8 measurements per case); the values were 19.715.4 kPa, and the length was 30.76.6 mm. Subject No. 10 had an average cervix elasticity 59 kPa (see position 601) and cervix length 36 mm (see position 602). The average standard deviation for the 4 cervix sector measurements of elasticity was found to be 3.5 kPa and the length was 3.4 mm.

[0065] FIG. 7 presents a data flow chart of a novel method for predicting spontaneous preterm delivery. This method includes: [0066] a) acquisition of cervix stress and strain data for a plurality of cervix sectors, [0067] b) calculating cervix length by approximating the strain data to zero cervix deformation (see FIG. 5), [0068] c) calculating cervix elasticity using the cervix strain data and the cervix stress data, [0069] d) using the cervix length and cervix elasticity data from a cervix map 700 as inputs for a predictive model 701, and [0070] e) calculating the probability of spontaneous preterm delivery. The predictive model 701 may be composed using a statistical or neural network classifier based on results of a clinical validation study.

[0071] FIG. 8 presents a block diagram of a method for predicting spontaneous preterm delivery, comprising:

[0072] step 801 of providing a cervix probe equipped with a plurality of tactile sensors and an ultrasound transducer positioned adjacent thereto,

[0073] step 802 of inserting the cervix probe into a vagina along a vaginal canal to contact cervix surface of a pregnant woman,

[0074] step 803 of simultaneously recording/acquiring cervix stress data using the tactile sensors and ultrasound cervix strain data for the same sector of the cervix during cervical tissue deformations by the cervix probe,

[0075] step 804 of calculating cervix elasticity and length from the cervix stress and strain data, and

[0076] step 805 of calculating probability of spontaneous preterm delivery with the use of the cervix elasticity and length as inputs to a predictive model.

[0077] Additional method steps may include conducting this evaluation multiple times for a pregnant woman beginning from 24 weeks of pregnancy, measurement from four (4) cervix sectors (upper, lower, and lateral right and left), calculating cervix length from ultrasound pulse time-of-flight to internal os surface of the cervix, calculating cervix elasticity based on a finite element model simulation for cervix, comprising a cervix map with a set of sectors with cervix elasticity and length data per every sector, and comprising a predictive model derived from a clinical validation study.

[0078] Although the invention herein has been described with respect to particular embodiments, it is understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.