LIEBSCHNER, Michael (3530 Chesapeak Ct, Pearland, TX, 77584, US)
CLAIMS
What is claimed is:
1. An apparatus for determining the structural integrity of a fluid-filled implant, the apparatus comprising: a mechanical component having a contact member; a transducer coupled to the mechanical component, the transducer configured to measure a property of the fluid-filled implant through the contact member; and an electrical component coupled to the mechanical component, the electrical component comprising a processor configured to determine whether the implant is defective using the measured implant property.
2. The apparatus of claim 1 wherein the processor is configured to compare the implant property to a baseline to determine whether the implant property is different from a predetermined value of the baseline, and indicate that the implant is defective in response to the determination that the implant property is different from the predetermined value of the baseline.
3. The apparatus of claim 1 wherein the processor is configured to compare the implant property to a baseline to determine whether the implant property is within a predetermined range of the baseline, and indicate that the implant is defective in response to the determination that the implant property is not within the predetermined range of the baseline. 4. The apparatus of claim 1 wherein the mechanical component includes a vibrometer coupled to the contact member, the vibrometer configured to apply a mechanical action to the contact member.
5. The apparatus of claim 4 wherein the implant property is a response to the mechanical action. 6. The apparatus of claim 5 wherein the implant property is at least one of acceleration, displacement, velocity, resonance frequency, accelerance, stiffness, compliance, mobility and impedance.
7. The apparatus of claim 2 wherein the baseline is adjustable to account for different implant types. 8. A self-contained module incorporating the apparatus of claim 1.
9. An apparatus comprising: a contact member configured to noninvasively engage an in vivo silicone gel-filled breast implant; a transducer coupled to the implant, the transducer configured to measure a response to a mechanical action applied through the contact member; and a processor in communication with the transducer, the processor configured to compare the response to a baseline to determine whether the response is different from a predetermined value of the baseline, and indicate that the implant is defective in response to the determination that the response is different from the predetermined value of the baseline. 10. The apparatus of claim 9 wherein the processor is configured to compare the response to a baseline to determine whether the response is within a predetermined range of the baseline, and indicate that the implant is defective according to the determination that the response is not within the predetermined range of the baseline.
11. The apparatus of claim 9 wherein the baseline is adjustable to account for different types of implants.
12. A method of determining the structural integrity of a fluid-filled implant, the method comprising: engaging a contact member with the implant; inducing a mechanical action in the contact member; measuring an implant property while inducing the mechanical action; and determining whether the implant is defective using the implant property.
13. The method of claim 12 further comprising: receiving a response from the implant due to the mechanical action; and determining the implant property from the response. 14. The method of claim 12 further comprising: comparing the implant property to a baseline; determining whether the implant property is different from a predetermined value of the baseline; and indicating that the implant is defective in response to the determination that the implant property is different from the predetermined value of the baseline.
15. The method of claim 12 further comprising: comparing the implant property to a baseline; determining whether the implant property is within a predetermined range of the baseline; and indicating that the implant is defective in response to the determination that the implant property is not within the predetermined range of the baseline.
16. The method of claim 12 further comprising: comparing the implant property to a baseline; calculating a percentage difference between the implant property and the baseline; determining whether the percentage difference is within a predetermined range; and indicating that the implant is defective in response to the determination that the percentage difference is not within the predetermined range.
17. The method of claim 14 further comprising: determining a severity of the implant defect based on the difference between the implant property and the baseline.
18. The method of claim 14 further comprising: determining a location of the implant defect based on the difference between the implant property and the baseline.
19. A method of noninvasively detecting whether an in vivo silicone gel-filled breast implant is defective, the method comprising: engaging the skin surrounding the implant with a contact member; inducing a mechanical action in the contact member; receiving a response from the implant through the contact member; determining an implant property from the response; and indicating whether the implant is defective using the implant property.
20. The method of claim 19 further comprising: comparing the implant property to a baseline; determining whether the implant property is different from a predetermined value of the ' baseline; and indicating that the implant is defective in response to the determination that the implant property is different from the predetermined value of the baseline. |
NONINVASIVE DIAGNOSTIC TOOL TO DETECT STRUCTURAL INTEGRITY
OF A FLUID-FILLED IMPLANT
BACKGROUND INFORMATION An estimated 1-2 million patients, or approximately 1% of the adult female population, have breast implants. Of the two main types of breast implant filler materials, silicone gel and saline fluid, many patients prefer silicone gel because it causes the breast implant to feel softer and more natural than a saline implant. However, rupture of a silicone gel-filled breast implant (SGBI) may cause certain risks to the patient. The risks of free silicone in the human body are widely debated, with research and studies on-going to determine these risks. It was previously thought that ruptured SGBI's were linked to serious medical conditions. Recent studies have not proved a cause-and-effect relationship between ruptured SGBI's and these serious medical conditions.
Aside from these unknown medical complications, a ruptured implant may cause other undesirable conditions. Some patients may notice decreased breast size, or a change in the shape or firmness of the breast. Patients may also notice hard knots, pain or tenderness, tingling, swelling, numbness, burning, or changes in sensation. A rupture may require a second operation and replacement of the leaking implant, thereby exposing the patient to possible complications from such operations.
However, these undesirable conditions only become a concern to the patient if the SGBI ruptures. Thus, it is important to understand whether SGBI's will rupture and when.
Recent research indicates that if the SGBI's are likely to rupture, they will do so in the first few years following surgery. Even in longer terms, the implants are expected to eventually wear out and release silicone into the surrounding breast tissue. As would be expected, the incidence of implant rupture increases over time. A recent study revealed that the median lifespan of a SGBI is 16.4 years. Goodman, CM., et al., The life span of silicone gel breast implants and a comparison of mammography, ultrasonography, and magnetic resonance imaging in detecting implant rupture: a meta-analysis, Ann. Plast. Surg., 1998, 41(6): pp. 577-85; discussion pp. 585-6. Another study reported failure of SGBI's to be 6% within the first five years following surgery, 30% at five years, 50% at ten years, and 70% at 17 years. Marotta, J.S., et al., Silicone gel breast implant failure and frequency of additional surgeries: analysis of 35 studies reporting examination of more than 8,000 explants, J. Biomed. Mater. Res., 1999, 48(3): pp. 354-64.
As can be seen, there is no reliable way to accurately predict SGBI life expectancy. Thus, it is very valuable to know the actual structural integrity of an implant while it is implanted, and to be able to determine if the implant is damaged or defective before an invasive operation is performed. Imaging systems represent the current state-of-the-art technology in SGBI in vivo evaluation. Such imaging systems include mammography, ultrasonography, X-rays, CT scans, and
magnetic resonance imaging (MRI). However, these imaging systems are lacking because they do not have sufficient sensitivity to accurately detect implant rupture. MRI, the most accurate imaging system for the evaluation of SGBI rupture, has a reasonably high sensitivity to extracapsular rupture (a rupture that has breached the scar capsule around the implant), but has an unacceptably low sensitivity to intracapsular rupture (scar capsule is still intact) due to the difficulty in imaging such a rupture. Ultrasonography provides some accuracy and is more available than MRI, but is highly operator dependent and has a steep learning curve. Mammography is inexpensive compared to the other imagining techniques mentioned above, and its findings may be specific if free silicone is present in the breast, but mammography has very low sensitivity. The limitations of the imaging techniques described above often mean that undesired surgical exploration is required to confirm the presence of implant rupture. And, as noted above, neither the rate of rupture nor its incidence can be reliably predicted. Therefore, there exists a need for more reliable in vivo diagnostic tools and testing to detect implant leakage at an early stage.
SUMMARY OF PREFERRED EMBODIMENTS Embodiments of the present invention are directed toward methods and apparatus for detecting the structural integrity of a fluid-filled implant, and, more specifically, a silicone gel-filled breast implant while it is implanted in the patient. A mechanical action or vibration is applied to the implant in vivo in a safe and noninvasive manner, and a response is measured and analyzed. The measured response may be compared to a predetermined baseline, and the comparison used to indicate the structural integrity of the implant. The severity and location of any rupture may also be indicated. The measured dynamic response, which is a direct mechanical measurement, may be used to more accurately determine the structural integrity of the implant than conventional imaging techniques.
BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a block diagram of one embodiment of an implant testing device; and
Figure 2 is an enlarged perspective view of an alternative embodiment of a portion of the implant testing device of Figure 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Certain terms are used throughout the following description and claims to refer to particular system features or components. This document does not intend to distinguish between features or components that differ in name but not function.
In the following discussion and in the claims, the terms "including" and "comprising" are used in an open-ended fashion, and thus should be interpreted to mean "including, but not limited to...". Also, the terms "couple," "couples," and "coupled" used to describe any connections are each intended to mean and refer to either an indirect or a direct electrical or mechanical connection. Thus,
for example, if a first device "couples" or is "coupled" to a second device, that interconnection may be through a conductor directly interconnecting the two devices, or through an indirect connection via other devices, conductors and connections.
The dynamic response of an object to a dynamic stimulus, being a direct mechanical measurement, is more directly related to the structural integrity of the object than the responses gathered from conventional imaging techniques. The dynamic stimulus, preferably a mechanical action, is created by a testing unit 100, illustrated in the block diagram of Fig. 1. Testing unit 100 includes an electrical component 102 and a mechanical component 140. Electrical component 102 may be a computer-based interface that provides power for testing unit 100, communicates with mechanical component 140, and performs data analysis on the dynamic response. Mechanical component 140 may be a portable testing interface responsible for both applying a dynamic mechanical stimulus to the implant and measuring the response of the object to the stimulus. Together, the mechanical and electrical components form a closed system that is capable of noninvasively testing the integrity of SGBI's. Although emphasis is placed on silicone gel-filled breast implants, the present invention is not limited to use with silicone implants and persons of ordinary skill in the art will appreciate that the presently described embodiments may be used with breast implants other than those specifically described herein. Furthermore, the present invention is not limited to a testing unit having separate mechanical and electrical components, and persons of ordinary skill in the art will appreciate that the present invention includes testing unit configurations other than those specifically described herein, such as a self-contained testing module or handheld diagnostic tool.
According to certain embodiments, electrical component 102 includes a dynamic signal generator 104, a data acquisition system 106 having a computer interface 108, and a dynamic frequency generator 110. Dynamic frequency generator 110 excites mechanical component 140 with constant amplitude pulses of a continuously variable driving frequency. Data acquisition system 106 further includes a processor 112 and memory 114. Memory 114 includes dedicated memory slots 116, 118, 120 and 122, which may include, among other things, computer programs or algorithms, implant property data and baseline value data.
The processor 112 may be any logic performing circuitry that can interface with an input signal, memory 114, and data output device 108. Memory 114 may be any type of storage media suitable for storing data 116, 118, 120 and 122, described more fully below. Persons of ordinary skill in the art are aware of several types of processors 112 and memory 114 that are suitable for the embodiments described herein.
According to certain embodiments, mechanical component 140 includes a vibrometer 142 and a mechanostatic core 144 for vibrational dampening. Vibrometer 142 includes a transducer
152, preferably a dual electromagnetic and piezo-electric driven transducer, an accelerometer 146 and a tip or contact member 150 for contacting an implant 200. Referring briefly to Figure 2, the tip 150 may have a dynamic load cell 148 mounted in it. Also, contact member 150 may be fitted with a terminal-testing tip or plate 154 to ensure a solid, stable mechanical interface between mechanical component 140 and the testing site. Persons of ordinary skill in the art are aware of several types of vibrometers 142, accelerometers 146 and contact members 150 that are suitable for the embodiments described herein.
The present invention is not limited to the specific mechanical and electrical devices described herein and persons of ordinary skill in the art will appreciate that the present invention includes mechanical and electrical devices and components other than those specifically described herein and capable of creating and analyzing the dynamic stimulus required for in vivo evaluation of implants.
In one embodiment, vibrometer 142 may be rigidly mounted to the applicator of a six degree-of-freedom robotic arm with an aluminum base plate adapter. The weight and size of the robotic arm ensures that the resonance frequency of the testing unit is in the upper end of the dynamic spectrum. The spatial control of the robotic arm also allows for accurate positioning of the testing tip or contact member with respect to the implant, and repeatable contact; pressure. between the testing tip and implant. However, as noted, vibrometer 142 may be applied to the implant via other configurations. Dynamic testing of implant 200 begins when contact member 150 is brought into contact with, or engaged with, implant 200 (or, the skin surrounding implant 200, in the case of in vivo evaluation). Next, a contact pressure is applied to the implant. For the contact pressure, a range between 10 and 20 Newtons is preferred, with 15 Newtons being specifically preferable. Dynamic frequency generator 110 excites mechanical component 140, and specifically vibrometer 142, with constant amplitude pulses of a continuously variable driving frequency. The electrical signal is then converted to a mechanical vibration, resulting in a dynamic stimulus or mechanical action. The mechanical action is applied within a frequency range, preferably between 20 and 1,000 Hz. A reaction or response force is generated, which excites the implant under test. Accelerometer 146 of mechanical component 140 measures the response force, or acceleration, at the point of contact between contact member 150 and implant 200. Both the input signal (dynamic force) and the output signal (acceleration) are measured at the point of contact between contact member 150 and implant 200 using an impedance head.
The present invention is not limited to the specific methods of applying forces or measuring signals described herein and persons of ordinary skill in the art will appreciate that the present invention includes methods and measurements other than those specifically described herein. For
example, the contact pressure and mechanical vibrations may be applied in different manners. The force and frequency ranges may be varied. Alternatively, the measured response to the input signal may be in terms of displacement or velocity rather than acceleration.
The response signals are relayed by mechanical component 140 to data acquisition system 106 of electrical component 102, where the signals are recorded in memory 114 as a recorded implant property 116. Furthermore, additional implant properties may be calculated, such as resonance frequencies (first and second), amplitude at resonance, half-power bandwidth, energy at half-power bandwidth and vibration coherence for a fixed bandwidth. Alternatively, more implant properties may be obtained, as will be explained below. A custom computer program or algorithm 118 may be used to perform a real-time data analysis on recorded implant property 116. First, algorithm 118 converts implant property 116 from the time domain into the frequency domain using Fourier Transformation. Frequency response functions may be applied to implant property 116 to account for fluctuations within the recorded signals. Implant property 116 may then be converted to a set of dynamic response, or transfer functions, including transfer function parameters such as accelerance, impedance, compliance and stiffness. These transfer function parameters are also implant properties shown as implant property 120 in Figure 1.
After implant properties 116, 120 are obtained, they may be compared to known values of undamaged implants of similar shape, size and type. Recorded signals such as acceleration, displacement, velocity or resonance frequency may be predetermined for any undamaged implant and later compared with implant property 116 of in vivo implant 200. Transfer function parameters such as accelerance, impedance, stiffness, mobility and compliance may also be predetermined for any undamaged implant and later compared with implant property 120. These predetermined values may also be called baseline values, and they are represented in Figure 1 as baseline 122. When the structural integrity of implant 200 is acceptable, baseline 122 is identical or substantially similar to the implant property it is being compared to. More detail regarding comparison of baseline 122 and implant properties 116, 120 is provided below. In one embodiment, baseline 122 may be created at the manufacturing facility where implant 200 is manufactured. In an alternative embodiment, baseline 122 may be created from empirical data developed from in vivo evaluation of implant 200. For example, during the first few months after implantation or at other times when implant 200 is known to have sound structural integrity, implant properties 116, 120 may be used to create a baseline 122. The present invention is not limited to the baseline creation methods described herein and persons of ordinary skill in the art will appreciate that the present invention includes baseline creation methods other than those specifically described herein.
Once created, baseline 122 is not necessarily fixed. Although it is within the scope of the present invention described herein that baseline 122 remains the same once created, it is also within the scope of the present invention that baseline 122 be adjustable based on implant properties 116, 120 observed over time. More specifically, baseline 122 may be adjusted based on trends observed through research in implant properties 116, 120. For example, it is conceivable that the implant manufacturer or another entity would discover certain indicators that appear before implant 200 ruptures or its structural integrity is otherwise compromised. It is therefore within the scope of the present invention that baseline 122 is updatable so that it may include these indicators. Persons of ordinary skill in the art are aware of other situations where it will be advantageous to update baseline 122. The present invention is not limited to the baseline update methods described herein and persons of ordinary skill in the art will appreciate that the present invention includes baseline update methods other than those specifically described herein.
In one embodiment, implant property 116 and/or implant property 120 is displayed on interface 108 along with baseline 122. If a difference in the values is shown, implant 200 is defective. Alternatively, interface 108 may simply indicate whether implant 200 is damaged or undamaged.
In another embodiment, a tolerance is built in to baseline 122. To account for such things as aging of the implant, surrounding soft tissue effects, temperature and other variables, baseline 122 may include a range of values which have been predetermined to reflect an undamaged implant. If implant property 116, 120 falls outside of this range, interface 108 may indicate that implant 200 is defective. Similarly, a percentage change in value between implant property 116, 120 and baseline 122 may be calculated and used to indicate the structural integrity of implant 200. For example, it may be determined that a 5% change in value between implant property 116, 120 and baseline 122 is acceptable (due to background noise), while a 30% change is not. In yet another embodiment, the comparison between implant property 116, 120 and baseline 122 may be used to indicate the severity of the damage to implant 200. The larger the difference between implant property 116, 120 and baseline 122, or the further implant property 116, 120 is outside the baseline 122 range, or the greater the percentage difference in values, the more severely implant 200 is damaged. A 700 micron puncture in implant 200 is detectable by the present invention, but may only be slightly outside the baseline range or may only indicate a 10% change in value from baseline 122. However, a lmm or 5mm long rupture is more severe, and will be indicated by an implant property value that is further outside the baseline range or a 30% change in value over baseline 122, for example.
The location of the implant rupture may also be indicated in a manner similar to the one just described with respect to rupture severity. An increased difference between implant property 116,
120 and baseline 122 generally indicates a rupture located close to the point of contact for contact member 150. The sensitivity of the present invention is such that rupture location will typically not have a major effect on the observed differences between implant property 116, 120 and baseline 122. For example, the location of a 700 micron rupture in implant 200 will not effect the detectability of the rupture, but may provide a slight difference in implant property 116, 120 such that comparison with baseline 122 will provide information as to the location of the rupture. Thus, by taking measurements at multiple locations, information regarding location of the rupture or defect may be gained.
While various preferred embodiments have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit and teachings herein. The embodiments herein are exemplary only, and are not limiting. Many variations and modifications of the systems and components disclosed herein are possible and within the scope of this teaching, with examples having been given herein. Accordingly, the scope of protection is not limited by the description set out above, but is defined by the claims which follow, that scope including all equivalents of the subject matter of the claims.