WO1995021581A1

WO1995021581A1 - The x-ray visible internal tissue replacement device

Info

Publication number: WO1995021581A1
Application number: PCT/CA1995/000050
Authority: WO
Inventors: Douglas Diethard Wing Wendler
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-02-08
Filing date: 1995-01-31
Publication date: 1995-08-17
Anticipated expiration: 1996-08-08
Also published as: CA2114927A1; AU1530395A

Abstract

An array of masses (B) composed of a compound which will block, diffract, deflect, or absorb X-rays, is to be placed in the layer of the encapsulating shell (A) of an internal articificial tissue replacement device which when bonbarded by X-ray radiation will be reproduced of an X-ray detecting medium.

Description

The X-RAY Visible Internal Tissue Replacement Device

Technical Field

This invention relates to the design of internal artificial tissue replacement devices and particularly to the placement of an X-ray identifiable array on the inner surface of the encapsulating shell of an internal artificial tissue replacement device.

Background Art

The need for an individual to introduce an artificial device into one's body can arise from the desire to improve one's appearance, or from circumstances beyond one's control. Accidental injury is a common source of circumstance which may require artificial tissue replacement. In the past decade the treatment of cancerous tissue has become a large source for the need of tissue replacement operations.

Cancer treatment can include the removal of tissue which contain cancer cells. The loss of tissue due to cancer treatment can be functionally and aesthetically displeasing. To overcome the loss of tissue, artificial devices may be placed internally to offset the effects of tissue loss. Once in place however, it is difficult to monitor the position within the body or the structural integrity of the device.

For example in cases of breast cancer, a mastectomy causes a noticeable loss of tissue. When it is desired to undergo reconstructive mammaplasty to replace to tissue lost from the mastectomy operation, it is common to use an artificial device to replace the tissue below the skin. Silicone gel filled implants are often used for this purpose. Saline filled and multi-chamber implants are examples of other devices also used in reconstructive mammaplasty.

The artificial devices in reconstructive mammaplasty are often filled with silicone gel, as silicone is generally thought to be biocompatible inside the human body. Once the implant is inside a person, it is difficult to monitor the integrity of the outer cross- linked silicone shell which encapsulates the implant. Rupture of this cross-linked silicone outer shell can enable the silicone gel contents of the implant to move freely through the body. The specific side effects of free silicone gel inside the body are unknown, and are still under study, but never the less this situation must be avoided if possible.

1 SUBSTITUTE SHEET prosthesis. MRI requires on average an hour to perform a complete examination. Purchase of MRI equipment for institutions is expensive, and highly trained staff are required to operate the machines. Currently there are over one million american women with an internal mammary prosthesis, and this figure is increasing due to the higher rate of female breast cancer. MRI is not a practical method to continuously monitor all of the women who have a mammary prosthesis. An intermediate system for diagnosing the status of an mammary prosthesis is required. One of the reasons that MRI is successful in monitoring the implant is that this method is able to isolate the silicone gel and display data relating to the presence of only silicone. A more conventional method would be to have a more identifiable material placed in an precise pattern on the surface of the encapsulating shell. If X-ray diffracting, absorbing, deflecting, diffracting, or blocking masses were to be placed in a precise pattern within the encapsulating shell of the implant, the implant would be viewable with a standard chest X-ray machine. These chest X-ray machines are accessible in health care institutions in metropolitan and rural locations. Chest X-ray machines and technicians are widely available, less expensive, and take less time to obtain data on a patient with implants.

With the assistance of computer imaging, the data from the X- ray can be used to construct a three dimensional representation of the implant, with possible ranges of the current shape of the outer cross linked shell. If the computer image is compared to data recorded from the initial installation of the implant the accuracy of a diagnoses can be enhanced.

There are some restrictions based on the condition of the patient and the shape and size of the artificial tissue replacement device which will have an effect of the accuracy of the information obtained on an individual. MRI provides a proven ability to diagnose silicone gel mammary prosthesis. The level of success obtainable by the array is unknown at this time, but information provided by the array is useful in that it can provide timely information about the structure of the implant.

Brief Description of the Drawings

Since the invention can undertake an amorphous shape, in order to illustrate the invention the drawings will describe an pear shaped implant placed on the chest of a patient outside the ribcage and below the skin tissue layer. The small end of the implant will be place closest to the head of the patent and will be labelled as the 90 "top" of the implant. The wide end of the implant will be placed closest to the feet of the patient and be labelled "bottom" for the orientation of the implant. The length of the pear will be oriented from top to bottom with the "front" being the surface farthest away from the ribcage of the patient, and the "back" being the surface closest to the 95 rib cage of the patient.

In the drawings which illustrate the embodiments of the invention, Figure 1 is the "front" view of an implant, Figure 2 is a "side" view of the implant across the "bottom" of an implant, Figure 3 is a "side" view from "top" to "bottom", and Figure 4 is a cross 00 sectional view along line 1 ,1 in Figure 1. Figures 5, 6, and 7 illustrate a different embodiment of the array.

The breast implant illustrated consists of a cross-linked silicone outer shell A which encapsulates the silicone gel contents C of the implant. The cross-linked silicone shell A can also be composed of 05 a different compound, but should have the properties to keep the silicone gel from leaking out, be biocompatible and have some flexibility to move with the body of the patient. Calcium spheres B are embedded in the cross-linked silicone outer shell A, and are placed over the entire cross-linked silicone shell A in the grid like array as 10 shown in figures 1 , 2, and 3. The calcium spheres B can be composed of other materials which block, diffract, or absorb X-rays.

The purpose of the calcium spheres B are that they, when bombarded by X-ray radiation, will individually show up on an X-ray detecting or sensitive medium. The fact that these calcium spheres 15 B will be displayed on the X-ray detecting medium will allow the outer shell of the breast implant to be evaluated for integrity. The resulting display of the calcium spheres B gives a physician more information about the integrity of the implant. When the implant is first put in place a chest X-ray shortly afterwards will result in a reference X-ray 20 of the intact implant which can be used as a reference point to compare future X-ray examinations. If for instance it is apparent that there is a calcium sphere B missing, or that there is more space between two adjacent calcium spheres B than there should be, than the physician can call for further tests to verify the presence of a 25 rupture in the outer shell A of the implant.

The calcium spheres B will show up white on an X-ray. The bones of the patient are also composed of calcium, but they tend to appear grey on an X-ray. Due to the different contrast between the bones of the patient an the calcium spheres B, the array can be

130 distinctly identified with some interference from the bones of the patient.

In figures 2 and 3 it can be shown that the "front" and "back" halves of the breast implant have the grid array of calcium spheres B offset by half of the distance between the calcium spheres B. In

135 figure 2 line 2,2 represents the line dividing the top and bottom sections of the implant. As it can be seen in figure 2 the array of calcium spheres B in the top section are offset from the array of calcium spheres B in the bottom section. Similarly in Figure 3 line 3,3 represents the division of the top and bottom sections along the side

140 of the implant.

Figure 4 is a cross section through line 1 ,1 of figure 1. The cross section illustrated by figure 4 shows that the calcium spheres B are contained within the cross-linked encapsulating shell A of the implant and do not come in direct contact with the silicone gel C of

145 the implant. Thus the loss of a calcium sphere B could be caused by exposure by a rupture on the outer surface of the shell surrounding the calcium sphere B, but not deep enough to continue through to the silicone gel C of the implant. If this situation occurs it is possible that the cross-linked encapsulating shell A could potentially rupture at this

150 point at a later time and the implant may need to be replaced before a rupture occurs as a preventative action. There are no calcium spheres B on the bottom section of the implant in figure 4 as they are offset and not in the plane of line 1 ,1 in figure 1.

Since figures 1 , 2 ,3, and 4 illustrate a pear shaped implant, the

155 implant should not flip from top to bottom once inside the patient. The pear shaped implant generally is also designed with a flat or shallow convex back side which will keep the implant in a consistent front, back orientation once inside the patient. This consistent orientation of the pear shape implant will have the same surface as the front at

160 all times and the same surface as the back at all times. By offsetting the array of calcium spheres B between the front and back grids it will make the resulting X-ray picture more valuable as the front and back arrays of calcium spheres B will be offset and not on top of each other. With implants which have a rounder shape it may not be

165 feasible to offset the front and back array of calcium spheres B as the orientation once inside can not be predicted, and the implant mav move around once inside due to the shape of the implant.

Figures 5, 6, and 7 illustrate how the array could be placed on a pancake shaped implant. Figure 5 represents the "front" surface of

170 the implant with D representing oval rather than round masses in a horizontal orientation. Figure 6 represents the "back" surface of the implant with E representing the oval masses in a vertical orientation.

Figure 7 represents the view taken of both arrays superimposed on one another. As it is represented in Figure 7 the "front" and "back"

175 arrays are individually visible due to the orientation and shape of each array. This can add more information as rotation of oval masses

D or E can be used as a factor to indicate possible rupture of the encapsulating envelope of the implant. The use of oval masses D or

E can have the disadvantage of causing a rupture by poking through

180 the surface of the implant where a fold or sharp curve in the encapsulating shell occurs.

Best Mode For Carrying Out The Invention

185 As noted earlier the X-ray blocking, diffracting, deflecting, or absorbing spheroid masses are depicted as being the calcium spheres B. Calcium is a good example of a material to be used in the array as it has all of the properties required of a material for this purpose. The properties of a material for use in the array are as 190 follows:

Biocompatible Biodegradable

Diffract, block, deflect, or absorb X-rays Non reactive to silicone gel or cross-linked shell 195 Non reactive during cross linking silicone process

Can be produced in specific size and shape Show up on an X-ray differently than the bones of the patient Heavy metals can be put into compounds which meet the above requirements, but may not be practical in the day to day operations 200 of the patient. Day to day examples such as airport metal detectors may discourage the use of heavy metals.

The disadvantages of the array in general are that if the patient has silicosis, or another lung condition which causes the lungs to show up as a white cloud, the array will not show through the cloud 205 around the lung area. In situations where a rupture causes the shell's surface to contract rather than expand, the calcium spheres B will move closer together, and it will be difficult to tell if the closeness of spheres is caused by a fold or a rupture. In some circumstances the calcium spheres B will interfere with other objects which need to be 210 viewed by a chest X-ray.

In current use are multiple chamber tissue replacement devices. These multi chamber devices are in use to better control the shape and size of an implant. The array may be placed within the chambers of the implant to monitor the position or integrity of these inner

215 chambers. As time continues and technology advances the complexities of the construction of internal artificial tissue replacement devices will increase. An attempt to include the unknown direction of the implant construction will be addressed in the claims following the conclusion of the description of the invention.

220 In summery, the above representation of the invention is attempting by means of words to describe an array of masses which will block, diffract, or absorb X-rays to be placed within the encapsulating layer of a tissue replacement device in such a manner as to be recorded on an X-ray recording media and that the resulting

225 picture or data recorded will provide a medical doctor with information which can assist in the diagnosis of the intactness of an the internal tissue replacement device.

Industrial Applicability:

230

This invention is designed to be integrated into the production of artificial tissue replacement devices. This invention could be used in artificial hearts, mammary prosthesis, and other such tissue replacement devices as they become available.

Claims

235 Claims:

1. The invention claimed is an array of X-ray blocking, diffracting, deflecting, or absorbing masses, to be placed within the surface layer of the encapsulating shell of an internal artificial tissue

240 replacement device, which when exposed to X-ray radiation will record on an X-ray detecting media the array of X-ray blocking, diffracting, deflecting, or absorbing masses in such a manner that the array of masses are mappable for the purpose providing information to assist in the determination of the integral status of the

245 encapsulating shell an internal tissue replacement device.

2. The array of X-ray blocking, diffracting, deflecting, or blocking masses as in claim 1 wherein the array is be placed within chambers or structures contained within the internal artificial tissue

250 replacement device for the additional purpose of monitoring positioning or integrity of the structures placed with in the internal artificial tissue replacement device.