US3731669A

US3731669A - External implantation of energy to power internal devices

Info

Publication number: US3731669A
Application number: US00081432A
Authority: US
Inventors: J Fitzgerald
Original assignee: SANDER NUCLEAR CORP
Current assignee: CAMBRIDGE NUCLEAR Corp
Priority date: 1970-10-16
Filing date: 1970-10-16
Publication date: 1973-05-08
Anticipated expiration: 1990-05-08

Abstract

A means and method is used to permit injection and/or extraction of radioisotopic energy source material to or from an energy source implanted in the body. Radioisotope injections are used to maintain energy sources for prosthetic organs and the like at desired energy outputs over long time periods thereby permitting minimization in size of implanted energy sources and maximization of economy. Preferably the radioisotopic material is thulium 171 in the form of microspheres.

Description

O United States Patent 1191 1111 3,731,669 Fitzgerald May 8, 1973 s41 EXTERNAL IMPLANTATION 0F 2,893,936 7/1959 Hatch e181. ..176/14 ENERGY TO POWER INTERNAL 132g l arvey u H n V 3,536,423 10/1970 Robinson i751 "TnVEnmr: Joseph J. Fitzgerald, Winchester, 3,563,028 2/1911 Goranson m1. ..3/1 x Mass. Primary Examiner-Dalton L. Truluck [73] Assignee. Sanders Nuclear Corporation, Nash- Attorney Louis Etlinger ua,N.H [22] Filed: 0ct.'16, 1970 ABSTRACT 2 1 ;g1 432 A means and method is used to permit injection and/or extraction of radioisotopic energy source material to or from an energy source implanted in the [52] U.S.Cl ..l28/1 R, 128/1.1, 128/260, body Radioisotope injections are used to maintain 176/14 energy sources for prosthetic organs and the like at [5 Int- Cl. desired energy outputs over long periods thereby [58] Field of Search ..-...l28/1 R, 1.1, 1.2, ermitting minimization in size of implanted energy 128/2 419 419 1310- sources and maximization of economy. Preferably the 2; 176/14 radioisotopic material is thulium 171 in the form of microspheres. [56] References Cited 15 Claims, 6 Drawing Figures PATENTEU 81975 3,731,669

SHEET 1 BF 2 FIGSA FIGBB INVENTOR JOSEPH J. FITZGERALD AT TORNEY PATENTEBHAY' 81975 sum 2 OF 2 3,731,669

NEW METHOD -0LD METHOD TIME, YEARS INVENTOI? JOSEPH J. FITZGERALD BY i W A TTORNEY EXTERNAL IMPLANTATION OF ENERGY TO POWER INTERNAL DEVICES BACKGROUND OF THE INVENTION used pacemakers are often powered by chemical means.

Some recently developed pacemakers employ radioisotopes as do some recently developed heart replacement engines. The use of radioisotopic energy sources for prosthetic organs involves a problem of useful life. Thus, radioisotopic materials decay over varying time periods depending upon the particular radioisotopic source half life period. Thus, if an energy source must have a power output of for example thermal watts and a useful life of 5 years, it would be necessary in the case of Tm-l71 to implant radioisotopic source material in the amount of 125 thermal watts at the beginning of life to have 20 watts at the end of 5 years. This half life problem increases cost of radioisotopic energy sources and further increases weight and size requirements as well as the heat dissipation and dose rate problems which can be a significant consideration when implanting prosthetic organs in thefbody. Moreover, because of the decay factor, it may be necessary to surgically remove the prosthetic organs from time to time to reinsert new prosthetic organs or at least the energy source materials in the same body with attendant complications. Thus, there is a need for low cost, lightweight, low dose rate and relatively long half life or long useful life radioisotopic energy sources to power prosthetic organs.

It is an object of this invention to provide a means and method of introducing and/or supplementing energy in an energy source and/or cavity for an energy source positioned in the body without the use of surgical procedures.

Another object of this invention is to provide means and method in accordance with the preceding object wherein the energy source comprises a radioisotopic material.

Still another object of this invention is to provide a means and method in accordance with the preceding objects which extends the useful life of relatively short half life radioisotopes.

Another object of this invention is to provide a means and method in accordance with the preceding objects which is low in cost and provides great flexibility to increase or decrease total power available from the source.

Still another object of this invention is to provide a means and method in accordance with the preceding objects which permits small size, light weight and low shielding parameters to be used.

SUMMARY OF THE INVENTION According to the invention, a power or energy source for use in the body has a means defining a chamber for carrying a radioisotopic material. Conduit means define a conduit interconnected with the chamber and the conduit has an end constructed and arranged to be positioned under the skin of the body so that radioisotopic material can be introduced into the chamber or withdrawn therefrom through the conduit means. The conduit means carries radiation shielding and is positioned to shield against radiation streaming paths from the chamber.

According to the method of this invention, power is provided to a power user implanted in the body by implanting a radioisotopic power source in the body in operative relationship with the power user. Radioisotopic material is periodically injected into the power source at predetermined timed intervals to maintain the power output of the source above a predetermined level.

The radioisotopic materials can be injected into the body in the form of dry microspheres preferably having a size of from 1 to 1,000 microns in diameter. The radioisotope materials may be coated with containment material to reduce the possibility of contamination. Alternatively, the radioisotopic materials can be in liquid form.

It is a feature of this invention that the useful life of relatively short half life radioisotopes can be extended by periodic injections. Cost of a heat source for powering a prosthetic organ can be reduced by this method. Flexibility is provided to increase or decrease the total power available to the prosthetic organ without the use of surgery. Other features include substantial reductions in weight, size and shielding requirements of energy sources. Since energy in the form of heat output can be predetermined, heat dissipation problems can be avoided or substantially decreased by the use of smaller size radioisotopic sources as required which are supplemented from time to time.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, advantages and features of the present invention will be better understood from the following specification when read in conjunction with the accompanying drawings in which:

FIG. 1 is a semidiagrammatic showing of a preferred energy source system in accordance with a preferred embodiment of this invention;

FIG. 2 is a cross sectional view through the center of an alternate embodiment of an element thereof;

FIG. 3A and 3B are semidiagrammatic showings of an alternate embodiment of the invention;

FIG. 4 is a semidiagrammatic showing of another alternate embodiment thereof; and

FIG. 5 is a graph indicating usefulness of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS With reference now to the drawings, a prosthetic organ system is illustrated generally at 10 in FIG. 1 and comprises an energy source 11, a prosthetic device 11A, a conduit 12, and interconnecting passageway 13 and a self-sealing membrane 14 implanted under the skin 15 of a body. The system can be used with any prosthetic device requiring a source of heat energy. The system 10 is surgically implanted in the body preferably with the conduit 12 having an end at or near the skin 15 so as to be accessible to a conventional hypodermic syringe 16.

The heat source 11 can be a container of any desired shape and design in accordance with known practice and in the preferred embodiment, is a rectangular chamber having suitable radiation shielding (not shown). The heat source 11 along with conduit 12 and the interconnecting passageway 13 are preferably mounted in the body in the position shown when the body is upright as in a standing human being. Radioisotopic material 17 can be initially charged to the heat source before surgical implantation to provide a desired thermal output to the user prosthetic device 11A which can be, for example, a heart pacemaker. The interconnecting passageway 13 is shieldedas known in the art and can be of various designs or configurations but preferably provides a tortuous path so that once the radioisotopic material is in the energy source 11, it will ordinarily stay within the source 11 and not pass upwardly through the passage 13 during normal body activities.

The interconnecting passageway 13 connects the needle passage conduit 12 with the energy source 11. The needle passage conduit 12 has a tubular shield 12A as of lead or other suitable shielding material toact as radiation shielding with a first self-sealing fluid impermeable membrane 20 at one end thereof and a second self-sealing fluid impermeable membrane as of silicon rubber 21 at a second end thereof. Thus, the conduit 12 is isolated from fluid flow. Preferably the proximal or outer end of the conduit 12 is funnelshaped as shown at 22 to act as a hypodermic needle guide in use. The conduit 12 is preferably an elongated right cylinder having its elongated axis arranged at a suitable angle to all portions of the energy source 11 so that no radiation streaming paths, which run in straight line directions from the radioisotopic material 17, are available for passage of the radioisotopic energy out through the conduit and thus effectively sealing the energy source against radiation loss.

The energy source 11 can be supplemented with radioisotopic energy by injection as by the use of a conventional hypodermic syringe 16. The needle of the hypodermic syringe is passed through the skin 15 and a fluid, gaseous, liquid or any flowable material 17 is introduced as shown in the drawing through the conduit 12 to the interconnecting passageway 13 where it drops to the energy source to supplement the radioisotopic material in the body energy source 111. The tip of the needle is preferably passed through both self-

sealing membranes

21 and 20. Thus, the energy output of the source 11 can be supplemented at predetermined times as desired by mere injection rather than surgical removal and replacement of the energy source.

The use of end seals formed by self-

sealing membranes

20 and 21 is particularly useful since it enables ease of decontamination of the conduit 32. Thus, when a single needle syringe such as 16 is used, after introduction of the radioisotopic material, the needle can be withdrawn and a second syringe carrying a flushing material such as alcohol can be inserted with its tip within the bounds of the conduit 12 defined by the

end seals

20 and 21. The flushing material can irrigate to conduit 12 and then be aspirated to remove any radioisotopic material which may have contaminated the chamber 12.

The radioactive material useful in the syringe or injection method of implantation must be flowable. It has been found that microspheres, having diameters of from 1 to 1,000 microns, of radioisotopic materials are flowable through small gauge needles such as conventional 16- to 26-gauge stainless steel hypodermic needles. Thus, when microspheres of thulium oxide having particle or diameter sizes of from 1 to 1,000 microns are used, they can be pumped through the syringe without the use of lubricants, solvents or suspending agents. Microspheres are conventionally made by adding fine powders of thulium oxide for example to a plasma arc area where the powder are vaporized into liquid form with the liquids later reformed into solids and the liquid surface tension acting to form microspheres.

In some cases, small particle size or microspheres of the radioisotopic material can be suspended in slurries or solvents to form liquid injectable mixtures. For example, slurries of thulium oxide microspheres suspended in alcohol can be used.

When slurries or solvent solutions are used, the seals or

membranes

20 and 21 can be diffusible membranes permitting diffusion of the solvent or suspending agents such as alcohol through the membranes in gaseous form to leave behind only the radioisotopic particles.

Another method of cleansing the conduit 12 and preventing contamination comprises the use of a double walled needle or an outer needle arrangement as shown in FIG. 3A. In this embodiment of the method, a 2l-gauge needle 30 may for example be used in conjunction with a surrounding l6-gauge needle 31. The l6-gauge needle 31 is inserted into a conduit 12' and therethrough short of seal 20 as shown in FIG. 3A, after which the syringe 16' with needle 30 is used with the needle of the syringe 16 passing beyond the end of the surrounding needle 31 and beyond seal 20. The needle 30, after filling, is then withdrawn through the surrounding needle which is later removed. Flushing of the chamber 12' can be accomplished by the use of needle 31 while the surrounding needle 31 is still within the chamber 12' with its tip therein by use of a sonic probe 32 or other agitating instruments. (See FIG. 3B). The potentially contaminated needle 31 will not be removed until the liquid in chamber 12 is extracted with another smaller needle. Clean fluid can be added to chamber 12' as required and flushed by sonic probing or other method until the final solution is clean. Then the decontaminated needle 31 can be removed without contaminating the body.

In still another embodiment of this invention as illustrated in FIG. 2, the conduit is nonlinear or irregularly shaped as shown at 23. A syringe of conventional design but having a flexible plastic needle can be introduced through the nonlinear passageway 23. The use of the nonlinear passageway 23 further assures the absence of free streaming paths which would allow streaming of energy particles such as beta or gamma rays from the energy source 11 or any portion of the interconnecting passageway 13.

Other modifications of the invention include direct positioning of the conduit adjacent the energy source 11. The use of a suitable angled conduit is employed to prevent free streaming radiation paths.

A hypodermic needle can be used only to introduce additional radioisotopic material to the energy source but also to remove spent or partially decayed radioisotopic materials originally introduced into the energy source. For example, by suitable manipulation of the body, or the use of an elongated flexible needle on a syringe such as 16, the spent materials can be aspirated from the chamber of the source 11 and removed after which fresh radioisotopic material of predetermined energy output can be introduced. In some cases where it is desired to reduce energy output, some of the radioisotopic material which is still active can be aspirated.

In still another embodiment of this invention as diagrammatically shown in FIG. 4, each unit comprises at least two energy source portions 11" with accompanying interconnecting passageways 13" and conduits 12" as previously described. Thus, upon original surgical implantation, only one energy source 11" carries radioisotopic material. Subsequently at a predetermined time when the heat output falls below a desired value, the conduit 12" of the second energy source can be used to introduce additional radioisotopic material to a second source without interrupting the power supply. Simultaneously or subsequently the spent or decayed radioisotopic material originally introduced into the body can be aspirated.

In a specific example illustrating the advantages of the present invention, a thulium 171 energy source of 30 watts output at the beginning of life is used. The decay rate and injection time period necessary to maintain 30 watts at each years end is indicated by the Table shown in FIG. 5. With respect to FIG. 5, thulium 171 decays at a rate of 9.2 thermal watts per year for a 30 thermal watt original input at 0 years as shown by the solid curve between 0 and first year. At the end of the first year, Tm-17l material corresponding to 9.2 watts is injected into the energy source to increase the power level back to 30 watts as shown by the vertical line at the end of the first year. Same processes repeat each year until the end of useful life. Then the power level will decrease continuously as shown by the solid curve after 3 years. Therefore, 9.2 watts per year of thulium 171 in the form of thulium oxide microspheres are injected at yearly intervals to keep the power level at 30 thermal watts at each years end. Thus according to this method, 9.2 watts per year for each year of a 4 year operation is used or 3 X 9.2. 27.6 thermal watts ending up with 20.8 watts at the end of 4 years. If the old method of utilizing a large single mass of thulium! 171 were used which mass would have to maintain a desired watt output over the 4 year period, 60 watts of material would be used originally with 46 watts used up over the 4 year period ending up with approximately 14 watts as shown by the dotted curve in FIG. 5. Thus, the injection method utilizes not only less activity originally, costs less but also ends up with more activity. In the instance cited above, the user can continue on for 1.2 years after the end of the 4 year period discussed before the 20.8 watts drops to 14 watts comparable to the 14 watts present at the end of the old method used.

In the known methods of surgical implantation of a mass of radioisotopic material which would not be changed or supplemented, a much larger quantity of radioactivity was required for insertion thus requiring large volume and large shielding. The initial quantity of radioactivity required for a given use 18 reduced by at least a factor of 2 in the case of thulium 171 and other isotopes such as Pm 147. For thulium 171 in the old method, an initial loading of 300 grams (60 thermal watts X 5 grams per watt) is required for a certain thermal output over a certain time period and occupies a volumefof approximately 40 cc. for an equivalent thermal output. The shielding requirements are reduced by a factor of 2 or a half value thickness. In the case of thulium 171, the shielding thickness would be 0.6 cm of lead or 0.4 cm of uranium less than the original shielding thickness. The above half valve thicknesses are based on the thulium 170 component in thulium 171. A comparison of the reduction in weight and shielding between the two methods is shown in the Table 1 below for constant dose rate at the surface of a unit designed for a needed power output of 30 thermal watts from thulium 171.

TABLE 1 Old Method Method of this Invention Source wt. 300 grams Source wt. grams Shielding 1356 grams Shielding 255 grams Total wt. 1656 grams Total wt. 405 grams Spherical Spherical source source radioisotopic radioisotopic material material diameter 2.1 cm diameter 1.7 cm

The following Table 2 indicates the economic advantages of using the systems and method of this invention with various radioisotopic materials:

1000 Based on injection period equivalent to half life of the radioisotopic material Based on an injection period of one year. No injection required. Based on the initial use of 30 watts.

While specific systems and methods have been shown and described, it should be understood that many variations thereof are possible. For example, the specific sizes and shapes of the various elements can vary greatly depending upon the particular radioisotopic materials used and the particular power requirements necessary as will be obviousto one skilled in the art. In some cases, the power sources 11 can themselves have integral self-sealing passageways for introduction of hypodermic needles as required. Any flowable material can be used in conjunction with a self-sealing membrane to carry out the purposes of the present invention. In some cases, suitable biological shielding can be used over the syringe of the hypodermic needles used if necessary in a particular application.

What is claimed is:

l. A method of supplementing energy in an energy source positioned in the body of a user of said energy source wherein said energy source comprises a material whose energy is dissipated over a predetermined time period, said method comprising,

determining the rate of energy dissipation of said material,

surgically implanting said energy source in the body,

and physically injecting additional energy source material into said energy source through the surface of the skin into a self-sealing means within the energy source at predetermined timed intervals. 2. A method of providing power to a power source implanted in the body, said method comprising,

periodically injecting radioisotopic material in flowable form through body tissue into a self-sealing conduit means in said power source without removing said power source, said injections taking place at predetermined timed intervals to maintain the power output of said source above a predetermined level. 3. A method in accordance with the method of claim 2 wherein said radioisotopic material is injected by means of a hypodermic-type needle.

4. A method in accordance with the method of claim 3 wherein said needle is passed through the skin of the body and thence through an elongated conduit having self-sealing membranes at ends thereof.

5. A method in accordance with the method of claim 4 wherein said needle is withdrawn after said injection and said conduit is flushed to irrigate and decontaminate said conduit and tip of outer needle.

6. A method in accordance with the method of claim 4 wherein said conduit is straight and is positioned to prevent radiation streaming paths from said energy source.

7. A method in accordance with the method of claim 5 wherein said conduit is tortuous and said needle is flexible so as to pass easily through said tortuous conduit.

8. A method in accordance with the method of claim 4 wherein said needle is surrounded by a tube when it is passed into said conduit with said tube stopping in said conduit when said needle passes therethrough,

and removing said needle from said conduit after injection of said material while maintaining said tube in said conduit to allow flushing of said conduit.

9. A method in accordance with the method of claim 3 wherein said flowable material is in the form of a liquid suspension having a volatile component.

10. A power source for use in the body, or in conjunction with an implant said power source comprising,

means defining a chamber for carrying a radioisotopic material,

conduit means defining a conduit interconnected with said chamber and having an end constructed and arranged to be positioned under the skin of a body whereby radioisotopic material can be introduced into said chamber said conduit defining first and second self-sealing membranes,

said conduit means comprising radiation shielding and said conduit being positioned to shield radiation streaming paths from said chamber.

11. A power source in accordance with claim 10 wherein an interconnecting passageway leads from said second membrane to said chamber and said interconnecting passageway is tortuous.

12. A power source in accordance with claim 11 wherein said power source contains radioisotopic material in flowable form.

13. A power source in accordance with claim 12 wherein said radioisotopic material is in the form of micros heres.

. power source in accordance with claim 10 wherein two of said chambers are defined by said firstmentioned means with a conduit means for each of said chambers.

15. A power source in accordance with claim 10 wherein said self-sealing membranes are pervious to gaseous flow.

Claims

2. A method of providing power to a power source implanted in the body, said method comprising, periodically injecting radioisotopic material in flowable form through body tissue into a self-sealing conduit means in said power source without removing said power source, said injections taking place at predetermined timed intervals to maintain the power output of said source above a predetermined level.
3. A method in accordance with the method of claim 2 wherein said radioisotopic material is injected by means of a hypodermic-type needle.
4. A method in accordance with the method of claim 3 wherein said needle is passed through the skin of the body and thence through an elongated conduit having self-sealing membranes at ends thereof.
5. A method in accordance with the method of claim 4 wherein said needle is withdrawn after said injection and said conduit is flushed to irrigate and decontaminate said conduit and tip of outer needle.
6. A method in accordance with the method of claim 4 wherein said conduit is straight and is positioned to prevent radiation streaming paths from said energy source.
7. A method in accordance with the method of claim 5 wherein said conduit is tortuous and said needle is flexible so as to pass easily through said tortuous conduit.
8. A method in accordance with the method of claim 4 wherein said needle is surrounded by a tube when it is passed into said conduit with said tube stopping in said conduit when said needle passes therethrough, and removing said needle from said conduit after injection of said material while maintaining said tube in said conduit to allow flushing of said conduit.
9. A method in accordance with the method of claim 3 wherein said flowable material is in the form of a liquid suspension having a volatile component.
10. A power source for use in the body, or in conjunction with an implant said power source comprising, means defining a chamber for carrying a radioisotopic material, conduit means defining a conduit interconnected with said chamber and having an end constructed and arranged to be positioned under the skin of a body whereby radioisotopic material can be introduced into said chamber said conduit defining first and second self-sealing membranes, said conduit means comprising radiation shielding and said conduit being positioned to shield radiation streaming paths from said chamber.
11. A power source in accordance with claim 10 wherein an interconnecTing passageway leads from said second membrane to said chamber and said interconnecting passageway is tortuous.
12. A power source in accordance with claim 11 wherein said power source contains radioisotopic material in flowable form.
13. A power source in accordance with claim 12 wherein said radioisotopic material is in the form of microspheres.
14. A power source in accordance with claim 10 wherein two of said chambers are defined by said first-mentioned means with a conduit means for each of said chambers.
15. A power source in accordance with claim 10 wherein said self-sealing membranes are pervious to gaseous flow.