CA1057424A - Non-invasive nuclear device for communicating pressure inside a body to the exterior thereof - Google Patents
Non-invasive nuclear device for communicating pressure inside a body to the exterior thereofInfo
- Publication number
- CA1057424A CA1057424A CA232,094A CA232094A CA1057424A CA 1057424 A CA1057424 A CA 1057424A CA 232094 A CA232094 A CA 232094A CA 1057424 A CA1057424 A CA 1057424A
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- CA
- Canada
- Prior art keywords
- pressure
- housing
- bellows
- pressure sensor
- components
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Abstract
ABSTRACT OF THE DISCLOSURE
The present invention provides a pressure sensor apparatus for indicating pressure in the human body, particularly intracranial pressure, comprising a housing, bellows supported within said housing, wherein said bellows defines a first chamber and a second chamber within said housing, a fluid filled within said first and second chambers, means for placing said first chamber in communication with said pressure to be sensed so that said pressure will cause said bellows means to contract and expand, means contained within said housing for communicating the contraction and expansion movement of said bellows means, said communication means having at least two components, the first of said two components being operatively connected to said bellows and movable therewith when said bellows expands and contracts, the second of said two components positioned within said first chamber and being operatively associated with said first component but not movable with said bellows so that the relative movement of said first component with respect to said second component varies as a function of said pressure, said communication means being adapted to being sensed by a sensor means located at a remote position from said housing and free of any physical interconnection with said housing for sensing the relative position of said first and second components to provide data indicative of said pressure. In a preferred embodiment, the first and second components are provided by a radioactive source and an associated shield, the radioactive output varying as a function of the relative positions thereof.
The present invention provides a pressure sensor apparatus for indicating pressure in the human body, particularly intracranial pressure, comprising a housing, bellows supported within said housing, wherein said bellows defines a first chamber and a second chamber within said housing, a fluid filled within said first and second chambers, means for placing said first chamber in communication with said pressure to be sensed so that said pressure will cause said bellows means to contract and expand, means contained within said housing for communicating the contraction and expansion movement of said bellows means, said communication means having at least two components, the first of said two components being operatively connected to said bellows and movable therewith when said bellows expands and contracts, the second of said two components positioned within said first chamber and being operatively associated with said first component but not movable with said bellows so that the relative movement of said first component with respect to said second component varies as a function of said pressure, said communication means being adapted to being sensed by a sensor means located at a remote position from said housing and free of any physical interconnection with said housing for sensing the relative position of said first and second components to provide data indicative of said pressure. In a preferred embodiment, the first and second components are provided by a radioactive source and an associated shield, the radioactive output varying as a function of the relative positions thereof.
Description
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. The pxesent invention relates to a pressure sensor ~ ;
~ - ¦ for~u~n~ the pressure in a body cavity. : ;-~ ~ :
: I The need for a non-invasive technique for measuring ..
: the pressure in body cavities of animals or humans is recog- . :
nized as highly desirable for continuous or intermittent moni- I
~' toring of body conditions. Such cavities as the cranium, vena . cava, bladder and others provide valuable and sometimes critical I
i information for maintaining the well-being or survival.of an :
.... ¦ animal or human. For example, it is known that the intra-¦ cranial pressure pro~ides a valuable indication of well-being 1~
for a variety of clinical conditions, including shock trauma ~ ; ~ I
. ¦ and hydrocephalus. l ~ ~1 Present-day pressure sensors are intended for perma-nent lmplantation for non-invasive utilization of~their pressure sensing function. They do, however, constitute~a foreign. body whose pressence may create physical problems which must.be obvi~
. ~ I ated for proper functioning of the sensor and for a minimum of : I discomfort and disfigurement to the patent. For instance, it . ¦ is highly desirable that the component parts of the sensor ex- .-~
., ternal to the body portion being monitored be firmly and securely .
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. .
. The pxesent invention relates to a pressure sensor ~ ;
~ - ¦ for~u~n~ the pressure in a body cavity. : ;-~ ~ :
: I The need for a non-invasive technique for measuring ..
: the pressure in body cavities of animals or humans is recog- . :
nized as highly desirable for continuous or intermittent moni- I
~' toring of body conditions. Such cavities as the cranium, vena . cava, bladder and others provide valuable and sometimes critical I
i information for maintaining the well-being or survival.of an :
.... ¦ animal or human. For example, it is known that the intra-¦ cranial pressure pro~ides a valuable indication of well-being 1~
for a variety of clinical conditions, including shock trauma ~ ; ~ I
. ¦ and hydrocephalus. l ~ ~1 Present-day pressure sensors are intended for perma-nent lmplantation for non-invasive utilization of~their pressure sensing function. They do, however, constitute~a foreign. body whose pressence may create physical problems which must.be obvi~
. ~ I ated for proper functioning of the sensor and for a minimum of : I discomfort and disfigurement to the patent. For instance, it . ¦ is highly desirable that the component parts of the sensor ex- .-~
., ternal to the body portion being monitored be firmly and securely .
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~057a~Z4 ~ -mounted as any movement of SUCIl component parts, p~rticularly when mounted subcu~aneou.sly can produce lrritation and attendant discomfort to -the patient. It is not uncommon for body tissue such as tha-t produced by surgical scars durin~ implantation or muscular grow-th to interfere with the proper operation of the ~ -sensor by imposi.ng pressures on those parts of the device which are designed to be responsive to pressures such as ambient pres- ;
sure. ~hen such a sensor is used pa.rticularly for pressure -~ ~
. sensing of the intracranial cavity, the pressure transmitting :
fluid conduit communicating with the pressure sensing device in m ~ the cavity can easily impose pressure on the brain, the sensitive `` tissue of which can be easily damaged. Furthermore, since such ~ -~
I pressure sensin~ apparatus should be devoid of deterioration .' during its useful Iife, which may be for a period of many years, it is highly desirable that the component parts be completely :~
~ compatible and/or inert chemically and physically with the `, adjacent body portions so as to avoid any adverse reactions.
-. : Additionally, the component parts of the apparatus and pressure :~ transmitting fluid whlch are in contact should be completely ~ 20 ~compatible so as to avoid any deterloratlng reaction therebetween.
In addition, leakage between the component parts is to be avoided, but should there be a failure, the fluid should be : : , :
compatible~in the event of leakage. Furthermore, the parts should remain in perfect working order throughout the useful ~ ~
life of the apparatus. Since such a pressure sensor uses -` :
radioactive matqrial, such radioactive material should be of the ~ type which requires no replacement during the useful life of the il~ sensor and it should function in a manner which is non-injurious . ~ to the body and to provide a radioactive output in a highly ;-~ 30 accurate and uniform manner so as to reflect with extreme .~ precision, the sensed body fluid pressure throughout its range of operation under both positi~e and negative fluid pressures.
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~057a~Z4 ~ -mounted as any movement of SUCIl component parts, p~rticularly when mounted subcu~aneou.sly can produce lrritation and attendant discomfort to -the patient. It is not uncommon for body tissue such as tha-t produced by surgical scars durin~ implantation or muscular grow-th to interfere with the proper operation of the ~ -sensor by imposi.ng pressures on those parts of the device which are designed to be responsive to pressures such as ambient pres- ;
sure. ~hen such a sensor is used pa.rticularly for pressure -~ ~
. sensing of the intracranial cavity, the pressure transmitting :
fluid conduit communicating with the pressure sensing device in m ~ the cavity can easily impose pressure on the brain, the sensitive `` tissue of which can be easily damaged. Furthermore, since such ~ -~
I pressure sensin~ apparatus should be devoid of deterioration .' during its useful Iife, which may be for a period of many years, it is highly desirable that the component parts be completely :~
~ compatible and/or inert chemically and physically with the `, adjacent body portions so as to avoid any adverse reactions.
-. : Additionally, the component parts of the apparatus and pressure :~ transmitting fluid whlch are in contact should be completely ~ 20 ~compatible so as to avoid any deterloratlng reaction therebetween.
In addition, leakage between the component parts is to be avoided, but should there be a failure, the fluid should be : : , :
compatible~in the event of leakage. Furthermore, the parts should remain in perfect working order throughout the useful ~ ~
life of the apparatus. Since such a pressure sensor uses -` :
radioactive matqrial, such radioactive material should be of the ~ type which requires no replacement during the useful life of the il~ sensor and it should function in a manner which is non-injurious . ~ to the body and to provide a radioactive output in a highly ;-~ 30 accurate and uniform manner so as to reflect with extreme .~ precision, the sensed body fluid pressure throughout its range of operation under both positi~e and negative fluid pressures.
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~ 574;~4 The no~-inyasive nuc].eqr device o~ the present invention is fully irnplantable and is full~ cap~ble of col~nunica-tiny pressure inside a body to the exterior thereof to allow read out non-invasively. In its pre:Eerred form, the invention includes . .
a housing ~or subcutaneous lmplantatlon with the radioactive source contalned ln the housln~ lnterior and appropriate radiation shield means disposed about the radioactive source.
Urging means such as a bellows are provided in the housing interior which yieldingly ur~e the radioactive source and shield means .into a predetermined shielding ralationship, the fluid pressure from a fluid pressure sensing device inserted in :
the body portion being monitored being transmitted to the housing interior by means of a pressure transmitting fluid through a conduit to move said radioactive source agalnst the force of the urging means out of the inltlal or repose shielded relationship with the shield means proportionallv with an increase in pressure in the body portion being monitored to produce a radioactive :
:~ output from the radioactlve source corresponding to the magnitude ~ ~
Qf the pressure in the body portion. In one embodiment, the ; ~:;
- 20 housing is securely mounted on a supporting portion of the ~ ~ body such as a bony structure for permanent implantation under .`.;~
.. the skin, the mounting means serving as a shield for . , .
radiation directed towards the body and to confine the radio~
~ .
active output to a limited external detection area.
When the inyentive device is inserted within a body `;: portion, such as the intracranial cavity, the deformable metal tube may be shaped in accordance with the contours of the body portion thereby avoiding any pressure and attendant injury to ; adjacent bod~ portions such as the brain. To compensate for changes in ambient pressure, an ambient pressure sensor is mounted on the housin~, the interior of which is filled with a preSsure transmi'cting fluid for transmitting the sensed change in ~:
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ambient pressure to the urc~in~ ~eans in o~posi-tion to khe ~ ;
pressure exerted on the urginy means. This am~ient pressure sensor includes an annular peripheral portion and a recessed centex por-tion to limit -the imposition of pressure on the device by scar tissue or ~uscular contraction and even concentrated loads such as externally applied forces.
The invention also includes a new and novel radioactive `~
composition to produce a highly accurate radioactive output throughout both the useful life and range of operation of the invention thereby accurately reflecting the true pressure conditions within the body portion being monitored, the radio~
actiye output being of a level whlch is virtually totally non~
injurious to the body.
Thus, the pressure monitoring apparatus of the invention may be simply and easily mounted on or within a body in a concealed, non-disfiguring manner and in a permanently installed position throughout the treatment term of the patient producing virtually no injurious effects on the patient yet producing high-ly accurate body pressure reaaings throughout its life and with-out mechanical deterioration or malfunctioning and with only ~slight decay of the radioactive output which is easily compensated for thus eliminating the need for replacement and its attendant ;
sur~ical problems.
~;i Figure 1 is a perspective view of a preferred embodiment ., ~:
of the non-invasive nuclear apparatus of the invention in an ~j installed position for monitoring the pressure in an intracranial ;
. . . .
cavity and communicating the monitored pressure to the exterior of the body;
; Figure 2 is a plan view of the apparatus of Figure l;
Figure 3 is a sectional VieW taken substantially along line 3~3 of Figure 2 in the direction of the arrows;
Figure 4 is an enlarged sectional view of a portion of ~, .. . ~ .. . . .
.... . . .
.. :. , , . :. , ~7424 , the apyaratus o~ 3ure 3;
Figure 5 is an enlar~ed perspective yiew oE the mounting arran~ement lor the apparatus of Figure l; ~:
Figure 6 is a perspective view of a portion of the skull of a patient prior to installation of the apparatus of the invention;
.~ Fi~ure 7 is a sectional view taken substantially along ~ lines 7-7 of Figure l in the direction of the arrows;
: Figure 8 is a vertical, cross-sectional view of another .~ lO embodiment of the pressure sensor apparatus of the present inven~
tion; and :~
Figure 9 is a plane view, partly ln section, of one of ; the flexible tambours a portion of which is shown in Figure 8.
eferring now to the drawings and to Figures l and 2 in particular, there is shown the pressure sensing apparatus of the invention with a housing designated generally by the numeral lO, ` and fluid pressure responsive ~eans designated generally by the :~
numeral ll and connectea to the housing lO for sensing the fluid pressure in a body portlon such as a cavity. Ambient pressure - .: .
~l 20 responsive means, designated generally by the numeral 12, is also -/~ provided on the housing 10 which is responsive to ambient pressure to compensate for changes in ambient pressure during the ;~:
operation of the invention. Although the pressure sensing apparatus of the invention is shown in an installed position on ~ ~.
.~- the head of a human body fornon-invasively monitoring intracranial i cavity pressure and communicating it to the exterior, it should .
` be understood that this is only a preferred example of the . invention and that it is equally adaptable for monitoring fluid pressure in other areas o~ the body~ both animal and human.
Therefore, while the description to follow will be directed to the use of the inyention for monitor~ng intracranial cavity . pressure, it should be understood that the invention is equally . . --6- :
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applicable ~o m~nitoriny fluid ~es$ure ;n other body portions and cavities.
Referring now to Flgure 3, and as specifically illus-trative of the inven-tion, the housing 10, which is formed of titanium, is preferably of tubular shape having a side wall 13 defining an interior 14. A :Eirst support member 16 formed of titanium having a central bore 17 is positioned within one end ~;
of the housing 10 in sealing relationship with the housing side wall 13 by means of an epoxy resin or the like. PreEerably, an annular shoulder 13a is formed in the housing side wall 13 for positioning the support member 16 in a precise location within the housing 10 as will be explained hereinafter. The first ;
support member centraI bore 17 is provided with a first portion 17a of slightly enlarged diameter and a second portion 17b of `~
substantially enlarged diameter defining a recess 20 which communicates with the interior i4 of the housing 10.
The fluid pressure responsive means 11 includes a fluid conduit 22 of deformable metallic material preferably titanium ~
which has been heat treated ror deformability, one end 22a which `
is arranged to be connected to a fluid pressure sensing device or tambour 23 having an interior 24 which is arranged to be position-ed within a body cavity such asthe intracranial cavity of Figure The tambour 23 is formed of a suitable elastomeric material such as medical Grade Silastic rubber and is of a sub-stantially flat configuration including a neck portion 25 in the wall of which is molded a helical spring 26 preferably of stain-less steel for imparting rigidity to the neck portion 25. The neck portion 25 includes a central bore 25a which communicates with the interior 24 of the tar~our 23 and which is arran~ed to receive the end 22a of the conduit 22 as shown in Figure 2.
~referably a U-shaped clip 27 of tantulum or the like is disposed `: `
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10S~4Z4 within the interior 24 of ~he tambour 23 ~or maintaining the side walls of the tambour ln spaced-apart relationship and to serve as a loca-ting means for the tambour wlth the use of x-rays.
he tambour or fluid pressure sensing device ~3, the fluid conduit 22 and the communicating portions of the housing interior 14, including the recess 20, are filled with a pressure trans- ;
mitting fluid through which the pressure sensed by the tambour 23 in the body cavity is transmitted to the housing interior 14. ~ ' The other end 22b of the conduit 22 is swaged to a suitable enlarged ou-ter diameter so as to confirm generally to ~ ' the inner diameter of the enlarged portion 17a of the first '' support member central hore 17. The conduit end 22b is press- ~ , fitted into the bore portion 17a with the conduit 22 extending -~
through the bore 17 as shown best in Figure 3. Sealing engage-ment between the conduit 22 and bore 17 is obtained by means of ,~
epoxy resin. Thus, the conduit end 22b communicates with the recess 20 and with the housing interior 14.
A source 29 of radioactive material preferahly in the ~ ~
form of a shaped article is disposed within the housing interior ~`
14 together wlth radiation shield means designated generally by the numeral 31., Means are provided in the housing interior 14 for'yieldingly urging into a shielding relationship. More specifically, urging means such as a bellows 32 having an '~
interior 33 is disposed within the housing interior 14, one end 32a of which is moun-ted on a necked-down portion 34a of a second support member 34 preferably formed of titanium and suitably mounted in the other end of the housing 10 in sealing engagement with the housing side wall 13 by means of an epoxy resin or the like. The other end 32b o~ the bellows 32 is closed as ~ill be explained hereinafter.
The second support member 34 is provided ~ith a central ;'~
bore 38 and the necked-down portion 34a is arranged to support ', :` :
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the bellows end 32a in a sealiny relationship therewith by means of an epoxy resin 41 or the llke.
The central bore 38 of the second support member 34 includes a portion of enlarged diameter forminc3 a recess 42 and which is provided wi~h an annulax, inwardly directed flange 43.
The recess 42 receives and nipple 44 having a central passage 44a of an ambient pressure sensor or tambour 46 forming the ambient pressure responsive means 12. The tambour 46 is formed of a flexible material, preferably an elastomeric material such as medical Grade Silastic rubber, and includes an annular peripheral portion 47 and a recessed central portion 48 defining an interior 49 extending through the nipple central pa~ssage 44a.
A suitable adhesive such as a medical Grade Silastic adhesive, seals the nipple 44 in -the recess 42 and the annular flange 43 compresses the outer surface of the nipple 44 to form a mechanical compression seal to securely retain the nipple 44 in ~ -~`l the recess 42. ~ ;
A rigid metal tube 51, preferably formed of titanium ;
is also sealed in nipple 44 and by a Silastic adhesive and ' ~ 20 extends through nipple central passage 44a and the central bore -~38 of the second support member 34 into the bellows interior 33 - to communicate the interior 49 of the tambour 46 with the bellows ~ -~ ' 32. The other end 51b of the tube 51 forms a stop for the bellows end 32b.
.,.: . :
In order to transmit the sensed ambient pressure to the interior of the bellows 32~ the interior of tambour 46, the bellows interior 33 and the tube 51 are filled with a pressure transmitting fluid, isolated by means of the bellows 32 from the ~l pressure transmitting fluid in the fluid pressure responsive `l 30 means 11. In the preferred embodiment, all o the exposed ;~
metallic surfaces of the sensin~ apparatus of the invention are coated with a suitable biocompatible material, such as a medical ~ ;
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~57424 grade Silastic adhesive. As shown in the drawings, ~his Silastic adhesive 50 extends from the n;pple ~4 of tam~our 46 to the joint between the metal conduit 22 and the neck portion 25 of tambour 23.
In the illustra-ted embodiment, the radiation shield means 31 includes a first portion 53 of radiation shileding material such as tantalum having a cup-shaped configuration. The first portion 53 preferably includes an end plate 54 preerably in the form of a disc and an annular slde member 56 both mounted on the other end 32b of the bellows 32 in closing relationship therewith as shown best in Figure 4.
The radiation shield means first portion 53 is mounted on an inwardly directed channel poriton 57 adjacent the last accordion pleat in the bellows 32, and a tubular sleeve portion ; 58 extending axially outward therefrom which together define an enclosure 59. The end plate 54 is adhesively secured in the end of the enclosure by a suitable adhesive such as an epoxy resin closing the end 32b of the bellows 32. Similarly, side member 56 is adhesively secured by means of an epoxy resin to sleeve portion 5~.
- The radiation shield means also includes a second ;~
i , portion 61 in the form of a tubular sleeve of radiation shield :
;~ material, also preferably tantalum which is press-fitted or the ; like within the recess 20 of the first support member 16~ It can ~ be seen that the second portion 61 extends throughout the depth -~ of the recess 20 and has a fo~ard end edge por-tion 61a termin-ating flush with the end of the first support member 16 abutting the housing side wall shoulder 13a. Thus, the second portion end 61a is precisely positioned axially in the housing interior 14 adjacent the end edge portion 56a of the first portion side ~ ;
member 56.
Radioactive source 29 is mounted on the end 32b of the , ;- ' , - ,: , .: , . . , ' . : , ': ., ,, : , , :
1~57~
bellows 32 and is slidably accommoda~ed for yuiding movement within the radlation shield means second portion 61 di.sposed in the recess 20. The radioactive source 29 which .is preferably of cylindrical shape, having an outer diameter conforming generally to -the inner diameter of the bellows sl.eeve portion 58 is `
; adhesively secured within the enclosure 59 defined by -the tubular sleeve portion 58 by means o~ a suitable adhesive such as an epoxy resin. The end cap 62 haviny a meniscus 62a is form-ed by the adhesive material.
The bellows 32 yieldingly urges the radioactive source , .
29, together with the sleeve portion 58, in the direction of the . ~
arrow I into the recess 20 with the edge portion 56a of the radiation shield means first portion side member 56 in adjacent cooperating relationship with the edge portion 61a of the tubular sleeve forming the radiation shield means second portion 61 to : . :
establish a shielding relationship with the radioactive source 29. ~
The end cap 62 is therefore disposed oppositely the outlet end :~ :
. !
22b of the pressure transmitting fluid conduit 22. .
~- The outer diameter of the bellows sleeve portion 58 is selected to produce a loose-fitting relationship with the inner surface of the sleeve forming the radiation shield means second ~ portion 61 so that fluid introduced into the recess 20 from the ; end 22b of condui.t 22 may flow freel~ therebetween and through a `' gap between the front and second portions end edge portions 56a ~ and 61a respectively to fill the interior 14 of the housing lO
. on the outside of the bellows 32.
It should be understood that in the assembled apparatus :
~ of the invention before installation in a body there is virtually ;, no pressure differential in the housing 10 between the pressure ~:
, 30 transmittiny fluids on opposite side of the bellows 32. In this :. condition, there is a gap between the adjacent end edge portions ~ ~
~ 56a and 61a of the first and second portions 53 and 61 respec- : , . .. . .
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~05742~ ' tively. When the apparatus is installed .in -the body, the normal l;
fluld pressure in the body cavity slightly lncxeases the pressure on the tambour 23, in-troducing additional pressure transmitting fluid into the housiny interior 14 on the ou-tside of bellows 32, t ~ moving the bellows in the direction of the arrow D, -thexeby lncreasing slightly the gap between -the end edge porti.ons 56a and 6la.
In the operation of the invention after installation, . ..
an increase in fluid pressure is sensed in the body cavity by the fluid pressure sensing device or tambour 23, the sensed pressure is transmitted by the pressure-transmitting fluid flow~
ing into the support memher recess 20 -through the end 22b of . conduit 22 around the end cap 62 through the gap between the edge portions 56a, 61a to move the be'lows 32 together with the radiation shield means first portion 53 and the radioactive source 29 in the direction indicated by the arrow D in opposition ~' to the urging force exerted by the bellows. During this movement, the radiation shield means first and second portions 53, 61 move apart increasing the gap proportionally with the increase in .. ~
. 20 cavity fluid pressure thereby modifying the shielding relation- ;1.:
.. ship between the shield means 31 and radioactive source 29 to . expose more of the radioactive source in accordance with the magnitude of the cavity pressure. The radioactive output of :
-. the exposed portion of the radioactive source 29 may then be .:.
, :
- sensed by a conventional nuclear counter or crystal detector disposed externally of the housing 10 and the body.
The provision of the ambient pressure responsive means .
12 permits the sensing apparatus of the invention to be respon-sive to pressure changes in the body cavity regardless of / 30 ambient pressure changes, Accordingly, ambient pressure changes . .
are imposed equally on both the ambient pressure responsive ~ ;
means 12 and the cavity pressure responsive means 11 whereby .
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the sensi.ng app.lratus of the invention respond$ to hody cavity pressure changes only.
To insure a lony life for the sensing apparatus of the invention commensurate with body compatability, it has been found that specific non-reactive fluids and elastomeric materials eliminate such reactions. More specifically, the best results that have been obtained are when the elastomeric material of the various components are formed in one examp].e, from a Silastic type of silicone rubber and the pressure transmitting fluids are eithe.r castor oil or mineral oil be~ween which there is vir-tually no chemical or physical reaction whereby insuring proper functioning of the invention throughout its life. It has also been found that when the pressure transmitting fluid is a sili-cone oil, the outstanding results of the invention are accom-plished when the materials are selected from the group consisting of butyl, neoprene, suna N (a trademark) and Viton A (a trademark) rubhers. It should be understood, however, that other elasto~
meric materials and fluids perform satisfactorlly but with less ~ ;
. . .
:~ desirable results.
, .
i 20 One major concern in selecting a fluid is the osmotic pressure effects produced during implant. It is preferred to eliminate these effects that a simulated cerebrospinal fluid be used as the pressure transmitting medium and it may be used with .~ all materials of construction as it will be compatible with body ~ ~ fluids and will not leak through the elastomeric materials as a ;
: .
-: conse~uence of osmotic pressure. .~
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~-: In the use of the invention to monitor the fluid pres- ~ ~ :
~ sure within an intracranial cavity and with reference to Figures ;~
- 5-7, the common practice is to p~ovide a burr hole or aperture 70 within the bony structure of skull 71 overlying the intra~
cranial cavity through which the metallic fluid conduit 22 is ~ .
inserted, the cavity pressure sensing device 23 being suitably -13- :
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d;sposed within the intracr,lnial cayit~, The housing 10, toge-ther with the ambient pressure responsive device 12 are mounted on the ou-ter surface OL ~he skull 71 under the scalp 72.
The apparatus of the inventlon includes means for per-manently mounting the housing 10 and ambient pressure responsive means 12 subcutansously on the outer surface of -the skull 71 in an inconspicuous, securely retained position. More specifically, an elongated concave groove 73 is formed within the outer surface of the skull 71 adjacent the burr hold 70, and mounting means are provided for securing the housing 10 in a seated relationship within the groove 73. The mounting means includes at least one, ;~
preferably two, tabs 74 arranged in longitudinally spaced -, relationship on the housing 10 as shown best in Figure 5. Each -~ of the tabs 74 includes an intermediate portion 76 of arcuate . J~ cross-sectional shape for acco~nodating the tubular housing 10 ~-'~ in underlying engagemen-t therewith. The tab portion 76 is secured to the outer surface of the housing 10 by suitable means ~ -such as a body compatible adhesive, welding or the like. The tabs 74 also include oppositely disposed end portions 77 and 78 'I
extending laterally outward of the housing 10 secured within the intermediate portion 76.
' Openings 79, 81 are provided in the tab end portions 77 ,78 respectively for accommodating screw means such as screws ~ 82 extending therethrough in threaded engagement with the under-3~ ` lying bone of the skull 71, and with the end portions 77, 78 in ;~ overlying engagement with the outer surface of the skull 71, the ! . . . ~
tab intermiedate portion 76 and housing 10 being accommodated ~ -within the groove 73.
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In the preferred embodiment, the tabs 74 are preferably formed of a radiation shielding material such as tantalum. One of the tabs 74 is positioned on the housing 10 with its intermediate portion 76 extending throughout the path of movement '~
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.--~ ~5~9~24 o~ the r.~dioactive source 61 w.i.thin the hol~siny. Thus, not only does the one ~ab 74 prevent downwardly directed :radiation into ; the body, but the radioactive output of source 29 ls confined in a non~attenuating manner to the ul~ward clirection to permit easy detection by an externally positioned detection device.
The output of the radioactive source 29 need only be of ; an ex-tremely low order of magnitude typically less than 0.1 microcurie, a magnitude far less than that at which the adjacent body tissue may be adversely affected. However, it should be characterized by an extremely precise and uniform output rate which accurately reflects the changes in fluid pressure within ; the body cavity throughout its range of operation. The prefer- :
red radioisotope used in the present invention is Promethium-145 ~ and to obtain the proper radioactive output from -the source 29, i`~ it should be in the form of a shaped article of highly homogeneous ~:
s . composition. Accordingly, another novel feature of this invention . is provision of such a shaped article of radioactive material.
~; The radioactive source 29 comprises Promethium chloride ,~J (pmcl3) uniformly distributed and absorbed onto an inert carrier - 20 such as diatomaceous earth and uniformly distributed throughout :.
a suitable binder such as an epoxy resin. Sources 29Of this . composition are extremely uniform regarding the concentratlon or : distribution of the PmC13.
.. Another embodiment is shown in Figures 8 and 9. In this embodiment, pressure sensor 110 broadly comprises housing 112 and . :.
, flexible containers or tambours 11~ and 116. Housing 112 defines an interior opening 118 which is divided into two chambers 120 ~.
and 122, respectively, by bellows 124. Chambers 120 and 122 act as reservoirs for non-radioactive fluid.
: 30 Bellows support 126 is mounted in the end of housing 112 and closes chamber 120. Chamber 120 is fluidly connected to tambour 114 by means of bellows tube 128 which fits into port 130 . : . .
: -15~
, :i 105~4Z9~
of bellows suppor-~ 126 and opening 132 in the end o~ tambour 114.
Chamber 122 is closed by radioactive material tube support 134 which is mounted in the other end of housing 112 from bellows support 126. Chamber 122 is fluidly connected to tambour 116 by means of connection tube 136 which fi-ts into port 138 in radioactive material tube support 134 and into opening 140 in the end of tambour 116.
The radioactive material 142 is housed in source tube 144 which is mounted in opening 146 in radioactive material tube support 134. The open end of source tube 144 is closed by shield .
plug 148. Surrounding source tube 144 is shield tube 150 which is connected to bellows 124. Opening 152 in shield tube 150 places the face 154 of bellows 124 in communication with tamoour 116 through port 156 in the body of radioactive material tube support 134 and annular opening 158 formed hetween housing 112 ;~
.
and radioactive material tube support 134. `
Tambour 116 is li~ce tambour 123 and is filled with a non-radioactive fluid and is placed in the body cavity such as the cranium, bladder, or vena cava of an animal or human for sensing the pressure of the body cavity. Tantalum wire 60 is -placed in tambour 116 to give it suitable shape and enable it to be located non-invasively. Furthermore, a coiled spring (not shown) is placed in neck portion 162 of tambour 116. Tambour 114, like tambour 116, is filled with the same non-radioactive fluid as tambour 116 and serves to compensate for changes in ambient pressure. Optionally, tambour 114 can be eliminated, the end of bellows tube 128 sealed, and chamber 120 filled with gas or evacuated to indicate absolute pressure Also, for certain applications, tube 128 can be left open to communicate with the - -atmosphere.
~lousing 112 as well as bellows support 126 and tubes 128, `~
140 and 144 is preferably constructed of titanium. Bellows 124 i ' "'' : . : : .: . :, . . - .
~05742A
is preferably constructed of nickel and -typically has a sprlng ra-te of 0.10 lbs/ln. ~adloactlve material tube support 134, shieldinq plug 148 and shieldlng tube 150 preferably comprises tantalum shielding; however, tungsten, iridium, rhenium, platinum, rhodium, gold, or other sultable heavy me-tals can be used. All tubing, housing and dlaphragm jolnts are suitably formed by epoxies, brazing, or the use of sultable gaskets, etc.
Flnally, the entire sensor can be coated with a thin coatlng of . .
sillcone rubber or placed ln a silicone rubber boot if desired to assure tissue compatibility.
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-17- ~
~ 574;~4 The no~-inyasive nuc].eqr device o~ the present invention is fully irnplantable and is full~ cap~ble of col~nunica-tiny pressure inside a body to the exterior thereof to allow read out non-invasively. In its pre:Eerred form, the invention includes . .
a housing ~or subcutaneous lmplantatlon with the radioactive source contalned ln the housln~ lnterior and appropriate radiation shield means disposed about the radioactive source.
Urging means such as a bellows are provided in the housing interior which yieldingly ur~e the radioactive source and shield means .into a predetermined shielding ralationship, the fluid pressure from a fluid pressure sensing device inserted in :
the body portion being monitored being transmitted to the housing interior by means of a pressure transmitting fluid through a conduit to move said radioactive source agalnst the force of the urging means out of the inltlal or repose shielded relationship with the shield means proportionallv with an increase in pressure in the body portion being monitored to produce a radioactive :
:~ output from the radioactlve source corresponding to the magnitude ~ ~
Qf the pressure in the body portion. In one embodiment, the ; ~:;
- 20 housing is securely mounted on a supporting portion of the ~ ~ body such as a bony structure for permanent implantation under .`.;~
.. the skin, the mounting means serving as a shield for . , .
radiation directed towards the body and to confine the radio~
~ .
active output to a limited external detection area.
When the inyentive device is inserted within a body `;: portion, such as the intracranial cavity, the deformable metal tube may be shaped in accordance with the contours of the body portion thereby avoiding any pressure and attendant injury to ; adjacent bod~ portions such as the brain. To compensate for changes in ambient pressure, an ambient pressure sensor is mounted on the housin~, the interior of which is filled with a preSsure transmi'cting fluid for transmitting the sensed change in ~:
- , . . :
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ambient pressure to the urc~in~ ~eans in o~posi-tion to khe ~ ;
pressure exerted on the urginy means. This am~ient pressure sensor includes an annular peripheral portion and a recessed centex por-tion to limit -the imposition of pressure on the device by scar tissue or ~uscular contraction and even concentrated loads such as externally applied forces.
The invention also includes a new and novel radioactive `~
composition to produce a highly accurate radioactive output throughout both the useful life and range of operation of the invention thereby accurately reflecting the true pressure conditions within the body portion being monitored, the radio~
actiye output being of a level whlch is virtually totally non~
injurious to the body.
Thus, the pressure monitoring apparatus of the invention may be simply and easily mounted on or within a body in a concealed, non-disfiguring manner and in a permanently installed position throughout the treatment term of the patient producing virtually no injurious effects on the patient yet producing high-ly accurate body pressure reaaings throughout its life and with-out mechanical deterioration or malfunctioning and with only ~slight decay of the radioactive output which is easily compensated for thus eliminating the need for replacement and its attendant ;
sur~ical problems.
~;i Figure 1 is a perspective view of a preferred embodiment ., ~:
of the non-invasive nuclear apparatus of the invention in an ~j installed position for monitoring the pressure in an intracranial ;
. . . .
cavity and communicating the monitored pressure to the exterior of the body;
; Figure 2 is a plan view of the apparatus of Figure l;
Figure 3 is a sectional VieW taken substantially along line 3~3 of Figure 2 in the direction of the arrows;
Figure 4 is an enlarged sectional view of a portion of ~, .. . ~ .. . . .
.... . . .
.. :. , , . :. , ~7424 , the apyaratus o~ 3ure 3;
Figure 5 is an enlar~ed perspective yiew oE the mounting arran~ement lor the apparatus of Figure l; ~:
Figure 6 is a perspective view of a portion of the skull of a patient prior to installation of the apparatus of the invention;
.~ Fi~ure 7 is a sectional view taken substantially along ~ lines 7-7 of Figure l in the direction of the arrows;
: Figure 8 is a vertical, cross-sectional view of another .~ lO embodiment of the pressure sensor apparatus of the present inven~
tion; and :~
Figure 9 is a plane view, partly ln section, of one of ; the flexible tambours a portion of which is shown in Figure 8.
eferring now to the drawings and to Figures l and 2 in particular, there is shown the pressure sensing apparatus of the invention with a housing designated generally by the numeral lO, ` and fluid pressure responsive ~eans designated generally by the :~
numeral ll and connectea to the housing lO for sensing the fluid pressure in a body portlon such as a cavity. Ambient pressure - .: .
~l 20 responsive means, designated generally by the numeral 12, is also -/~ provided on the housing 10 which is responsive to ambient pressure to compensate for changes in ambient pressure during the ;~:
operation of the invention. Although the pressure sensing apparatus of the invention is shown in an installed position on ~ ~.
.~- the head of a human body fornon-invasively monitoring intracranial i cavity pressure and communicating it to the exterior, it should .
` be understood that this is only a preferred example of the . invention and that it is equally adaptable for monitoring fluid pressure in other areas o~ the body~ both animal and human.
Therefore, while the description to follow will be directed to the use of the inyention for monitor~ng intracranial cavity . pressure, it should be understood that the invention is equally . . --6- :
lOS74Z~ ~
.
applicable ~o m~nitoriny fluid ~es$ure ;n other body portions and cavities.
Referring now to Flgure 3, and as specifically illus-trative of the inven-tion, the housing 10, which is formed of titanium, is preferably of tubular shape having a side wall 13 defining an interior 14. A :Eirst support member 16 formed of titanium having a central bore 17 is positioned within one end ~;
of the housing 10 in sealing relationship with the housing side wall 13 by means of an epoxy resin or the like. PreEerably, an annular shoulder 13a is formed in the housing side wall 13 for positioning the support member 16 in a precise location within the housing 10 as will be explained hereinafter. The first ;
support member centraI bore 17 is provided with a first portion 17a of slightly enlarged diameter and a second portion 17b of `~
substantially enlarged diameter defining a recess 20 which communicates with the interior i4 of the housing 10.
The fluid pressure responsive means 11 includes a fluid conduit 22 of deformable metallic material preferably titanium ~
which has been heat treated ror deformability, one end 22a which `
is arranged to be connected to a fluid pressure sensing device or tambour 23 having an interior 24 which is arranged to be position-ed within a body cavity such asthe intracranial cavity of Figure The tambour 23 is formed of a suitable elastomeric material such as medical Grade Silastic rubber and is of a sub-stantially flat configuration including a neck portion 25 in the wall of which is molded a helical spring 26 preferably of stain-less steel for imparting rigidity to the neck portion 25. The neck portion 25 includes a central bore 25a which communicates with the interior 24 of the tar~our 23 and which is arran~ed to receive the end 22a of the conduit 22 as shown in Figure 2.
~referably a U-shaped clip 27 of tantulum or the like is disposed `: `
. .
., .
10S~4Z4 within the interior 24 of ~he tambour 23 ~or maintaining the side walls of the tambour ln spaced-apart relationship and to serve as a loca-ting means for the tambour wlth the use of x-rays.
he tambour or fluid pressure sensing device ~3, the fluid conduit 22 and the communicating portions of the housing interior 14, including the recess 20, are filled with a pressure trans- ;
mitting fluid through which the pressure sensed by the tambour 23 in the body cavity is transmitted to the housing interior 14. ~ ' The other end 22b of the conduit 22 is swaged to a suitable enlarged ou-ter diameter so as to confirm generally to ~ ' the inner diameter of the enlarged portion 17a of the first '' support member central hore 17. The conduit end 22b is press- ~ , fitted into the bore portion 17a with the conduit 22 extending -~
through the bore 17 as shown best in Figure 3. Sealing engage-ment between the conduit 22 and bore 17 is obtained by means of ,~
epoxy resin. Thus, the conduit end 22b communicates with the recess 20 and with the housing interior 14.
A source 29 of radioactive material preferahly in the ~ ~
form of a shaped article is disposed within the housing interior ~`
14 together wlth radiation shield means designated generally by the numeral 31., Means are provided in the housing interior 14 for'yieldingly urging into a shielding relationship. More specifically, urging means such as a bellows 32 having an '~
interior 33 is disposed within the housing interior 14, one end 32a of which is moun-ted on a necked-down portion 34a of a second support member 34 preferably formed of titanium and suitably mounted in the other end of the housing 10 in sealing engagement with the housing side wall 13 by means of an epoxy resin or the like. The other end 32b o~ the bellows 32 is closed as ~ill be explained hereinafter.
The second support member 34 is provided ~ith a central ;'~
bore 38 and the necked-down portion 34a is arranged to support ', :` :
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~L~S742~ :
the bellows end 32a in a sealiny relationship therewith by means of an epoxy resin 41 or the llke.
The central bore 38 of the second support member 34 includes a portion of enlarged diameter forminc3 a recess 42 and which is provided wi~h an annulax, inwardly directed flange 43.
The recess 42 receives and nipple 44 having a central passage 44a of an ambient pressure sensor or tambour 46 forming the ambient pressure responsive means 12. The tambour 46 is formed of a flexible material, preferably an elastomeric material such as medical Grade Silastic rubber, and includes an annular peripheral portion 47 and a recessed central portion 48 defining an interior 49 extending through the nipple central pa~ssage 44a.
A suitable adhesive such as a medical Grade Silastic adhesive, seals the nipple 44 in -the recess 42 and the annular flange 43 compresses the outer surface of the nipple 44 to form a mechanical compression seal to securely retain the nipple 44 in ~ -~`l the recess 42. ~ ;
A rigid metal tube 51, preferably formed of titanium ;
is also sealed in nipple 44 and by a Silastic adhesive and ' ~ 20 extends through nipple central passage 44a and the central bore -~38 of the second support member 34 into the bellows interior 33 - to communicate the interior 49 of the tambour 46 with the bellows ~ -~ ' 32. The other end 51b of the tube 51 forms a stop for the bellows end 32b.
.,.: . :
In order to transmit the sensed ambient pressure to the interior of the bellows 32~ the interior of tambour 46, the bellows interior 33 and the tube 51 are filled with a pressure transmitting fluid, isolated by means of the bellows 32 from the ~l pressure transmitting fluid in the fluid pressure responsive `l 30 means 11. In the preferred embodiment, all o the exposed ;~
metallic surfaces of the sensin~ apparatus of the invention are coated with a suitable biocompatible material, such as a medical ~ ;
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~57424 grade Silastic adhesive. As shown in the drawings, ~his Silastic adhesive 50 extends from the n;pple ~4 of tam~our 46 to the joint between the metal conduit 22 and the neck portion 25 of tambour 23.
In the illustra-ted embodiment, the radiation shield means 31 includes a first portion 53 of radiation shileding material such as tantalum having a cup-shaped configuration. The first portion 53 preferably includes an end plate 54 preerably in the form of a disc and an annular slde member 56 both mounted on the other end 32b of the bellows 32 in closing relationship therewith as shown best in Figure 4.
The radiation shield means first portion 53 is mounted on an inwardly directed channel poriton 57 adjacent the last accordion pleat in the bellows 32, and a tubular sleeve portion ; 58 extending axially outward therefrom which together define an enclosure 59. The end plate 54 is adhesively secured in the end of the enclosure by a suitable adhesive such as an epoxy resin closing the end 32b of the bellows 32. Similarly, side member 56 is adhesively secured by means of an epoxy resin to sleeve portion 5~.
- The radiation shield means also includes a second ;~
i , portion 61 in the form of a tubular sleeve of radiation shield :
;~ material, also preferably tantalum which is press-fitted or the ; like within the recess 20 of the first support member 16~ It can ~ be seen that the second portion 61 extends throughout the depth -~ of the recess 20 and has a fo~ard end edge por-tion 61a termin-ating flush with the end of the first support member 16 abutting the housing side wall shoulder 13a. Thus, the second portion end 61a is precisely positioned axially in the housing interior 14 adjacent the end edge portion 56a of the first portion side ~ ;
member 56.
Radioactive source 29 is mounted on the end 32b of the , ;- ' , - ,: , .: , . . , ' . : , ': ., ,, : , , :
1~57~
bellows 32 and is slidably accommoda~ed for yuiding movement within the radlation shield means second portion 61 di.sposed in the recess 20. The radioactive source 29 which .is preferably of cylindrical shape, having an outer diameter conforming generally to -the inner diameter of the bellows sl.eeve portion 58 is `
; adhesively secured within the enclosure 59 defined by -the tubular sleeve portion 58 by means o~ a suitable adhesive such as an epoxy resin. The end cap 62 haviny a meniscus 62a is form-ed by the adhesive material.
The bellows 32 yieldingly urges the radioactive source , .
29, together with the sleeve portion 58, in the direction of the . ~
arrow I into the recess 20 with the edge portion 56a of the radiation shield means first portion side member 56 in adjacent cooperating relationship with the edge portion 61a of the tubular sleeve forming the radiation shield means second portion 61 to : . :
establish a shielding relationship with the radioactive source 29. ~
The end cap 62 is therefore disposed oppositely the outlet end :~ :
. !
22b of the pressure transmitting fluid conduit 22. .
~- The outer diameter of the bellows sleeve portion 58 is selected to produce a loose-fitting relationship with the inner surface of the sleeve forming the radiation shield means second ~ portion 61 so that fluid introduced into the recess 20 from the ; end 22b of condui.t 22 may flow freel~ therebetween and through a `' gap between the front and second portions end edge portions 56a ~ and 61a respectively to fill the interior 14 of the housing lO
. on the outside of the bellows 32.
It should be understood that in the assembled apparatus :
~ of the invention before installation in a body there is virtually ;, no pressure differential in the housing 10 between the pressure ~:
, 30 transmittiny fluids on opposite side of the bellows 32. In this :. condition, there is a gap between the adjacent end edge portions ~ ~
~ 56a and 61a of the first and second portions 53 and 61 respec- : , . .. . .
''.:.' ' '- . , ~;,- '. ` , ' : . .
. ! ~ . . ~
r, ~' ''' ' '', .~ ' ''. ' ' '' ' ' ' '''', .
~05742~ ' tively. When the apparatus is installed .in -the body, the normal l;
fluld pressure in the body cavity slightly lncxeases the pressure on the tambour 23, in-troducing additional pressure transmitting fluid into the housiny interior 14 on the ou-tside of bellows 32, t ~ moving the bellows in the direction of the arrow D, -thexeby lncreasing slightly the gap between -the end edge porti.ons 56a and 6la.
In the operation of the invention after installation, . ..
an increase in fluid pressure is sensed in the body cavity by the fluid pressure sensing device or tambour 23, the sensed pressure is transmitted by the pressure-transmitting fluid flow~
ing into the support memher recess 20 -through the end 22b of . conduit 22 around the end cap 62 through the gap between the edge portions 56a, 61a to move the be'lows 32 together with the radiation shield means first portion 53 and the radioactive source 29 in the direction indicated by the arrow D in opposition ~' to the urging force exerted by the bellows. During this movement, the radiation shield means first and second portions 53, 61 move apart increasing the gap proportionally with the increase in .. ~
. 20 cavity fluid pressure thereby modifying the shielding relation- ;1.:
.. ship between the shield means 31 and radioactive source 29 to . expose more of the radioactive source in accordance with the magnitude of the cavity pressure. The radioactive output of :
-. the exposed portion of the radioactive source 29 may then be .:.
, :
- sensed by a conventional nuclear counter or crystal detector disposed externally of the housing 10 and the body.
The provision of the ambient pressure responsive means .
12 permits the sensing apparatus of the invention to be respon-sive to pressure changes in the body cavity regardless of / 30 ambient pressure changes, Accordingly, ambient pressure changes . .
are imposed equally on both the ambient pressure responsive ~ ;
means 12 and the cavity pressure responsive means 11 whereby .
~12~
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~574Z~ :
.,~ .
the sensi.ng app.lratus of the invention respond$ to hody cavity pressure changes only.
To insure a lony life for the sensing apparatus of the invention commensurate with body compatability, it has been found that specific non-reactive fluids and elastomeric materials eliminate such reactions. More specifically, the best results that have been obtained are when the elastomeric material of the various components are formed in one examp].e, from a Silastic type of silicone rubber and the pressure transmitting fluids are eithe.r castor oil or mineral oil be~ween which there is vir-tually no chemical or physical reaction whereby insuring proper functioning of the invention throughout its life. It has also been found that when the pressure transmitting fluid is a sili-cone oil, the outstanding results of the invention are accom-plished when the materials are selected from the group consisting of butyl, neoprene, suna N (a trademark) and Viton A (a trademark) rubhers. It should be understood, however, that other elasto~
meric materials and fluids perform satisfactorlly but with less ~ ;
. . .
:~ desirable results.
, .
i 20 One major concern in selecting a fluid is the osmotic pressure effects produced during implant. It is preferred to eliminate these effects that a simulated cerebrospinal fluid be used as the pressure transmitting medium and it may be used with .~ all materials of construction as it will be compatible with body ~ ~ fluids and will not leak through the elastomeric materials as a ;
: .
-: conse~uence of osmotic pressure. .~
. :.: .
~-: In the use of the invention to monitor the fluid pres- ~ ~ :
~ sure within an intracranial cavity and with reference to Figures ;~
- 5-7, the common practice is to p~ovide a burr hole or aperture 70 within the bony structure of skull 71 overlying the intra~
cranial cavity through which the metallic fluid conduit 22 is ~ .
inserted, the cavity pressure sensing device 23 being suitably -13- :
, . . : : . ~ .
:
1al574;~
d;sposed within the intracr,lnial cayit~, The housing 10, toge-ther with the ambient pressure responsive device 12 are mounted on the ou-ter surface OL ~he skull 71 under the scalp 72.
The apparatus of the inventlon includes means for per-manently mounting the housing 10 and ambient pressure responsive means 12 subcutansously on the outer surface of -the skull 71 in an inconspicuous, securely retained position. More specifically, an elongated concave groove 73 is formed within the outer surface of the skull 71 adjacent the burr hold 70, and mounting means are provided for securing the housing 10 in a seated relationship within the groove 73. The mounting means includes at least one, ;~
preferably two, tabs 74 arranged in longitudinally spaced -, relationship on the housing 10 as shown best in Figure 5. Each -~ of the tabs 74 includes an intermediate portion 76 of arcuate . J~ cross-sectional shape for acco~nodating the tubular housing 10 ~-'~ in underlying engagemen-t therewith. The tab portion 76 is secured to the outer surface of the housing 10 by suitable means ~ -such as a body compatible adhesive, welding or the like. The tabs 74 also include oppositely disposed end portions 77 and 78 'I
extending laterally outward of the housing 10 secured within the intermediate portion 76.
' Openings 79, 81 are provided in the tab end portions 77 ,78 respectively for accommodating screw means such as screws ~ 82 extending therethrough in threaded engagement with the under-3~ ` lying bone of the skull 71, and with the end portions 77, 78 in ;~ overlying engagement with the outer surface of the skull 71, the ! . . . ~
tab intermiedate portion 76 and housing 10 being accommodated ~ -within the groove 73.
::
In the preferred embodiment, the tabs 74 are preferably formed of a radiation shielding material such as tantalum. One of the tabs 74 is positioned on the housing 10 with its intermediate portion 76 extending throughout the path of movement '~
. ~
. ~
:.. . . . . . ., , , .~ , . , . , . , ~ ~
.--~ ~5~9~24 o~ the r.~dioactive source 61 w.i.thin the hol~siny. Thus, not only does the one ~ab 74 prevent downwardly directed :radiation into ; the body, but the radioactive output of source 29 ls confined in a non~attenuating manner to the ul~ward clirection to permit easy detection by an externally positioned detection device.
The output of the radioactive source 29 need only be of ; an ex-tremely low order of magnitude typically less than 0.1 microcurie, a magnitude far less than that at which the adjacent body tissue may be adversely affected. However, it should be characterized by an extremely precise and uniform output rate which accurately reflects the changes in fluid pressure within ; the body cavity throughout its range of operation. The prefer- :
red radioisotope used in the present invention is Promethium-145 ~ and to obtain the proper radioactive output from -the source 29, i`~ it should be in the form of a shaped article of highly homogeneous ~:
s . composition. Accordingly, another novel feature of this invention . is provision of such a shaped article of radioactive material.
~; The radioactive source 29 comprises Promethium chloride ,~J (pmcl3) uniformly distributed and absorbed onto an inert carrier - 20 such as diatomaceous earth and uniformly distributed throughout :.
a suitable binder such as an epoxy resin. Sources 29Of this . composition are extremely uniform regarding the concentratlon or : distribution of the PmC13.
.. Another embodiment is shown in Figures 8 and 9. In this embodiment, pressure sensor 110 broadly comprises housing 112 and . :.
, flexible containers or tambours 11~ and 116. Housing 112 defines an interior opening 118 which is divided into two chambers 120 ~.
and 122, respectively, by bellows 124. Chambers 120 and 122 act as reservoirs for non-radioactive fluid.
: 30 Bellows support 126 is mounted in the end of housing 112 and closes chamber 120. Chamber 120 is fluidly connected to tambour 114 by means of bellows tube 128 which fits into port 130 . : . .
: -15~
, :i 105~4Z9~
of bellows suppor-~ 126 and opening 132 in the end o~ tambour 114.
Chamber 122 is closed by radioactive material tube support 134 which is mounted in the other end of housing 112 from bellows support 126. Chamber 122 is fluidly connected to tambour 116 by means of connection tube 136 which fi-ts into port 138 in radioactive material tube support 134 and into opening 140 in the end of tambour 116.
The radioactive material 142 is housed in source tube 144 which is mounted in opening 146 in radioactive material tube support 134. The open end of source tube 144 is closed by shield .
plug 148. Surrounding source tube 144 is shield tube 150 which is connected to bellows 124. Opening 152 in shield tube 150 places the face 154 of bellows 124 in communication with tamoour 116 through port 156 in the body of radioactive material tube support 134 and annular opening 158 formed hetween housing 112 ;~
.
and radioactive material tube support 134. `
Tambour 116 is li~ce tambour 123 and is filled with a non-radioactive fluid and is placed in the body cavity such as the cranium, bladder, or vena cava of an animal or human for sensing the pressure of the body cavity. Tantalum wire 60 is -placed in tambour 116 to give it suitable shape and enable it to be located non-invasively. Furthermore, a coiled spring (not shown) is placed in neck portion 162 of tambour 116. Tambour 114, like tambour 116, is filled with the same non-radioactive fluid as tambour 116 and serves to compensate for changes in ambient pressure. Optionally, tambour 114 can be eliminated, the end of bellows tube 128 sealed, and chamber 120 filled with gas or evacuated to indicate absolute pressure Also, for certain applications, tube 128 can be left open to communicate with the - -atmosphere.
~lousing 112 as well as bellows support 126 and tubes 128, `~
140 and 144 is preferably constructed of titanium. Bellows 124 i ' "'' : . : : .: . :, . . - .
~05742A
is preferably constructed of nickel and -typically has a sprlng ra-te of 0.10 lbs/ln. ~adloactlve material tube support 134, shieldinq plug 148 and shieldlng tube 150 preferably comprises tantalum shielding; however, tungsten, iridium, rhenium, platinum, rhodium, gold, or other sultable heavy me-tals can be used. All tubing, housing and dlaphragm jolnts are suitably formed by epoxies, brazing, or the use of sultable gaskets, etc.
Flnally, the entire sensor can be coated with a thin coatlng of . .
sillcone rubber or placed ln a silicone rubber boot if desired to assure tissue compatibility.
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-17- ~
Claims (20)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A pressure sensor apparatus for indicating pressure in the human body, particularly intracranial pressure, comprising a housing, bellows means supported within said housing, wherein said bellows means defines a first chamber and a second chamber within said housing, a fluid filled within said first and second chambers, means for placing said first chamber in communication with said pressure to be sensed so that said pressure will cause said bellows means to contract and expand, means contained within said housing for communicating the contraction and expansion movement of said bellows means, said communication means having at least two components, the first of said two components being operatively connected to said bellows means and movable therewith when said bellows means expands and contracts, the second of said two components positioned within said first chamber and being operatively associated with said first component but not connected to, nor movable with said bellows means so that the relative movement of said first component with respect to said second component varies as a function of said pressure, said communica-tion means being adapted to being sensed by a sensor means located at a remote position from said housing and free of any physical interconnection with said housing for sensing the relative position of said first and second components to provide data indicative of said pressure.
2. A pressure sensor as claimed in Claim 1, wherein the first of said two components is a radioactive source, the second of said two components is a radioactive shield, whereby relative movement of said source and shield causes a variation in the radioactive output therefrom as a function of said pressure.
3. A pressure sensor as claimed in Claim 1, wherein the first of said two components is a radioactive shield and the second of said two components is a radioactive source, whereby relative movement of said source and shield causes a variation in the radioactive output therefrom as a function of said pressure.
4. A pressure sensor in accordance with any one of claims 1 to 3 wherein ambient pressure responsive means are pro-vided communicating with said second chamber for transmitting ambient pressure to said bellows means in the direction of the urging force of said bellows means.
5. A pressure sensor in accordance with any one of claims 1 to 3 wherein said pressure responsive means includes a pressure sensing device of flexible material for insertion in the body cavity and a pressure-transmitting fluid in said pressure sensing device communicating with said first chamber for trans-mitting the pressure in said body cavity sensed by said pressure sensing device to said housing interior.
6. A pressure sensor in accordance with any one of claims 1 to 3 wherein said pressure sensing device comprises a substantially planar member of flexible material having an interior and a neck portion having one end communicating with said housing interior and the other end with the interior of said planar member.
7. A pressure sensor according to claim 2 or claim 3 wherein said radiation shielding means includes a window for said radioactive source.
8. A pressure sensor according to claim 2 or claim 3 wherein said radioactive source is a solid mass.
9. A pressure sensor according to claim 2 or claim 3 wherein said radioactive source is a solid mass of promethium 145 in a binder.
10. A pressure sensor in accordance with claim 1 wherein said pressure responsive means includes as a fluid conduit formed of deformable metallic material to permit said conduit to be shaped to the contours of the body portions adjacent said body cavity.
11. A pressure sensor in accordance with any one of claims 1 to 3 wherein at least part of said pressure responsive means is formed of a silicone rubber material and includes a pressure-transmitting fluid selected from the group consisting of castor oil and mineral oil.
12. A pressure sensor in accordance with any one of claims 1 to 3 wherein said pressure responsive means includes a silicone oil as a pressure-transmitting fluid and wherein at least part of said pressure responsive means is formed of an elastomeric material selected from the group consisting of butyl rubber, neoprene rubber, butadiene rubber and fluorelastomer.
13. A pressure sensing device in accordance with any one of claims l to 3 wherein said pressure responsive means is formed in part from an elastomer and includes as a pressure trans-mitting fluid a similated cerebrospinal fluid.
14. A pressure sensor according to claim 2 or claim 3 wherein said radiation shielding means defines a gap in the repose condition which gap is incrementally exposing said radioactive source with infinite resolution.
15. A pressure sensor according to claim 2 or claim 3 wherein said radiation shielding means and said radioactive source are slidably arranged in loose fitting relationship to define a flow passage therebetween.
16. A pressure sensor according to claim 1 further including means for securing said sensor to a portion of the body whose pressure is being monitored.
17. A pressure sensor according to claim 16, wherein the securing means is a tab having an intermediate portion of arcuate cross-sectional shape for accommodating said housing in underlying clamped engagement therewith and fastening means to secure said tab to the body portion.
18. A pressure sensor in accordance with claim 17 wherein said means for securing is formed at least in part of tantalum.
19. A pressure sensing apparatus in accordance with claim 10 wherein said fluid conduit is formed of titanium.
20. A mounting arrangement in accordance with claim 17 wherein adhesive means are provided to secure said tab to said housing.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA232,094A CA1057424A (en) | 1975-07-23 | 1975-07-23 | Non-invasive nuclear device for communicating pressure inside a body to the exterior thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA232,094A CA1057424A (en) | 1975-07-23 | 1975-07-23 | Non-invasive nuclear device for communicating pressure inside a body to the exterior thereof |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1057424A true CA1057424A (en) | 1979-06-26 |
Family
ID=4103684
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA232,094A Expired CA1057424A (en) | 1975-07-23 | 1975-07-23 | Non-invasive nuclear device for communicating pressure inside a body to the exterior thereof |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1057424A (en) |
-
1975
- 1975-07-23 CA CA232,094A patent/CA1057424A/en not_active Expired
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