U.S. patent number 3,741,198 [Application Number 05/188,337] was granted by the patent office on 1973-06-26 for radiological diagnostic method.
This patent grant is currently assigned to Temple University. Invention is credited to Charles Burton.
United States Patent |
3,741,198 |
Burton |
June 26, 1973 |
RADIOLOGICAL DIAGNOSTIC METHOD
Abstract
A radiological diagnostic method is provided in which a
radiopaque ferrofluid is injected into a body system which is to be
studied, such as the subarachnoid space surrounding the spinal
cord. The ferrofluid is then transferred through the body system by
applying a magnetic force to the ferrofluid. The portions of the
body system of particular interest are radiographicly or
fluoroscopicly examined while the ferrofluid is present in these
areas. The ferrofluid is thereafter removed by drawing it back to
the point of introduction and removing it from the body system. The
diagnostic method of this invention is especially useful in
myelographic studies.
Inventors: |
Burton; Charles (Gladwyne,
PA) |
Assignee: |
Temple University
(Philadelphia, PA)
|
Family
ID: |
22692743 |
Appl.
No.: |
05/188,337 |
Filed: |
October 12, 1971 |
Current U.S.
Class: |
600/431;
250/302 |
Current CPC
Class: |
A61B
5/06 (20130101); A61B 6/481 (20130101); A61B
6/506 (20130101) |
Current International
Class: |
A61B
5/06 (20060101); A61B 6/00 (20060101); A61b
005/00 () |
Field of
Search: |
;128/2A,2R,2.5R
;250/65R |
Other References
some Applications of Ferrofluid Magnetic Colloids, by R. Kaiser and
G. Miskolczy, Apr. 1970. .
Occlusion of Intercranial Aneurisms by Ferromagnetic Thrombi, D. A.
Roth, Journal of Applied Physics, Vol. 40, Pages 1044-1045,
1969..
|
Primary Examiner: Laudenslager; Lucie H.
Claims
I claim:
1. The method for radiologically examining a body system having an
internal area which contains a fluid which is relatively static or
which has a mucous lining, said method comprising inserting into
said area a given amount of a radiopaque ferrofluid comprised of
ferromagnetic domain particles having a diameter of from about
10-300 A which are enveloped with a physiologically inert liquid
carrier which is insoluble and immiscible with said fluid and
mucous, said given amount being an amount sufficient to provide an
effective contrast in radiopaqueness for a radiological
examination; radiological examining said body system, and
thereafter removing said ferrofluid from said body system by
applying a magnetic force to an extraction means inserted into said
area sufficient to magnetically attract said ferrofluid to said
extraction means and withdrawing said ferrofluid with said
extraction means.
2. The method according to claim 1 wherein the amount of ferrofluid
inserted is less than the volume of the area and wherein the
ferrofluid is moved from the point of introduction to a portion of
said area by applying a magnetic force to said ferrofluid.
3. The method according to claim 1 wherein the amount of magnetic
force delivered to said ferrofluid is from about 5,000-10,000
Gauss.
4. The method according to claim 1 wherein said magnetic force is
provided by a permanent magnet comprised of a member selected from
the group consisting of a rare earth metal, nickel, cobalt, alloys
thereof and alloys with aluminum.
5. The method according to claim 4 wherein said magnet is a
samarium-cobalt magnet.
6. The method according to claim 1 wherein said liquid carrier is a
fluorinated lower aliphatic hydrocarbon.
7. The method according to claim 1 for radiological examining of
the spinal column comprising the steps of inserting a lumbar
puncture needle into the subarachnoid space; injecting said given
amount of said ferrofluid through said lumbar puncture needle into
the subarachnoid space; moving said ferrofluid from the point of
insertion through the subarachnoid space by applying a magnetic
force of about 5,000-10,000 Gauss to said ferrofluid to transfer
said ferrofluid to a section of said area to be radiologically
studied; radiologically examining said section; thereafter moving
said ferrofluid back to the point of insertion and withdrawing it
through said lumbar puncture needle.
8. The method according to claim 7 wherein the ferrofluid is
injected into the subarachnoid space surrounding the cauda
equina.
9. The method according to claim 7 wherein the magnetic force is
provided by a permanent magnet made of a member selected from the
group consisting of a rare earth metal, nickel, cobalt, alloys
thereof and alloys with aluminum.
10. The method according to claim 9 wherein the magnet is a
samarium-cobalt magnet.
11. The method according to claim 7 wherein the lumbar puncture
needle has a given ID, a given length and a sharpened bevel at a
terminal end thereof, within which an insert needle made of a
magnetizable metal having an OD less than said given ID, a length
greater than said given length, and a smooth, round, perforated tip
is inserted after insertion of the lumbar puncture needle, into the
subarachnoid space with tip of the insert needle extending past the
bevel of the lumbar puncture needle and thereafter the insert
needle is magnetized to attract the ferrofluid to the tip of the
insert needle through which the ferrofluid is removed after
completion of the radiological examination.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention is concerned with a radiological diagnostic
method.
2. Description of the Prior Art
Radiological diagnostic procedures are widely used in the medical
field to detect various abnormalities of the body, such as broken
bones, ulcers, tumors, and the like. In order to obtain
satisfactory results with radiological procedures, it is necessary
to have a substantial difference in the radiopaqueness of the area
which is desired to be examined and the immediate surrounding areas
of the body. When a radiological study is made, to determine for
example, if one of the long bones of the body is broken no
particular problems are encountered, in that bone is relatively
radiopaque as compared to the surrounding soft tissues.
However, when a radiological study is made of certain parts of the
body, there is often an insufficient amount of contrast in the
radiopaqueness of the areas to be studied and the surrounding
tissues, or, the area to be examined is covered by a relatively
radiopaque material which shields the desired area of study. A
typical situation of this type is when a myelographm is performed,
wherein the subarachnoid space surrounding the spinal cord is
X-rayed to determine if any abnormalities distorting its normal
pattern are present, such as tumors, herniated discs, osteophytic
spurs, abscesses, and the like. Because of the presence of the
protective relatively radiopaque shield of vertebrae about the
spinal column and the relative similarity and lack of
radiopaqueness of the elements comprising the soft tissues of the
spinal column, such as the spinal cord, and the pia, arachnoid and
dura membranes, it is necessary to inject a radiopaque material
into the spinal column to increase the radiopaqueness of the
subarachnoid space.
Various materials have heretofore been suggested to increase
radiopaqueness when conducting myelographic studies. One such
method was to inject a gas such as air into the spinal column to
replace part of the spinal fluid. This method has proven to be
highly unsatisfactory because the patient is subjected to
considerable pain as a result of the injection of the gaseous
material, and in addition, the relative degree of radio-opacity is
at best only marginal.
An additional method which has been suggested, is to inject
radiopaque liquids into the spinal column. A typical type of
compound which is used for this purpose is the compound of the
formula ##SPC1##
One of the problems encountered with the injection of such
radiopaque liquids heretofore suggested was that the compounds, for
clinical reasons, should be completely removed after the
radiological examination is completed. In actual practice, however,
it has been found that it is virtually impossible to completely
remove all of the injected compound from the spinal column. It is
believed that the residual amounts of these radiopaque materials
are a definite contributory factor in causing the highly painful
condition known as adhesive arachnoiditis.
A common technical problem usually encountered when using either
gases or conventional radiopaque liquids is that it is difficult to
move and accurately position the injected material in the desired
location required for the radiological examination. For example, in
myelography, the radiopaque agent, whether it is gas or a liquid,
is normally injected into the low lumbar subarachnoid space, that
is, the portion of the spinal column which is below the lower
terminal end of the spinal cord in order to avoid injury to the
spinal cord itself. A myelogram, however, generally involves a
study of the spinal cord and the surrounding tissues. For this
reason, the injected material must be moved up the spinal column to
the desired areas of study.
Using the prior art techniques this was accomplished by employing
only the difference in the specific gravity of the injected
material and the normal body fluid of the body system being
evaluated. The relative body position of the patient is changed so
as to facilitate the movement of the injected material. The gases
which are injected are hyperbaric as compared to spinal fluid which
has about the specific gravity of saline. The liquids, on the other
hand, are hyperbaric as compared to spinal fluid. To move the
injected material from one position to another, requires that the
body of the patient be tilted to cause the material to flow from
one part of the spinal column to another. Due to the difference
between specific gravities of the injected material and spinal
fluid, the patient is generally raised or lowered on a tilt table
especially designed for this purpose. However, even using this
specialized apparatus, the process is at best, uncomfortable and
often quite painful to the patient, especially in cases where the
patient has an acute spinal abnormality. It should be further
noted, that in certain situations, it is even necessary to rotate
the patient approximately 180.degree. with respect to the normal
erect position so that his head is in a downward position. This of
course, is highly uncomfortable and in some cases, highly
dangerous.
The gravitational technique for moving the injected material
throughout the spinal column has the further disadvantage that the
injected substance often breaks into separate smaller globules and
thereby becomes ineffective as a radiopaque agent. Once the
material separates, it is difficult, to recombine the material so
as to effectively conduct radiological study. An additional problem
that is encountered is that when the radiopaque material is
positioned by gravitational methods it is often difficult to
maintain the radiopaque material at the desired location for
sufficient time to adequately expose X-rays and obtain an accurate
study. This is due in part to the natural curvature of the spine,
which promotes rapid flow of the radiopaque material along certain
areas of the spinal column.
It is accordingly an object of this invention to overcome the
aforementioned problems and difficulties of the prior art.
It is still a further object of this invention to provide an
improved radiological diagnostic method which is safer for the
patient, and which can be more effectively utilized by a
radiologist to achieve more accurate studies.
Other objects and advantages of this invention will become further
apparent hereafter from a continued reading of the specification
and study of the attached drawings.
BRIEF SUMMARY OF THE INVENTION
The objects of this invention have been achieved by providing a
radiological diagnostic method comprised of injecting a radiopaque
ferrofluid into the body system to be radiologically studied;
moving the ferrofluid with a magnet to the particular location
desired to be examined, and after the study is completed, removing
the ferrofluid from the body system.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a schematic illustration of a body which is being
radiographically examined in accordance with the method of this
invention. The spinal column of the body is shown in full
lines.
FIG. 2 is an enlarged illustration taken as indicated by the dotted
area 2 of FIG. 1.
FIG. 3 is an enlarged illustration of the dotted area 3 of FIG.
2.
FIG. 4 is an illustration in cross section of a magnet which is
especially useful for employment in the method of the present
invention.
FIG. 5 is an enlarged illustration of the area 5 of FIG 1.
FIG. 6 is an illustration of the removal of the ferrofluid from the
spinal column in accordance with the teachings of this
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In describing the method of this invention, particular reference
will be made to the use of the method of this invention for the
radiological examination of the spinal column in order to
facilitate the explanation of the invention. However, it should be
appreciated that the method of the present invention is not limited
to radiological examination of the subarachnoid space of the spinal
column and can be also used to examine various other areas of the
spinal column and body systems wherein there is a relatively slow
flow of fluids and also systems which have mucous linings. These
systems include among others, the respiratory tract, the upper
gastrointestinal system, the genitourinary tract and the
ventricular system of the brain.
In the method of this invention ferrofluids are used as the
radiopaque contrast means. Ferrofluids are a relatively new class
of fluids. These fluids are commercially available or can be
prepared by known methods. Ferrofluids are colloidal dispersions of
single domain ferromagnetic particles. The ferrofluids as a class
are unique, in that it is possible by inducing a magnetic force to
move the ferrofluids in direct response to the magnetic force. The
magnetic response of the ferrofluids is due to the coupling of the
individual ferromagnetic particles with a substantial volume of a
surrounding carrier liquid. The magnetic force, when applied to the
ferrofluid, attracts the enveloped ferromagnetic particles together
with the associated liquid carrier so that the entire liquid mass
is drawn as a unit by the magnetic force.
The method of preparing ferrofluids is known to those skilled in
the art, however, to facilitate an explanation of this invention
the process will be briefly described. Since most inorganic
magnetic solids are characteristically insoluble in common liquids,
the coupling of magnetic particles with the carrier liquid is
accomplished by using a mordant-like material, which is initially
applied to the particles of the magnetic material. The mordant-like
material, or as it is often referred to as the stabilizer, has the
ability to be both adsorbed onto the surface of the magnetic
particles and also to solvate the carrier liquid. A typical
compound of this type is oleic acid. The ferromagnetic particles
which are used are relatively small being colloidal in size with
diameters in the range of about 10 to 300 A (Angstroms) being most
desirable. It should be appreciated that the term ferrofluid as
utilized in this application is not limited to ferroliquids which
contain iron, but is generic to all fluids which exhibit the above
noted properties including liquids which contain metals other than
iron which can effectively be moved by a magnetic force, such as
chromium.
The selection of the type and amount of the carrier liquid which is
used in the method of the present invention is highly important. In
the manufacture of the ferrofluids, if an excess amount of carrier
liquid is employed or if thereafter additional amount of carrier
liquid is added to the ferrofluid system, a phase separation will
occur which destroys the ferrofluid properties. On the other hand,
if an insufficient amount of carrier liquid is employed in the
manufacture of ferrofluids or if a portion of the carrier liquid is
removed from the ferrofluid, the ferromagnetic particles will
agglomerate and the ferrofluid properties will likewise be
destroyed.
In view of the relative critical balance between the ratio of the
amount of the ferromagnetic particles and the liquid carrier in the
ferroliquid, it is important to select a ferrofluid which will not
be adversely effected when used in the method of the present
invention. Furthermore, the ferrofluids as a whole and the liquid
carrier in particular, must be physiologically inert.
The carrier liquids which are generally employed to make
conventional ferrofluids are for example, water, lower aliphatic
hydrocarbons, and halogenated aliphatic hydrocarbons. It can be
readily appreciated that the ferrofluids having water as a carrier
liquid would be unsuitable in the method of the present invention,
in that, the water normally found in body fluids would blend with
the ferrofluids and thereby dilute the ferrofluids, destroying the
properties by dilution as noted above. On the other hand, certain
commonly used carriers are absorbed by the body, and consequently,
the absorbtion would destroy the ferrofluids by concentration of
the ferrofluids to a point where the ferromagnetic particles would
agglomerate. It has been found, however, that certain classes of
liquid carriers can be employed which have a broad range of
applicability in the method of the present invention. Particular
attention is directed to the halogenated aliphatic hydrocarbons
especially the perfluorinated aliphatic hydrocarbons.
In order to more clearly explain the method of the present
invention, specific attention will be directed to the drawings
which show the method of this invention used for either
radiographically or fluoroscopically examining the spinal column 10
of a patient 12. A sterile ferrofluid is prepared having a suitable
liquid carrier such as a ferrofluid having a perflourinated
aliphatic hydrocarbon liquid carrier and iron ferromagnetic
particles. Sterile procedures are followed as is customary in
conventional lumbar punctures. An 18 gauge lumbar puncture needle
14 is inserted between the third and fourth lumbar vertebrae into
the subarachnoid space 16 of the cauda equina portion of the spinal
column 10. The cauda equina is that portion of the spinal cord
which continues as individual nerves extending beyond the spinal
cord proper 18. The cauda equina is surrounded by spinal fluid 20
and composed of distal nerve ends 22. The bevel 24 of the needle 14
is positioned in about the center of the cross sectional area of
the subarachnoid space of the cauda equina. The stylet 26 is then
removed and a predetermined amount, for example, 3 to 12 cc of
spinal fluid is aspirated from the spinal column 10. A syringe (not
shown) is used to inject approximately the same volume of
ferrofluid 28 as the amount of spinal fluid removed into the cauda
equina area of the subarachnoid space 16. The stylet 26 is
reinserted into the needle 26 and a sterile dressing is placed over
the needle assembly.
As can be seen in FIG. 3, the ferrofluid 28 is hyperbaric as
compared to the surrounding spinal fluid 20 and accordingly tends
to settle to the lower side of the cauda equina in contact with the
arachnoid membrane. The patient is now ready for the X-ray
examination. The X-ray examination can be either a radiographic
examination or a fluoroscopic examination depending upon the
particular type of test results desired, but are usually used in
combination. However, because of the advantages of the present
method, the radiographic method requires less patient radiation
exposure thus increasing patient safety.
As shown in FIG. 1, the patient either during or immediately after
the lumbar puncture is placed on a conventional X-ray table (not
shown), over which there is a moveable X-ray tube 32. A
photographic plate 34 is positioned under the patient directly
below the X-ray camera for radiographic examinations. The
photographic plates are exposed in the conventional manner. In the
event that it is desired to make a fluoroscopic examination, the
radiographic equipment would be replaced with the appropriate
fluoroscopic or image intensification equipment.
Except in somewhat unusual cases, the radiologist is not
particularly interested in the immediate area in which the
ferrofluid 28 is injected. Accordingly, it is necessary to transfer
the radiopaque ferrofluid up or down the spinal column 10 through
the subarachnoid space 16 to the area which is desired to be
studied.
In accordance with the present invention, the ferrofluid 28 is
transferred not by gravity as in the prior art, but is moved by the
use of magnetic force along the spinal column to the location
desired to be studied, and if required, the ferrofluid can be
maintained in this location until the radiological studies are
completed. The effects of moving the ferrofluid can be best seen in
the FIGS. 1 and 5, wherein the ferrofluid 28 has been drawn from
the cauda equina area of the spinal column 10 to the high point in
the spinal curve. This part of the spinal column is generally one
of the most difficult areas to X-ray. However, using the process of
the present invention, the ferrofluid can readily be maintained in
this area until the radiographic examination of the area is
completed.
The magnet which is used to draw the ferrofluid 28 through the
subarachnoid space, can be selected from a variety of permanent and
temporary magnets. The magnets can be made of iron, nickel, cobalt
and alloys of these metals as well as alloys with aluminum such as
Al-Ni-Co, rare earth metals and so forth.
The amount of magnetic force normally required to be applied to the
ferrofluid 28 has been found to be about 5,000 to 10,000 Gauss. An
electrically energized magnet can be used to create this amount of
magnetic energy without endangering the patient, but requires the
use of relatively expensive and bulky equipment which is
undesirable.
It has been found that a highly effective and compact type of
permanent magnet 36 for use in the method of this invention are the
rare earth magnets, and particularly the samarium-cobalt magnets.
These magnets 36 are made from discs 38 of a samarium-cobalt alloy.
The discs 38 are stacked in a suitable container made from a
plastic material. A magnet 36 of this type which is about 1 inch in
diameter and about 5 inches long can produce a magnetic field
strength of up to about 10,000 Gauss which is adequate for use in
the method of this invention. Further, it should be noted, that the
magnet 36 can be held in the hand of the radiologist and does not
require the use of a separate power supply to operate it. Using the
samarium-cobalt magnet 36 the ferrofluid 28 is readily drawn
through the subarachnoid space 16 to the desired position. It
should be carefully noted that the patient 10 is not required to be
moved during the entire procedure.
Furthermore, the ferrofluid 28 can be drawn repeatedly up and down
the spinal column as required without causing any discomfort or
damage to the patient. A very important advantage of this
invention, in addition to the relative mobility of the radiopaque
material within the spinal column, is a fact that the ferrofluid 28
can be held stationary in an area of the spinal column for
extensive studies of the area.
A still further advantage of this invention is that the ferrofluid
28 does not tend to separate like the radiopaque materials
heretofore used. Even if the ferrofluid does inadvertantly separate
into separate sections, it can readily be recombined by drawing the
separate portions together with the magnet.
When the radiographic or fluoroscopic study is completed, the
ferrofluid is removed in a highly efficient manner which was not
heretofore available using the prior art radiopaque materials. As
shown in FIG. 6, the ferrofluid is drawn by the magnet 36 back to
the place where it was initially introduced. In accordance with the
preferred embodiment of this invention the original stylet 26 is
removed, and an insert needle composed of a magnetic metal having a
round, smooth, perforated tip is inserted in place of the stylet
26. When an 18 gauge needle is employed for the initial injection
with an ID 0.033 inches, the insert needle 40 which is inserted
will be at least 21 gauge. At the opposite terminal end from the
tip of the hollow needle 40 there is a hub 42 which includes a lock
44 which engages the hub of the needle 14. The hollow needle 40
likewise includes a hub to which a syringe 46 is attached.
When withdrawing the ferrofluid 28 the hollow tubular insert needle
40 is magnetized with the magnet 36. The ferrofluid 28 is attracted
to the magnetized perforated tip of the hollow needle and is drawn
up the hollow needle with the syringe 46. The insert needle has two
principal functions. Initially, it is made of a magnetizable metal
which assists in the removal of the ferrofluid from the spinal
column. Secondly, it should be noted, that when inserted, the tip
of the insert needle 40 shields the sharp beveled edge 24 so that
the lumbar puncture needle 14 does not accidently puncture the
distal arachnoid and dural membranes during removal of the
ferrofluid. It has been found that as opposed to the conventional
method heretofore used, that in accordance with the method of the
present invention, all of the ferrofluid can be effectively removed
without much difficulty using the process of the present
invention.
As is indicated above, the method of the present invention is not
limited to radiological examinations of the spinal column but can
be used with other body systems wherein there is a relatively slow
flow of fluids or which have a mucous lining. The technique
employed would be modified according to the particular body system
involved. For example, if the ferrofluids were used in place of the
conventional barium compounds for purposes of making studies of the
upper gastrointestinal tract, the ferrofluid would be introduced by
means of a tube or the like which contained a magnetizable element
such as a wire or the like, which would assist in the removal of
the ferrofluid from the gastrointestinal system after completion of
the test. It of course, would be possible to simply allow the
ferrofluid to remain in the gastrointestinal system and be expelled
by the normal bodily function since the ferrofluids employed are
biologically inert. When using the technique of the present
invention with the genitourinary tract the method employed would
generally consist of using a catheter for the purpose of inserting
the ferrofluid into the appropriate organ such as the bladder,
kidneys or the like. The catheter should likewise contain a wire or
the like that can be magnetized, so as to assist in drawing the
ferrofluid toward the catheter upon completion of the radiographic
or fluoroscopic examination.
* * * * *