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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to devices for positioning of medical
instruments such as needles for accurate percutaneous insertion, and more
particularly to devices for such positioning of needles and other medical
instruments in combination with X-ray emissions.
2. Description of the Prior Art
The conventionally and widely used "CAT Scan" device, a computer controlled
X-ray instrument which can provide cross-sectional imaging of body
tissues, is a very powerful modern instrument which has a wide range of
uses. One such use is the precise location of body tissues which are
desired to be accessed, as by use of long, thin needles or other medical
instruments (such as catheters) by percutaneous insertion, for taking
biopsy samples of such target tissues or for further medical treatment
(such as draining abcesses or removing foreign bodies therefrom).
However, currently trial and error methods are used to insert such needles
and medical instruments in response to the cross-sectional images
generated by the CAT Scan device, in order to puncture the skin and reach
the desired target point. This can result in repeated puncturing of the
skin which carries with it the enhanced risk of damage to body organs
adjacent to the target point lying along the path which the needle is
desired to travel. Moreover, many target points may lie too close to vital
nerve or other body tissues, or no safe path may be available to permit
the needle to circumvent vital body organs lying along the desired
puncture path. In such cases, the risk to the patient in reaching the
target point may be so great as to prevent the use of, e.g. needle biopsy,
and further medical diagnosis and treatment might then require exploratory
surgery. This of course entails significant trauma, expense, time and
manpower in conducting the surgery, and also entails added post-operative
time and expense.
Heretofore, no device or method has ben found which alleviates the need for
subjecting the patient to such trial and error needle positioning. Prior
art trial and error methods of acomplishing percutaneous tumor biopsy and
absecess drainage, and the risks associated therewith, are discussed in
"Interventional Radiology of the Abdomen", Joseph T. Ferruci, et al., pp.
124-135 (Williams and Wilkins 1981); "Interventional Radiology",
Athanasoulis, et al., PP. 561-583 (W. B. Saunders Co. 1982); and M. P.
Heilbrun, et al., "Preliminary experience with Brown-Roberts-Wells (BRW)
computerized tomography stereotaxic guidance system", J. Neurosurg. vol.
59, pp. 217-222 (1983), the disclosures of which are hereby incorporated
by reference.
Devices which have been developed for cranial surgery and treatment include
those disclosed in U.S. Pat. Nos. 3,115,140; 3,135,263; 4,294,119; and
4,350,159, and in Russian Patents 441,933 and 764,670. However, these
devices are complex and cumbersome, and are not readily adaptable for use
on body parts other than the head.
SUMMARY OF THE INVENTION
A device is provided which is useful in accurately positioning needles and
other thin, elongated medical instruments intended for percutataneous
insertion through the skin to a predetermined target within the body of a
patient. The device comprises (i) a base, provided at one end thereof with
a vertically disposed support member, (ii) turning plate means movably
affixed to the base and adapted to be tilted in a direction which is
substantially parallel to the plane defined by the vertical support
member, (iii) means for adjusting the tilt angle of the turning plate
means; (iv) needle holding means, movably affixed to the turning plate
means, for removably securing a needle or other elongated medical
instrument thereto and adapted to be tilted along the turning plate in a
plane which is substantially perpendicular to the plane defined by the
vertical support member (v) means for adjusting the tilt angle of the
needle holding means; and (vi) arcuate needle angle indicator means,
provided with a plurality of spaced-apart radiopaque needle angle
indicators along the upper periphery of the arcuate turning plate means
and adapted to provide a visible indication of the needle tilt angle along
the turning plate means when the device is exposed to X-ray emissions, the
balance of said device being constructed of a material which is
substantially transluscent to such radiation.
The needle holding means can further comprise a needle depth measuring
means for indicating the depth to which the needle is to be inserted into
the body cavity, and the base can further comprise screw threaded height
adjusting means for adjusting the height of the base avobe the skin and
for leveling the device thereon. The needle holding means can also be
provided with a longitudinal, vertically disposed radiopaque indicator
line to aid in determining the needle tilt angle.
The device of this invention can further comprise a circular angular
indicator means, adapted to be removably attached to the turning plate
means and needle holding means such that the tilt angle of the turning
plate means and needle holding means can be accurately determined by means
of a rotatable circular angle indicator disk.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1-1A are perspective elevational views of an embodiment of the device
of this invention provided with an offset angle indicator means.
FIG. 1B is an elevational view of a second embodiment of an offset angle
indicator means having a circular angle indicator disk.
FIG. 2 is a perspective, elevational view of the base of FIG. 1.
FIG. 3 is an exploded, perspective view in elevation of the needle holding
means and an associated turning nut and locking nut for positioning the
needle holder, circular angle indicator adaptor and elongated depth gauge
of the device illustrated in FIG. 1.
FIG. 4 is an exploded, elevational perspective view of the circular angle
indicator and adaptor 75 to the needle holding means.
FIG. 5 is a side elevational view of the needle holder illustrated in FIG.
3.
FIG. 6 is an exploded view, in perspective and elevation, of the turning
plate of FIG. 1 and an associated radiopaque arcuate angle indicator.
FIG. 7 is an elevational view of a portion of the reverse face of turning
plate of FIG. 6 and illustrates the gear rail thereof.
FIG. 8 is a perspective elevational view of another embodiment of the
arcuate needle angle indicator.
FIG. 9 is a simplified cross-section of a body part. FIG. 10 is a
simplified top view of the body part of FIG. 9 with radiopaque skin
markers thereon.
FIG. 11 is a cross-sectional view of the body part of FIG. 10 taken along
line B--B', slightly rotated.
FIG. 12 is a simplified elevational view of a device 10 of FIG. 1
positioned above puncture point 120 on the sking of body part 100.
FIG. 13 is a cross-sectional body part view as in FIG. 11 except that a
body organ 140 lies on the needle pathway.
FIG. 14 is a simplified, perspective view of a body part as in FIG. 13
showing a vital organ and target.
FIG. 15 is a simplified perspective view of a device 10 of this invention
used in combination with an offset angle indicator means of this
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIGS. 1-7, one embodiment of the device of this invention is
illustrated which comprises base 14, vertical support member 12, turning
plate means 20, needle holder means, generally indicated at 68, and
arcuate needle angle indicator means 30.
Vertical support member 12 is positioned along one side of base 14 and is
provided with arcuate aperature 17 therethrough, and first arcuate gear
rail 13 above arcuate aperature 17.
Turning plate means 20 comprises supporting, opposing triangular-shaped end
portions 38 and 39, planar mid-portion 92. Turning plate turning means,
indicated generally at 93, comprises cylindrical axle support 35a, screw
threaded member 35, turning nut 36 and locking nut 31.
Turning plate 20 is movably affixed to base 14 by means of pins 63 and 64
which are affixed to the lower portion of each end of plate 20 (and can be
integrally formed therewith) and are each rotatably housed in the
associated pin cavities 19a and 19b in base 14, to permit turning plate 20
to be tilted in a direction which is parallel to the plane defined by
vertical support member 12, namely, in the YY-ZZ plane. The substantially
flat lower surface of plate 20 adjacent to pins 63 and 64 are movably
positioned within channels 19c and 19d of base 14, which should each be of
a sufficient width to permit plate 20 to turn, without binding the
portions of base 14 surrounding cavities 19a and 19b.
At the upper portion of one side 38 of turning plate 20 is provided
cylindrical axle support 35a and screw threaded member 35 which are
adapted to be inserted through aperature 17 of vertical support member 12,
and to be movably affixed to support 12 in a plurality of positions along
the arcuate aperature 17 by means of locking nut 31 and turning nut 36.
Locking nut 31 is provided with screw threads to engage the screw threaded
member 35, and turning nut 36 is sized slightly larger than axle 35a to
permit nut 36 to be turned, and engage the gear rail 13, without imparting
rotational force to axle 35a, on which nut 36 is positioned. Therefore, it
can be seen that axle support 35a should be of a length which is
sufficient to enter aperature 17 and extend therebeyond to permit nut 36
to rest thereon. Nut 36 is provided with gears 37 which are adapted to
mesh with gear rail 13. When so constructed, turning plate 20 can be
tilted in a plane substantially parallel to the plane (YY-ZZ in FIG. 1)
formed by vertical support member 12, and the tilt angle of plate 20 can
be fixed and precisely adjusted by means of gears 37, gear rail 13 and
locking nut 31. For example, when locking nut 31 is loosened slightly upon
member 35, turning nut can then be rotated in the desired direction,
whereupon gears 37 and gear rail 13 act to precisely adjust the tilt angle
of plate 20. Nut 31 can then be again tightened to maintain the selected
tilt angle of plate 20.
The total angular adjustment possible for plate 20 can be set by the length
of aperature 17, and can vary widely, with a total of 160 degrees of
angular tilt (that is, 80 degrees of tilt away from the vertical in either
direction) will be generally sufficient for turning plate 20.
Needle holder means 68 comprises needle holder 40 and removable clasp 50.
Needle holder 40 comprises a longitudinal grooved housing adapted to
receive a needle 70 (or other elongated medical instrument intended for
percutaneous insertion into a body cavity) in a longitudinal groove 45
defined in the front face 43 of housing 40. The needle 70 can be removably
affixed to housing 40 by means of a removable clasp 50 which can be
fabricated from a material and of a size such that the inner sides 65 of
clasp 50 securely grip the sides 41 of housing 40 to hold needle 70 within
groove 45 and to prevent needle 70 from moving, of its own weight,
downwardly when holder 40 is positioned vertically, as in FIG. 1. The
frictional resistance to such downward motion of needle 70 should not,
however, be sufficient to prevent the needle 70 from being repositioned by
application of external force, as by hand, to precisely adjust the
position of needle tip 74 in use of the device of this invention, which is
generally indicated at 10 in FIG. 1.
Clasp 50 can be provided with housing 52 extending outwardly therefrom and
provided with aperature 51 to secure a longitudinal needle depth gauge 60
therein such that the shaft of gauge 60 extends upwardly from housing 52
and remains parallel to needle 70 throughout any adjustment of the needle
tilt angle, as will be explained in more detail below.
Needle holder 40 is further provided with a recessed portion 44 in the
lower portion of inner face 54 of housing 40, and a pin 48 is affixed to
the inner recessed surface of face 54, preferably centrally in such
recessed face. Pin 48 is adapted to be received by pivot cavity 59 in a
pivot structure 58 which is provided centrally in the lower portion of
turning plate 20.
At the upper portion of rear face 54 of housing 40 is affixed a cylindrical
support axle 46 and screw threaded member 47 which are adapted to be
inserted into arcuate aperature 34 in planar mid-portion 92 of turning
plate 20, and to be movably affixed to turning plate 20 be means of needle
holder turning means, indicated generally at 94, which comprises turning
nut 55 and locking nut 57. Nut 57 is provided with screw threads to engage
the screw threaded member 47, and turning nut is sized to rest upon axle
46 and is provided with gears 56 which are adapted to mesh with gear rail
21. Turning nut 55 is sized slightly larger than axle 46 to permit nut 55
to be turned without imparting rotational force to axle 46. Therefore, the
needle tilt angle, which is adjusted by means of movement of needle holder
40 along turning plate 20, can be precisely adjusted in a manner similar
to that described above for adjustment of the turning plate tilt angle
itself. When so constructed, needle holder 40 can be moved independently
of the angle selected for turning plate 20, with needle tilt angles being
adjusted by means 94 along a planar direction which is parallel to the
plane then formed by turning plate 20 (which is the XX-YY plane as
illustrated in FIG. 1 when plate 20 is in the vertical position) and which
is therefore perpendicular to the plane defined by vertical support member
12.
The total angular movement permitted for needle holder 40 can be determined
by the length of aperature 34 and can vary widely, with a total of 160
degrees (that is, 80 degrees away from the vertical in either direction)
being generally sufficient. It will therefore be seen that turning plate
20 and needle holder 40 can be independently positioned to result in a
wide range of possible attitudes of needle 70, relative to the vertical YY
axis.
Upon the upper surface 21 of turning plate 20 is positioned arcuate needle
angle indicator plate 30 which is provided with a plurality of
spaced-apart, radiopaque needle angle indicator marks 32 which are adapted
to give a visual indication of the needle tilt angle of needle 70 when
device 10 is exposed to either visible light and, more importantly, also
to X-ray emissions such as are normally employed in CAT Scan devices of
the prior art. Therefore, indicator marks 32 can be composed of any known
radiopaque material such as barium sulfate, metal iodides, metal alloys
and the like, and plate 30 can be formed from a plastic material, which
contains marks 32 and is otherwise transparent or translucent to such
X-ray emissions. Arcuate plate 30 can be either removably affixed to
turning plate 20 (as shown in FIG. 1, as by means of pins 33 which are
affixed to plate 30 and are adapted to be inserted into associated
aperatures 33a in turning plate 20. Alternatively, arcuate plate 30 can be
formed integrally with turning plate 20 (not shown).
Indicator marks 32 can comprise any convenient shape and can be used in any
convenient number on plate 30. Generally, from about 10 to 50 such marks
32 will be sufficient. Each such mark 32 is preferably separated from its
adjacent marks 32 by a distance which is sufficiently large to avoid
blurring of two or more marks as a result of the resolution of the imaging
device (e.g., X-ray sensitive photographic film) normally associated with
prior art CAT Scan devices. Generally, a separation distance of from about
2 to 4 mm will be sufficient. Similarly, the shape of marks 32 is not
critical, and they may be rounded (as in FIG. 1) or linear. FIG. 8
illustrates linear marks 32a, each of which can comprise the front face of
a radiopaque flat plate extending through the width of the arcuate plate
30a. The precise dimensions of marks 32 necessary to achieve sufficient
radiopacity to permit ready observation of needle angles using a
conventional CAT Scan device will depend on such factors as the particular
radiopaque material selected for use, the shape of marks 32 and other
factors, and can be readily determined by one having ordinary skill in the
art given the present disclosure. Furthermore, the balance of device 10
can be constructed of such known, substantially non-radiopaque materials
as plastics (e.g. Lucite, polyethylene, polypropylene and the like) and
other known such materials of construction.
Referring now to FIG. 1A, there is illustrated an offset angle indicator
means, indicated generally at 95, which comprises shaft 22, connector 11,
angularly adjustable connector 24, linear gauge 27 and circular angle
indicator means 23, which is substantially transparent and is provided
with an angular scale and a weight 28 affixed to the lowest portion of
disk 23, which is rotatably affixed to gauge 27 by means of axle 29 to
permit disk 23 to freely rotate such that weight 28 continues to point
downwardly when linear gauge 27 is tilted from the vertical.
Alternatively, the circular angular indicator can be fixed to linear gauge
27 and can be provided with a weighted, freely rotating pointer 28b,
having a weight mass 28a at its lower end, so that pivoting pointer 28b
will continue to point downwardly when gauge 27 (indicated as gauge 27a in
FIG. 1B) is tilted from the vertical.
Gauge 27 is provided with distance scale markings thereon (e.g., mm) and is
also provided with a center line 96, in the preferred embodiment. The
lower portion of gauge 27 (indicated at 97 in FIG. 1A) is adapted to be
removably secured to nub 26 of adjustable connector 24. Both gauge end
portion 97 and nub 26 are each of a circular cross-section so that their
rounded dimensions facilitate the movement and positioning of gauge 27
thereon. Alternatively, both end portion 97 and nub 96 can be formed to
have a substantially rectangular (preferably square) cross section to
permit accurate positioning of the plane of disk 23 relative to the plane
defined by the shaft 22 and linear gauge 27 (that is, either parallel or
perpendicular to the XX-YY plane as defined in FIG. 1). Connector 11 is
adapted to be removably secured to a nub 18 which is provided at one side
of base 14 along the X-X axis and affixed to the extending portion of pin
63 (which is affixed to plate 20) and mounted thereon so as to rotate in a
direction and in response to the movement of turning plate 20 in adjusting
plate 20 angle, as defined above. (Although not shown, it will be
understood that pin 63 projects through base 14 sufficiently to permit nub
18 to be affixed thereto, as described.) A separate such nub (not shown)
can be provided along the X-X axis on the opposite side of base 14 and
similarly, rotatably affixed to pin 64 of turning plate 20. The angle of
tilt of gauge 27 can be adjusted by loosening a thumb screw 25 to permit
nub 26 to pivot in XX-YY plane (as shown in FIG. 1) to the desired angle,
which can then be observed directly on the angular scale of circular
indicator 23. The selected angle can be maintained by tightening thumb
screw 25. The offset angle indicator means 95 of this invention can be
employed with device 10 of this invention to permit percutaneous insertion
of needle 70 to reach targets which are not otherwise accessible, as will
be illustrated hereinafter.
Referring to FIG. 4, it can be seen that a circular angle indicator 23 can
also be employed to visually indicate, directly, the needle tilt angle of
needle holder 40, by the provision of a suitable nub 66 at the end portion
of screw threaded member 47 of holder 40. Nub 66 then acts to mate with a
connector 75 which is provided another nub 26a, situate at right angle
relationship to the center axis of screw threaded member 47, which is
sized so as to mate in turn with lower end portion 97 of linear gauge 27
(or gauge 27a). By such means, the positioning of needle holder 40 along
turning plate 20, as described above, will cause linear gauge 27 to move
accordingly. Since gauge 27, when positioned upon nub 26a, will lie
parallel to needle 70, the needle tilt angle can be read directly on
circular disk 23 (or 23a, as the case might be).
The method of use of device 10 can be further understood by reference to
FIGS. 9-12. Body part 100 (e.g., the abdomen) can be subjected to X-ray
beams 103, 104 and 105, using conventional methods (which do not form a
part of this invention), to generate cross-sectional images 106, 107 and
108, respectively, using a conventional CAT Scan device (which also forms
no part of the present invention). Image 107 represents a vertical image
plane, image 106 represents a cross-sectional image plane which is
-20.degree. from vertical, and image 108 represents a cross-sectional
image plane which is +20.degree. from vertical. After the desired image
plane angle on the CAT Scan device is selected (which can generally range
from -20 to +20 degrees from the vertical), radiopaque indicator lines
122-126 are marked (or taped) on the patient's skin of body part 100 above
the general area of the target 130. An image is then made which identifies
ouncture point 120 as lying midway between indicators 124 and 125 and
which provides the required needle pathway 111, as shown in FIG. 11. The
scanning plane can be visually projected on the skin by use of the
internal alignment light beam which is a component of conventional CAT
Scan devices. Device 10 can then be placed on the skin with point "O" of
the needle holder located upon puncture point 120, and the axis X-X of
device 10 superimposed with the scanning plane visually projected onto the
skin (which can be marked thereon with a suitable ink, if desired). The
tile angle of the turning plate 20 is then adjusted according to the
circular angular indicator 23 attached to nub 18 as described above, such
that plate 20 is secured (by turning means 93) at an angle which
corresponds to the selected image plane angle (e.g., image plane 103,
which is 3120 degrees from the vertical). If desired, the tilt angle of
plate 20 can be precisely compared to the image plane angle by use of
external alinment light beam, which are also generally provided on
conventional CAT Scan devices and which comprise a thin beam of visible
laser beam which is projected across the skin of body part 100 and
coincides with the direction of the image plane which will result when the
X-ray emissions of the CAT Scan device are activated to generate the
desired image. The tilt angle of the needle holder 40 is then adjusted
according to the angle ".theta." of the needle path 111 to the horizontal
line X"--X' in FIG. 11 (e.g., -80 degrees from the horizontal) which is
provided by the CAT Scan device's image. An imaging scan can then be taken
and the relationship between target point 130, puncture point 120 and
device 10 accurately established, such that a line connecting points 120
and 130 can be extended to intersect with the arcuate plate 30, thereby
permitting observation of the required needle tilt angle by means of
radiopaque marks 32 which appear on the cross-sectional image thus
obtained. The needle tilt angle can then be precisely adjusted by movement
of the needler holder 40 as described above by operation of turning means
94. Then, the depth from skin puncture point 120 to target 130 can be
ascertained from the image (as in FIG. 11), and the needle depth gauge 60
can be employed (by suitable positioning of slideable tabs 69a and 69b) to
mark the corresponding depth. Therefore, tab 69a can be placed adjacent to
a defined section of needle 70, for example, at the lower edge of shaft
connector 72, which connects needle 70 to a conventional plunger (not
shown), and tab 69b can then be placed below tab 69a at a distance which
corresponds to the desired needle insertion depth. Needle 70 can then be
inserted through the patient's skin at 120 along path 111 by operation of
the plunger, to the predetermined depth marker 69a to reach target 130. If
desired, base 14 can be taped to the skin for stability.
To permit the thus-inserted needle to be used for exchanging and insertion
of other, larger elongated medical instruments along path 111, for the
desired tissue sampling, observation or treatment, base 14 of device 10 is
preferably provided with an enlarged center opening, as defined by walls
15 in the embodiment illustrated in FIG. 1, to permit device 10 from being
removed from the patient's skin without disturbing (or requiring the
removal of) the thus-positioned needle 70. Preferably, base 14 has a
substantially discontinuous outer periphery along one side thereof, as
shown in FIG. 1, adjacent to needle holder 40, to permit more fascile
removal of device 10 after insertion of needle 70.
It has been found that the foregoing device 10 and above-described method
permit accurate and rapid determination of needle path 111 and insertion
of needle 70, and this invention has resulted in saving of as much as 75%
or more of the time needed using prior art needle biopsy methods.
Referring again to FIGS. 1 and 2, radio opaque linear marks (e.g., 82-85
and 88) are provided on the upper surface of base 14 at diagonally
opposing sides thereof. Each set of such marks (e.g., marks 82-85) should
comprise at least 2 to 3 such marks in decreasing lengths, and the
difference in length of each successive mark in a given set should be
constant and equal to the distance by which the longest such mark (e.g.,
mark 82) in each set is separated from the center axis (X-X) of turning
plate 20. In this manner,if the patient moves slightly after turning plate
20 is precisely aligned with the desired image angle, one or more dots
will appear when the image is actually obtained, at one side of puncture
point 120. The number and position of these dots (illustrated at 82 in
FIG. 12) will indicate the direction and distance of the movement away
from the planned image plane. For example, in the image taken in FIG. 12,
if the constant length difference was 5 mm., then the appearance of two
dots to the left of the puncture point 120 indicates that the patient has
moved about 10 mm (and not more than about 14 mm) in a direction which is
into the paper as viewing FIG. 12. Had these dots appeared on the opposite
side of point 120, it could be concluded that the movement occurred in a
direction which is out of the plane of the paper, toward the viewer, as
viewing FIG. 12. In this manner, the scanning plane can be adjusted by
moving the surface (generally a slidable table) on which the patient is
positioned, in a direction and for a distance sufficient to compensate for
this unexpected slight movement.
Referring to FIG. 13, there is illustrated a cross-sectional image scan of
body part 100a showing a target body object 130a, vital body organ 140 and
a plurality of linear radio opaque indicator skin markers (e. g., 122 and
126). Similarly to the scan shown in FIG. 11, a projected needle path 111a
can be defined between puncture point "O" and target 130a. However, in
this case a vital body organ 140 would be punctured if path 111a were
followed. Use of an offset angle indicator 95 of this invention, in
combination with a device 10, will now be described, having reference to
FIGS. 14 and 15.
In the image scan of FIG. 13, shown in perspective as scan 89 in FIG. 14,
body organ 140 lies in a direct line from desired puncture point "O" to
target 130a. A second scan is taken, using the same image plane angle,
which can be accomplished by conventional means, as by moving the patient
linearly and maintaining the angle settings of the imagining device that
were previously selected. The second scan image 99 results in a new
puncture point "P", and it is seen that no vital organs lie in the path of
P to 130a. A straight line is drawn on the patient's skin to connect O-P,
and device 10, having offset indicator means attached thereto, is
positioned above "P", with the needle point 74 being placed upon "P". The
turning plate 20 is aligned with its X-X axis coinciding with the line
formed by O-P. The tilt angle of the turning plate 20 is then adjusted, as
is the tilt angle of the needle holder 40 as described above (e.g.,
according to an angle ".theta." between line 111a and horizontal line
X'--X' as shown in FIG. 13. The length of shaft 22 is chosen such that the
distance from "P" to the center of connector 24 is equal to the length of
line O-P. The circular indicator 23 is positioned (by means of selecting
the relationship of nub 26 and lower end portion 97) such that the plane
of indicator 23 is in the XX-YY plane. The angle of gauge shaft 27 is then
adjusted as described above such that it corresponds to the angle of the
image plane employed to obtain the scans 89 and 99 (which is assumed to
have been vertical in FIGS. 14 and 15). Since O-T, the depth from "O" to
the target 130a is known from scan 89, the same distance from X-X axis
along gauge 27 can be measured, and point T' marked thereon. The needle
tilt angle O'PT' along turning plate 20 can then be readily adjusted, by
moving needle holder 40 until needle shaft 70 intersects point "T'" on
shaft 27. Since line O-P equals P-O', and O-T equals O'-T', it can be seen
that the puncture distance P-T equals P-T', which is the distance from the
point 74 to the intersection of needle 70 with gauge shaft 27. A
confirming scan can be made to ensure that the thus-inserted needle 70 is
on target.
If desired, screw threaded member 35 (similarly to nub 66 illustrated for
needle holder 40 in FIG. 3) can be provided with a nub (not shown) at the
end thereof which is adapted to mate securel albeit removably, with a
connector 75 such that a circular angular indicator means 95 can be
attached directly to member 35 to directly indicate the tilt angle of the
turning plate 20.
In the embodiment of FIG. 1, the screw threaded height adjusting means
comprises screws 3 and 5 which are positioned in the corresponding
aperatures 2 and 4, respectively, in base 14, and screw 7 which is
positioned in aperature 6 and which cooperates with thumb nut 8 (housed in
a recessed slot (not shown) in base portion 16) to permit precise
adjustment of the base height and level. If desired, an adhesive surface
can be provided upon the bottom surface of each such screw 3, 5 and 7 to
assist in stabilizing the device 10 on the surface of a patient's skin.
The foregoing description has been given for the purposes of understanding
only, and it will be understood that no unnecessary limitations should be
read therefrom, as some modifications will be apparent from the above
description.
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