CA2129015A1 - Device for guiding a puncture device and its use with a hand-held appliance for locating blood vessels - Google Patents

Abstract

Abstract Apparatus for Guiding a Puncturing Device and its Use in a Hand-held Device for Locating Vessels The apparatus (40) serves to receive a puncturing device (20). It comprises a detector (10) to determine the location and/or type of a vessel lying beneath the skin. The detector (10) is connected to analyzing means, the result of which is shown by an indicator. When the indicator indicates the position of the guiding apparatus suitable for puncture, the puncturing device is introduced into the vessel to be punctured. (Figure 8)

Description

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Apparatus for Guiding a Punctu~ing Device and its Use in a ~and-held Device for Locating Vessels Field of the Invention The present invention relates to an apparatus for guiding a puncturing device such as a syringe or a catheter as defined in the preamble of claim 1. Such an apparatus is disclosed in EP 0 467 291 Al as discussed below.

Backqround of the Invention In medicine, examination and treatment of patients very often require the puncturing of vessels such as veins lying beneath the skin. When taking blood samples or administering medication, syringes are generally employed to puncture, for instance, veins in the arm region. For other purposes, e.g., heart examination, catheters are inserted into veins. This requires the physician to determine the location of the vessel to be punctured, for example, by palpating potential body sites and feeling for the vessels lying beneath the skin~ This method is very inaccurate and involves the risk that either the vessel to be punctured might be missed altogether or another vessel, e.g., an artery might be hit although a vein should have been punctured when taking blood samples. If an artery is punctured, there will be the danger of extensive bleeding.

There have been known devices that can be employed in artery or vein examinations, for example, in order to detect vascular diseases or vasoconstriction. Such devices operate on the basis of ultrasonography, i.e., using ultrasound with frequencies in the range of >20kHz. A transducer allows ultrasound waves to be transmitted to body sites and reflection to be measured. In this fashion border layers in ~,~ `~' ~ :`

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the tissue as well as vessels such as arteries or veins can be examined. In blood it is primarily erythrocytes that reflect sound waves. Part of the transmitted energy is reflected toward the transducer and is available for analysis.

Doppler sonography especially allows movements such as the movement or direction of the blood flow to be observed. This method utilizes Doppler effects and measures the shift in frequency of the received signal resulting from the movement of the erythrocytes present in the blood. Depending on the direction and rate of motion, a particular Doppler shift is achieved so as to allow that venous and arterial blood, one flowing toward the heart and the other flowing away from the heart, can be differentiated. A further possibility of distinguishing between arteries and veins is found in that the pulsatile arterial blood flow leads to a periodic increase and decrease of the Doppler shift in the frequency spectrum. By contrast, the slow, almost steady blood flow in the vein leads to a nearly constant frequency shift.

Depending on the type of device, sonography of the veins enables the physician to determine the flow direction, flow rate and depth of the vein, and the pulse rate, to diagnose various venous diseases and to examine the structure of the tissue (density) as well as indirectly determining blood pressure.

DE-OS 19 27 868 discloses an apparatus for accurately and quickly localizing blood vessels and for reliably inserting an injection needle into such vessels. Said apparatus comprises an ultrasound system directly in the region of the movement axis of the injection needle on the skin or near the tip of the needle. Said system is composed of at least one detection transducer supported by support means and connected to a radio frequency transmitter and a Doppler device. Said detection transducer can be preceded by a , , ,,;. ! ~: ~ ! ~ ' : . ' ' ' 2129~1~

coupling device contacting the skin and conducting the ultrasound. Alternatively, the detection transducer can be arranged in the interior of the injection needle next to the movement axis or so as to surround the movement axis. In the two last-mentioned alternatives the detection transducer or a part of its support means can be provided with a device for guiding the injection needle in the vessels once they have been detected.

A prerequisite for proper functioning of the known apparatus is said to be that the detection system and the injection needle are spatially arranged so as to allow them to interact on the skin at the time of puncture. Prior to injection, it is therefore absolutely necessary that both the injection needle and the detecting transducer or the preceding coupler be sterilized. Upon injection the detection transducer is inevitably polluted, thus requiring sterilization prior to re-use.

DE-OS 21 48 700, which is a supplement to the above-mentioned patent application, discloses an apparatus combined with a depth indicator. Said depth indicator operates on the pulse propagation time principle and enables the depth of the vessel and the depth of the puncture of the needle to be recorded. For this purpose, a path scale which can be read in relation to the detection oscillator must be provided in the region of the front end of the injection needle.
.
The aforementioned apparatuses have the drawback that the user needs both hands for handling. Once the vessel has been detected, the support means must be held in one hand while the injection needle is guided with the other hand through the guide bore of the support means toward the detected vessel.

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DE-OS 23 14 367, by the same inventor as the two above-discussed patent applications, relates to an ultrasound Doppler applicator which is provided with specific means for attaching the ultrasound detection transducer to the injection needle and permits single-handed usage. Prior to detection of the vessel, the tip of the injection needle is inserted until it reaches approximately the application surface of the detection oscillator and once a blood vessel suitable for injection is found, some frictional or elastic force must be overcome to insert the injection needle through the skin into the tissue toward the vessel. To improve ultrasound coupling, a coupling gel may be provided between the application surface of the detection oscillator and the skin. Said known apparatus has a very complicated construction and has the drawback that the coupling gel in the region of the puncture site may penetrate the tissue or vessel along with the injection needle. Moreover, the detection oscillator cannot be detached from the needle.

DE-OS 24 18 426 discloses an apparatus for simplified puncturing of the arteries or veins by using the Doppler ultrasound probe. Said apparatus comprises a needle guide top part with a first bore to receive the Doppler ultrasound probe and a notch on one of its sides to guide the puncture needle. The ultrasound direction forms one plane with the puncturing direction, and the point of intersection of the two directions is found deep down in the vessel in the tissue. The guide of the injection needle is inaccurate due to the small supporting surface of the needle guide top part and requires two-hand handling by the user.

The above-described apparatuses share the drawback that the actual syringe, the probe as well as the receiver must be sterilized or provided in a sterile packing prior to use.
For one thing, this requires extra effort and for the other, the electrical components such as the detection oscillator may be damaged.
:-. --212901a To avoid such drawbacks, DE-A1 39 09 140 suggests a syringe for Doppler sonographically aided puncturing in which the transmitter and the receiver are arranged in the piston of a commercial syringe. It is further suggested that a small amount of physiological salt solution contained in the syringe be injected in order to achieve direct coupling of the ultrasound with the soft tissue surrounding the vessel to be detected. In this known apparatus the piston must be sterilized after each use and packaged in a sterile one-way bag. It is also necessary for coupling of the ultrasound waves that the nèedle be introduced through the skin into the vicinity of the vessel to be localized in order to detect especially vessels lying far beneath the skin.

DE-AS 29 06 474 discloses an ultrasound transducer probe comprising a carrier having a base surface to be placed on the body surface of the patient, a plurality of ultrasound transducer elements provided sequentially on the base surface, a cable to connect the individual transducer elements to an electric transmitter/receiver portion of an ultrasound diagnostic device and a needle guiding block removable from the carrier. There is provided in the needle guiding block a needle guiding slot with a wide aperture on the upper needle inlet surface and with a taper towards the base surface. Furthermore, there is provided in the needle guiding block a slot substantially perpendicular to the guiding slot for the guidance of the needle out of the carrier and out of the needle guiding block.

This ultrasound transducer probe is to ensure that the guide surface be sterile for a sterilized needle to be introduced into the body. To further avoid the entire ultrasound transducer probe from having to be sterilized again prior to use, the support and the needle guiding block insertable therein form separate units. Prior to use, only the guiding slot portion (needle guiding block) is appropriately sterilized or utilized as a disposable unit packed under aseptic or sterile conditions. The carrier, which is never in direct contact with the needle, can be disinfected by using, e.g., alcohol.
DE-OS 25 53 404 discloses a surgical device comprising an ultrasound detector using an ultrasound transducer or a group of ultrasound transducers to connected to an analyzer for localizing any body site to be punctured. The ultrasound transducer elements are provided at the front end of a casing additionally comprising a puncturing device adjustably provided thereon by means of a support.
In a preferred embodiment a water-filled rubber bubble useful in transmitting ultrasound may be provided in the front part of the transducer. Thus, the commonly used coupling gel may be omitted.
This known device has the disadvantage that the entire apparatus must be sterilized if it is to be used under sterile conditions.
US-A-4 ~77 033 discloses a body for an ultrasound detector comprising a through hole parallel to the detector to permit introduction of a cannula. The wall thickness at the front end of the body is reduced and this area forms a window for ultrasound coupling.
EP O 467 291 A1 discloses a needle guide for assembly upon an ultrasound imaging transducer by spring means. A sterile protective cover which is held in place by spring means is stretched over the nosepiece of the transducer. Prior to use, an acoustic coupling gel is first applied to the transducer face, the sterile protective cover stretched over the transducer and the needle guide placed on the transducer. Then a coupling gel is applie~ to the outside of the protective cover at the transducer face.

This known device has the disadvantage that the sterile protective cover takes the form of a bag stretched over the face of the transducer, possibly causing the area around the face of the transducer to become folded. Also, a coupling gel is used between the face of the transducer and the 212901 ~

sterile protective cover, possibly leading to air bubbles being enclosed in the coupling gel when the protective cover is applied, thereby preventing penetration of ultrasound waves. Furthermore, there is the danger of the coupling gel applied to the outside of the sterile protective cover entering the introduction site along with the injection needle. In addition, this device comprises several components, complicating its assembly upon the transducer.

CH 676 787 A5 discloses a puncturing device for puncturing blood vessels comprising a casing with a slidable support for a syringe provided on one side and a tubular carrier for a probe head of a transmitter/receiver arrangement of an ultrasound system provided on the opposite side. The casing contains an electric circuit which is required for the ultrasound system to function and which comprises all operating elements, power supply means and acoustic signal transmitters. The probe head is held in place by the carrier through plug-type connection, allowing said head, at any time, to be replaced by another head having, for instance, other ultrasound transmitters. The probe head comprises a longitudinal slot wherein the needle of the syringe is held in place practically without being touched by the user.
However, said needle is guided when the slidable support is moved towards the needle axis. -~

The casing may be covered with a sealing compound at its front end, said compound serving as acoustic coupling substance for ultrasound waves. At its flat back side, the sealing compound borders on two flat ultrasound transducers, one acting as the transmitter and the other as the receiver.
The transducers are electrically connected to the plugs at ~ -the bottom of the probe head. In order to achieve focusing of the ultrasound waves, the sealing compound can take the form of either a convex lense or a concave lense. These lenses may be made of polymers, e.g., araldite, silicone or rubber.

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-- 212901a This known puncturing device has the disadvantage that the entire arrangement must be sterilized to allow use under sterile conditions. Sterilization is time-consuming and incurs both material and personnel cost. In the meantime, the device will not be available.

It is apparent from the above discussion of the prior art that there is a need for an apparatus for guiding a needle, a catheter or other puncturing device which can be handled single-handedly and which allows detection of a puncturing site by ultrasound, while ensuring sterile conditions at the injection site without requiring sterilization of all parts prior to re-use of the apparatus.

Obiects and Summarv of the Invention The object underly-ing the present invention is to provide a guiding apparatus for accurately localizing vessels lying beneath the skin, especially veins, by using an ultraqound detector and for accurately guiding a puncturing device such as a syringe or a catheter- to the vessel to be punctured, ensuring that sterile conditions prevail during the puncturing process.

A further object underlying the present invention is to provide an apparatus which may be used single-handedly and which allows controlling of the puncturing device, while ensuring sterile conditions at the injection site without requiring sterilization of the detector prior to re-use of the apparatus.

This object is achieved with a guiding apparatus having the features of claim 1.

The guiding apparatus of the invention enables handling of both the casing with the detector attached thereto and the :

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puncturing device with one hand. First, the puncturing device is arranged on the casing such that the front end of the puncturing device does not protrude beyond the front end of the casing. To find the location and direction of a vessel lying beneath the skin to be punctured, the guiding apparatus with a gel pad provided at the front end of the casing is placed on the respective body site and the position and direction of the guiding apparatus is changed until the detector indicates a suitable position for puncturing. Then the puncturing device such as, e.g., a syringe or a catheter is shifted with one hand toward the vessel to be punctured along the guide surface.

The apparatus of the invention has the advantage that the detector does not contact the body site to be punctured directly. Instead, the detector is entirely surrounded by a casing, and there is a gel pad for ultrasound coupling between the detector and the body site to be punctured. This has the advantage that merely the gel pad and perhaps the casing must be sterilized in order to ensure sterile conditions at the body site to be punctured.

In a preferred embodiment of the present invention the casing is a slip-on cover which can be attached to and detached from the detector. In an alternative embodiment the front end of the slip-on cover comprises the gel pad. Thus, this slip-on cover functions as an adapter, which means it is possible to employ different puncturing devices in conjunction with a commonly usable detector. For this purpose, a variety of slip-on covers, each adapted to the puncturing device in size and shape, can advantageously be used in conjunction with the universal detector. It is preferred to design the slip-on cover with the gel pad attached thereon as a single-use piece. This has the advantage that, for example, one sterilized slip-on cover may be used for each individual puncturing operation, thus ensuring sterility at the site of puncture.

212901 a Preferably, the slip-on cover is open at its rear end, and the detector is pushed into the hollow space through said opening until coupling is achieved and until the ultrasound waves emitted from the detector are transmitted to the body site to be examined substantially without attenuation and the return signals can be received. Either the front end of the detector is in direct contact with the gel pad, or the front end wall of the casing is situated between the front end of the detector and the gel pad, with the casing being made of a material permeable to ultrasound waves.

In the embodiment described above the gel pad is preferably fastened to the front end of the casing by adhesion or welding. If desired, a large portion of the gel pad is connected to the front end wall of the case or along the region adjacent to the contours of an aperture at the front end.

More preferably, a dimensionally stable gel pad produced from an ultrasound-permeable material is used. Such a material is disclosed, for example, in EP-A 0 211 482. This material is a hydrogel having a water content of more than 90% by weight. The gel pad is fitted in an aperture at the front end of the casing. More specifically, the gel pad is mechanically held in place, preferably by means of grooves in the gel pad and edges at the aperture. Other mechanical fastening means are also possible. When the detector in the casing is in its final position, the ultrasound head of the detector is in direct contact with the rear side of the gel pad ~i.e., without a wall lying inbetween). The gel pad thus ensures optimal coupling between the ultrasound head and the body site to be examined. The detector in its final position can be fixed in the casing by grooves provided at the detector and corresponding edges provided at the casing.

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In an alternative embodiment the gel pad is preferably made of a thin sheet and a coupling gel contained therein, is entirely permeable to ultrasound waves and has a high ultrasound conductivity. Thus, the guiding apparatus can advantageously be positioned so as to form different angles with the body site to be punctured, thereby ensuring that there be a connection between the detector and the body site to be examined to conduct ultrasound waves. In this embodiment a large portion of the gel pad contacts the body site to be examined and may adapt to uneven sites, if any, and the slanted position of the guiding apparatus. The front side forms an angle of 30-60 (45) with the ultrasound axis, thus facilitating the slanted entry of the ultrasound into the tissue which is required for determining the Doppler effect.

In a particularly preferred embodiment of the invention the guide surface is formed by an elongate groove or by a channel which is adapted to the puncturing device in size and shape. In particular, the width and depth of the groove is such that the puncturing device protrudes at least partially into the groove and is guided thereby laterally.
This has the advantage that the puncturing device is placed on or in the groove when the guiding apparatus is held in one hand and, for example, the puncturing device is held with the thumb and is slidable when the guiding apparatus is grasped with one hand. The cross section of the groove is preferably such that from a top view its width decreases as depth increases. Preferably, a circular cross section should be used. Thus, a puncturing device having a round cross section, for example, can be supported by the groove.

The puncturing device is preferably a syringe with a hollow needle, a body and a piston, with the body being slidably guided at the guide surface. A further embodiment comprises in the region of the front end of the slip-on cover a support preferably having a V-shaped notch wherein the 12 2~2901~

needle of the syringe is slidably guided. This has the advantage that both the syringe body and the needle are supported laterally.

The height of the support, the dimensions of the elongate groove and their position in relation to each other should preferably be adapted to the type and size of the syringe to be used such that both the syringe body and the needle contact the respective guide surfaces. This permits accurate guidance of a particular type of syringe, e.g., the center or off-center arrangement of the needle based on the bottom of the syringe body.

Alternatively, the aforementioned groove can be replaced by two webs to guide the syringe, thus enabling the syringe handle ~generally having a larger diameter than the body of the syringe) to be moved freely. The two webs can also be used to guide a slide in which the syringe body is nipped.
This slide would enable the use of syringes of different sizes comprising a constant-type slip-on cover. Only the slide serving as an adapter would have to be selected accordingly. For simplicit-y, the syringe body is placed directly onto the guide formed by the webs. The length of the webs is such that their protruding ends do not obstruct the movement of the syringe. In the simplest case the length of the webs is smaller than the length of the syringe body.
In such an embodiment the front end of the casing is provided with a needle guide in the form of a slot.
Preferably, the slot is formed by two swivelling flaps spaced apart. The flaps can be swivelled, for example, by means of a film hinge in a manner similar to a swinging door so that, if desired, the joining piece of the injection needle can also be guided through the slot to ensure that the needle penetrates the skin as deeply as possible.

The slip-on cover preferably has an elongate shape and its cross section tapers off in the front part toward the front -` 212901~

end. If the casing is cubic, the two lateral surfaces will preferably be slanted towards the center and the bottom will be inclined upwardly. The upper surface with the guide surface arranged therein forms one plane. The upper surface, the bottom and the slanted lateral surfaces end in a front surface at the front end of the casing which preferably forms an angle of 50-85 relative to the axial direction of the puncturing device. The lateral surfaces and the bottom preferably form angles of about 25 and about 16, respectively, based on the axial direction of the puncturing device. This embodiment permits that the body site to be punctured is covered only in the region of the front end which is reduced in cross section relative to the casing and that in particular the site at which the puncturing device penetrates the skin is readily visible.

In a further embodiment of the slip-on cover the bottom part may be flat and the guide of the puncturing device used (e.g., a syringe) may be slanted at an angle of 10-20 relative to the longitudinal axis of the device. Thus, the injection needle enters the sphere of influence of the ultrasound shortly after perforating the skin. The cover is shaped in such a way that it can be easily grasped with one hand and that the puncturing device is fixed on the guide.
For more complicated measures (e.g., placement of a vein catheter), the device can simply be detached after the vein has been located in order to leave enough space for any required manipulation. The material of the cover is made of light-permeable plastic (preferably polypropylene) which allows an unobstructed view of the display of the internal analyzing means. ~ :

The cover is adapted to the detector in terms of its size and shape and encloses said detector entirely. Further, the rear side of the cover is provided with a lid which also covers the rear side of the detector so as to keep it sterile. In a preferred embodiment the sealing lid in the 212901~

region of the upper edge is coupled with the rear side of the cover by means of a double hinge. This double hinge enables the sealing lid to be opened completely and swung out towards the upper surface of the cover. To completely seal off the interior of the cover, the sealing lid has a circulating edge which snaps shut with a corresponding projecting part at the rear side of the cover when closed.
At the opposite side of the double hinge, there is arranged a bracket to allow reopening of the lid. If desired, the lid can also be arranged at the bottom part and/or coupled therewith by means of a single hinge.

In a further embodiment of the invention the slip-on cover comprises at the rear end an extendable tubular cover which can be extended beyond the rear end of the detector, for example, to protect wires connected to an external data processing unit. Said tubular cover may take the form of extendable bellows, for example.

According to the invention, the guiding apparatus is used in combination with a hand-held device. This device comprises a specifically adapted ultrasound measuring device. It is preferred that the outer dimensions of the ultrasound measuring device be adapted substantially to the hollow space in the guiding apparatus. Due to its small size and low weight, this combination makes single-handed usage possible.

The ultrasound measuring device preferably comprises at least one transducer which preferably serves both as a transmitter and a receiver. The transducer is arranged such that the ultrasound waves are transmitted substantially in the same direction in which the puncturing device is aligned axially. Preferably, the transducer is provided directly beneath the guide surface of the puncturing device.

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The geometry of the transducer is such that the ultrasonic beam has an essentially homogeneous cross section of about 2 x 8 mm in the region between the skin surface and a depth of 40 to 50 mm. The cross section may vary within the range of 1 to 2.5 x 5 to 10 mm. This enables alignment of the rotational axis of the detector with the flow direction of the vein. The reflected signal is greatest when the large axis of the elliptic ultrasonic beam is parallel to the vessel.

In a further embodiment of the invention two transducers are provided beneath the guide groove, one being substantially parallel to the axial direction of the puncturing device and the other being slanted relative to the axial direction of the puncturing device. The effective lines of the two transducers are aligned such that they are spaced apart at a particular distance deep down in the vessel to be punctured.
Thus, it is possible to accurately determine the position and the flow direction of the vessel to be punctured.

The transducer is constructed in such a way that the ultrasonic beam emitted therefrom has an elliptic rather than a circular cross section. The great cross section of the ellipse is perpendicular to the longitudinal axis of the device. The design of the ultrasonic beam as an ellipse causes additional information to be gathered on the flow direction of the target vein. If the long axis of the ellipse is alligned so as to be parallel to the flow direction of the vein, a larger portion of the ultrasonic beam will hit the center of the vessel. Among others, this will cause the intensity of the reflected ultrasound portion to increase with the largest shift in frequency. This is to enhance targeting accuracy in enabling the device to be aligned with the flow direction of the vessel.

The puncturing axis and the ultrasonic cone axis intersect at an angle of 10-20. This and the fanning of the 16 212901~

ultrasonic cone in the longitudinal axis help correct parallax errors; the puncturing axis lies predominantly in the region of the ultrasonic cone.

In a further embodiment of the invention the detector comprises two transducers (two receiving crystals) and a transmitter. The axes of the prime sensitivity of the two receiving transducers are aligned either so as to be parallel to each other and spaced apart at a small distance (5 to 10 mm) or so as to be slightly divergent. Comparative measurement of the signals received shows whether or not the detector is aligned so as to be parallel to the flow direction of the vessel~ In this case, too, the ultrasonic beams have a width of about 2 mm and a length of about 5 mm.
The axis of the effective direction of the ultrasound head is inclined at an angle of 10 to 20, preferably 15 to 17, relative to the axis of the puncturing device. This angle may have to be adapted to the nature of the puncturing device.

Preferably, the ultrasound measuring device operates on the basis of sonography, i.e., -using ultrasound in the range of 1 to 30 MHz, most preferably 6 MHz or 10 MHz. Ultrasound waves are introduced into the sites of the body to be examined and the reflected portions are measured and analyzed. From the propagation time of the reflected portions, for example, the depth of any vessel lying beneath the skin can be determined.

Most preferably, the Doppler ultrasound effect is utilized to identify the vessels. Thus, it is possible to readily distinguish especially arteries from veins so as to avoid unintentional puncturing of an artery. For the detection of a vein, a continuous ultrasound signal having a frequency of 8 MHz will be emitted. The portion of the ultrasound reflected by the blood flow undergoes a frequency shift corresponding to the flow direction and flow rate of the 212901~

blood. This frequency shift can be represented acoustically or optically.

In an alternative embodiment of the invention the transducer is connected to a transmitter via a transmitter/receiver switch. The transmitter optionally operates in a continuous or pulsed mode. In continuous operation the Doppler shift is preferably measured, while pulsed operation is used for depth measurement, thereby carrying out propagation time measurements.

The transmitter preferably has a pulse shaper, at the output of which, for example, an RF pulse with Gaussian distribution is generated. The pulse shapér allows the transmitter pulse to have a narrow frequency spectrum. The transmitter preferably has a pulse shaper which amplitude-modulates radiofrequency oscillation with a defined envelope curve. Suitable shaping of the envelope curve gives the transmitter pulse a narrow frequency spectrum with a still acceptable deformation in the time region. A possible curve shape is the Gaussian curve.

The ultrasound measuring device comprises analyzing means which can optionally be designed as an analog receiver or a digital receiver using the audiofrequency or radiofrequency method. In any case the signal received from the transducer is preferably regenerated by means of a low-noise pre-amplifier, if desired, a subsequent band pass filter, the center frequency of which corresponds to the transmitter frequency, and a further amplifier with preferably predetermined amplification in the range of +60 to +90 dB.
Preferably, there is provided at the input some receiver protection in the form of an amplitude limiter.

In the embodiment comprising an analog receiver or digital receiver using the audiofrequency method, the thus pre-amplified and bandlimited received signal is supplied to a 18 212901a mixing device, e.g., a ring mixer which mixes same with a reference signal from a local oscillator and generates an audiofrequency signal. The audiofrequency signal is filtered out by means of a subsequent low-pass filter having a corresponding cut-off frequency. In an analog receiver the output signal of the low-pass filter is indicated after a controlling and amplifying step, for example, by output via a loudspeaker.

In a digital receiver the output signal of the low-pass filter is converted before and after a controlling and amplifying step from analog to digital and analyzed in a signal processor in terms of frequency shift and/or propagation time and then the result is indicated.
Preferably, the frequency spectrum of the received signal is analyzed either by FFT or multiple band pass filtering. The frequency maximum and the intensity of the received signal is indicated via a chain of optical signal transmitter (e.g., LED). Assuming an essentially laminar flow in veins, the highest flow rate is expected to be found in the center ~
of the vessel. ~ ;

In a further embodiment of the invention the obtained data are analyzed using fuzzy logic for typical patterns in veins centrally exposed to ultrasonic waves and the probability of hit is indicated.

In the embodiment comprising a digital receiver using the radiofrequency method the received signal is converted directly from analog to digital and analyzed in a signal processor with DMA (direct memory access) logic or FIFO and indicated.

The embodiment comprising an analog ultrasound Doppler receiver is the most inexpensive means of analyzing electronics. An estimation of the Doppler maximum is possible and therefore useful in localizing a vessel. The , , ;, , ~ ~ , , "",,,, ,~"",~ ",, ~

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embodiment comprising a digital receiver using the radiofrequency method offers a great variety of possibilities regarding received signal analysis and is therefore more accurate.

An acoustic and/or optic indicator is used to indicate the suitable location and position of the guiding apparatus for the desired puncture. There may be separate indicators to indicate the type of vessel, on the one hand, and/or the location of the vessel, i.e., its flow direction and depth, on the other. In the case of an acoustic output, the frequency of the local oscillator should preferably be equal to the transmitter frequency so as to avoid that the received RF carrier generates disturbing acoustic beats.

At the top part, there are two chains of light displays (LED) to indicate the position of a vein or artery.

Through the numerous illuminated elements, the light chain indicates the maximum of the Doppler shift as measured. This can be coupled with a peak-hold mechanism for better recognition. The intensity of the light may also indicate the intensity of the received signal. - -~
' :'"~-, Preferably, the light-emitting diodes protrude from the top part of the detector. In this case the cover is provided with outwardly protruding protuberances which also serve the purpose of fixing the cover to the detector in an axial posltion. ~

The guiding apparatus of the invention enables medically ~-trained personnel such as physicians or nurses to accurately determine the location of a vessel lying beneath the skin to be punctured, to even accurately localize veins lying deeply beneath the skin (non-palpable veins) and to reliably guide the puncturing device such as a syringe or a catheter to the vessel and to puncture same.

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The apparatus of the invention facilitates the manual puncture of various veins such as "Vena jugularis", "Vena femoralis", "Vena brachiocephalica". This enumeration includes only some examples. It is also possible to localize and puncture veins other than these.

The apparatus of the invention can advantageously be employed in patients with hardly noticeable veins, such as infants, children, and in particular adipose (obese) people.
It is useful in differentiating between veins of good and poor patency, such as frequently punctured veins wherein blood passage is obstructed as a result of adhesion (obliteration).

In addition to saving time in detecting and puncturing vessels, thus avoiding multiple puncturing, which is inconvenient to patients, the apparatus of the invention enables the user to differentiate between different vessels such as veins and arteries. This will be of great advantage when, for example, a medicament should be injected into a vein but by no means into an artery.

The present apparatus can also advantageously be employed in veterinary medicine.

Following production, the cover or casing of the invention is packed, air-sealed and sterilized, for example, by using ethylene dioxide. This has the advantage that the gel pad being made of up to 98% of water is protected from drying out, thus ensuring long useability. The airproof packing comprises a tear-off strip, e.g., a perforation to allow easy opening. Preferably, the tear-off strip is arranged at the rear end of the cover, i.e., on the opposite side of the gel pad. After the packing is opened, the detector can be introduced into the cover by the opening at the tear-off strip, the cover can then be taken out of the packing and ' '' '` ' '1"' ~ ~ ~: ;: ',.:'i. ~" ~'' .~''~.i`.: ~, ,, ;',:, , ,, ,,, ," , , "~ """,, ~, "", ", ~,"" ~ ," ;, 21 212901~

the sealing lid at the rear can be closed. This ensures sterile conditions. The casing of the detector is preferably sealed so as to be completely waterproof and so that it can be placed in disinfectants for cleaning purposes. The batteries of the detector are inductively recharged by means of radiofrequency coupling.

Brief Description of the Drawings The invention will be illustrated in more detail by way of examples and drawings.

Fig. 1, 2, and 3 show a perspective view (on a reduced scale), a side view and a front view, respectively, of a first embodiment of a guiding apparatus of the invention.
~ -Fig. 4, 5, 6, and 7 show a perspective view (on a reduced scale), a side view, a front view, and a top view, respectively, of a first embodiment of a detector of the invention.
: -Fig. 8, 9, and 10 show a perspective view (with a syringe placed thereon and on a reduced scale), a side view and a front view, respectively, of the guiding apparatus of Fig. 1 with the detector of Fig. 4 attached thereto.

Fig. 11, 12, and 13 show a perspective view (on a reduced scale), a side view and a front view, respectively, of an alternative embodiment of a guiding apparatus of the invention.

Fig. 14, 15, and 16 show a perspective view (with a syringe placed thereon and on a reduced scale), a side view, and a front view, respectively, of the guiding 22 2129~

apparatus of Fig. 11 with the detector of Fig. 4 attached thereto.

Fig. 17 shows a schematic side view of the embodiment of Fig. 9 in operation.

Fig. 18, 19, 20, and 21 show a view from the bottom, a top view, a side view, and a front view, respectively, of a further embodiment of a guide apparatus of the present invention.

Fig. 22 shows two schematic halves of the side view of Fig.
20 along lines A-A and B-B.

Fig. 23, 24, and 25 show partial views of Fig. 20 with the lid open, partially closed, and completely closed, respectively.

Fig. 26, 27, and 28 show a front view, a top view, and a side view, respectively, of the gel pad as used in the embodiment of Figures 18 to 21.
, .:
Fig. 29, 30, 31, 32, and 33 show a view from the bottom, a top view, a side view, a semiview from the back (left side), a semiview from the front (right side), and a sectional view of Fig. 31 along line A-A, respectively, of a detector of the present invention.

Fig. 34 shows a block diagram of a transmitter for an ultrasound measuring device.

Fig. 35 shows a first embodiment of analyzing means for an ultrasound measuring device.

Fig. 36 shows a second embodiment of analyzing means for an ultrasound measuring device.

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Fig. 37 shows a third embodiment of analyzing means for an ultrasound measuring device.

Descri~tion of the Preferred Embodiments ~-The guiding apparatus of the invention shown in Figures 1, ~
2, and 3 is a slip-on cover 40 which can be attached to a ~ -detector. Such a detector may, for example, take the form of the detector shown in Figures 5 to 7. The slip-on cover has a hollow space 41 adapted to the detector in shape and size and covers the front part of the detector as apparent, e.g., from Figures 8 and 9.

The slip-on cover 40 comprises a groove or channel 43 at its upper surface 42 and two adjacent slanted surfaces 44, 45 and two lateral slanted surfaces 46 in the lower front region (see also Figs. 11 and 12). A gel pad 60 is provided at the front end 48 of the slip-on cover 40. The gel pad preferably is detachable. It ensures low-reflection transmission of the ultrasound waves from the detector to the respective body site and vice versa. At the front end, a support 50 extends upwardly from the upper edge 42, which support comprises a guide 52 for the hollow needle of a puncturing device.

The detector of the invention shown in Figures 4, 5, 6 and 7 comprises a substantially cuboid casing 10 which fully encloses the ultrasound measuring device. At its upper surface 12, there is provided a groove 13 to receive the body of a syringe (not shown).
:: -As especially apparent from Figures 5 and 6, there are provided in the front region of the casing 10 a lower slanted surface 14 and two lateral slanted surfaces 16.
Also, the casing 10 comprises at its front end a flat ~~-~ 212~01a surface 18 substantially perpendicular to the axial direction of the groove 13.

As also apparent from Figures 5 and 7, there are provided at the upper surface 11 of the casing first indicators 115a comprising, e.g., two LEDs and second indicators 115b comprising, e.g., seven LEDs. The first optic indicator serves, for example, to indicate the type of vessel, while the second indicator indicates, for example, the intensity of the reflected signal, that is to say the location and depth of the vessel to be punctured.

As a hand-held device, the detector is preferably provided with a rechargeable battery which can be connected to a suitable power unit, e.g., via contacts 70 at its rear end.

In Figures 8, 9, and lo the slip-on cover of Fig. 1 is attached to the detector shown in Figure 4. Preferably, a new sterile slip-on cover is attached prior to each puncture. For this purpose, the slip-on cover is slid over the front end of the detector until the flat surface 18 of the detector contacts the gel pad 60 of the slip-on cover 40.

Then, as apparent from Fig. 8, a syringe 20 is, for example, placed in the groove 43 on the upper surface 42 of the slip-on cover 40, the hollow needle 22 pointing toward the front end and being supported and guided by the support S0, while the piston 26 of the syringe protrudes beyond the rear end of the slip-on cover 40.

Figures 11, 12 and 13 show a second embodiment of a guiding apparatus of the invention in the form of a slip-on cover substantially corresponding to the first embodiment, but comprising an extendable cover tube 54 at its rear end. The cover tube 54 can be pulled in and out like an accordion and serves to provide protection and a sterile cover for the 212901~ :

detector and, if desired, for wires connected to an external device.

In Figures 14, 15, and 16 said second embodiment of a slip-on cover of the invention is shown with a syringe 20 placed thereon. As especially apparent from Fig. 15, the slip-on cover is attached to the detector 10 of Fig. 4.

Fig. 17 shows a combination of a detector and a slip-on cover 40 attached thereto, said apparatus being in contact with the skin 2 at its front end. The ultrasound measuring device of the detector comprises a first transducer 92 and a second transducer 94, the first transducer 92 being substantially parallel to the upper surface 41 of the slip-on cover 40, while the second transducer 94 forms an angle therewith, pointing upwardly in the drawing. The transducers 92, 94 communicate with a transmitter 80 and analyzing means 100, 200, 300, the result of which is shown by the indicator 115, 215, 315. In the example as shown the transducers 92, 94 are so arranged in relation to each other that their effective lines penetrate through the gel pad 60 and the skin 2 and hit the vessel 4 to be localized while being spaced apart.

Various views of a further preferred embodiment of a guiding apparatus of the invention, which will be referred to as the cover hereinafter, are shown in Figures 18 to 25. Figures 26 to 28 show views of the gel pad used in this embodiment. The cover 400 serves to receive a detector 500 as shown in Figures 29 to 33. As apparent from the bottom view of Fig.
18, the cover 400 comprises at its front end a gel pad 460 and at its rear end a lid 470. The lid 470 is attached to the top part by means of a double hinge 473 tsee Figures 19, 20, 23-25) in the region of the rear end so as to be flexibly swivelable. At the side of the lid opposite to the double hinge, there is provided a snap-in lug 472 which engages with a groove 471 located at the bottom of the cover 26 212901~

400 and parallel to the rear edge. Additionally, three recessed grips 490 are shown at the bottom of the cover.

As apparent from the top view of Fig. 19, the guide apparatus for a puncturing device such as a syringe (not shown) is formed by two upright webs 431, 432 in this embodiment. Said webs 431, 432 start at the front end of the cover 400, are parallel to each other and are adapted to any puncturing device to be guided in terms of their height, length and distance from each other. At the front end of the cover 400, there is provided a needle guide 450 which serves to guide the injection needle of a syringe. As apparent especially from Figure 20, said needle guide 450 protrudes upwardly and forwardly at an angle towards the front edge of the cover 400. As shown in Fig. 21, the needle guide is comprised of left and right side parts 451, 455 forming in the middle a slot 453 corresponding to the cross section of an injection needle in terms of its width. The side parts 451 and 455 each have wing pieces 452, 453 that are swivelably arranged in the region of the slot and that can be swivelled like a swinging door, allowing the slot 453 to be widened.

At the front end 480 of the cover 400, there is provided an aperture (hole) with a rim 485. In the cover 400, there is arranged at the front end the one-piece gel pad 460 which partially protrudes forwardly and upwardly through the aperture at the front end. The front part 461 of the gel pad is essentially parallel to the front edge of the cover. The front part 461 is contacted by the body site to be examined.
The opposite rear part 462 of the gel pad serves as a contact surface for a transducer 590 of a detector 500 (see Figures 29 to 33). As apparent especially from Figures 26 to 28, the gel pad 460 has a circular notched line 466 in which the circular rim 493 of the aperture engages. This mechanical engagement (back view) ensures that the gel pad 460 is held in place at the front end of the cover 400. The 27 2129~1~

gel pad fully occupies the front space of the cover 400 and ~ -comprises a camber 463. This leads to a large portion of the gel pad contacting the body site to be examined and to undisturbed ultrasound reflection. ~;
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Figures 23, 24, and 25 show the lid 470 in various open positions. In Fig. 23 the lid is swivelled upwardly, allowing the detector 500 to be placed in and out through the aperture at the rear end. In Fig. 24 the snap-in lug 472 is engaged with the groove 471. In Fig. 25 the double hinge 473 is additionally swivelled in, causing the lid 470 to completely close the rear aperture of the cover 400. ~-The detector 500 (see Figures 29 to 33) is adapted to the interior of the cover 400 in size and shape. At the bottom part, there are provided recesses 580 (see Fig. 29). At the front end, there is provided the transducer 590 which slightly protrudes from the casing of the detector 500. The top part of the detector comprises upwardly protruding visual indicators 515a and 515b. At the back, there is a recess 520 to which a moving coil can be introduced to charge the rechargeable batteries provided in the detector 500. At the top part of the detector, there is also a switch 570. This switch serves to switch on the detector and can be operated by pressing against the specific site of the cover 400 even if the detector is inserted in the cover 400.

Fig. 32 shows partly the rear view with the recess 520 and partly the front view with the transducer 590. Fig. 33 shows a section along line A-A of the side view of Fig. 31.

The embodiment described above has the advantage that the detector 500 is entirely surrounded by the cover 400, with a large portion of the transducer 590 contacting the rear 462 of the gel pad, ensuring good coupling between the ~ -~
ultrasound and the body site to be examined.
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` 28 2129~1~

The above-described examples refer to hand~held devices which can be operated with one hand. Both the guiding apparatus together with the puncturing device such as a syringe are held in one hand, the vessel to be punctured is localized, the puncture is made and then the guiding apparatus 40 is detached from the puncturing device 20. This means the guiding apparatus and the syringe 20 can be easily detached from each other once the puncture is completed.

The casing material of the guiding apparatus and the slip-on cover is preferably plastic. In the sound penetrating region an ultrasound wave-permeable material, preferably a polyacrylate-based hydrogel, is used. Preferably, the material of the slip-on cover is light-permeable so that in the embodiment shown in Figures 8 and 14 the indicators 115a and 115b positioned underneath are visible. Alternatively, the indicators may be arranged in a region uncovered by the slip-on cover. It is also possible to use acoustic signal transmitters as indicators.
.
Alternatively, the apparatus may be provided with an optic indicator to determine the- flow direction (to distinguish between arteries and veins) and depth of the vessel to be punctured and with an acoustic or optic scale to determine the flow rate.

The ultrasound transmitter shown in Fig. 34 comprises an oscillator 81 which preferably operates with a frequency of 8 MHz, a buffer amplifier 82 connected to the output of the oxcillator~ the output signal of which is supplied to a pulse shaper 83, the output signal of which, in turn, is supplied to two transducers 92, 94 via a power amplifier 84 and a transmitter/receiver switch 96. The ultrasound transmitter additionally comprises control means 85 to switch on and off via a first output UA1 the oscillator 81, the buffer amplifier 82, and the power amplifier 84. The envelope curve of the pulse shaper 83 is controlled via a -~ 2~29~1a second output UA2 of the control means 85. Via a first input UEl of the control means 85 continuous or pulsed operation of the transmitter can optionally be selected. A second input UE2 of the control means 85 serves to trigger a pulse.
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The ultrasound waves transmitted from the transducers by the transmitter are introduced into the body sites to be examined and the reflected portions are received by the transducers. The received signal is supplied to the analyzing means 100, 200, 300 (Figures 35, 36, and 37) via the transmittertreceiver switch 96. When a test head with two transducers or a receiver with a large volume range is used, the switch may be very simple in construction or may even be omitted.

In the analyzing means the received signal is first supplied to a limiter 101, 201, 301 which protects the subsequent components from overload. This limiter is followed by a low-noise pre-amplifier 102, 202, 302, the output signal of which is supplied to an amplifier 104, 304 via a band pass filter 103, 203, 303 (see Figures 35 through 37). The band pass filter preferably has a center frequency corresponding to the transmitter frequency, e.g., 8 MHz, and a band width of, e.g., 20 kHz. In the digital receiver using the RF
method, the amplifier 304 preferably is a logarithmic amplifier or an amplifier with key modulation because the required dynamics of reception can easily be achieved thereby.

In the embodiments of analyzing means as shown in Figures 35 and 37 the output signal of the amplifier 104 and the band-pass filter 203 is supplied to a mixer 106, 206 which additionally receives a reference signal from a local - ~ .
oscillator 105, 205. The output signal of the mixer is ~ `
.: -supplied to a low-pass filter 108, 208 via a wide band -~
terminator 107, 207 for impedance adaption either directly or through a low-noise amplifier 204.

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In the analyzing means shown in Fig. 35 the reference signal of the local oscillator 105 has a frequency of 7.99 MHz which may be tuned. The low-pass filter has a cut-off frequency of slightly less than 10 kHz corresponding substantially to the differential frequency of the input signal (8 MHz) and the reference signal (7.99 MHz~. The output signal of the low-pass filter 108 is supplied to a loudspeaker 115 via a voltage divider 109 and an AF
amplifier 110.

This analyzing means of purely analog construction provides an inexpensive solution for estimating the Doppler maximum and thus localizing vessels lying beneath the skin.

In the analyzing means shown in Fig. 36 the frequency of the reference signal of the local oscillator 205 preferably is 7.95 MHæ and the low-pass filter has a cut-off frequency of 40 kHz. The output signal of the low-pass filter 208 is supplied to an analog-to-digital converter 212 (16 bits) via a limiter 209, a low-pass filter 210 and a driver circuit 211. The limiter is to protect the ADC from destruction and from temporary malfunction in the case of overload. The low-pass filter positioned directly before the ADC removes harmonic waves generated by limitation which would be folded back to the fundamental wave region by the sampling process.
A sampling pulse generated by a clock generator 216 to sample the input signal is supplied to the analog-to-digital converter 212. The output signal of the analog-to-digital converter 212 is supplied to a signal processor 213, the result of which is shown by an indicator 215.

In the analyzing means depicted in Fig. 37 the pre-amplified and bandlimited received signal is supplied directly to an analog-to-digital converter 308 via a limiter 305 comprising a low-pass filter, and a driver circuit 306. A clock generator 307 provides a sampling pulse to the analog-to-~A ~ A

~ 31 2129~1~

digital converter 308 with which the received signal issampled. In the example as shown the sampling pulse has a frequency of 20 MHz, while the received signal has a frequency of 8 MHz. The output signal of the analog-to-digital converter 308 (20 million word(s)) is supplied to a signal processor 309 preferably with DMA (direct memory access) logic. The result of the calculations of the signal processor 309 is shown by a display 315.

These digitalized analyzing means allow flow direction and depth, and also pulse rate, blood pressure, flow rate, pathological alterations as well as tissue to be examined.
The indicator in the latter case is preferably a graphics display such as that of a notebook PC. optionally, the analyzing means is arranged separately from the guide apparatus and both communicate with each other via signal connections such as lines or light guides.

The present invention provides a portable electronic device which enables medically trained personnel to readily determine the location of, for example, a vein beneath the skin and to even accurately puncture veins lying deeply beneath the skin with a syringe or a vein catheter. The apparatus can be handled with one hand and allows ultrasound monitoring while avoiding direct contact of the detector and the ultrasound head with the patient's body as well as the user, thereby avoiding the requirement to sterilize the detector including the ultrasound head prior to use.

Claims (20)

P a t e n t C 1 a i m s

1. An apparatus capable of receiving an ultrasound detector with at least one ultrasound transducer for transmitting and receiving ultrasound waves, an analyzer connected to the ultrasound transducer, and an indicator, said apparatus comprising:
- a guide means (43, 430) for supporting a vessel puncturing device (20), and - an ultrasound coupling medium (60, 460) provided at the front end of the apparatus, characterized in that the apparatus takes the form of a casing capable of receiving at least the front portion of the ultrasound detector, - the ultrasound coupling medium taxes the form of a gel pad (60, 460), and - the guide means is provided on one lateral surface of the casing and formed by at least one guide surface onto which the vessel puncturing device can be placed and accurately guided and slid along the length of the apparatus.

2. An apparatus as defined in claim 1 wherein the apparatus (40, 400) is open at its rear end so that a detector can be introduced into the apparatus from the rear end to the front end (48, 480) and the detector can be coupled with the gel pad (60, 460) for ultrasound waves.

3. An apparatus as defined in claim 2 wherein the rear end can be closed by a lid (470).

4. An apparatus as defined in any of claims 1 to 3 wherein the gel pad (460) is mechanically fastened to the front end (480), preferably by a protruding rim (485) that engages with a notch (466) in the gel pad (460).

5. An apparatus as defined in any of claims 1 to 3 wherein the gel pad is fastened to the front end (48, 480) of the apparatus (40, 400) by adhesion or welding.

6. An apparatus as defined in any of claims 1 to 5 wherein the front part of the gel pad (460) is at an angle of 30-600, preferably 45°, relative to the ultrasound direction.

7. An apparatus as defined in any of claims 1 to 6 wherein the guide surfaces (430) are formed by two upright webs (431, 432) which run parallel from the front end (480) to the rear and are spaced apart.

8. An apparatus as defined in any of claims 1 to 6 wherein the guide surfaces are formed by an elongate groove (43) adapted to the vessel puncturing device (20) in size and shape.

9. An apparatus as defined in any of claims 1 to 8 wherein the guide means is adapted in size and form to a syringe (20) comprising an injection needle (22), a body (24) and a piston (26) such that the body (24) of the syringe is slidably guided on the guide surface (43, 430).

10. An apparatus as defined in claim 9 wherein a support (50) or a needle guide (450) is provided in the region of the front end (48) of the apparatus (40), in which support or needle guide the injection needle (22) is slidably guided along the length of the apparatus.

11. An apparatus as defined in claim 10 wherein the dimensions of the support or needle guide (50, 450), the guide surface and the position of the two in relation to each other with regard to a syringe (20) of a particular type and size are such that the body (24) of the syringe and the injection needle (22) are slidably guided in the guide surface (43, 430) and along the support (50) or needle guide (450), respectively.

12. An apparatus as defined in any of claims 1 to 11 wherein the region of the front part of the apparatus (40, 400) is tapered toward the front end (48).

13. An apparatus as defined in claim 12 wherein the apparatus (40, 400) comprises in the region of its front end two slanted lateral surfaces (46, 446) directed towards the front end and forming an angle with each other, and a slanted bottom surface (44, 444) directed towards the front end and forming an angle with the lateral surface (42, 442).

14. An apparatus as defined in claim 13 wherein the slanted lateral surfaces and the bottom surface (44, 46) are at angles of about 25° and about 16°, respectively, relative to the axial direction of the vessel puncturing device (20).

15. An apparatus as defined in any of claims 1 to 14 wherein a preferably extendable tubular cover (54) is provided at the rear end of the apparatus (40).

16. A combination of an apparatus as defined in any of claims 1 to 15 and an ultrasound detector, said detector being adapted in size and form to the interior of the casing.

17. The combination as defined in claim 16, with at least two transducers (92, 94) being arranged in the detector such that their effective lines form an angle with each other and/or preferably are at a specific distance from each other deep down in the vessel to be punctured.

18. The combination as defined in claim 16 or 17, with the ultrasound beams having an elliptic cross-sectional profile.

19. The combination as defined in any of claims 16 to 18, with down conversion being effected in the hand-held device and the resulting signal being supplied to an analog-to-digital converter (212), the output signal of which is analyzed by a signal processor (213) and the result of which is shown by an indicator (215).

20. The combination as defined in any of claims 16 to 19, with an analog-to-digital converter (308) being provided in the hand-held device to digitalize the received signal and to supply the digitalized signal to a signal processor (309) and with the result being shown by an indicator (315).