FR2569114A1 - High flow rate injection tube for a contrast product for radiological examinations and method of making it - Google Patents

Abstract

The present invention relates to a high flow rate injection tube. The method of manufacture of this tube is characterised in that the operation of extruding the main tube 2 is followed by at least one hot drawing operation in particular carried out at the temperature of the Vicat softening point of the material from which this main tube 2 is made, before wrapping its proximal end 3 with the optional reinforcing sheath 4. Application to injecting a contrast product for radiological examinations in particular.

Description

 The present invention relates to an injection probe with a very high flow rate of contrast medium, in particular for digital angiography and to its method of production.

 Digital angiography has a number of advantages over conventional angiography.

 Any technician in the field knows that the radiography of the vessels consists in injecting by arterial route an iodinated contrast agent, opaque to an X-ray beam, in order to create a difference in density with the surrounding structures. The high concentration of contrast agent in arterial blood (due to the fact that iodine is injected through a catheter placed directly in the arterial lumen after catheterization of a peripheral artery) allows to obtain a radiological image by modulation of the intensity of the X-ray beam emerging relative to the incident beam, this image being able to be read directly on a film or on a television screen.

 However, the photographic processing of the radiological image thus obtained, namely enlargement and in particular subtraction - that is to say the suppression of parasitic shadows (or gray levels) corresponding to the non-vascular parts (soft parts and bones) - are long and tedious and always involve a loss of information, while with the digitization of the radiological image one can carry out the subtraction directly during the radiological examination (therefore, without going through the photographic stages).

In addition, digital angiography makes it possible - to inject the contrast product by venous route,
thus eliminating the risks of arterial puncture, - not to use general anesthesia or
premedication, - to identify the contours of a cavity without intervention
manual, hence the possibility of calculating its volume, - calculating the bit rates by videodensimetry, and - increasing the contrast, which implies the use of a
less opacifying agents to inject.

 Regarding the rate of acquisition of digital images, which are in matrix form, this is currently limited to one to three images per second with matrices of 512 x 512 elementary points or pelas ", but already at this rate it is necessary to have fairly high contrast product flow rates, which has guided the manufacturers of injection angiography probes in the direction of reducing their internal diameter by producing a new generation of probes, called "large" probes flow "or" high pressure "or even" small caliber ", which make it possible to inject a prefixed quantity of contrast medium in the shortest possible time, the reduction in the internal diameter also causing a reduction in the external diameter which, in practice , is an indication of the first and whose unit of measurement is French (a French = 1 F = 0.33 mm): we managed to make "small caliber" probes of 3, 4 and 5 F.

 Different solutions have been provided in the prior art, in terms of materials and structure, to improve the flow rate of injection probes in conventional or digital angiography.

 A first type of probe is known which is obtained by coextrusion of a polyurethane tube on a nylon tube, the polyurethane outer sheath allowing the internal nylon tube to withstand the mechanical stresses due to the high values of hydrodynamic pressure; however, this type of probe has a relatively high rigidity.

There is also known a second type of probe armed with a metal braid made of stainless steel integrated in "Rilsan", so as to combine the advantage due to the reduction in the thickness of the wall of the probe ( which reduction is granted by the intrinsic properties of the "Rilsan") to the good transmission of the torque imparted to the entire probe by the user who is due to the peripheral arrangement of the armature, the latter also allow withstand the hydrodynamic pressures imposed by the high flow rates required in certain applications of angiography, particularly in cardiology. To reduce the risk of vascular trauma, the distal end of this second type of probe does not have a frame: it is made in "RkexX and is welded by heating to
UHF to the armed party, so that this solution is very expensive and its complicated manufacturing.

 A third type of probe, making it possible to ensure high flows of contrast product, consists of a tube made of "Rilsan" which includes a reinforcing sheath of about 4 cm in length, also made of Rilsan and disposed at the proximal end of the probe so as to absorb the stress due to the hydrodynamic pressure: in fact the latter decreases in intensity by a value equal to the pressure drops as one reaches the distal end, in so that the maximum value manifests itself at the level of the sheathed proximal part.

 In each case, the shape of the distal end of the probes used is adapted to the vascular territory to be irrigated.

 The object of the present invention is therefore to provide an injection probe with a very high flow rate of contrast medium and intended for digital angiography, which better meets the needs of the practice than the probes aiming at the same purpose previously known, in particular in that it combines great flexibility, exceptional performance of resistance to pressure and therefore flow.

The subject of the present invention is a method of manufacturing a very high flow rate injection probe, in particular of a contrast product for digital angiography, of the type comprising in particular the following operations - extrusion of a main tube, and - possibly, extrusion of a secondary tube of shorter length,
followed by 1 1 application of this secondary tube to 1 1 proximal end
of said main tube, so as to constitute a reinforcing sheath, which method is characterized in that the operation of ex: trusion of the main tube is followed by at least one hot drawing operation, before wrapping, optionally, its proximal end by said reinforcing sheath.

 The present invention also relates to a very high flow rate injection probe obtained by this method.

 In addition to the foregoing provisions, the invention also comprises other provisions, which will emerge from the description which follows.

The invention will be better understood using the additional description which follows, which refers to the accompanying drawings in which - Figure 1 is a schematic sectional view of an extru
classic deuse to obtain the main tube
of the probe according to the present invention, - Figure 2 is a schematic view also in section
corresponding to the drawing installation of the tube obtained
using the extruder of Figure 1, - Figure 3 shows the drum storage facility
of the tube thus stretched, - Figure 4 shows the steps for producing the probe
according to the invention from a drawn main tube and
a sheath of reinforcement of its proximal end cut
to the desired length by sheathing and applying a
suitable base for connection to an injector (not
shown) of contrast material.

 It should be understood, however, that these drawings and the corresponding descriptive parts, are given solely by way of illustration of the subject of the invention, of which they do not in any way constitute a limitation.

 The injection probe 1 according to the invention, intended for injecting contrast agent for digital angiography, comprises a main tube 2 - the distal end 5 of which has been shown (in a nonlimiting manner and for reasons of simplicity ) as being straight - and a secondary tube 4, which sheaths the proximal end 3 of the main tube 2, as well as a base 6 making it possible to connect the probe 1 to an injector (not shown) of high density contrast agent d 'iodine, after having trapped between this base 6 and a nut 19 a flange 20, 21, produced on the two tubes 2 and 4, respectively.

 The main tube 2 is obtained by extrusion and drawing from powder (or granule) 7, in particular from "Rilsan", contained in the feed hopper 8 of the extruder shown in FIG. 1, which also shows the screw extrusion 9, disposed inside the body 10 of the extruder, the punch 11 and the extrusion head 12, the tube in the extruded state being indicated by the reference 2a.

 Then the tube 2a is stretched substantially at the temperature of the VICAT point of the material used, using, for example, the installation shown in Figure 2, which is placed in cascade relative to the extruder of Figure1 and which comprises a heating die 13 receiving the extruded tube 2a, and two conformers, one of which is external 14, while the other is internal and is constituted by a mandrel 15, defining by cooperation the external and internal diameter of the probe 1, respectively. A pulling train 16a advances the tube 26 in the stretched state towards a device 17, known to technicians in the field, for heat treatment for removing the tube 2b from the mandrel 15.

 It goes without saying that the extruded tube 2a can be subjected to two or more drawing operations to obtain a tube whose internal diameter and thickness of its wall (therefore the external diameter) have a value prefixed by way of example. non-limiting, it is possible to start from an extruded tube 2a of 6 F to arrive at a drawn tube of 4 F or 3 F in one or more drawing operations.

 In any case, the stretched tube thus obtained is stored on a drum 18 by cooperation with a second drawing train 16b which, at the end of the winding operation allows the withdrawal of the shaping and guiding mandrel 15.

 Now, it has been proven that the above mechanical and thermal treatments make it possible to obtain a main tube 2 which has an exceptionally high resistance to pressure allowing it to convey, possibly in cooperation with said secondary tube 4 enveloping the proximal end 3, also exceptionally high contrast product flow rates, which makes the probe according to the invention particularly suitable for the requirements of digital vascular radiology.

 Between the main tube 2 and the proximal sheath 4 there is a functional clearance which is necessary and sufficient for the main tube to be able to deform slightly under the action of the injection pressure before this deformation can be counteracted by said sheath 4.

 The influence of stretching can be appreciated by considering that, among the probes of the prior art, in particular that which corresponds to the third type of probe proposed in the prior art described above - whose main tube is not stretched and which has a diameter of 4 F and has a reinforcement sheath of 4 cm - bursts when injecting contrast medium with a flow rate of 15 ml / s immediately downstream of the reinforcement sheath, while in the same conditions there is no bursting after stretching the main tube, in accordance with the present invention.

However, it has been found that the maximum value of 30 ml / s can be reached without bursting - a value largely sufficient for current applications - with a probe whose main drawn tube has a diameter of 4 F and a reinforcement of its end proximal constituted by a sheath whose length is advantageously greater than 4 cm and at most equal to approximately 7 cm: in practice this maximum value is to be considered as a preferential value in order to respect the useful length of the probe, namely the length of the tube main downstream of said
(possible) reinforcing sheath and avoid that the total length becomes too great.

 With regard to the probes of the first and second types proposed in the prior art, their performances are even worse: for example1 with a probe in "#bax" of the second type having a diameter of 4 F one can only reach a flow 8 ml / s.

 When the sheath is absent, the maximum flow rate without bursting, which can be reached with this drawn probe of diameter 4 F, drops to 24 ml / s.

 It has been noted that if the diameter of the drawn probe according to the invention increases, for example from 4 F to 5 F, the maximum flow rate of 30 ml / s can still be obtained without bursting, and this is also valid without a sheath. reinforcement.

 However, the maximum value of 30 ml / s is - as already emphasized above - largely sufficient for applications, taking into account the fact that, for safety reasons, the dose of contrast agent injectable into an organism, over time maximum of 2 sec. which is imposed by digital angiography, must not exceed the quantity of approximately 0.5 ml / kg of patient weight: in fact, the quantity of contrast product that can be injected in 2 sec. with a flow rate 30 ml / s is 60 ml, which corresponds to a patient whose weight is 120 kg, so that the probe according to the invention can be used advantageously with all the patients who are brought to be treated in the field of vascular radiology.

 It goes without saying that, with equal diameter, shape of the distal end and useful length, the thickness of the wall of the main tube of the probe according to the invention is less compared to the probes of the prior art, in particular of the said third type, so that are improved not only the pressure and the injection rate of the probe but also its flexibility, which makes the probe according to the invention, less traumatic.

 In any case, the thickness of the drawn main tube is calculated so that it is able to withstand the pressure corresponding to the chosen application over its entire length or over its useful length, namely over the length not reinforced by the proximal sheath. above when it exists.

 As regards the materials which can be used to make the probe according to the invention, in addition to the materials already mentioned, such as "Rilsan" - which is a polyamide of vegetable origin, in particular based on castor oil - or "Pebax "- which is a polymer made up of a linear and regular chain of rigid polyamide segments and flexible polyether segments - all thermoplastics and also thermoplastic polyurethanes can be used.

 As is apparent from the above, the invention is in no way limited to those of its modes of implementation, embodiment and application which have just been described more explicitly; on the contrary, it embraces all the variants which may come to the mind of the technician in the matter, without departing from the framework, or the scope, of the present invention.

Claims (4)

 1.- Method of manufacturing a very high flow rate injection probe (1), in particular of contrast product for digital angiography, of the type comprising in particular the following operations - extrusion of a main tube (2) , and - optionally, extrusion of a secondary tube (4) of  shorter length, followed by the application of this tube  secondary (4) at the proximal end (3) of said tube  main (2), so as to constitute a sheath of  reinforcement, which method is characterized in that the operation of extruding the main tube (2) is followed by at least one hot drawing operation, in particular carried out at the temperature of the VICAT point of the material of which this tube is made main (2), before possibly wrapping its proximal end (3) by said reinforcing sheath (4).  2.- Very high flow rate injection probe, in particular of contrast agent for digital angiography, obtained using the method according to claim 1, of the type comprising a main tube (2) made of plastic material, possibly reinforced by a sheath (4) also made of plastic, disposed at its proximal end (3), as well as a base (6) for connecting the probe (1) to an injector of contrast product known per se, which probe (1) is characterized in that the main tube (2) has: - a particular structure determined by hot drawing substantially at the temperature of the VICAT point of the plastic material which constitutes the previously extruded tube subjected to drawing when hot, - a reduction in the diameter of the tube before hot drawing, - and possibly a reduction in the initial thickness of the wall of the tube before being subjected to hot drawing, which main tube (2 ) stretched presents a resistance nce exceptionally high pressure and flexibility.  3. A probe according to claim 2, characterized in that its proximal end (3) is reinforced by a sheath (4) of flexible plastic material, such as thermoplastic material, the length of which is sufficient to strengthen the proximal end of the tube main (2) stretched while being compatible with the easements linked to the introduction of the useful length of the probe into the vessels, such a reinforcement allowing exceptionally high flow rates, of the order of 30 ml / sec., of product of contrast in the main tube (2) stretched, for a diameter of the stretched tube between 3 F and 5 F.  4. A probe according to claim 3, characterized in that the inside diameter of the sheath (4) and the outside diameter of the main tube (2) are calculated so as to determine a clearance between the sheath (4) and the main tube (2), necessary and sufficient to allow a slight deformation of the main tube (2) by the injection pressure of the contrast product, without affecting the role of reinforcement of said tube (2) of the sheath (4).