Electrode needle with active radiofrequency filament

Abstract: 1. Electrode needle for the treatment of parenchymatous tumours through radiofrequency-induced interstitial hyperthermy, comprising a hollow guide needle (11) and a radiofrequency active filament (12) threaded into the needle, connectable to a radiofrequency generator and capable of axial movements between an inactive position retracted into the needle and an active position of protrusion of a terminal segment of the filament from the distal end of the needle, characterised in that said terminal segment (13) of the filament is shaped to pass from a rectilinear shape when the filament is in retracted position into the needle, to a spiral shape when the filament is in the active forward position.

Description: The present invention relates to an electrode needle, in particular for the treatment of parenchymatous tumours through radiofrequency-induced hyperthermy. The treatment of tumoral masses through radiofrequency-induced hyperthermy has already been proposed with success. The instruments currently available for such treatment are catheter tubes with at least one terminal electrode, or needles with a rectilinear radiofrequency active filament. However, catheter tubes are relatively large and, even though they are efficient due to the presence of a big electrode, they exhibit the disadvantage that they can only be introduced into the patient's body up to the tumoral mass through natural open ways or opened through expansion. On the other hand, needles with an active filament can be introduced into the body making them pass through the tissues, but their are limited in their action due to the small diameter of the active filament, which operates on limited areas and thus implies longer operation and treatment times. On the other hand, if larger needles are use for the treatment of larger tumoral masses, the use of such needles is more traumatic for the patient. Purpose of the finding is that of finding a remedy for the limitations of known instruments, thus providing a radiofrequency active electrode needle that could be used in the treatment of even considerable tumoral masses, maintaining in any case its limited diameter to reduce the traumatic effect and allow reaching organs or parts of organs that could not be otherwise reached but with larger needles or tubes. The purpose and resulting advantages are achieved with an instrument comprising a hollow guide needle and a radiofrequency active filament threaded and sliding into said needle between a retracted position, withdrawn into the needle, and a forward position emerging from the distal end of the needle and where said filament has a terminal segment bending in a helical or spiral shape when the filament is in the forward position. Thanks to such helical and/or spiral arrangement of a terminal part, even though the active filament is very thin it is capable of irradiating and thus treating a much larger surrounding area than the area of its section. In other words, starting from very thin guide needle and radiofrequency active filament it is possible to easily treat tumoral masses that are at least as wide as the width of the helical or spiral part of the filament. Further details of the finding will appear more clearly from the following description, made with reference to the attached indicative and nonlimiting drawings. In such drawings: Figure 1 shows separate needle and active filament according to a first embodiment; Figure 2 shows a longitudinal section of the needle of Figure 1 with the filament threaded in a retracted position; Figure 3 shows the needle with the filament in forward position for use; Figure 4 shows a longitudinal section of the electrical connection means to use the electrode needle of the previous Figures; Figure 5 shows a needle with a threaded filament in a second embodiment and with open connector; and Figure 6 shows a perspective view of a detail of the handling means of the filament threaded in the needle of the previous Figure. In such drawings, reference numeral 11 indicates a guide needle intended to be introduced into the body of a patient, and reference numeral 12 indicates a radiofrequency active filament, sized to be threaded and to slide into needle 11. The filament is rectilinear except for a distal terminal part 13 shaped as a helix or a spiral, for example through a thermoforming process. Such terminal part 13 can be in axis with respect to the main longitudinal direction of the needle, or angular, for example up to 90°. For the constructional purposes, the needle has an external insulating coating 11' for its entire length, except for a part at the distal end 11". According to a first embodiment shown in Figures 1-4, the proximal end of the radiofrequency filament 12 protrudes from the needle and is buried into a union 14, for example through a resin casting, which in any case is exposed for the contact with a filament electrical connection connector 15 to a radiofrequency generator, not shown. Once it has been threaded into the guide needle, or keeping it still, the filament can be made to slide forward and backward through union 14, between an inactive position in which it is completely retracted into the needle, and an active position in which the terminal part 13 protrudes from the distal end of the needle. In a second embodiment shown in Figures 5 and 6, the proximal end of the guide needle 11 is introduced into a connector 16 wherein there is housed a small shaft 17 capable of rotating around a perpendicular axis with respect to the needle through a hand grip 18. The proximal end of the active filament 12 is engaged with said shaft 17 so that, when the hand grip 18 is rotated in clockwise or counter clockwise direction, the terminal part 13 of the filament respectively protrudes from or withdraws into, the needle. In this case, the electrical power supply cable 19 is directly inserted into connector 16 and is connected to the distal end of the guide needle 11. To have an indication of the position of the active filament 12 with respect to the guide needle 11, once it has been introduced into the patient's body, the hand grip 18 can be associated to a pointer 20 angularly movable between at least two reference points provided on the connector. For its angular movements, said pointer can exhibit, for example, a pin interacting with a spiral structure obtained on the inner side of the hand grip 18. Irrespective of the embodiment, moreover, a thermocouple - not shown - can be applied on the distal part of the guide needle 11 for measuring the body temperature. In practice, when the needle is introduced into the patient's body, the filament is held in inactive retracted position, and its terminal part 13 remains substantially rectilinear, contained into the needle recess, as shown in Figure 2. When the tumoral mass to be irradiated has been reached, the terminal part 13 is pushed outside by the needle, it winds up as a spiral or helix, as shown in Figures 3 and 4, thus affecting a wide irradiation area. Once the treatment has finished, the terminal part of the filament is withdrawn into the needle. It must be noted that the effectiveness of the electrode needle can be further improved using more active filaments threaded into the same guide needle and configured as described above. Finally, it must be noted that the electrode needle being examined can also be used in combination with other electromagnetic wave generators, for example microwave generators.

Claims: Electrode needle for the treatment of parenchymatous tumours through radiofrequency-induced interstitial hyperthermy, comprising a hollow guide needle (11) and a radiofrequency active filament (12) threaded into the needle, connectable to a radiofrequency generator and capable of axial movements between an inactive position retracted into the needle and an active position of protrusion of a terminal segment of the filament from the distal end of the needle, characterised in that : said terminal segment (13) of the filament is shaped to pass from a rectilinear shape when the filament is in retracted position into the needle, to a spiral shape when the filament is in the active forward position; and the terminal segment is angled with respect to the longitudinal direction of the needle. Electrode needle according to claim 1, wherein the terminal segment of the filament is helical. Electrode needle according to claim 1, wherein the terminal segment of the filament is spiral. Electrode needle according to any one of the previous claims, wherein the needle is provide with an external insulating coating (11') and a non-insulated distal part (11"). Electrode needle according to any one of the previous claims, characterised in that it further comprises a thermocouple applied on the distal part of the guide needle (11). Use of a filament having a terminal segment preformed into a hollow guide needle for the treatment of tumours through radiofrequency-induced hyperthermy, wherein said terminal segment can take a rectilinear shape when retracted into the needle, and a spiral or helical shape when emerging from said needle.

Inventors: MALTESE MICHELE, MALTESE, MICHELE
Applicants: INVATEC SRL, INVATEC S.R.L
Application year: 2001
Main classification: A61N1
IPC codes: A61B18, A61N1