Radiating device for hyperthermia

Abstract

A flexible three-paths catheter provided with a balloon carries a sealingly sheathed radiofrequency radiating antenna, together with the shielded power supply cable and with some thermocouples, within a plastic lining surrounded by a flow of liquid; a second path carries the power supply cables of some outer thermocouples, flooded by the reverse liquid flow, while the third path allows a fluid to flow through for inflating the balloon.

Introduction of the catheter into a hollow organ makes it possible to perform hyperthermal therapy of tumors by means of radiation.

Description

prostata prostrate 33 and bladder 32, while simultaneously taking care that the catheter front end does not subject the bladder internal wall to any pressure. Once the catheter has been introduced into the bladder in such a way, one actuates the supply pump of conditioning liquid 2 preferably comprising a solution of a selective citotoxicity cytotoxicity substance, which is accordingly forced to circulate through the bladder coming out from opening 3 and going back through opening 4, or viceversa, along side channel 5 which carries the power supply cables of thermocouples 6, 6′, 6″ therewithin. The liquid forced circulation, provided by the variable flowrate supply pump, suitably combined with an outer balancing and degassing chamber, allows the volume of liquid within the bladder to be balanced at will, in such a way as to compensate the pathological or physiological urine production, while thoroughly ejecting the gases generated or unwillingly introduced in circulation, out of the bladder, in order to prevent irradiation non-uniformities which would otherwise be caused by coexistance of anisotropic media. Once bladder 32 has been completely filled with conditioning liquid 2, ballon 7 is inflated by introducing a fluid, which may be a gas but it is preferably a liquid, along side channel 8 and through the end opening 9 thereof; ballon 7 inflated as mentioned above, pushes then against outer thermocouples 6, 6′, 6″ power supply cables thereby moving said thermocouples into tangential engagement against bladder wall 32 in different positions, in order to detect the temperatures prevailing therein as caused by irradiation generated by antenna 1. The possibility of changing the location and the number of the outer thermocouples, enables the thermocouples to be positioned at will, on the bladder wall, or in any case place of the body organ to be treated, while being able to individually check the temperatures in the various locations. The inflated ballon 7 protects the bladder neck wall from an excess heat caused by the proximity of the radiating antenna, and in the meantime it prevents the catheter from being accidentally displaced or from coming out through the bladder neck.

The dimensions of antenna 1 are such that it may be freely positioned along the catheter while being obviously wholly contained within the human bladder to be treated, but in the meantime they must be suitable to generate a therapeutically active radiation, in order to reach the temperatures considered lethal for the cancer cells. Since the physical length of an antenna is related to the virtual electrical length thereof through an equation involving the impedance of said antenna, as well as the impedance deriving from the environment irradiated by the antenna, the antenna electrical length comes out to be inversely proportional to the irradiated medium conductivity. Accordingly, since the conductivity of an aqueous solution is for instance many times higher than the conductivity of air, when operating in an aqueous environment it is possible to use an antenna which is physically quite shorter than the length needed if it were necessary to operate in air.

The dipole according to this invention corresponds to a dipole of the quarter wave type and in the aqueous environment comprising the solution filled bladder, it makes it possible to operate at frequencies in the range of 900-1000 MHz; in particular, a frequency of 915 MHz has been chosen since very different frequencies would result in penetration, intensity, and other effects not always exactly predictable and controllable in the body tissues, since in general high frequencies have a low penetration power and therefore they do not provide the desired local heating, while lower frequencies, having a higher penetration power, may get deeper tissues involved and damaged.

On the other hand, radiations having different wavelengths might create a disturbance for radio and telephone communications, protected by constraints imposed by the legislations of the various countries.

In order to reduce to a minimum and possibly to nil the influence of the radiofrequency field of the thermocouples, as well as the various thermoelectric effects connatural with said thermocouples, the supply cable end stretches close to the thermocouples are wound into an helical shape whereby the temperature measured in the various sensing points is a reliable data, unaffected by said influences. The above structure construction prevents measuring errors due to conduction, it provides a reliable temperature indication, for instance exactly in the area of the dipole power supply position in the case of thermocouple 30, and it reduces in an extremely effective manner the thermocouple self-heating process due to radiofrequencies, also when there is an extremely high concentration of energy, whereby said structures are almost unaffected by the disturbances in the radio-frequency field.

Since the sizes, and in particular the cross-sections of the plural device components according to this invention must be extremely small, to suit the particular field of use desired for the device, the energy losses due for instance to self-heating of the antenna power supply cable are particularly high, for instance in the range of 20-40%. Since this undesirable self-heating, due to the Joule effect, might cause excessive heating of the urethral walls, and accordingly a discomfort for the patient subjected to treatment, or even damages to the tissues, the antenna cable, and the antenna itself are continuously cooled, while in operation, by using the conditioning liquid flow directed to the bladder and then withdrawn again therefrom, whereby a simultaneous control action is obtained, for controlling the temperature prevailing both in the liquid within the bladder and along the urethra. Temperature control is effected by variations of the conditioning liquid supply flow and of the cooling source temperature. In such a way it is possible both to increase the temperature and to withdraw heat.

In order to enable outer thermocouples 6, 6′, 6″ for detecting the bladder wall temperature to be safely deflected outwards when ballonon balloon 7 is inflated, the power supply cables thereof are reinforced along their whole length by inserting within the protecting sheath thereof a thin stainless steel wire providing them with the required rigidity and flexibility. The presence of said reinforcing wire provides as well he the thermocouple power supply cables with the mechanical strength necessary to bear the compressive and tensile stresses caused when the cables are inserted within side channel 5, and when thermocouples 6, 6′, 6″ are laid in the desired locations.

When the catheter, provided with all its components, is introduced into the urethral channel, all the way to the bladder, the ends of outer thermocouples 6, 6′, 6″ projecting upstream of balloon 7 through opening 4 are temporarily locked by inserting them, downstream of balloon 7, in one or more notches provided, as the case may be, in suitable positions according to the different body organ or the particular patient to be treated, close to the catheter end, as it is shown in FIG. 6. When balloon 7 is inflated it causes the thermocouple ends to come out from the notches and then to deflect outwards until the thermocouple tips come into engagement with the bladder wall. The particular outwards deflecting system of thermocouples 6, 6′, 6″ causes the ends of the respective power supply cables comprising the actual thermocouple, to tangentially engage the bladder wall, whereby no excessive concentrated pressures are generated. On the other hand, the tangential position taken by the thermocouple tips when contacting the bladder wall, makes it possible to measure the actual temperature of the wall position considered in that at the boundary between said wall and the liquid filling the bladder there is a thin liquid layer substantially stationary, which is not affected by the liquid circulation within the bladder, since it clings to the tissue because of a physical attraction, while the coil shape of the cable terminal stretches increases the thermal capacity of the thermocouple whose diameter, inclusive of the coils, is less than 0,7 mm whereby the thermocouple is completely submerged within the liquid stationary layer having a thickness of approximately 1 mm.

After the thermocouples have been deflected outwards within the bladder, it is still possible to modify their location by performing pushing and/or pulling actions on the reinforced power supply cables, as mentioned above, and possibly by rotating the catheter containing them. Control of the temperature detected on the bladder walls and/or within the circulating liquid mass, is obtained by changing the flowrate of said liquid from few cubic centimeters per minute to several tens of cubic centimeters per minute. The circulated fluid circulating system prevents permanence or formation and build-up of possible gas bubbles within the bladder or through the circuit, in that air or other gas bubbles having possibly formed or being already present, are entrained out by the continuous flow and exhausted to the outer environment in an appropriate position of the outer pumping circuit. In addition, the liquid circulation provided as above presents prevents the antenna and the environment thereof from overheating, therefore from causing undesirable reactions within the circulating liquid.

It is pointed out herein that all the antenna and thermocouple components contacted by the liquid circulating within the bladder are sealingly lined and insulated from the outer environment by a polytetrafluoroethylene layer whereby, after each usage and application they may be sterilized for subsequent further use.

Claims

1. A radiating device for urethral hyperthermia including a catheter provided at its distal end with an inflatable balloon (7) and adapted to receive multiple injected liquid flows (2,5,8) passing therethrough, a radiofrequency radiating antenna (1) and multiple thermocouples (6,6′,6″), the radiating antenna being submerged within said liquid flow, characterized in that

said radiating antenna (1) is submerged within a liquid flow which proceeds through a central channel (2) surrounding said radiating antenna (1) towards the distal end of said catheter and passes from said catheter through a first opening (3) into the bladder to be treated, while flowing back into said catheter towards the proximal end thereof through a second separate opening (4) of a side channel (5) surrounding the power supply cables of said thermocouples (6,6′,6″),

the ends of said thermocouples (6,6′,6″) project out of said second opening (4), being thus deflected outwards into the bladder when said balloon (7) is inflated by injecting a fluid therein through a second side channel (8) and third opening (9), whereby the outwardly deflected ends of said thermocouples (6,6′,6″) come into tangential engagement with the bladder wall (32) irradiated by said antenna (1).

2. A radiating device for irradiating a cavity comprising:

a catheter;

an antenna, situated at a distal portion of the catheter, for irradiating the cavity;

a central channel adapted to provide a fluid to the cavity;

a side channel adapted to receive the fluid from the cavity;

at least one side branch, situated at a proximal portion of the catheter; and

at least one temperature sensing device, having an end, the end of the at least one temperature sensing device extending outward from the catheter after the catheter is inserted into the cavity;

wherein the end of the at least one temperature sensing device is adapted to detect a temperature of a wall of the cavity irradiated by the antenna.

3. The radiating device according to claim 2 wherein the at least one side branch provides an inlet for the fluid to enter the central channel.

4. The radiating device according to claim 2 wherein the at least one side branch provides an outlet for the fluid to exit from the side channel.

5. The radiating device according to claim 2 further comprising:

an inflatable balloon situated at the distal portion of the catheter;

a second side channel adapted to provide a fluid used to inflate the inflatable balloon; and

a one-way valve for introducing the fluid used to inflate the inflatable balloon to the second side channel.

6. The radiating device according to claim 5 wherein the fluid used to inflate the inflatable balloon is a liquid.

7. The radiating device according to claim 5 wherein the fluid used to inflate the inflatable balloon is a gas.

8. The radiating device according to claim 2 wherein the fluid comprises a conditioning liquid.

9. The radiating device according to claim 2 wherein the fluid comprises a solution of a selective cytotoxicity substance.

10. The radiating device according to claim 2 wherein the antenna comprises a linear dipole antenna.

11. The radiating device according to claim 10 wherein the linear dipole antenna comprises a coil-shaped segment.

12. The radiating device according to claim 2 further comprising a stainless steel wire coupled to the at least one temperature sensing device.