WO2015136553A1

WO2015136553A1 - Improved microwave hyperthermia device

Info

Publication number: WO2015136553A1
Application number: PCT/IN2015/000125
Authority: WO
Inventors: Arunachalam Kavitha; C Geetha
Original assignee: Indian Institute Of Technology Madras
Priority date: 2014-03-13
Filing date: 2015-03-13
Publication date: 2015-09-17

Abstract

An improved microwave hyperthermia device with compact heating applicator and inline degassing for bolus circulation. A family of 434 MHz patch antenna (3x3x1 cm till 10X10X2cm) with varying effective heating area for treating tissue disease of varying extent. The bolus water circulation proposed for the 434 MHz patch antennas is a smart closed loop system capable of removing dissolved micro air bubbles real time during hyperthermia treatment. The patch antenna comprises of a radiating patch mounted on a low loss dielectric substrate which is housed inside a metal cavity and has a low loss superstrate on the patient contacting side. Temperature and flow sensors embedded in the fluid flow path can measure the temperature and flow of fluids which can be further sampled and fed to the control unit/computer for process control. A closed loop application running on the control unit/computer sends the control signals to the pump and water heater to circulate degassed temperature controlled water at a constant flow rate.

Description

IMPROVED MICROWAVE HYPERTHERMIA DEVICE

TECHNICAL FIELD

[0001] The present invention relates to medical devices and equipments. The present invention also relates to hyperthermia devices for performing an extreme hyperthermia treatment for therapeutical purposes. Further, the present invention specifically relates to an improved microwave hyperthermia device with compact heating applicator and inline degassing for bolus circulation.

BACKGROUND OF THE INVENTION

[0002] Thermal therapy devices are well known in the art for treatment and management of diseases in a mammalian. Thermal therapy consists of raising the temperature of living tissues until they are destroyed. This type of treatment can be divided into two main groups: hyperthermia in which the temperatures reach up to 46°C and thermal ablation in which the temperature exceeds- 50°C.1¾en9dk therapy, and in particular hyperthermia, have been used to intensify radio and chemotherapy treatments; tumor tissues are more sensitive to heat than healthy tissues and additionally the temperature increase sensitises the cancer cells to chemotherapy and radiation treatments. In experimental and clinical oncology, hyperthennia treatments have already been used to raise the temperature of affected areas to 40-46°C.

[0003] A conventional hyperthermia device generally employs an applicator which enables heat transfer to the target tissue. The commonly used heating mechanisms are acoustic and electromagnetic (EM) techniques. In EM techniques, capacitive, inductive, radiated and laser assisted heating modalities are available ii the clinic. Within each modality, the type of applicators is categorized as external, interstitial, intra cavitary and intra luminal. Depending on the extent and locatioi of target tissue and, physician's expertise, the mode of heat delivery is varied

Devices are typically developed in industrial scientific and medicine(ISM) frequencies for clinical use. Lower EM frequencies, 70 and 434 Mi¾ are used for larger and deeper tissues and higher frequencies 915 and 2450 MHz are used for superficial tissue diseases.

[0004] Fig. 1 illustrates an exemplary prior art hyperthermia device 100 using an applicator (microwave antenna) coupled to the tissue through a surface cooling temperature controlled water bolus. Hyperthennia devices developed at 434 MHz include dielectric loaded waveguide and horn antennas. Clinically available hyperthermia antennas at 434 MHz are bulky with fixed effective heating areas. Hence, their ability to treat varying size tissue diseases is limited. Irrespective of the applicator used for hyperthermia devices 100, heat is delivered to the target tissue through a coupling medium often referred as the bolus.

[0005] The bolus typically reduces impedance mismatch and couples power delivered by the applicator to the tissue, regulates temperature distribution on the interface between applicator and tissue, and avoids thermal burns at tissue- applicator interface and, control location of the hot spot in the tissye by varying bolus temperature. Such features can be accomplished by circulating temperature controlled fluid (typically 37°C - 42°C) inside the bolus and maintaining uniform volume during treatment. The commonly used coupling medium is deionized water. Bolus liquid of varying impedance can be achieved by mixing water in low dielectric constant fluid such as glycerin, ethylene glycol. During thermal therapy, power delivered by the applicators is partly dissipated in the coupling bolus due to the non-zero loss tangent of the coupling fluid which aids in the release of dissolved gases in the circulating liquid. Power delivered for 30-60 minutes duration during typical hyperthermia treatment causes release of dissolved gases in the form of micro air bubbles which adheres to the bolus surface adjacent to the antenna and the tissue contacting side of the applicator.

[0006] EM radiation from the antenna is partly reflected by the air bubbles thereby reducing power coupled to the tissue and alters tissue temperature during hyperthermia treatment. Tissue temperature drop due to impedance mismatd caused by air bubbles is compensated during treatment

power deli vered by the power amplifier. Thus, output power of amplifiers used in thermal therapy is typically larger than what is required to account for power reflection during treatment. The large safety factor results in higher system cost. Fig. 2 illustrates a prior art bolus circulation system used in clinical thermal therapy devices. During HIFU treatment, tissue temperature is elevated above 70°C for couple of minutes to ablate the target tissue. This is an invasive procedure applicable for small target volumes. In contrast, hyperthermia treatment is delivered for 60 minutes during which target tissue is maintained at 40-46°C for reversible cell damage. Due to high temperature and smaller applicator size, power reflection due to bubble formation is a serious problem during HIFU treatment.

[0007] Based on the foregoing, it is believed that a need exists for an improved microwave hyperthermia device with compact heating applicator and inline degassing for bolus circulation, as described in greater detail herein. SUMMARY OF THE INVENTION

[0008] The following summary is provided to facilitate an understanding of some of the innovative features unique to the disclosed embodiment and is not intended to be a full description. A full appreciation of the various aspects of the embodiments disclosed herein can be gained by taking the entire specification, claims, drawings, and abstract as a whole.

[0009] It is, therefore, one aspect of the disclosed embodiments to provide for an improved microwave hyperthermia device.

[0010] It is another aspect of the disclosed embodiments to provide for improved hyperthermia device with compact heating applicator.

[0011] It is further aspect of the disclosed embodiments to provide for improved low cost inline degassing for bolus circulation. [0012] The aforementioned aspects and other objectives and advantages can now be achieved as described herein. An improved microwave hyperthermia device with compact heating applicator and inline degassing for bolus circulation, is disclosed herein. A family of 434 MHz patch antenna with varying effective heating area for treating tissue disease of varying extent 12-100 sq cm. The bolus water circulation proposed for the 434 MHz patch antennas is a smart closed loop system capable of removing dissolved micro air bubbles real time during hyperthermia treatment.

[0013] The patch antenna comprises of a radiating patch mounted on a low loss dielectric substrate. Temperature and flow sensors embedded in the fluid flow path can measure the temperature and flow of fluids which can be further sampled and fed to the control unit/computer for process control. A closed loop application running on the control unit/computer sends the control signals to the pump and water heater to circulate degassed temperature controlled water at a constant floM ate.

[0014] The permittivity of the low loss dielectric substrate can be increased from 4-80 and the patch dimensions can be scaled down accordingly for resonance at 434 MHz. Such feasibility in the design of the substrate and patch facilitates to develop 434 MHz patch antennas with effective heating area varying between 12- 100 sq. cm for hyperthermia treatment of superficial cancers/tissue diseases. Since the signal source required for the varying size patch antennas is the same, system cost and complexity associated with treatment delivery and feedback system for power control remains the same. Large treatment area is also possible using at plurality of same sized antennas resonant at 434 MHz.

[0015] Bolus water circulation proposed for the 434 MHz patch eliminates the need for off-line degassing or human intervention in the system by making it suitable for other thermal therapy applicators that require a coupling fluid. The proposed inline degasser employs a single peristaltic pump and does not require i gas permeable filter. Instead it employs a simple system design εμφ robust control algorithm for inline degassing.

[0016] The improved microwave hyperthermia device disclosed herein can be a compact model when compared to dielectric loaded waveguide and horn antennas at 434 MHz (10x10x10 cm). The different sized patch applicator with varying effective heating area accommodates varying extent tissue diseases. The device comprises a single or plurality of microwave sources for power deposition through one or multiple antennas, and power sensors for monitoring and controlling power delivered during the treatment. The device proposed herein can be used inside the MR scanner to obtain 3D tissue temperature distribution for volumetric thermal dose calculation and, provide real time feedback to control amplitude and power delivered to antennas for deep seated tissue heating. Motion artifacts due to water circulation in the MR compatible heating during thermal therapy with 3D MH based tissue thermometry can be eliminated using D 0 (heavy water) as a coupling medium. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying figures, in which like reference numerals refer to identical or functionally-similar elements throughout the separate views and which are incorporated in and form a part of the specification, further illustrate the present invention and, together with the detailed description of the invention, serve to explain the principles of the present invention.

[0018] Fig. 1 illustrates an exemplary prior art hyperthermia device 100 using an applicator (microwave antenna) coupled to the tissue through a surface cooling temperature controlled water bolus;

[0019] Fig. 2 illustrates a prior art bolus circulation system used in clinical thermal therapy devices;

[0020] FIG. 3 illustrates the top view of a folded 434 MHz patch antenna for microwave hyperthermia device, in accordance with the disclosed embodiments;

[0021] FIG. 4 illustrates a side view of the folded 434 MHz patch antenna 300 for microwave hyperthermia device, in accordance with the disclosed embodiments; and

[0022] FIG. 5 illustrates a low cost inline degassing for bolus circulation in the hyperthermia device, in accordance with the disclosed embodiments.

DETAILED DESCRIPTION

[0023] The particular values and configurations discussed in these non-limiting examples can be varied and are cited merely to illustrate at least one embodiment and are not intended to limit the scope thereof.

[0024] The embodiments now will be described more fully hereinafter with reference to the accompanying drawings, in which illustrative embodiments of the invention are shown. The embodiments disclosed herein can be embodied in many different forms and should not be construed as limited to the embodiments set fortl herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items. [0025] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

[0026] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should e interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0027] FIG. 3 illustrates the top view 300 of a folded 434 MHz patch antenna for microwave hyperthermia device, in accordance with the disclosed embodiments. The microwave hyperthermia device disclosed herein can be an improved microwave hyperthermia device with compact heating applicator and inline degassing for bolus circulation. A family of 434 MHz patch antenna

(varying 3x3x10 cm till 10X10X2cm) 100 with varying effective heating area for treating tissue disease of varying extent. The patch antenna 300 comprises of a radiating patch mounted on a low loss dielectric substrate. Temperature and How sensors embedded in the fluid flow path can measure the temperature and flow cf fluids which can be further sampled and fed to the control unit/computer for process control. A closed loop application running on the control unit/computer sends the control signals to the pump and water heater to circulate degassei temperature controlled water at a constant flow rate.

[0028] FIG. 4 illustrates a side view 400 of the folded 434 MHz patch antenna

300 for microwave hyperthermia device, in accordance with the disclosed embodiments. The permittivity of the low loss dielectric substrate can be increased from 4-80 and the patch dimensions can be scaled down for resonance at 434 MHz.

Such feasibility in the design of the substrate and patch facilitates to develop 434

MHz patch antennas with effective heating area varying between 12-100 sq. cm for hyperthermia treatment. Since the signal source required for the varying size patch antennas is the same, system cost and complexity associated with treatment delivery and feedback system for power control remains the same.

[0029] The applicator of the hyperthermia device can be a folded patch antenna

300 with a conformal variable volume bolus bag. The external body is made of

Aluminum and is light weight. The patch is fed by a coaxial line, where TEN mode is maintained. Reactive loading of the patch is done to reduce the overall size of the applicator for operation at 434 MHz. The subsj¾ate and superstrate permittivity can be varied from 4-80 using available low loss dielectric materials. As the permittivity is lowered the dimensions of the patch increases and is optimized for resonance at 434 MHz. Thus antenna substrate and superstrate can be varied to suit treatment area. Patch miniaturization for a given substrate and superstrate combination is achieved using a metal cavity surrounding the patch antenna, patch folding and/or meandering and patch reactive loading. The metal cavity provides stable resonance at 434 MHz and antenna is less susceptible to variation in tissue load.

[0030] Lower permittivity substrate and superstrate gives larger patch antennas thereby larger effective heating area. Patch antennas designed with varying permittivity for the substrate and superstrate is proposed for treating varying extent tissue diseases. The power reflections were measurements acquired for the fabricated folded patch antenna on volunteers. Comparison between measurements and simulation indicate good agreement with resonance near 434 MHz. [0031] FIG. 5 illustrates a low cost inline degassing for bolus circulation 400 in the hyperthermia device, in accordance with the disclosed embodiments. The bolus water circulation proposed for the 434 MHz patch antennas is a smart closed loop system capable of removing dissolved micro air bubbles real time during hyperthermia treatment. Bolus water circulation proposed for the 434 MHz patch antenna eliminates the need for off-line degassing or human intervention in the system by making it suitable for other thermal therapy applicators that require a coupling fluid. The proposed inline degasser employs a single peristaltic pump and does not require a gas permeable filter. Instead it employs a simple system design and robust control algorithm for inline degassing.

[0032] The improved microwave hyperthermia device disclosed herein can be ι compact model when compared to dielectric loaded waveguide and horn antennas at 434 MHz (10x10x10 cm). The different sized patch applicator with varying effective heating area accommodates varying extent tissue diseases. The device comprises a single microwave source and power sensor for monitoring and controlling power delivered during the treatment. The device proposed herein can be used with MR compatible thermal therapy devices. The device also eliminates the issues with power coupling and motion artifacts during thermal therapy using MR thermometry for volumetric dose calculation by using D20 as a coupling medium. A heating device comprising of a spatial arrangement of several patch antennas could also be constructed to deposit focused energy in deep seated tumor/target tissue.

[0033] It will be appreciated that variations of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art whict are also intended to be encompassed by the following claims.

Claims

CLAIMS I/We Claim:

1. An improved microwave hyperthermia device with compact heating applicator and inline degassing for bolus circulation, said device comprising:

a plurality of patch antennas with varying effective heating area for treating tissue disease of varying extent wherein said plurality of patch antennas comprises of a radiating patch mounted on a low loss dielectric substrate;

an inline degassing bolus water circulation for said plurality of patch antennas forming a smart closed loop unit capable of removing dissolved micro air bubbles real time during hyperthermia treatment.

2. The device of claim 1 further comprising a control unit having a closed loop application which sends control signals to pump and water heater thereby circulate degassed temperature controlled water at a constant flow rate wherein said control unit receives feeds on measurement of temperature and flow of fluids in the flov path.

3. The device of claim 1 wherein said plurality of patch antennas with effective heating areas can be developed by increasing the permittivity of the low loss dielectric substrate from 4-80 and scaling the patch dimensions down accordingly for resonance at 434 MHz.

4. The device of claim 1 wherein said inline degassing bolus water circulation proposed for the plurality of patch antennas eliminates the need for off-line degassing or human intervention.

5. The device of claim 1 wherein said inline degassing bolus water circulation proposed inline employs a single peristaltic pump which is simple design and robust control algorithm for inline degassing.

6. The device of claim 1 wherein said plurality of patch antennas comprises 434 MHz patch antennas with effective heating area varying between 12-100 sq. cm.

7. The device of claim 1 wherein said plurality of patch antennas can be configured by increasing the heating area to larger treatment area.

8. The device of claim 2 wherein said control unit receives/sends control signals via a wired communication.

9. The device of claim 2 wherein said control unit receives/sends control signals via a wireless communication.