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A microwave hyperthermia treatment and thermometry system
Int. J. Radiation Oncology Bid. Phys., Vol. 5, pp. 2113-2115 a Pergamon Press Ltd., 1979. Printed in the U.S.A.
036@3016/79/112113-03$02.00/0
??Technical Innovations and Notes
A MICROWAVE HYPERTHERMIA TREATMENT AND THERMOMETRY SYSTEM? WALTERJ. KoPEcKY,P~.D.~~~ CARLOS A.PEREz,M.D. Division of Radiation Oncology, The Edward Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, Missouri 633110 Studies involving the clinical use of hyperthermia either alone or in conjunction with radiation have been implemented across the country at several institutions. Many of these protocols suggest the use of microwaves as a heating modality with a very specific temperature range. A microwave heating system and an associated thermometry system is described that will meet the needs of these protocols. This equipment was used in the treatments of 42 patients in the 1978 calendar year. Hyperthermia,
Microwave,
Clinical equipment.
INTRODUCTION
The design of these applicators has been described elsewhere. 6 The thermometry system is shown below the generator. It consists of a dual channel strip chart recorder,** thermistor probes,t each feeding into an analog readout unit.t Tumor core and tumor surface probes occupy the two channels of the strip chart recorder. The probes which are used are 24 gauge diameter hypodermic needles with a thermistor chip imbedded approximately 2-3 mm from the tip of the needle. A normal tissue surface probe is also used and is recorded manually by reading the third analog readout unit. The trace from the strip chart recorder is kept in the patient file for each treatment in order to provide a permanent record of the hyperthermia temperature profile. The thermometry system is calibrated monthly against a mercury thermometer whose calibration is traceable to the National Bureau of Standards. The calibration is accomplished using two water baths (30°C and 48°C) in order to establish a “calibration range” on the chart recorder. A spot check is then performed at the clinical treatment temperatures (42-43”C). Since the clinical protocols we are using require hyperthermia post irradiation, the thermistor probes are inserted after the radiation treatment and are
has been suggested as a possible adjuvant to radiation therapy. Biological data5,’ suggests that heat alone has a tumoricidal effect. Recently Phase I and II clinical hyperthermia protocols have been implemented by participating organizations such as the Radiation Therapy Oncology Group in order to collect data on the effectiveness of hyperthermia as a clinical modality. In order to meet the objectives of these protocols we have constructed a hyperthermia treatment system in conjunction with a thermometry system. Figure 1 shows the system that is used in the clinical treatment area at this institution. The microwave generator is at the top of the cart;* it has both variable power output and variable frequency (400 MHz-1000 MHz) capabilities. The output of the generator is fed into an isolator which is used to permit full forward power to pass but absorbs all but a fraction of the reflected power. This is because the generator has a built-in circuit which will place itself in a stand-by mode if the reflected power is greater than 10 watts. The output of the isolator is then fed into a double stub tuner which is used to control mismatches between the applicator and the patient surface; these are caused by slight changes in patient position that occur during the course of treatment. Hyperthermia
tThis work supported in part by Tumor Biology Research Training Grant No. 5-T32-CA 09118-03, National Institutes of Health, Bethesda, Maryland. Reprint requests to: Walter J. Kopecky, Ph.D., Physics Section, Division of Radiation Oncology, The Edward Mallinckrodt Institute of Radiology, Washington Univer-
sity School of Medicine, St. Louis, Missouri 63110. *MCL Corporation. **Hewlett-Packard Corporation. SYellow Springs Instruments. Accepted for publication 29 August 1979. 2113
Radiation Oncology 0 Biology 0 Physics
2114
Fig. 1. Microwave generator, applicator in a treatment area.
thermometry
system
November-December 1979, Vol. 5, No. 11 and No. 12
and
Fig. 3. Typical plate/adaptor.
Fig. 2. Applicator
in place on superficial
machine.
oriented perpendicular to the microwave electric field so they don’t induce localized probe heating. Additionally these probes are sufficiently shielded so they are not affected by stray radio frequency radiation which may produce erroneous temperature readings.
applicator
with threaded
stud and flange
Figure 2 demonstrates how we attach the microwave applicator to a superficial x-ray unit.* This applicator is typical of several which are available in our clinic. The thermal distributions produced by this applicator have been published elsewhere.1,2,3,4*6 Since some of the applicators used in hyperthermia work are dielectric filled, the weight of the applicators becomes a major concern in trying to localize the microwave beam. The treatment arm on the superficial unit (because of the sturdiness of construction and the movement flexibility) proved to be ideally suited for holding the applicator. Each applicator has a small threaded flange attached to the top; this in turn is screwed onto the adaptor plate which has a threaded stud attached to it as shown in Figure 3. If the protocol requires combined treatment (radiation plus Hyperthermia) it is very easy to remove the x-ray collimator from the superficial tube and insert in its place the applicator with its accompany adaptor. From our experience in executing
*Picker Corp.
Microwave treatment system 0 W. J. KOPECKY and C. A. PEREZ
over 200 patient treatments we have found this systern to be very versatile and adaptable to existing and future clinical hyperthermia protocols.
2115
A detailed list of the equipment manufacturers, addresses, and part numbers is available upon request from the authors.
REFERENCES Field Theory of Guided Waves. Collin, R.E.: McGraw-Hill, New York, 1960, Ch. 7, pp. 258-313. in phantom 2. Ho, H.S.: Contrast of dose distributions heads due to aperture and plane wave sources. Ann. 1975. N.Y. Acad. Sci. 247: 45U73, 3. Ho, H.S., Fadeu, J.: Experimental and theoretical determination of absorbed microwave dose rate distributions in phantom heads irradiated by an aperture source. Health Physics 33: 13-21, 1977. 4. Magin, R.L., Kantor, G.: Comparison of the heating patterns of small microwave (2450 MHz) applicators. J. of Bioengineering 1: 493-509, 1977. 1.
5. Robinson, J.E., Wizenberg, M.J.: Proceedings of the International Symposium on Cancer Therapy by Hyperthermia and Radiation, Bethesda, MD. Philadelphia,
American College of Radiology, 1976, pp. 1-161. T.S., Kowal, H.S., Johnson, R.: The development of microwave hyperthermia applicators. I. J. Rad. Oncology, Biol. and Phys. 4: 515-519, 1978. 7. Streffer, C. et al.: Cancer Therapy by Hyperthermia and Radiation, Streffer, C., van Beumingen, D., GieBen, F. Dietzel, Rottinger, J.E., Robinson, J.E., Scherer, E., Seeber, S., and Trott, K.-R., Eds. Baltimore, Urban and Schwarzenberg, 1978, pp. 3-396. 6. Sandhu,
036@3016/79/112113-03$02.00/0
??Technical Innovations and Notes
A MICROWAVE HYPERTHERMIA TREATMENT AND THERMOMETRY SYSTEM? WALTERJ. KoPEcKY,P~.D.~~~ CARLOS A.PEREz,M.D. Division of Radiation Oncology, The Edward Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, Missouri 633110 Studies involving the clinical use of hyperthermia either alone or in conjunction with radiation have been implemented across the country at several institutions. Many of these protocols suggest the use of microwaves as a heating modality with a very specific temperature range. A microwave heating system and an associated thermometry system is described that will meet the needs of these protocols. This equipment was used in the treatments of 42 patients in the 1978 calendar year. Hyperthermia,
Microwave,
Clinical equipment.
INTRODUCTION
The design of these applicators has been described elsewhere. 6 The thermometry system is shown below the generator. It consists of a dual channel strip chart recorder,** thermistor probes,t each feeding into an analog readout unit.t Tumor core and tumor surface probes occupy the two channels of the strip chart recorder. The probes which are used are 24 gauge diameter hypodermic needles with a thermistor chip imbedded approximately 2-3 mm from the tip of the needle. A normal tissue surface probe is also used and is recorded manually by reading the third analog readout unit. The trace from the strip chart recorder is kept in the patient file for each treatment in order to provide a permanent record of the hyperthermia temperature profile. The thermometry system is calibrated monthly against a mercury thermometer whose calibration is traceable to the National Bureau of Standards. The calibration is accomplished using two water baths (30°C and 48°C) in order to establish a “calibration range” on the chart recorder. A spot check is then performed at the clinical treatment temperatures (42-43”C). Since the clinical protocols we are using require hyperthermia post irradiation, the thermistor probes are inserted after the radiation treatment and are
has been suggested as a possible adjuvant to radiation therapy. Biological data5,’ suggests that heat alone has a tumoricidal effect. Recently Phase I and II clinical hyperthermia protocols have been implemented by participating organizations such as the Radiation Therapy Oncology Group in order to collect data on the effectiveness of hyperthermia as a clinical modality. In order to meet the objectives of these protocols we have constructed a hyperthermia treatment system in conjunction with a thermometry system. Figure 1 shows the system that is used in the clinical treatment area at this institution. The microwave generator is at the top of the cart;* it has both variable power output and variable frequency (400 MHz-1000 MHz) capabilities. The output of the generator is fed into an isolator which is used to permit full forward power to pass but absorbs all but a fraction of the reflected power. This is because the generator has a built-in circuit which will place itself in a stand-by mode if the reflected power is greater than 10 watts. The output of the isolator is then fed into a double stub tuner which is used to control mismatches between the applicator and the patient surface; these are caused by slight changes in patient position that occur during the course of treatment. Hyperthermia
tThis work supported in part by Tumor Biology Research Training Grant No. 5-T32-CA 09118-03, National Institutes of Health, Bethesda, Maryland. Reprint requests to: Walter J. Kopecky, Ph.D., Physics Section, Division of Radiation Oncology, The Edward Mallinckrodt Institute of Radiology, Washington Univer-
sity School of Medicine, St. Louis, Missouri 63110. *MCL Corporation. **Hewlett-Packard Corporation. SYellow Springs Instruments. Accepted for publication 29 August 1979. 2113
Radiation Oncology 0 Biology 0 Physics
2114
Fig. 1. Microwave generator, applicator in a treatment area.
thermometry
system
November-December 1979, Vol. 5, No. 11 and No. 12
and
Fig. 3. Typical plate/adaptor.
Fig. 2. Applicator
in place on superficial
machine.
oriented perpendicular to the microwave electric field so they don’t induce localized probe heating. Additionally these probes are sufficiently shielded so they are not affected by stray radio frequency radiation which may produce erroneous temperature readings.
applicator
with threaded
stud and flange
Figure 2 demonstrates how we attach the microwave applicator to a superficial x-ray unit.* This applicator is typical of several which are available in our clinic. The thermal distributions produced by this applicator have been published elsewhere.1,2,3,4*6 Since some of the applicators used in hyperthermia work are dielectric filled, the weight of the applicators becomes a major concern in trying to localize the microwave beam. The treatment arm on the superficial unit (because of the sturdiness of construction and the movement flexibility) proved to be ideally suited for holding the applicator. Each applicator has a small threaded flange attached to the top; this in turn is screwed onto the adaptor plate which has a threaded stud attached to it as shown in Figure 3. If the protocol requires combined treatment (radiation plus Hyperthermia) it is very easy to remove the x-ray collimator from the superficial tube and insert in its place the applicator with its accompany adaptor. From our experience in executing
*Picker Corp.
Microwave treatment system 0 W. J. KOPECKY and C. A. PEREZ
over 200 patient treatments we have found this systern to be very versatile and adaptable to existing and future clinical hyperthermia protocols.
2115
A detailed list of the equipment manufacturers, addresses, and part numbers is available upon request from the authors.
REFERENCES Field Theory of Guided Waves. Collin, R.E.: McGraw-Hill, New York, 1960, Ch. 7, pp. 258-313. in phantom 2. Ho, H.S.: Contrast of dose distributions heads due to aperture and plane wave sources. Ann. 1975. N.Y. Acad. Sci. 247: 45U73, 3. Ho, H.S., Fadeu, J.: Experimental and theoretical determination of absorbed microwave dose rate distributions in phantom heads irradiated by an aperture source. Health Physics 33: 13-21, 1977. 4. Magin, R.L., Kantor, G.: Comparison of the heating patterns of small microwave (2450 MHz) applicators. J. of Bioengineering 1: 493-509, 1977. 1.
5. Robinson, J.E., Wizenberg, M.J.: Proceedings of the International Symposium on Cancer Therapy by Hyperthermia and Radiation, Bethesda, MD. Philadelphia,
American College of Radiology, 1976, pp. 1-161. T.S., Kowal, H.S., Johnson, R.: The development of microwave hyperthermia applicators. I. J. Rad. Oncology, Biol. and Phys. 4: 515-519, 1978. 7. Streffer, C. et al.: Cancer Therapy by Hyperthermia and Radiation, Streffer, C., van Beumingen, D., GieBen, F. Dietzel, Rottinger, J.E., Robinson, J.E., Scherer, E., Seeber, S., and Trott, K.-R., Eds. Baltimore, Urban and Schwarzenberg, 1978, pp. 3-396. 6. Sandhu,