Advertisement

Hyperthermia by magnetic induction: I. Physical characteristics of the technique

      This paper is only available as a PDF. To read, Please Download here.

      Abstract

      Several electromagnetic techniques are currently used in hyperthermia therapy for cancer. This report discusses the magnetic induction technique, in which application of an alternating magnetic field to a conductor results in induction of eddy current flow and power deposition via ohmic losses. The power density in tissues depends upon the heterogeneous tissue conductivities and dielectric constants, magnetic field intensity and distribution, and eddy current radius. Using a newly developed magnetic field probe, the magnetic fields produced at 13.56 MHz by electrodes of a commercial magnetic induction device have been accurately mapped and used to calculate power densities in static phantoms. Calculated and observed temperature elevations in a cylindrically symmetric phantom agree well, confirming the simple formula in this case relating power density to magnetic field strength. The efficiencies of three commercially available electrodes have been accurately measured using calorimetric techniques and phantom loads modeling human anatomy and electrical conductivity. The effect of eccentric positioning of the load has been studied using magnetic field mapping techniques. Power densities in a very simplified model of human anatomy that retains cylindrical symmetry were calculated. Effects of inhomogeneities in conductivity have been investigated qualitatively using composite static phantoms modeling human cross-sectional anatomy and thermographic camera recordings of surface temperature distributions. The advantages and disadvantages of this heating technique are discussed from the point of view of the power density distributions in heterogeneous materials. Evaluation of power density distributions is essential for optimizing this heating technique using various electrode arrangements and/or load modifications, for providing part of the information needed for solution of the bioheat transfer equation in living subjects, and for predicting the ability of the technique to heat specific tumors.

      Keywords

      To read this article in full you will need to make a payment
      ASTRO Member Login
      ASTRO Members, full access to the journal is a member benefit. Use your society credentials to access all journal content and features.
      Already a print subscriber? Claim online access
      Already an online subscriber? Sign in
      Institutional Access: Sign in to ScienceDirect

      References

        • Bicher H.I.
        • Hetzel F.W.
        • Sandhu T.S.
        • Frinak B.S.
        • Vaupel P.
        • O'Hara M.D.
        • O'Brien T.
        Effects of hyperthermia on normal and tumor microenvironment.
        Radiology. 1980; 137: 523-530
      1. Bowman, H.F.: Heat transfer mechanisms and thermal dosimetry. J. Natl'. Cancer Inst. (In press).

        • Cetas T.C.
        Practical thermometry with a thermographic camera: Calibration, transmittance and emittance measurements.
        Rev. Sci. Instrum. 1978; 49: 245-254
        • Dewhirst M.W.
        • Moon T.
        • Carlin D.
        Analysis of tumor volume and thermal dosimetric effects on tumor response to heat, radiation, and heat plus radiation: Results of a phase III randomized clinical trial in pet animals.
        in: Presented at the AAPM Summer School, “Physical Aspects of Hyperthermia”, Dartmouth College, Hanover, N.H.August 3–7, 1981
        • Dewhirst M.W.
        • Ozimek E.J.
        • Gross J.
        • Cetas T.C.
        Will hyperthermia conquer the elusive hypoxic cell?.
        Radiology. 1980; 137: 811-817
        • Douglas M.A.
        • Parks L.C.
        • Bebin J.
        Sudden myelopathy secondary to therapeutic total-body hyperthermia after spinal-cord irradiation.
        N. Engl. J. Med. 1981; 304: 583-585
        • Eddy H.A.
        Alterations in tumor microvasculature during hyperthermia.
        Radiology. 1980; 137: 515-521
        • Emami B.
        • Nussbaum G.H.
        • TenHaken R.K.
        • Hughes W.L.
        Physiological effects of hyperthermia: Response of capillary blood flow and structure to local tumor heating.
        Radiology. 1980; 137: 805-809
        • Goflinet D.R.
        • Choi K.Y.
        • Brown J.M.
        The combined effects of hyperthermia and ionizing radiation on the adult mouse spinal cord.
        Radiat. Res. 1977; 72: 238-245
        • Guy A.W.
        Analyses of electromagnetic fields induced in biological tissues by thermographic studies on equivalent phantom models.
        IEEE Trans. on Microwave Theory and Techniques. 1971; MTT-19: 205-214
        • Hahn G.M.
        • Kernahram P.
        • Martinez A.
        • Pounds D.
        • Prionas S.
        • Anderson T.
        • Justice G.
        Some heat transfer problems associated with heating by ultrasound, microwaves, or radiofrequency.
        Ann. NY. Acad. Sci. 1980; 335: 327-345
        • Jackson J.D.
        Classical Electrodynamics.
        John Wiley and Sons, Inc.,, New York1962
        • Miller R.C.
        • Leith J.T.
        • Veomett R.C.
        • Gerner E.W.
        Potentiation of radiation myelitis in rats by hyperthermia.
        Brit. J. Radiol. 1976; 49: 895-896
        • Mortimer B.
        • Osborne S.L.
        Tissue heating by short wave diathermy.
        JAMA. 1935; 104: 1413-1419
        • Oleson J.R.
        An accurate probe for mapping strong HF magnetic fields.
        IEEE Trans. Biomed. Eng. 1982; 8: 581-583
        • Oleson J.R.
        • Gerner E.W.
        Hyperthermia in the treatment of malignancies.
        in: Lehmann J.F. Therapeutic Heat and Cold. 3rd edition. Williams & Wilkins, Baltimore1982: 603-635
        • Pätzold J.
        • Wenk P.
        Zur Wirkungsweise des Spulenfeldes in der Kurzwellentherapie: Wärmemessungen an geschichteten Elektrolyten im hochfrequenten Spulenfeld.
        Strahlentherapie. 1936; 55: 692-707
        • Song C.W.
        • Kang M.S.
        • Rhee J.G.
        • Levitt S.H.
        The effect of hyperthermia on vascular function, pH, and cell survival.
        Radiology. 1980; 137: 795-803
        • Storm F.K.
        • Harrison W.H.
        • Elliott R.S.
        • Hatzitheofilous C.
        • Morton D.L.
        Human hyperthermia therapy: Relationship between tumor type and capacity to induce hyperther mia by radiofrequency.
        Amer. J. Surg. 1979; 138: 170-174
        • Storm F.K.
        • Harrison W.H.
        • Elliott R.S.
        • Morton D.L.
        Normal tissue and solid tumor effects of hyperthermia in animal models and clinical trials.
        Cancer Res. 1979; 39: 2245-2251
        • Storm F.K.
        • Harrison W.H.
        • Elliott R.S.
        • Morton D.L.
        Hyperthermia therapy for human neoplasms: Thermal death time.
        Cancer. 1980; 46: 1849-1854
        • Toler J.
        • Seals J.
        RF dielectric properties measurement system, human and animal data.
        Cincinnati, US Department HEW (NIOSH) publication no. 77-176. 1977;
        • Young J.H.
        • Wang M.T.
        • Brezovich I.A.
        Frequency/depth-penetration considerations in hyperthermia by magnetically induced currents.
        Electron Letters. 1980; 16: 358-359

      Comments

      Commenting Guidelines

      To submit a comment for a journal article, please use the space above and note the following:

      • We will review submitted comments as soon as possible, striving for within two business days.
      • This forum is intended for constructive dialogue. Comments that are commercial or promotional in nature, pertain to specific medical cases, are not relevant to the article for which they have been submitted, or are otherwise inappropriate will not be posted.
      • We require that commenters identify themselves with names and affiliations.
      • Comments must be in compliance with our Terms & Conditions.
      • Comments are not peer-reviewed.