Electromagnetic heating of breast tumors in interventional radiology: in vitro and in vivo studies in human cadavers and mice.
OBJECTIVE
To assess relevant parameters for the minimally invasive elimination of breast tumors by using a selective application of magnetite and exposure of the breast to an alternating magnetic field.


METHODS
The specific absorption rate (SAR) of different magnetite samples was determined calorimetrically. Temperature elevations based on magnetite mass (7-112 mg) and magnetic field amplitude (1.2-6.5 kA/m frequency, 400 kHz) were investigated by using human breast tissue. Parameter combinations (21 mg +/- 9 [SD], 242-second magnetic field exposure, 6.5-kA/m amplitude) were tested in 10 immunodeficient mice bearing human adenocarcinomas (MX-1 cells). Histologic sections of heated tumor tissue were analyzed.


RESULTS
SAR data of different magnetite particle types ranged from 3 to 211 W/g. Temperature elevation (DeltaT) as a function of the magnetite mass increased linearly up to 28 mg; at higher masses, a saturation of DeltaT was observed at nearly 88 degrees C. The dependence of DeltaT on magnetic field amplitude (H) revealed a third-order power law: DeltaT = 0.26 degrees C/(kA/m)(3). H(3), with r(2) = 0.95. A mean temperature of 71 degrees C +/- 8 was recorded in the tumor region at the end of magnetic field exposure of the mice. Typical macroscopic findings included tumor shrinkage after heating. Histologically nuclear degenerations were observed in heated malignant cells.


CONCLUSIONS
Magnetic heating of breast tumors is a promising technique for future interventional radiologic treatments.
Hilger
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Institutes of Diagnostic and Interventional Radiology, Clinics of Friederich Schiller University Jena, Bachstrasse 18, D-07740 Jena, Germany.
Andrä
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Hergt
R
R
Hiergeist
R
R
Schubert
H
H
Kaiser
W A
WA
D000818:Animals; D001943:Breast Neoplasms / Q000628:therapy*; D002102:Cadaver; D055590:Electromagnetic Phenomena; D005260:Female; D052203:Ferrosoferric Oxide; D006801:Humans; D006979:Hyperthermia, Induced / Q000379:methods*; D066298:In Vitro Techniques; D007501:Iron / Q000493:pharmacokinetics / Q000627:therapeutic use*; D008325:Mammary Neoplasms, Experimental / Q000628:therapy*; D051379:Mice; D008815:Mice, Inbred Strains; D009368:Neoplasm Transplantation; D010087:Oxides / Q000493:pharmacokinetics / Q000627:therapeutic use*; D015642:Radiology, Interventional
D010087:Oxides; D007501:Iron; D052203:Ferrosoferric Oxide