Heating potential of iron oxides for therapeutic purposes in interventional radiology.
OBJECTIVE
In addition to their diagnostic applications, iron oxides could be used therapeutically to eliminate tumors with heat if their heating powers are adequate. The authors therefore examined the specific absorption rate (SAR) of different iron oxide (magnetite) samples suspended in water and in liquid or solidified gel.


METHODS
The authors compared two ferromagnetic fine powders (total particle size, >350 nm and 100 nm), five superparamagnetic ferrofluidic samples (total particle size, 10-280 nm), and a commercially available contrast medium (ferumoxides injectable solution, Endorem). The SARs of the magnetic material-suspended in distilled water or in liquid or solid agar-were estimated from time-dependent calorimetric measurements during exposure to an alternating current magnetic field (amplitude, 6.5 kA/m; frequency, 400 kHz).


RESULTS
SARs varied considerably between the different iron oxide samples. The highest value was found for a ferrofluidic sample (>93 W/g), while Endorem had little heating power (<0.1 W/g). The SAR was clearly dependent on the aggregation state of the matrix only for the large-particle-size ferromagnetic sample, yielding the highest values for particle suspensions in water (74 W/g) and lowest for solid agar (8 W/g). The heating power of the smaller-particle-size ferromagnetic sample did not exceed 8 W/g.


CONCLUSIONS
Heating powers differed according to the interaction of multiple physical parameters. Iron oxides should be selected carefully for therapeutic applications in magnetic heating.
Hilger
Ingrid
I
Department of Diagnostic and Interventional Radiology, Klinikum der Friedrich-Schiller-Universität Jena, Germany.
Frühauf
Katrin
K
Andrä
Wilfried
W
Hiergeist
Robert
R
Hergt
Rudolf
R
Kaiser
Werner A
WA
D000042:Absorption; D002151:Calorimetry; D005290:Ferric Compounds / Q000737:chemistry* / Q000627:therapeutic use; D006358:Hot Temperature; D066298:In Vitro Techniques; D015642:Radiology, Interventional
D005290:Ferric Compounds; C000499:ferric oxide