An easy-to-use microwave hyperthermia system combined with spatially resolved MR temperature maps: phantom and animal studies.
BACKGROUND
Hyperthermia has been used in multimodal cancer treatments, and in randomized, controlled studies, hyperthermia is an effective cancer therapy. For clinical accuracy and safety, however, temperature monitoring during treatment is essential. We aimed to develop a convenient microwave hyperthermia system combined with spatially resolved real-time temperature monitoring to improve its efficacy and safety.


METHODS
Using an MR-compatible irradiation-type microwave applicator, agar phantoms, thigh muscles of rabbit, and subcutaneous VX2 tumors of rabbit were heated in combination with noninvasive MR temperature maps. For MR temperature calculation, a proton resonance frequency method was used. After determination of temperature coefficients and evaluation of the precision in MR thermometry, distribution of microwave heating over time was examined for each substance.


RESULTS
The temperature coefficients of phantoms, rabbit muscles, and VX2 tumors were -0.00977, -0.00976, and -0.01027 ppm/ degrees C, respectively. The 95% limits of agreement of MR and fluoroptic thermometry in the three subjects were +0.318/-0.339 degrees C, +0.693/-0.661 degrees C, and +0.564/-0.526 degrees C, respectively. Concerning VX2 tumor, the average tumor temperature was 42.60 +/- 0.14 degrees C and the surface of skin was 43.27 +/- 0.45 degrees C in the 60-min experimental period.


CONCLUSIONS
With this easy-to-use microwave hyperthermia system, effective hyperthermia was accomplished in phantoms and living animals in combination with MR temperature maps.
Department of Surgery, Shiga University of Medical Science, Shiga, Japan. demura@belle.shiga-med.ac.jp
Koichi
K
Demura
Shigehiro
S
Morikawa
Koichiro
K
Murakami
Koichiro
K
Sato
Hisanori
H
Shiomi
Shigeyuki
S
Naka
Yoshimasa
Y
Kurumi
Toshiro
T
Inubushi
Tohru
T
Tani
D000362:Agar; D000818:Animals; D004195:Disease Models, Animal; D006979:Hyperthermia, Induced / Q000379:methods*; D008279:Magnetic Resonance Imaging; D008297:Male; D008872:Microwaves; D018482:Muscle, Skeletal; D009368:Neoplasm Transplantation; D009369:Neoplasms / Q000628:therapy*; D011817:Rabbits; D040521:Subcutaneous Tissue; D013696:Temperature; D013817:Thermography
D000362:Agar