Changes in muscle temperature induced by 434-MHz microwave hyperthermia

Noriko Ichinoseki-Sekine ^1*, Hisashi Naito ¹, Norio Saga ¹, Yuji Ogura ¹, Minoru Shiraishi ², Arrigo Giombini ³, Valentina Giovannini ⁴ and Shizuo Katamoto ¹

¹ Juntendo University, Japan
² Jikei University School of Medicine, Japan
³ Sport Medicine Laboratory-IUSM, Italy
⁴ Restek Medical Dev., Italy

^* To whom correspondence should be addressed. E-mail: noriko.sekine{at}sakura.juntendo.ac.jp.

Accepted 10 January 2007

Abstract

Objective: This study investigated the changes in temperature of human muscle during microwave hyperthermia.

Methods: Skin surface and muscle temperatures were measured in 11 healthy adult males (age 24.3±2.2 yrs; height 174.2±6.1 cm; weight 70.0±5.3 kg) during a 30 min exposure of the thigh to 434-MHz microwave hyperthermia. The skin temperature was maintained at the pilot temperature of 40°C, and the temperature of the water in the bolus was 38°C. The peak power output was set at 60 W and controlled automatically to maintain the pilot temperature. Muscle temperature was measured in the vastus lateralis muscle at an average muscle depth of 2.0±0.2 cm using a 23-G Teflon-shielded thermocouple. Biopsy specimens were obtained for light microscopy from three subjects. A muscle equivalent phantom was used to evaluate the vertical heating pattern.

Results: Both of the skin and muscle temperature increased from baseline, and the muscle temperature was higher than the skin temperature (skin 39.2±0.5°C; temperature rise: 5.0±1.5°C, muscle 43.7±0.8°C; temperature rise: 8.9±1.4°C). At the end of the hyperthermia treatment, the muscle temperature decreased to 39.8±0.9°C, but it was still 4.8±1.5°C higher than baseline. No signs of muscle damage were observed based on blood creatine kinase activity and histological sections.

Conclusions: Our results show that the 434-MHz microwave hyperthermia treatment increased and maintained the muscle temperature locally by 6.3-11.4°C without muscle damage. These findings suggest that the microwave hyperthermia system provides effective and safe treatment.

Key Words: hyperthermia, microwave, muscle temperature, vastus lateralis muscle

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