Effects of 50 Hz magnetic fields on mouse spermatogenesis monitored by flow cytometric analysis.

Flow cytometry (FCM) was performed to monitor the cellular effects of extremely-low-frequency magnetic field on mouse spermatogenesis. Groups of five male hybrid F1 mice aged 8-10 weeks were exposed to 50 Hz magnetic field. The strength of the magnetic field was 1.7 mT. Exposure times of 2 and 4 h were chosen. FCM measurements were performed 7, 14, 21, 28, 35, and 42 days after treatment. For each experimental point, a sham-treated group was used as a control. The possible effects were studied by analyzing the DNA content distribution of the different cell types involved in spermatogenesis and using the elongated spermatids as the reference population. The relative frequencies of the various testicular cell types were calculated using specific software. In groups exposed for 2 h, no effects were observed. In groups exposed for 4 h, a statistically significant (P < 0.001) decrease in elongated spermatids was observed at 28 days after treatment. This change suggests a possible cytotoxic and/or cytostatic effect on differentiating spermatogonia. However, further studies are being carried out to investigate the effects of longer exposure times.

Low-frequency RF hyperthermia: IV--A 27 MHz hybrid applicator for localized deep tumor heating.

A 27 MHz dual-device applicator of novel design, which is aimed to heat noninvasively with improved safety tumor masses at depth, is proposed. A substantially localized temperature gain is obtained by superimposing two delocalized low RF frequency and phase-coherent current distributions, which are launched to constructively interfere over a limited region emcompassing the tumor volume. An hybrid applicator (HA) has been developed, integrated one capacitive and one inductive heating device, and has been assessed on a 20 cm diameter cylindrical fat-muscle phantom. The interference pattern is characterized by a deep broad SAR maximum and by the disappearance of the central null SAR value typical of single inductive devices. An 80% SAR useful therapeutic volume (UTV) of a near-cylindrical shape of about 800 cm3 is obtained with a penetration of 6-8 cm for the phantom surface, with a noncritical axial length of approximately 21 cm. The UTV may be somehow controlled in size and penetration. These results are obtained with the tissue-like medium surrounding the UTV heated uniformly and safely to a temperature pedestal below the therapeutic temperature with about half RF power values to each of the heating devices.

27 MHz conformal capacitive ring (CR) applicators for uniform hyperthermic/diathermic treatment of body segments with axial fields.

A family of 27 MHz heating devices has been developed and fundamental tests carried out. The devices consist in a pair of ring-like, flexible, capacitive electrodes, conformally wrapped round the tissue to be heated, for use in hyperthermia and rehabilitation treatment. These capacitive ring (CR) applicators produce an axial E-field which can uniformly heat the central portion of a 20 cm OD cylindrical phantom simulating fat and muscle tissues. This electrode-body configuration can be used to uniformly heat most human body segments with the highest symmetry congruence, the RF currents flowing parallel to the boundaries provided by the pseudo-axial symmetry of these segments. With respect to the rigid pads used in RF capacitive heating, the CR electrodes exhibit a larger working surface area. Moreover, they may be used with an interposed dielectric layer between the electrodes and the skin, to reduce edge effects. With respect to the axially symmetric radiators of higher frequency, they are applicable to larger cross-section body segments with increased penetration and without the need of an integral water bolus. The CR devices allow free access to most of the body surface for skin temperature measurement and conditioning, and for combined treatments. Moreover, the almost uniform heating pattern may represent a useful feature for standardizing treatment. The CR electrodes can easily be matched to the RF source even if they are low impedance devices, and they give rise to low-level stray fields, which can be taken care of by a local shield. These CR devices can be considered safe and practical and suitable for regional hyperthermic and rehabilitation treatment.