title: An HF exposure system for mice with improved efficiency.
abstract: An exposure system that addresses difficulties that arise for exposure of small animals at low frequencies with a high exposure level is presented. The system, intended to operate at 27 MHz, consists of two identical transverse electro-magnetic (TEM) cells for exposure and sham exposure of groups of 16 free-running mice housed in pairs within standard cages, capable of exposure over extended daily periods while being provided food and water. Inclusion of the exposure cell in a half-wavelength resonator has been developed as a new paradigm to enhance field strength for an increase of >50-fold in available specific absorption rate (SAR) levels compared to traditional TEM cell configurations. The system described allows both daily and weekly exposure schedules and supports blinded protocols with continuous wave (CW) and amplitude modulation (AM) signals with programmable modulation depths and frequencies. Electric field (E-field) homogeneity across the TEM cell along a vertical plane (orthogonal to the axis of the TEM line) was within 3.3%, and 3.1% along the horizontal plane. Accurate and comprehensive dosimetric assessments based on whole-body and organ-specific SAR essential for in vivo bioelectromagnetic experiments are presented, which takes into account various factors (e.g., mouse activities, close proximity, and field homogeneity). Average SAR levels are controllable in the range of 1 mW/kg to 2 W/kg, with expanded uncertainty (k = 2) of 1 dB and instantaneous variation (k = 1) of 4 dB.
authors.affiliation: IT'IS Foundation, ETH Zürich, Zürich, Switzerland.
authors.forename: Myles
authors.initials: M
authors.lastname: Capstick
authors.affiliation: IT'IS Foundation, ETH Zürich, Zürich, Switzerland.|Integrated System Laboratory, ETH Zürich, Zürich, Switzerland.
authors.forename: Yijian
authors.initials: Y
authors.lastname: Gong
authors.affiliation: Department of Cancer Biology, Wake Forest Baptist Comprehensive Cancer Center, Winston-Salem, North Carolina.
authors.forename: Boris
authors.initials: B
authors.lastname: Pasche
authors.affiliation: IT'IS Foundation, ETH Zürich, Zürich, Switzerland.|Integrated System Laboratory, ETH Zürich, Zürich, Switzerland.
authors.forename: Niels
authors.initials: N
authors.lastname: Kuster
mesh_terms: D065638:Absorption, Radiation; D000818:Animals; D004574:Electromagnetic Fields / Q000009:adverse effects; D051379:Mice; D009928:Organ Specificity; D000069079:Radiation Exposure / Q000032:analysis*; D011834:Radiation Monitoring / Q000295:instrumentation*; D035501:Uncertainty; D014916:Whole-Body Irradiation / Q000009:adverse effects
keywords: AM RF EMF; dosimetry; numerical; resonant TEM cell; rodent exposure; therapeutic frequencies