||Fort Sam Houston, TX 78234
Radiofrequency (RF) dosimetry depends largely on computational models that predict the specific absorption rate (SAR) of tissues based on their material properties. These SAR maps, although powerful, require empirical validation in the form of in vivo dosimetry. Model validation usually involves the direct/indirect measurement of temperature dynamics within a tissue during and after RF exposure. While the use of temperature measuring devices imbedded in the tissues is possible, it can lead to erroneous measurements and, in some cases, especially when involving the brain; it can cause the death of the animal. Another challenge arises when researchers need to measure RF-induced temperature changes in structures/tissues responsible for thermoregulation. Typically, this is not an issue for short (acute) exposures, but for longer exposures (chronic), placing temperature-measuring probes into a structure like the hypothalamus is challenging as doing so could affect the animals ability to thermoregulate.
My lab investigates the use of either naturally occurring or transgenic animal models that may be used as “living dosimeters” for RF exposure. We are currently investigating the utility of both invertebrate (Drosophlia melanogaster, Caenorhabditis elegans) and vertebrate (Mus musculus) animal models including transgenic versions of each. Our lab possess a small animal imaging system (PerkinElmer IVIS SpectrumCT) capable of detecting bioluminescence, fluorescence, and Cherenkov radiation from either transgenic animals or animals injected with a luminescent tracer. The power of this particular system lies in its ability to pinpoint the source of the light within the animal’s body and co-register that location with a micro-computed tomography scan producing a detailed 3-D image. Currently, we are using a transgenic mouse model engineered with a ubiquitously expressed bioluminescence/fluorescence tagged heat sensitive molecule (heat shock protein 70), however as with all models, there are limitations. From preliminary studies within our laboratory, this transgenic model has a narrow range in terms of temperature response. This transgenic model may not detect exposures generating a time/temperature profile that is less than 4 minutes of Cumulative Exposure Minutes at 43°C (CEM43). Additionally, this transgenic model will not accurately represent harsher exposures that may result in cellular damage and or cellular death, thus there is a need to develop temperature sensitive dyes/probes that can accurately report a wide range of time/temperatures histories.
We are currently seeking a post-doctoral researcher to investigate and develop different light emitting molecules capable of “non-invasively” reporting RF energy deposition in vivo within specific tissues. The ideal candidate will have 1) Ph.D. in Biophysics/Physics, 2) A strong background in fluorescence/time resolved fluorescence spectroscopy techniques, 3) Both cellular and animal handling work, 4) Experience using either the PerkinElmer IVIS SpectrumCT or systems similar to it, and 4) Background in TIRF and FLIM microscopy.
small animal imaging; radiofrequency dosimetry; bioluminescence; heat shock protein 70; TIRF microscopy; FLIM