Historically, biodosimetry studies
focused exclusively on external whole-body photon irradiation.
A main theme of our center is to assess the significance of the
variety of other radiation scenarios that are likely to occur,
using all endpoints under study. These scenarios are:
How will the results of the biodosimetric
assays change with prolonged exposure time, over periods up to
at least 24 hours, compared with acute exposure?
order to enable low dose-rate studies, we have modified our X-RAD
320 x-ray irradiator to provide essentially the same spectrum
of X rays at dose rates ranging from 4 Gy/day to 1 Gy/min. We
have designed and built a custom incubator (Figure) to allow prolonged
exposure of blood samples under physiological conditions. We have
also designed and built a custom mouse housing unit and installed
a cooling and air exchange system within the x-ray chamber, to
maintain appropriate conditions for long term exposure of mice.
We currently plan to extend the range of dose rates available
for our studies, both to very high dose-rates and to much more
protracted low dose rates.
The direct radiation component of an
Improvised Nuclear Device (IND) exposure will be at much higher
dose rates than the ~1 Gy/min rates that are typically available
from conventional irradiators. To approach a more realistic dose
rate for this scenario, we will build a high dose rate (up to
120 Gy / min) mouse irradiation system based on a radiotherapy
At the other end of the spectrum, we plan to extend our studies
of low dose rate effects using a variable-dose-rate external 137Cs
irradiator (VADER), which we have designed to be able to simulate
the changing dose rates experienced when 137Cs has been internally
deposited and is slowly excreted from the body. We will also be
able to use this device to provide a constant low dose rate to
mice housed within the irradiator for weeks.
we have long had facilities to provide monoenergetic neutron irradiations,
both in vitro and for small animals. We have now developed
and tested a unique facility to simulate the neutron spectra at
relevant distances (e.g. 1.5 km) from the epicenter of a nuclear
detonation. This new facility has been and continues to be used
by all three projects. As expected an increased RBE has been seen
over photon irradiations. In addition, we have an x-ray machine
located in the next room to the neutron irradiation room, which
allows x-ray irradiations to be performed immediately before or
after a neutron irradiation, for simulating combined exposures,
which is the current focus of these studies.
A major component of the absorbed dose
from a Radiological Dispersal Device (RDD) or nuclear detonation
will be from incorporation of radionuclides into the body, either
by inhalation of radioactive aerosols or ingestion of contaminated
food. In order to study the impact of internal emitters on our
biodosimetric methods, we have partnered with the Lovelace
Respiratory Research Institute. Two prior studies were concluded
on the effects of internalized
• Cs-137: a typical gamma emitter
that provides a uniform total body exposure with an exponentially
decaying dose rate.
• Sr-90: a beta emitter that
is accumulated in the bone providing a total body irradiation
with a constant dose rate.
Some data from these studies is presented
in the results section of Projects
Currently planned studies will expand
on the earlier 137Cs study, with different injection amounts being
given to the animals to further explore the effects of dose and
dose rate. Later work planned with the VADER will allow
us to follow up further on these studies including additional
dose-rates and endpoints.