Radiation Footprint Research Articles

Footprint and height corrections for UAV-borne gamma-ray spectrometry studies

Advancements in the development of gamma-ray spectrometers (GRS) have led to small and lightweight spectrometers that can be used under unmanned aerial vehicles (UAVs). Airborne GRS measurements are used to determine radionuclide concentrations in the ground, among which the natural occurring radionuclides 40K, 238U, and 232Th. For successful applications of these GRS sensors, it is important that absolute values of concentrations can be measured. To extract these absolute radionuclide concentrations, airborne gamma-ray data has to be corrected for measurement height. However, the current analysis models are only valid for the height range of 50–250 m. The purpose of this study is to develop a procedure that correctly predicts the true radionuclide concentration in the ground when measuring in the UAV operating range of 0–40 m. An analytical model is developed to predict the radiation footprint as a function of height. This model is used as a tool to properly determine a source-detector geometry to be used in Monte-Carlo simulations of detector response at various elevations between 0 and 40 m. The analytical model predicts that the smallest achievable footprint at 10 m height lies between 22 and 91 m and between 40 and 140 m at 20 m height. By using Monte-Carlo simulations it is shown that the analytical model correctly predicts the reduction in full energy peak gamma-rays, but does not predict the Compton continuum of a spectrum as a function of height. Therefore, Monte-Carlo simulations should be used to predict the shape and intensity of gamma-ray spectra as a function of height. A finite set of Monte-Carlo simulations at intervals of 5 m were used for the analysis of GRS measurements at heights up to 35 m. The resulting radionuclide concentrations at every height agree with the radionuclide concentration measured on the ground.

The radiation footprint on the pediatric trauma patient

BackgroundThe actual baseline of radiation exposure used in evaluating pediatric trauma is not known and has relied on estimates in the literature that may not reflect clinical reality. Our objectives were to determine the baseline amount of radiation delivered in a pediatric trauma evaluation and correlate radiation exposure with trauma activation status to identify the cohort most at risk.MethodsWe retrospectively evaluated trauma patients (N = 1050) at an independent Level I children’s hospital for each level of trauma activation (consults, alerts, stats) from June 2010 to January 2011. Those patients with full dosimetry (N = 215) were analyzed for demographics, mechanism of injury, Injury Severity Score, imaging modalities, and total effective radiation dosages during the full trauma assessment from the time of injury to discharge.ResultsDemographics included gender (143 males, 72 females) and average age (5.5 years [range < 1–16]). The most radiation was conferred from CTs and greatest in trauma stats, followed by alerts, then consults (p < 0.001 for stat and alert doses compared to consults). Repeated imaging was common: 35% of stats had 2–3 CTs and 40% had 4–10 CTs (range 0–10 CTs). The average non-accidental trauma consult utilized four times as many CTs as the average consult (p = 0.002). Most outside hospital CTs (66%) delivered more radiation: 50.0% were at least double the standard pediatric dosage.ConclusionsThis study is the first to identify the actual baseline of radiation exposure for one trauma evaluation and correlate radiation exposure with trauma activation status. Factors associated with highest radiation include stat activations, suspected non-accidental traumas (NAT), and outside hospital system imaging.

The radiation footprint on the pediatric trauma patient

The radiation footprint on the pediatric trauma patient

Intensity-Modulated Advanced X-Ray Source (IMAXS) for Homeland Security Applications

X-ray cargo inspection systems for the detection and verification of threats and contraband must address competing performance requirements. In addition to high X-ray energy, high X-ray intensity is needed to penetrate dense cargo, while low intensity is desirable to minimize the radiation footprint, i.e. the size of the controlled area, required shielding and the dose to personnel. We report here on a collaborative effort between HESCO/PTSE Inc., Schonberg Research Corporation and Rapiscan Laboratories, Inc. to design an Intensity-Modulated Advanced X-ray Source (IMAXS) that allows such cargo inspection systems to achieve up to two inches greater penetration capability, while on average retaining the same radiation footprint as present fixed-intensity sources. Alternatively, the new design can be used to obtain the same penetration capability as with conventional sources, but reducing the average radiation footprint by about a factor of three. The key idea is to anticipate the needed intensity for each X-ray pulse by evaluating signal strength in the cargo inspection system detector array for the previous pulse. Requirements therefore include an X-ray source capable of changing intensity from one pulse to the next by electronic signal, as well as electronics inside the cargo inspection system detector array determining the required source intensity for the next pulse. The feasibility of pulse-to-pulse intensity modulation of both S-band (2998 MHz) and X-band (9303 MHz) linac sources has been demonstrated.

Electronic protection and routing optimization of MANETs operating in an electronic warfare environment

Domination of the electromagnetic spectrum is a crucial component of the 21st century warfare. In the harsh electromagnetic environment of the modern battlefield, it is of the utmost importance to deny the opposing force the opportunity to attack or exploit the detection/interception of friendly communications assets through the deployment of electronic protection (EP) measures in order to attain low probability of detection (LPD), low probability of interception (LPI) and anti-jam (A/J). Given that directional antennas are a suitable means to achieve both extended range and LPD/LPI, this paper proposes mechanisms to optimize the trade-off between these capabilities, minimizing the number of hops and end-to-end delay when routing packets in a multi-hop ad-hoc network, while taking into account stealth requirements. The novel scheme is based on a variant of Fisheye State Routing, coupled with a power control algorithm to guarantee a LPD/LPI beyond the zone covered by the omni-directional radiation footprint of the network. The performance of the proposed scheme is evaluated through computer simulation.