In vivo EPR dosimetry to quantify exposures to clinically significant doses of ionising radiation

Abstract

As a result of terrorism, accident or war, populations potentially can be exposed to doses of ionising radiation that could cause direct clinical effects within days or weeks. There is a critical need to determine the magnitude of the exposure to individuals so that those with significant risk can have appropriate procedures initiated immediately, while those without a significant probability of acute effects can be reassured and removed from the need for further consideration in the medical/emergency system. It is extremely unlikely that adequate dosemeters will be worn by the potential victims, and it also will be unlikely that prompt and accurate dose reconstruction at the level of individuals will be possible. Therefore, there is a critical need for a method to measure the dose from radiation-induced effects that occur within the individual. In vivo EPR measurements of radiation-induced changes in the enamel of teeth is a method, perhaps the only such method, which can differentiate among doses sufficiently to classify individuals into categories for treatment with sufficient accuracy to facilitate decisions on medical treatment. In its current state, the in vivo EPR dosemeter can provide estimates of absorbed dose of +/- 0.5 Gy in the range from 1 to >10 Gy. The lower limit and the precision are expected to improve, with improvements in the resonator and the algorithm for acquiring and calculating the dose. In its current state of development, the method is already sufficient for decision-making action for individuals with regard to acute effects from exposure to ionising radiation for most applications related to terrorism, accidents or nuclear warfare.

EPR dosimetry with tooth enamel: A review

“…Resonators of various designs have been proposed and developed (Ikeya and Ishii, 1989;Ikeya, 1993;Yamanaka et al 1993;Miyake et al, 2000;Zdravkova et al, 2002aZdravkova et al, , 2002bZdravkova et al, , 2003aZdravkova et al, , 2003bSalikhov et al, 2003;Iwasaki et al, 2005aIwasaki et al, , 2005bSwartz et al 2005;Zdravkova et al, 2005;Swartz et al, 2006). The spectrometers for in vivo measurements fall in two categories: those using a conventional magnet (which makes it necessary for the persons to be screened to visit the laboratory hosting the spectrometer), and those using flat magnets (which are sufficiently lightweight to be transported to the site of a radiological event).…”

Experimental procedures for sensitive and reproducible in situ EPR tooth dosimetry

“…In vivo EPR dosimetry is currently performed using the whole-body clinical EPR spectrometer at the Dartmouth EPR Center (Salikhov, et al, 2005, Swartz, et al, 2006, Swartz, et al, 2004. This continuous wave (CW) spectrometer operates at an L-Band frequency (1.2 GHz) and the main magnetic field is produced by a 420 G permanent magnet with 50 cm pole separation.…”

“…Detailed descriptions of this clinical spectrometer are given in the published reports (Salikhov, et al, 2005, Swartz, et al, 2004 and specific modifications to the instrument for tooth dosimetry are given here. Descriptions of another dedicated transportable spectrometer for tooth dosimetry have also been published (Swartz, et al, 2006.…”

“…These combined considerations call for the development of a non-invasive means to perform EPR dosimetry. This development is underway at Dartmouth Medical School (Iwasaki, et al, 2005a, Iwasaki, et al, 2005b, Salikhov, et al, 2005, Swartz, et al, 2006, Swartz, et al, 2004 in normal volunteers with irradiated teeth placed in their mouths and initial measurements with patients who have undergone radiation therapy have begun.…”

Technology Assessment and Roadmap for the Emergency Radiation Dose Assessment Program

“…Unfortunately, these early efforts resulted in microwave burns to volunteers. Although progress is being made in this regard, most recently reported data indicate that applications to human teeth Department of Homeland Security fâÑÑÉÜà|Çz \ÇyÉÜÅtà|ÉÇ 21 are still at the ex vivo stage, although the instrumentation is suitable for in vivo applications with research animals (Miyake et al, 2000;Swartz et al, 2004aSwartz et al, , 2004b.…”