Due to overlap with the Uniformed Services University of the Health Sciences (USUHS) in missions, scientific interests, expertise, and instrumental requirements, it was determined to be mutually beneficial to establish a joint USUHS/NIST EPR project, located at the NIST, to facilitate collaboration between the institutions. This collaboration will serve to bring together the USUHS expertise in radiation physics, small small-field dosimetry, and military-specific biodosimetry requirements with the NIST expertise in alanine dosimetry, biodosimetry and dose assessment, and spectroscopic analysis.
Developments in radiotherapy have significantly increased the use of small fields in stereotactic procedures and IMRT fields composed of small fields. Ionization chambers are not always suitable where situations of high dose gradients, time-dose variance, and non-uniform beam distributions are encountered. Volume averaging and lack of electronic equilibrium complicate the use of ionization chambers for the dosimetry of small photon beams. An international protocol was under development by the IAEA and the AAPM to address the difficult problems of small-field dosimetry in radiation therapy (e.g., Gamma Knife, IMRT, Cyber Knife, TomoTherapy). One promising path from national standards in large reference fields is the use of alanine/EPR dosimetry. The project was being conducted on multiple levels in parallel:
The collaboration served as a state-of-the-art EPR research center for the study of radiation dosimetry, radiation accident dose assessment and mapping, and the effects of ionizing radiation on various materials, in order to improve scientific understanding of radiation therapy dose distributions, radiation accident triage procedures, and radiosensitive materials. At the center of the effort is a state-of-the-art USUHS EPR spectrometer that will be used to establish a protocol for a new prototype alanine dosimeter that is better suited for small-field dosimetry. The challenge was to balance the sensitivity demands of the biodose realm and the smaller mass dosimeter with the ultimate goal to develop a calibration service that will provide traceability to national standards.