in vivo dosimetry by electron spin resonance spectroscopy

Health Physics Pergamon Press 1968. Vol. 15, pp. 43--47. Printed in Northern Ireland
IN VIVO DOSIMETRY BY ELECTRON SPIN RESONANCE
SPECTROSCOPY
JOHN M. BRADY*, NORMAN O. AARESTAD and HAROLD M. SWARTZ
Department of Biophysics, Division of Nuclear Medicine, Walter Reed Army Institute of
Research, Walter Reed Army Medica! Genter, Washington, D.G. 20012
(Received 13 October 1967; in revisedform 8 December 1967)
Abstract-Several tissues, especially hard tissues, showed persistent electron spin resonances
following in vivo or in vitro irradiations. The resonances had a linear relation to dose. Dose
measurements were made in teeth at less than 100 rads of 6 °Co radiation. The method
appears to be applicable for dosimetry of accidental irradiations, especially X- or gamma-ray
exposures.
INTRODUCTION
DosIMETRY of accidental irradiation incidents
is difficult unless dosimeters are exposed in the
accident. Dose calculation usually depends on
reconstruction of the exposure situation. If
the accidental exposure includes neutron radiation
the resulting activation may aid in the
determination of exposure dose; if neutrons
are not involved, the difficulty of accurate
reconstruction increases. Radiation, especially
sparsely ionizing radiation such as gammaor
X-rays, produces free radicals. Many ofthese
radiation-induced radicals may persist. < 1 > Electron
spin resonance (ESR) techniques detect
free radicals and so offer potential dosimetry
without man-made dosimeters. Long-lived
electron spin resonances have been reported in a
variety of irradiated tissues, but usually at
doses beyond those of biological interest.

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J. M. BRADY, N. O. AARESTAD and H. M. SWARTZ
potential promise and should be further
investigated.
Teeth, on the basis of the results presented
here, are good dosimeters and can be useful at
doses as low as 100 rads. They show a linear