41Ca in Tooth Enamel. Part II: A Means for Retrospective Biological Neutron Dosimetry in Atomic Bomb Survivors

41Ca is produced mainly by absorption of low-energy neutrons on stable 40Ca. We used accelerator mass spectrometry (AMS) to measure 41Ca in enamel of 16 teeth from 13 atomic bomb survivors who were exposed to the bomb within 1.2 km from the hypocenter in Hiroshima. In our accompanying paper (Wallner et al., Radiat. Res. 174, 000–000, 2010), we reported that the background-corrected 41Ca/Ca ratio decreased from 19.5 3 10215 to 2.8 3 10215 with increasing distance from the hypocenter. Here we show that the measured ratios are in good correlation with c-ray doses assessed by electron paramagnetic resonance (EPR) in the same enamel samples, and agree well with calculated ratios based on either the current Dosimetry System 2002 (DS02) or more customized dose estimates where the regression slope as obtained from an errors-in-variables linear model was about 0.85. The calculated DS02 neutron dos