Date Published: February 6, 2018
Publisher: Public Library of Science
Author(s): Angela Kinoshita, Oswaldo Baffa, Sérgio Mascarenhas, Sergey Sholom.
Explosion of the bombs in Hiroshima and Nagasaki corresponds to the only historical moment when atomic bombs were used against civilians. This event triggered countless investigations into the effects and dosimetry of ionizing radiation. However, none of the investigations has used the victims’ bones as dosimeter. Here, we assess samples of bones obtained from fatal victims of the explosion by Electron Spin Resonance (ESR). In 1973, one of the authors of the present study (SM) traveled to Japan and conducted a preliminary experiment on the victims’ bone samples. The idea was to use the paramagnetism induced in bone after irradiation to measure the radiation dose. Technological advances involved in the construction of spectrometers, better knowledge of the paramagnetic center, and improvement in signal processing techniques have allowed us to resume the investigation. We obtained a reconstructed dose of 9.46 ± 3.4 Gy from the jawbone, which was compatible with the dose distribution in different locations as measured in non-biological materials such as wall bricks and roof tiles.
Electron Spin Resonance spectroscopy allows the use of constituents of the human body as dosimeter. It has been widely studied and explored due to its application in retrospective dosimetry in cases of accidental exposure to radiation. This is a subject of great relevance if we consider that advanced medical treatments, like the use of stem cells and transplantation, can be offered to the victims of such exposure depending on the radiation dose they received [1–3].
Fig 2 shows the initial spectrum obtained after 400 scans of the mandible (black line) and the spectrum of the simulated isotropic radical at g = 2.0045 (red line). The signal obtained after subtraction (blue line) fitted the signal of axial CO2-, recognized as a radical induced by incidence of ionizing radiation on hydroxyapatite (Hap). After irradiation, the signal intensified. Therefore, there was no saturation, as seen from the increasing signal-to-noise ratio with increasing deposited dose.
ESR dosimetry in bones is not novel. Many papers have dealt with reconstruction of the radiation dose received during radiological accidents. However, the samples analyzed in this work have important historical value because they belong to fatal victims of the first and only moment in history when nuclear weapons were used against civilian targets. This work demonstrates how technological advances, such as higher sensitivity of spectrometers and use of software to simulate ESR spectra, can contribute to the conduction and finalization of investigations that did not advance to final conclusions in the past.