Speaker
Mr
Johann Wanek
(University of Zurich, Centre of Evolutionary Medicine, Institute of Anatomy)
Description
Johann Wanek 1,2, R. Speller 2, G. Royle 2, F. Rühli 1
1: University of Zürich, Centre for Evolutionary Medicine, Institute of Anatomy, Switzerland
2: University College London, Dept of Medical Physics and Bioengineering, United Kingdom
Human tissue undergoes dramatic physicochemical changes as well as morphological alterations during the mummification process such as decreased cell volume and spacing. The exposure of ancient remains to radiation undergoing e.g. computed tomography imaging, is often accompanied by uncertainties regarding damage to ancient DNA in the ancient tissue. Consequently, anthropologists and forensic scientists are highly interested to know the probability of DNA destruction due to X-ray imaging.
Up to the present, there have been no attempts to quantify the contribution of the direct effects of sparsely ionizing radiation on desiccated cells embedded in different phantom tissues. The aim of our studies is to investigate the impact of geometry and molecular weight variations on the radiation sensitivity of cells following mummification. A computed tomography model shall be presented for the irradiation of cell nuclei distributed by self-avoiding random walks in 3D (SAW).
The results were calculated for phantom nuclei embedded in a cylinder composed of normal tissue phantom (NT) representing wet muscle tissue, dry muscle tissue (DT) representing dehydrated muscle tissue phantom or cortical bone (CB) phantom. Using Geant4 low energy extension, computed tomography (CT) scans were simulated in the energy range from 20 to 120 keV at a photon fluence of 1.1x1010 photons/cm2 and a sample rotation of 10 deg/step. A cluster of 81 ellipsoids with a dimension of 6x6x10 μm or 4x4x6 μm were placed at the isocenter of the CT model. The absorbed energy and the number of unaffected cells were calculated from protein phantoms.
This study clearly showed that the number of unaffected cells increased from 37 to 69 % by changing the surrounding tissue phantom from NT to DT because of the reduced cell volume and molecular weight. These results are in close agreement with Hutchinson's observations that the radiation sensitivity of dry biological molecules can be estimated by their molecular weight.
Reference:
Hutchinson, F. Radiation inactivation of molecules in cells. The American Naturalist, Vol. 94, No. 874 (Jan.-Feb., 1960), pp. 59-70
Primary author
Mr
Johann Wanek
(University of Zurich, Centre of Evolutionary Medicine, Institute of Anatomy)
