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Radiat Environ Biophys (2013) 52:397410 DOI 10.1007/s00411-013-0471-z
ORIGINAL PAPER
Direct action of radiation on mummied cells: modeling of computed tomography by Monte Carlo algorithms
Johann Wanek Robert Speller Frank Jakobus Rhli
Received: 10 December 2012 / Accepted: 14 April 2013 / Published online: 25 April 2013 Springer-Verlag Berlin Heidelberg 2013
Abstract X-ray imaging is a nondestructive and preferred method in paleopathology to reconstruct the history of ancient diseases. Sophisticated imaging technologies such as computed tomography (CT) have become common for the investigation of skeletal disorders in human remains. Researchers have investigated the impact of ionizing radiation on living cells, but never on ancient cells in dry tissue. The effects of CT exposure on ancient cells have not been examined in the past and may be important for subsequent genetic analysis. To remedy this shortcoming, we developed different Monte Carlo models to simulate X-ray irradiation on ancient cells. Effects of mummication were considered by using two sizes of cells and three different phantom tissues, which enclosed the investigated cell cluster. This cluster was positioned at the isocenter of a CT scanner model, where the cell hit probabilities P(0,1,, n) were calculated according to the Poisson distribution. To study the impact of the dominant physics process, CT scans for X-ray spectra of 80 and 120 kVp were simulated. Comparison between normal and dry tissue phantoms revealed that the probability of unaffected cells increased by 21 % following cell shrinkage for 80 kVp, while for 120 kVp, a further increase of unaffected cells of 23 % was observed. Consequently, cell shrinkage caused by dehydration decreased the impact of X-ray
radiation on mummied cells signicantly. Moreover, backscattered electrons in cortical bone protected deeper-lying ancient cells from radiation damage at 80 kVp X-rays.
Keywords CT imaging Target theory Cell shrinkage
Monte Carlo simulation Ancient DNA
Introduction
What is a mummy? According to Lynnerup, mummies are human remains with preservation of soft tissue (Lynnerup 2007). Physical anthropology distinguishes between natural and articial mummies. The natural or so-called spontaneous preservation of nonbony tissue takes place postmortem, usually under dry and cold (or hot) environmental conditions. A prominent subject of such mummication is the 5,300-year-old Iceman Oetzi, found in September 1991 in the Oetztal Alps. Spontaneous mummication is characterized through the rapid desiccation...