Spectrophotometric Color Measurement to Assess Temperature of Exposure in Cortical and Medullar Heated Human Bones: A Preliminary Study

Abstract

Heated-bone color changes may provide information about temperature of exposure, with interest for anthropologists and forensic experts. The aim of this study was to assess heat-induced color changes by spectrophotometry in cortical and medullar human bones heated at different temperatures and times. CIELAB (International Commission on Illumination-LAB) color parameters (L*, a*, and b*) and whiteness (WI) and yellowness (YI) indexes were obtained by spectrophotometry in the cortical and medullar zones of 36 bone sections exposed at 200, 400, 600, and 800 °C for 30 and 60 min. The accuracy of color-based temperature estimations was evaluated by Receiver Operating Characteristics (ROC) analysis. Chromaticity a* showed the best significant discrimination power with the area under the ROC curve (AUC) values ranged from 0.9 to 1.0 in cortical zones and 0.7 to 1.0 in medullar zones for all temperatures of exposures and both time of exposures. Chromaticity b*, and WI and YI indexes showed an AUC of 1.0 at 400, 600, and 800 °C for 30 and 60 min in the cortical and medullar zones. The spectrophotometric color parameters provided a highly accurate estimation of the temperature of exposure to discriminate between temperatures and exposure times in the cortical and medullar zones. Spectrophotometric bone color measurement in cortical and medullar zones can be an objective and reproducible method to estimate the temperature of exposition, and it can be considered useful for forensic and anthropological purposes.

A Tunguska sized airburst destroyed Tall el-Hammam a Middle Bronze Age city in the Jordan Valley near the Dead Sea

“…Skull is embedded in pulverized mudbrick containing numerous charcoal fragments (yellow circles) and is stained with ash commonly found in the destruction layer (blue arrow). The orange tint of the skull suggests it was exposed to temperatures > 200 °C 141 . ( b ) Rear view of the same skull in panel ‘ a ’ (blue arrow) near the second skull (purple arrow) and numerous disarticulated, fragmented human bones (orange arrows).…”

High-Resolution Phosphorescence Lifetime Imaging (PLIM) of Bones

“…A photographic image of the bones samples after the heating which feature typical heat-induced color changes [16] is shown in Figure 2a. The color ranges from black (400 • C) to brown and grey and completely white (900 • C).…”

“…The color ranges from black (400 °C) to brown and grey and completely white (900 °C). The color changes of bones as a result of temperature are well-known and caused by changes of the chemical composition of the organic components [16]. Figure 2b shows microscopic images which were derived from the pixelwise-collected photon counts during "laser on" and "laser off" times.…”

“…Figure 2b shows microscopic images which were derived from the pixelwise-collected photon counts during "laser on" and "laser off" times. The laser "on-time" images reflect the fluorescence intensity distribution (with negligible phosphorescence contributions) and the "laser-off The color changes of bones as a result of temperature are well-known and caused by changes of the chemical composition of the organic components [16]. Figure 2b shows microscopic images which were derived from the pixelwise-collected photon counts during "laser on" and "laser off" times.…”