Postmortem volumetric CT data analysis of pulmonary air/gas content with regard to the cause of death for investigating terminal respiratory function in forensic autopsy

Postmortem CT (PMCT) is useful to investigate air/gas distribution and content in body cavities and viscera. The present study investigated the procedure to estimate total lung air/gas content and aeration ratio as possible indices of terminal respiratory function, using three-dimensional (3-D) PMCT data analysis of forensic autopsy cases without putrefactive gas formation (within 3 days postmortem, n = 75), and analyzed the volumetric data with regard to the cause of death. When 3-D bilateral lung images were reconstructed using an image analyzer, combined lung volume was larger in drowning (n = 12) than in alcohol/sedative-hypnotic intoxication (n = 8) and sudden cardiac death (SCD; n = 10), and intermediate in other cases, including mechanical asphyxiation (n = 12), fire fatalities due to burns (n = 6) and carbon monoxide intoxication (n = 7), fatal methamphetamine abuse (n = 7), hyperthermia (heatstroke; n = 6) and fatal hypothermia (cold exposure; n = 7). Air/gas content of the lung as detected using HU interval between −2000 and −400 ('effective' lung aeration areas) and between −2000 and −191 (total lung aeration areas) as well as the ratios to total lung volume ('effective' and total lung aeration ratios, respectively) was higher in mechanical asphyxiation, drowning, fatal burns and hypothermia (cold exposure) than in SCD, and was intermediate in other cases. 'Effective' and total lung aeration ratios may be useful for comparisons between specific causes of death to discriminate between hypothermia (cold exposure) and drug intoxication, and between SCD and other causes of death, respectively. These findings provide interesting insights into potential efficacy of PMCT data analyses of lung volume and CT density as well as lung air/gas content and aeration ratio with regard to the cause of death, as possible indicators of terminal respiratory function, as part of virtual autopsy of the viscera in situ.