Unveiling the diagnostic accuracy of PMCT: Detection of pneumonia considering postmortem changes and time intervals

Purpose: Postmortem CT (PMCT) faces challenges in assessing lung parenchyma due to images being acquired in expiratory state, leading to varying severity of pulmonary edema redistribution with gravity-dependent attenuation ranging from ground glass to full opacification. This retrospective study assessed the effect of gravity-dependent attenuation and the postmortem time interval (PTI) on the diagnostic accuracy of PMCT for detecting acute pneumonia. Materials and methods: Deceased patients who underwent PMCT and autopsy were included. Consensus evaluations by two radiologists and two pathologists re-examined images and histological samples of separate lung lobes. Scores were assigned for radiological and histological findings, including the presence of acute pneumonia, gravity-dependent attenuation severity, and pulmonary edema. PTI was calculated and correlated with gravity-dependent attenuation severity. Crosstabs were created to calculate diagnostic parameters. Results: Fifty-seven patients were included, with four excluded and 44 fully opacified lung lobes. 168 lung lobes remained for analysis. The average PTI was 22 hours and 47 min. A weak correlation was observed between PTI and gravity-dependent attenuation severity (tb = 0.125, p = 0.016). Acute pneumonia prevalence was 24,4 %, with sensitivity and specificity of PMCT for all lung lobes at 31,71 % and 85,83 %, respectively. PMCT performed better in subgroups with none or slight gravity-dependent attenuation and in patients scanned within 16 hours after death. Conclusion: Interpretation of lung parenchyma with PMCT is challenging. Statistical power was limited due to a limited sample size. PMCT is more suited for excluding acute pneumonia than detecting its presence. Prolonging PTI should be avoided, as increasing gravity-dependent attenuation severity over time limits PMCT sensitivity.