Regional measurements of radio-density in the right atrium do not show differences between salt-water or fresh-water drowned or control decedents

Purpose: To determine whether the use of post-mortem computed tomography (PMCT) measurements of blood radio-density within the right atrium could differentiate decedents grouped according to cause of death as controls, fresh-water or salt-water drowning. Methods: PMCT images from drowning cases comprising fresh-water (n = 34) and salt-water (n = 30) incidents and also controls (n = 48) were selected from a forensic database. Four regions of interest (ROIs) were placed within the right atrium of the heart using a standardised procedure that accounted for sedimentation effects. Statistical analysis was undertaken using a two-way random effect inter-class correlation (ICC) test set for absolute agreement and then a repeated measures ANOVA test. Results: ICC tests demonstrated very good agreement for the readings for all ROIs (ICC ≥ 0.90). A statistically significant sedimentation effect was observed across the anterior middle and posterior regions of the right atrium (F(2,218) = 212, p <.001). There was no significant effect of Group (F(2,109) = 0.481, p =.620), nor was there a significant interaction between group and Region (F(4,218) = 2.09, p =.083). Conclusions: Aspiration of fluid while drowning may cause changes in blood concentration. Blood concentration is measured using radio-density on PMCT images. PMCT radio-density data extracted from regional ROIs demonstrates the presence of the sedimentation effect but is not supportive of classification of drowning. There was good agreement between readers in the performance of this task.