Metal artifact reduction for intracranial projectiles on post mortem computed tomography

Abstract

PurposeTo compare the image quality of cranial post-mortem computed tomography (CT) obtained with and without projection-based single-energy metal artifact reduction (SEMAR) in cadavers with intracranial metallic ballistic projectiles. Materials and methodsFrom January 2017 to January 2018, cadavers with ballistic projectile head wounds with metal fragments and without massive head destruction were investigated using post-mortem CT. All subjects underwent CT using a conventional iterative reconstruction (IR) and SEMAR. To evaluate the impact of metallic artifacts, the total intracranial area (TA), non-interpretable zone (NIZ), disturbed interpretation zone (DZ), and artifact total surface (ATS) were delineated. Two independent readers identified extra-axial hemorrhage (EAH) and subarachnoid hemorrhage (SAH). Autopsy reports were used as the standard of reference. ResultsEleven corpses (10 males, 1 female; mean age, 62.8±17.9 [SD] years) were evaluated. SEMAR showed a significant decrease in the ATS ratio with respect to conventional IR (72.1±26.1 [SD] % [range: 26.8-99.1] vs. 86.4±17.8 [SD] % [range: 37.2-100]; P<0.001) and NIZ/TA ratios (11.6±8.26% [range: 0.95–33.4] versus 42.5±30.5% [range: 3.86–100]; P<0.001). The interobserver reproducibility in diagnosing EAH and SAH was excellent with conventional IR (0.82) and good with SEMAR (0.75). SEMAR reduced uncertain diagnoses of EAH in 7 subjects for Reader 1 and in 6 for Reader 2, but did not influence the diagnosis of SAH for either reader. ConclusionSEMAR reduces the influence of metallic artifacts and increases the confidence with which the diagnosis of EAH can be made on post-mortem CT.