Technical note: derivation and evaluation of practical PMCT display window parameters for frozen brain tissue.

OBJECTIVE: Frozen cadavers are common in forensic practice. When examining frozen cadaver brains with conventional clinical CT brain windows, brain tissue exhibits a "completely black" appearance precluding assessment. This study aimed to derive and evaluate CT display window parameters for frozen brain tissue to optimize image quality and assist forensic image interpretation. METHODS: A two-phase study was conducted on 30 frozen cadavers (-20 °C, ≥ 72 h). In Phase I (n = 2), Window Level (WL) and Window Width (WW) were derived from CT values of anatomical regions on PMCT and locked. In Phase II (n = 28), parameters were applied to a held-out internal evaluation cohort. Effectiveness was evaluated using display coverage rate and subjective scores by two independent raters. RESULTS: Brain density dropped to negative HU upon freezing. The derived parameters (WL: -10 HU, WW: 110 HU) markedly improved the "completely black" appearance, achieving display coverage rates of 100% for normal brain ROIs and 54.55% for hemorrhagic ROIs, with an overall rate of 96.69%. Subjective image quality scores were significantly higher for the derived parameters (median [IQR]: 18.0 [17.0-18.0]) than for conventional clinical windows (median [IQR]: 6.5 [6.0-7.0]) for both raters (P < 0.001), with excellent inter-rater agreement (overall weighted κ = 0.981). CONCLUSION: This study derived and internally evaluated practical display window parameters (WL: -10 HU, WW: 110 HU) for frozen brain PMCT. These parameters effectively improved visualization of frozen brain anatomy and hemorrhagic lesions, providing a pragmatic post-processing display parameters for post-mortem cranial imaging evaluation of frozen cadavers in forensic PMCT practice.