Radiation dose reduction through short scan protocols and arms-out positioning in clavicular CT for forensic age estimation.

OBJECTIVE

To assess the effect of scan length, partial humeral head inclusion, and body mass index (BMI) on radiation dose of CTs of the medial clavicular epiphysis (MCE) performed with elevated arms (arms-up).

METHODS

Ninety consecutive MCE CTs acquired in an arms-up position for forensic age estimation were retrospectively analysed. Scans were grouped by scan length (short: ≤4 cm; long: >4 cm, rounded to the nearest cm) and by arm position (arms-out: humeral heads excluded; arms-in: humeral heads partially included). Dose-relevant parameters (effective tube current, volume CT dose index, CT dose length product, and effective dose) were compared. Adjusted geometric mean ratios (aGMRs) were calculated to quantify the association between radiation doses and scan length, arm inclusion, and BMI.

RESULTS

Population: 88 males, 2 females; median (IQR) weight 62.0 kg (57.5-67.9), height 172 cm (168-178), BMI 21.1 kg/m² (19.5-22.4). Effective dose was lowest in short scans with arms-out (0.38 mSv, 0.32-0.43), highest in long scans with arms-in (0.49 mSv, 0.39-0.62), and equal in short scans with arms-in and long scans with arms-out (0.41 mSv, 0.36-0.46 and 0.34-0.46, respectively). Each additional centimetre of scan length increased dose by 8.3% (aGMR 1.083, 95% CI 1.036-1.132), each centimetre of humeral head inclusion by 6.8% (1.068, 1.046-1.090), and each BMI unit by 4.1% (1.041, 1.024-1.058).

CONCLUSIONS

Effective dose was 22% lower in short scans with arms-out than in long scans with arms-in. Careful patient positioning and precise scan length planning substantially reduce radiation exposure in MCE CT for age estimation.