CT of the medial clavicular epiphysis for forensic age estimation - raised arms position recommended.

OBJECTIVE

To compare the effect of arm positioning on radiation dose, scan length, and image noise in computed tomography (CT) scans of the medial clavicular epiphysis for forensic age estimation performed with the arms alongside the body (arms-down) versus elevated above the head (arms-up).

METHODS

Twenty consecutive CT scans were analysed, ten performed with arms-down and ten with arms-up. The scans were conducted at 120 kVp and 37 mAs reference tube current. Scan length extended from 10 mm above to 10 mm below the medial clavicular epiphysis. Dose-relevant parameters (effective CT tube current, volume CT dose index (CTDIvol), CT dose length product (DLP), and effective dose) as well as scan length and image noise were compared between arms-up and arms-down CT scans.

RESULTS

Population characteristics: 19 males, 1 female; mean weight 65.8 ± 9.2 kg; height 174.6 ± 7.8 cm; and body mass index (BMI) 21.6 ± 2.5 kg/m². Dose-relevant parameters were significantly lower with arms-up compared to arms-down (effective tube current: 80.9 ± 21.7 mAs vs. 146.0 ± 47.5 mAs, p = 0.001; CTDIvol: 5.5 ± 1.5 mGy vs. 9.9 ± 3.2 mGy, p = 0.001; DLP: 40.2 ± 13.7 mGy*cm vs. 63.8 ± 21.9 mGy*cm, p = 0.010; effective dose: 0.6 ± 0.2 mSv vs. 0.9 ± 0.3 mSv, p = 0.010). No significant differences were found in scan length, image noise, or population characteristics.

CONCLUSIONS

Removing the arms from the CT beam path reduced radiation dose by 33% without affecting scan length or image noise. Given the importance of dose optimisation in non-medical examinations of potentially minor individuals, CT scans of the medial clavicular epiphysis should be performed with arms elevated above the head.