Tin-filtered ultra-low-dose CT for lower limb torsion measurements in children and adolescents: a prospective study.

OBJECTIVE

Accurate femoral and tibial torsion measurements are essential for planning lower extremity derotation surgeries in children/adolescents. Advances in modern CT scanners may enable reliable measurements using tin filtration in addition to an ultra-low-dose CT protocol, markedly reducing radiation exposure. This study evaluates image quality, reliability, and estimated effective radiation dose of this approach.

MATERIALS AND

METHODS

Between April 2022 and December 2022, tin-filtered ultra-low-dose CTs were prospectively acquired from 52 children/adolescents using a 384-slice scanner. Two pediatric radiologists independently performed torsion measurements for all patients. Interrater agreement and image quality were assessed. Effective radiation doses of the scans were estimated.

RESULTS

The study population consisted of 52 participants (mean age, 12.7 years ± 2.0 [standard deviation]; 19 females, 33 males). All torsion measurements showed very high interrater agreement (intra-class correlation coefficient > 90% for all locations). The image quality of the vast majority of image datasets was rated as excellent. The mean total effective dose of the tin filtered ultra-low-dose protocol (including 3 spiral scans) was 0.026/0.025 mSv (boys/girls), compared to 0.184/0.215 mSv (boys/girls) of the previously published ultra-low-dose protocol without tin filtration. This represents a dose reduction of up to 88% compared to the previous protocol.

CONCLUSION

The use of tin filtration, in addition to an ultra-low-dose protocol, allows pediatric lower extremity torsion measurements to be performed with radiation doses in a lower range than a typical localizer dose, without compromising diagnostic confidence, pushing the limits of the ALARA (as low as reasonably achievable) principle.