Implementing tin-prefiltration in routine clinical CT scans of the lower extremity: impact on radiation dose.

Objectives: Several studies have demonstrated the potential of tin-prefiltration to reduce radiation dose while maintaining diagnostic image quality for musculoskeletal imaging. Still, no study has reported data on the impact of tin-prefiltration on radiation dose reduction for clinical routine scanning.

Materials and methods: Retrospective inclusion of 300 clinically indicated CT scans of the pelvis, knee, and ankle before January 2020 (without tin filter) and after December 2020 (with tin filter). For each joint, 50 examinations with tin-prefiltration and 50 examinations without tin-prefiltration were selected. Dose parameters were extracted, calculated, and compared. Subjective and quantitative parameters for image quality were assessed.

Results: The CTDI_vol, DLP, and effective dose were reduced significantly in all tin-prefiltered examinations compared to the non-tin-prefiltered examinations (p < 0.001): CTDI_vol was 65% lower in the pelvis, 73% lower in the knee, and 54% lower in the ankle. This reduced the effective dose of 61%, 71%, and 60%, respectively. In absolute numbers, the reduction of the median effective dose delivered in a single CT scan of the pelvis was - 2.29 mSv, - 0.15 mSv for the knee, and - 0.03 mSv for the ankle. No difference in diagnostic image quality, depiction of bone anatomy and soft tissues, and image artifacts was observed (p > 0.05). Subjective and objective image noise was higher in tin-prefiltered pelvis CT (p < 0.001).

Conclusion: The implementation of tin-prefiltration in clinical routine scan protocols significantly reduced the effective radiation dose for unenhanced CT scans of the lower extremities between 60 and 70%.