Whole body imaging in the diagnosis of blunt trauma, ionizing radiation hazards and residual risk

Topogram-based automated selection of the tube potential and current in thoraco-abdominal trauma CT - a comparison to fixed kV with mAs modulation alone

OBJECTIVE

To investigate the impact of automated attenuation-based tube potential selection on image quality and exposure parameters in polytrauma patients undergoing contrast-enhanced thoraco-abdominal CT.

METHODS

One hundred patients were examined on a 16-slice device at 120 kV with 190 ref.mAs and automated mA modulation only. Another 100 patients underwent 128-slice CT with automated mA modulation and topogram-based automated tube potential selection (autokV) at 100, 120 or 140 kV. Volume CT dose index (CTDI(vol)), dose-length product (DLP), body diameters, noise, signal-to-noise ratio (SNR) and subjective image quality were compared.

RESULTS

In the autokV group, 100 kV was automatically selected in 82 patients, 120 kV in 12 patients and 140 kV in 6 patients. Patient diameters increased with higher kV settings. The median CTDI(vol) (8.3 vs. 12.4 mGy; -33%) and DLP (594 vs. 909 mGy cm; -35%) in the entire autokV group were significantly lower than in the group with fixed 120 kV (p < 0.05 for both). Image quality remained at a constantly high level at any selected kV level.

CONCLUSION

Topogram-based automated selection of the tube potential allows for significant dose savings in thoraco-abdominal trauma CT while image quality remains at a constantly high level.

KEY POINTS

• Automated kV selection in thoraco-abdominal trauma CT results in significant dose savings • Most patients benefit from a 100-kV protocol with relevant DLP reduction • Constantly good image quality is ensured • Image quality benefits from higher kV when arms are positioned downward.