Evidence-based recommendations for musculoskeletal kinematic 4D-CT studies using wide area-detector scanners: a phantom study with cadaveric correlation.

PROPOSE

To establish evidence-based recommendations for musculoskeletal kinematic 4D-CT on wide area-detector CT.

MATERIALS AND METHODS

In order to assess factors influencing image quality in kinematic CT studies, a phantom consisting of a polymethylmethacrylate rotating disk with round wells of different sizes was imaged with various acquisition protocols. Cadaveric acquisitions were performed on the ankle joint during motion in two different axes and at different speeds to allow validation of phantom data. Images were acquired with a 320 detector-row CT scanner and were evaluated by two readers.

RESULTS

Motion artefacts were significantly correlated with various parameters (movement axis, distance to centre, rotation speed and volume acquisition speed) (p < 0.0001). The relation between motion artefacts and distance to motion fulcrum was exponential (R 0.99). Half reconstruction led to a 23 % increase in image noise and a 40 % decrease in motion artefacts. Cadaveric acquisitions confirmed phantom data. Based on these findings, high tube rotation speed and half reconstruction are recommended for kinematic CT. The axis of motion significantly influences image artefacts and should be considered in patient training and evaluation of acquisition protocol suitability.

CONCLUSION

This study provides evidence-based recommendations for musculoskeletal kinematic 4D-CT.

KEY POINTS

• Motion artefacts can hamper the quality and interpretation of dynamic joint studies • The recommendations presented here help increase image quality • Patient training and preparation can be improved • The artefact-free distance concept helps protocol adaptation and comparison.