Evaluation of a Quantitative Method for Carpal Motion Analysis Using Clinical 3-D and 4-D CT Protocols

Area of Science:

• Medical Imaging
• Biomechanics
• Radiology

Background:

• 2D imaging of the wrist is often insufficient for diagnosing motion-related complaints.
• 3D motion imaging (4D CT) offers potential for quantifying carpal motion but faces accuracy limitations due to artifacts.
• Systematic investigation into the accuracy and precision of 4D CT for carpal motion analysis is lacking.

Purpose of the Study:

• To introduce and evaluate a semi-automatic segmentation- and registration-based method for 3D carpal motion analysis.
• To systematically investigate the accuracy and precision of this 3D carpal motion analysis method.
• To determine the influence of motion and scan parameters on the accuracy and precision of 4D CT carpal motion analysis.

Main Methods:

• Developed and validated a semi-automatic segmentation and registration method for 3D carpal motion analysis.
• Utilized a wrist phantom to assess accuracy and precision under varying conditions.
• Investigated the impact of angular velocity, radiation dose, gantry revolution angle, and scanner type on positioning errors.

Main Results:

• Standstill positioning error was minimal (≤ 0.23 mm, ≤ 0.78°).
• Partial gantry revolution for 3D reconstruction introduced image deformation and increased positioning error (approx. 0.8 mm), exacerbated by reduced dose and higher angular velocity.
• Errors increased significantly when phantom rotation opposed gantry rotation, likely due to apparent velocity increase.

Conclusions:

• Slow carpal motion analysis using 4D CT is feasible with standard CT scanners.
• Partial gantry revolution for 3D reconstruction can decrease the accuracy of carpal motion analysis due to image deformation.
• Understanding positioning errors in 4D CT is crucial for accurate wrist injury assessment, distinguishing true motion from methodological artifacts.