The Common Vein

• Motion is the most common  caused by
  • patient,
  • cardiac, or
  • respiratory motion.
• Attempt at solutions
  • Cardiac motion artifacts

  • 

    web-CT-011.webp

    Axial CT images obtained at different phases of the cardiac cycle (from 0% to 80% R-R interval) show that the right coronary artery has varying degrees of motion in each of the cardiac phases. In this patient, the motion is least in the 50% and 80% phases of the R-R interval.
    Kalisz K et al  Artifacts at Cardiac CT: Physics and Solutions  RadioGraphicsVol. 36, No. 7

  • can be reduced by
    • decreasing the heart rate and variability and the
    • duration of data acquisition;
    • adjusting the placement of the data window within a cardiac cycle; (diastole
    • performing single-heartbeat scanning; and
    • using multisegment reconstruction,
    • motion-correction algorithms, and
    • electrocardiographic editing.
  • Respiratory motion artifacts can be minimized with
    • proper breath holding and
    • shortened scan duration.
  • Partial volume averaging is
    • caused by the
      • averaging of attenuation values from all tissue contained within a voxel and
    • reduced by
      • improving the spatial resolution,
      • using a higher x-ray energy, or
      • displaying images with a wider window width.
  • Beam-hardening artifacts are
    • • caused by the
        • polyenergetic nature of the x-ray beam and can be
      • reduced by using
        • x-ray filtration,
        • applying higher-energy x-rays,
        • altering patient position,
        • modifying contrast material protocols, and
        • applying certain reconstruction algorithms.
    • Metal artifacts are complex and
      • have multiple causes,
        • including x-ray scatter,
        • underpenetration, motion, and
        • attenuation values that exceed the typical dynamic range of Hounsfield units.
    • Quantum mottle or noise is
      • caused by
        • insufficient penetration of tissue and can be
      • improved by
        • increasing the tube current or peak tube potential,
        • reconstructing thicker sections,
        • increasing the rotation time,
        • using appropriate patient positioning, and
        • applying iterative reconstruction algorithms.

Links and References

Kalisz K et al  Artifacts at Cardiac CT: Physics and Solutions  RadioGraphicsVol. 36, No. 7