Imaging Pearls ❯ CT Techniques and Principles, including MPR and 3D ❯ Metal Artifacts
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- Factors Affecting Metal Artifacts at Multidetector CT
- Hardware related
- Scanner parameter related - CT of the Hip Prosthesis: Appearance of Components, fixation, and Complications
Roth TD et al.
RadioGraphics 2012; 32:1089-1107 - Factors Affecting Metal Artifacts at Multidetector CT
- Hardware Related
- Composition
- Cobalt chrome based has highest photon attenuation
- Iron based (stainless steel) has high photon attenuation
- Titanium based has lower photon attenuation - Factors Affecting Metal Artifacts at Multidetector CT
- Hardware Related
- Geometry
- Shape-artifact greater with complex shapes
- Orientation-artifact greatest along the long axis in the axial plane - Factors Affecting Metal Artifacts at Multidetector CT
- Scanner Related Parameters
- Collimation-narrower collimation decreases artifacts
- Kilovolt peak-higher kVP reduces noise but lowers image contrast and increases radiation dose
- Milliampere seconds-higher mAs reduces noise but increases radiation dose - Factors Affecting Metal Artifacts at Multidetector CT
- Scanner Related Parameters (cont)
- Pitch-low pitch oversamples data, decreases artifact, and improves image quality but increases dose
- Reconstruction Algorithm-lower spatial frequency algorithms “smooth” the images and mitigate fine streaks around hardware
- Reconstruction Section Thickness-thicker sections decrease artifacts by averaging signal - OBJECTIVE: Conventional CT of the postoperative patient with metal hardware is frequently limited by beam-hardening artifacts. With the evolution of 3D CT, CT is an increasingly effective means of examining the postsurgical patient for the integrity of their hardware and the course of their healing.
CONCLUSION: Potential postsurgical complications such as nonunion, osteolysis, infection, and heterotopic ossification are all well assessed by 3D CT.
Value of 3D CT in defining skeletal complications of orthopedic hardware in the postoperative patient
Fayed LM, Patra A, Fishman EK
AJR 2009 Oct;193(4):1155-63