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Updated: May 11, 2026

Protocol for the Evaluation of MRI Artifacts Caused by Metal Implants to Assess the Suitability of Implants and the Vulnerability of Pulse Sequences
Published on: May 17, 2018
Changes realized from extended bit-depth and metal artifact reduction in CT
C Glide-Hurst1, D Chen, H Zhong
1Department of Radiation Oncology, Henry Ford Health Systems, Detroit, Michigan 48202, USA. churst2@hfhs.org
Enhanced 16-bit computed tomography (CT) imaging with metal artifact reduction (MAR) improves image quality and dose calculation accuracy for patients with metal implants. This approach offers a more precise dosimetric method and better visualization by reducing CT artifacts.
Area of Science:
- Medical Physics
- Radiological Imaging
- Radiation Oncology
Background:
- Metal artifacts in computed tomography (CT) degrade image quality and introduce errors in dose calculations.
- High-Z materials, common in medical implants, are primary sources of these artifacts.
- Accurate dose calculation is critical for effective radiation therapy planning.
Purpose of the Study:
- To evaluate the combined benefits of metal artifact reduction (MAR) and enhanced 16-bit CT depth for improving image quality and dosimetric accuracy.
- To quantify the impact of 16-bit reconstruction compared to standard 12-bit reconstruction in the presence of metal artifacts.
- To assess the potential for improved treatment planning using MAR-corrected 16-bit CT data.
Main Methods:
- Development of extended CT to electron density (CT-ED) curves for 12- and 16-bit reconstructions.
- Application of MAR to sinogram data on a Brilliance BigBore CT scanner.
- Monte Carlo simulations (MC-SIM) and phantom studies with titanium, stainless steel, and Cerrobend inserts.
- Dosimetric verification using Gafchromic film and Anisotropic Analytic Algorithm (AAA) calculations.
- Analysis of patient data from cases with various metal implants.
Main Results:
- 16-bit CT reconstructions showed significantly higher CT numbers for metal implants compared to 12-bit, which saturated.
- Monte Carlo simulations indicated a ~6.4% greater dose with 16-bit data downstream of metal artifacts.
- Film dosimetry and gamma analysis demonstrated superior agreement between 16-bit calculated doses and film measurements compared to 12-bit.
- Patient data revealed dose discrepancies of up to 17%-20% for 12-bit reconstructions, particularly in cases with direct beam traversal of metal.
Conclusions:
- Implementation of 16-bit MAR-corrected images is recommended for treatment planning.
- This approach offers a more accurate dosimetric strategy.
- Enhanced visualization through artifact suppression is a key benefit for clinical application.
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