PET/CT에서의 고관절 삽입물에 의한 인공물과 Metal Artifact Reduction Algorithm의 유용성에 대한 고찰

The Study of Usefulness of Metal Artifact Reduction Algorithm and Artifacts Caused by Metallic Hip Prosthesis on PET/CT

Purpose : PET/CT performed CT-based attenuation correction generates the beam hardening artifact by metallic implant. The attenuation correction causes over or underestimate of the area adjacent to metallic hip prosthetic material and change of ¹⁸F-FDG uptake. Also, the image quality and the diagnosability on genitourinary disease are reduced. Therefore, this study will evaluate the usefulness of MAR (Metal Artifact Reduction) algorithm method to improve the image quality on PET/CT. Materials and Methods : PET/CT was performed by fixing hip prosthesis in SPECT/PET phantom. In PET images with and Without MAR algorithm, the Bright streak, Dark streak, Metal region and Background area that appeared on CT were confirmed, and the change of each SUV (standardized uptake value) was analyzed. Also, in 15 patients who underwent total hip arthroplasty, each MAR algorithm and Without MAR algorithm and non attenuation correction was evaluated. Results : In PET image Without MAR algorithm, SUV of Bright streak region was 0.98±0.48 g/ml; Dark streak region was 0.88±0.02 g/ml; Metal region was 0.24±0.16 g/ml, Background area was 0.91±0.18 g/ml. In SUV of PET image with MAR algorithm, Bright streak region was 0.88±0.49 g/ml, Dark streak region was 0.63±0.21 g/ml, Metal region was 0.06±0.07 g/ml, Background was 0.90±0.02 g/ml. SUV generally decreased when applying MAR algorithm. In PET image Without MAR algorithm, SUVs of Bright region were higher than those measured in the Background, and it was false positive uptake. But, in PET image with MAR algorithm, SUVs of Bright region were similar to the Background, and false positive uptake disappeared. Conclusion : MAR algorithm could reduce an increase of ¹⁸F-FDG uptake due to attenuation correction in the hip surrounding tissue. However, decrease of SUV in Dark streak region should be considered in the future. Therefore, this study propose that the diagnostic accuracy can be improved in genitourinary diseases adjacent to metallic hip prosthesis, if provided PET images with and Without MAR algorithm, and non attenuation correction images at the same time.