The Effect of Modified Metal Artifact Suppression Method for Proton Planning
C Lin1*, T Lee2, (1) Dept. of Radiation Oncology, Wayne State University School of Medicine ,Detroit, MI, (2) McLaren Proton Therapy Center, Flint, MISU-E-J-170 Sunday 3:00PM - 6:00PM Room: Exhibit Hall
Purpose: The presence of high atomic number (high-Z) materials in CT images may create significant artifacts, called metal artifacts, which are accompanied by bright and dark shadows and streaks on CT images. The impact of incorrect CT numbers caused by metal artifacts may lead to inaccurate dose distribution in treatment planning system, especially for proton therapy. The goal of this study is to reduce the metal artifacts using modified metal artifact suppression method (MMAS) for gold fiducial markers and discover the differences of dose distribution with and without it.
Methods: CT images of water phantom with gold fiducial markers were used. First, the metal artifact suppression method was used to reduce the streak artifacts. The metal parts were properly extracted by thresholding and preserved. Using smoothing and polynomial interpolation methods to reduce artifacts around metal object. Then, the treatment plans with and without MMAS CT images for proton therapy were compared using dose distributions, conformity index and homogeneity index.
Results: Comparisons of the plans with CT images with and without MMAS show significant changes in dose around gold fiducial markers. These errors of CT numbers caused by metal artifacts appear underdosage or overdosage to the tumor and surrounding normal tissues shown on proton treatment plans.
Conclusion: This work indicates the importance of reduction of metal artifacts for proton therapy planning. Underestimation or overestimation to tumor dose and / or critical organs would impact the treatment outcome.