Correction of CT artifacts and its influence on Monte Carlo dose calculations

被引:110
作者
Bazalova, Magdalena
Beaulieu, Luc
Palefsky, Steven
Verhaegen, Frank
机构
[1] McGill Univ, Montreal Gen Hosp, Dept Phys Med, Montreal, PQ H3G 1A4, Canada
[2] Univ Laval, Dept Phys Genie Phys & Opt, Ste Foy, PQ G1K 7P4, Canada
[3] Ctr Hosp Univ Quebec, Hotel Dieu, Dept Radiooncol, Quebec City, PQ G1R 2J6, Canada
关键词
CT scanner; CT metal artifacts; HU calibration; Monte Carlo calculation;
D O I
10.1118/1.2736777
中图分类号
R8 [特种医学]; R445 [影像诊断学];
学科分类号
1002 [临床医学]; 100207 [影像医学与核医学]; 1009 [特种医学];
摘要
Computed tomography (CT) images of patients having metallic implants or dental fillings exhibit severe streaking artifacts. These artifacts may disallow tumor and organ delineation and compromise dose calculation outcomes in radiotherapy. We used a sinogram interpolation metal streaking artifact correction algorithm on several phantoms of exact-known compositions and on a prostate patient with two hip prostheses. We compared original CT images and artifact-corrected images of both. To evaluate the effect of the artifact correction on dose calculations, we performed Monte Carlo dose calculation in the EGSnrc/DOSXYZnrc code. For the phantoms, we performed calculations in the exact geometry, in the original CT geometry and in the artifact-corrected geometry for photon and electron beams. The maximum errors in 6 MV photon beam dose calculation were found to exceed 25% in original CT images when the standard DOSXYZnrc/CTCREATE calibration is used but less than 2% in artifact-corrected images when an extended calibration is used. The extended calibration includes an extra calibration point for a metal. The patient dose volume histograms of a hypothetical target irradiated by five 18 MV photon beams in a hypothetical treatment differ significantly in the original CT geometry and in the artifact-corrected geometry. This was found to be mostly due to miss-assignment of tissue voxels to air due to metal artifacts. We also developed a simple Monte Carlo model for a CT scanner and we simulated the contribution of scatter and beam hardening to metal streaking artifacts. We found that whereas beam hardening has a minor effect on metal artifacts, scatter is an important cause of these artifacts. (c) 2007 American Association of Physicists in Medicine.
引用
收藏
页码:2119 / 2132
页数:14
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