Image reconstruction and the effect on dose calculation for hip prostheses.
Image reconstruction and the effect on dose calculation for hip prostheses.
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DOI：
10.1016/s0958-3947(02)00246-7
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发表时间：
2003-01-01
期刊：
影响因子：
--
通讯作者：
Mohan, Radhe
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文献类型：
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作者：
Keall, Paul J;Chock, Leah B;Mohan, Radhe
使用过滤反投影(FBP)方法时，高原子序数的假体(如髋关节假体和牙齿填充)会在计算机断层扫描(CT)图像上造成条纹伪影。这些条纹伪影严重降低了我们区分肿瘤体积的能力。此外，不正确的Hounsfield数产生不正确的电子密度信息，这可能导致错误的剂量计算，并因此危及临床结果。本研究的目的是评估包含人工髋关节的前列腺癌患者放射治疗计划中伪影的剂量学结果。将对应于铁假体的CT编号插入现有CT图像集的右侧股骨头中。该无伪影图像被用作标准图像集。通过图像集的CT投影形成正弦图，并在此基础上使用滤波反投影和迭代去模糊方法生成重建图像集。这些重建的图像集包含伪影。然后使用蒙特卡罗系统对标准和重建的CT图像集计算前列腺治疗计划。在假体附近，重建图像和标准图像之间的CT数有很大不同。然而，由于CT数差仅覆盖很小的区域，重建图像集和标准图像集上的剂量分布没有显著差异。前列腺、直肠和膀胱的剂量-体积直方图实际上是相同的。我们的结果表明，尽管CT图像伪影限制了我们区分肿瘤和关键结构的能力，但对于包含髋关节假体的前列腺计划，在无伪影图像集和包含伪影图像集上计算的剂量分布没有显著差异。
High atomic number inserts, such as hip prostheses and dental fillings, cause streak artifacts on computed tomography (CT) images when filtered back-projection (FBP) methods are used. These streak artifacts severely degrade our ability to differentiate the tumor volume. Also, incorrect Hounsfield numbers yield incorrect electron density information that may lead to erroneous dose calculations, and, as a result, compromise clinical outcomes. The aim of this research was to evaluate the dosimetric consequences of artifacts during radiotherapy planning of a prostate patient containing a hip prosthesis. The CT numbers corresponding to an iron prosthesis were inserted into the right femoral head of an existing CT image set. This artifact-free image was used as the standard image set. CT projections through the image set formed the sinogram, from which filtered back projection and iterative deblurring methods were used to create reconstructed image sets. These reconstructed image sets contained artifacts. Prostate treatment plans were then calculated using a Monte Carlo system for the standard and reconstructed CT image sets. Close to the prosthesis, the CT numbers between the reconstructed and standard image sets differed substantially. However, because the CT number differences covered only a small area, the dose distributions on the reconstructed and standard image sets were not significantly different. The dose-volume histograms for the prostate, rectum, and bladder were virtually identical. Our results indicate that even though CT image artifacts restrict our ability to differentiate tumors and critical structures, the dose distributions for a prostate plan containing a hip prosthesis, calculated on both artifact-free image sets and image sets containing artifacts, are not significantly different.