| 高留刚,孙鸿飞,谢凯,林涛,眭建锋,倪昕晔.基于12和16 bit CT图像的金属伪影校正对放疗剂量分布的影响[J].中华放射医学与防护杂志,2017,37(12):938-945 |
| 基于12和16 bit CT图像的金属伪影校正对放疗剂量分布的影响 |
| Effects of metal artifact correction based on 12 and 16 bit CT images on dose distribution in radiotherapy |
| 投稿时间：2017-07-18 |
| DOI：10.3760/cma.j.issn.0254-5098.2017.12.012 |
| 中文关键词: 金属植入物 放疗 剂量 CT成像 伪影 |
| 英文关键词:Metallic implants Radiotherapy Dose Computed tomography Artifacts |
| 基金项目:江苏省自然科学基金（BK20151181） |
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| 中文摘要: |
| 目的 利用金属伪影去除技术去除基于12 bit和16 bit CT图像中金属植入物伪影，分析其对图像CT值分布和放疗剂量分布的影响。方法 将金属棒插入模体中，CT扫描得到12和16 bit原始CT图像，运用归一化伪影去除法（NMAR）分别对所得到的原始CT图像进行去伪影处理，得到NMAR修正后图像。临床中选取人工股骨头患者CT图像，对其进行同样处理。比较分析各图像伪影去除前后CT值分布。在放疗计划系统中，基于各图像设计放射治疗计划，计算剂量分布，比较分析各图像的剂量分布差异。结果 12 bit图像中金属CT值为3 071 HU，远小于金属实际CT值11 080 HU；16 bit图像中金属CT值为11 098 HU，与实际值很接近。原始CT图像在金属周围含有大量伪影，CT值与参考图像CT值偏差很大；NMAR校正后图像伪影显著减少，CT值与参考图像较接近。NMAR修正后16 bit图像的剂量分布与参考图像最接近，中心轴上最大剂量偏差为1.8%；12 bit图像与参考图像在金属后方剂量差异很大，最大剂量偏差为81.6%。射线穿过原始图像伪影区域后导致剂量分布与参考图像有明显差异，引起最大剂量偏差达21.6%。结论 含有金属植入物时，基于16 bit图像进行NMAR伪影校正可以得到准确的CT值分布，从而得到准确的剂量分布。 |
| 英文摘要: |
| Objective To apply metal artifact reduction algorithm to reduce metal artifacts based on 12 bit and 16 bit CT images, and aimed to analyze the effects on CT value and dose distribution. Methods The metal implant was inserted into the phantom, and the original 12 bit CT image and original 16 bit CT image were derived from CT scanning. The images were processed using NMAR algorithm, so the corrected 12 bit image and corrected 16 bit image were obtained. A patient's CT was chosen with artificial femur, and used the NMAR algorithm to reduce metal artifacts. Furthermore, the CT values of original images and corrected images were compared and analyzed. In the planning system, dose distribution was calculated based on each image by same radiation treatment plan. The dose distribution difference of each image was compared and analyzed. Results For the 12 bit image, the CT value of metal was 3 071 HU, which was much smaller than the metal's actual CT value 11 080 HU. The metal's CT value for the 16bit image was 11 098 HU, which was very close to the actual value. The original CT images contained a lot of artifacts around the metal, resulting in a large deviation of CT values from the reference image. After NMAR correction, metal artifacts were reduced significantly, and the CT values were close to the reference images. The dose distribution of the corrected 16 bit image was closest to that of the reference image. The maximum dose deviation on the central axis was 1.8%. The difference between the 12 bit image and the reference image downstream the metal was notable, and the maximum dose deviation on the central axis was 81.6%. The X-rays passed through the artifact region in original image, the dose distribution was obviously different from the reference image, and the maximum dose deviation was 21.6%. Conclusions For the patient with metal implant, using the NAMR algorithm on the 16 bit image result in accurate CT value of CT image, so that the accurate dose distribution will be obtained. |
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