| 马霄云,张雁山,张梦灵.重离子放射治疗靶区边缘剂量跌落分析[J].肿瘤学杂志,2021,27(5):390-394. |
| 重离子放射治疗靶区边缘剂量跌落分析 |
| Analysis of Dose Decay at the Edge of Beam in Heavy Ion Radiotherapy |
| 投稿时间：2021-02-22 |
| DOI：10.11735/j.issn.1671-170X.2021.05.B012 |
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| 中文关键词: 重离子 均匀扫描 剂量跌落 |
| 英文关键词:heavy ion uniform scanning dose decay |
| 基金项目:甘肃省科技厅点研发计划-社会发展项目（19YF3FH001） |
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| 中文摘要: |
| 摘 要：［目的］ 分析重离子放疗时靶区后缘的剂量跌落梯度，利用重离子治疗计划系统（treatment planning system，TPS），分析固定束照射时在不同的入射方式、多种剂量分割条件下靶区边缘的剂量跌落速度，为重离子放射治疗时靶区与危及器官之间的相对安全距离提供参考数据。 ［方法］ 在TPS中选择重离子均匀扫描模式，在均匀水模体中设计多种常用分割条件下单野照射、两野对穿照射、两野正交照射的重离子计划，以射野后缘中心轴线上剂量开始快速下降的位置为基准，采集各计划的剂量跌落数据。 ［结果］ 剂量跌落数据分析显示，单野照射时，射野后缘5mm距离后剂量可跌落至约20%；两野对穿照射时，射野后缘5mm距离后剂量可跌落至约50%；两野正交照射时，射野后缘5mm距离后剂量可跌落至约30%~38%。重离子射束后缘的剂量跌落迅速，远优于X射线，在设计放射治疗计划时，可在满足靶区照射剂量的同时，使紧邻靶区的危及器官剂量限值达到临床可接受范围内。［结论］ 通过计划系统中的数据分析，可以看出重离子束射野后缘剂量的锐度是优于侧缘的，但其产生的X线污染也不容忽视；在实际情况中，重离子束穿射的人体组织是不均匀的，这也会对射野后方的剂量跌落曲线产生影响。故在实际临床中，还需考虑不均匀的CT值对重离子射束剂量跌落的影响。 |
| 英文摘要: |
| Abstract：［Objective］ To analyze the dose decay at the edge of the beam under different incident modes and multiple dose segmentation conditions during fixed beam irradiation with treatment planning system(TPS) in heavy ion radiotherapy. ［Methods］ Uniform scanning mode was selected in heavy ion TPS，and multiple heavy ion treatment plans with single beam irradiation，two beams irradiation in opposite direction and two beams orthogonal irradiation under common segmentation conditions were designed in a homogeneous water phantom. The dose decay data of each plan were collected based on the position of the central axis of the edge of beam where the dose began to drop rapidly. ［Results］ The analysis of dose decay data showed that in the case of single beam irradiation，the dose could drop to about 20% after 5mm distance from the back edge of the beam. When two beams were irradiated in opposite direction，the dose could drop to about 50% in 5mm away from the posterior edge of the beam. In orthogonal irradiation of two beams，the dose of posterior edge of the beam could drop to about 30%~38% in a distance of 5mm. The dose drop at the back edge of the heavy ion beam center was rapid，which was far better than X-ray. When designing the radiotherapy treatment plan，the dose limit of organs at risk adjacent to the target region should reach the clinically acceptable range while achieving the irradiation dose at the target region. ［Conclusions］ Through the data analysis in the TPS，it can be seen that the sharpness of the dose at the back edge of the heavy ion beam is better than that at the lateral edge，but the generated X-ray pollution cannot be ignored. In practice，the tissue of human body is heterogeneous，which will also affect the dose drop curve behind the field. Therefore，the effect of uneven CT value on the dose drop of heavy ion beam should also be considered in clinical treatment. |
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