2D脊形滤波器提高碳离子治疗效率的临床可行性研究

张利嘉, SCHLEGEL Nicki, 盛尹祥子, 韩榕城, 赵静芳

  1. 1.上海市质子重离子医院放射物理科，上海 201321
    2.上海市放射肿瘤学重点实验室，上海 201321
    3.上海质子重离子放射治疗工程技术研究中心，上海 201321
    4.复旦大学附属肿瘤医院放射治疗科，复旦大学上海医学院肿瘤学系，上海 200032
  • 收稿日期:2024-11-22 修回日期:2025-02-14 出版日期:2025-05-30 发布日期:2025-06-10
  • 通信作者: 赵静芳
  • 作者简介:张利嘉（ORCID: 0009-0003-4326-8779），硕士，研究实习员。
  • 基金资助:
    上海市卫生健康委员会青年项目(20244Y0049)

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摘要/Abstract

摘要：

背景与目的： 脊形滤波器（ripple filter，RiFi）是一种在粒子束治疗中展宽布拉格峰的被动能量调制器。1D-RiFi为波浪形结构，能将单能碳离子束流展宽至3 mm，而2D-RiFi采用二维沟槽结构，能将束流展宽至6 mm。本研究旨在以1D-RiFi为参照，通过对比水模体计划和临床患者计划，分析2D-RiFi在剂量分布优化、治疗效率提升及危及器官（organ at risk，OAR）剂量控制方面的潜在优势，评估其在临床中的可行性和实用性。方法： 研究设计基于水模体和20例患者的碳离子治疗计划，分别使用1D-RiFi和2D-RiFi生成治疗计划。水模体计划采用80 mm×80 mm×80 mm的立方体靶区，射程分别为95、105、190和290 mm。从上海市质子重离子医院接受碳离子治疗的患者中，按照不同肿瘤部位的比例进行分层，随后采用计算机生成随机数的方法，通过简单随机抽样选取20例患者（6例头颈部肿瘤患者、4例前列腺肿瘤患者、4例肺部肿瘤患者、2例胰腺肿瘤患者、2例肝肿瘤患者和2例肩部肿瘤患者）。重点分析靶区剂量均匀性指数（homogeneity index，HI）、剂量适形性指数（conformity index，CI）、临床靶区（clinical target volume，CTV）受到95%处方剂量的体积（V95）等剂量学指标，以及OAR剂量。统计比较两种RiFi计划所需的能量层数、束流时间和照射时间。所有数据均采用Wilcoxon秩和检验进行统计学分析，P<0.05为差异有统计学意义。本研究已获得上海市质子重离子医院医学伦理委员会批准（伦理编号：240311EXP-01）。结果： 对于水模体计划，1D-RiFi计划的HI、CI、V95和平坦度分别为0.04±0.01、1.10±0.03、99.92%±0.06%和6.52%±0.61%，2D-RiFi计划的HI、CI、V95和平坦度分别为0.04±0.01、1.11±0.04、99.92%±0.06%和7.52%±0.81%。1D-RiFi计划末端挡块和侧向挡块的平均剂量分别为（1.34±0.43）Gy[相对生物效应（relative biological effectiveness，RBE）]和（0.98±0.05）Gy（RBE），2D-RiFi计划末端挡块和侧向挡块的平均剂量分别为（1.47±0.33）Gy（RBE）和（0.94±0.03）Gy（RBE）。相比1D-RiFi，使用2D-RiFi的计划平均束流时间下降43%，能量层数平均下降48%。临床患者计划比较显示，1D-RiFi计划的HI、CI和V95分别为0.07±0.04、1.94±0.67和98.81%±1.61%，2D-RiFi计划的HI、CI和V95分别为0.07±0.05、1.95±0.70和98.79%±1.69%，结果差异无统计学意义（P=0.77、0.65和0.66）。使用2D-RiFi时OAR的平均剂量略微增加（平均增加0.8%，P=0.62），但均满足耐受标准。使用2D-RiFi的临床患者计划能量层数下降45%~50%，平均下降48%；束流时间下降32%~49%，平均下降44%；照射时间下降28%~41%，平均下降36%。结论： 使用2D-RiFi制定碳离子治疗计划可以获得与1D-RiFi治疗计划相同的靶区覆盖，OAR受照剂量虽略有增加，但均可满足临床要求。应用2D-RiFi可以显著减少碳离子治疗的能量层数、束流时间和照射时间，提高治疗效率。

关键词: 脊型滤波器, 碳离子治疗, 剂量学, 临床效率, 剂量分布优化

Abstract:

Background and purpose: The ripple filter (RiFi) is a passive energy modulator used in particle beam therapy to broaden the Bragg peak. The 1D-RiFi features a wavy structure that can broaden a monoenergetic carbon ion beam to 3 mm, while the 2D-RiFi employs a two-dimensional groove structure to achieve a 6 mm beam broadening. This study aimed to evaluate the potential advantages of the 2D-RiFi over the 1D-RiFi in terms of dose distribution optimization, treatment efficiency, and organ at risk (OAR) dose control by comparing water phantom and clinical patient plans. Methods: Carbon ion treatment plans were designed for water phantoms and 20 patients using both 1D-RiFi and 2D-RiFi. The water phantom plans targeted a cubic region of interest (80 mm×80 mm×80 mm) at ranges of 95, 105, 190 and 290 mm. From patients who underwent carbon ion therapy at Shanghai Proton and Heavy Ion Center, 20 cases were selected via simple random sampling with computer-generated random numbers, stratified by the proportion of different tumor sites (6 head and neck tumors, 4 prostate tumors, 4 lung tumors, 2 pancreatic tumors, 2 liver tumors and 2 shoulder tumors). Key dosimetric metrics, including homogeneity index (HI), conformity index (CI) and clinical target volume (CTV) coverage by 95% prescription dose (V95), were analyzed along with OAR doses. Energy layers, beam time, and irradiation time were compared between the two RiFi types. Statistical analysis was performed using the Wilcoxon rank-sum test, with a significance level of P<0.05. This study was approved by the ethics committee of Shanghai Proton and Heavy Ion Center (approval number: 240311EXP-01). Results: For water phantom plans, the 1D-RiFi plans achieved HI of 0.04±0.01, CI of 1.10±0.03, V95 of 99.92%±0.06% and flatness of 6.52%±0.61%, while the 2D-RiFi plans achieved HI of 0.04±0.01, CI of 1.11±0.04, V95 of 99.92%±0.06%, and flatness of 7.52%±0.81%. The mean doses to the distal and lateral block in 1D-RiFi plans were (1.34 Gy±0.43) Gy [relative biological effectiveness (RBE)]and (0.98±0.05) Gy (RBE), respectively, compared to (1.47±0.33) Gy (RBE) and (0.94±0.03) Gy (RBE) for 2D-RiFi plans. The use of 2D-RiFi reduced the average beam-on time by 43% and the number of energy layers by 48%. For clinical plans, the 1D-RiFi plans had HI of 0.07±0.04, CI of 1.94±0.67, and V95 of 98.81%±1.61%, compared to HI of 0.07±0.05, CI of 1.95±0.70, and V95 of 98.79%±1.69% for the 2D-RiFi plans, with no statistically significant differences (P=0.77, 0.65 and 0.66, respectively). OAR mean doses increased slightly with the 2D-RiFi plans (average increase of 0.8%, P=0.62) but remained within clinically acceptable limits. The 2D-RiFi plans reduced energy layers by 45%-50% (average 48%), beam time by 32%-49% (average 44%), and irradiation time by 28%-41% (average 36%). Conclusion: Treatment plans using the 2D-RiFi achieved comparable target coverage to those using the 1D-RiFi, with a slight but clinically acceptable increase in OAR doses. The application of the 2D-RiFi significantly reduced the number of energy layers, beam time and irradiation time in carbon ion therapy, enhancing treatment efficiency.

Key words: Ripple filter, Carbon ion therapy, Dosimetry, Clinical efficiency, Dose distribution optimization

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