磁共振加速器放疗计划中心点位置对剂量学的影响

目的分析磁共振加速器放疗计划中心点位置对偏中心肿瘤计划剂量学的影响。方法回顾性选取2020年在中山大学肿瘤防治中心接受放疗的19例偏中心肿瘤病例资料, 每个病例分别设计两组放疗计划:①按照磁共振加速器常规计划设计流程将计划等中心点固定设计调强放疗计划(A组)。②以靶区几何中心点作为治疗计划中心点设计调强放疗计划(B组)。比较两组放疗计划中靶区适形指数和均匀性指数、正常组织剂量和计划MU数。结果两组治疗计划均能满足临床剂量要求。A和B组计划靶区适形指数和均匀性指数差异均无统计学意义(P>0.05), 正常组织受照剂量也无明显差别(P>0.05)。但是, A组计划MU数(1 149±903)明显高于B组(970±652), 差异有统计学意义(t=2.804, P=0.012)。结论虽然磁共振加速器计划等中心点位置固定, 但计划质量可满足临床要求, 开展磁共振加速器治疗偏中心肿瘤是可行的。     

头颈部肿瘤调强适形放疗过程中重复修改计划的研究进展

头颈部肿瘤是常见的恶性肿瘤之一,放射治疗可以避免手术带来的容貌毁损,也可以最大限度地保留器官功能,又能取得良好的疗效,故在头颈部肿瘤的治疗中起了极大的作用.特别是调强适形放射治疗(IMRT)是一种新的提高治疗增益的放射治疗技术,在头颈肿瘤中运用IMRT,使剂量分布更适合于肿瘤靶区,增加肿瘤剂量,减少正常组织的照射剂量,提高肿瘤的局部控制率.在首次放疗后,头颈部肿瘤病人基本出现体重下降和肿瘤明显退缩,为不影响肿瘤靶区的放疗和进一步降低正常器官受量,适时的重复修改计划是十分必要的.     

医用加速器治疗中的质量保证及防范措施

卫生部发布的《放射治疗卫生防护与质量保证管理规定》保证了放射治疗的健康发展,也是加速器治疗质量保证的指南。加速器治疗的质量保证是指临床放疗医师根据患者的实际病情及加速器放射线治疗的特点,拟定出治疗方案,经物理人员核定照射剂量而设计出一套精确的治疗计划,由放疗技术人员准确完整、地执行,从而给患者的肿瘤区域以足够的科学的治疗剂量,最大可能地杀灭肿瘤细胞,同时尽可能地避免或最小限度地使周围健康组织及器官受照射,从而提高治疗效果,减少局部复发率及放射性并发症。据文献［１］报道,肿瘤照射量减少３％,肿瘤局…     

立体定向放射治疗体部肿瘤(附96例随访分析)

目的:通过临床随访观察,确定用立体定向分次放射治疗(Fractionted Stereotactic Radiotherapy,FSRT)体部肿瘤的近期疗效。对象与方法:96例体部肿瘤患者,其中38例肺癌、12例肝癌、11例胰腺癌、6例纵隔恶性肿瘤、6例食管癌、5例胃癌、5例胆管癌、6例直肠癌、3例宫颈癌和卵巢癌、4例椎骨转移瘤,继确诊和/或手术后,均经x线立体定向分次放射治疗。全部病例中67例(70％)经术前经皮穿刺针吸活组织检查或术后病理组织学检查证实,其余病例由临床、CT和/或磁共振等影像资料证实。用体箱、负压袋固定患者后CT扫描定位,X线立体定向放射治疗计划系统设计并优化治疗计划,加速器旋转照射。部分病人结合常规放射治疗。结果:X线立体定向放射治疗后1～3周内,90例(近94％)表现出临床症状明显改善,而且在此期间未发现1例严重并发症或死亡。肺癌患者随访CT检查32例,其中29例于FSRT后1～6个月肿瘤消失,2例肿瘤体积缩小50％以上,只有1例肿瘤大小无变化,有效率近97％。FSRT对其他肿瘤也有明显疗效,不仅可使原发癌灶缩小或消失,而且可使有癌转移的淋巴结消失。结论:FSRT是一种安全、无痛苦的、且能保持器官原有形态、结构及功能的治疗体部肿瘤的方法,它不仅适合于早期肿瘤患者,而且尤其适合于那些年老体弱,不能耐受手术的或术后残     

腹部肿瘤适形放疗的质量控制与摆位体会

目的：提高三维立体定向放射治疗的摆位质量。方法：应用瓦里安6MVX线直线加速器匹配中科院大恒医疗设备有限公司三维全身肿瘤立体放射治疗计划系统（STSR-2000）。对89例腹部肿瘤患者采用三维适形治疗（3DCRT），每次照射剂量3—4Gy每周照射3—5次，肿瘤总剂量为40-50Gy。结果：通过多种物理方法可以提高摆位治疗质量。     

放射治疗分次间与分次中眼晶状体的位移研究

目的 探讨眼晶状体在放射治疗分次间与分次中的运动范围.方法 对17例头颈部肿瘤患者的CT和MRI图像进行配准,勾画晶状体轮廓,分别确定中心坐标位置,进一步模拟分析分次间与分次中的晶状体位移.结果 左右晶状体在分次中与分次间均有不同程度的位移.与分次中运动幅度相比,在左右、前后和头脚方向上分次间晶状体运动的幅度均较大.结论 在自由状态下进行放射治疗时,不考虑摆位误差影响,仅以分次间与分次中运动幅度而论,晶状体的计划危及器官应在晶状体外延1.5mm为宜.     

子野直接优化方法提高鼻咽癌调强放疗下颈部靶区的分次剂量

鼻咽癌是头颈部常见的恶性肿瘤.放射治疗多采用调强放射治疗,照射范围主要包括鼻咽部肿瘤区和咽后淋巴结,以及下颈部和锁骨上区域[1-5].由于鼻咽部肿瘤区和左右侧颈部预防区分别给予不同的照射剂量[6],鼻咽和上颈部靶区、下颈部和锁骨上区调强放射治疗时照射次数相同,而下颈部和锁骨上区单次量低,放射生物效应差.本研究采用子野直接优化逆向调强技术,鼻咽和上颈部靶区、下颈部靶区分别独立设计子野,整个治疗计划分时段照射的方法实现鼻咽和上颈部靶区、下颈部靶区相同分次剂量不同照射剂量的目的.     

子野直接优化方法提高鼻咽癌调强放疗下颈部靶区的分次剂量

鼻咽癌是头颈部常见的恶性肿瘤.放射治疗多采用调强放射治疗,照射范围主要包括鼻咽部肿瘤区和咽后淋巴结,以及下颈部和锁骨上区域[1-5].由于鼻咽部肿瘤区和左右侧颈部预防区分别给予不同的照射剂量[6],鼻咽和上颈部靶区、下颈部和锁骨上区调强放射治疗时照射次数相同,而下颈部和锁骨上区单次量低,放射生物效应差.本研究采用子野直接优化逆向调强技术,鼻咽和上颈部靶区、下颈部靶区分别独立设计子野,整个治疗计划分时段照射的方法实现鼻咽和上颈部靶区、下颈部靶区相同分次剂量不同照射剂量的目的.     

子野直接优化方法提高鼻咽癌调强放疗下颈部靶区的分次剂量

鼻咽癌是头颈部常见的恶性肿瘤.放射治疗多采用调强放射治疗,照射范围主要包括鼻咽部肿瘤区和咽后淋巴结,以及下颈部和锁骨上区域[1-5].由于鼻咽部肿瘤区和左右侧颈部预防区分别给予不同的照射剂量[6],鼻咽和上颈部靶区、下颈部和锁骨上区调强放射治疗时照射次数相同,而下颈部和锁骨上区单次量低,放射生物效应差.本研究采用子野直接优化逆向调强技术,鼻咽和上颈部靶区、下颈部靶区分别独立设计子野,整个治疗计划分时段照射的方法实现鼻咽和上颈部靶区、下颈部靶区相同分次剂量不同照射剂量的目的.     

子野直接优化方法提高鼻咽癌调强放疗下颈部靶区的分次剂量

鼻咽癌是头颈部常见的恶性肿瘤.放射治疗多采用调强放射治疗,照射范围主要包括鼻咽部肿瘤区和咽后淋巴结,以及下颈部和锁骨上区域[1-5].由于鼻咽部肿瘤区和左右侧颈部预防区分别给予不同的照射剂量[6],鼻咽和上颈部靶区、下颈部和锁骨上区调强放射治疗时照射次数相同,而下颈部和锁骨上区单次量低,放射生物效应差.本研究采用子野直接优化逆向调强技术,鼻咽和上颈部靶区、下颈部靶区分别独立设计子野,整个治疗计划分时段照射的方法实现鼻咽和上颈部靶区、下颈部靶区相同分次剂量不同照射剂量的目的.     

加速器MVCBCT扫描图像在自适应放疗中应用的可行性研究

目的 探讨加速器成像射束影像系统（IBL）的全扇形束和大射野（EFOV）两种模式扫描得到的兆伏级锥形束断层（MV CBCT）图像可否用于剂量计算。方法 利用大孔径CT和在IBL的全扇形束和EFOV模式下对CIRS 062M型电子密度模体进行扫描,在Pinnacle计划系统中分别建立电子密度曲线。用CT和加速器MV级CBCT模式扫描头颈、胸、腹盆腔部仿真模体,利用CT图像制作调强计划,并将计划移植于MV CBCT的图像中,利用相应的电子密度曲线计算剂量,比较靶区及危及器官剂量分布。结果 MV CBCT图像中剂量分布比参考计划剂量偏低,并且在头颈、胸、腹盆腔模体中偏差依次增大。与参考计划相比,头颈部靶区剂量和危及器官剂量分布一致,偏差均在3%以内。胸部和腹盆腔靶区和危及器官的剂量分布均有大幅度的降低,偏差分别达到5%和10%,超出了临床接受范围。结论 在加速器IBL中全扇形束模式条件下,头颈部患者扫描得到的MV CBCT图像可在自适应放疗中用于剂量计算,胸、腹盆腔部位在EFOV模式下仅可用于图像引导,不能用于剂量计算。     

自适应多叶光栅在脑肿瘤质子放疗中的应用

目的 通过比较使用和不使用自适应多叶光栅的脑肿瘤质子调强治疗计划,评估自适应多叶光栅的临床应用价值。方法 选取20例脑肿瘤术后行放射治疗的患者,在同样优化条件下为每位患者分别设计使用和不使用自适应多叶光栅的质子调强治疗计划,通过比较靶区适形指数(CI)、靶区均匀性指数(HI)和正常组织受量对两组方案进行评价。结果 使用自适应多叶光栅设计质子调强治疗计划,靶区CI均值从0.58提高到0.66,50%处方剂量体积均值从797.70 cm³降低到638.15 cm³,耳蜗、脑干、视交叉、视神经、眼晶状体的辐射受量均显著减少(t=2.06、3.02、2.11、2.58、2.67,P < 0.05)。另外,两组方案间靶区的HI值以及计划的机器跳数差异没有统计学意义(P > 0.05)。结论 自适应多叶光栅能显著降低靶区周围正常组织的照射剂量,对保护靶区外危及器官具有积极作用,具有良好的临床应用前景。     

Assessment of semi-automated stereotactic treatment planning for online adaptive radiotherapy in ethos

IntroductionThe Ethos treatment planning system allows for the rapid generation of online adaptive treatment plans while the patient is on the treatment couch. One promising application of online adaptive radiotherapy is its use in stereotactic radiotherapy. The purpose of this study was to ensure the Ethos treatment planning system (TPS) can produce clinically acceptable stereotactic plans, that are non-inferior to those from the Eclipse TPS.MethodForty patients that received previous stereotactic radiotherapy treatment on a Halcyon, 20 of which were lung cases, and 20 that were brain cases, were replanned using the Ethos TPS. The generated IMRT and VMAT plans were compared to the clinical Eclipse VMAT plan.ResultsThis study found that the Ethos TPS can produce VMAT plans of equivalent quality (target coverage, conformity and OAR doses) to those from the Eclipse TPS for lung SBRT and brain SRT. The IMRT plans produced by the Ethos planning system were marginally inferior to Eclipse VMAT plans, with the differences likely primarily due to beam geometry rather than the optimization system. Ethos plans were generally more modulated than Eclipse plans. With careful selection of optimization structures and reduction in the body contour, VMAT plan generation time could be reduced by 87%.ConclusionEthos can generate stereotactic VMAT plans that are equivalent to those from Eclipse in the timeframe required for online adaptive radiotherapy.     

变形配准与经验计算剂量累加法用于肺癌放疗计划累加剂量计算的研究

目的 应用变形配准功能评价肺癌患者放疗计划中正常组织和危及器官的累加剂量,并与经验计算剂量累加法进行比较.方法 回顾性分析10例肺癌患者,放疗前制定了三维适形或调强治疗计划,放疗过程中重新行CT模拟,并重新设计相同的治疗计划.采用Mimvista软件,运用变形配准,分别在2次CT图像上进行剂量累加.采用经验计算剂量累加法,计算2次放疗计划的正常组织和危及器官的累加剂量,分别对两种方法的双侧肺组织、心脏及脊髓的受照剂量体积以及平均剂量等参数,进行比较.结果 定位和复位图像采用相同的计划方式时,两种方法所得正常组织和危及器官的累积受照体积和剂量等参数差异无统计学意义,仅右肺的平均剂量除外(t=2.98,P＜0.05).结论 变形配准法可以准确评价肺癌患者多次放疗计划中正常组织和危及器官的累加剂量.肺癌患者的靶区变化不大并且采用相同的计划方式时,应用经验计算剂量累加法,可粗略评价肺和心脏等正常组织和危及器官的剂量体积.     

不同调强方式在胸中上段食管癌放疗中的剂量学研究

目的 对胸中上段食管癌患者进行静态调强（IMRT）和容积旋转调强（VMAT）两种放疗方式的剂量学对比研究。方法 对20例IMRT治疗的食管癌患者行VMAT（单弧和双弧）计划的重新设计。在单弧的VMAT计划中,对其中5例患者行不同子野间隔（4°、3°、2°）以及不同计划系统（Monaco和MasterPlan）的计划设计。比较靶区和危及器官（OAR）的剂量学差异及治疗参数。结果 双弧VMAT计划各项靶区剂量学参数明显好于IMRT计划和单弧VMAT计划（P<0.05）,靶区均匀性（HI）（P<0.05）和适形度（CI）（P<0.05）最好。危及器官参数VMAT可在一定程度上降低OAR的受照剂量,但是IMRT对肺组织和正常组织（E-P）的低剂量保护要优于VMAT（P<0.05）;不同子野间隔的VMAT计划中,2°相对于3°和4°其OAR的受照剂量是减小的（P<0.05）,除了心脏的D_mean;不同计划系统设计的VMAT计划,以Monaco对OAR的保护为最优（P<0.05）;VMAT的机器跳数少于IMRT,而且有效节省了治疗时间。 结论 VMAT方式相对于IMRT能够实现更好的靶区覆盖、均匀性和适形度,同时能降低脊髓、肺组织、心脏和E-P的受照剂量;对于VMAT来说,双弧技术、小子野角度间隔能够进一步地改善靶区和OAR的受照剂量;此外,在物理参数和优化参数一致的前提下,Monaco可以更好地保护OAR。     

非小细胞肺癌不同调强放疗方案的剂量学对比研究

目的 探讨非小细胞肺癌调强放疗计划设计的合理方案。方法 对11例非小细胞肺癌患者分别制定2种放疗计划:PTV60计划的PTV为(GTV+6～8mm)+呼吸动度+摆位误差,对PTV获得60Gy处方剂量进行归一;PTV70计划的PTV为GTV+呼吸动度+摆位误差,对PTV获得70Gy处方剂量进行归一。通过剂量体积直方图分析2种治疗计划的靶区剂量分布和危及器官受量,并进行剂量学的对比研究。结果 PTV70计划接受60Gy剂量的靶区体积明显高于PTV60计划,两组在靶区剂量均匀性方面相似。PTV70计划的肺V₂₀较PTV60计划平均下降(1.69±0.42)%,两组相比差异有统计学意义(t=0.047,P=0.002);肺V₅平均下降(1.29±1.09)%,两组相比差异无统计学意义。结论 在非小细胞肺癌调强放疗设计中,PTV70计划优于PTV60计划。     

子宫颈癌术后调强放疗照射野设计的探讨

目的 通过对子宫颈癌调强放疗各种布野方案的比较,探讨符合临床要求的最佳照射方案。方法 对10例子宫颈癌患者采用调强治疗方案,处方剂量为46 Gy,分次量为2 Gy。每位患者做6个不同的治疗计划,分别为5野、7野、9野均分照射,初始入射角度选用0°和180°。分别计算比较靶区的覆盖度、均匀性、适形度各项指标。结果 7野和9野的靶区适形度基本一致,7野的均匀性最好,5野靶区覆盖度也能达到要求,但适形度和均匀度都次于7、9野;9野IMRT计划与5野IMRT计划相比没有减少正常组织的受照剂量,但增加了子野数和照射的总跳数,延长了治疗时间。结论 在子宫颈癌的调强放疗中,综合考虑各种物理和生物因素,建议在设计照射野时尽量选择7野照射。     

Adaptive Radiation Therapy for Localized Mesothelioma with Mediastinal Metastasis Using Helical Tomotherapy

The purpose of this study was to compare 2 adaptive radiotherapy strategies with helical tomotherapy. A patient having mesothelioma with mediastinal nodes was treated using helical tomotherapy with pretreatment megavoltage CT (MVCT) imaging. Gross tumor volumes (GTVs) were outlined on every MVCT study. Two alternatives for adapting the treatment were investigated: (1) keeping the prescribed dose to the targets while reducing the dose to the OARs and (2) escalating the target dose while maintaining the original level of healthy tissue sparing. Intensity modulated radiotherapy (step-and-shoot IMRT) and 3D conformal radiotherapy (3DCRT) plans for the patient were generated and compared. The primary lesion and nodal mass regressed by 16.2% and 32.5%, respectively. Adapted GTVs and reduced planning target volume (PTV) margins of 4 mm after 22 fractions decrease the planned mean lung dose by 19.4%. For dose escalation, the planned prescribed doses may be increased from 50.0 to 58.7 Gy in PTV₁ and from 60.0 to 70.5 Gy in PTV₂. The step-and-shoot IMRT plan was better in sparing healthy tissue but did not provide target coverage as well as the helical tomotherapy plan. The 3DCRT plan resulted in a prohibitively high planned dose to the spinal cord. MVCT studies provide information both for setup correction and plan adaptation. Improved healthy tissue sparing and/or dose escalation can be achieved by adaptive planning.     

Validation of automated post-adjustments of HDR prostate brachytherapy treatment plans by quantitative measures and oncologist observer study

PURPOSEThe aim was to evaluate a postprocessing optimization algorithm's ability to improve the spatial properties of a clinical treatment plan while preserving the target coverage and the dose to the organs at risk. The goal was to obtain a more homogenous treatment plan, minimizing the need for manual adjustments after inverse treatment planning.MATERIALS AND METHODSThe study included 25 previously treated prostate cancer patients. The treatment plans were evaluated on dose-volume histogram parameters established clinical and quantitative measures of the high dose volumes. The volumes of the four largest hot spots were compared and complemented with a human observer study with visual grading by eight oncologists. Statistical analysis was done using ordinal logistic regression. Weighted kappa and Fleiss’ kappa were used to evaluate intra- and interobserver reliability.RESULTSThe quantitative analysis showed that there was no change in planning target volume (PTV) coverage and dose to the rectum. There were significant improvements for the adjusted treatment plan in: V150% and V200% for PTV, dose to urethra, conformal index, and dose nonhomogeneity ratio. The three largest hot spots for the adjusted treatment plan were significantly smaller compared to the clinical treatment plan. The observers preferred the adjusted treatment plan in 132 cases and the clinical in 83 cases. The observers preferred the adjusted treatment plan on homogeneity and organs at risk but preferred the clinical plan on PTV coverage.CONCLUSIONSQuantitative analysis showed that the postadjustment optimization tool could improve the spatial properties of the treatment plans while maintaining the target coverage.     

An evaluation of adaptive planning by assessing the dosimetric impact of weight loss throughout the course of radiotherapy in bilateral treatment of head and neck cancer patients

The purpose of this study was to investigate the dosimetric impact of weight loss in head and neck (H&N) patients and examine the effectiveness of adaptive planning. Data was collected from 22 H&N cancer patients who experienced weight loss during their course of radiotherapy. The robustness of Intensity Modulated Radiation Therapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT) treatment plans were compared including the potential need for replanning. The dosimetric impact of weight loss was evaluated by calculating a verification plan for each patient on an assessment CT scan taken during the course of treatment. Using a regression analysis, significance was tested for the dosimetric change in target volumes and 10 specific organs at risk (OAR) using an anatomical separation difference in the H&N at corresponding levels. For both the IMRT and VMAT plans, a significant correlation was found for the dose to 5% of the high risk Planning Target Volume (PTV) (D₅), dose to 95% of the intermediate risk PTV and Clinical Target Volume (CTV) (D₉₅), and the percentage of the pharynx receiving 65 Gy. An independent t-test was also performed for each metric in the VMAT and IMRT plans showing the dose to 95% of the intermediate risk PTV as significant. No quantitative method for finding the threshold of anatomical separation difference requiring a replan was established. Based on the increase in dose to organs at risk and increased target coverage due to separation loss, it was concluded that adaptive radiotherapy may not always be necessary when alignment of bony anatomy and remaining soft tissue is within tolerance. Physician judgment and preference is needed in such situations.