螺旋断层放疗系统在胸部肿瘤治疗中的临床应用

放射治疗是胸部肿瘤治疗中最重要的手段之一,但胸部肿瘤的放射治疗由于受呼吸、心博因素的影响,在常规放疗时代难以确保射线的精确投射,进而带来明显的不良反应,限制了其发展。以螺旋断层放疗系统（TOMO）为代表的最新一代精确放疗系统,可通过螺旋照射、图像引导放疗（IGRT）及自适应放疗（ART）等新技术的应用,在提高放疗精确性的同时,减少正常组织的放射损伤,从而突破了放射治疗在胸部肿瘤治疗中的“瓶颈”,为胸部肿瘤的放疗翻开了崭新的一页。     

螺旋断层放射治疗在头颈部肿瘤中的应用

头颈部肿瘤是常见的恶性肿瘤之一,放射治疗不仅治疗效果理想,还可保留患者的容貌及功能,故在头颈部肿瘤的治疗中发挥了重要的作用。螺旋断层放射治疗（helical tomotherapy, HT）是近十年发展起来的一种新的调强适形放疗技术,目前已初步用于鼻咽癌、口咽癌等多种头颈部肿瘤的治疗。与常规加速器调强放疗相比,螺旋断层放疗在放疗靶区的剂量覆盖及危及器官的保护等方面具有一定优势。     

利用兆伏级CT分析头颈部肿瘤在螺旋断层放疗中的摆位误差

目的：应用螺旋断层放疗机（Tomo therapy）自带的兆伏级CT（MVCT）影像引导,测定并分析采取面网固定方式的头颈部肿瘤患者的摆位误差,并依此计算CTV-PTV外扩Margin值的大小。方法对34例采取面网固定装置的头颈部肿瘤患者,每次治疗前均行MVCT扫描,将扫描所得MVCT图像与定位图像（kVCT）行靶区位置配准,分析患者左右（x）、头脚（y）、腹背（z）和横断面旋转（Roll）方向的误差值,根据公式M＝2．5∑＋0．7σ计算出合理的CTV-PTV外扩Margin值。结果34例患者共行640次MVCT扫描,线性误差在x、y、z方向的系统误差＆#177;随机误差分别为：（-0．15＆#177;0．55） mm、（0．30＆#177;0．56） mm、（0．35＆#177;0．71）mm;在Roll方向的旋转误差为（-0．07＆#177;0．52）＆#176;。 CTV-PTV外放边界在x、y、z三个方向Margin值分别为3．31 mm、5．32 mm和3．35 mm。结论通过对摆位误差的分析为CTV-PTV外扩边界提供了理论依据,为精确放疗提供必要的质量保证。     

螺旋断层放射治疗在胸部肿瘤中的应用

目的 螺旋断层放射治疗是近十年发展起来的一种新的调强适形放疗技术,其独创性的设计以螺旋CT旋转扫描方式,结合计算机断层影像导航调校,突破了传统加速器的诸多限制,对肿瘤患者进行高效、精确、安全的治疗.本文总结螺旋断层放射治疗在胸部肿瘤的临床应用,探讨其治疗发展方向及最新动态.方法 以“螺旋断层放疗,胸部肿瘤,肺癌,肺转移瘤,胸膜间皮瘤,食管癌”为关键词,检索PubMed及CNKI期刊全文数据库2007-04-2016-04的相关文献,共检索到中文文献286条,英文文献297条.纳入标准:(1)肺癌、肺转移瘤的螺旋断层放疗;(2)胸膜间皮瘤的螺旋断层放疗;(3)食管癌的螺旋断层放疗.根据纳入标准,符合分析的文献26篇.结果 螺旋断层放疗在胸部肿瘤有较好的疗效,其实现了高适形和均匀度的剂量分布,从而提高了靶区剂量和降低了周围正常组织剂量,在放疗靶区的剂量覆盖及危及器官的保护等方面具有一定优势,在胸部复杂不规则靶区,范围较大的靶区及多个靶点的放疗方面具有明显的优势,并且未明显增加放疗相关的毒副作用.结论 螺旋断层放疗凭借对靶区的剂量覆盖及正常器官的保护等方面的独特优势,提高了肺癌、胸膜间皮瘤、食管癌等放疗疗效.但因目前相关临床试验较少,其治疗地位仍需大型多中心随机临床试验来确立.     

头颈部肿瘤螺旋断层放疗与动态调强放疗剂量学比较—Meta分析

目的:探讨螺旋断层放疗的优势及不足,为临床治疗提供有价值的循证医学依据.方法:计算机检索PubMed、EMBASE、Science、中国知网和万方等数据库,筛选头颈部肿瘤螺旋断层放疗与动态调强放疗剂量学比较的文章,应用StataSE 12.0软件对满足条件的数据进行Meta分析.结果:纳入10篇文章.螺旋断层放疗较动态调强放疗靶区的均匀性明显提高(SMD=-1.529,95％ CI:-2.265 ～-0.793,P＜0.001),脊髓Dmax 及脑干Dmean等比较,差异均有统计学意义.而脑干Dmax视交叉Dmax及喉Dean等比较,差异无统计学意义.结论:头颈部肿瘤螺旋断层放疗比动态调强放疗靶区分布更均匀,可明显降低高剂量区的照射靶体积,对危及器官如脊髓、脑干的保护更优.     

螺旋断层放射治疗技术在恶性肿瘤中的治疗进展

摘 要：随着现代放射治疗技术的不断发展,放疗在恶性肿瘤治疗中的地位日益显著,已成为不可或缺的一环。三维适形放疗(three-dimensional conformal radiotherapy,3DCRT),调强放疗（intensity-modulated radiotherapy,IMRT）、容积旋转调强放疗（volumetric-modulated arc therapy,VMAT）等放疗新技术在临床中得到应用广泛。全文综述新型放疗技术—螺旋断层放疗（helical tomotherapy）在全身各系统肿瘤放射治疗过程中优势、缺点及相关临床应用进展。     

螺旋断层放疗技术的特点与临床应用

螺旋断层放疗是一种新兴的调强放疗(intensity-modulated radiotherapy,IMRT)技术,在放疗过程中,机架和治疗床连续运动,与螺旋CT扫描过程相似.固定在滑环机架上的直线加速器射出6 MV-X线束,并经气动二维动态多叶光栅调制后形成许多扇形射野进行螺旋照射.     

螺旋断层放疗治疗髓母细胞瘤的疗效观察

目的 探讨螺旋断层放疗技术治疗髓母细胞瘤的剂量学优势、不良反应及疗效。方法 2011年2月至2011年10月,4例髓母细胞瘤患者接受螺旋断层放射治疗。术后瘤床临床靶区（CTV1）剂量：50.4Gy／28f,每次18Gy,5次／周;全脑全脊髓临床靶区（CTV2）剂量：30.6Gy／17f,每次1.8Gy,5次／周。结果 4例患者接受照射的均匀性和适形性较好,重要器官的照射剂量低,治疗时间均小于15min。4例患者均获随访,中位随访9个月（4～15个月）,至随访截止时间无1例复发。主要不良反应为骨髓抑制和恶心呕吐,4例患者均可耐受。结论 螺旋断层放疗治疗髓母细胞瘤的疗效和剂量分布较好,为治疗髓母细胞瘤开辟了一个新的治疗平台。     

鼻咽癌螺旋断层放疗与常规调强放疗剂量学及对唾液腺保护的分析

摘 要：［目的］ 比较鼻咽癌在螺旋断层放疗（helical tomotherapy,HT）与常规调强放疗（intensity modulated radiotherapy,IMRT）两种治疗计划中适形度指数（CI）、均匀性指数（HI）及唾液腺的剂量。［方法］ 收集2015～2016年行放疗的31例鼻咽癌患者,将定位数据及靶区勾画信息分别传输至Tomotherapy TPS工作站及Elekta Pinnacle TPS工作站进行调强计划设计,比较两个治疗计划的适形度指数、均匀性指数及唾液腺平均剂量、腮腺D50等指标。［结果］螺旋断层放疗计划与常规调强放疗计划比较,适形度指数（P<0.001）与均匀性指数（P<0.001）均有明显优势。腮腺的受照射剂量在常规调强放疗计划中更有优势（右侧P=0.01,左侧P=0.001）。腮腺D50在两组放疗计划差异无统计学意义（右侧P=0.671,左侧P=0.156）。螺旋断层放疗计划中颌下腺的平均剂量明显降低（右侧P=0.007,左侧P=0.007）。［结论］两组放疗计划均能满足临床要求,相较于传统调强放疗计划,螺旋断层放疗在鼻咽癌治疗中有更好的靶区剂量覆盖,剂量均匀性,在颌下腺保护优势明显。     

鼻咽癌螺旋断层放疗与常规加速器调强放疗的剂量学比较

目的 通过比较鼻咽癌螺旋断层放疗与常规直线加速器静态调强治疗计划,研究其剂量学特性.方法 选10例鼻咽癌患者的CT图像,统一勾画靶区及正常器官后,分别传输至螺旋断层放疗、常规调强放疗逆向调强计划系统.统一给予肿瘤靶区(pGTV、PTVnd)处方剂量70 Gy分33次,亚临床病灶区(PTV1)60 Gy分33次,预防照射区(PTV2)54 Gy分33次.正常器官限制体积与剂量为腮腺V35＜50%,脑干＜54 Gy,脊髓＜45 Gy,晶体＜9 Gy等.对两组数据进行配对t检验.结果 两组计划均有较好靶区处方剂量分布,但螺旋断层放疗组的均匀性好于常规调强放疗组;PTV1平均剂量(63.84 Gy)也显著低于常规调强放疗组(70.30 Gy);腮腺平均剂量较常规常规调强放疗组低5.3Gy,V30及V35显著低于常规调强放疗组;喉-气管-食管的最大剂量也较常规调强放疗组明显降低.结论 在鼻咽癌调强放疗中,螺旋断层放疗较常规直线加速器静态调强放疗有更好的剂量均匀性及更陡峭的剂量梯度,并可更好地保护正常器官.     

Total body irradiation: Significant dose sparing of lung tissue achievable by helical tomotherapy

PurposeTotal body irradiation (TBI) is an important procedure in the conditioning for bone marrow and hematopoietic stem cell transplantation. Doses up to 12 Gy are delivered in hyperfractionated regimes. TBI performed with helical Tomotherapy® (Accuray, Madison, Wisconsin, USA) is an alternative to conventional techniques to deliver dose in extended target volumes with the possibility of simultaneous dose sparing to organs at risk. In this study we focused on maximum dose reduction to the lungs in TBI using helical Tomotherapy®.Material and methodsForty treatment plans of patients who received TBI were calculated with TomoH® (Accuray, Madison, Wisconsin, USA, Version 2.0.4) with a dose of 12 Gy delivered in six equal fractions (2 × 2 Gy/day). Planning iterations necessary to accomplish ICRU 83 report should be less than 250. Treatment time should be practicable in daily routine (<60 min.). Besides the usual contouring of organs at risk special contouring was required for optimization processes which focused on maximum dose sparing in the central lung tissue. Dose constraints (D2, D98, D99) were predefined for target volumes (i.e. PTV TBI D99: 90% of prescribed dose). Homogeneity index <0.15 was defined for acceptability of the treatment plan.ResultsFor all patients acceptable treatment plan fulfilling the predefined constraints were achievable. An average time of 46 min is required for treatment. Thirty-four of forty patients fulfilled D2 in the PTV TBI. Four patients failed D2 due to a high BMI >28 (maximum dose 13.76 Gy = 114.7%). The D98 in the PTV TBI was not reached by 2/40 patients due to BMI > 31 (minimum dose 11.31 Gy = dose coverage of 94.2%). Also these two patients failed the homogeneity index <0.15. The mean lung dose over all patients of the right lung was 7.18 Gy (range 6.4–9.5 Gy). The left lung showed a median (D50) dose of 7.9 Gy (range 6.7–9.3 Gy). Central lung dose showed a mean dose (D50) of 5.16 Gy (range 4.02–7.29 Gy). The D80 of the central lung showed an average dose of 3.87 Gy.ConclusionsTotal body irradiation using helical Tomotherapy® can be delivered with maximum lung tissue sparing (<6 Gy) but without compromise in adjacent PTV TBI structures (i.e. ribs, heart). High conformity and homogeneity in extended radiation volumes can be reached with this technique in an acceptable planning and treatment time. Limitations may occurred in patients with high body mass index.     

螺旋断层放疗系统调强放疗验证

目的 通过螺旋断层放疗系统一系列调强放疗验证方法的研究,探讨其调强放疗的质量保证验证方法是否可行.方法 采用断层放疗计划系统进行调强放疗计划设计.为实现其剂量验证,笔者采用圆柱形固体水模体、0.056cm3 AISL电离室及EDR2胶片来实现对计划进行绝对剂量及相对剂量验证.将剂最胶片和电离室分别置于模体中,调用患者治疗计划束流数据对模体进行模拟照射;由此得出轴向截面上的等剂量分布和点绝对剂量,与计划模体的等剂量曲线及计算剂量结果进行比对.束流照射前,利用调强放疗兆伏特CT对摆位模体实行图像引导,与计划系统中模体千伏特CT图像进行配准比较,实现验证模体摆位准确性.结果 轴向测得注量分布与断层放疗计划系统计算结果相一致,测量点绝对剂量测量的结果与计划系统的计算误差均在±3%以内.测量模体的摆位误差基本可保持在1mm以内,但由于床从摆位虚拟中心到束流中心之间存在垂直下降2mm的系统误差,需要在模体或患者摆位中予以考虑.结论 3个月临床实践证明断层放疗的调强放疗所采用上述质量保证措施是切实可行的,建立了其质最保证体系.     

Intensity-modulated proton therapy versus helical tomotherapy in nasopharynx cancer: planning comparison and NTCP evaluation

PURPOSE: To compare intensity-modulated proton therapy (IMPT) and helical tomotherapy (HT) treatment plans for nasopharynx cancer using a simultaneous integrated boost approach. METHODS AND MATERIALS: The data from 6 patients who had previously been treated with HT were used. A three-beam IMPT technique was optimized in the Hyperion treatment planning system, simulating a "beam scanning" technique. HT was planned using the tomotherapy treatment planning system. Both techniques were optimized to simultaneously deliver 66 Gy in 30 fractions to planning target volume (PTV1; GTV and enlarged nodes) and 54 Gy to PTV2 subclinical, electively treated nodes. Normal tissue complication probability calculation was performed for the parotids and larynx. RESULTS: Very similar PTVs coverage and homogeneity of the target dose distribution for IMPT and HT were found. The conformity index was significantly lower for protons than for photons (1.19 vs. 1.42, respectively). The mean dose to the ipsilateral and contralateral parotid glands decreased by 6.4 Gy and 5.6 Gy, respectively, with IMPT. The volume of mucosa and esophagus receiving >/=20 Gy and >/=30 Gy with IMPT was significantly lower than with HT. The average volume of larynx receiving >/=50 Gy was significantly lower with HT, while for thyroid, it was comparable. The volume receiving >/=30, >/=20, and >/=10 Gy in total body volume decreased with IMPT by 14.5%, 19.4%, and 23.1%, respectively. The normal tissue complication probability for the parotid glands was significantly lower with IMPT for all sets of parameters; however, we also estimated an almost full recovery of the contralateral parotid with HT. The normal tissue complication probability for the larynx was not significantly different between the two irradiation techniques. CONCLUSION: Excellent target coverage, homogeneity within the PTVs, and sparing of the organs at risk were reached with both modalities. IMPT allows for better sparing of most organs at risk at medium-to-low doses.     

螺旋断层放疗与常规调强放疗在乳腺癌保乳术后同步推量中的剂量学比较

目的 比较乳腺癌保乳术后同步推量放疗中应用常规调强放疗（IMRT）及螺旋断层放疗（HT）剂量分布的差异,为HT在乳腺癌保乳术后的临床应用提供依据。方法 随机选择10例乳腺癌保乳术后患者,统一勾画计划靶区（PTV）与原发灶靶区（PGTV）并导入HT计划系统及瓦里安Eclipse计划系统,分别设计IMRT和HT计划,处方剂量均为PTV 50Gy／25f、PGTV 60Gy／25f,通过比较靶区剂量适形度、均匀性以及心肺受照剂量来评估IMRT与HT的优劣。结果 HT计划中靶区剂量的均匀性、适形度明显优于IMRT（P＜0.05）,患侧肺V5、V10、V20、V30及肺平均剂量均明显低于IMRT（P＜0.05）,但健侧肺V5增加;心脏剂量明显降低（P＜0.05）。结论 对于乳腺癌保乳术后同步推量放疗,HT与IMRT计划都可以满足临床剂量的要求,但HT计划在剂量学方面相对于IMRT计划具有优势,可以显著降低对正常器官的毒副作用。     

Intra-fraction motion of the prostate during treatment with helical tomotherapy

Background and purpose

To measure the geometric uncertainty resulting from intra-fraction motion and intra-observer image matching, for patients having image-guided prostate radiotherapy on TomoTherapy.

Material and methods

All patients had already been selected for prostate radiotherapy on TomoTherapy, with daily MV-CT imaging. The study involved performing an additional MV-CT image at the end of treatment, on 5 occasions during the course of 37 treatments. 54 patients were recruited to the study. A new formula was derived to calculate the PTV margin for intra-fraction motion.

Results

The mean values of the intra-fraction differences were 0.0 mm, 0.5 mm, 0.5 mm and 0.0° for LR, SI, AP and roll, respectively. The corresponding standard deviations were 1.1 mm, 0.8 mm, 0.8 mm and 0.6° for systematic uncertainties (Σ), 1.3 mm, 2.0 mm, 2.2 mm and 0.3° for random uncertainties (σ). This intra-fraction motion requires margins of 2.2 mm in LR, 2.1 mm in SI and 2.1 mm in AP directions. Inclusion of estimates of the effect of rotations and matching errors increases these margins to approximately 4 mm in LR and 5 mm in SI and AP directions.

Conclusions

A new margin recipe has been developed to calculate margins for intra-fraction motion. This recipe is applicable to any measurement technique that is based on the difference between images taken before and after treatment.     

Dose as a function of liver volume and planning target volume in helical tomotherapy, intensity-modulated radiation therapy-based stereotactic body radiation therapy for hepatic metastasis

PURPOSE: Stereotactic body radiation therapy (SBRT) has been shown to be an effective, well-tolerated treatment for local control of tumors metastatic to the liver. Multi-institutional Phase II trials are examining 60 Gy in 3 fractions delivered by linac-based, 3D-conformal IMRT. HiArt Helical TomoTherapy is a treatment unit that delivers co-planar helical IMRT that is capable of image-guided SBRT. We hypothesized that the maximum tolerable dose (MTD) delivered to a lesion by Helical TomoTherapy-based SBRT could be predicted based on the planning target volume (PTV) and liver volume. METHODS AND MATERIALS: To test this, we performed inverse treatment planning and analyzed the dosimetry for multiple hypothetical liver gross tumor volumes (GTV) with conventional PTV expansions. Inverse planning was carried out to find the maximum tolerated SBRT dose up to 60 Gy to be delivered in 3 fractions based on the dose constraint that 700 cc of normal liver would receive less than 15 Gy. RESULTS: Regression analysis indicated a linear relationship between the MTD, the PTV and the liver volume, supporting our hypothesis. A predictive equation was generated, which was found to have an accuracy of +/-3 Gy. In addition, dose constraints based on proximity to other normal tissues were tested. Inverse planning for PTVs located at varying distances from the heart, small bowel, and spinal cord revealed a predictable decrease in the MTD as the PTV increased in size or approached normal organs. CONCLUSIONS: These data provide a framework for predicting the likely MTD for patients considered for Helical TomoTherapy liver SBRT.     

Intensity-modulated radiation therapy (IMRT) dosimetry of the head and neck: a comparison of treatment plans using linear accelerator-based IMRT and helical tomotherapy

PURPOSE: To date, most intensity-modulated radiation therapy (IMRT) delivery has occurred using linear accelerators (linacs), although helical tomotherapy has become commercially available. To quantify the dosimetric difference, we compared linac-based and helical tomotherapy-based treatment plans for IMRT of the oropharynx. METHODS AND MATERIALS: We compared the dosimetry findings of 10 patients who had oropharyngeal carcinoma. Five patients each had cancers in the base of the tongue and tonsil. Each plan was independently optimized using either the CORVUS planning system (Nomos Corporation, Sewickly, PA), commissioned for a Varian 2300 CD linear accelerator (Varian Medical Systems, Palo Alto, CA) with 1-cm multileaf collimator leaves, or helical tomotherapy. The resulting treatment plans were evaluated by comparing the dose-volume histograms, equivalent uniform dose (EUD), dose uniformity, and normal tissue complication probabilities. RESULTS: Helical tomotherapy plans showed improvement of critical structure avoidance and target dose uniformity for all patients. The average equivalent uniform dose reduction for organs at risk (OARs) surrounding the base of tongue and the tonsil were 17.4% and 27.14% respectively. An 80% reduction in normal tissue complication probabilities for the parotid glands was observed in the tomotherapy plans relative to the linac-based plans. The standard deviation of the planning target volume dose was reduced by 71%. In our clinic, we use the combined dose-volume histograms for each class of plans as a reference goal for helical tomotherapy treatment planning optimization. CONCLUSIONS: Helical tomotherapy provides improved dose homogeneity and normal structure dose compared with linac-based IMRT in the treatment of oropharyngeal carcinoma resulting in a reduced risk for complications from focal hotspots within the planning target volume and for the adjacent parotid glands.     

螺旋断层治疗设备多叶准直器故障分析

目的 通过对螺旋断层治疗设备二进制气动多叶准直器故障现象及处理方法的分析,总结相关维修经验,达到准确判断故障部件,缩短停机时间,提高开机率的目的。方法 对螺旋断层治疗设备48个月的多叶准直器维修情况进行统计和分析,总结出多叶准直器常见的故障部件、故障原因及处理方法。结果 在48个月内,设备共出现多叶准直器故障20次,空气压缩机11次,位置验证板4次,叶片驱动器2次,叶片缓冲阀2次,叶片位置验证杆滑脱1次。多叶准直器故障与高压气体湿度有很大关系,设备出束时间对多叶准直器部分部件使用寿命也有很大影响。结论 螺旋断层治疗设备多叶准直器结构复杂,高强度工作增加了其故障率,高压气体湿度影响设备多叶准直器的正常运行,通过总结多叶准直器维修经验可初步判断故障原因,确定故障部件,达到缩短停机时间、提高开机率的目的。