Hi-Art tomotherapy加速器机房的辐射防护屏蔽评价

利用Hi-Art tomotherapy加速器辐射场的数据,来计算某医院同型加速器机房防护屏蔽厚度,并进行职业病危害辐射防护评价。由于螺旋断层加速器自屏蔽结构的存在,对于其机房屏蔽防护设计只需考虑散射线和漏射线。根据同型加速器辐射场特性,计算以加速器中心点为中心、每隔15o张角所对应机房墙体辐射防护屏蔽厚度,并对机房的设计值进行对比评价。结果表明,机房各屏蔽体所需防护屏蔽厚度最大值为与加速器中心点张角为15o处,东、南、西、北面墙体、顶棚、地板所需屏蔽厚度分别为1023、975、917、1460、1147和1189mm。经核实计算,除北侧防护墙设计厚度(1200mm)偏小外,其余均满足辐射防护屏蔽的要求。

TomoTherapy在全身放疗方面的应用

目的:本文报道一例TomoTherapy全身照射病例,介绍其调强计划方案,并分析其计划及验证结果。方法:由定位CT获取病人全身CT图像,在CMS医生工作站进行靶区和重要器官的勾画,传至TomoTherapy计划工作站进行计划设计。用ArcCheck三维半导体矩阵对计划实施验证,计划验证通过后在螺旋断层放疗设备上完成对病人的全身照射。结果:85%的靶区接受10Gy的处方剂量,靶区适形度CI和均匀指数HI分别为0.76和1.16。重要器官限制剂量达到临床要求,左晶体的最大剂量为3.4Gy,右晶体的最大剂量为4.3Gy,肺的平均剂量为5.5Gy,V5为45%,左肾的平均剂量为5Gy,右肾的平均剂量为5.7Gy。结论:TomoTherapy可以完成全身的照射,肺的剂量可以降得更低,减少毒副反应。为全身放疗提供了一种安全的方法。

TomoTherapy治疗计划剂量验证方法的研究

目的:建立一种可以对TomoTherapy治疗计划剂量进行验证的方法。方法:根据IAEA TRS 277号报告提供的水下吸收剂量测量计算的基本原理,采用待检的TomoTherapy辐射源以及在权威计量部门检定过的0.65 cc Farmer电离室,参照交叉校准的方法将标准量值传递给0.015 cc针尖电离室测量系统。之后采用固体水球型模体对治疗计划剂量进行检测和验证。结果:采用所建立的方法,剂量检测结果与治疗计划剂量相对偏差分别为1.35%、-2.30%、2.88%和0,皆小于±3%。结论:采用本研究所建立的方法可以与设备生产厂家的剂量治疗计划、检测结果进行比对、核查和控制,对于TomoTherapy项目的防护与应用质量检测具有重要的现实意义。

TomoTherapy HT系统长期剂量及能量稳定性监测

目的对Tomothepapy HT系统剂量及能量稳定性进行监测与评价,研究更换系统重要部件对剂量及能量稳定性的影响。方法用A1SL电离室,Tomo Electronmeter矩形固体水模体,参照美国医学物理学会TG-148号报告,对Tomotherapy HT系统质控规程中剂量输出、能量稳定性进行长期监测,并收集整理数据及分析结果。数据囊括了2011年3月到2017年3月所有日检剂量输出结果和月检静态模式下束流能量稳定性测量结果。结果 6年日检剂量输出平均绝对偏差是1.2%,更换固定靶前后绝对偏差值分别是1.30%、1.30%(P=0.986)。系统安装剂量伺服系统(Dose Servo System,DCS)前后偏差均值分别为1.30%、0.96%(P<0.001)。6年能量稳定性监测(ratio_P20/P10)平均绝对偏差是0.82%。更换固定靶前后平均偏差分别是0.82%、1.11%(P=0.248)。安装DCS前后绝对偏差是1.11%、0.64%(P=0.088)。结论 Tomo Therapy HT系统长期剂量和能量稳定性较好。固定靶与旋转靶对输出剂量和能量稳定性影响均无差异。剂量伺服系统的安装提高了输出剂量的稳定性而对能量稳定性无影响。

Tomotherapy计划系统中利用不同密度模体精确创建CT值密度曲线

目的通过研究不同密度模体创建的CT值密度曲线(Image Value to Density Table,IVDT)对剂量计算精度的影响,探讨如何在Tomotherapy计划系统中正确创建IVDT。方法分别用Gammex和CIRS两种密度模体创建立应的IVDT表,其中以是否含有空气密度点和在CT值-100~100 HU范围内是否包含除水以外的物质密度点分别创建IVDT表。调用不同IVDT表设计4组调强计划,同时生成7组剂量传输验证计划(Delivery Quality Assurance,DQA),测量上述11组调强计划的剂量偏差并进行配对t检验判断IVDT表是否符合要求。结果IVDT表中含有-100~100 HU计划组剂量偏差为1.55%±0.9%,与标准计划组剂量偏差比,有统计学差异(P<0.01),同理,不含空气密度点组的剂量偏差也有明显剂量学差异。7组DQA计划中调用CIRS IVDT Abdo(-100~100 HU)、Gammex IVDT Abdo(standard)的5组DQA计划剂量偏差,无统计学差异(P>0.05);调用CIRS IVDT Abdo(-100~100 HU)的2组DQA计划平均剂量偏差均为1.77%±1%,与对照组剂量偏差相比,有统计学差异。结论创建IVDT表时需要确保CT值在-100~100 HU范围内除水以外不含任何其他物质密度点,同时曲线中应该加入空气密度点,此两点对剂量计算精度影响较大。

TomoTherapy HD放射治疗系统的温度控制系统工作原理及故障分析

TomoTherapy HD放射治疗系统的产热部件包括加速管、磁控管、固态调制器、高压电源、微波循环控制器等[1-2]。这些部件只有在恒温条件下才能保证稳定工作。因此,温度控制系统(themal control system,TCS)是TomoTherapy HD放射治疗系统的重要组成部分,其稳定性直接影响着射频和束流部件的寿命及整机系统的故障率。本文首先介绍TomoTherapy HD放射治疗系统的TCS工作原理,然后对TCS的常见故障及维修过程进行总结,以供参考。

Clinical analysis of intracranial germinoma's craniospinal irradiation using helical tomotherapy

Objective： To evaluate the short-term clinical outcomes of intracranial germinoma patients treated with craniospinal irradiation （CSI） using helical tomotherapy （HT） system in our center. Methods： Twenty-three patients who were treated with CSI in our center from January 2008 to July 2012 were collected, with an average age of 20. M1 of the patients＇ CSI used the HT system. The total doses were 27-36 Gy/15-20 F （1.5-2 Gy per fraction）, and total local doses were 46-60 Gy/30-50 F （5 fractions per week）. M1 female patients for CSI were treated with left-right parallel-opposed field irradiation to protect their ovarian functions. Median follow-up time was 30.9 months （range, 5-67 months）. The SPSS19.0 software was used, and the overall survival （OS） was calculated using the Kaplan-Meier method. Results： Among 17 patients with assessable tumors, 9 cases （52.9%） were CR, 7 cases （41.2%） were PR, and 1 case （5.9%） was SD. Hematological toxicity was the severest side-effect occurred in the procedure of CSI. The level 1-4 acute leukopenia were 8.7%, 30.4%, 34.8% and 21.7% and the level 1-4 acute thrombopenia were 8.7%, 30.4%, 21.7% and 8.7%, respectively. Conclusions： For primary intracranial germinomas, HT can be used to implement CSI for simplifying radiotherapy procedures, improving radiotherapy accuracy, enhancing protection of peripheral organs at risk （ORA） and guaranteeing therapeutic effects. With the acceptable acute and long-term toxicity, CSI using HT in intracranial germinoma patients can be a safe and alternative mode.

Preliminary experience of helical tomotherapy for locally advanced pancreatic cancer

Radiotherapy for locally advanced pancreatic cancer is technically difficult and frequently associated with high-grade digestive toxicity.Helical tomotherapy(HT)is a new irradiation modality that combines megavoltage computed tomography imaging for patient positioning with intensity-modulated fan-beam radiotherapy.Its recent availability opens new fields of exploration for pancreatic radiotherapy as a result of its ability to tailor very well-defined dose distributions around the target volumes.Here,we report the use of HT in two patients with locally advanced pancreatic cancer. Doses to the bowel,kidneys and liver were reduced significantly,which allowed for excellent treatment tolerance without any high-grade adverse effects in either patient.

Helical tomotherapy and volumetric modulated arc therapy:New therapeutic arms in the breast cancer radiotherapy

AIM To analyse clinical and dosimetric results of helical tomotherapy(HT) and volumetric modulated arc therapy(VMAT) in complex adjuvant breast and nodes irradiation.METHODS Seventy-three patients were included(31 HT and 42 VMAT). Dose were 63.8 Gy(HT) and 63.2 Gy(VMAT) in the tumour bed, 52.2 Gy in the breast, 50.4 Gy in supraclavicular nodes(SCN) and internal mammary chain(IMC) with HT and 52.2 Gy and 49.3 Gy in IMC and SCN with VMAT in 29 fractions. Margins to particle tracking velocimetry were greater in the VMAT cohort(7 mm vs 5 mm).RESULTS For the HT cohort, the coverage of clinical target volumes was as follows: Tumour bed: 99.4% ± 2.4%; breast: 98.4% ± 4.3%; SCN: 99.5% ± 1.2%; IMC:96.5% ± 13.9%. For the VMAT cohort, the coverage was as follows: Tumour bed: 99.7% ± 0.5%, breast: 99.3% ± 0.7%; SCN: 99.6% ± 1.4%; IMC: 99.3% ± 3%. For ipsilateral lung, Dmean and V20 were 13.6 ± 1.2 Gy, 21.1% ± 5%(HT) and 13.6 ± 1.4 Gy, 20.1% ± 3.2%(VMAT). Dmean and V30 of the heart were 7.4 ± 1.4 Gy, 1% ± 1%(HT) and 10.3 ± 4.2 Gy, 2.5% ± 3.9%(VMAT). For controlateral breast Dmean was 3.6 ± 0.2 Gy(HT) and 4.6 ± 0.9 Gy(VMAT). Acute skin toxicity grade 3 was 5% in the two cohorts.CONCLUSION HT and VMAT in complex adjuvant breast irradiation allow a good coverage of target volumes with an acceptable acute tolerance. A longer follow-up is needed to assess the impact of low doses to healthy tissues.

Could helical tomotherapy do whole brain radiotherapy and radiosurgery?

Whole brain radiotherapy (WBRT) remains the standard management of breast cancer patients with brain metastases, allowing for symptomatic improvement and good local control in most patients. However, its results remain suboptimal in terms of both efficacy and toxicity. In highly selected breast cancer patients, stereotaxic radiotherapy demonstrates a very good local control with a low toxicity. With the purpose of improving the efficacy/toxicity ratio, we report the association of integrated boost with WBRT in a breast cancer patient with brain metastases. Two and a half years after completion of helical tomotherapy (HT), the patient experienced clinical and radiological complete remission of her brain disease. No delayed toxicity occurred and the patient kept her hair without need of radiosurgical procedure. The HT provided a high dosimetric homogeneity, delivering integrated radiation boosts, and avoiding critical structures involved in long-term neurological toxicity. Further assessment is required and recruitment of breast cancer patients into clinical trials is encouraged.

TomoTherapy Hi.Art放射治疗系统故障分析与排除

介绍了TomoTherapy Hi.Art放射治疗系统的基本组成及多叶光栅(multi-leaf collimator,MLC)的工作原理,详细分析了单片MLC故障、MLC初始化失败故障、MLC over travelled故障等产生的原因并给出了具体的排除方法,为同行维修类似故障提供参考。

Dosimetric Comparison of Craniospinal Axis Irradiation (CSI) Treatments Using Helical Tomotherapy, Smartarc^TM, and 3D Conventional Radiation Therapy

Purpose: Craniospinal axis irradiation (CSI) is a method of treating various central nervous system malignancies. The large target volume typically includes entire spinal cord and whole brain. Dosimetric comparison was performed between tomotherapy, volumetric modulated arc therapy (VMAT), and 3D conformal radiation therapy (3D-CRT) for CSI. Methods and Materials: Five (n = 5) CSI patients were planned using 3D-CRT, VMAT, and tomotherapy (normalized such that 95% of PTV received at least 23.4 Gy in 13 fractions). Plans were compared using PTV conformity number (CN) and homogeneity index (HI), normal tissue (NT) dose statistics, integral dose, and treatment time. Results: On average, tomotherapy plans showed higher CN (0.932 vs. 0.860 and 0.672 for SmartArc and 3D-CRT). In terms of HI, VMAT plans consistently showed better dose homogeneity (1.07 vs. 1.15 and 1.13 for tomotherapy and 3D-CRT). SmartArc delivered lower maximum dose for majority of NT, but higher mean dose. 3D-CRT plans delivered higher maximum dose but lower mean dose to NT. Conclusions: SmartArc treatments achieved better PTV homogeneity and reduced maximum dose to NT. Tomotherapy showed better target conformity, but 3D-CRT was shown to reduce mean dose to NT. Integral doses were similar between treatment modalities, but tomotherapy treatment times were much longer.

Systematic Analysis of the ArcCheck Diode Arrays for Tomotherapy Delivery Verification

Objective: The aim of this study was to evaluate the functional characteristics of ArcCheck? array detectors and the application for Tomotherapy IMRT plan verification. Method and Materials: The basic character of the ArcCheck applying on Tomotherapy system was tested. The diode testing procedures included the followings: The short term reproducibility, linearity, dose rate dependence, the profile measurement compared to ion chamber. The effect of insert on gamma passing rate was also studied. A total number of 602 Tomotherapy Delivery Quality Assurance (DQA) plans were retrospectively analyzed to obtain the action limit results with statistical significance evaluation. Results: The short term reproducibility, linearity, dose rate dependence, profile to ion chamber correlation and clinical application were all compared with satisfactory outcome with this device. If anterior diode points were properly calibrated with machine absolute output, then there was no significant difference between the ArcCheck phantom with and without insert on gamma passing rate. The average passing rate was 97.5% and the recommend action level was established at 92% based on the 602 patients’ clinical data with 95% confidence level criteria. Conclusion: This comprehensive study shows that ArcCheck is an accurate and efficient device for quality assurance of Tomotherapy with remarkable consistency of 3D volume analysis of arc therapy.

Evaluation of Deformable Image Registration and Dose Accumulation Using Histogram Matching Algorithm between kVCT and MVCT with Helical Tomotherapy

Purpose: To evaluate the accuracy of deformable image registration (DIR) between the planning kVCT (pCT) and the daily MVCT combined with the histogram matching (HM) algorithm, and evaluate the deformable dose accumulation using a suggested method for adaptive radiotherapy with Helical Tomotharapy (HT). Methods: For five prostate cancer patients (76 Gy/38 Fr) treated with HT in our institution, seven MVCT series (a total of 35 series) acquired weekly were investigated. First, to minimize the effect of different HU values between pCT and MVCT, this image-processing method adjusts HU values between pCT and MVCT images by using image cumulative histograms of HU values, generating an HM-MVCT. Then, the DIR of the pCT to the HM-MVCT was performed, generating a deformed pCT. Finally, deformable dose accumulation was performed toward the pCT image. Results: The accuracy of DIR was significantly improved by using the HM algorithm, compared with non-HM method for several structures (p &plusmn;0.05, 0.83 &plusmn;0.06, and 0.90 ± 0.04 for the CTV, rectum, and bladder, respectively, while that of the HM method was 0.81 &plusmn;0.06, 0.81 &plusmn;0.04, and 0.92 &plusmn;0.06, respectively. For the deformable dose accumulation, some difference was observed between the two methods, particularly for the small calculated regions, such as rectum V60 and V70. Conclusion: Adapting the HM method can improve the accuracy of DIR. Furthermore, dose calculation using the deformed pCT using HM methods can be an effective tool for adaptive radiotherapy.

Helical tomotherapy for duodenal adenocarcinoma in an elderly patient: A case report

To evaluate the efficacy and feasibility of external beam radiotherapy(EBRT) for duodenal adenocarcinoma in an 84-year-old female who underwent EBRT(2.2 Gy/d for a total dose of 46.2 Gy) using helical tomotherapy(HT). Toxicity was evaluated on the National Cancer Institute's common toxicity criteria(CTCAE 3.0). The patient completed the treatment without G3-G4 toxicity. After 22-mo follow-up, she is alive and well, in complete remission with no late side effects. HT seems to be feasible and effective for duodenal adenocarcinoma in old to very old patients.

Evaluation of Delivery Analysis to Detect Intrafractional Motion during Tomotherapy

The purpose of this study was to investigate the ability of a management system (Delivery Analysis: DA) to detect intrafractional motion during intensity-modulated radiation therapy (IMRT) in tomotherapy mode. Tomotherapy has made it possible to manage internal movements during treatment using software DA, which quantifies using the information of the passing dose obtained during the radiation treatment of patients. First, three treatment plans for the test were created (lumbar spine, prostate, and femur). Second, a pelvis phantom was moved in the X, Y, and Z directions, and a sinogram was acquired. The magnitudes of the movements were 3 mm, 5 mm, and 10 mm, respectively. Finally, the ability of DA to detect the motion was evaluated by comparing the sinogram obtained by moving the phantom with a reference sinogram obtained without movement. The sensitivity of DA could be detected with a shift amount of 3 mm (gamma analysis tolerance 0.3 mm/0.3%). The average gamma analysis of each direction at 0.3 mm/0.3% tolerance at each treatment site was 96.1% for the prostate, 93.5% for the lumbar spine, and 94.4% for the femur. Additionally, the average gamma pass rate results for the pelvic phantom in the X, Y, Z directions for a 10 mm shift were 96.2%, 96.3%, and 95.9%, respectively. DA is a powerful tool with high detection sensitivity and ability to detect body movement during treatment.

Variations in Tomotherapy Beam Outputs: A Multiple-Institutional Investigation

This study aimed to determine variations in tomotherapy beam outputs at multiple institutions. Measurements were obtained at 22 radiotherapy institutions. The first parameter was the absolute dose to water (Dfmsrw, Qmsr) in the machine-specific reference field (fmsr), which indicated a static field in the tomotherapy reference conditions defined by the International Atomic Energy Agency (IAEA) study group. The second measured parameter was the difference between the measured and the planed doses in the intensity modulated radiotherapy (IMRT) verification plans, which were created using a solid phantom by the vendor during tomotherapy apparatus installation to adjust the beam output. The IMRT verification plan error at each institution was defined as the systematic error of the beam output;Dfmsrw, Qmsr was subsequently modified. The Dfmsrw, Qmsr values of four institutions with a modified energy fluence per ideal open time (EFIOT) were lower than the values at other institutions. The mean value of all institutions except those four was 0.994 ± 0.013 Gy (range: 0.974 Gy, 1.017 Gy). When the Dfmsrw, Qmsr value was corrected by the IMRT verification error, this variation decreased. In addition, the mean IMRT verification errors in the TomoDirectTM and TomoHelicalTM modes with the TomoEDGETM mode were 1.2% ± 0.8% (range: -0.6%, 1.8%) and 0.2% ± 0.5% (range: -0.6%, 0.9%), respectively (p

Evaluation of Efficacy and Toxicity of Helical Tomotherapy in the Treatment of Patients with Nasal NK/T-Cell Lymphoma

Purpose: Nasal lymphoma created dosimetric challenges in radiotherapy due to the complex anatomical structures. This study was to evaluate the efficacy and toxicity of helical Tomotherapy (HT) in the treatment of nasal NK/T-cell lymphoma (NKTCL) patients. Methods and Materials: Between August 2008 and April 2013, a total of 25 NKTCL patients were treated with HT in our department;Among them, three patients have not received chemotherapy, one patient has received concurrent chemo-radiation with CHOP plus L-ASP, two patients have received the sequential chemotherapy regimen following irradiation, and all the others have received 1 - 2 cycles of induction chemotherapy followed by irradiation and then with sequential chemotherapy. CHOP-L with 1 - 7 cycles (median: 4 cycles) was utilized as the main chemotherapy regimen. As for HT, the gross tumor volume (GTV) received target doses (TD) ranging from 50 to 56 Gy (median: 50 Gy) at 2 - 2.78 Gy per fraction;and the clinical target volume (CTV) from 36 to 50 Gy (median: 40 Gy) at 1.6 - 2 Gy per fraction. Results: For those patients who had received irradiation, thirteen achieved complete remission (CR), four partial responses (PR);four had progressive disease (PD), two were lost to follow-up, two died within one month after irradiation and were not followed. In 21 patients with follow-up records, the overall response (CR + PR) was 81.0% with the 3-year survival rate of 87.2%, and the mean survival time was 52.8 months [95% confidence interval (CI): 45.2 - 60.4 months]. After radiotherapy the majority of patients had dry mouth and taste changes in varying degrees, and a small portion of patients had compromised hearing or vision functions. No brain injury symptoms occurred during radiation radiotherapy. Conclusions: As compared with conventional three-dimensional conformal radiotherapy (3D-CRT) and intensity modulated radiation therapy (IMRT) performed with HT, HT appears to have more favorable efficacy and toxicity profiles in the treatment of NKTCL. Further systematic and randomized clinical research is under investigation.

Dosimetric analysis of tomotherapy-based intensity-modulated radiotherapy with and without bone marrow sparing for the treatment of cervical cancer

Objective The aim of the study was to compare tomotherapy-based bone marrow-sparing intensity-mod- ulated radiotherapy （BMS-IMRT） with intensity-modulated radiotherapy （IMRT） without entering the pelvic bone marrow as a planning constraint in the treatment of cervical cancer after hysterectomy. Methods BMS-IMRT and IMRT plans were designed for a cohort of nine patients. The prescribed dose was 45 Gy in 1.8 Gy daily fractions, and 95% of the planned target volume received this dose. The doses were computed using a commercially available treatment planning system with the convolution/superposition algorithm. Plans were compared according to dose-volume histogram analysis in terms of planning target volume homogeneity and conformity indices （HI and CI） as well as organ at risk dose and volume parameters. Results BMS-IMRT had advantages over IMRT in terms of CI, but was equivalent to the latter in H1. V5, V10, V20, V30, and V40 of pelvic bone marrow in BMS-IMRT decreased by 0.06%, 17.33%, 22.19%, 13.85%, and 16.46%, respectively, compared with IMRT. Except for V30 of the small bowel and V30 and V40 of the bladder, no statistically significant differences were found between BMS-IMRT and IMRT in the small bowel, bladder, and rectum. Conclusion For cervical cancer patients receiving tomotherapy-based radiotherapy after hysterectomy, BMS-IMRT reduced pelvic bone marrow volume receiving low-dose radiation, and it may be conducive to preventing acute hematologic toxicity.

Clinical study on the changes of the tumor target volume and organs at risk in helical tomotherapy for nasopharyngeal carcinoma

Background Helical tomotherapy （HT） is a new image-guided intensity-modulated radiation therapy （IMRT）.The aim of this study was to evaluate the changes in the target volume and organs at risk （OARs） of patients with nasopharyngeal carcinoma （NPC） during helical tomotherapy.Methods Forty-three patients with NPC and treated via HT from March 2008 to January 2010 were reviewed retrospectively.Repeated CT scanning and plan adaptation were conducted at the 20th fraction during radiotherapy.The volumetric differences between the two scans were evaluated for nasopharyngeal tumor and retro- pharyngeal lymph nodes （GTVnx）,neck lymph nodes （GTVnd）,and parotid glands,as well as the axial diameter of the head.Results The median interval between the two scans was 25 days （23-28 days）.The volumetric decrease in GTVnx was 30.1% （median,29.8%） and in GTVnd 41.6% （median,45.9%）.The variation in the GTVnd volume was correlated with the weight loss of the patient.The volume of the left parotid gland decreased by 35.5% （median,33.4%） and of the right parotid glands decreased by 36.8% （median,33.5%）.The axial diameter of the head decreased by 9.39% （median,9.1%）.Conclusions The target volume and OARs of patients with NPC varied considerably during HT.These changes may have potential dosimetric effects on the target volume and/or OARs and influence the clinical outcome.Repeated CT scanning and replanning during the HT for NPC patients with a large target volume or an obvious weight loss are recommended.