Dosimetric Comparative Analysis of Volumetric Modulated Arc Therapy and Intensity-Modulated Radiation Therapy in Cervical Cancer

Objective:To carry out dosimetric comparison between volumetric modulated arc therapy(VMAT)and intensity-modulated radiation therapy(IMRT)in cervical cancer.Methods:50 postoperative cervical cancer patients were included in this study.The patients were admitted for treatment from January 2021 to January 2022.VMAT and IMRT plans were designed for each patient to analyze the dose distribution in the target area of the two treatment techniques.Results:Comparing the monitor unit for single treatment(638.21±116.21 MU)and time of single treatment(143.21±23.14 s)in the observation group and the monitor unit for single treatment(932.14±74.11 MU)and time of single treatment(223.14±17.26 s)in the control group,there was significant difference(P<0.05);there was also significant difference(P<0.05)between the normal tissue(bladder and rectum)of the observation group and that(bladder and rectum)of the control group.Conclusion:VMAT is more effective in cervical cancer,and it has a certain protective effect on normal tissues in patients and can reduce the radiation dose.

Dosimetry Comparison between Volumetric Modulated Arc Therapy with RapidArc and Fixed Field Dynamic IMRT for Local-Regionally Advanced Nasopharyngeal Carcinoma

Objective: A dosimetric study was performed to evaluate the performance of volumetric modulated arc radiotherapy with RapidArc on locally advanced nasopharyngeal carcinoma (NPC). Methods: The CT scan data sets of 20 patients of locally advanced NPC were selected randomly. The plans were managed using volumetric modulated arc with RapidArc and fixed nine-field coplanar dynamic intensity-modulated radiotherapy (IMRT) for these patients. The dosimetry of the planning target volumes (PTV), the organs at risk (OARs) and the healthy tissue were evaluated. The dose prescription was set to 70 Gy to the primary tumor and 60 Gy to the clinical target volumes (CTV) in 33 fractions. Each fraction applied daily, five fractions per week. The monitor unit (MU) values and the delivery time were scored to evaluate the expected treatment efficiency. Results: Both techniques had reached clinical treatment’s requirement. The mean dose (Dmean), maximum dose (Dmax) and minimum dose (Dmin) in RapidArc and fixed field IMRT for PTV were 68.4±0.6 Gy, 74.8±0.9 Gy and 56.8±1.1 Gy; and 67.6±0.6 Gy, 73.8±0.4 Gy and 57.5±0.6 Gy (P<0.05), respectively. Homogeneity index was 78.85±1.29 in RapidArc and 80.34±0.54 (P<0.05) in IMRT. The conformity index (CI: 95%) was 0.78±0.01 for both techniques (P>0.05). Compared to IMRT, RapidArc allowed a reduction of Dmean to the brain stem, mandible and optic nerves of 14.1% (P<0.05), 5.6% (P<0.05) and 12.2% (P<0.05), respectively. For the healthy tissue and the whole absorbed dose, Dmean of RapidArc was reduced by 3.6% (P<0.05), and 3.7% (P<0.05), respectively. The Dmean to the parotids, the spinal cord and the lens had no statistical difference among them. The mean MU values of RapidArc and IMRT were 550 and 1,379. The mean treatment time of RapidArc and IMRT was 165 s and 447 s. Compared to IMRT, the delivery time and the MU values of RapidArc were reduced by 63% and 60%, respectively. Conclusion: For locally advanced NPC, both RapidArc and IMRT reached the clinic requirement. The target volume coverage was similar for the different techniques. The RapidArc technique showed some improvements in OARs and other tissue sparing while using reduced MUs and delivery time.

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.

Partial and Full Arc Volumetric Modulated Arc Therapy in Lung Cancer Stereotactic Body Radiotherapy with Different Definitions of Internal Target Volume Based on 4D CT

Purpose: To investigate the feasibility of partial arc volumetric modulated arc therapy (VMAT) in lung cancer stereotactic body radiotherapy (SBRT), as well the volumetric and dosimetric effects of different internal target volume (ITV) definitions with 4D CT. Methods: Fourteen patients with primary and metastatic lung cancer underwent SBRT were enrolled. Full and partial arc VMAT plans were generated with four different ITVs: ITVall, ITVMIP, ITVAIP and ITV2phases, representing ITVs generated from all 10 respiratory phases, maximum intensity projection (MIP), average intensity projection (AIP), and 2 extreme respiratory phases. Volumetric and dosimetric differences, as well as MU and delivery time were investigated. Results: Partial arc VMAT irradiated more dose at 2 cm away from planning target volume (PTV) (P = 0.002), however, it achieved better protection on mean lung dose , lung V5, spinal cord, heart and esophagus compared with full arc VMAT. The average MU and delivery time of partial arc VMAT were 240 and 1.6 min less than those of full arc VMAT. There were no significant differences on target coverage and organ at risks (OARs) sparing among four ITVs. The average percent volume differences of ITVMIP, ITVAIP and ITV2phases to ITVall were 8.6%, 13.4%, and 25.2%, respectively. Conclusions: Although partial arc VMAT delivered more dose 2 cm out of PTV, it decreases the dose to lung, spinal cord, and esophagus, as well decreased the total MU and delivery time compared with full arc VMAT without sacrificing target coverage. Partial arc VMAT was feasible and more efficient for lung SBRT.

A prospective trial of volumetric intensity-modulated arc therapy vs conventional intensity modulated radiation therapy in advanced head and neck cancer

AIM: To prospectively compare volumetric intensitymodulated arc therapy(VMAT) and conventional intensity-modulated radiation therapy(IMRT) in coverage of planning target volumes and avoidance of multiple organs at risk(OARs) in patients undergoing definitive chemoradiotherapy for advanced(stage Ⅲ or Ⅳ)squamous cell cancer of the head and neck. METHODS: Computed tomography scans of 20 patients with advanced tumors of the larynx, naso-, oroand hypopharynx were prospectively planned using IMRT(7 field) and VMAT using two arcs. Calculated doses to planning target volume(PTV) and OAR were compared between IMRT and VMAT plans. Dose-volume histograms(DVH) were utilized to obtain calculated doses to PTV and OAR, including parotids, cochlea,spinal cord, brainstem, anterior tongue, pituitary and brachial plexus. DVH's for all structures were compared between IMRT and VMAT plans. In addition the planswere compared for dose conformity and homogeneity. The final treatment plan was chosen by the treating radiation oncologist. RESULTS: VMAT was chosen as the ultimate plan in 18 of 20 patients(90%) because the plans were thought to be otherwise clinically equivalent. The IMRT plan was chosen in 2 of 20 patients because the VMAT plan produced concentric irradiation of the cord which was not overcome even with an avoidance structure. For all patients, VMAT plans had a lower number of average monitor units on average(MU = 542.85) than IMRT plans(MU = 1612.58)(P < 0.001). Using the conformity index(CI), defined as the 95% isodose volume divided by the PTV, the IMRT plan was more conformal with a lower conformity index(CI = 1.61) than the VMAT plan(CI = 2.00)(P = 0.003). Dose homogeneity, as measured by average standard deviation of dose distribution over the PTV, was not different with VMAT(1.45 Gy) or IMRT(1.73 Gy)(P = 0.069). There were no differences in sparing organs at risk.CONCLUSION: In this prospective study, VMAT plans were chosen over IMRT 90% of the time. Compared to IMRT, VMAT plans used only one third of the MUs, had shorter treatment times, and similar sparing of OAR. Overall, VMAT provided similar dose homogeneity but less conformity in PTV irradiation compared to IMRT. This difference in conformity was not clinically significant.

A dosimetric evaluation of flattening filter-free volumetric modulated arc therapy for postoperative treatment of cervical cancer

Objective The aim of the study was to compare flattening filter-free(FFF) beams and conventional flattening filter(FF) beams in volumetric modulated arc therapy(VMAT) for cervical cancer after surgery, through a retrospective planning study.Methods VMAT plans of FFF beams and normal FF beams were designed for a cohort of 15 patients. The prescribed dose was 45 Gy to 1.8 Gy per fraction, and at least 95% of the planning target volume received this dose. Doses were computed with a commercially available treatment planning system using a Monte Carlo(MC) 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 organs at risk(OAR) dose and volume parameters. Results FFF-VMAT was similar to FF-VMAT in terms of CI, but inferior to FF-VMAT considering HI. No statistically differences were observed between FFF-VMAT and FF-VMAT in following organ at risks including pelvic bone marrow, small bowel, bladder, rectum, and normal tissue(NT)..Conclusion For patients with cervical cancer after hysterectomy, the FFF beam achieved target and OAR dose distribution similar to that of the FF beam. Reduction of beam-on time in cervical cancer is beneficial.

DICOM-RT Plan Complexity Verification for Volumetric Modulated Arc Therapy

The purpose of this study was to investigate the relationship between plan parameters verified with DICOM-RT and dosimetric results for volumetric modulated arc therapy (VMAT). We investigated three treatment locations: prostate cancer (ten cases), maxillary sinus cancer (four cases), and malignant pleura mesothelioma (four cases) with treatment plans generated by a MonacoTM treatment planning system (TPS), and delivered with an Elekta SynergyTM linear accelerator. We calculated plan parameters, including gantry and multileaf collimator (MLC) positions, Monitor Units (MU), and millimeters of MLC motion per degree of gantry rotation (mm/degree), and performed quality assurance (QA) with a DICOM-RT plan verification system. We measured the VMAT dose with a two-dimensional diode array detector. The average gamma passing rate with percent dose acceptance criteria and distance to agreement criteria of 2 mm and 2% (2 mm/2%) were 97.4%, 97.8% and 92.0% for prostate cancer, maxillary sinus cancer, and malignant pleural mesothelioma, respectively. The mean 95th percentile value for DICOM-calculated mm/degree was 4.0, 5.2, and 11.1 for prostate cancer, maxillary sinus cancer, and malignant pleural mesothelioma, respectively. The gamma passing rate showed a correlation with calculated mm/degree, with a coefficient of determination (R2) of 0.60. Higher calculated mm/degree values led to increased dosimetric errors. We conclude that dose distribution calculated by a TPS is more reliable at smaller mm/degree.

Benefits and Limitations of Volumetric Modulated Arc Therapy in Treating Bilateral Breast Cancer with Regional Lymph Nodes

Purpose: The study was performed comparing dosimetric characteristics of volumetric modulated arc therapy (VMAT) and field-in-field (FiF) techniques on a patient with synchronous bilateral breast carcinoma. Methods: The patients with bilateral breast cancer treatment were included in this study. A total dose of 40.05 Gy in 15 fractions was prescribed to the Planning Target Volume (PTV) of the whole bilateral breast cancer with the supraclavicular and infraclavicular nodes, with a complementary boost of 10 Gy in 4 fractions to the surgical bed (PTVboost). For both radiotherapy techniques, several VxGy parameters were analyzed for the PTVs, together with the Conformity index (CI), the Homogeneity index (HI) and the critical organs at risk (OARs), lungs and heart. Results: The patient was treated by the VMAT technique and the daily treatment time was less than 20 minutes with daily CBCT imaging. In the VMAT plan, the PTV 95% dose covered 38.89 ± 0.81 Gy, compared to 37.26 ± 1.02 Gy in the FiF technique. The VMAT plan improved the dose homogeneity index and lower dose in lung towards high dose region. Conclusion: The study demonstrates the viability of the VMAT technique in the treatment of bilateral breast cancer. The introduced single isocentric VMAT technique is fast to deliver and it increases the dose homogeneity of the target volume with some limitations. The treatment was well tolerated, without interruption of the treatment courses caused by treatment-related toxicities.

Dosimetric comparison of different multileaf collimators in volumetric modulated arc therapy for malignant pleural mesothelioma

Objective The aiom of the study was to compare the impacts of two types of multileaf collimators （MLC） [standard MLC with a width of 10 mm （sMLC） and micro-MLC with a width of 5 mm （mMLC）] on volumetric modulated arc therapy （VMAT） planning for malignant pleural mesothelioma. Methods VMAT for ten patients with inoperable malignant pleural mesotheliomas was retrospectively planned with the sMLC and mMLC. Histogram-based dose-volume parameters of the planning target vol- ume （PTV） [conformity index （CI） and homogeneous index （HI）] and organs-at-risk were compared for VMAT plans with sMLC （sMLC-VMAT） and mMLC （mMLC-VMAT）. Results The mMLC-VMAT plans were more efficient （average delivery time： 2.67±1.49 min） than the sMLC-VMAT plans （average delivery time： 4.21 ± 2.03 min; P 〈 0.05）. Moreover, compared to the sMLC plans, the mMLC plans demonstrated advantages in the dose coverage of the PTV （CI 0.75 ± 0.08 vs 0.73± 0.09; HI 1.09 ±0.02 vs 1.10± 0.02）, although the difference was not statistically significant （P 〉 0.05）. In addition, significant dose sparing in the fraction of the ipsilateral lung volume receiving 〉 20 Gy （V20; 54.72± 27.08 vs 58.52 ± 29.30） and 〉 30 Gy （V30; 42.74 ± 27.86 vs 46.86± 31.49） radiation, respectively, was observed for the mMLC plans （P 〈 0.05）. Conclusion Comparing sMLC-VMAT and mMLC-VMAT not only demonstrated the higher efficiency and better optimal target coverage of mMLC-VMAT, but also considerably improved the dose sparing of the ipsilateral lung in the VMAT plans for mali qnant pleural mesothelioma.

Predicting Delivery Error Using a DICOM-RT Plan for Volumetric Modulated Arc Therapy

The purpose of this study was to investigate the prediction of mechanical error using DICOM-RT plan parameters for volumetric modulated arc therapy (VMAT). We created plans for gantry rotation arcs of 360° and 180° (full-arc and half-arc VMAT) for six maxillary sinus cancer cases using a Monaco treatment planning system, and delivered the doses with a linear accelerator. We calculated DICOM-RT plan parameters, including gantry, multileaf collimator (MLC) positions and Monitor Units (MU). We compared plans with regard to gantry angle per MU (degrees/MU) and MLC travel per MU (mm/MU) for each segment. Calculated gantry angle/MLC position speeds and errors were evaluated by comparison with the log file. On average, the half-arc VMAT plan resulted in 47% and 35% fewer degrees/MU and mm/MU than the full-arc VMAT plan, respectively. The root mean square (r.m.s.) gantry and MLC speeds showed a linear relationship with calculated degrees/MU and mm/MU, with coefficients of determination (R2) of 0.86 and 0.72, respectively. The r.m.s. gantry angle and MLC position errors showed a linear relationship with calculated degrees/MU and mm/MU with R2 of 0.63 and 0.76, respectively. Deviations from plan parameters were related to mechanical error for VMAT, and provided quantitative information without the need for VMAT delivery. These parameters can be used in the selection of treatment planning.

双弧与对偶弧技术在胸中下段食管癌VMAT计划中的剂量学研究

目的:对比双弧(two arc,TA)和对偶弧(dual arc,DA)技术在胸中下段食管癌容积旋转调强放射治疗(volumetric modulated arc therapy,VMAT)中对计划靶区(planning target volume,PTV)与危及器官(organs at risk,OAR)剂量分布的影响。方法:回顾性选取2020年7月至2022年6月于某院接受放射治疗的10例胸中下段食管癌患者,使用RayStation 4.7.5.4计划系统的RayArc模块为每例患者分别制订TA和DA放射治疗计划,并对比2种计划的PTV D_(2)、D_(5)、D_(50)、D_(95)、D_(98)、均匀性指数(homogeneity index,HI)、适形性指数(conformity index,CI)、出束时间、总机器跳数,以及OAR肺V_(5)、V_(10)、V_(20)、V_(30)、Dmean,心脏V_(30)、V_(40)、Dmean和脊髓Dmax等剂量学参数。采用SPSS 22.0软件进行统计学分析。结果:2种计划PTV的CI、HI、D_(2)、D_(5)、D_(50)、D_(95)及出束时间比较,差异无统计学意义(P>0.05),而DA计划的D98及总机器跳数均高于TA计划,差异有统计学意义(P<0.05)。在OAR保护方面,DA计划的心脏V_(30)、V_(40)、D_(mean)较TA计划略有下降,但差异无统计学意义(P>0.05);肺V_(5)、V_(30)、D_(mean)及脊髓D_(max)较TA计划显著降低,差异有统计学意义(P<0.05)。结论:DA技术相比于TA技术在PTV剂量分布和OAR受量方面更具优势,选择DA技术制订食管癌VMAT计划,对患者治疗效果的提升有一定意义。

Volumetric modulation arc radiotherapy with flattening filter-free beams compared with conventional beams for nasopharyngeal carcinoma:a feasibility study

There is increasing interest in the clinical use of flattening filter-free(FFF) beams.In this study,we aimed to investigate the dosimetric characteristics of volumetric modulated arc radiotherapy(VMAT) with FFF beams for nasopharyngeal carcinoma(NPC).Ten NPC patients were randomly selected to undergo a RapidArc plan with either FFF beams(RA-FFF) or conventional beams(RA-C).The doses to the planning target volumes(PTVs),organs at risk(OARs),and normal tissues were compared.The technical delivery parameters for RapidArc plans were also assessed to compare the characteristics of FFF and conventional beams.Both techniques delivered adequate doses to PTVs.For PTVs,RA-C delivered lower maximum and mean doses and improved conformity and homogeneity compared with RA-FFF.Both techniques provided similar maximum doses to the optic nerves and lenses.For the brain stem,spinal cord,larynx,parotid glands,oral cavity,and skin,RA-FFF showed significant dose increases compared to RA-C.The dose to normal tissue was lower in RA-FFF.The monitor units(MUs) were(536 ± 46) MU for RA-FFF and(501± 25) MU for RA-C.The treatment duration did not significantly differbetween plans.Although both treatment plans could meet clinical needs,RA-C is dosimetrically superior to RA-FFF for NPC radiotherapy.

AAA和AXB算法在儿童髓母细胞瘤全脑全脊髓VMAT中的剂量学差异

目的:从剂量学角度分析各向异性算法(anisotropic analytical algorithm,AAA)和光子剂量(acuros external beam,AXB)算法在儿童髓母细胞瘤全脑全脊髓容积调强放射治疗(volumetric modulated arc therapy,VMAT)中的差异。方法:回顾性选取2015年2月至2022年8月于某院接受全脑全脊髓放射治疗(craniospinal irradiation,CSI)的35例髓母细胞瘤患儿,采用Varian Eclipse 15.6计划系统对35例患儿分别制订AAA计划和AXB计划,分为AAA计划组和AXB计划组。比较AXB计划组与AAA计划组对计划靶区(planning target volume,PTV)D_(mean)、D2、适形性指数(conformity index,CI)、均匀性指数(homogeneity index,HI)以及危及器官(organ at risk,OAR)双侧眼球、心脏、双侧肾脏、肝脏D_(mean),双侧肺V_(5)、V_(10)、V_(20)和D_(mean),双侧晶体、双侧视神经和小肠Dmax的剂量学影响。结果:AAA计划组的CI低于AXB计划组,差异有统计学意义(P<0.05);AAA计划组的HI、D2和D_(mean)均高于AXB计划组,差异有统计学意义(P<0.05)。AAA计划组的左、右眼D_(mean)均高于AXB计划组,差异有统计学意义(P<0.05);AAA计划组的左肺V_(5)、V_(10)、D_(mean)及右肺V_(5)、V_(10)、D_(mean)均高于AXB计划组,差异有统计学意义(P<0.05)。其他OAR剂量学参数在2个计划组间的差异无统计学意义(P>0.05)。结论:相较于AAA,在CSI计划中使用AXB算法能改善靶区剂量的均匀性,有效降低因放射治疗导致的副反应发生概率,推荐在儿童髓母细胞瘤全脑全脊髓VMAT中使用AXB算法代替AAA。

ArcCHECK Machine QA工具在医用直线加速器质量保证中的应用效果

目的探讨ArcCHECK Machine QA工具在医用直线加速器质量保证中的应用效果。方法利用ArcCHECK Machine QA工具和ArcCHECK体模对医用直线加速器进行性能测试,项目包括机架角度、机架旋转速度、机架旋转中心、多叶准直器和铅门位置的一致性、机架旋转出束时的平坦度和对称性,评估该工具在医用直线加速器质量保证中的应用效果。结果旋转模式下机架平均旋转速度为3.6 deg/s,最大偏差约0.5 deg/s;机架旋转等中心形成的平均半径为0.4 mm,多叶准直器与铅门的最大距离正、负差异平均值分别为0.7 mm、-0.7 mm;旋转出束模式下Y方向的平坦度为1.8%,Y方向的对称性为1.1%,X方向的对称性为4.3%。结论ArcCHECK Machine QA工具可用于医用直线加速器常规及容积调强出束性能质量保证。

Evaluation of 3D-CRT and VMAT Radiotherapy Plans for Left Breast Cancer with Regional Lymph Nodes Irradiation

Introduction: Radiation therapy after breast surgery is an integral part of the treatment of early breast cancer. The goal of radiation therapy is to achieve the best possible coverage of the planning target volume (PTV), while reducing the dose to organs at risk (OARs) which are normal tissues whose sensitivity to irradiation could cause damage that can lead to modification of the treatment plan. In the last decade, radiation oncologist started to use the Intensity Modulated Radiotherapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT) for irradiating the breast, in order to achieve better dose distribution and target dose to the PTV and OAR. The aim of this study is to compare 2 external radiotherapy techniques (VMAT vs 3D) for patients with node-positive left breast cancer. Patients and Methods: We randomly selected 10 cases of postoperative radiotherapy for breast cancer in our hospital. The patients are all female, the average age was 45.4 years old, and the primary lesions are left breast. The ANOVA test was used to compare the mean difference between subgroups, and the p value Results: Dose volume histogram (DVH) was used to analyze each evaluation dose of clinical target volume (CTV) and organs at risk (OARs). Compared to 3DCRT plans, VMAT provided more uniform coverage to the breast and regional lymph nodes. The max point dose for tVMAT was lower on average (106.4% for VMAT versus 109% for 3DCRT). OAR sparing was improved with tVMAT, with a lower average V17Gy for the left lung (27.91% for VMAT versus 30.04% for 3DCRT, p and lower for V28Gy (13.75% for VMAT versus 22.34% for 3DCRT, p = 0.01). We also found a lower V35Gy for the heart on VMAT plan (p = 0.02). On the contrary, dose of contralateral breast was lower in 3DCRT than VMAT (0.59 Gy vs 3.65 Gy, p = 0.00). Conclusion: The both types of plans can meet the clinical dosimetry demands of postoperative radiotherapy for left breast cancer. The VMAT plan has a better conformity, but 3CDRT can provide a lower dose to the contralateral organs (breast and lung) to avoid the risk of secondary cancers.

不同准直器角度组合对鼻咽癌VMAT计划质量的影响

目的:比较不同准直器角度组合对双弧VMAT鼻咽癌计划质量的影响,为临床选择提供参考依据。方法:本研究纳入10例鼻咽癌患者,设计不同准直器角度组合的双弧VMAT计划,用于对计划质量进行评价。结果:调整准直器角度能够提升靶区PGTV和GTVnd的适形指数,而对PTV的影响不显著。在重要器官方面,旋转准直器角度可以降低其中部分器官的最大受照剂量,但对平均受照剂量的影响则不明显。此外,调整准直器角度并不会导致MU和射束时间增加,执行效率与准直器角度为(0°,0°)的方案相当。综合考量计划质量,以准直器角度为(10°,350°)的放疗计划在总体质量得分方面表现最佳(SD:0.12),相较之下,准直器角度为(0°,0°)的得分最低(SD:1.2)。结论:不同准直器角度组合对鼻咽癌放疗计划的剂量分布有显著影响,但执行效率相当。在测试的准直器角度组合中,(10°,350°)总体计划质量表现最优,推荐临床使用。

光学体表监测系统引导VMAT技术在全身放射性治疗的应用

目的:建立光学体表监测系统(OSMS)引导容积旋转调强(VMAT)技术应用于全身放射性治疗(TBI)的基本流程,评价OSMS在放疗前分次间辅助摆位和放疗中分次内实时监测位置误差的精确性和有效性。方法:回顾分析造血干细胞移植前清髓接受OSMS引导VMAT-TBI的白血病患者15例,CT模拟定位,分别在头先进仰卧位(HFS)和脚先进仰卧位(FFS)采集全身图像数据,传输至治疗计划系统进行图像融合、多中心VMAT放疗计划设计及剂量验证,处方剂量为800 cGy/4F,一天两次。放疗前采用OSMS辅助摆位,CBCT进行位置验证,治疗中应用OSMS监控,通过分析离线日志文件获得OSMS实时监测的分次内误差。结果:HFS模式计划靶区的平均剂量和覆盖率分别为(905.4±19.0)cGy和(93.0±2.8)%;危及器官肺和肾脏平均剂量分别为(603.7±55.7)cGy和(600.4±49.6)cGy;晶体最大受照剂量为(393.9±58.9)cGy。FFS模式计划靶区的平均剂量和覆盖率分别为(888.5±58.9)cGy和(94.0±3.2)%;衔接处的最大剂量为(1148.9±72.9)cGy。单次放疗实施时间为(75.1±15.1)min。放疗前OSMS辅助摆位,CBCT三维矢量总偏差在平移方向和旋转方向分别为(2.71±1.96)mm和(0.91±0.90)°。在放疗中OSMS监测的分次内运动幅度平移方向三维矢量偏差为(1.95±1.88)mm,其中偏差在1 mm以内的在LNG、LAT和VRT方向上占比分别为57.5%、79.7%和62.1%;旋转方向三维矢量偏差为(0.76±0.72)°,其中偏差在1°以内在Rtn、Pitch和Roll方向上占比分别为93.1%、85.7%和94.3%。结论:VMAT简化TBI流程,同时提高靶区的覆盖率并较好地保护危及器官;采用OSMS可减少位移误差特别是旋转误差,为保障TBI精确实施和患者的安全性,有必要联合OSMS进行辅助摆位和分次内位置监测。

非小细胞肺癌同层双转移病灶SBRT-VMAT计划设计方式研究

目的:研究非小细胞肺癌同层双转移病灶立体定向放射治疗(stereotactic body radiation therapy,SBRT)时不同计划方式对肺的受量、机器跳数、适形性指数(conformity index,CI)及剂量梯度(gradient index,GI)的影响,以为此类患者治疗计划的设计提供参考。方法:选取非小细胞肺癌单侧同层双转移病灶患者共11例,采用容积旋转调强放疗(volumetric modulated arc therapy,VMAT)技术制订3种SBRT计划。根据4D-CT定位方式的最大投影图像勾画内靶区ITV1、ITV2,均匀外放3 mm得到计划靶区PTV1、PTV2,并将PTV1与PTV2相加得到PTV12。第1种计划方式以PTV1和PTV2靶区中心为治疗中心,制订2个单独计划plan-1与plan-2,合并为plan-sum后进行剂量评估;第2种计划方式分别以PTV1和PTV2中心为治疗中心,制订多中心的计划plan-D。第3种计划方式以PTV12的中心为治疗中心,制订单中心计划plan-S。将plan-sum的plan-1与plan-2分别归一到PTV1和PTV2 95%体积以满足处方剂量,将plan-S与plan-D归一到PTV12 95%体积以满足处方剂量。比较3种计划方式下肺的受量、机器跳数、CI及GI。采用SPSS 25.0软件进行统计学分析。结果:plan-S除V_(5)与plan-sum相比差异无统计学意义(P>0.05)外,V_(10)、V_(20)、V_(30)及平均剂量均低于plan-sum,差异有统计学意义(P<0.05);plan-D肺的受量和平均剂量均低于plan-sum,差异有统计学意义(P<0.05);plan-S与plan-D计划方式下肺的受量差异无统计学意义(P>0.05)。plan-sum的CI低于plan-S和plan-D,差异有统计学意义(P<0.05);plan-S与plan-D的CI差异无统计学意义(P>0.05)。plan-D的GI低于plan-S和plan-sum,差异有统计学意义(P<0.05);plan-S与plan-sum的GI差异无统计学意义(P>0.05)。plan-D和plan-sum的机器跳数高于plan-S,差异有统计学意义(P<0.05);plan-D与plan-sum的机器跳数差异无统计学意义(P>0.05)。结论:若患者身体状况支持长时间保持定位姿势,可以采用多中心的计划方式优化剂量分布和提高适形度;若患者身体状况较差,可以采用单中心的计划方式缩短治疗时间。

ArcCheck模体与胶片在鼻咽癌VMAT剂量验证中的比较研究

比较研究ArcCheck与胶片在鼻咽癌容积弧形调强(VMAT)验证中的应用,探讨ArcCheck在VMAT剂量验证中的可行性。随机选取5例鼻咽癌病人的VMAT治疗计划,分别用ArcCheck和胶片两种方法进行剂量验证,比较两种方法的验证结果。ArcCheck验证的平均通过率为96.74±2.60,胶片验证的平均通过率是95.95±1.17,利用统计分析t检验,结果表明ArcCheck和胶片验证两种结果在剂量学上没有明显差异。ArcCheck分析软件可以直接获取三维合成的剂量分布,且操作过程较胶片验证简单,可以更为便捷的进行VMAT剂量验证。

MONACO放疗计划系统VMAT计划照射野Arc数目对治疗计划影响的比较分析

目的评价MONACO治疗计划系统中VMAT计划照射野不同Arc数目对剂量分布、计划执行以及剂量验证通过率的影响。方法对接受治疗32例宫颈癌患者进行了回顾性分析,原执行治疗的计划为设置两个射野,每个射野1个Arc(1 Arc Per Beam,1APB),在原治疗计划轮廓勾画和参数约束相同的情况下,将照射野参数改为一个射野,每个射野2个Arc(2 Arc Per Beam,2APB)。计划在保证靶区100%体积接受95%处方剂量的标准下,对靶区的适形指数、均匀指数,危及器官的受照剂量,治疗计划的机器跳数和控制点数以及治疗计划的执行时间和剂量验证通过率进行评估。结果两种计划靶区的适形指数和均匀指数均值相近,危及器官受照剂量均值相近,差异无统计学意义(P>0.05)。与1APB计划相比,2APB计划的机器跳数和控制点数明显减少(P<0.05);在计划执行方面,2APB计划比1APB计划的实施时间明显缩短(P<0.05);而在两种计划的剂量输出验证方面,剂量通过率相近,差异无统计学意义(P>0.05)。结论两种治疗计划的剂量学差异相近,均能满足临床要求,但是2APB计划比1APB计划的执行效率有大幅提升,可在减少治疗机损耗的基础上提升了整体工作效率。