Dosimetric Comparison Between Helical Tomotherapy and Volumetric Modulated Arc Therapy in Patients With Malignant Pleural Mesothelioma

AimsTo carry out a dosimetric comparison and constraints feasibility proof of adjuvant radiotherapy through helical tomotherapy or volumetric modulated arc therapy (VMAT) for malignant pleural mesothelioma patients after pleurectomy/decortication.Materials and methodsRetrospective calculations were carried out on previously acquired simulations. A whole-pleura volume with 50.4 Gy in 28 fractions was prescribed, simulating a no residual tumour situation. Calculations were carried out using an anisotropic analytical algorithm with a 2.0 mm grid. Beam-on time, planning target volume (PTV) coverage, homogeneity index and organ at risk exposure were compared.ResultsSixteen patient plans were calculated per device. Constraints were met overall by both modalities. For helical tomotherapy and VMAT plans, median beam-on times were 13.8 (11.6–16.1) min and 6.4 (6.1–7.0) min; P = 0.006. The median left-sided radiotherapy PTV D₉₈ were 48.1 (48.0–48.8) Gy and 47.6 (46.5–48.3) Gy; P = 0.023. No significant difference for right-sided radiotherapy was found. PTV D₂ for left-sided radiotherapy was higher with VMAT (P = 0.014). For right-sided radiotherapy, helical tomotherapy showed higher doses (P = 0.039). No homogeneity index differences for left-sided radiotherapy (P = 1.00) and right-sided radiotherapy (P = 0.598) were seen. Significant organ at risk exposure differences were found on left-sided radiotherapy whole-lung V_20, as well as D₅₀ (both P = 0.008). Higher contralateral lung and ipsilateral kidney exposures were found with VMAT plans for both treatment sides.ConclusionAdjuvant radiotherapy after pleurectomy/decortication in malignant pleural mesothelioma patients, with a VMAT- or helical tomotherapy-based platform, is dosimetrically feasible. Lung sparing was mostly improved with helical tomotherapy. Technique selection must be carried out according to availability and clinical criteria.     

Adjuvant Radiotherapy after Breast Conserving Treatment for Breast Cancer:A Dosimetric Comparison between Volumetric Modulated Arc Therapy and Intensity Modulated Radiotherapy

Background: Radiotherapy is an important treatment of choice for breast cancer patients after breastconservingsurgery, and we compare the feasibility of using dual arc volumetric modulated arc therapy (VMAT2),single arc volumetric modulated arc therapy (VMAT1) and Multi-beam Intensity Modulated Radiotherapy(M-IMRT) on patients after breast-conserving surgery. Materials and Methods: Thirty patients with breastcancer (half right-sided and half left-sided) treated by conservative lumpectomy and requiring whole breastradiotherapy with tumor bed boost were planned with three different radiotherapy techniques: 1) VMAT1; 2)VMAT2; 3) M-IMRT. The distributions for the planning target volume (PTV) and organs at risk (OARs) werecompared. Dosimetries for all the techniques were compared. Results: All three techniques satisfied the doseconstraint well. VMAT2 showed no obvious difference in the homogeneity index (HI) and conformity index(CI) of the PTV with respect to M-IMRT and VMAT1. VMAT2 clearly improved the treatment efficiency andcan also decrease the mean dose and V5Gy of the contralateral lung. The mean dose and maximum dose of thespinal cord and contralateral breast were lower for VMAT2 than the other two techniques. The very low dosedistribution (V1Gy) of the contralateral breast also showed great reduction in VMAT2 compared with the othertwo techniques. For the ipsilateral lung of right-sided breast cancer, the mean dose was decreased significantlyin VMAT2 compared with VMAT1 and M-IMRT. The V20Gy and V30Gy of the ipsilateral lung of the leftsidedbreast cancer for VMAT2 showed obvious reduction compared with the other two techniques. The heartstatistics of VMAT2 also decreased considerably compared to VMAT1 and M-IMRT. Conclusions: Comparedto the other two techniques, the dual arc volumetric modulated arc therapy technique reduced radiation doseexposure to the organs at risk and maintained a reasonable target dose distribution.     

Single Arc Volumetric Modulated Arc Therapy of head and neck cancer

Background

The quality of Volumetric Modulated Arc Therapy (VMAT) plans is highly dependent on the performance of the optimization algorithm used. Recently new algorithms have become available which are capable of generating VMAT plans for Elekta accelerators. The VMAT algorithm in Pinnacle³® is named SmartArc and its capability to generate treatment plans for head and neck cancer was tested.

Methods

Twenty-five patients with oropharyngeal or hypopharyngeal carcinoma, previously treated with IMRT by means of Pinnacle³® and Elekta accelerators, were replanned with single arc VMAT. The VMAT planning objectives were to achieve clinical target coverage and sparing of the organs at risk (OAR). Comparison with the original clinically used IMRT was made by evaluating (1) dose-volume histograms (DVHs) for PTVs, (2) DVHs for OARs, (3) delivery time and monitor units (MU), and (4) treatment accuracy.

Results

Equivalent or superior target coverage and sparing of OARs were achieved with VMAT compared to IMRT. Volumes in the healthy tissues receiving between 17.3 Gy and 49.4 Gy were significantly reduced and the conformity (CI_95%) of the elective PTV was improved from 1.7 with IMRT to 1.6 with VMAT. Compared to step-and-shoot IMRT, VMAT reduced the number of MUs by 8.5% to 460 ± 63 MUs per fraction, and delivered on an Elekta Synergy accelerator, the treatment time was on average reduced by 35% to 241 ± 16 s. In Delta4® measurements of the VMAT treatments, 99.6 ± 0.5% of the detector points passed a 3 mm and 3% gamma criterion, identical to the results of IMRT.

Conclusions

The target coverages obtained in the IMRT and VMAT plans were found to be very similar. SmartArc generated single arc VMAT plans with equivalent or better target coverage and sparing of OARs compared to IMRT, while both delivery time and MUs were decreased. Very good dose accuracy results were obtained delivering the plans on an Elekta accelerator.     

Dosimetric Comparison between Acuros XB (AXB) and Anisotropic Analytical Algorithm (AAA) in Volumetric Modulated Arc Therapy

Aim: Dose calculation accuracy between Anisotropic Analytical Algorithm (AAA) and Acuros XB (AXB) for various megavoltage (MV) photon beams for both flattening filter (FF) and flattening filter free (FFF) beams and to validate the accuracy of these dose calculations using inhomogeneous phantom in volumetric modulated arc therapy (VMAT). Material and methods: A Cheese Phantom having 20 holes that can be filled with all virtual water plugs or set of density calibration plugs  was used for VMAT planning using two different algorithms using either single or double arc. Further phantom was used  irradiate plan in linear accelerator and the point doses measured using a 0.053 cc A1SL ionization chamber along electrometer . Different plans, cylindrical shape, C-shaped and donut targets were planned 6MV, 10MV, 6FFF MV and 10FFF MV beam energy. Result: The minimum average mean dose difference was 1.2% for PTV structures between AAA and AXB (p=0.02). Apart from these structures, the following density plugs have a more than 2% difference in maximum dose with statistical significance. (i) Solid water (MD=6.1%, p=0.016), (ii) Bone 200 (2.3%, p=0.029), (iii) CB_30% (MD=2.4%, p=0.050) and (iv) Cortical bone (MD=4.3%, p=0.018). In 6MV FFF and 10 MV FFF plans, the difference between AAA and AXB was not statistically significant (Fig 3). The Conformity index for the AAA less than that of AXB, in all energies and for all the PTVs. The CI was better in AXB than AAA, but the CI was not having much variation due to changes in beam energies, particularly for Cylinder shaped PTV. Conclusion: All combinations of beam energy AAA showed higher values in the maximum dose than the Acuros XB, except for the lung insert. Nonetheless, AAA showed a higher mean dose than the Acuros XB. Differences between these two algorithms for most of the beam energies are minimal.     

宫颈癌术后容积旋转调强治疗与三维适形调强放疗的临床研究

目的 评估宫颈癌术后盆腔放疗中开展容积旋转调强治疗(VMAT)与三维适形调强放疗(IMRT)的近期疗效及不良反应.方法 选取30例宫颈癌术后盆腔肿瘤床及淋巴引流区预防性放射治疗的患者,其中15例接受了VMAT治疗,15例患者接受了IMRT治疗.放疗采用每周5次,每日1次,每次1.8Gy.盆腔预防性放疗处方剂量为45Gy.根据RTOG评定指标评价放射治疗反应.结果 至末次随访时间,VMAT组4例复发,IMRT组5例复发.骨髓抑制反应VMAT组11例,IMRT组12例.全部患者中,均未出现3级及以上胃肠道早期反应及泌尿道早期反应.结论 对宫颈癌术后应用容积旋转调强技术及固定野调强技术进行照射治疗,两者在不良反应及复发率上无明显差别.     

Dosimetric Comparison and Feasibility of Simultaneous Integrated Boost (SIB) in Treatment of Malignant Gliomas Using Intensity Modulated Radiotherapy (IMRT) or Volumetric Modulated Arc Therapy (VMAT)

Objective: To evaluate the dosimetric parameters of Simultaneous Integrated Boost in the treatment of malignantgliomas and compare the SIB plans of VMAT and IMRT. Methodology: CT and MRI of 28 patients were used forgenerating SIB plans with VMAT and IMRT. A dose of 2Gy per fraction was prescribed to the CPTV and 2.4Gy tothe GPTV for a total of 25 fractions. The plans were accepted only if they met the set of planning objectives definedin the protocol. Results: We could achieve the planning objectives in all the SIB plans. Although GPTV coverage wasstatistically better in VMAT (98.67% vs 98.19% ;p=0.024) the difference is not clinically meaningful. The conformityindex for GPTV was higher in IMRT (0.83 vs 0.76; p=0.001). The coverage of CPTV was better in IMRT(97.88% vs 96.87%; p=0.021). But the conformity index of CPTVannulus was higher in VMAT (0.72 vs 0.67; p=0.01).There was no difference in homogeneity index of GPTV and CPTV annulus between the plans. The mean dose receivedby normal brain was higher in IMRT (28Gy vs 24.2Gy; p<0.001). Ipsilateral optic nerve has received lesser Dmax inIMRT (44.2Gy vs 46.95Gy; p=0.02). No difference was seen in Dmax of brainstem, optic chiasm, contralateral opticnerve. The treatment times and monitor units were significantly less in VMAT. Conclusion: SIB is dosimetricallyfeasible for hypofractionation in malignant gliomas using IMRT and VMAT. IMRT plans had better boost conformity,lower ipsilateral optic nerve and brainstem maximum doses compared to VMAT. Whereas, VMAT had better coverage,better overall PTV conformity, lower normal brain mean dose, lower monitor units and lesser treatment times. Althoughplanning of VMAT is cumbersome and time consuming, the advantage of reducing treatment time is beneficial tothe patients’ comfort and better managing of patient load in high volume centres.     

Dosimetric Comparison of Volumetric Modulated Arc Therapy and Intensity Modulated Radiation Therapy for Soft Tissue Sarcoma of the Extremities

PurposeRadiation therapy is a standard part of limb conserving therapy for extremity soft tissue sarcoma (STS) at high risk of recurrence. Toxic effects increase with radiation dose and volume of normal tissue irradiated. This study sought to compare dosimetry of volumetric modulated arc therapy (VMAT) with intensity modulated radiation therapy (IMRT) and to investigate the optimal planning technique.Methods and MaterialsTwenty patients with extremity STS who underwent preoperative radiation therapy (50 Gy in 25 fractions) between 2016 and 2020 at a specialised sarcoma center were included. The original treatment techniques were sliding window IMRT or 3-dimensional conformal. VMAT plans were retrospectively generated according to the original tumor and organ-at-risk constraints. Quality assurance was performed as per departmental protocol. Wilcoxon signed-rank test was used to compare dosimetric parameters (for planning target volume [PTV], in-field bone, and soft tissue structures), monitor units (MUs), and treatment time.ResultsMedian patient age was 65 years and the majority were male (n = 14, 70%). The most common subtype was undifferentiated pleomorphic sarcoma (n = 14, 70%), and most tumors were located on the thigh (n = 12, 60%). Median PTV was 1110 cm³ and median volume of in-field bone 236 cm³. VMAT plans had significantly lower average MU (480 vs 862 MU, P < .001) and overall treatment time (300 vs 153 seconds, P < .001). PTV coverage favored VMAT, with marginally higher mean, minimum, and maximum doses and higher conformity index. However, differences were not statistically significant. Dose to infield bone and soft tissue structures were similar or slightly lower with VMAT.ConclusionsIn extremity STS, VMAT plans demonstrated a favorable trend toward tumor coverage and dose conformity compared with IMRT along with significantly lower MUs and half the overall treatment time.     

Bilateral Regional Nodal Irradiation Using Volumetric Modulated Arc Therapy: Dosimetric Analysis and Feasibility

PurposeDosimetric and technical challenges often limit radiation therapy (RT) target coverage for patients with breast cancer who require bilateral breast/chest wall and regional nodal irradiation (RNI). We evaluated the feasibility of using volumetric modulated arc therapy (VMAT) to administer bilateral comprehensive RNI including the internal mammary nodes.Methods and MaterialsWe analyzed all patients treated at our institution with bilateral RNI using VMAT between 2017 and 2020. Medical records were reviewed to ascertain clinicopathologic features, radiotherapeutic parameters, and treatment-related adverse events.ResultsThe cohort was comprised of 12 patients who underwent VMAT for bilateral RNI, with a median follow-up time of 14.5 months. Median volume of the lung receiving 5 Gy (V₅) for the bilateral lungs was 96.1% (range, 84.5%-99.8%), and median volume of the lung receiving 20 Gy for each lung was 27.5% (range, 14.9%-38.1%). The cardiac mean dose was a median of 699 cGy (range, 527-1117 cGy). Five patients (41%) developed grade 1 cough/dyspnea, with one patient developing grade 3 dyspnea. Of note, 3 of these patients (60%) were current or former smokers. No patient received glucocorticoid therapy or required respiratory intervention, and none developed longer-term pulmonary complaints. A decline in ejection fraction occurred in one patient with a preexisting cardiac condition who also received anthracycline-based chemotherapy and trastuzumab. Only one patient experienced a locoregional recurrence with synchronous distant progression, and subsequently succumbed to the disease. No secondary cancers have been noted to date.ConclusionsVMAT appears to be a feasible and tolerable RT modality for patients with breast cancer who require bilateral comprehensive adjuvant RT with RNI to obtain excellent target coverage. No patients required medical intervention for pulmonary complaints despite a median bilateral V₅ approaching 100%, providing further evidence that V₅ is not predictive for complications.     

半弧和剪刀形切线弧技术在左侧乳腺癌根治术后放疗中的剂量学研究

摘 要：［目的］ 探讨半弧(semi-arc,SA)和剪刀形切线弧(tangent-arc,TA)技术在左侧乳腺癌根治术后放疗中的应用研究及剂量学优势。［方法］ 选取15例根治术后的左侧乳腺癌病例,在Monaco计划系统上分别采用SA和TA两组射野方式进行容积旋转调强（VMAT）计划设计,比较两组计划的靶区平均剂量、最大剂量、适形性指数（HI）、均匀性指数（CI）等,以及危及器官（OAR）的相关受照剂量体积参数。［结果］ 对于胸壁靶区PTV-T,TA射野组的Dmean和D2均小于SA组（P<0.05）,且HI和CI值优于SA组;对于锁骨淋巴结靶区PTV-N,虽然在HI和CI上两组差异无统计学意义,但Dmean、D98和D2均呈现TA相似文献   

双侧乳腺癌保乳术后单射野中心与双射野中心容积旋转调强放疗的剂量学比较

目的:研究双侧乳腺癌保乳术后采用单射野中心与双射野中心容积旋转调强放射治疗的剂量学差异.方法:随机选取2017年1月1日至2020年6月30日云南省肿瘤医院双侧乳腺癌保乳术后患者8例,女性,年龄33～65岁,中位年龄49岁.用Monaco计划系统为每例患者分别设计单射野中心和双射野中心放射治疗计划,双侧乳腺癌双靶区处方...     

COMPASS三维验证系统在食管癌容积旋转调强放疗中的应用

目的 探讨COMPASS三维验证系统在食管癌容积旋转调强剂量验证中的可行性。方法 选取37例食管癌初治患者在Oncentra计划系统上进行容积旋转调强（VMAT）计划设计,然后将治疗计划传送至COMPASS验证系统和加速器上。比较计划系统中的计算结果和COMPASS验证系统中实际测量结果之间的差异。分析靶区的平均剂量（Dmean）、95%体积受照射的剂量（D95）和γ值,危及器官比较双肺V20、V30剂量值。结果 计算结果和测量结果在靶区上的γ通过率均>92%,靶区D95的平均值偏差<3%,Dmean标准偏差平均值<1%。测量结果与计划结果中双肺V20、V30分别为（19.86±2.18）%、（20.03±2.21）%和（12.35±2.61）%、12.40±2.52）%,明显看出测量的结果V20、V30比计算结果小。结论 COMPASS三维验证系统能准确快速的分析出结果,保证食管癌治疗的安全。     

Dosimetric Comparison between Single and Dual Arc-Volumetric Modulated Arc Radiotherapy and Intensity Modulated Radiotherapy for Nasopharyngeal Carcinoma Using a Simultaneous Integrated Boost Technique

Backround: Plan quality and performance of dual arc (DA) volumetric modulated arc therapy (VMAT) , single arc (SA) VMAT and nine field (9F) intensity modulated radiotherapy were compared using a simultaneous integrated boost (SIB) technique. Methods: Twelve patients treated in Elekta Synergy Platform (mlci2) by 9F-IMRT were replanned with SA/DA-VMAT using a CMS Monaco Treatment Planning System (TPS) with Monte Carlo simulation. Target delineation was conducted as per Radiation Therapy Oncology Protocols (RTOG0225 and 0615). A 70Gy dose prescribed to PTV70 and 61Gy to PTV61 in 33 fractions was applied for the SIB technique. The conformity index (CI) and homogeneity index (HI) for targets and the mean dose and maximum dose for OAR’s, treatment delivery time (min), monitor units (MUs) per fraction, normal tissue integral dose and patient specific quality assurance were analysed. Results: Acceptable target coverage was achieved for PTV70 and PTV61 with all the planning techniques. No significant differences were observed except for D98 (PTV61), CI(PTV70) and HI(PTV61). Maximum dose (Dmax) to the spinal cord was lower in DA-VMAT than 9F-IMRT (p=0.002) and SA-VMAT (p=0.001). D50 (%) of parotid glands was better controlled by 9F-IMRT (p=0.001) and DA-VMAT (p=0.001) than SA-VMAT. A lower mean dose to the larynx was achieved with 9F-IMRT (P=0.001) and DA-VMAT (p=0.001) than with SA-VMAT. DA-VMAT achieved higher CI of PTV70 (P= 0.005) than SA-VMAT. For PTV61, DA-VMAT (P=0.001) and 9F-IMRT (P=0.001) achieved better HI than SA-VMAT. The average treatment delivery times were 7.67mins, 3.35 mins, 4.65 mins for 9F- IMRT, SA-VMAT and DA-VMAT, respectively. No significant difference were observed in MU/fr (p=0.9) and NTID (P=0.90) and the patient quality assurance pass rates were >95% (gamma analysis Ґ3mm, 3%). Conclusion: DA-VMAT showed better conformity over target dose and spared the OARs better or equal to IMRT. SA-VMAT could not spare the OARs well. DA-VMAT offered shorter delivery time than IMRT without compromising the plan quality.