A robust volumetric arc therapy planning approach for breast cancer involving the axillary nodes

We quantify the robustness of a proposed volumetric-modulated arc therapy (VMAT) planning and treatment technique for radiotherapy of breast cancer involving the axillary nodes. The proposed VMAT technique is expected to be more robust to breast shape changes and setup errors, yet maintain the improved conformity of VMAT compared to our current standard technique that uses tangential intensity-modulated radiation therapy (IMRT) fields. Treatment plans were created for 10 patients. To account for anatomical variation, planning was carried out on a computed tomography (CT) with an expanded breast, followed by segment weight optimization (SWO) on the original planning CT (VMAT + SWO). For comparison purposes, tangential field IMRT plans and conventional VMAT (cVMAT) plans were also created. Anatomical changes (expansion and contraction of the breast) and setup errors were simulated to quantify changes in target coverage, target maximum, and organ-at-risk (OAR) doses. Finally, robustness was assessed by calculating the actual delivered dose for each fraction using cone-beam CT images acquired during treatment. Target coverage of VMAT + SWO was shown to be significantly more robust compared to cVMAT technique, against anatomical variations and setup errors. Sensitivity of the clinical target volume (CTV) V95% is ?5%/cm of expansion for the proposed technique, which is identical to the IMRT technique and much lower than the ?22%/cm for cVMAT. Results are similar for setup errors. OAR doses are mostly insensitive to anatomical variations and the OAR sensitivity to setup variations does not depend on the planning technique. The results are confirmed by dose distributions recalculated on cone-beam CT, showing that for VMAT + SWO the CTV V95% remains within 2.5% of the planned value, whereas it deviates by up to 7% for cVMAT. A practical VMAT planning technique is developed, which is robust to daily anatomical variations and setup errors.     

宫颈癌术后放疗中自动计划与人工计划的剂量学比较

目的 比较容积弧形调强（VMAT）人工计划与自动计划的剂量学参数,评估自动计划在临床宫颈癌术后放疗应用的可行性以及剂量学特点。方法 选取23例宫颈癌术后病例,其中Ⅱ_A期8例,Ⅱ_B期15例,使用Pinnacle³放射治疗计划系统分别设计人工VMAT和自动VMAT计划。比较两种计划靶区的D_mean、D₉₅、适形指数（CI）、均匀性指数（HI）、危及器官（OAR）的剂量体积直方图（DVH）、平均优化时间、调试次数以及机器跳数（MU）。结果 自动计划得到的靶区D_mean、CI以及HI均优于人工计划（t=4.65~14.92,P<0.05）,而D₉₅无明显差异（P>0.05）;自动计划得到的OAR各参数均优于人工计划（t=3.30~14.42,P<0.05）;自动计划明显减少了计划的平均优化时间（72 min,t=3.85,P<0.05）和调试次数（2次,t=5.41,P<0.05）;自动计划和人工计划的平均机器跳数分别为（819±53）和（638±41） MUs,自动计划跳数增加了181 MUs。结论 使用Pinnacle³自动设计的宫颈癌术后VMAT计划具有临床可行性,并且自动VMAT计划与人工VMAT计划相比提高了计划质量,减少了计划设计时间、人为因素对于计划质量的影响。     

呼吸幅度对旋转容积调强剂量分布的影响研究

目的 研究呼吸幅度对旋转容积调强放疗(VMAT)剂量分布的影响。方法 采用呼吸运动模拟模体(QUASAR)模拟人体头脚方向的一维呼吸运动,二维电离室矩阵采集不同呼吸幅度等中心层面的剂量分布。通过Verisoft软件及绝对剂量分析,分析采集数据与计划数据比较的剂量分布、等中心绝对剂量百分误差和射野通过率。结果 呼吸运动对靶区等中心点剂量影响小于剂量允许误差5%(t=-22.614~-10.756,P<0.05),使靶区边缘剂量偏高、靶区内热点少、冷点多,且随着呼吸幅度的增大,对靶区整体剂量分布影响越大。6、8、10 mm整个射野γ通过率与静态相比差异有统计学意义(t=3.095、8.685、14.096,P<0.05)。8、10 mm靶区内射野通过率与静态相比差异有统计学意义(t=6.081、9.841,P<0.05)。结论 呼吸运动可导致VMAT剂量传输误差,且误差随靶区运动幅度的增加而升高,且呼吸运动方向靶区边缘的正常组织实际治疗受照剂量高于计划评价。     

Physical dosimetry of volumetric modulated arc therapy (VMAT) using EPID and 2D array for quality assurance

Outline

To address the correspondence of measured and predicted doses for different malignant tumours utilizing various gamma criteria and QA for confirmation of VMAT with an EPID and 2D array detector.

VMAT与IMRT在局部晚期宫颈癌放疗中的剂量学差异

目的 比较分析容积弧形调强放射治疗（VMAT）与固定野调强适形放射治疗（IMRT） 在局部晚期宫颈癌延伸野放疗计划中的剂量学差异。 方法 回顾性分析2019年1月至2021年12月南京医科大学附属淮安第一医院收治的20例宫颈癌患者的临床资料,患者年龄（56.3±9.1）岁,范围39~78岁,均行CT扫描,对所有患者进行计划靶区（PTV）、转移淋巴结计划靶区（PGTVnd）以及膀胱、直肠、双侧股骨头、 肝、双肾、小肠、脊髓等危及器官的勾画。按照随机数字表法将患者分为IMRT 组和VMAT组,每组10例,分别进行IMRT 和VMAT的放疗计划;其中IMRT 组患者年龄（54.1±7.1）岁,VMAT组患者年龄（58.1±10.8）岁。比较2组患者靶区的剂量参数、危及器官的剂量参数以及机器总跳数、有效治疗时间。计量资料的组间比较采用t检验。 结果 在PTV中,VMAT组的适形指数（0.81±0.03）高于IMRT组（0.79±0.23）,且差异有统计学意义（t=−2.190,P=0.035）。在PGTVnd中,VMAT组的均匀性指数（0.06±0.01）低于IMRT组（0.07±0.01）,且差异有统计学意义（t=−2.315,P=0.026）。在膀胱受照射剂量中,VMAT组的V20 Gy（Vx Gy表示接受≥x Gy照射的体积占总体积的百分比）为（92.64±2.29）%,低于IMRT组的（93.98±1.47）%,且差异有统计学意义（t=2.220,P=0.032）。在直肠受照射剂量中,VMAT组的V20 Gy为（92.20±2.21）%,低于IMRT组的（93.68±1.88）%,且差异有统计学意义（t=2.282,P=0.028）。在肝受照射剂量中,VMAT组的V10 Gy、V20 Gy分别为（7.73±0.39）%、（5.14±0.68）%,均低于IMRT组的V10 Gy[（7.93±0.10）%]、V20 Gy[（5.51±0.16）%],且差异均有统计学意义（t=2.372、2.367,P=0.023、0.023）。在小肠受照射剂量中,VMAT组的V20 Gy、V30 Gy、V40 Gy和平均剂量（Dmean）分别为（77.67±4.64）%、（39.21±1.10）%、（18.35±3.05）%和（30.36±3.46） Gy,均低于IMRT组的V20 Gy[（80.24±1.05）%]、V30 Gy[（42.34±6.00）%]、V40 Gy[（22.34±6.01）%]和Dmean[（34.23±6.71） Gy],且差异均有统计学意义（t=2.228~2.628,均P<0.05）。在脊髓受照射剂量中,VMAT组的V20 Gy和Dmean分别为（38.81±2.33）%和（11.46±4.26） Gy,均低于IMRT组的V20 Gy[（42.88±6.19）%]和Dmean[（17.97±7.40） Gy],且差异均有统计学意义（t=2.752、3.410,P=0.009、0.002）。在左肾受照射剂量中,VMAT组的V20 Gy和Dmean分别为（11.67±2.36）%和（10.02±2.19） Gy,均低于IMRT组的V20 Gy[（15.56±7.50）%]和Dmean[（14.06±7.29） Gy],且差异均有统计学意义（t=2.216、2.375,P=0.033、0.023）。在右肾受照射剂量中,VMAT组的V20 Gy和Dmean分别为（11.72±2.31）%和（10.07±2.15） Gy,均低于IMRT组的V20 Gy[（16.67±6.92）%]和Dmean[（13.92±7.17） Gy],且差异均有统计学意义（t=3.030、2.295,P=0.004、0.027）。在左股骨头受照射剂量中,VMAT组的 V10 Gy、V20 Gy、V30 Gy、V40 Gy、V50 Gy及Dmean均低于IMRT组[（74.77±2.33）%对（78.51±7.46）%、（34.37±2.74）%对（38.91±7.20）%、（14.77±2.33）%对（18.51±7.46）%、（2.99±1.03）%对（4.98±3.73）%、（0.48±0.22）%对（0.99±0.65）%、（34.32±2.79） Gy对（38.41±6.67） Gy],且差异均有统计学意义（t=2.147~3.359,均P<0.05）。在右股骨头受照射剂量中,VMAT组的 V50 Gy为（0.02±0.01）%,低于 IMRT组的V50 Gy[0.03±0.01%],且差异有统计学意义（t=2.997,P=0.005）。VMAT组的机器总跳数为（536.16±42.37）,低于IMRT组的（614.44±59.44）,且差异有统计学意义（t=−5.362,P<0.001）;VMAT组的有效治疗时间为（152.23±0.31） min,短于IMRT组的（453.88±9.94） min,且差异有统计学意义（t=−151.708,P<0.001）。 结论 对于局部晚期宫颈癌,VMAT计划的适形度及均匀性较好,更能保护危及器官,且可减少机器跳数,缩短治疗时间。     

Monaco与Pinnacle计划系统在肺癌容积旋转调强计划中的比较

目的 比较Monaco和Pinnacle 2套计划系统设计的肺癌容积旋转调强(VMAT)计划的计划质量、治疗效率和剂量验证精度.方法 选取20例肺癌病例,其中左肺癌10例,右肺癌10例,分别利用Monaco 3.0和Pinnacle 9.2两套计划系统设计VMAT计划,比较2种计划的靶区适形度、均匀性、最大剂量(D_max)、平均剂量(D_mean)与最小剂量(D_min)及危及器官的受照剂量;比较治疗计划执行时间、机器跳数和剂量验证的准确性.结果 除PTV的D_min外,Monaco计划靶区的其他各项剂量学指标都明显优于Pinnacle(t=5.927~12.034,P<0.05);2种计划除患侧肺V₁₀、全肺V₅外,Monaco计划肺的其他剂量学指标都差于Pinnacle(t=3.545~7.485,P<0.05),Monaco计划对心脏的保护明显优于Pinnacle(t=2.836~4.011,P<0.05),但较差的是Monaco计划执行时间(t=9.780,P<0.05)和MU数量(t=5.304,P<0.05).Monaco计划的Delta⁴验证结果优于Pinnacle(t=4.937,P<0.05).结论 对于肺癌的VMAT计划,Monaco与 Pinnacle两套计划系统都能满足临床应用要求;Pinnacle在肺的保护与计划执行方面有明显的优势,Monaco在靶区剂量分布和心脏的保护,以及剂量验证方面具有优势.     

Effect of arc length on skin dose from hypofractionated volumetric modulated arc radiotherapy treatments of the lung and spine

Due to large doses per fraction, stereotactic ablative radiotherapy of lung or spine can lead to skin tissue toxicity, the amount of which depends on a variety of factors such as target location, beam geometry, and immobilization. The effect of arc length on spreading out entrance and exit doses and the corresponding predictions of skin reactions has not yet been studied for stereotactic body radiotherapy volumetric modulated arc therapy (VMAT) treatments. 58 clinically relevant VMAT stereotactic body radiotherapy spine and lung plans were created for an anthropomorphic phantom utilizing a range of target locations, beam geometries and arc lengths. Skin dose was assessed by considering the National Cancer Institute skin reaction grades adjusted for 3 fraction treatments. While the skin volumes predicted to exhibit low grade reactions decreased with arc length, high grade reactions were found to increase at smaller arcs as well as at full arcs where a superposition of entrance and exit doses would occur. It is possible for skin dose to be effectively optimized by choice of arc length (within clinically relevant boundaries) and thus minimize the skin reaction. High skin doses are often attributed to effects arising from the distance between the planning target volume and patient surface but this study has demonstrated that VMAT arc length is of equal importance. Understanding this relationship will assist in minimizing skin reactions through modification of plan parameters and will provide clinicians more information for patient selection.     

A volumetric approach to path-length measurements is essential when treating radiotherapy with modulated beams

The established dosimetric benefits of intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy have lead to their increased use in prostate radiotherapy. Complimenting these techniques, volumetric image guidance has supported increased positional accuracy. In addition, 3-dimensional image guidance has also allowed for assessment of potential dosimetric variation that can be attributed to a deformation of either internal or external structures, such as rectal distension or body contour. Compounding these issues is the variation of tissue density through which the new field position passes and also the variation of dose across a modulated beam. Despite the growing level of interest in this area, there are only a limited number of articles that examine the effect of a variation in beam path length, particularly across a modulated field. IMRT and volumetric-modulated radiation therapy (VMAT) fields are dynamic in nature, and the dose gradient within these fields is variable. Assessment of variation of path length away from the beam׳s central axis and across the entire field is vital where there is considerable variation of dose within the field, such as IMRT and VMAT. In these cases, reliance on the traditional central axis to focus skin distances is no longer appropriate. This article discusses these more subtle challenges that may have a significant clinical effect if left unrecognized and undervalued.     

宫颈癌术后容积旋转调强放疗与5野调强放疗计划的剂量学比较

目的比较宫颈癌术后容积旋转调强放疗（VMAT）与5野调强放疗（5F-IMRT）计划的剂量学差异,并在危及器官保护方面进行分析。方法选择10例宫颈癌术后放疗的5F-IMRT计划,按相同的剂量限制对每例患者行单弧VMAT和双弧VMAT计划设计,比较3种计划的靶区剂量、适形度指数、均匀性指数、危及器官剂量及加速器跳数。组间比较采用单因素方差分析检验,组间两两比较采用LSD检验。结果单弧VMAT和双弧VMAT均能满足靶区处方剂量的要求,在靶区最大剂量、平均剂量、适形度指数和均匀性指数上,双弧VMAT与5F-IMRT计划相当,单弧VMAT计划最差,差异有统计学意义（F=24.102、13.710、5.919、11.045,均P < 0.05）;靶区最小剂量比较,3种计划差异无统计学意义（F=3.323,P>0.05）。单弧VMAT和双弧VMAT计划的加速器跳数明显少于5F-IMRT计划,差异有统计学意义（F=295.138,P < 0.05）。对于小肠、直肠和膀胱的参数最大剂量,双弧VMAT与5F-IMRT计划相当,单弧VMAT计划最差,差异有统计学意义（F=16.069、7.521、13.966,均P < 0.05）。对于膀胱的参数V20、V30和V40（V表示受照剂量体积百分比）,5F-IMRT优于单弧VMAT和双弧VMAT,差异有统计学意义（F=5.142、20.095、7.387,均P < 0.05）。对于左股骨头参数V20和V30,单弧和双弧VMAT优于5F-IMRT,差异有统计学意义（F=3.717、16.040,均P < 0.05）。对于右股骨头参数V30和V40,单弧和双弧VMAT优于5F-IMRT,差异有统计学意义（F=10.873、7.791,均P < 0.05）。结论宫颈癌术后放疗,双弧VMAT计划在靶区剂量学参数上与5F-IMRT计划相当,单弧VMAT计划较差。在危及器官保护方面,3种计划各有优势,但VMAT计划的加速器跳数明显减少,可以提高治疗效率,值得进一步研究。     

快速旋转调强与五野动态调强在乳腺癌 保乳术后放疗中的剂量学比较

目的 比较乳腺癌保乳术后RapidArc计划与五野动态调强(5F-IMRT)计划的剂量学差异。方法 选择8例左侧乳腺癌保乳术后女性患者,处方剂量为50 Gy/ 25次。分别设计RapidArc计划与5F-IMRT计划。比较两种计划的靶区适形度指数、均匀性指数、靶区覆盖度和危及器官的受照剂量体积,同时比较两组计划实施时的治疗时间和机器跳数。结果 在两种计划的靶区比较中,RapidArc计划的靶区适形度指数为(0.88±0.03),高于5F-IMRT计划的(0.79±0.02)(t=8.28,P<0.05);RapidArc计划的均匀性指数为(9.01±0.73),优于5F-IMRT计划的(10.44±1.08)(t=-2.73,P<0.05)。两组计划在同侧肺受照剂量体积比较中RapidArc计划的D_mean、V₁₀、V₂₀、V₃₀小于5F-IMRT计划(t=-7.53、-7.20、-8.39、-7.80,P<0.05),但RapidArc计划中的V₅较5F-IMRT计划增加了约16% (t=5.67,P<0.05);心脏的受照剂量体积比较中RapidArc计划中的D_mean、V₅、V₁₀均高于5F-IMRT(t=10.46、28.76、5.40,P<0.05),但在RapidArc计划中心脏的V₃₀低于5F-IMRT (t=-6.12,P<0.05)。对侧肺和对侧乳腺的V₅在RapidArc计划中明显高于5F-IMRT计划 (肺:t=21.50,P<0.05;乳腺:t=5.44,P<0.05)。RapidArc计划中机器跳数减少了25%,平均治疗时间节省了60%。结论 乳腺癌保乳术后RapidArc计划与5F-IMRT计划比较提高了靶区的适形度和均匀度,减少了高剂量区的受照体积,降低了机器跳数,缩短了治疗时间,但增加了正常组织低剂量区的受照体积。     

三维适形、逆向调强及旋转调强放疗技术对部分乳腺外照射的剂量学比较

目的 比较三维适形(3 D-CRT)、逆向调强(IMRT)及旋转调强(V-MAT)3种部分乳腺外照射(EB-PBI)治疗计划的剂量学差异.方法 选择定位影像资料完整的12例保乳术后行EB-PBI患者,每例患者分别设计3D-CRT、IMRT、V-MAT 3种治疗计划,比较3种计划的靶区剂量分布、危及器官受照剂量及所需机器跳数(MU)和治疗时间.结果 3D-CRT计划的靶区适形度最差,V-MAT计划的处方剂量靶区覆盖率及靶区剂量均匀性最差.3D-CRT计划中患侧肺V5、V10和平均剂量低,而患侧肺V30高;计划间患侧肺V20差异无统计学意义;V-MAT计划中15、20和25 Gy剂量包绕的同侧正常乳腺体积少;对于心脏V5、平均剂量及最大剂量、对侧肺平均剂量、甲状腺平均和最大剂量,IMRT＞ V-MAT＞ 3D-CRT,计划间两两比较差异均有统计学意义(z=-2.94 ～ -2.09,P＜0.05).3D-CRT、IMRT和V-MAT计划所需MU值分别为417.6 ±34.4、772.8±54.4和631.0±109.0,计划间两两比较差异均有统计学意义(z=-2.93、-2.76、-2.93,P＜0.05);V-MAT计划施照时间短.结论 对于部分乳腺癌的放射治疗,旋转调强计划在降低患侧靶区外正常乳腺组织受照射剂量和减少治疗时间方面优势比较明显.     

Synchronous bilateral breast cancer irradiation: clinical and dosimetrical issues using volumetric modulated arc therapy and simultaneous integrated boost

Objectives

The aim of the present retrospective analysis was to evaluate dosimetric parameters, feasibility and outcome for Synchronous Bilateral Breast Cancer (SBBC) patients treated with adjuvant radiotherapy (RT) by Volumetric Modulated Arc Therapy (VMAT).

Methods

From September 2011 to April 2016, 1100 Breast Cancer (BC) patients were referred to our institution to receive adjuvant breast RT, and those with SBBC were selected for the present analysis. A total of 16 patients were identified. A total dose of 50 Gy in 25 fractions was prescribed to the Planning Target Volume of the whole bilateral breast (PTV_BN) with or without the supraclavicular and infraclavicular nodes, while a total dose of 60 Gy in 25 fractions was prescribed to the surgical bed (PTV_boost). Several V _xGy and Dx% parameters were analyzed for the PTVs, together with Conformity and Homogeneity indexes (CI, HI), and for the critical Organs at risk (OARs), lungs and heart first.

Results

With a median follow-up of 24 months, no acute or late side effects more than grade 2 were observed. All patients are alive without any sign of disease. For target dose coverage, our observed inter-patients averages (±1 sd) were V _{95% Dp} = 96.7 ± 1.6% (96.3 ± 1.8%) to the left (right) PTV_BN, V _{95% Dp} = 98.6 ± 2.7% (99.4 ± 0.9%) to the left (right) PTV_boost, and D _2% = 64.4 ± 1.8 Gy (65.0 ± 2.0 Gy) to the left (right) PTV_boost, respectively. With regard to the heart, the inter-patient average of D _mean was 8.3 ± 3.3 Gy. For the lungs, the inter-patient average of D _mean, V _5 Gy and V _20 Gy were 11.8 ± 2.3 Gy, 78.9 ± 15.3% and 15.7 ± 5%, respectively.

Conclusions

The present retrospective analysis showed the feasibility, tolerability and safety of VMAT in the treatment of SBBC patients. Further studies are necessary to confirm these preliminary data.

     

A systematic review of methods to immobilise breast tissue during adjuvant breast irradiation

Greater use of 3D conformal, Intensity Modulated Radiotherapy (IMRT) and external beam partial breast irradiation following local excision (LE) for breast cancer has necessitated a review of the effectiveness of immobilisation methods to stabilise breast tissue.To identify the suitability of currently available breast (rather than thorax) immobilisation techniques an appraisal of the literature was undertaken. The aim was to identify and evaluate the benefit of additional or novel immobilisation approaches (beyond the standard supine, single arm abducted and angled breast board technique adopted in most radiotherapy departments). A database search was supplemented with an individual search of key radiotherapy peer-reviewed journals, author searching, and searching of the grey literature. A total of 27 articles met the inclusion criteria.The review identified good reproducibility of the thorax using the standard supine arm-pole technique. Reproducibility with the prone technique appears inferior to supine methods (based on data from existing randomised controlled trials). Assessing the effectiveness of additional breast support devices (such as rings or thermoplastic material) is hampered by small sample sizes and a lack of randomised data for comparison.Attention to breast immobilisation is recommended, as well as agreement on how breast stability should be measured using volumetric imaging.     

非均整器模式在左侧乳腺癌改良根治术后患者深吸气屏气容积旋转调强放疗中的剂量学优势

目的 比较非均整器（FFF）模式和均整器（FF）模式在左侧乳腺癌改良根治术后深吸气屏气（DIBH）动态容积旋转调强放疗（VMAT）中的剂量学差异。 方法 回顾性分析2020年12月至2021年5月在西安交通大学第一附属医院行DIBH放疗的16例左侧乳腺癌改良根治术后女性患者的临床资料,年龄37~61（43.5±5.7）岁。对同一患者分别设计FFF和FF模式的VMAT计划,给予计划靶区（PTV）相同的处方剂量50 Gy/25次,在达到相同的剂量归一条件下,比较靶区剂量学、危及器官受量及机器执行效率的差异。组间数据比较采用配对t检验。 结果 2种模式下靶区PTV的D2%、D50%、D98%（Dx%表示x%靶体积的受照剂量）、适形指数、平均指数及梯度指数差异均无统计学意义（t=−1.519~1.644,均P>0.05）;FFF模式的心脏V5 Gy、V30 Gy（Vx Gy表示≥x Gy体积占总体积的百分比）及平均剂量（Dmean）,患侧肺V5 Gy、V10 Gy及Dmean,全肺V5 Gy、V10 Gy、V20 Gy及Dmean,患者受照剂量的V5 Gy均优于FF模式,组间比较差异均有统计学意义（t=−4.741~−2.156,均P<0.05）;FFF模式机器跳数是FF模式的1.32倍[（1073.41±143.79）MU对（815.70±87.69） MU],但执行时间却减少为FF模式的88.9%[（128.00±11.64） s对（144.75±11.45） s],且差异均有统计学意义（t=8.665、−4.373,均P<0.05）。 结论 2种模式下靶区剂量相似,FFF模式危及器官受照剂量更低,并且可显著缩短DIBH治疗时间。     

Image-guided volumetric modulated arc therapy for breast cancer: a feasibility study and plan comparison with three-dimensional conformal and intensity-modulated radiotherapy

Objective:

To test the feasibility of volumetric modulated arc therapy (VMAT) in breast cancer and to compare it with three-dimensional conformal radiotherapy (3D-CRT) as conventional tangential field radiotheraphy (_conTFRT).

Methods:

12 patients (Stage I, 8: 6 left breast cancer and 2 right breast cancer; Stage II, 4: 2 on each side). Three plans were calculated for each case after breast-conserving surgery. Breast was treated with 50 Gy in four patients with supraclavicular lymph node inclusion, and in eight patients without the node inclusion. Multiple indices and dose parameters were measured.

Results:

V95% was not achieved by any modality. Heterogeneity index: 0.16 (VMAT), 0.13 [intensity-modulated radiotherapy (IMRT)] and 0.14 (_conTFRT). Conformity index: 1.06 (VMAT), 1.15 (IMRT) and 1.69 (_conTFRT). For both indices, IMRT was more effective than VMAT (p=0.009, p=0.002). D_mean and V20 for ipsilateral lung were lower for IMRT than VMAT (p=0.0001, p=0.003). D_mean, V2 and V5 of contralateral lung were lower for IMRT than VMAT (p>0.0001, p=0.005). Mean dose and V5 to the heart were lower for IMRT than for VMAT (p=0.015, p=0.002).

Conclusion:

The hypothesis of equivalence of VMAT to IMRT was not confirmed for planning target volume parameter or dose distribution to organs at risk. VMAT was inferior to IMRT and 3D-CRT with regard to dose distribution to organs at risk, especially at the low dose level.

Advances in knowledge:

New technology VMAT is not superior to IMRT or conventional radiotherapy in breast cancer in any aspect.In Western countries, one in every eight females is diagnosed with breast cancer. Breast-conserving surgery with post-operative radiotherapy (RT) is the primary therapeutic strategy for Stages I and II of breast cancer. Systemic therapy is also part of the primary therapeutic strategy in most patients with Stage I and II breast cancer. RT substantially reduces the rate of local relapse and improves long-term survival [1]. However, RT is suggested to be associated with morbidity of the heart [2,3], lung [4,5], subcutaneous tissue and skin [6] and a risk of secondary malignancies [7–9].A large body of available data regarding the potential toxicity of RT was published between 1980 and the end of 1990 [1]. Special clinical interest has been focused on acute and mostly transient lung and skin toxicity, axillary problems and late cardiac events, in addition to the risk of secondary malignancies. This period was characterised by RT delivery using a fluoroscopic technique with two-dimensional planning followed by three-dimensional (3D) conformal techniques with two conventional tangential field radiotherapy (_conTFRT) fields. _conTFRT encompassed the whole breast, skin, minor ipsilateral lung volume, a part of the axillary region at Level 1 and a part of the heart in the case of left-sided cancer [10–12]. These areas have been sites for local toxicity, because RT principles, and thus homogeneous photon flux across treatment fields, remained unchanged.Intensity-modulated radiotherapy (IMRT) has been implemented in the past decade, permitting variation of fluence modulation across fields and allowing optimal dose administration according to an individual''s anatomy. IMRT results in improved avoidance of critical structures such as the heart, skin, axillary region and lung, while facilitating necessary tumour volume coverage [13,14]. Clinical data on IMRT show an improvement in dose homogeneity within the irradiated breast and sparing of the heart and lung [14–17]. However, a disadvantage of IMRT over _conTFRT is the long treatment duration owing to the higher number of fields and monitor units (MUs) involved. In addition, although IMRT reduces the volume of the heart and ipsilateral lung that receive high doses, it is associated with an increase in overall low-dose radiation. Despite the available clinical data, the wider use and specific indications for IMRT for breast cancer have not been established.In volumetric modulated arc therapy (VMAT), technical extension of conventional fixed-field IMRT, an optimised dose distribution is possible with a single gantry rotation. Studies have shown that VMAT reduces the number of MUs and treatment delivery time [18–22], with similar or better planning target volume (PTV) coverage and sparing of organs at risk (OARs) than IMRT. Reports on VMAT for breast cancer are few and mainly concern planning comparisons [20,23–28] and very preliminary clinical data [29].The RapidArc® system (Varian Medical Systems, Palo Alto, CA) has recently been introduced in our department. Accordingly, we have begun examining the potential of RapidArc VMAT for breast cancer treatment in a prospective clinical setting to adequately evaluate dosimetric parameters, treatment planning and clinical implications as well the disadvantages.The present study aimed to compare the use of RapidArc VMAT with IMRT and _conTFRT for breast cancer therapy. We hypothesised that the use of RapidArc under routine clinical circumstances would be equivalent to or better than IMRT and _conTFRT in terms of PTV coverage and OAR sparing, while reducing both treatment time and MUs.     

Tomosynthesis as a screening tool for breast cancer: A systematic review

BackgroundMammography is an important screening tool for reducing breast cancer mortality. Digital breast tomosynthesis (DBT) can potentially be integrated with mammography to aid in cancer detection.MethodUsing the PRISMA guidelines, a systematic review of current literature was conducted to identify issues relating to the use of tomosynthesis as a screening tool together with mammography.FindingsUsing tomosynthesis with digital mammography (DM) increases breast cancer detection, reduces recall rates and increases the positive predictive value of those cases recalled. Invasive cancer detection is significantly improved in tomosynthesis compared to mammography, and has improved success for women with heterogeneous or extremely dense breasts.ConclusionTomosynthesis reduces some limitations of mammography at the time of screening that until recently were most often addressed by ultrasound at later work-up. Tomosynthesis can potentially be adopted alongside mammography as a screening tool.     

加速器运行误差对宫颈癌容积旋转调强放疗的剂量学影响

目的 研究加速器机架旋转角度、准直器到位和多叶光栅（MLC）叶片到位等误差对宫颈癌容积旋转调强放疗（VMAT）的剂量学影响。方法 选取10例已行VMAT的宫颈癌计划,提取Pinnacle³ V9.2计划系统（美国Philips公司）中每个临床计划的plan.Trail文件,使用Matlab编写的程序读取并修改每个控制点运行参数,从而模拟加速器运行误差。通过各引入误差的计划与原计划的剂量比较,评估加速器各参数运行误差对VMAT的剂量学影响及主要的影响因素。结果 在引入机架旋转角度误差、准直器到位误差和两侧MLC叶片同向偏移误差中,PTV各剂量限值的最大变化分别为0.16%、0.46%和0.57%,危及器官（OAR）各剂量限值的最大变化分别为0.38%、-1.32%和-0.44%。引入两侧MLC叶片反向或相向运动误差,其幅度为±0.5、±1和±2 mm时,导致PTV各剂量限值变化的最大值分别为2.11%、3.04%和6.03%,各OAR平均剂量变化的最大值分别为2.17%、3.92%和7.97%,且PTV和OAR各剂量限值与MLC反向或相向运动误差呈强线性相关（t=21.201~90.562,P<0.05）。引入各参数实际执行误差值时,PTV和OAR各剂量限值的最大变化分别为0.16%和1.30%,适形指数（CI）和均匀性指数（HI）基本不变。结论 执行宫颈癌VMAT计划时,两侧MLC叶片反向或同向运动误差相比机架旋转角度误差、准直器到位误差和MLC叶片同向偏移误差对VMAT剂量学影响更加显著,因此,应加强对加速器质控尤其MLC叶片到位误差的质量控制以提高放疗的精度。