锥形束CT测量胸段食管癌调强放疗摆位误差对剂量学的影响

目的 应用千伏级锥形束CT(kV-CBCT)测量胸段食管癌调强放疗的摆位误差,探讨摆位误差对肿瘤靶体积和周围正常组织受照剂量的影响.方法 21例胸段食管癌患者经图像引导调强放疗,共获得173组CBCT摆位误差数据,利用这些数据在三维治疗计划系统中模拟患者的实际治疗过程,分析摆位误差对肿瘤靶区及周围正常组织受照剂量的影响.结果 21例患者左右、头脚、前后方向的摆位误差分别是(2.73 ±1.85)、(3.19±2.71)和(2.35±1.71)mm.摆位误差对患者GTV的剂量学影响不明显,但误差却使患者95％ PTV( D95％)接受的剂量与标准计划相比降低3.38 Gy,PTV最小剂量(Dmin)和平均剂量(Dmean)分别下降9.83和0.65 Gy,摆位误差的修正提高了计划靶区的适形度和剂量均匀性,标准计划相应值分别为(0.74±0.10)和(1.07±0.02),模拟计划相应值分别为(0.69±0.08)和(1.13±0.07),差异均有统计学意义(t=3.43和-3.91,P＜0.05);摆位误差对脊髓的最大剂量(Dmax)、双肺和心脏等周围正常组织受照剂量影响,差异无统计学意义(P＞0.05),模拟计划中脊髓的最大剂量均值为(42.20±4.97)Gy,标准计划为(41.37±2.75) Gy,摆位误差使部分患者脊髓最大剂量超过45 Gy,其中1例最大值达到52.8 Gy.结论 kV-CBCT图像引导胸段食管癌调强放疗可减小患者的摆位误差,提高PTV的受照剂量和治疗精度,摆位误差对双肺、脊髓和心脏受照剂量未见明显改变.     

乳腺癌术后胸壁大体积复发二野和六野调强放疗剂量学比较

目的 比较乳腺癌术后胸壁大体积复发2野和6野调强放疗的计划差异.方法 对8例乳腺切除术后胸壁大体积复发病例,Pinnacle计划系统上分别对PTV进行2野调强和6野调强放疗计划设计,PTV处方剂量为50 Gy/25次(GTV后续计划补量至66～70 Gy),比较2种计划95％处方剂量PTV适形指数(CI)、均匀性指数(HI)及心脏、同侧肺剂量.结果 6野IMRT计划的CI和HI均优于2野IMRT计划,6野和2野的CI分别为(0.66±0.08)和(0.53±0.10)(t=7.99,P＜0.05),HI分别为(1.36±0.08)和(2.19±0.78)(t=9.04,P＜0.05).2个计划中肺V5、V10、V20、V35和心脏Dmax、V35、Dmean值比较差异无统计学意义.结论 乳腺癌切除术后胸壁大体积复发患者行放疗,6野静态逆向调强放疗计划靶区覆盖优于2野,而心肺受量方面无明显差异.     

多叶准直器叶片位置误差对鼻咽癌调强放疗剂量的影响

目的 分析多叶准直器(MLC)叶片位置误差对鼻咽癌调强放射治疗靶区和危及器官剂量的影响.方法 选取10例已行鼻咽癌调强放疗患者计划,通过修改MLC文件,在计划文件中引入MLC叶片的位置误差,模拟调强计划执行过程中可能出现的叶片不到位情况,比较不同模拟计划与原计划的剂量学差异.结果 2 mm范围内的叶片随机误差及叶片偏移误差的剂量学影响差异无统计学意义(JP＞0.05),计划靶区(PGTV、PTV1及PTV2)D95％最大改变量为(-0.92±0.51)％、(1.00±0.24)％和(0.62±0.17)％,脊髓及脑干D0.1cc最大改变量为(1.90±2.80)％和(-1.78±1.42)％,左右腮腺Dmean最大改变量为(1.36±1.23)％和(-2.25±2.04)％.与原计划相比,当叶片外扩达2 mm时,PGTV、PTV1及PTV2的D95％和D5％受量显著增加(t=8.97、10.97、9.74、7.30、6.04、3.04,P＜0.05);脊髓及脑干D0.1cc显著增加(t=6.16、9.22,P＜0.05);左右腮腺Dmean显著增加(t=7.12、4.25,P＜0.05).结论 鼻咽癌调强放疗时,直线加速器MLC叶片在一定范围内的随机误差及叶片整体偏向一侧的位置误差对剂量分布的影响并不显著,叶片外扩及内收的位置误差对剂量分布的影响不可忽略,应加强对MLC系统位置误差的质量控制以提高放疗精度.     

基于元启发策略的肿瘤调强放疗自动计划方法

目的提出一种基于元启发策略的放疗自动计划方法(ATP-STAR),并验证其有效性。方法ATP-STAR方法的主要过程为先对优化参数进行向量化编码,采用高斯卷积修正优化参数,再利用模拟退火选择备选优化参数向量集,结合射野通量优化,并行探索最优的优化参数组合,实现计划自动试错。选取20例肿瘤个体化差异较大的病例进行方法测试。邀请具备5年以上临床工作经验的物理师进行人工计划设计。人工计划和ATP-STAR计划均基于开源matRad计划系统完成,射野及处方剂量与临床治疗计划保持一致。分析不同病种ATP-STAR与人工计划的靶区和危及器官剂量学差异。结果对靶区而言,ATP-STAR计划的均匀性优于人工计划(脑瘤:z=2.28,P=0.022;肺癌:z=2.29,P=0.022;肝癌:z=2.11,P=0.035),脑瘤和肝癌ATP-STAR计划的适形性与人工计划相当,肺癌ATP-STAR计划的适形性略差于人工计划(z=2.29,P=0.022)。对脑瘤的危及器官而言,相比于人工计划,ATP-STAR计划的左眼晶状体Dmean平均受量由2.19 Gy降至1.76 Gy(z=2.28,P=0.022),左视神经Dmean由11.36 Gy降至10.22 Gy(z=2.28,P=0.022),右视神经Dmax由32.92 Gy降至29.97 Gy(z=2.10,P=0.036),垂体Dmax由39.53 Gy降至35.21 Gy(z=2.29,P=0.022)。对肺癌的危及器官而言,ATP-STAR计划的脊髓Dmax平均受量由38 Gy降至31.17 Gy(z=2.12,P=0.034),双肺Dmean由8.51 Gy降至8.07 Gy(z=2.29,P=0.022),心脏Dmean由3.21 Gy降至2.69 Gy(z=2.29,P=0.022)。对肝癌的危及器官而言,ATP-STAR计划的脊髓Dmax由18.19 Gy降至14.76 Gy(z=2.11,P=0.035),肝脏Dmean由15.61 Gy降至14.45 Gy(z=2.11,P=0.035),肾脏Dmean由4.76 Gy降至4.04 Gy(z=2.10,P=0.036)。结论ATP-STAR方法较少依赖人工计划设计经验,易于推广,有望改善调强放疗计划质量及一致性,并节省临床人力和时间成本。     

调强放疗对36例鼻咽癌患者腮腺功能的保护作用

目的 探讨调强适形放疗对鼻咽癌患者腮腺功能的保护作用。方法采用均衡配对方法将36例鼻咽癌患者分为调强放疗组(调强组)和常规放疗组(常规组),每组18例。调强组计划靶体积(pGTVnx) 72.0 Gy,常规组放疗2.0Gy/次,5次/周,共70.0Gy。于放疗前、放疗结束时及放疗后3及6个月、1及2年进行腮腺动态显像检测,计算腮腺的放射性摄取指数(UI)及酸性刺激后的分泌指数(EI)。并利用剂量体积直方图对腮腺组织进行受量分析。结果调强组和常规组的患者在放疗结束时、2年后腮腺的UI分别是77.6％、96.2％和56.8％、7.0％,EI分别是64.1％、95.3%和19.4％、0。调强组和常规组患者的健侧和患侧腮腺受照射的平均剂量分别为20.0、31.0Gy和61.0、68.2Gy。结论调强放疗可以明显减少腮腺受照剂量,有效保护腮腺功能。     

鼻咽癌调强放疗和常规放疗早期反应的对照观察

目的观察鼻咽癌病人调强放疗和常规放疗的早期治疗结果和早期并发症情况。方法78例Ⅰ～Ⅲ期鼻咽癌病人分为调强放疗组(38例)和常规放疗组(40例)。常规放疗采用面颈联合野+锁骨上野及耳前野+后颈电子线野,靶区剂量2Gy/(次·天);调强放疗先设定7～9个适形野,再设定80～100个调强子野照射,靶区剂量2.2Gy/(次·天)。研究调强放疗和常规面颈联合野放疗病人的腮腺、脊髓、临床靶区和计划靶区的平均受照体积,观察放疗期间病人的皮肤反应、口干(腮腺)反应和口腔黏膜反应。结果所有病人放疗后鼻咽及周围病灶明显消退。腮腺、脊髓、临床靶区和计划靶区的受照体积调强放疗组分别为(30±4.8)%、(56±6.7)%、(95±8.6)%、(92±8.1)%,常规放疗组分别为(98±9.4)%、(56±10.7)%、(100±9.7)%、(99±9.5)%,调强放疗组腮腺受照体积明显低于常规放疗组。调强放疗组的皮肤反应多为Ⅰ级,口干(腮腺)反应多为Ⅰ、Ⅱ级,口腔黏膜反应为Ⅰ、Ⅱ级。而常规放疗组的皮肤反应及口干(腮腺)反应多为Ⅱ、Ⅲ级,口腔黏膜反应为Ⅱ、Ⅲ级。其中口干(腮腺)反应、皮肤反应、口腔黏膜反应Ⅱ、Ⅲ级者调强放疗组明显少于常规放疗组。另外,调强放疗组的放疗时间为45.0±4.4天,少于常规放疗组的51.0±5.3天。但调强放疗组放疗后鼻咽腔炎症反应较重。结论使用调强技术可明显减轻鼻咽癌病人放疗的口干和皮肤反应等早期放疗反应,并能缩短放疗时间。     

COMPASS系统在鼻咽癌容积旋转调强剂量验证中的应用

目的 探讨COMPASS三维剂量验证系统在鼻咽癌容积旋转调强剂量验证中的应用.方法 选取8例鼻咽癌病例在Masterplan治疗计划系统中进行旋转调强计划设计,然后将治疗计划分别传输至COMPASS系统和控制加速器运行的MOSAIQ网络上.比较计划系统计算结果和COMPASS实际测量结果差异的主要指标,如靶区的平均剂量(Dmean)、95％体积剂量(D95％)和γ值,脊髓、脑干的Dmean和D1％左右腮腺的Dmean、V30.结果 计划系统计算结果和COMPASS实际测量的结果二者在靶区的γ通过率均＞95％,各个靶区的D95%平均偏差大多＜3％,各个靶区Dmean的偏差平均值在1％以内.脊髓和脑干的D1％的平均偏差分别为(4.3±3.0)％和(5.9±2.9)％,二者Dmean的平均偏差分别为(5.3±3.0)％和(8.0±3.5)％.COMPASS测量的脊髓和脑干的剂量都比计划系统计算的结果小.左右腮腺Dmean差异的平均值分别为(6.1±3.1)％、(4.7±4.4)％,V30的差异分别为(9.4±7.5)％和(9.4±9.9)％.结论 COMPASS三维剂量验证系统是容积旋转调强剂量验证的一个非常理想的工具,可以快速、直观地分析出靶区和正常器官理论和实际照射情况下的差异.     

18F-FLT PET显像预测肿瘤放射敏感性的实验研究

目的 探讨18 F-FLT PET显像能否预测肿瘤放射敏感性.方法 对乳腺癌MDA-MB-231细胞和脑胶质瘤LN229细胞以6 MVX线照射0、8和16Gy后分别行克隆形成细胞存活率实验和18 F-FLT细胞摄取实验,各剂量组2种细胞的数据差异行t检验,同种细胞放疗前(0 Gy)与放疗后数据差异行单因素方差分析.将MDA-MB-237和LN229细胞分别接种至雌性BALB/c nu/nu裸鼠右后肢外侧皮下,待肿瘤直径长至10 mm时,将2种荷瘤鼠均按0、8和16 Gy分组(随机数字表法),每组20只.各组按相应剂量放疗后分别行18F-FLT PET显像和免疫组织化学检测,计算肿瘤与肌肉的SUV比值(T/M)和TK1标记指数(LITK1),并行相关性分析.结果 8Gy辐照后MDA-MB-231细胞和LN229细胞生存分数分别为(59.73±4.3)％和(93.41±3.75)％(t=-13.20,P＜0.001),16 Gy时两者生存分数分别为(43.57±4.06)％和(81.77±4.42)％(t=-14.24,P＜0.001).8Gy辐照后1 h MDA-MB-231细胞18F-FLT摄取降至(18.32±1.38) kBq/105细胞[0Gy时为(128.22±8.24) kBq/105细胞,F=266.41,P＜0.01],72h内保持在较低水平;LN229细胞辐照后1h摄取降至(9.87±1.30) kBq/105细胞[0 Gy时为(134.88±6.59) kBq/105细胞,F=346.06,P＜0.01],后逐渐增加,72 h时升至(127.17±9.08) kBq/105细胞(F =346.06,P＞0.05);16 Gy时2种细胞摄取变化基本同8Gy组.8 Gy放疗后裸鼠MDA-MB-231移植瘤18 F-FLT摄取在第1天T/M比值下降至0.78±0.39(放疗前为2.84±0.29,F=39.78,P＜0.01),后缓慢升高,在第7天时仍低于放疗前水平(F=39.78,P＜0.01);16 Gy时变化基本同8Gy组.LN229移植瘤8 Gy放疗在第1天T/M比值升高至2.41±0.47(放疗前为1.58±0.29,F=34.01,P＜0.05),后逐渐降低,到第7天降至0.66±0.32(F=34.01,P＜0.05);16 Gy放疗后18 F-FLT摄取值持续下降,至第7天降到0.44±0.22 (F=41.85,P＜0.01).2组细胞移植瘤8Gy和16 Gy放疗后18F-FLT摄取与TK1表达相关(8 Gy:r =0.67,0.73; 16 Gy:r =0.73,0.69,均P＜0.01).结论 实验结果示18F-FLT PET显像能够预测肿瘤放射敏感性,能否应用于临床需进一步研究.     

中下段食管癌调强放疗布野方案剂量学比较

目的 分析中下段食管癌放疗中5野调强计划与7野调强计划的差异,寻找布野最佳方案.方法 分别为接受调强放射治疗的12例中下段食管癌患者设计5野调强计划与7野调强计划,计划设计中要求95％的计划靶体积达到处方剂量.在每个病例中,分别比较两种计划的剂量体积直方图统计数据、剂量均匀指数、剂量适形指数.结果 两种方案中,7野调强计划的靶区剂量适形度较好(t=2.681,P＜0.05);两种方案的剂量均匀指数、脊髓受照剂量、心脏受照剂量之间的差异无统计学意义;5野调强计划的双肺V5、V10、V15较低(t=-7.938、-12.055和4.859,P均＜0.05).结论 在中下段食管癌放疗中,与7野调强计划相比,5野调强计划可以减少肺部的低剂量受照体积,同时提供可以接受的计划靶体积适形度,有助于减少肺部辐射损伤的发生概率,改善患者生存质量,值得在临床工作中推广应用.     

食管癌调强放疗中摆位误差对剂量学的影响

目的通过电子射野影像装置(EPID)测量食管癌患者在调强放疗过程中的摆位误差,分析摆位误差对靶区和正常组织受量的影响,验证目前计划靶体积(PTV)外放范围的合理性。方法 36例食管癌患者用EPID测量其摆位误差,每位患者接受摆位验证4~6次(1次/周)。在医科达(CMS-XIO)治疗计划系统上模拟实际摆位误差,比较实际治疗过程中大体肿瘤体积(GTV)、临床靶区体积(CTV)和周围正常组织的受照剂量。结果 36例食管癌患者前后、左右、头脚方向摆位误差分别为(2.43±1.80)、(2.56±1.87)和(3.53±2.82)mm。摆位误差使食管癌患者GTV的95%体积接受的剂量(D95)与原治疗计划相比降低了50 c Gy,CTV的D95降低了78.21 c Gy。原计划(P1)和摆位误差计划(P2)的全肺接受20 Gy照射体积占全肺体积的百分比(V20)分别为24.34%和23.52%(P<0.05);心脏平均剂量分别为2 067.23 c Gy和2 021.33 c Gy(P<0.05);P1中无一例脊髓受量超过4 500 c Gy,而P2中12例脊髓最大剂量超过4 500 c Gy,其中1例最大剂量为5 602.70 c Gy。结论摆位误差使GTV、CTV的受照剂量降低,部分患者脊髓最大剂量超过耐受量,双肺、心脏受照剂量有所下降。     

乳腺癌保乳术后静态逆向调强与三维适形野中野放疗的剂量学比较

目的 比较早期乳腺癌保乳术后静态逆向调强(IMRT)与三维适形野中野瘤床同步加量(FIF)两种放疗技术的剂量学差异。方法 选择9例左侧早期乳腺癌保乳术后患者,分别设计IMRT与FIF两组放疗计划,处方剂量为乳房靶区50.4 Gy,分28次,每次1.8 Gy;瘤床靶区61.6 Gy,分28次,每次2.2 Gy。比较两组计划的靶区适形度及危及器官受量,并比较两者的计划优化和治疗时间。结果 IMRT的全乳靶区适形度(CI)为1.82±0.16,低于FIF的2.21±0.15(t=2.08,P<0.05);瘤床靶区适形度为1.19±0.04,低于FIF的1.59±0.11(t=3.97,P<0.05)。两组计划危及器官同侧肺的V₂₀和心脏的V₃₀无明显差异。FIF对侧肺的Dmax和Dmean分别是(5.41±2.76)和(0.51±0.10) Gy, IMRT分别为(25.72±2.61)和(7.46±0.39) Gy(t=-22.44、-21.14,P<0.05)。对侧乳房的Dmax和Dmean,FIF为(8.50±5.61)和(0.46±0.11) Gy,IMRT为(27.73±4.29)和(6.38±0.48) Gy(t=-5.66、-14.83,P<0.05)。对于对侧肺和乳房的低剂量照射区V₅,FIF为(0.09±0.09)%和(0.45±0.45)%,低于IMRT的(84.66±3.06)%和(60.79±4.94)%(t=-28.19、-12.80,P<0.05)。在计划优化及治疗时间方面,FIF与IMRT优化时间分别为(61.57±0.89)min和(241.28±1.06)min,单次治疗时间分别为(16.14±1.42)min和(29.85±0.59) min(t=-32.35、-8.82,P<0.05)。结论 IMRT改善了靶区适形度,但是增加了对侧肺和对侧乳房的受照剂量。FIF在计划优化时间及治疗时间方面有优势。     

Stereotactic body radiation therapy planning with duodenal sparing using volumetric-modulated arc therapy vs intensity-modulated radiation therapy in locally advanced pancreatic cancer: A dosimetric analysis

Stereotactic body radiation therapy (SBRT) achieves excellent local control for locally advanced pancreatic cancer (LAPC), but may increase late duodenal toxicity. Volumetric-modulated arc therapy (VMAT) delivers intensity-modulated radiation therapy (IMRT) with a rotating gantry rather than multiple fixed beams. This study dosimetrically evaluates the feasibility of implementing duodenal constraints for SBRT using VMAT vs IMRT. Non–duodenal sparing (NS) and duodenal-sparing (DS) VMAT and IMRT plans delivering 25 Gy in 1 fraction were generated for 15 patients with LAPC. DS plans were constrained to duodenal D_max of<30 Gy at any point. VMAT used 1 360° coplanar arc with 4° spacing between control points, whereas IMRT used 9 coplanar beams with fixed gantry positions at 40° angles. Dosimetric parameters for target volumes and organs at risk were compared for DS planning vs NS planning and VMAT vs IMRT using paired-sample Wilcoxon signed rank tests. Both DS VMAT and DS IMRT achieved significantly reduced duodenal D_mean, D_max, D_1cc, D_4%, and V_20 Gy compared with NS plans (all p≤0.002). DS constraints compromised target coverage for IMRT as demonstrated by reduced V_95% (p = 0.01) and D_mean (p = 0.02), but not for VMAT. DS constraints resulted in increased dose to right kidney, spinal cord, stomach, and liver for VMAT. Direct comparison of DS VMAT and DS IMRT revealed that VMAT was superior in sparing the left kidney (p<0.001) and the spinal cord (p<0.001), whereas IMRT was superior in sparing the stomach (p = 0.05) and the liver (p = 0.003). DS VMAT required 21% fewer monitor units (p<0.001) and delivered treatment 2.4 minutes faster (p<0.001) than DS IMRT. Implementing DS constraints during SBRT planning for LAPC can significantly reduce duodenal point or volumetric dose parameters for both VMAT and IMRT. The primary consequence of implementing DS constraints for VMAT is increased dose to other organs at risk, whereas for IMRT it is compromised target coverage. These findings suggest clinical situations where each technique may be most useful if DS constraints are to be employed.     

移动滑轨在椎体瘤调强放疗计划中的动态剂量扰动

目的 研究Qfix kVue治疗床移动滑轨在椎体瘤调强放射治疗(IMRT)计划中的动态剂量扰动。方法 移除EDGE直线加速器碳基绝缘滑轨,进行CT扫描并上传至治疗计划系统,重建床板和滑轨模型。依据均质模体和非均质患者CT,分别制作6和10 MV光子IMRT计划(180°、200°、220°、160°、140°),处方剂量为3 Gy/次,共10次,采用AcruosXB计算剂量。分别制作无滑轨和双侧滑轨对称移动(4~19 cm,步长1 cm)的优化计划。在优化计划中添加、移除滑轨结构,创建验证计划。对比分析验证计划和优化计划的差异,包括靶区平均剂量(D_mean)、均匀性指数(HI)、适形度指数(CI)和脊髓最大剂量(D_max)。结果 有无滑轨患者靶区HI均变差,其最大差值为2%。6 MV有滑轨时患者靶区D_mean减少(2.07±0.99)%,靶区CI值增加(4.91±3.12)%,脊髓D_max减少(1.83±1.37)%。无滑轨时患者靶区D_mean增加(2.02±0.96)%,靶区CI减少(3.07±1.31)%,脊髓D_max增加(2.03±1.44)%。移除和添加滑轨组间,靶区D_mean、CI和脊髓D_max差值差异有统计学意义(F=27.55、361.32、13.05,P<0.05)。靶区D_mean和脊髓D_max随滑轨位置变化呈倾斜的"W"减少。在滑轨＜10 cm范围内,差值出现极大值。当滑轨向外侧移动时,差值逐渐减小为0,6 MV计划中靶区D_mean和脊髓D_max变化值＞10 MV。结论 Qfix kVue治疗床滑轨位置变化对椎体瘤IMRT计划扰动不可忽略,计划制作时应予以考虑,治疗时滑轨应与计划位置保持一致。     

Dosimetric comparison of different multileaf collimator leaves in treatment planning of intensity-modulated radiotherapy for cervical cancer

To study the effect of multileaf collimator (MLC) leaf widths (standard MLC [sMLC] width of 10 mm and micro-MLC [mMLC] width of 4 mm) on intensity-modulated radiotherapy (IMRT) for cervical cancer. Between January 2010 and August 2010, a retrospective analysis was conducted on 12 patients with cervical cancer. The treatment plans for all patients were generated with the same machine setup parameters and optimization methods in a treatment planning system (TPS) based on 2 commercial Elekta MLC devices. The dose distribution for the planning tumor volume (PTV), the dose sparing for organs at risk (OARs), the monitor units (MUs), and the number of IMRT segments were evaluated. For the delivery efficiency, the MUs were significantly higher in the sMLC-IMRT plan than in the mMLC-IMRT plan (802 ± 56.9 vs 702 ± 56.7; p < 0.05). The number of segments in the plans were 58.75 ± 1.8 and 59 ± 1.04 (p > 0.05). For the planning quality, the conformity index (CI) between the 2 paired IMRT plans with the mMLC and the sMLC did not differ significantly (average: 0.817 ± 0.024 vs 0.810 ± 0.028; p > 0.05). The differences of the homogeneity index (HI) between the 2 paired plans were statistically significant (average: 1.122 ± 0.010 vs 1.132 ± 0.014; p < 0.01). For OARs, the rectum, bladder, small intestine, and bony pelvis were evaluated in terms of V₁₀, V₂₀, V₃₀, and V₄₀, percentage of contoured OAR volumes receiving 10, 20, 30, and 40 Gy, respectively, and the mean dose (D_mean) received. The IMRT plans with the mMLC protected the OARs better than the plans with the sMLC. There were significant differences (p < 0.05) in evaluated parameters between the 2 paired IMRT plans, except for V₃₀ and V₄₀ of the rectum and V₁₀, V₂₀, V₄₀, and D_mean of the bladder. IMRT plans with the mMLC showed advantages over the plans with the sMLC in dose homogeneity for targets, dose sparing of OARs, and fewer MUs in cervical cancer.     

鼻咽癌三种调强放疗计划剂量学对比研究

目的 对比鼻咽癌常规固定野调强（IMRT）、容积旋转调强（VMAT）以及断层调强（HT）3种不同调强放疗计划的剂量学差异。方法 选择18例接受VMAT治疗的鼻咽癌患者,以相同处方剂量和目标条件分别重新进行IMRT和HT计划设计。比较3种计划靶区的均匀度（HI）、适形度（CI）、最大剂量以及平均剂量。危及器官的最大量和平均量以及感兴趣区的剂量体积、计划执行时间和机器跳数（MU）。结果 3种计划在靶区的覆盖率满足临床要求。IMRT计划在靶区的HI和CI方面结果最差,HT计划结果最优。危及器官方面,IMRT计划受量最高,HT计划的脊髓、脑干和腮腺受量最低;但对于视神经、晶状体以及视交叉HT计划的受量最高而VMAT计划的受量最低。IMRT的治疗时间（8.0±0.5） min高于VMAT（3.9±0.1）min和HT（7.4±0.9）min。与VMAT相比,IMRT每次治疗为（711.4±78.7）MU,高于VMAT的（596.4±33.7）MU。结论 鼻咽癌IMRT、VMAT以及HT计划在靶区覆盖和危及器官保护上都可以达到临床要求,在靶区的适形度和均匀性上HT计划优于VMAT和IMRT,但在治疗时间和加速器的机器跳数上VMAT较有优势。     

乳腺癌根治术后双弧VMAT与IMRT计划的剂量学比较

目的 比较乳腺癌根治术后双弧的容积旋转调强放射治疗(VMAT)与5野的静态调强放射治疗(IMRT)2种计划之间的剂量学差异,评估VMAT技术在乳腺癌根治术后的剂量学特点与应用能力.方法 选取28例乳腺癌根治术后患者(左侧10例,右侧18例),分别制定双90度弧段的VMAT与5野的IMRT 2种计划,主要的计划评估参数为靶区的肿瘤控制概率(TCP)、适形指数(CI)、均匀指数(HI)以及接受相应处方剂量水平照射体积百分比V₉₅、V₁₁₀,危及器官(OAR)评估包括患侧肺的正常组织并发症概率(NTCP)、D_mean、V₅、V₂₀、V₃₀,心脏的NTCP值、D_mean、V₂₅,健侧乳腺的D_mean、机器跳数(MU)以及治疗时间.结果 VMAT计划与IMRT计划的TCP值分别为(96±2)%、(90±2)%(t=-6.28,P<0.01);HI值分别为0.15±0.04,0.22±0.02(t=13.29,P<0.05);肿瘤位于左侧时,心脏NTCP值在VMAT计划与IMRT计划中分别为(1.0±0.12)%,(1.7±0.13)%(t=2.14,P<0.05);肿瘤位于右侧时,2种计划心脏的NTCP差异无统计学意义,平均剂量分别为(3.27±0.26)、(6.0±0.47)Gy(t=9.21, P<0.01);VMAT计划在MU少于IMRT计划(t=9.58,P<0.01),治疗时间短于IMRT计划(t=8.40,P<0.05).结论 乳腺癌根治术后,VMAT计划具有更强的临床应用能力,且表现出更优的剂量学特点.     

Pelvic Ewing sarcomas

Purpose

The goal of the present work was to assess the potential advantage of intensity-modulated radiotherapy (IMRT) over three-dimensional conformal radiotherapy (3D-CRT) planning in pelvic Ewing’s sarcoma.

Patients and methods

A total of 8 patients with Ewing sarcoma of the pelvis undergoing radiotherapy were analyzed. Plans for 3D-CRT and IMRT were calculated for each patient. Dose coverage of the planning target volume (PTV), conformity and homogeneity indices, as well as further parameters were evaluated.

Results

The average dose coverage values for PTV were comparable in 3D-CRT and IMRT plans. Both techniques had a PTV coverage of V₉₅ >?98?% in all patients. Whereas the IMRT plans achieved a higher conformity index compared to the 3D-CRT plans (conformity index 0.79?±?0.12 vs. 0.54?±?0.19, p?=?0.012), the dose distribution across the target volumes was less homogeneous with IMRT planning than with 3D-CRT planning. This difference was statistically significant (homogeneity index 0.11?±?0.03 vs. 0.07?±?0.0, p?=?0.035). For the bowel, D_mean and D_1%, as well as V₂ to V₆₀ were reduced in IMRT plans. For the bladder and the rectum, there was no significant difference in D_mean. However, the percentages of volumes receiving at least doses of 30, 40, 45, and 50 Gy (V₃₀ to V₅₀) were lower for the rectum in IMRT plans. The volume of normal tissue receiving at least 2 Gy (V₂) was significantly higher in IMRT plans compared with 3D-CRT, whereas at high dose levels (V₃₀) it was significantly lower.

Conclusion

Compared to 3D-CRT, IMRT showed significantly better results regarding dose conformity (p?=?0.012) and bowel sparing at dose levels above 30 Gy (p?=?0.012). Thus, dose escalation in the radiotherapy of pelvic Ewing’s sarcoma can be more easily achieved using IMRT.     

Improvement in plan quality after Implementation of clinical goals in a large network of cancer centers

Clinical Goals (CG) is a tool available in the Varian Eclipse planning system to objectively and visually evaluate the quality of treatment plans based upon user-defined dose-volume parameters. We defined a set of CG for Stereotactic Radiosurgery (SRS) and Intensity-Modulated Radiotherapy (IMRT) based on published data and guidelines and implemented this in a network of cancer centers in India (American Institute of Oncology). A dosimetric study was performed to compare brain SRS and breast IMRT plan quality before and after CG implementation.The CG defined for SRS plans were target V_100% ≥ 98%, dose gradient measure (GM) ≤ 0.5 cm, conformity index (CI) 1.0 to 1.2. For breast IMRT plans, CG defined target V_100% ≥ 97%, V_95% ≥ 95%, V_107% ≤ 2%, V_105% ≤ 10%, and D_max ≤ 2.4 Gy. Dose limits to organs-at-risk (OAR) were summarize in supplemental materials. Twenty brain SRS and 10 breast IMRT treatment plans that were previously delivered on patients were selected and re-planned using CG. The pre and postoptimized plan parameters were compared using student t-tests.For brain SRS plans, the V₁₀₀, GM, and CI for the pre- and post-Clinical-Goals plans were 93.22% ± 7.2% vs 97.96% ± 0.29% (p = 0.009), 0.63 ± 0.16 vs 0.42 ± 0.05 (p < 0.001) and 1.07 ± 0.18 vs 1.06 ± 0.06 (p = 0.79), respectively. There were no differences in max dose to OARs. In breast IMRT plans, the target V_107% for pre and postimplemented plans were 16.50% ± 10.98% vs 0.32% ± 0.32%, respectively (p = 0.001). The average target V_105% were 44.00% ± 15.72% and 8.69% ± 4.53%, respectively (p < 0.001). No differences were found in the average target V_100% (p = 0.128) and V_95% (p = 0.205). The average target D_max were 112.28% ± 1.59% and 109.14% ± 0.73%, respectively (p < 0.001). There were only minor differences in doses to OARs.The implementation of CG in Varian Eclipse significantly improved SRS and IMRT plan quality with enhanced coverage, dose GM, and CI without increased dose to OARs.     

铅门跟随技术与铅门固定技术在直肠癌术前调强放疗中的剂量学比较

目的 研究固定射野动态调强放疗铅门跟随技术与铅门固定技术在直肠癌术前调强放疗中的剂量学差异.方法 采用两种治疗技术对10例直肠癌术前患者设计治疗计划.在95%体积的计划靶区(PTV)和计划肿瘤区(PGTV)满足处方剂量的前提下,尽量降低危及器官的剂量.比较两组治疗计划的剂量-体积直方图,评估靶区及危及器官的剂量分布.分别将两组治疗计划用电离室矩阵2D-Array 729和OCTAVIUS(PTW)模体进行剂量验证.结果 两组计划的靶区均达到临床处方剂量的要求.PTV和PGTV的最大剂量与平均剂量差异无统计学意义.铅门跟随动态调强计划中全身的V₅、V₁₀、V₂₀、V₃₀、V₄₀、D_mean以及双侧股骨头、膀胱、小肠的V₁₀、V₂₀、V₃₀和D_mean均低于铅门固定动态调强计划的相应值,差异有统计学意义(t=-2.32~12.24,P<0.05);双侧股骨头、膀胱、小肠的V₄₀以及D_max差异无统计学意义.采用γ-2D分析两组计划的通过率,两组计划均通过剂量验证.结论 直肠癌术前放疗患者采用固定射野动态调强放疗铅门跟随技术与铅门固定技术两种技术,其靶区和危及器官受量均能满足临床治疗要求,而铅门跟随技术能够更好地降低正常组织和危及器官的低剂量照射.     

早期乳腺癌保乳术后仰卧及俯卧位调强放疗的剂量学比较

目的 比较早期乳腺癌保乳术后仰卧位与俯卧位调强治疗计划靶区和危及器官的剂量学差异.方法 选取15例接受保乳术后放疗的大乳腺及乳腺下垂的左侧乳腺癌患者,分别进行仰卧位及俯卧位CT定位扫描,利用相同优化条件分别进行切线2野调强治疗计划设计.比较2种不同体位计划的靶区剂量分布、心脏、左肺及右侧乳腺受照剂量和体积,以及机器跳数的差异.结果 俯卧位调强计划适形度指数(CI)优于仰卧位计划(0.79±0.05 vs. 0.72±0.04,W=138,P<0.01),均匀性指数(HI)也优于仰卧位计划(1.09±0.01 vs. 1.12±0.02,t=-4.7,P<0.01).俯卧位计划靶区接受95%处方剂量照射的百分体积(V_95%)、最小剂量(D_min)大于仰卧位计划(t=7.1、6.4,P<0.01),平均剂量(D_mean)大于仰卧位计划(W=153,P<0.01),最大剂量(D_max)小于仰卧位计划(t=-3.6,P<0.01).仰卧位计划的右乳接受5 Gy照射的百分体积(V₅)小于俯卧位计划(W=160,P<0.01),心脏接受30 Gy照射的百分体积(V₃₀)大于俯卧位计划(t=5.4,P<0.01),心脏平均剂量(D_mean)、左肺接受20和5 Gy照射的百分体积(V₂₀、V₅)明显大于俯卧位计划(W=133、120、120,P<0.01).机器跳数间差异无统计学意义.结论 对于大乳腺及乳腺下垂乳腺癌患者,保乳术后俯卧位调强计划与仰卧位调强计划相比,靶区剂量分布更均匀,心、肺受照射剂量和体积明显减少.