肺肿瘤在线与离线结合锥形束CT图像引导放疗的可行性研究

目的 探讨肺肿瘤在、离线结合锥形束CT(CBCT)图像引导放疗的可行性.方法 14例行三维适形放疗的肺肿瘤患者入组.放疗前后分别行在线CBCT扫描1次,并与计划CT图像配准,记录各个方向的配准差值.放疗前后配准获得的平移矢量分别作为分次间误差和分次内误差,利用CTV外放公式分别计算未行在线校正以及在线校正后的cTV外放.分别以0.5、1.5 mm为允许的最大残余系统摆位误差,计算预测总系统摆位误差所需的最少CBCT图像数以及离线校正系统摆位误差后的CTV外放.结果 未行在线校正时,左右、头脚、前后方向上群体化CTV外放分别为5.7、8.0、7.8 mm;每分次放疗均行在线校正时,3个方向上群体化CTV外放分别为2.4、2.4、2.3 mm.分别以0.5 mm或1.5 mm为允许的最大残余系统误差,计算预测系统摆位误差所需的最少CBCT图像数为9套或7套,对系统摆位误差进行离线校正后,左右、头脚和前后方向上群体化CTV外放分别为3.3 mm或3.9 mm、3.7 mm或4.3 mm和3.6 mm或4.3 mm.结论 基于CBCT图像分析的在线校正和离线校正均能明显减小摆位误差,并有助于缩小CTV外放.肺肿瘤患者进行在线、离线相结合的图像引导放疗是可行的.     

锥形束CT图像分析鼻咽癌临床靶区外放的研究

目的:利用在线采集的千伏级锥形束CT(cone beam computed tomo-graphy,CBCT)图像,分析鼻咽癌放疗过程中摆位误差的大小,从而获得临床靶区(clinical target volume,CTV)的合理外放边界.方法:16例鼻咽癌患者均采用三维适形放疗或调强放疗.放疗过程中以传统的热塑面膜固定头颈部,激光灯摆位.分次放疗前患者在治疗床上进行CBCT扫描,并将CBCT图像与计划CT图像进行在线配准,根据配准得到的平移矢量调整治疗床的位置,从而修正摆位误差,并分别记录各个方向上平移矢量.结果:16例患者共计160组配准数据.为满足至少95%放疗分次的CTV接受处方剂量,计划靶区各方向上的外放间距均为4 mm.结论:鼻咽癌三维适形调强放疗时具有一定的摆住误差.基于千伏级CBCT图像分析的在线校正方法能减小该摆位误差,并有助于确定合适的CTV外放.     

利用CBCT联合六自由度治疗床研究宫颈癌术后放疗摆位误差及CTV外放边界

目的 利用千伏级CBCT联合HexaPOD evo RT六自由度治疗床研究宫颈癌术后盆腔放疗摆位误差,推算CTV外放边界。方法 采用医科达AXESSE^TM直线加速器治疗宫颈癌术后患者17例。所有患者常规摆位后CBCT,治疗床在线校正后再次CBCT,治疗后再次CBCT,分别获得XVI。与计划CT图像配准后,即可获得患者左右、上下、前后方向平移及旋转误差,分析摆位误差及CTV外放边界。采用配对t检验差异。结果 CBCT校正前后均为304次,治疗后68次。所有患者分次间左右、上下、前后方向平移误差和旋转误差经在线校正后均减小,校正前/后绝对值的平均值分别为2.42 mm/0.42 mm、3.55 mm/0.47 mm、3.26 mm/0.27 mm和1.24°/0.24°、0.70°/0.32°、0.57°/0.12°(P=0.036、0.000、0.000、0.002、0.000、0.004)。考虑分次内摆位误差影响,治疗床校正后CTV外扩边界在左右、上下、前后方向上分别为2.24、3.32、2.20 mm。结论 宫颈癌术后患者CBCT联合六维治疗床在线校正可明显减小6个方向分次间摆位误差,且能缩小CTV外放边界。     

在线千伏级锥形束CT引导前列腺癌调强放疗摆位误差研究

目的 通过千伏级锥形束CT(KV-CBCT)在线测量前列腺癌调强放疗的摆位误差及图像引导后的残余误差,确定前列腺癌患者外照射治疗计划中CTV外放PTV的边界大小.方法 入选7例接受根治性调强放疗的前列腺癌患者,每例患者每周至少行KV-CBCT在线校正治疗体位2次.采用常规皮肤标记激光对位后采集图像,将所获得CBCT与计划CT图像进行灰度自动配准.计算摆位误差并进行在线评价,若摆位误差＞2 mm则调整治疗床进行纠正.纠正后重新采集CBCT图像进行配准,计算残余误差.根据摆位误差和残余误差分别计算纠正前后临床靶体积(CTV)至计划靶体积(PTV)外放边界大小.结果 共获取197幅KV-CBCT图像.7例患者左右、头脚、前后方向系统误差和随机误差分别为3.1和2.1、1.5和1.8、4.2和3.7 mm,外放边界分别为9.3、5.1、13.0 mm.经KV-CBCT引导纠正后左右、头脚、前后方向系统残余误差和随机残余误差分别为1.1和0.9、0.7和1.1、1.1和1.3 mm,外放边界分别为3.4、2.5、3.7 mm.结论 在线KV-CBCT引导放疗技术可减小前列腺癌患者摆位误差、提高摆位精度,CTV外放PTV边界可缩小至3～4 mm.     

利用锥形束CT图像分析非小细胞肺癌临床靶区外放的研究

目的 探讨非小细胞肺癌三维适形放射治疗临床靶区的外放范围。方法 8例非小细胞肺癌患者均采用三维适形放疗或调强放疗。分次放疗前、后患者在治疗床上进行锥形束CT扫描,并将锥形束CT图像与计划CT图像进行在线配准,根据配准得到的平移矢量调整治疗床的位置,从而修正摆位误差,并分别记录各个方向上平移矢量。结果 8例患者共计160组配准数据。如果放射治疗过程中未进行在线图像引导校正,在实际应用中临床靶区外放10.9 mm;如果每次放射治疗均进行在线图像引导校正,在实际应用中临床靶区外放2.2 mm。结论 非小细胞肺癌三维适形调强放疗时具有一定的摆位误差。基于锥形束CT图像分析的在线校正方法能减小该摆位误差,并有助于确定合适的临床靶区外放。     

兆伏级锥形束CT在食管癌放射治疗中摆位误差的分析

目的:评估兆伏级锥形束CT(CBCT)图像引导食管癌三维适形放射治疗(3DRT)的摆位误差,计算临床靶体积(CTV)到计划靶体积(PTV)的外放边界.方法:用西门子配备有MVision兆伏级CBCT的直线加速器,对32例三维适形放疗(3DRT)的食管癌患者,在治疗的5周内每周1次,分别对治疗前、摆位误差调整后行CBCT扫描.通过计划CT图像与治疗图像进行匹配,获取左右(X)、头脚(Y)、前后(Z)的摆位误差,计算CTV到PTV的外放边界.结果:32例患者共获取320幅CBCT图像.在校正前,患者的摆位误差分别为左右(-1.25±3.28)mm、头脚(-0.63±5.00)mm、前后(0.84±3.26) mm;根据Van等提供的公式,CTV至PTV的外放边界为左右9.38mm,头脚12.28mm,前后7.70mm.摆位误差调整后:误差分别为左右(0.19±1.89) mm、头脚(-0.56±3.71)mm和前后(0.53±1.54)mm,与调整前相比在三维方向均有降低,且有统计学差异(P＜0.05).摆位误差调整后PTV外扩边界,左右3.68mm,头脚4.83mm,前后4.24mm.结论:通过CBCT获取食管癌患者的摆位误差并对其进行纠正,能显著降低分次间的摆位误差,提高放疗精确度,减小PTV外放边界.     

非小细胞肺癌在线配准剂量残差回归式离线补偿技术的初步探讨

目的:探讨非小细胞肺癌(NSCLC)锥形束CT(CBCT)图像引导在线摆位校正后,对残余误差导致的剂量学差异进行离线补偿的可行性.方法:2例NSCLC患者入组.每分次放疗前进行在线CBCT图像引导摆住校正,然后对在线CBCT图像数据进行回顾性分析.离线配准CBCT图像与计划CT图像,对比分析配准后CBCT图像上靶区的剂量分布与初始计划的差异,如果发现明显的剂量缺陷区域,则通过逆向调强技术制定新的放疗计划,下一分次放疗按新计划执行.结果:NSCLC患者经在线图像引导摆位校正后,仍然有多分次靶区存在欠剂量区,通过逆向调强技术可以给予欠剂量区以高剂量,从而实现对前次治疗所欠剂量的补偿.结论:离线逆向调强补量技术作为在线图像引导技术的补充,能够对在线图像引导后配准残差导致的剂量学误差进行有效补偿,有望进一步减小靶区外放,实现与每日计划相同的剂量学目标.     

保留乳房术后放疗锥形束CT引导系统摆位误差预测的可行性研究

目的:探讨保留乳房术后放疗过程中应用初始分次放疗的锥形束CT引导数据预测和校正系统摆位误差的可行性。方法:20例保留乳房术后行三维适形放疗和调强放疗的患者入组。每分次放疗前行在线CBCT扫描,与计划CT图像配准,记录前后、头脚和左右方向的配准差值。分别以初始5次和10次差值的平均值作为预测值校正后续治疗的系统摆位误差。校正系统摆位误差后的残余误差定义为每日实际偏差值与系统预测值之间的差值。比较未进行在线摆位校正、应用5次校正法或10次校正法进行在线摆位校正放疗过程中的群体化系统、随机摆位误差以及三维残余误差。结果:未校正组在前后、头脚和左右方向上的群体化系统摆位误差分别为2.91、3.38和2.33mm,群体化随机摆位误差分别为2.56、2.87和2.51mm;应用5次校正法在前后、头脚和左右方向上的群体化系统摆位误差分别为2.26、2.03和1.96mm,群体化随机摆位误差分别为2.48、2.80和2.37mm;应用10次校正法在前后、头脚和左右方向上的群体化系统摆位误差分别为2.37、1.66和1.51mm,群体化随机摆位误差分别为2.39、2.70和2.46mm。平均三维残余误差分别为6.1(未校正)、4.9(5次校正)和4.7mm(10次校正)。与未进行在线摆位校正比较,应用5次校正法,平均三维残余误差>6mm的患者比例由40%降低至25%,>7mm的患者比例由30%降低至5%,放疗分次比例由34.19%降低至19.70%。10次校正法与5次校正法相比,未显示出明显的改善。结论:利用初始5次放疗在线CBCT配准差值预测并校正系统摆位误差在一定程度上改善了每日摆位准确度。然而,在开发出更准确的图像引导策略之前,每日进行在线摆位校正仍然是有必要的。     

锥形束CT测量食管癌放射治疗的摆位误差

目的 利用锥形束CT在线研究食管癌放疗时的摆位误差,计算CTV到PTV的外放边界(MPTV).方法 应用医科达Synergy系统对食管癌患者治疗11例148次,分别在首次摆位后、摆位误差纠正后及治疗后行CBCT扫描,共获取444个CBCT信息,通过系统配有的匹配功能,获取的CBCT图像与计划CT图像相匹配,获取患者左右(X)、头脚(Y)和前后(Z)等3个方向的线性摆位误差,分析其摆位误差.结果 11例患者共行444次CBCT,首次摆位后CBCT扫描,系统误差(均数)±随机误差(标准差)在X、Y、Z方向上分别为(-0.17±3.62)、(1.82±3.97)、(-2.34±2.10)mm,误差纠正后再次行CBCT,结果显示摆位误差明显缩小(P＜0.05)。与纠正后比较,治疗后摆位误差增大,差异有统计学意义(P＜0.05)。纠正前X、Y、Z轴上MPTV分别为8.49、9.09、5.67mm,纠正后X、Y、Z方向的MPTV分别为1.80、2.47、2.21mm。结论本组病例食管癌放疗时Y方向摆位误差最大,X方向次之,Z方向最小;分次内误差在食管肿瘤治疗过程中变化明显,这在设计治疗计划时应予以考虑;通过CBCT获取食管癌患者的摆位误差并对其进行纠正,能显著降低分次间的摆位误差,提高放疗精确度,减小PTV外放边界.     

肝癌术后简化调强放疗临床靶体积误差的锥形束CT分析

目的 通过锥形束CT (CBCT)分析肝癌患者术后简化调强放疗分次间和分次内的临床靶体积(CTV)误差。方法 12例肝癌患者放疗前、后均行CBCT。在瘤床放置金属标记,配准框包全所有金属标记,不包括肋骨、椎体等骨质,使用自动骨性配准。若放疗前平移误差>3 mm和(或)旋转误差>3°则行在线校位后重复CBCT。12例患者共行214次CBCT成111组数据,111组可计算分次间左右(x)、头脚(y)、前后(z)方向CTV误差,70组可计算分次内CTV误差。计划靶体积(PTV)边界计算公式为2.0∑+0.7σ(∑为系统误差,σ为随机误差)。结果 x、y、z方向上分次间CTV平移误差分别为 －0.03、－0.43、1.02 mm,∑分别为1.50、5.89、1.97 mm,σ分别为1.76、4.13、2.42 mm;分次内平移误差分别为0.04、0.86、－0.46 mm,∑分别为0.46、1.14、0.31 mm,σ分别为0.95、1.38、0.91 mm。PTV边界在x、y、z方向上分别为4.5、15.0、5.8 mm。结论 肝癌患者简化调强放疗时CTV误差不可避免,使用术中放置瘤床金属标记行CBCT获得的数据真实准确。     

图像引导调强放疗头颈部肿瘤摆位误差对靶区外扩边界大小的影响

目的 利用锥形束CT (CBCT)图像分析跟踪头颈部恶性肿瘤调强放疗分次治疗间和分次治疗内肿瘤中心误差情况,并以此误差探讨临床靶体积(CTV)外放边界大小.方法 51例头颈部肿瘤经图像引导调强放疗,其中治疗前CBCT引导464次,治疗后CBCT 126次.根据CBCT图像与计划CT图像匹配实现在线和离线分析得到位移偏差.按不同在线校正次数(15次、11～15次、5～10次)和3个方向偏差依照双模型参数计算CTV外扩边界大小.结果 464次摆位未校正的左右、前后、上下方向偏差分别为0.37、-0.43、0.47 mm,CTV外扩边界分别为6.41、6.15、7.10 mm;校正后偏差分别为0.08、-0.03、0.03 mm,CTV外扩边界分别为1.78、1.80、1.97 mm.在线校正次数>15次,11～15次,5～10次者左右、前后、上下方向外扩分别为3.8、3.8、4.0 mm,4.0、4.0、5.0 mm,5.4、5.2、6.1 mm.结论 利用CBCT引导头颈部恶性肿瘤的调强放疗可确定确切的CTV外扩边界大小,保证肿瘤区域得到准确剂量和减小正常组织受量.

Abstract：

Objective To determine the planning target volume margins of head and neck cancers treated by image guided radiotherapy (IGRT).Methods 464 sets cone beam computed tomography (CBCT) images before setup correction and 126 sets CBCT images after correction were obtained from 51 head and neck cancer patients treated by IGRT in our department.The systematic and random errors were evaluated by either online or offline correction through registering the CBCT images to the planning CT.The data was divided into 3 groups according to the online correction times.Results The isocenter shift were 0.37 mm±2.37 mm, -0.43 mm±2.30 mm and 0.47 mm±2.65 mm in right-left (RL), anterior-posterior (AP) and superior-inferior (SI) directions respectively before correction, and it reduced to 0.08 mm±0.68 mm, -0.03 mm±0.74 mm and 0.03 mm±0.80 mm when evaluated by 126 sets corrected CBCT images.The planning target volume (PTV) margin from clinical target volume (CTV) before correction were:6.41 mm,6.15 mm and 7.10 mm based on two parameter model, and it reduced to 1.78 mm,1.80 mm and 1.97 mm after correction.The PTV margins were 3.8 mm,3.8 mm,4.0 mm;4.0 mm,4.0 mm,5.0 mm and 5.4 mm,5.2 mm,6.1 mm in RL, AP and SI respectively when online-correction times were more than 15 times, 11-15 times,5-10 times.Conclusions CBCT-based on online correction reduce the PTV margin for head and neck cancers treated by IGRT and ensure more precise dose delivery and less normal tissue complications.     

Image-guided radiotherapy via daily online cone-beam CT substantially reduces margin requirements for stereotactic lung radiotherapy

PURPOSE: To determine treatment accuracy and margins for stereotactic lung radiotherapy with and without cone-beam CT (CBCT) image guidance. METHODS AND MATERIALS: Acquired for the study were 308 CBCT of 24 patients with solitary peripheral lung tumors treated with stereotactic radiotherapy. Patients were immobilized in a stereotactic body frame (SBF) or alpha-cradle and treated with image guidance using daily CBCT. Four (T1) or five (T2/metastatic) 12-Gy fractions were prescribed to the planning target volume (PTV) edge. The PTV margin was >or=5 mm depending on a pretreatment estimate of tumor excursion. Initial daily setup was according to SBF coordinates or tattoos for alpha-cradle cases. A CBCT was performed and registered to the planning CT using soft tissue registration of the target. The initial setup error/precorrection position, was recorded for the superior-inferior, anterior-posterior, and medial-lateral directions. The couch was adjusted to correct the tumor positional error. A second CBCT verified tumor position after correction. Patients were treated in the corrected position after the residual errors were 相似文献   

千伏级锥形束CT勾画心脏可行性研究

目的 研究千伏级锥形束CT (CBCT)进行心脏勾画的可行性,并探讨计划CT上进行心脏勾画的外放标准。方法 选取接受放疗的早期非小细胞肺癌患者15例,每次治疗前拍摄CBCT进行摆位误差纠正,利用每位患者前10次CBCT进行研究。在每次CBCT图像上按照统一标准进行心脏勾画,比较基于计划CT和CBCT心脏勾画的差异以及不同扫描时机CBCT勾画心脏的重复性,测量基于计划CT获得心脏各个轴向外放距离。结果 15例患者计划CT获得的心脏体积均小于CBCT的(平均值为588、717 cm³,P=0.000),不同次数CBCT勾画的心脏体积基本相当(P=0.999),相同解剖层面与首次CBCT图像心脏范围的重复性达0.985±0.020,各套间也相似(P=0.070)。基于计划CT勾画心脏时外扩距离左、右方向分别为(10.5±2.8) 、(5.9±2.8) mm,上、下方向分别为(2.2±1.6)、(3.3±2.2) mm,前、后方向分别为(6.7±1.1)、(4.5±2.5) mm。结论 基于CBCT进行心脏勾画是可行的;未配备CBCT进行心脏勾画时建议在计划CT基础上对心脏左、右侧外放11、6 mm,上、下方向外放3、4 mm,前、后方向外放7、5 mm。     

A moving target: Image guidance for stereotactic body radiation therapy for early-stage non-small cell lung cancer

PurposePrecise patient positioning is critical due to the large fractional doses and small treatment margins employed for thoracic stereotactic body radiation therapy (SBRT). The goals of this study were to evaluate the following: (1) the accuracy of kilovoltage x-ray (kV x-ray) matching to bony anatomy for pretreatment positioning; (2) the magnitude of intrafraction tumor motion; and (3) whether treatment or patient characteristics correlate with intrafraction motion.Methods and MaterialsEighty-seven patients with lung cancer were treated with SBRT. Patients were positioned with orthogonal kV x-rays matched to bony anatomy followed by cone-beam computed tomography (CBCT), with matching of the CBCT-visualized tumor to the internal gross target volume obtained from a 4-dimensional CT simulation data set. Patients underwent a posttreatment CBCT to assess the magnitude of intrafraction motion.ResultsThe mean CBCT-based shifts after initial patient positioning using kV x-rays were 2.2 mm in the vertical axis, 1.8 mm in the longitudinal axis, and 1.6 mm in the lateral axis (n = 335). The percentage of shifts greater than 3 mm and 5 mm represented 39% and 17%, respectively, of all fractions delivered. The mean CBCT-based shifts after treatment were 1.6 mm vertically, 1.5 mm longitudinally, and 1.1 mm laterally (n = 343). Twenty-seven percent and 10% of shifts were greater than 3 mm and 5 mm, respectively. Univariate and multivariable analysis demonstrated a significant association between intrafraction motion with weight and pulmonary function.ConclusionsKilovoltage x-ray matching to bony anatomy is inadequate for accurate positioning when a conventional 3-5 mm margin is employed prior to lung SBRT. Given the treatment techniques used in this study, CBCT image guidance with a 5-mm planning target volume margin is recommended. Further work is required to find determinants of interfraction and intrafraction motion that may help guide the individualized application of planning target volume margins.     

Cone beam CT (CBCT) evaluation of inter- and intra-fraction motion for patients undergoing brain radiotherapy immobilized using a commercial thermoplastic mask on a robotic couch

Patients receiving fractionated intensity-modulated radiation therapy (IMRT) for brain tumors are often immobilized with a thermoplastic mask; however, masks do not perfectly re-orient the patient due to factors including the maximum pressure which can be applied to the face, deformations of the mask assembly, patient compliance, etc. Consequently, ~3-5mm PTV margins (beyond the CTV) are often recommended. We aimed to determine if smaller PTV margins are feasible using mask immobilization coupled with 1) a gantry mounted CBCT image guidance system and 2) position corrections provided by a full six-degree of freedom (6-DOF) robotic couch. A cohort of 34 brain tumor patients was treated with fractionated IMRT. After the mask set-up, an initial CBCT was obtained and registered to the planning CT. The robotic couch corrected the misalignments in all 6-DOF and a pre-treatment verification CBCT was then obtained. The results indicated a repositioning alignment within our threshold of 1.5 mm (3D). Treatment was subsequently delivered. A post-treatment CBCT was obtained to quantify intra-fraction motion. Initial, pre-treatment and post-treatment CBCT image data was analyzed. A total of 505 radiation fractions were delivered to the 34 patients resulting in ~1800 CBCT scans. The initial median 3D (magnitude) set-up positioning error was 2.60 mm. Robotic couch corrections reduced the 3D median error to 0.53 mm prior to treatment. Intra-fraction movement was responsible for increasing the median 3D positioning error to 0.86 mm, with 8% of fractions having a 3D positioning error greater than 2 mm. Clearly CBCT image guidance coupled with a robotic 6-DOF couch dramatically improved the positioning accuracy for patients immobilized in a thermoplastic mask system; however, such intra-fraction motion would be too large for single fraction radiosurgery.     

Assessment of residual error for online cone-beam CT-guided treatment of prostate cancer patients

PURPOSE: Kilovoltage cone-beam CT (CBCT) implemented on board a medical accelerator is available for image-guidance applications in our clinic. The objective of this work was to assess the magnitude and stability of the residual setup error associated with CBCT online-guided prostate cancer patient setup. Residual error pertains to the uncertainty in image registration, the limited mechanical accuracy, and the intrafraction motion during imaging and treatment. METHODS AND MATERIALS: The residual error for CBCT online-guided correction was first determined in a phantom study. After online correction, the phantom residual error was determined by comparing megavoltage portal images acquired every 90 degrees to the corresponding digitally reconstructed radiographs. In the clinical study, 8 prostate cancer patients were implanted with three radiopaque markers made of high-winding coils. After positioning the patient using the skin marks, a CBCT scan was acquired and the setup error determined by fusing the coils on the CBCT and planning CT scans. The patient setup was then corrected by moving the couch accordingly. A second CBCT scan was acquired immediately after the correction to evaluate the residual target setup error. Intrafraction motion was evaluated by tracking the coils and the bony landmarks on kilovoltage radiographs acquired every 30 s between the two CBCT scans. Corrections based on soft-tissue registration were evaluated offline by aligning the prostate contours defined on both planning CT and CBCT images. RESULTS: For ideal rigid phantoms, CBCT image-guided treatment can usually achieve setup accuracy of 1 mm or better. For the patients, after CBCT correction, the target setup error was reduced in almost all cases and was generally within +/-1.5 mm. The image guidance process took 23-35 min, dictated by the computer speed and network configuration. The contribution of the intrafraction motion to the residual setup error was small, with a standard deviation of +/-0.9 mm. The average difference between the setup corrections obtained with coil and soft-tissue registration was greatest in the superoinferior direction and was equal to -1.1 +/- 2.9 mm. CONCLUSION: On the basis of the residual setup error measurements, the margin required after online CBCT correction for the patients enrolled in this study would be approximatively 3 mm and is considered to be a lower limit owing to the small intrafraction motion observed. The discrepancy between setup corrections derived from registration using coils or soft tissue can be due in part to the lack of complete three-dimensional information with the coils or to the difficulty in prostate delineation and requires further study.