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.     

CT与MRI图像融合在头颈部肿瘤放疗靶区勾画中的应用

放射肿瘤学己逐步从常规外照射向立体定向放疗、三维适形放疗、调强放疗等精确放疗发展，而肿瘤靶区边界和正常组织轮廓定义的精确与否己成为肿瘤放疗计划优劣的基础和评估的依据。放疗计划系统解剖结构主要取自于CT，但是CT对软组织分辨率较低，如果仍简单地采用CT图像来定义靶区轮廓，就可能遗漏部分靶体积，增加了肿瘤复发概率。因此对常用CT和MRI利用图像融合配准技术得到融合图像，探讨两种图像在头颈部肿瘤放疗当中对GTV确定的优缺点。[第一段]     

锥形束CT引导自主呼吸控制保乳术后三维适形部分乳腺外照射术腔中银夹位移的研究

目的锥形束CT（CBCT）引导测定术腔中银夹位移以探讨保乳术后三维适形部分乳腺外照射（EB-PBI）临床靶体积（CTV）外扩到计划靶体积（PTV）的边界。方法自主呼吸控制（ABC）辅助行CT模拟定位扫描，获取适度深吸气呼吸控制（mDIBH）状态CT图像，分别勾画和标记术腔中4个选定银夹，并勾画所有银夹构成的术腔作为肉眼靶体积（GTV）。每次照射前获取ABC辅助mDIBH状态下2次CBCT扫描图像。每次获取CBCT图像后先与计划CT图像自动匹配，在自动匹配基础上对选定银夹进行手动匹配。获得选定银夹在左右、上下、前后各个方向的位移数据，依据获取的数据分别计算选定银夹放疗分次内和分次间群体系统误差的标准差和群体随机误差的标准差及总体系统误差和总体随机误差的标准差，依据公式M=2．5∑总＋0．7σ总计算各个选定银夹在各个方向上由CTV外扩到PTV所需要边界大小。结果最上层银夹LAT、LNG、VRT方向由CTV到PTV的外扩边界分别为9．2、6．4、12．0mm，最近胸壁层银夹为8．1、8．0、11．7mm，最外侧银夹为9．8、7．7、12．5mm，最下层银夹为9．8、7．7、12．5mm。结论ABC辅助mDIBH状态下CBCT图像与计划CT图像自动加手动配准可准确显示银夹位移，为EB-PBI的PTV边界确定提供了依据。     

锥形束CT测量鼻咽癌放疗计划靶区外放研究

放疗靶区中为了弥补靶区运动和摆位误差等不确定因素而设定了临床靶区（CTV）-计划靶区（PTV）和危及器官计划靶区（PORV）外放范围。笔者通过17例鼻咽癌患者应用锥形束CT（CBCT）精确分析靶区运动和摆位误差,建立群体化CTV-PTV和PORV外放。     

应用主动呼吸控制系统结合图像引导放疗治疗乳腺癌的对比研究

目的 研究主动呼吸控制系统(ABC)结合图像引导放疗治疗乳腺癌的意义。方法 选择我院20例乳腺癌保乳术后患者,随机分为两组进行放射治疗,分别对门控组患者配合ABC系统在2/3呼吸深度屏气(BH)状态及对照组患者在自由呼吸(FH)状态下进行CT定位扫描,应用ELECTA Precise-Paln和Pinnicle3进行治疗计划设计,每次治疗前后均对每组患者进行CBCT扫描,利用XVI系统得出左右(x)、头脚(y)、前后(z)方向误差并记录,根据误差调整治疗床位置后治疗。评价急性放射皮肤反应,并作出FH和BH状态下剂量学分析。结果 对照组乳腺癌患者治疗前后CBCT图像与定位图像比较在左右、头脚、前后三个方向上的误差分别为(0.37±0.13)、(0.29±0.32)、(-0.44±0.45)和(0.10±0.07)、(0.08±0.07)、(-0.13±0.19);门控组乳腺癌患者治疗前后CBCT图像与定位图像比较在左右、头脚、前后三个方向上的误差分别为(0.3±0.09)、(0.71±0.34)、(0.58±0.25)和(0.09±0.06)、(0.24±0.11)、(0.15±0.08)。门控组患者患侧肺V₂₀、患侧肺MLD、心脏V₃₀和心脏平均受量D_mean均优于对照组患者;两组患者急性放射性皮肤反应结果相近。结论 主动呼吸控制系统结合图像引导放射治疗是满足乳腺癌临床放疗要求的最佳方法,不但可以减少呼吸运动对靶区的影响,还可以减少危及器官的受照体积和剂量,进而提高放疗精度。     

主动呼吸控制系统对肝脏肿瘤放疗靶区勾画设计影响的研究

目的 观察主动呼吸控制（active breathing control,ABC）膈肌在人体纵轴方向的运动规律,探讨计划靶区（planning targetvolume,PTV）的设计。方法对15例肝脏肿瘤患者应用ABC,同时用ElektaSynery加速器配备的XVI系统中的MotionView功能采集连续图像150张,然后测量膈肌的运动幅度。结果15例患者经训练后均能达到ABC的要求,配合ABC可很好地控制膈肌的运动,在一次屏气的前3／4时相,膈肌在人体纵轴方向的位移幅度不超过1mm,但是在屏气的后1／4时相,膈肌在人体纵轴方向的位移幅度较大,在3．12-5．00mm,中位值为4mm。结论ABC技术可以很好地控制膈肌的运动,可减少放疗过程中肿瘤靶区的位移,进而提高3DCRT的精度。     

锥形束CT图像引导放疗系统的质量保证

全文综述了锥形束CT图像引导放疗系统用于校正器官移动和摆位带来的误差时所需要的质量保证(QA)内容,包括安全性QA、图像质量QA、硬件参数QA、几何特性QA.     

图像引导的放射治疗在头颈部肿瘤

随着图像引导的放射治疗(image-guided radiotherapy,IGRT)技术的出现,肿瘤放射治疗进入一个精确化、个体化和自适应性的时代.目前该技术在多种肿瘤治疗中得以应用.本文就其在头颈部肿瘤治疗中的作用、特殊性和具体应用作一综述,以期待其能更好地为开展头颈部肿瘤的IGRT临床研究提供帮助.     

CT模拟确定肺癌靶区体积的影响因素研究

为准确确定肺癌的三维形状及体积,为三维适形放疗提供真实准确的影像信息,为实施精确放疗,笔者进行了CT模拟确定靶区体积的影响因素研究。一、材料与方法1.材料:通过一变速电机控制靶区运动速度,模拟靶区随呼吸运动的频率;通过一偏心轮的离心程度模拟肺呼吸时靶区的最大移动幅度。模体内一圆球形及以一正方体靶区     

Reproducibility of lung tumor position and reduction of lung mass within the planning target volume using active breathing control (ABC)

PURPOSE: The active breathing control (ABC) device allows for temporary immobilization of respiratory motion by implementing a breath hold at a predefined relative lung volume and air flow direction. The purpose of this study was to quantitatively evaluate the ability of the ABC device to immobilize peripheral lung tumors at a reproducible position, increase total lung volume, and thereby reduce lung mass within the planning target volume (PTV). MATERIALS AND METHODS: Ten patients with peripheral non-small-cell lung cancer tumors undergoing radiotherapy had CT scans of their thorax with and without ABC inspiration breath hold during the first 5 days of treatment. Total lung volumes were determined from the CT data sets. Each peripheral lung tumor was contoured by one physician on all CT scans to generate gross tumor volumes (GTVs). The lung density and mass contained within a 1.5-cm PTV margin around each peripheral tumor was calculated using CT numbers. Using the center of the GTV from the Day 1 ABC scan as the reference, the displacement of subsequent GTV centers on Days 2 to 5 for each patient with ABC applied was calculated in three dimensions. RESULTS: With the use of ABC inspiration breath hold, total lung volumes increased by an average of 42%. This resulted in an average decrease in lung mass of 18% within a standard 1.5-cm PTV margin around the GTV. The average (+/- standard deviation) displacement of GTV centers with ABC breath hold applied was 0.3 mm (+/- 1.8 mm), 1.2 mm (+/- 2.3 mm), and 1.1 mm (+/- 3.5 mm) in the lateral direction, anterior-posterior direction, and superior-inferior direction, respectively. CONCLUSIONS: Results from this study indicate that there remains some inter-breath hold variability in peripheral lung tumor position with the use of ABC inspiration breath hold, which prevents significant PTV margin reduction. However, lung volumes can significantly increase, thereby decreasing the mass of lung within a standard PTV.     

The reproducibility of organ position using active breathing control (ABC) during liver radiotherapy

Purpose: To evaluate the intrafraction and interfraction reproducibility of liver immobilization using active breathing control (ABC).

Methods and Materials: Patients with unresectable intrahepatic tumors who could comfortably hold their breath for at least 20 s were treated with focal liver radiation using ABC for liver immobilization. Fluoroscopy was used to measure any potential motion during ABC breath holds. Preceding each radiotherapy fraction, with the patient setup in the nominal treatment position using ABC, orthogonal radiographs were taken using room-mounted diagnostic X-ray tubes and a digital imager. The radiographs were compared to reference images using a 2D alignment tool. The treatment table was moved to produce acceptable setup, and repeat orthogonal verification images were obtained. The positions of the diaphragm and the liver (assessed by localization of implanted radiopaque intra-arterial microcoils) relative to the skeleton were subsequently analyzed. The intrafraction reproducibility (from repeat radiographs obtained within the time period of one fraction before treatment) and interfraction reproducibility (from comparisons of the first radiograph for each treatment with a reference radiograph) of the diaphragm and the hepatic microcoil positions relative to the skeleton with repeat breath holds using ABC were then measured. Caudal-cranial (CC), anterior-posterior (AP), and medial-lateral (ML) reproducibility of the hepatic microcoils relative to the skeleton were also determined from three-dimensional alignment of repeat CT scans obtained in the treatment position.

Results: A total of 262 fractions of radiation were delivered using ABC breath holds in 8 patients. No motion of the diaphragm or hepatic microcoils was observed on fluoroscopy during ABC breath holds. From analyses of 158 sets of positioning radiographs, the average intrafraction CC reproducibility (σ) of the diaphragm and hepatic microcoil position relative to the skeleton using ABC repeat breath holds was 2.5 mm (range 1.8–3.7 mm) and 2.3 mm (range 1.2–3.7 mm) respectively. However, based on 262 sets of positioning radiographs, the average interfraction CC reproducibility (σ) of the diaphragm and hepatic microcoils was 4.4 mm (range 3.0–6.1 mm) and 4.3 mm (range 3.1–5.7 mm), indicating a change of diaphragm and microcoil position relative to the skeleton over the course of treatment with repeat breath holds at the same phase of the respiratory cycle. The average population absolute intrafraction CC offset in diaphragm and microcoil position relative to skeleton was 2.4 mm and 2.1 mm respectively; the average absolute interfraction CC offset was 5.2 mm. Analyses of repeat CT scans demonstrated that the average intrafraction excursion of the hepatic microcoils relative to the skeleton in the CC, AP, and ML directions was 1.9 mm, 0.6 mm, and 0.6 mm respectively and the average interfraction CC, AP, and ML excursion of the hepatic microcoils was 6.6 mm, 3.2 mm, and 3.3 mm respectively.

Conclusion: Radiotherapy using ABC for patients with intrahepatic cancer is feasible, with good intrafraction reproducibility of liver position using ABC. However, the interfraction reproducibility of organ position with ABC suggests the need for daily on-line imaging and repositioning if treatment margins smaller than those required for free breathing are a goal.     

Short-term and long-term reproducibility of lung tumor position using active breathing control (ABC)

PURPOSE: To evaluate the short-term and long-term reproducibility of lung tumor position for scans acquired using an active breathing control (ABC) device. METHODS AND MATERIALS: Ten patients with lung cancer were scanned over three sessions during the course of treatment. For each session, two scans were acquired at deep inhale, and one scan each at half of deep inhale and at exhale. Long-term reproducibility was evaluated by comparing the same breathing state scans from two sessions, with setup variation removed by skeletal alignment. Tumor alignment was based on intensity matching of a small volume around the tumor. For short-term reproducibility, the two inhale volumes from the same session were compared. RESULTS: For the short-term reproducibility, the mean and the standard deviation (SD) of the displacement of the center of tumor were 0.0 (1.5) mm in anteroposterior (AP), 0.3 (1.4) mm in superior/inferior (SI), and 0.2 (0.7) mm in right/left (RL) directions. For long-term reproducibility, the mean (SD) were -1.3 (3.1) mm AP, -0.5 (3.8) mm SI, and 0.3 (1.6) mm RL for inhale and -0.2 (2.8) mm AP, 0.2 (2.1) mm SI, and -0.7 (1.1) mm RL for exhale. CONCLUSION: The ABC device demonstrates very good short-term and long-term reproducibility. Increased long-term variability in position, primarily in the SI and AP directions, indicates the role of tumor-directed localization in combination with breath-held immobilization.     

适度深吸气呼吸控制状态下全乳腺正向调强外照射的剂量学研究

目的:评估适度深吸气(mDIBH)呼吸控制状态下乳腺癌保留乳房术后全乳正向调强外照射的剂量学优势。方法:入组的18例乳腺癌保留乳房术患者,在自主呼吸控制技术配合下进行CT定位扫描,获得1幅自由呼吸(FB)及1幅mDIBH的图像。采用Pinnacle7.4f治疗计划系统,分别在FB的图像上和mDIBH的图像制定全乳腺正向调强外照射计划,比较2个计划的正常组织和靶区的受照射情况。结果:FB状态下的计划靶区剂量均匀性及适形性与mDIBH状态下的计划相似(1.08±0.01 vs 1.09±0.01,P=0.776;0.59±0.08 vs 0.60±0.04,P=0.821);FB状态下患侧肺V20和V30分别为(13.07±3.93)%和(11.68±3.90)%,均较mDIBH状态下的(9.75±3.58)%和(8.12±3.23)%高,P=0.000。9例左侧乳腺癌患者在FB状态下心脏的V20和V30分别为(5.42±3.21)%和(3.70±2.84)%,均较mDIBH状态下的(2.73±1.95)%和(1.48±0.22)%高,P<0.05。结论:与FB状态相比,mDIBH呼吸控制状态下可减少乳腺癌保留乳房术后全乳腺正向调强外照射的肺和心脏受照射剂量。     

肝癌碘油标记图像对锥形束CT图像配准方法及靶区外放的影响

目的 分析碘油标记的肝癌图像对有无图像引导放疗(IGRT)中不同配准方法及靶区外放范围的影响。方法 5例经动脉灌注化疗栓塞(TACE)后放疗的肝癌患者,在医科达IGRT联合主动呼吸控制(ABC)系统下,每日治疗前用锥形束CT (CBCT)采集图像。根据靶区及邻近器官进行治疗计划CT图像和CBCT容积图像配准,记录左右、上下、前后方向偏移值(CBCT₁),并校正摆位误差;纠正后再次CBCT扫描与CT图像配准(CBCT₂);治疗结束后,再次CBCT扫描与CT图像配准(CBCT₃)。用SPSS软件计算CTV-PTV的外放边界,对CBCT₁、CBCT₂、CBCT₃比较结果行配对t检验。结果 CBCT₁和CBCT₂及CBCT₃在左右、上下、前后方向偏移值不同,分别为0.254、－0.612、0.314 cm和0.020、0.014、－0.064 cm及－0.004、0.042、－0.040 cm。CTV-PTV外放边界无IGRT时左右、上下、前后方向分别为0.96、0.96、0.83 cm,有IGRT时为0.67、0.68、0.58 cm。离线分析放疗过程中CBCT下碘油图像形态变化发现,即使在靶区(碘油)精确配准下,肝脏在上下方向、椎体在3个方向上仍有很大偏移值。结论 IGRT技术带来的CTV-PTV外放减小约3 mm。内靶区无标记物患者,CTV-PTV外放应将肿瘤上下方向误差及椎体误差考虑在内。配准时如果单纯以肝缘图像为参考配准点,图像配准将会有很大不确定性。     

Online planning and delivery technique for radiotherapy of spinal metastases using cone-beam CT: image quality and system performance

PURPOSE: To assess the feasibility of an online strategy for palliative radiotherapy (RT) of spinal bone metastasis, which integrates imaging, planning, and treatment delivery in a single step at the treatment unit. The technical challenges of this approach include cone-beam CT (CBCT) image quality for target definition, online planning, and efficient process integration. METHODS AND MATERIALS: An integrated imaging, planning, and delivery system was constructed and tested with phantoms. The magnitude of CBCT image artifacts following the use of an antiscatter grid and a nonlinear scatter correction was quantified using phantom data and images of patients receiving conventional palliative RT of the spine. The efficacy of online planning was then assessed using corrected CBCT images. Testing of the complete process was performed on phantoms with assessment of timing and dosimetric accuracy. RESULTS: The use of image corrections reduced the cupping artifact from 30% to 4.5% on CBCT images of a body phantom and improved the accuracy of CBCT numbers (water: +/- 20 Hounsfield unit [HU], and lung and bone: to within +/- 130 HU). Bony anatomy was clearly visible and was deemed sufficient for target definition. The mean total time (n = 5) for application of the online approach was 23.1 min. Image-guided dose placement was assessed using radiochromic film measurements with good agreement (within 5% of dose difference and 2 mm of distance to agreement). CONCLUSIONS: The technical feasibility of CBCT-guided online planning and delivery for palliative single treatment has been demonstrated. The process was performed in one session equivalent to an initial treatment slot (<30 min) with dosimetric accuracy satisfying accepted RT standards.     

鼻咽癌适形调强放射治疗中计划靶体积不确定度的研究

背景与目的:鼻咽癌的适形调强放疗为减少正常组织的放射损伤,提高患者的生存质量提供了契机.但是,高度适形的治疗技术使肿瘤和正常组织之间的剂量梯度变得非常陡峭,每日的摆位不确定度对理想化的治疗计划产生的影响也会因此而加大.本研究探讨使用热塑面罩固定时,该治疗过程的摆位不确定度,以及为补偿这种不确定度需要在临床靶体积周围所加的安全边界的大小.方法:选取首次做适形调强放疗的早期鼻咽癌患者19例.每周进行一次CT重复扫描,方法与做治疗计划时完全相同.共获取85次扫描参数.通过读图软件对每周扫描的CT图像与计划设计的CT图像进行比较,求出每次摆位与首次定位时感兴趣的解剖标记点在三维方向上的差异.结果:19例患者的85次扫描参数比较,不同解剖骨性标记点在X、Y、Z方向的绝对位移值分别为(0.89±0.69)mm、(0.82±0.79)mm、(0.95±1.24)mm、矢量位移的系统误差分别为0.94 mm、1.00mm、1.32mm,随机误差分别为0.87 mm、0.80 mm、1.04 mm.等中心点的三维矢量位移的平均值为1.87 mm,95%可信区间为2.03～7.24 mm,平均值3.82 mm.结论:对早期鼻咽癌患者的适形调强放疗,其X、Y、Z轴向上由临床靶体积统一外扩3.00 mm形成临床靶体积-计划靶体积安全边界来弥补由于体位固定的不确定度对靶区剂量分布造成的影响应该是足够的.     

Lung tumor reproducibility with active breath control (ABC) in image-guided radiotherapy based on cone-beam computed tomography with two registration methods

Purpose

To study the inter- and intrafraction tumor reproducibility with active breath control (ABC) utilizing cone-beam computed tomography (CBCT), and compare validity of registration with two different regions of interest (ROI).

Methods and materials

Thirty-one lung tumors in 19 patients received conventional or stereotactic body radiotherapy with ABC. During each treatment, patients had three CBCT scanned before and after online position correction and after treatment. These CBCT images were aligned to the planning CT using the gray scale registration of tumor and bony registration of the thorax, and tumor position uncertainties were then determined.

Results

The interfraction systematic and random translation errors in the left-right (LR), superior-inferior (SI) and anterior-posterior (AP) directions were 3.6, 4.8, and 2.9 mm; 2.5, 4.5, and 3.5 mm, respectively, with gray scale alignment; 1.9, 4.3, 2.0 mm and 2.5, 4.4, 2.9 mm, respectively, with bony alignment. The interfraction systematic and random rotation errors with gray scale and bony alignment groups ranged from 1.4° to 3.0° and 0.8° to 2.3°, respectively. The intrafraction systematic and random errors with gray scale registration in LR, SI, AP directions were 0.9, 2.0, 1.8 mm and 1.5, 1.7, 2.9 mm, respectively, for translation; 1.5°, 0.9°, 1.0° and 1.2°, 2.2°, 1.8°, respectively, for rotation. The translational errors in SI direction with bony alignment were significantly larger than that of gray scale (p < 0.05).

Conclusions

With CBCT guided online correction the interfraction positioning errors can be markedly reduced. The intrafraction errors were not diminished by the use of ABC. Rotation errors were not very remarkable both inter- and intrafraction. Gray scale alignment of tumor may provide a better registration in SI direction.