Implantation of 125Ⅰ seeds for recurrence cervical node of head and neck tumor after external beam radiotherapy

Objective To summarize the efficacy and the feasibility of 125I seed implantation for recurrence cervical lymph node of head and neck tumor after radiotherapy or radiotherapy plus neck dissection. Methods Thirty-six patients with the recurrence cervical lymphnode of head and neck tumor after radiotherapy (17 patients) or radiotherapy plus neck dissection (19 patients) were treated with 125I seed implantation guided by ultrasound or CT under local anesthesia. The median number of seeds was 27( range from 3 to 78 ). Postoperative quality evaluation were routinely obtained for all patients. The actuarial D90 ranged from 90-160 Gy (median, 130 Gy). Results The follow-up rate was 100%. The number of the patients who were followed up over 1-and 2-year were 11 and 3. The overall response rate was 81%. The 1-and 2-year over local control rates, over survival rates were 69% and 35%, 50% and 22%, respectively.The 1-and 2-year local control rates in patients with recurrence node after radiotherapy plus neck dissection were 72% and 54%, while those were 67% and 50% in patients with recurrence node after radiotherapy,respectively (χ2=00,P=0.965). The 1-and 2-year survival rates in two groups were 48%, 13% , and 51%, 39%, respectively (χ2=0.17, P=0.676). Conclusions 125I seed implantation is a safe,minimal invasive with low morbidity and high efficacy salvage treatment method for cervical lymph node recurrence of head and neck tumor after radiotherapy with or without neck dissection.     

鼻咽癌调强放疗对腮腺功能的影响

Objective To evaluate the effect of intensity-modulated radiation therapy(IMRT) on parotid function in nasopharyngeal carcinoma(NPC). Methods Eighty-three NPC patients received prima-ry IMRT between 2001 and 2003. Xerostomia before radiotherapy, at the end of radiotherapy, at 6-month, 1-,2-,3-,4- and 5-year after radiotherapy were investigated, respectively. The relation between xerostomia and parotid dose distribution was analyzed. Results Of all the patients,4,31,31 and 17 had stage Ⅰ,Ⅱ,Ⅲ and ⅣA disease, respectively. Sixteen patients received chemo-radiotherapy. The median followed-up time was 65 months. The 5-year local control and regional control rate were 96% and 95% ,respectively. The 5-year overall survival rate was 80%. The mild xerostomia rate at the seven time points was 42%, 51%, 71%, 77%, 58%, 38% and 26%. The corresponding moderate xerostomia rate was 52%, 53%, 21%,8%, 3%, 2% and 2%, respectively. No serious xerostomia was observed. The mean dose of the bilateral parotid glands was 34.34 Gy. Xerostomia at 6-month after radiotherapy was positively correlated with the mean dose of the parotid glands, and D50 was the independent factor in predicting the xerostomia. Parotid function was well protected when the mean dose and D50 were no more than 33 Gy and 29 Gy,respectively. Conclusions IMRT can improve the local-regional control of NPC and protect the parotid glands from radiation-induced in-jury.     

鼻咽癌调强放疗对腮腺功能的影响

Objective To evaluate the effect of intensity-modulated radiation therapy(IMRT) on parotid function in nasopharyngeal carcinoma(NPC). Methods Eighty-three NPC patients received prima-ry IMRT between 2001 and 2003. Xerostomia before radiotherapy, at the end of radiotherapy, at 6-month, 1-,2-,3-,4- and 5-year after radiotherapy were investigated, respectively. The relation between xerostomia and parotid dose distribution was analyzed. Results Of all the patients,4,31,31 and 17 had stage Ⅰ,Ⅱ,Ⅲ and ⅣA disease, respectively. Sixteen patients received chemo-radiotherapy. The median followed-up time was 65 months. The 5-year local control and regional control rate were 96% and 95% ,respectively. The 5-year overall survival rate was 80%. The mild xerostomia rate at the seven time points was 42%, 51%, 71%, 77%, 58%, 38% and 26%. The corresponding moderate xerostomia rate was 52%, 53%, 21%,8%, 3%, 2% and 2%, respectively. No serious xerostomia was observed. The mean dose of the bilateral parotid glands was 34.34 Gy. Xerostomia at 6-month after radiotherapy was positively correlated with the mean dose of the parotid glands, and D50 was the independent factor in predicting the xerostomia. Parotid function was well protected when the mean dose and D50 were no more than 33 Gy and 29 Gy,respectively. Conclusions IMRT can improve the local-regional control of NPC and protect the parotid glands from radiation-induced in-jury.     

鼻咽癌调强放疗对腮腺功能的影响

Objective To evaluate the effect of intensity-modulated radiation therapy(IMRT) on parotid function in nasopharyngeal carcinoma(NPC). Methods Eighty-three NPC patients received prima-ry IMRT between 2001 and 2003. Xerostomia before radiotherapy, at the end of radiotherapy, at 6-month, 1-,2-,3-,4- and 5-year after radiotherapy were investigated, respectively. The relation between xerostomia and parotid dose distribution was analyzed. Results Of all the patients,4,31,31 and 17 had stage Ⅰ,Ⅱ,Ⅲ and ⅣA disease, respectively. Sixteen patients received chemo-radiotherapy. The median followed-up time was 65 months. The 5-year local control and regional control rate were 96% and 95% ,respectively. The 5-year overall survival rate was 80%. The mild xerostomia rate at the seven time points was 42%, 51%, 71%, 77%, 58%, 38% and 26%. The corresponding moderate xerostomia rate was 52%, 53%, 21%,8%, 3%, 2% and 2%, respectively. No serious xerostomia was observed. The mean dose of the bilateral parotid glands was 34.34 Gy. Xerostomia at 6-month after radiotherapy was positively correlated with the mean dose of the parotid glands, and D50 was the independent factor in predicting the xerostomia. Parotid function was well protected when the mean dose and D50 were no more than 33 Gy and 29 Gy,respectively. Conclusions IMRT can improve the local-regional control of NPC and protect the parotid glands from radiation-induced in-jury.     

鼻咽癌调强放疗对腮腺功能的影响

Objective To evaluate the effect of intensity-modulated radiation therapy(IMRT) on parotid function in nasopharyngeal carcinoma(NPC). Methods Eighty-three NPC patients received prima-ry IMRT between 2001 and 2003. Xerostomia before radiotherapy, at the end of radiotherapy, at 6-month, 1-,2-,3-,4- and 5-year after radiotherapy were investigated, respectively. The relation between xerostomia and parotid dose distribution was analyzed. Results Of all the patients,4,31,31 and 17 had stage Ⅰ,Ⅱ,Ⅲ and ⅣA disease, respectively. Sixteen patients received chemo-radiotherapy. The median followed-up time was 65 months. The 5-year local control and regional control rate were 96% and 95% ,respectively. The 5-year overall survival rate was 80%. The mild xerostomia rate at the seven time points was 42%, 51%, 71%, 77%, 58%, 38% and 26%. The corresponding moderate xerostomia rate was 52%, 53%, 21%,8%, 3%, 2% and 2%, respectively. No serious xerostomia was observed. The mean dose of the bilateral parotid glands was 34.34 Gy. Xerostomia at 6-month after radiotherapy was positively correlated with the mean dose of the parotid glands, and D50 was the independent factor in predicting the xerostomia. Parotid function was well protected when the mean dose and D50 were no more than 33 Gy and 29 Gy,respectively. Conclusions IMRT can improve the local-regional control of NPC and protect the parotid glands from radiation-induced in-jury.     

鼻咽癌调强放疗对腮腺功能的影响

Objective To evaluate the effect of intensity-modulated radiation therapy(IMRT) on parotid function in nasopharyngeal carcinoma(NPC). Methods Eighty-three NPC patients received prima-ry IMRT between 2001 and 2003. Xerostomia before radiotherapy, at the end of radiotherapy, at 6-month, 1-,2-,3-,4- and 5-year after radiotherapy were investigated, respectively. The relation between xerostomia and parotid dose distribution was analyzed. Results Of all the patients,4,31,31 and 17 had stage Ⅰ,Ⅱ,Ⅲ and ⅣA disease, respectively. Sixteen patients received chemo-radiotherapy. The median followed-up time was 65 months. The 5-year local control and regional control rate were 96% and 95% ,respectively. The 5-year overall survival rate was 80%. The mild xerostomia rate at the seven time points was 42%, 51%, 71%, 77%, 58%, 38% and 26%. The corresponding moderate xerostomia rate was 52%, 53%, 21%,8%, 3%, 2% and 2%, respectively. No serious xerostomia was observed. The mean dose of the bilateral parotid glands was 34.34 Gy. Xerostomia at 6-month after radiotherapy was positively correlated with the mean dose of the parotid glands, and D50 was the independent factor in predicting the xerostomia. Parotid function was well protected when the mean dose and D50 were no more than 33 Gy and 29 Gy,respectively. Conclusions IMRT can improve the local-regional control of NPC and protect the parotid glands from radiation-induced in-jury.     

鼻咽癌调强放疗对腮腺功能的影响

Objective To evaluate the effect of intensity-modulated radiation therapy(IMRT) on parotid function in nasopharyngeal carcinoma(NPC). Methods Eighty-three NPC patients received prima-ry IMRT between 2001 and 2003. Xerostomia before radiotherapy, at the end of radiotherapy, at 6-month, 1-,2-,3-,4- and 5-year after radiotherapy were investigated, respectively. The relation between xerostomia and parotid dose distribution was analyzed. Results Of all the patients,4,31,31 and 17 had stage Ⅰ,Ⅱ,Ⅲ and ⅣA disease, respectively. Sixteen patients received chemo-radiotherapy. The median followed-up time was 65 months. The 5-year local control and regional control rate were 96% and 95% ,respectively. The 5-year overall survival rate was 80%. The mild xerostomia rate at the seven time points was 42%, 51%, 71%, 77%, 58%, 38% and 26%. The corresponding moderate xerostomia rate was 52%, 53%, 21%,8%, 3%, 2% and 2%, respectively. No serious xerostomia was observed. The mean dose of the bilateral parotid glands was 34.34 Gy. Xerostomia at 6-month after radiotherapy was positively correlated with the mean dose of the parotid glands, and D50 was the independent factor in predicting the xerostomia. Parotid function was well protected when the mean dose and D50 were no more than 33 Gy and 29 Gy,respectively. Conclusions IMRT can improve the local-regional control of NPC and protect the parotid glands from radiation-induced in-jury.     

鼻咽癌调强放疗对腮腺功能的影响

Objective To evaluate the effect of intensity-modulated radiation therapy(IMRT) on parotid function in nasopharyngeal carcinoma(NPC). Methods Eighty-three NPC patients received prima-ry IMRT between 2001 and 2003. Xerostomia before radiotherapy, at the end of radiotherapy, at 6-month, 1-,2-,3-,4- and 5-year after radiotherapy were investigated, respectively. The relation between xerostomia and parotid dose distribution was analyzed. Results Of all the patients,4,31,31 and 17 had stage Ⅰ,Ⅱ,Ⅲ and ⅣA disease, respectively. Sixteen patients received chemo-radiotherapy. The median followed-up time was 65 months. The 5-year local control and regional control rate were 96% and 95% ,respectively. The 5-year overall survival rate was 80%. The mild xerostomia rate at the seven time points was 42%, 51%, 71%, 77%, 58%, 38% and 26%. The corresponding moderate xerostomia rate was 52%, 53%, 21%,8%, 3%, 2% and 2%, respectively. No serious xerostomia was observed. The mean dose of the bilateral parotid glands was 34.34 Gy. Xerostomia at 6-month after radiotherapy was positively correlated with the mean dose of the parotid glands, and D50 was the independent factor in predicting the xerostomia. Parotid function was well protected when the mean dose and D50 were no more than 33 Gy and 29 Gy,respectively. Conclusions IMRT can improve the local-regional control of NPC and protect the parotid glands from radiation-induced in-jury.     

鼻咽癌调强放疗对腮腺功能的影响

Objective To evaluate the effect of intensity-modulated radiation therapy(IMRT) on parotid function in nasopharyngeal carcinoma(NPC). Methods Eighty-three NPC patients received prima-ry IMRT between 2001 and 2003. Xerostomia before radiotherapy, at the end of radiotherapy, at 6-month, 1-,2-,3-,4- and 5-year after radiotherapy were investigated, respectively. The relation between xerostomia and parotid dose distribution was analyzed. Results Of all the patients,4,31,31 and 17 had stage Ⅰ,Ⅱ,Ⅲ and ⅣA disease, respectively. Sixteen patients received chemo-radiotherapy. The median followed-up time was 65 months. The 5-year local control and regional control rate were 96% and 95% ,respectively. The 5-year overall survival rate was 80%. The mild xerostomia rate at the seven time points was 42%, 51%, 71%, 77%, 58%, 38% and 26%. The corresponding moderate xerostomia rate was 52%, 53%, 21%,8%, 3%, 2% and 2%, respectively. No serious xerostomia was observed. The mean dose of the bilateral parotid glands was 34.34 Gy. Xerostomia at 6-month after radiotherapy was positively correlated with the mean dose of the parotid glands, and D50 was the independent factor in predicting the xerostomia. Parotid function was well protected when the mean dose and D50 were no more than 33 Gy and 29 Gy,respectively. Conclusions IMRT can improve the local-regional control of NPC and protect the parotid glands from radiation-induced in-jury.     

图像引导鼻咽癌调强放疗位置误差导致剂量差异分析

目的 分析千伏特锥形束CT(CBCT)对鼻咽癌调强放疗靶区中心位置变化及由位置偏差导致的剂量变化.方法 对21例鼻咽癌患者调强放疗,全程376次CBCT得到每次靶区中心变化值.在上述变化值中随机抽取10、15次值输入逆向调强放疗计划系统中,照射角度、子野序列、权重等均不变,只对中心发生变化;累积10、15次偏差计划得到新的剂量分布,通过偏差公式得到相对应次数标准计划剂量偏差情况.结果 未经校正的376次CBCT在左右、上下、前后方向的系统误差和随机误差分别为0.75 mm和1.13 mm,0.92 mm和2.15 mm,0.82 mm和1.24 mm,利用双参数模型计算CTV外扩4、6,4 mm生成PTV,左右、上下、前后方向＜2 mm的偏差比例分别为82.8%、76.0%、81.8%,＞3 mm偏差分别为6.2%、9.8%、7.1%.在15次累积计划时靶区接受95%处方剂量(D95)偏差为-7.5%～-11.9%,D50的为-5.1%～-8.2%.结论 每次较小的摆位误差可能对靶区或正常器官的剂量影响较小,但整个疗程累计30余次的误差结果可能导致较大剂量差异,通过双参数模型计算生成PTV并按PTV实现的计划和图像引导放疗可弥补这些剂量的不足.

Abstract：

Objective To discuss the set-up isocenter error based on kilovolt cone beam computed tomography (KVCBCT) and to investigate dose deviation led to set-up isocenter error. Methods 21 cases of nasopharyngeal carcinoma ( NPC ) treated with image guided intensity modulated radiotherapy (IG-IMRT)were investigated. The online KVCBCT scan, rigid image registration, set-up error was gained for 376 sets before radiotherapy. We sampled ten and fifteen setup isocenter error in the 376 sets randomly. Without changing beam angle,fields size and leaf sequences and dose weight et al. , we only replaced new isocenter and accumulated the new plan for ten or fifteen plans. We compared the percentage deviation between ten,fifteen times accumulated plans and normal ten , fifteen times plans. Results All 376 sets of KVCBCT image were analyzed for 21 cases. Under the condition of non-correction, the setup isocenter errors are 0. 75mm ± 1.13 mm, 0. 92 mm ±2. 15 mm,0. 82 mm ± 1.24 mm in left-right, superior-inferior and anteriorposterior directions respectively. So, we developed the margins which were 4 mm,6 mm、4 mm in three directions respectively from clinical tumor volume to planning tumor volume (PTV) calculated by two parameters model. In the fifteen accumulated plan, the deviation in the dose of 95% PTV (D95) was -7. 5% - - 11.9%, and the deviation in the D50 was -5. 1% - -8. 2%. Conclusions It is possible of small effects to normal organs and targets because of small error of patient displacement in one fraction.However, many small errors can led to considerable dose difference in targets and normal tissue in thirty fractions of all treatments period. So, according to two parameters model, PTV margin can be designed new planning and depended on IG-IMRT technique, which it will be significantly reduced these dose differences.     

OBI图像引导在鼻咽癌IMRT中的应用

目的 探索IGRT在保障鼻咽癌IMRT精确性中的应用。方法 应用直线加速器OBI系统对10例鼻咽癌患者实施IMRT,观察并记录每次摆位后、体位调整后、治疗后的IGRT,分析其影像与CT模拟定位影像之间的摆位差异。结果 摆位后左右、头脚、前后方向误差分别为(0.22±1.00)、(-0.37±1.28)、(0.04±1.36) mm;体位调整后对应为(0.29±0.76)、(-0.04±0.78)、(-0.01±0.92) mm;治疗后对应为(0.20±0.78)、(0.16±0.80)、(0.05±0.92) mm。摆位后左右、头脚、前后方向误差≤1 mm概率分别为81.0%、77.6%、88.2%;体位调整后对应为92.5%、96.4%、96.4%;治疗后对应为91.7%、94.9%、96.8%。结论 鼻咽癌患者实施分次IMRT过程中进行OBI系统下的精准IGRT技术非常重要,必要时需参照摆位后的IGRT影像调整患者的放疗体位,修正摆位误差,有效提高分次IMRT的精确性。     

不同体位固定方式对乳腺癌放疗摆位精度的影响

目的:探讨使用4种不同体位固定方式用于乳腺癌放疗定位,并对4种不同的固定方式的摆位精度分析和比较,为临床应用提供参考。方法:选取2018年11月至2019年1月我院收治的乳腺癌放疗患者34例,其中乳腺癌保乳术后患者20例,乳腺癌根治术后（锁骨上下区放疗）患者14例。将乳腺癌保乳术后患者20例分为A、B两组,分别采用负压垫加头膜固定和乳腺托架固定;将乳腺癌根治术后患者14例分为C、D两组,采用颈肩膜固定（C组双手置于体侧）(D组患侧手抓耳)。用Philips Bigbore大孔径CT模拟机进行定位扫描,图像传输到Varian Ecplipse治疗计划系统进行重建,计划设计。对所有参与研究的患者首次治疗完成后,进行CT下复位验证,并将验证图像与计划图像配准,测量治疗中心坐标误差,用SPSS 18.0统计软件对数据进行统计分析,给出摆位误差。结果:A组在X、Y、Z方向上的摆位误差分别为（1.7±1.9） mm、（2.1±2.9） mm、（2.0±1.2） mm;B组在X、Y、Z方向上的摆位误差分别为（2.8±1.1） mm、（3.7±1.1） mm、（4.8±1.3） mm;C组在X、Y、Z方向上的摆位误差分别为（2.1±1.6） mm、（2.1±1.5） mm、（3.6±3.1） mm;D组在X、Y、Z方向上的摆位误差分别为（1.0±0.5） mm、（1.9±1.5） mm、（3.6±1.9） mm。A组在Y、Z方向的摆位误差小于B组（P=0.048、0.038）,A、B两组在X方向的摆位误差比较,差异无统计学意义（P>0.05）;C、D两组在X、Y、Z方向的摆位误差比较,差异无统计学意义（P>0.05）。结论:乳腺癌保乳术后患者的放疗,全乳加锁骨上的一体化的调强技术,用负压垫加头膜固定技术比用乳腺托架固定技术减少了摆位误差;乳腺癌根治术后患者放疗,用颈肩膜固定技术的两种体位对摆位误差无太大差异,为了减少相邻野衔接问题引起的剂量误差建议采用手抓耳体位。     

C T模拟机及模拟定位机在头颈部肿瘤I MRT位置验证中的应用

目的：探讨GE LightSpeed RT型CT模拟机及Nucletron SIMULIX HQ型模拟定位机在头颈部肿瘤IMRT靶区治疗中心位置校正方法及各自优势。方法：抽取60例采取头颈肩热塑网膜固定的头颈部肿瘤IM-RT患者随机分成两组,利用DRR正侧位图像在模拟定位机下校正位置30例,利用中心层面的横断面图像在CT模拟机下复位30例。分别测量在X（左右）、Y（头脚）、Z（前后）三个方向上校位中心与治疗中心的位置差别,记录三个方向上的误差为Ex、Ey、Ez。结果：误差整理分为三个等级范围Ea≤±1mm,±1mm＜Eb≤±2mm,Ec ＞±2mm。CT模拟机校正中心时X方向上各误差等级范围例数依次为8（26．7％）、18（60．0％）、4（13．3％）;Y方向上为19（63．3％）、8（26．7％）、3（10．0％）;Z方向上为9（30．0％）、14（46．7％）、7（23．3％）。模拟定位机校正中心时X方向为6（20．0％）、19（63．3％）、5（16．7％）;Y方向上为9（30．0％）、18（60．0％）、3（10．0％）;Z方向上为8（26．7％）、14（46．7％）、8（26．7％）。三个方向上CT模拟机校正中心的平均误差分别为1．39mm、0．53mm、1．48mm;模拟定位机分别为1．51mm、1．43mm、1．66mm。60例患者首次治疗时按照校正后的中心进行摆位,经加速器治疗前IGRT验证其三维方向上的误差均控制在±2mm以内。结论：对于采取头颈肩热塑网膜固定的头颈部肿瘤IMRT患者,无论是采取CT模拟机复位还是模拟定位机复位,其三维方向上整体最高只有40％的患者位移精度在1 mm以内,所以为确保患者的治疗,IMRT计划出来后进行位置验证和修正是非常有必要的;三维方向上,CT模拟机和模拟定位机的复位平均精度都控制在2mm以内,所以两种设备都可以适用于IMRT计划的位置验证,有利于提高模拟机的使用率和工作效率;CT定位机复位方法在三维方向上平均精度高于模拟定位机的平均精度,主要是在Y方向上的差异明显。     

热塑面罩收缩对放疗靶区定位精度的影响

目的 分析头颈部肿瘤放疗患者热塑面罩收缩对靶区定位精度的影响。方法 试验一,测量热塑膜自由状态下收缩幅度:将规格为100 mm×50 mm的热塑膜片加热并按一定比率在一维方向上拉伸,然后在拉伸后不同时刻测量热塑膜长度变化,分析不同拉伸比率与收缩幅度的关系。试验二,模体试验:利用头颈部仿形模体,模拟患者从制作面罩到放疗整个过程,测量治疗过程中由于面罩收缩引起的治疗中心位置偏移程度。结果 热塑膜在前20 min内收缩幅度最大,不同拉伸比率对收缩幅度无明显影响。在治疗过程中由于面罩收缩引起的中心点偏移量在左右、上下、前后方向分别为(－0.12±0.31)、(－0.24±0.21)、(0.61±0.42) mm,在模拟一个疗程6周时间内各点内偏移相近(P=0.185~0.961)。结论 为患者制作面罩时冷却时间应≥20 min,在此前提下面罩收缩引起的摆位误差在可接受水平。     

鼻咽癌调强放疗摆位误差对剂量分布影响的研究

目的探讨鼻咽癌（NPC）调强放射治疗（IMRT）中摆位误差对靶区和危及器官物理剂量的影响。方法对6例鼻咽癌患者,应用瓦里安Trilogy直线加速器的机载影像系统（On-Borad-Imager）,实时采集CBCT图像,治疗前行CT扫描取得实际图像,将CBCT图像与计划系统的模拟定位CT图像靶中心匹配。采用瓦里安专用的分析软件计算x（左右）、y（头脚）、z（腹背）方向偏移误差,并通过Eclipse 8.6 Version治疗计划系统研究误差在鼻咽癌放疗中对剂量分布的影响。结果系统误差（均差mean）±随机误差（标准差stdev）在x、y、z方向分别为（-0.52±1.2）mm、（-0.22±2.54）mm、（-0.53±1.21）mm,颈部转移淋巴结（GTVnd）总剂量分布变化为0.32%～12.34%,鼻咽原发肿瘤（GTVnx）剂量变化为-0.25%～0.32%,左晶体剂量变化为-12.45%～0.13%,右晶体剂量变化为-17.87%～-0.08%,脊髓剂量变化为-0.18%～8.20%,脑干剂量变化为-5.40%～6.55%。结论鼻咽癌IMRT摆位误差是难以避免的,应用OBI-CBCT系统,进行实时摆位误差校正,尽可能减少系统误差和随机误差,提高摆位精度,使靶区及周围正常组织器官剂量分布准确,为临床放疗提供质量保证。     

应用CBCT、EPID研究鼻咽癌2种体位固定方式摆位误差的比较分析

背景与目的：随着放疗技术和设备的不断发展,鼻咽癌放射治疗已经进入了精确放疗时代,摆位误差成为影响放疗效果的非常重要的因素。本研究在千伏级锥形束CT(cone beam computed tomography,CBCT)与兆伏级电子射野影像系统(electronic portal imaging device,EPID)2种影像模式引导下治疗鼻咽癌,在头枕+头颈肩面膜、真空气垫+头颈肩面膜固定2种方式下的摆位误差分析比较。方法：随机选取40例鼻咽癌患者分成2组(头枕+头颈肩面膜组,真空气垫+头颈肩面膜固定组),每组组内再分成CBCT扫描组和EPID验证组。将CBCT扫描图像与计划CT图像进行自动骨性配准、将EPID拍摄的正侧位片采用突出性骨性标志进行手动配准,分别得出x、y、z共3个线性方向上的摆位误差值,对获得的2组数据进行组内组间两两比较,采用t检验比较数据差异有无统计学意义。结果：头枕+头颈肩面膜组摆位后行CBCT扫描,在x、y、z方向上进行配准所得的平均误差分别为：x方向(0.67±2.01)mm、y方向(0.51±1.71)mm、z方向(0.57±2.04)mm;拍摄EPID验证片配准所得误差均值：x方向(0.69±2.19)mm、y方向(0.54±2.03)mm、z方向(0.61±2.11)mm。真空气垫+头颈肩面膜固定组摆位后行CBCT扫描,在x、y、z方向上进行配准所得的平均误差分别为：x方向(0.42±1.81)mm、y方向(0.33±1.55)mm、z方向(0.50±1.75)mm;拍摄EPID验证片配准误差均值：x方向(0.44±1.87)mm、y方向(0.43±1.70)mm、z方向(0.54±1.77)mm。采用头枕+头颈肩面膜组、真空气垫+头颈肩面膜固定组的误差数据差异均有统计学意义(P<0.05)。结论：2种不同的影像模式(CBCT与EPID)进行摆位误差的比对未见明显统计学差异,2种固定方式下头颈部真空气垫+头颈肩面膜固定的患者体位重复性更好。     

个体化口含牙胶辅助定位减少鼻咽癌放疗摆位误差

目的 评估个体化口含牙胶辅助的定位方法保证鼻咽癌放疗摆位的精确性。方法鼻咽癌放疗定位和摆位时,使用头颈肩热塑面罩固定体位,注意体表轮廓处的体膜成型,增加个体化口含牙胶辅助定位。放疗最初3次以及之后每周1次用OBI系统验证摆位误差。结果 全部病例的摆位误差在左右、上下、前后方向的平均值和标准偏差分别为－0.26、0.36、0.35 mm和0.97、1.16、1.11 mm,3个方向上摆位误差≤2 mm的概率分别为99.7%、98.0%、100%。结论 采用个体化口含牙胶辅助的定位方法可以保证鼻咽癌放疗摆位的精确性。     

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.     

ExacTrac图像引导系统在鼻咽癌IMRT中的应用

目的探讨ExacTrac图像引导系统在鼻咽癌调强放射治疗(IMRT)摆位误差全程管控中的应用价值。方法收集2018年3月至2018年8月接受IMRT的30例鼻咽癌患者,采用ExacTrac图像引导系统全程实施图像引导放射治疗(IGRT),分析左右、头脚、腹背3个平移方向及绕此3个方向旋转角度上的6D误差。结果ExacTrac图像引导系统校正前左右、头脚、腹背3个平移方向的误差值分别为(0.11±1.52)mm、(1.45±2.40)mm和(0.67±1.65)mm,绕此3个方向的旋转误差值分别为(-0.16±1.12)°、(0.32±1.59)°、(-0.38±1.12)°。校正后,左右、头脚、腹背3个平移方向的误差值分别为(-0.04±0.46)mm、(0±0.42)mm和(0.03±0.54)mm,绕此3个方向的旋转误差值分别为(-0.03±0.25)°、(0.01±0.23)°和(0.01±0.28)°。校正后在左右、头脚、腹背3个平移方向及绕此3个方向的旋转角度上,≤1 mm或1°的误差概率分别为99%、100%、99%、100%、100%和100%。2 mm或2°的误差概率在左右平移方向为1%,腹背平移方向为1%,其余方向为0。≥3 mm或3°的误差概率均为0。ExacTrac图像引导系统校正前后6D方向摆位误差的差异有统计学意义(P<0.05)。结论鼻咽癌患者在实施每分次IMRT的过程中行IGRT非常必要,应用ExacTrac图像引导系统可以明显校正摆位误差,提高放疗精准性。     

摆位稳健性对IMRT与VMAT剂量学影响研究

目的 比较摆位稳健性对头颈部肿瘤IMRT与VMAT剂量分布的影响程度,评价两者对图像引导需求。方法 纳入30例IMRT鼻咽癌患者按临床上剂量要求设计VMAT计划,AAA法计算剂量。每患者两计划分别沿原始x、y、z轴各移动等中心±1.0、±3.0、±5.0 mm模拟左右、上下、前后方向摆位误差对剂量分布影响,分析60个参考计划与1080个再计划DVH参数。配对t检验差异。结果 误差为1 mm时,GTV D₉₈、CTV D₉₅、HI、PGTV V₉₅平均偏差<0.5%;误差为3 mm时,GTV与CTV剂量平均变化<1.0%,且VMAT高于IMRT (GTV D₉₈,P=0.00;CTV D₉₅,P=0.00),PGTV剂量偏差要大,IMRT与VAMT中PGTV_nx与PGTV_nd V₉₅平均偏差分别为[1.64% 比1.95%(P=0.01)]、[1.73% 比2.63%(P=0.00)]。误差增大各指标偏差变大,且VMAT高于IMRT (GTV D₉₈,P=0.00;CTV D₉₅,P=0.00;CTV HI,P=0.00;PGTV V₉₅,P=0.01)。相比靶区,脊髓、脑干D_max变化更大,但IMRT与VMAT间差异不明显。结论 误差较小时(<3 mm),IMRT与VMAT计划均较稳健。VMAT对摆位误差更敏感,主要体现在靶区剂量,随摆位误差增加两者间差异变大。建议行VMAT患者增加图像引导频次。