鼻咽癌放疗中常见的四种头部固定技术

目的 探讨鼻咽癌放疗的头部固定技术应用及推广。材料与方法：５０例鼻咽癌随机采用四种不同的头部固定技术，在钴６０治疗机上做放射治疗，观察测量２０天次。结果 （１）塑料面罩固定技术；重复性好，体位不易变，操作简单方便，轻巧，但随患者消瘦会影响面罩和头部的吻合程度，常用于常规等中心治疗。（２）带尼龙带扣的泡沫塑料枕固定技术；重复性好，体位不易变，操作简单方便，轻巧，适用于常规等中心治疗和面颈联合野、低熔     

鼻咽癌放疗3种体位固定方式的摆位误差研究

鼻咽癌放疗主要采用调强放疗或容积旋转调强放疗技术进行治疗. 调强放疗技术对临床摆位的精度和重复性要求苛刻,摆位精度直接影响照射剂量和放疗效果. 早期鼻咽癌放疗常采用头颈肩大面罩进行体位固定,然而临床运用发现部分患者摆位误差仍然较大,因此有必要对此种固定方式进行改良. 本文利用CBCT研究鼻咽癌放疗常规头枕结合头颈肩大面罩、发泡剂泡沫垫结合头颈肩大面罩和泡沫塑形枕结合头颈肩大面罩3种体位固定方式的临床摆位误差,现将结果报告如下.     

鼻咽癌定位方法的改进

目的　探讨鼻咽癌模拟定位方法的改进及技术提高。方法　①等距离定位方法 ;②在模拟机下等中心定位方法 ;③在模拟机下等中心定位方法及使用低熔点铅技术即鼻咽癌鼻咽部准适形照射 (经典适形 )。结果　①等距离定位方法 :重复性差 ,准确性差 ,放疗反应重。②在模拟机下等中心定位方法 :设备要求严格 ,技术要求高。病人摆位方便 ,体位固定好 ,体位重复性好。③准适行照射定位方法 :要求严格 ,定位的准确性提高 ,摆位方便 ,体位固定好 ,重复性好。结论　在模拟机下等中心定位使用低熔点铅技术方法值得推广。     

面罩适形技术在头部肿瘤放疗中的应用

面罩适形技术用于头部肿瘤患者放疗是安全可行的,面罩固定组体表野中心偏移治疗机灯光野中心的距离较垫棉枕组明显减少,可明显提高头部肿瘤患者放疗时体位的稳定性和重复性,有效地保护了正常组织器官.     

鼻咽癌定位方法的改进

目的：探讨鼻咽癌模拟定位方法的改进及技术提高。方法：（1）等距离定位方法。（2）在模拟机下等中心定位方法；（3）在模拟机下等中心定位方法及使用低熔点铅技术即鼻咽癌鼻咽部准适形照射（经典适形）。结果：（1）等距离定位方法：重复性差，准确性差，放疗反应重。（2）在模拟机下等中心定位方法：设备要求严格，技术要求高。病人摆位方便，体位固定好，体位重复性好。（3）准适行照射定位方法：要求严格，定位的准确性提高，摆位方便，体位固定好，重复性好。结论；在模拟机下等中心定位使用低熔点铅技术方法值得推广。     

鼻咽癌放射治疗体位、设野及固定方法的研究

目的：探讨鼻咽癌的合理照射体位及设野的剂量分布特点,比较几种体位固定方法的摆位重复性和位移情况。方法：利用ＴＰＳ探讨常规和改进体位下设野的合理性和剂量分布特点;将１２０例鼻咽癌随机均分成砂袋组、面罩组、泡沫塑枕组和等距离照射（ＳＳＤ）组,利用模拟机模拟定位和治疗过程,并分别摄取头颅侧位片,测量各照片间中心点的移动距离。结果：改进体位和设野与常规设野比较靶区中心剂量差别不大,但明显提高了茎突后,后组     

三维适形放疗面罩固定的质量控制

三维适形放疗（ 3-dimensional conformal radiation therapy, 3-D CRT）作为一种精确的放疗技术对摆位重复性的要求甚高。热塑面罩固定法是头颈部肿瘤放射治疗常用的固定方法,它具有简单、经济、无创等优点。热塑面罩固定法摆位重复性受摆位者主观因素影响较大,能否通过面膜制作和摆位各环节的质量控制减少摆位重复性误差,并将其用于 3-D CRT是值得研究的问题。本文报告了作者将面罩固定用于 26例局部复发鼻咽癌 3-D CRT的摆位质量控制及重复性验证的方法和结果。 1 材料与方法 1.1 病例资料 局部复发鼻咽癌 26例,其中女性 9例,男性 17例,年龄 23～ 71岁,中位年龄 46岁。全组病人神志清楚,摆位合作。 1.2 设备 PIKER PQ CT定位机, ACQ SIM ＆ ACQ PLAN（ CT模拟与三维计划系统） FICSHER三维 TPS、立体定向体架、多叶光栅, VARIAN 600C/D直线加速器,热塑面罩固定装置。 1.3 面罩制作与摆位过程的质量控制 1.3.1 病人准备：剃光头,着低领薄衫,以便于在病人头颈部作标记,并消除长发给面罩制作带来的不便和因长发位置变化引起的摆位误差。 1.3.2 个体化泡沫枕的制作：根据患者平卧头颈过伸时顶、枕、颈部曲面制作个体化泡沫枕,使患者头颈部能最大程度地与泡沫枕接触,减少患者体位可变度。     

发泡剂泡沫枕加固定面罩应用于鼻咽癌适形调强治疗

[目的]介绍一种更加适合鼻咽癌适形调强治疗的体位固定器.[方法]用美国NOMOS公司的MIMiC执行适形调强治疗,观察用常规固定枕加面罩和用发泡剂制作的泡沫枕加面罩这两种体位固定技术,比较固定枕与患者颈项部之间的吻合程度,患者的舒适性和患者的体位移动情况.[结果]在用常规固定枕的体位固定技术中,38%患者的头部与固定枕之间有不吻合现象,有35%的患者感觉到体位的不舒适,有46%的患者体位有移动(范围从0.4～4.01mm),平均移动值为0.84mm;而用发泡剂制作的泡沫枕作体位固定时不存在这些情况.[结论]在鼻咽癌适形调强治疗的体位固定技术中,发泡剂泡沫枕加面罩的体位固定技术比常规的固定技术优越,更加适合适形调强治疗的体位固定的要求.     

鼻咽癌放射治疗摆位精度初探

目的 :了解鼻咽癌常规放疗摆位与面模固定等中心放疗摆位的精度。方法 :随机选择 80例采用普通头垫软枕摆位放疗的鼻咽癌耳前野放疗患者 ,与同期采用面模固定仿适形挡铅等中心摆位的鼻咽癌放疗患者 6 0例 ,分别对其放疗前和放疗后头颅体位移动变化进行测量、比较。结果 :头垫软枕摆位常规放疗者出现体位移动 ,患者不自主移动发生率为 15 % ,最大移动距离为± 7mm ,由于操作者目测位不准造成误差率为 30 % ,最大移动距离为±8mm ;面模固定仿适形挡船等中心摆位放疗者 ,体位移动发生率 <2 % ,移动距离 <2mm。结论 :鼻咽癌放疗计划实施中 ,面模固定摆位能获得较好的质量保证。     

鼻咽癌放射治疗摆位精度初探

目的：了解鼻咽癌常规放疗摆位与面模固定等中心放疗摆位的精度。方法：随机选择80例采用普通头垫软枕摆位放疗的鼻咽癌耳前野放疗患者，与同期采用面模固定仿适形挡铅等中心摆位的鼻咽癌放疗患者60例，分别对其放疗前和放疗后头颅体位移动变化进行测量、比较。结果：头垫软枕摆位常规放疗者出现体位移动，患者不自主移动发生率为15％，最大移动距离为±7mm，由于操作者目测位不准造成误差率为30％，最大移动距离为±8mm；面模固定仿适形挡船等中心摆位放疗者，体位移动发生率＜2％，移动距离＜2mm。结论：鼻咽癌放疗计划实施中，面模固定摆位能获得较好的质量保证。     

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。     

Breast radiotherapy in the lateral decubitus position: A technique to prevent lung and heart irradiation

PURPOSE: To present an original technique for breast radiotherapy, with the aim of limiting lung and heart irradiation, satisfying quality assurance criteria. METHODS AND MATERIAL: An original radiotherapy technique for breast irradiation has been developed at the Institute Curie in January 1996. It consists of isocentric breast irradiation in the lateral decubitus position (isocentric lateral decubitus [ILD]). This technique is indicated for voluminous or pendulous breasts needing breast irradiation only. Thin carbon fiber supports and special patient positioning devices have been developed especially for this technique. In vivo measurements were performed to check the dose distribution before the routine use of the technique. RESULTS: ILD has been successfully implemented in routine practice, and 500 patients have been already treated. Breast radiotherapy is performed using a dose of 50 Gy at ICRU point in 25 fractions. ILD shows good homogeneity of the dose in breast treatment volume, treatment fields are perpendicular to the skin ensuring its protection, and extremely low dose is delivered to the underlying lung and heart. CONCLUSION: In cases of voluminous breasts or patients with a history of lung and heart disease, our technique provides several advantages over the conventional technique with opposing tangential fields. This technique improves the dose homogeneity according to the ICRU recommendations.     

MUC5B levels in submandibular gland saliva of patients treated with radiotherapy for head-and-neck cancer: A pilot study

We developed a new method for immobilization of the fix lower extremities by using a thermoplastic mask, a carbon fiber base plate, a customized headrest, and an adjustable angle holder. The lower extremities of 11 patients with lower extremity tumors were immobilized by this method. CT simulation was performed for each patient. For all 11 patients, the device fit was suitable and comfortable and had good reproducibility, which was proven in daily radiotherapy.     

发泡胶枕在鼻咽癌调强放疗中的应用

目的:应用MVCT研究鼻咽癌放疗中个体化发泡胶枕与标准聚氨酯头枕两种不同固定方式的摆位精度。方法:选取鼻咽癌螺旋断层调强放疗患者共34例,分为试验组和对照组,分别采用个体化发泡胶枕和标准化聚氨酯头枕,结合头颈肩热塑网膜进行体位固定。两组患者每次放疗前行MVCT扫描并与定位CT在线匹配,对得出的两组摆位误差数据行独立样本t检验,并以线性误差3 mm和旋转误差2°为限定阈值,对两组摆位误差数据行χ2检验。结果:对照组在左右、上下、前后三个方向的摆位线性误差和绕这三个方向形成的旋转误差分别为（1.79±2.05）mm、（1.82±1.36）mm、（1.48±1.77）mm和（0.94±1.23）°、（1.15±1.08）°、（0.54±0.61）°;试验组在上述的摆位误差和旋转误差分别为（1.19±1.09）mm、（1.24±0.97）mm、（0.91±0.89）mm和（0.71±0.79）°、（0.99±0.79）°、（0.67±0.68）°,两组在上述方向比较P=0.00、0.00、0.00、0.00、0.01、0.00,两组超出误差限定阈值次数的比较,除绕前后方向的旋转误差无统计学意义（P>0.05）,其余各方向均有意义（P<0.05）。结论:采用个体化发泡胶枕对鼻咽癌患者进行体位固定,摆位精度优于标准化聚氨酯头枕。     

Patient position verification with oblique radiation beams.

PURPOSE: In this study we investigated whether the position of head and neck cancer patients during radiotherapy could be determined from portal images of oblique radiation beams. Currently applied additional anterior posterior (AP) and lateral verification beams could then be abandoned. METHOD: The patient position was determined from portal images of the oblique radiation beams and compared with that determined from AP and lateral verification beams. Seven hundred and fifty-one portal images of 18 different patients were analyzed. RESULTS: The set-up errors of patients that were treated with oblique gantry angles could be determined with the same accuracy from the oblique beams as from the AP and lateral verification beams in the ventrodorsal and craniocaudal direction. An additional AP beam was necessary to obtain the same accuracy in the lateral direction, because the used beam directions were relatively close to lateral. The position verification of patients treated with both oblique gantry angles and isocentric table rotations was more accurate if AP and lateral verification beams were used. CONCLUSIONS: For patients treated with an irradiation technique with oblique gantry angles (and no isocentric table rotations) position verification can be performed by using these oblique radiation beams.     

Setup reproducibility in radiation therapy for lung cancer: a comparison between T-bar and expanded foam immobilization devices

Purpose: Physiologic and non-physiologic tumor motion complicates the use of tight margins in three-dimensional (3D) conformal radiotherapy. Setup reproducibility is an important non-physiologic cause of tumor motion. The objective of this study is to evaluate and compare patient setup reproducibility using the reusable T-bar and the disposable expanded foam immobilization device (EFID) in radiation therapy for lung cancer.Methods and Materials: Two hundred forty-four portal films were taken from 16 prospectively accrued patients treated for lung cancer. Patients were treated with either a pair of anterior and posterior parallel opposing fields (POF), or a combination of POF and a three-field isocentric technique. Each patient was treated in a supine position using either the T-bar setup or EFID. Six patients were treated in both devices over their treatment courses. Field placement analysis was used to evaluate 3D setup reproducibility, by comparing positions of bony landmarks relative to the radiation field edges in digitized simulator and portal images. Anterior-posterior, lateral, and longitudinal displacements, as well as field rotations along coronal and sagittal planes were measured. Statistical analyses of variance were applied to the deviations among portal films of all patients and the subgroup treated with both immobilization methods.Results: For the T-bar immobilization device, standard deviations of the setup reproducibility were 5.1, 3.7, and 5.1 mm in the anterior-posterior, lateral, and longitudinal dimensions, respectively. Rotations in the coronal plane and the sagittal plane were 0.9° and 1.0°, respectively. For the EFID, corresponding standard deviations of set up reproducibility were 3.6 mm, 5.3 mm, 5.4 mm, 0.7° and 1.4°, respectively. There was no statistically significant difference (p = 0.22) in the 3D setup reproducibility between T-bar and EFID. Subgroup analysis for the patients who were treated with both immobilization devices did not reveal a difference either. There was no consistent systematic error from simulator to treatment unit identified for either immobilization device.Conclusion: Although the optimal immobilization technique and patient positioning for thoracic radiotherapy have yet to be determined, this study indicates that T-bar is comparable with EFID in its setup reproducibility. In view of the inherent advantages of T-bar, it has become a standard immobilization device at our institution. The observed range of displacements in field positioning with either immobilization device implies that one cm (two standard deviations [SD] of setup error) will be a more appropriate margin to allow for setup variability in radiation therapy for lung cancer.     

Multicentre dosimetric comparison of photon‐junctioning techniques in head and neck radiotherapy

Because many head and neck radiotherapy treatment techniques rely on a junction between X‐ray fields, it was the aim of the present study to investigate the use of different junctioning techniques and the affect on the dose across the junction. Techniques in use at nine radiotherapy centres in Australia were investigated using thermoluminescence dosimetry (TLD). The techniques could broadly be divided into two groups: (i) use of the light field to match the fields after moving the patient; and (ii) use of asymmetric collimation to create a single isocentre located in the junction. The mean dose at the junction and its reproducibility was studied in five consecutive treatments in each centre using 25 TLD chips placed throughout the junction in an anthropomorphic phantom. There was a tendency for the mono‐isocentric technique to deliver a lower, more accurate mean dose at the junction (Group I: 1.22 Gy (n = 8) vs Group II: 0.96 Gy (n = 5) for 1 Gy planned, some centres contributed to both technique) with greater reproducibility (Group I: 9.6%, Group II: 5.1% of the mean dose). We conclude that a mono‐isocentric treatment technique has the potential to deliver a more accurate and reproducible dose distribution at the field junction of photon beams in head and neck treatment.     

Whole breast radiotherapy in the isocentric lateral decubitus position: Role of the immobilization device and table on clinical results

PurposeTo evaluate clinical results and the “effect bolus” based on the table design of different linear accelerators in patients with breast cancer treated by previously published whole breast irradiation in the isocentric lateral decubitus position.Material and methodsWe studied 248 consecutive female patients with early stage breast cancer treated by conservative surgery followed by three-dimensional conformal whole breast irradiation in the isocentric lateral decubitus position between January 2013 and February 2014. Radiotherapy was performed on linear accelerators using a Varian. The energy used was 4 and 10 MV photons or 6 MV photons. All patients were evaluated weekly by the radiation oncologist, acute toxicity was assessed using the NCICTC v 3.0 scale. Late toxicity and cosmetic results were evaluated 18 months after the radiotherapy. Cosmetic results were defined as excellent, good, middle or bad.ResultsAmong the 248 women included, the median age was 67 years (range: 35–91 years). All received whole breast radiotherapy with boost in 144 patients (58%). One-hundred-twenty patients received normofractionated and 124 patients hypofractionated whole breast radiotherapy. Median follow-up was 18 months. Acute skin toxicity in the whole breast radiotherapy in the isocentric lateral decubitus position was acceptable: there was 47% of grade 1 radiodermatitis, 50% of grade 2 and 3% grade 3 and no grade 4 for normofractionated radiotherapy; 89% of grade 1 dermatitis and 11% of grade 2 for hypofractionated radiotherapy; 89.7% of grade 0–1 dermatitis and 10.3% of grade 2 for the “flash” scheme and did not differ between the three linear accelerators (P = 0.2, P = 0.9 and P = 0.2 respectively for the normofractionated radiotherapy, hypofractionated radiotherapy and the “flash”scheme). Late toxicity was acceptable with 84% of grade 0–1 fibrosis for normofractionated radiotherapy, 94% of patients for hypofractionated radiotherapy and 77% for “flash” scheme and did not differ between the three linear accelerators (P = 0.44, P = 1 and P = 0.22 resp.). Most of patients (81%) had an excellent or a good cosmetic outcome.ConclusionsWhole breast radiotherapy in the isocentric lateral decubitus position is well tolerated. Clinical results are comparable based on different immobilization device allowed by linear accelerators. Particularly, there was no influence of the couch on skin tolerance and cosmetic results.     

Surface laser scanning to routinely produce casts for patient immobilization during radiotherapy*

Immobilization casts are used to reduce patient movement during the radiotherapy of head and neck and brain malignancies. Polyethylene‐based casts are produced by first taking a Plaster of Paris ‘negative’ impression of the patient. A ‘positive’ mould is then made, which is used to vacuum form an immobilization cast. Taking the ‘negative’ cast can be messy, stressful for patients and labour intensive. Recently, lightweight hand‐held laser surface scanners have become available. These allow an accurate 3‐D representation of objects to be generated non‐invasively. This technology has now been applied to the production of casts for radiotherapy. Each patient’s face and head is digitized using the Polhemus FastSCAN (Polhemus, Colchester, VT, USA) scanner. The electronic data are transferred to a computer numerical controlled mill, where a positive impression is machined. The feasibility of the process was examined, the labour required and radiation therapists’ satisfaction with aspects of the produced masks assessed. The scanner‐based method of mask production was found to be simple, accurate and non‐invasive. There was a reduction in radiation therapist labour required. Masks produced with the scanner‐based method were reported to result in improved mask fitting, daily reproducibility, patient immobilization and patient comfort.